I need a torque and HP curve for 1997 C8.3 325hp RV. The best thing I can find on the internet is this link: Cummins C325-20 Diesel Engine for Vehicle---Diesel Engine, Diesel Engine Parts, (http://www.engine-trade.com/product/cummins-c325-20-diesel-engine-for-vehicle.htm)
(https://www.foreforums.com/imagecache.php?image=http%3A%2F%2Fwww.engine-trade.com%2Fuploadfiles%2FPerformance-Curve-and-Drawing-of-CUMMINS-C325-20-Diesel-Engine-for-Vehicle.jpg&hash=4d733e8735b22fe0c48e0bfa1f8c6e9f" rel="cached" data-hash="4d733e8735b22fe0c48e0bfa1f8c6e9f" data-warn="External image, click here to view original" data-url="http://www.engine-trade.com/uploadfiles/Performance-Curve-and-Drawing-of-CUMMINS-C325-20-Diesel-Engine-for-Vehicle.jpg)
I'm planning on changing my rear end gearing and want to see where I need to have my RPM be for a nice 65-70mph cruise on the flat.
Pierce, I wrote about this in that old thread: Rear vibration 65-70mph+ (http://www.foreforums.com/index.php?topic=21694.50)
My coach has 5.13
Krush,
For some reason, I was thinking you had an 1989 U280 with a four speed. With your 1998, you will have a 6 speed so should have an O.D. of .65. If you have the same diameter tires and switched to a 4.63, this would give you about the same final drive and revolutions per mile as we have with our 3.07 ratio in our U300. With a slightly smaller engine, the six speed will still give you a pretty good first gear start on most any hill or altitude. Between the 4.63 and the 4.33, I would think a primary west coast rig would be better with the 4.63 and a mid-west/east coast rig would be good with a 4.33. With your length, you have to knock off a couple of thousand pounds so the 4.33 might end up the best choice, especially with the six speed.
My ex-Greyhound 4107 had a much lower rear end ratio than our U300 and about 125 HP less with the non-turbo 8V-71. It would eventually get to about 90 mph and did get a couple of MPG better. Same length but 96" and lighter. With a VW Rabbit for a toad, the worst I every got was 9.3 MPG in the Rockies. Was sure slow on the grades.
Pierce
I would investigate to see if gale banks still readjusts mechanical 8.3's.
More power can be geared higher. Normally improves mileage btw.
Turned up a lot of mechanical 8.3's.
More is better
I don't have a power problem. There is plenty of power. I rarely tow, and if I do it's light. I'm around 28,000-29,000. And I haven't fully gone over everything to insure it is in tip-top shape (valves, fuel pressure, etc).
The gearing is horrible on this coach. I don't know what they were thinking. 65 is ~1900 in 6th. 70mph is about 2050. 75mph is 2200. 2400 is max governed RPM.
In my mind, it should be geared so 1:1 gear (4th) is used around 50-55mph. A regular overdrive shouldn't be used until above 60 (5th). and a double overdrive should be for high speed flat cruising. There is nothing wrong with dropping down a gear for grades.
The only downside is I need to watch what RPM will be around 50-55mph to ensure I'm around the power band and don't end up in a bad spot between gears.
I also need to make sure 1st gear doesn't get too high...but I'm not making a significant change, so that won't be a problem.
I need to do this before I go out west and have long stretches of flat nothing. The east has more hills than people think.
at what RPM is Max torque achieved in your engine? Max torque is best efficiency. Most FT I have had have all been geared so that transmission is in top gear, and at Max torque RPM @ 65MPH
Is Max torque for your engine at 1900 RPM, or lower?
Krush,
You won't have a problem in first as it is MUCH higher numerically than first in our four speed Allison. That is the reason I have to back up our driveway rather than just heading up it. When the OD fifth and sixth are balanced against a 4.33 or 4.65 rear ratio, you will have far better gear selections than we do with our four speed. Fuel cutoff at 2110 RPM give us about 57 MPH in third so not the end of the world on grades. It does make "hunting" between third and fourth annoying if you don't just punch in third and relax.
You and your six speed will be happy with either of those ratios. Don't think you will find any bad spots between gears.
Yes, the east does have a lot of grades but they are shorter and much lower altitude but with a lot of rude drivers and a couple of low spots in each lane from overloaded trucks.
Third member from a RV wrecking yard seems a better choice than having a shop replace the R&P. Probably cheaper too. A couple of guys and a jack...but hey, you know the drill.
Pierce
Are you sure you mean "Max Torque" RPM? On my engine, Torque Peak (lb-ft) is listed as: 820 @ 1300 RPM. At 65 mph in 6th gear, I show about 1900 RPM - well above the Torque Peak.
Yes, I mean Peak Torque - what speed are you going at 1300 RPM again? My recollection from a Cummins Technical bulletin was that Diesel engines have the greatest efficiency at their peak torque RMP - in mine that is 65MPH at 1500 RPM as I recall. Thought it was similar in my ISM on my 1999 U-270 as well.
Or I could just be getting m ore senile.....
:-)
I'll have to try it out next time we drive the coach - I don't think I could get down to 1300 RPM in 6th gear, without the trans downshifting. But I could be wrong!
If it is possible, and IF it is a direct numerical relationship, then if 1900 RPM (in 6th) = 65 mph, 1300 RPM (in 6th) would = 44 mph.
Our 6V-92TA generates it's peak torque of 1020 ft lbs at 1200 RPM and 350HP at 2110 RPM. That's why they got away with a 4.xx first gear with the 746 Allison. A 8.3 Cummins is only slightly smaller in displacement so should have plenty of torque for a 1500 RPM cruise at 65 MPH in sixth gear. Any higher RPM at 65 means more piston speed/travel per mile and that usually translates to less MPG.
We could easily pull a rear end ratio down in the high 2.xx and still have plenty of power. Would give us a good third gear grade speed.
Pierce
That was the purpose for starting this thread-----to see if anybody has any hp/tq curves. I pasted one in the first message. It's the best i can find.
If you gear for max torque with out ability to ever get to rated hp RPM, you will be underpowered and overloading the engine. It's not about having torque to cruise at 65mph, it's about ensuring the engine makes enough HP at that RPM. BUT we have ANOTHER thread for that discussion!!!!!! HP vs Torque discussion (split from Overheat on Long Grade) (http://www.foreforums.com/index.php?topic=22731)
I found take out rear ends for ~$300 plus shipping. Just pull the axles and bolt it right in. Just heavy, but I've done worse.
The only thing I've heard is that RV's have "quiet ride" gears that are polished. I can get a rear from another RV that has quiet ride, but they are 4.63. I can also try to polish up the gears myself. But really, I don't think it's a huge deal as the rear is back by the engine making all that noise anyway.
Krush,
Good price for the gears assuming no moisture has been in the rear axle assembly (reddish cast to most everything) . As far as noise goes, if the mesh pattern is at the correct spot on the ring gear, they will "polish" themselves in short time when new. Only have heard noise out of straight cut gears or gears with improper mesh pattern. The right bearing preload, lash, mesh pattern mean a quiet rear end. Nice to have an old timer "lead" (as in lead paint) the gears, rock the ring gear back and forth a few teeth and give his opinion.
Rear ends that are quiet while slowing, make a slight clunk when you accelerate and then whine have incorrect lash and mesh pattern.
Pierce
They call it "QuietRide and noise sensitive bevel gear technology for quiet and smooth operation".
ear Axle: Meritor (Rockwell) RS-21-145 Quiet ride Motorhome Gearing 4.88 Ratio Manual: Renegade custom built motorhomes and toterhomes (http://www.wrightwaytrailers.com/Motorhomes_Toterhomes/Renegade/renegade_chassis_options.html)
I spoke breify with James T at FOT and he said it may be noiser because they use Quiet Ride gears. But, I haven't found specifically what the difference is. I bet, they just spend a few more minutes getting tolerances closer.
Decent article (geared more towards OTR trucks) on fuel mileage - lots of info - see page 23 for gearing discussion and RPM on ISM (Mine is right there 1500 - 1600 RPM at 65MPH. - which is max torque
other factors:
- and a host of other factors
From Page 23 of this Guide - discussing ISM:
ur experience to date with the Sure Start as a distributor is that we always see 60% or more LRA reduction when properly installed and sized.
The device will often actually reduce LRA more during the first 10 starts then after it has gone through the "learning" process, but on single phase applications 60% reduction (or more) is always achieved. Also, duration of the inrush event is not reduced (or lengthened) by an appreciable amount. SureStart will/does reduce LRA by 60% when properly applied/installed and LRA is properly measured with a meter that measure and report accurate in-rush current (in LRA). For example: the Fluke 375 True RMS clamp meter.
I am not sure why the poster's results differ from Hyper Engineering (and Generac) testing of the device over multiple test environments. Hyper engineering does stand behind the 60% reduction and will replace or refund the unit if it does not achieve the claimed 60% reduction in LRA when properly sized and installed.
Have read in a Cummins guide that peak "efficiency" WRT fuel is to have engine operate at Peak Torque - which was 1500 RPM I thought on my ISC and is 1600 I think on my ISM
I had a friend ( he has since passed away Replace the rear end in a U270 only to find that the WHINE was more than he could bear, he sold it soon after and I have no idea who has it know. He also related that he should have gone with RV REAR END. I also believe that a RV rear is set up more precisely than a truck would be.
Gary B
Tim,
Which way are they playing the power factor, leading or lagging to achieve the 60% reduction of LRA ? Would guess lagging but with Generac who knows the game plan, maybe a secret ?
Dave M
will send you a PM
100 LRA single phase will be 40 or less after install of Sure Start
One More - Cummins FMCA 2014 presentation .ppt
http://cumminsengines.com/uploads/docs/FMCA-presentation-August-2014.pdf (http://cumminsengines.com/uploads/docs/FMCA-presentation-August-2014.pdf)
sorry, forgot to add document link - here it is
http://cumminsengines.com/uploads/docs/cummins_secrets_of_better_fuel_economy.pdf (http://cumminsengines.com/uploads/docs/cummins_secrets_of_better_fuel_economy.pdf)
The first image I posted have brake specific fuel consumption. You'll see this is lowest around 1300-1400rpm. But, as we go back to the same topic again. Running where torque curve is maximum is pointless if your engine isn't making enough HP to maintain vehicle speed.
Give MERITOR technical dept., a call and run your idea past them before you go to the trouble and expense of this change (please.) Then put your calculator to work and determine the expense of your idea divided by planned mileage.
Unless you plan on going a distance, I'd bet the expense isn't worth your effort. pc
A couple hundred bucks to prevent a well known $3000 transmission repair on the p3 output bearing?
Had real noise problems in the 300 ORED rear ends starting in 1987. Howl under load.
Had to add gm positraction additive and b&m heavy weight rear end oil to make the noise inaudible brand new.
Oshkosh used the less expensive non polished gears. $40 difference oem cost.
40k miles later you could pull the pumpkin out and redo the backlash and the noise was reduced.
You could see the machining marks on the teeth. The quiet ones were shiny smooth.
Don't IMO.
Learned to max the power then regear. Did many different rigs.
Mechanical cummins if someone were inclined to do so can adjust the Bosch fuel pumps pressure with a screwdriver to turn the wheel under the hex nut. See gale banks as this has been done thousands of times safely.
Ten percent faster zero to,sixty at least. Screwdriver....
I assume at some point Foretravel switched from the mechanical to the electronic C8.3. If so, then what year?
Running at peak torque under heavy load such as head wind or slight grade can easily build exhaust temp. Engine speed is our friend in these situations. Try pulling a gentle grade into a headwind at 65mph with cruise on. I've accepted 64 mph is the all around most efficient cruise speed on the flats and down shifting to get RPM up when the pyrometer starts to climb. Amazing how flooring after downshifting significantly drops coolant and exhaust temps uphill in the Rockys!
Several owner operator Semi drivers and a knowledgeable member of this Forum have insisted I implement this technique. Factory might have known what they were doing with our rear ends? The aerodynamics alone make 75 + cruising laborious no matter how you gear our 8.3's
While our U300 makes 1020 ft lbs of torque at 1200 RPM, it does not taper off that much at the fuel cutoff of 2110 RPM. Sometimes we cruise at 55 or 60 but when in a hurry, I have gone several days at 82 MPH without a complaint. When it slows down on hills, I shift down but unless it wants to hunt between gears, I keep it petal to the metal letting up only when the engine temp gets to 200 and then dropping gears to keep it under the magic 200 mark. I have driven Detroits and Mercedes that way since the late 1960's with manual transmissions but exactly the same way without any kind of failure in several hundred thousand miles. Diesels whether Detroits, Mercedes, Cummins, CATs are built to produce max power as long as you don't overheat them or bog them down but the Allison takes care of the bog part and makes them pretty idiot proof as long as you watch the temperature gauge.
While I love my Detroit, I think Krush's Cummins will do the exact same thing day after day, mile after mile. It's the unskilled RV driver who thinks they can idle the engine all day while they have lunch or shuts it down to take photos after climbing a long grade without bringing the coolant and oil temperature down that damages the engine and shortens it's life.
Look at any big rig with over twice the load we have and probably pushing twice the air out of his or her way. You don't see them baby the engine. They shift down to keep the RPM up at the high end of the power band and move a lot more coolant at that RPM also while going down the road usually at much higher than the posted speed limit. The only thing that keeps a big rig at 65 is the price of diesel and not knowing who belongs to the headlights behind.
With the horsepower we have in our engines compared to marine use and the Allison automatic that won't let you lug the engine, even the newbie will have a hard time hurting the engine. Unless you have had a shop turn the fuel way up, EGTs are not going to be a problem with the Allison behind the engine.
We used to turn our engines at 2400 RPM in the fire service so the only worries I have at 2100 and 82 MPH is getting a ticket and paying for the extra fuel used. Cummins also makes great engines and being slightly smaller displacement (8.3 vs 9.0), allows it to turn at even higher RPM for extended periods also without any damage.
The biggest challenge for an RV driver is not going up the hills but coming down the grades in the correct gear and knowing how much to use the service brakes with the added bonus of a little retarder use if so equipped. The Allison takes most the thinking out of it going up but it can't do it all on the backside.
Pierce
It all comes down to how much HP is being USED at the RPM running at. Again, refer to the HP curve in the first post. If you are running 1800rpm and going 60mph and this requires less HP than the engine is capable of making at 1800rpm (the line), then the EGT will lower.
If you overload the engine at 1600 and require more HP than it is designed to put up to maintain that speed (above the line) EGT will go up.
It's all about matching available HP at an RPM to what is required to maintain the speed desired.
The premise of my exercise here is that going 65 mph doesn't require all the HP available (approx 300hp) at 1900rpm.
My coach is a 1998 and has mechanical cummins (engine is 1997). I think 1998 engines are electronic--making 1999 coaches have electronic engines.
Our 99' coach has a build date of July 98' and is an ISC (electronic 350HP), the engine was built in 98' as well of course, and was also as a 99' model year.
Don
So, original question: Where do I find a HP/Torque curve?
Krush,
I would choose one of these that is the closest to what you have. Don't know if yours is stock or modified but take a look: https://www.google.com/search?q=8.3+cummins+torque+curve+graph&espv=2&biw=1410&bih=779&tbm=isch&tbo=u&source=univ&sa=X&ei=sqc-VJS5LND4yQTRt4CgBA&ved=0CCoQsAQ (https://www.google.com/search?q=8.3+cummins+torque+curve+graph&espv=2&biw=1410&bih=779&tbm=isch&tbo=u&source=univ&sa=X&ei=sqc-VJS5LND4yQTRt4CgBA&ved=0CCoQsAQ)
Pierce
While trying to figure how to hot rod your small engine, why not think of a larger Big Boy engine that gets the job done day in & day out ?
Could never figure why folks buy the little engines, guess due to being unaware and just looking at $$$$ only ? Looks like one needs to live with their toy as is.
Me, I love whopping butt on mountain up grades, everyone goes screaming past me on the down grades with brakes smoking. Another reason I laugh.
Take it to a Cummins dealer, have them put it on the dyno, you will have all the info you need for your engine, then you can be sure it is running up to snuf.
FYI, dyno's are hard on rear tires as they heat up too much. Also radiator may not get enough air flow to keep coolant temps low.
And while I am at it, steam cleaning pressure washing engines can be hard on gaskets, electrical parts, etc. I have seen Cummins require steam cleaning, even if not dirty, before working on engine. Also radiator fins can be bent with pressure washer.
I think you
do have a power problem. The curves you showed appear to be reasonable given the stated torque and horsepower for your engine. Your problem is that the engine needs to spin up to a high RPM to develop its rated horsepower.
Contrast that with the M11 in my U320 which weighs roughly the same as your coach, and develops roughly the same wind resistance at a given speed. My M11 develops about 370 hp at the 1500 RPM that it turns at around 70 MPH.
It's pretty clear why they chose the axle ratio they did for your coach. The small torque of your engine means that it has to spin at a high RPM to develop reasonable horsepower and that requires roughly the axle ratio they chose to perform adequately under typical conditions.
I completely agree! The M11 in our coach is perfect for the application. It develops 1350 lb-ft at 1200 RPM, and 370 hp at 1500 RPM at about 70 MPH, which is where we like to cruise. With 400 hp at 1800 RPM it performs very nicely both in the mountains and on the flats.
I'd be very happy to have your 500 hp, but I try not to be greedy! ;D
You could probably run lower RPM at 70mph on the flat. What is your boost at that speed/rpm? Or do you have a read out that gives you % of power.
Where did I state I was trying to go faster up hills? I stated I'm trying to go faster on the level. There is a known problem with the p3 carrier bearing going bad on these coaches. Coaches that are driven around 60mph don't seem to develop this problems. Coaches driven around 70mph do.
U295 Driveline vibration issues (http://www.beamalarm.com/Documents/foretravel_u295_driveline_vibration_issues.html)
A double overdrive (6th) isn't meant to be engaged at 50-55mph.
Downshifting for hills allows the engine to get to the proper RPM to produce HP needed.
I A) don't want to blow up my transmission by driving 70-75mph and B) hopefully get a tiny bit better fuel economy.
How about this...I realistically cannot drive my coach at 75mph. Driveshaft RPM is too fast (big deal) and engine RPM is unnecessarily fast (not a huge deal).
Another fact: in 1999, coaches went to 4.63 gearing (350hp) from 5.13 (325hp) in 1998. Hmmmmmmmm...the mother ship changed something!
Lastly, I have a 34' coach. I like it, I don't want a 36. I wish it was 30' foot or less. The 8.3 is a great engine and easy to maintain and gets great economy. I have all the power I need.
You guys are trying to out think the situation. Just stick the 4.63 (or lower) in and be happy. It will be the same final drive as our U300, be lighter and with 6 speeds with a higher numerical first gear, way quicker and faster in a quarter mile. Better (more) ratios for the grades so probably faster up those too. Foretravel got it right on a lot of things but also missed the boat on others. At the $300 plus shipping quoted earlier, that's almost free with not much labor for installation.
I have dropped ratios in many diesel cars and trucks and have been happy with the results every time. If ours were a 6 speed with OD 5th and 6th, I would drop the ratio to a 4.33 in a second.
Pierce
Pierce makes a good point: If you want the engine to turn at a lower RIM then change the differential to a numerically lower ratio. Simple!
Gale Banks engineering might have it on their site.
They offer proven kits and help for 93-98 cummins "c' engines up to an including your 325hp.
Many customers with better mileage, more power, advice on gearing needed.
I would only buy a mechanical 8.3 knowing I could buy the banks kit for it.
You have the right coach and cooling and stopping systems.
Look at their website and call them IMO.
Presently using the stock gearing of 3.91, but thinking maybe need to check for other ratios like 4.11, 4.33,4.44, 4.56. Need to run the numbers and see what the present housing is capable of using. Always playing gear ratios, not looking for mpg, just get er done within reason. And yes having two over drive radios is good, Boys & toys. ;D
I have an email sent to Cummins tech service...hopefully they return the specs I want.
I found this post via google on another forum. It's the internet, so I am always skeptical. But, the numbers sound right.
https://www.rv.net/FORUM/index.cfm/fuseaction/thread/tid/23812743/srt/pd/pging/1/page/2.cfm (https://www.rv.net/FORUM/index.cfm/fuseaction/thread/tid/23812743/srt/pd/pging/1/page/2.cfm)
You have a 325
I would buy any coach knowing I am going to be happy with it as it is. I would never buy a motorhome wanting to later modify it for more power. If I want/need more power, I need to buy a different model with higher horsepower. All power increases can come with unknown issues, including the popular Banks.
We know several are VERY happy with their Banks systems and would not trade it for anything.
And we also know Banks user that found exhaust temps too high and removed the Banks rather than taking so much time watching EGT gauge, with the risk of damaging engine. Often more power can result in more heat.
Aftermarket turbo kits always go hand in hand with adding fuel to the injection pump. Add too much and you get smoke and high EGTs. Unless the mechanical injection pump has an altitude compensator, the EGT will go UP with increased altitude. High altitude together with a restricted air cleaner can really raise the exhaust temperature.
As far as having to watch the EGT gauge, an engine with a turbo kit installed may lower the EGT if you take some of the extra fuel out of the pump. Some people get too greedy and boost too much or add too much fuel or both or drive their modified diesel with a restricted air cleaner. Hard to imagine a stock Foretravel with an Allison controlling the shift points having to worry about high exhaust temps. Another reason this old diesel saying was true, especially with manual transmissions, "Drive it like you stole it", meaning high RPM translates into lower EGT in turn translates into longer engine life. Very hard for many gasoline car drivers to be able to understand or do.
EGT probe goes before the turbine wheel, not after for correct reading.
Pierce
I made excel sheet with speed vs engine RPM for 5.13, 4.63, and 4.33 gears---for each gear 1st through 6th. Lower on the sheet is RPM of driveshaft.
520 is what I used rev's per mile. This matches up to a michelin number and the number seem to match up to my Tach and Speedometer.
Doing a bit of analysis shows me that 4.33 is going to probably be the choice. 4.33 allows for a nice 72mph cruise of 1800rpm (which is a nice good blend of HP and efficiency). 65mph will give around 1600. This is for FLAT cruising.
If there is a problem, pop it down into 5th, and we basically are at the same conditions as the original 5.13 gearing....meaning 5th with 4.33 is about same overall ratio as 6th with 5.13.
And 4.33 in 4th gear gives 2050rpm at 55mph...perfect for the hill climbs.
Of course, this is all in theory ;). But, since 1999+ coaches have 4.63 gears and nobody seems to complain, I think this should work out well.
I don't plan on doing banks kit or upping the fuel. My power is fine. Gearing doesn't change power.
The jump from 4th to 5th means that peak HP (2100 or so) is going to be ~55mph or ~75mph. But 65 in 5th gear should be fine for a fair grade.
IF you ever sell your coach a 400hp ten mpg rig is worth more than the cost of the work. $10-$15k+. Trust me after selling a lot of high line motorhomes.
IF you were fortunate enough to have a modifiable coach and did not I would be able to buy it for less and add to its future value cheaply.
Especially for anyone who travels the Rockies which it seems you do not do.
With the increased power you could lower the numerical ratios even more. Better mpg.
Regeared many 3176 Marquis because of adding power.
Some future time the banks parts may be unavailable. Old already.
Safer having a coach that on a six percent grade does not have to go in and out of the truck lanes.
Or without a tow can be in the left lane up hills. Power sells rv's. Type "a" are not patient.
For sure adds resale and owners enjoyment.
I hated driving around the steep grades where the pretty was to stay on the flatter bottom of the canyon roads.
My two cents. You have an enviable coach that can legally and safely be rerated.
We'll see how it runs and decide on more HP at that point. I don't hear of many banks upgrades on the 325hp. Regardless, even with 400hp, the power band is going to be the same RPM range, so the gearing probably won't need to be changed.
I doubt I'll ever sell the coach. I usually run things "into the ground". Besides, they don't make them like this anymore--what would I replace it with? 34', no slides, simple, easy to maintain, well wired and built.
Not only for Krush but for anyone with questions about tires size comparisons, mph, rpm, etc., this is an excellent site for just sticking in your information, hitting the calculate button and there you go. Calulators from [url=http://www.4Lo.com]www.4Lo.com (http://www.4lo.com/4LoCalc.htm)[/url]
OK, how realistic is it to change from a 5.13 to 4.65 rear end ratio?
Our U300 HT746 four speed ratios starting with first gear
3.69, 2.02, 1.38, 1:1 in fourth
MD3060R six speed ratios starting with first gear
3.49, 2.86, 1.41, 1:1, .75, .65
Right now I can go 21 mph in first at 2100 RPM (with a 3.08 rear axle ratio). A U270 after a rear end change to 3.65 is going to be able to go 16 MPH in first at 2200 RPM. Translation: even after dropping the rear end ratio from 5.13 to 4.65, the U270 is going to run all over me from a stop light or will have a much easier time on an uphill start. My extra .7 liters, 25 HP and 1020 ft lbs of torque are not going to make up the difference. Top governed speed for our U300 is almost 82 MPH @2100 with the U270 turning the engine a little faster @2200 RPM would be 86.4 MPH Our tire sizes are only about one revolution per mile difference. We get to 82 MPH in a hurry and expect the U270 would only be slightly slower in top gear acceleration and the close 5th to 6th ratio would make up for that.
My bottom line: conversion from a 5.13 to a 4.65 seems a slam dunk. I have never driven a 8.3 so not sure how I feel about going to a 4.33. That would give a theoretical top speed of 93 MPH but I don't think the 8.3 would have nearly enough oats to push that much air aside. Sixth gear would probably be limited to flat ground without a headwind. The Allison should automatically shift down to keep the EGT within safe limits.
FYI: a Michelin 275/80 (Michelin, Goodyear, Continental) and most any brand of 295/75 are almost exactly the same diameter with the 295 only turning about one less revolution per mile. The 295/75 does have a little bigger footprint on the road.
For gear heads who might want to know their Allison 6 speed ratios by model, see: Allison 6-Speed Automatic Transmissions (http://www.vibratesoftware.com/html_help2014/2011/Allison/allison_6speed_auto_trans.htm#MD) 3060 R
Pierce
This site has more specs on it as well for transmissions (convertor details, etc). http://www.utxchange.com/faq/transmission-specifications/ (http://www.utxchange.com/faq/transmission-specifications/)
The thing about gearing...as long as 1st is good enough to get going, one can always downshift from 6th to 5th.
My intention is to turn 6th gear into a "Only use on level ground 65 or above".
The other MAIN goal, is to get driveshaft RPM lower.
Price for the rear is $375, plus $150 core. I may be able to pick it up and save the 150-200 shipping. Labor is free.
If you have the garage space, nice to put the 5.13 in a box. $150 goes nowhere buying a third member later.
I have noticed the Allison kit for the drive shaft problem. Would talk to the factory about the high driveshaft RPM part failure. Can't believe they haven't fixed it. A lot of RVs use that transmission.
Pierce
No plan on turning over a perfectly good diff for $150. Plus, if I have to swap it back in......
Simply more info on ISM......perhaps mirrors what Tim found in the excellent references he found.
I found this chart in my FT book for my ISM, the chart is by Cummins and data is listed as restricted to RV, Coach and Fire Trucks.
Peak torque of 1450 lb-ft at 1200 rpm, and torque 1050 at 2100 rpm
Peak hp of 450 BHP at 1800 rpm, and 420 at 2100 rpm
recommended cruise RPM and Best Performance listed as between 1700 and 2000 rpm. Best economy 1200 to 1800 rpm
I see on dash tachometer that we are at approx 1375 rpm at 64-65 mph (per odometer and GPS)
I was riding right behind the driver in a new Mexican Mercedes bus. I think it had the Detroit 13 liter four stroke DD13 (OM471) in it with a 6 speed manual. My technical Spanish is not that good. He had a very small green range on the tach from about 900 to 1300 RPM. Redline was 2000 but think they used the lower range for economy. I was amazed at the torque it had. Even with a full load, it pushed you back against the seat for about 3 seconds then shifted to the next gear and back in the seat again. Very smooth. The late electronic engines are really amazing for power and with the massive torque at just above idle, they must get good fuel mileage as well operating at low RPM even on the highway.
Pierce
The M11 or ISM in the 400 to 450 hp range is really the ideal engine for these motorhomes. Ours runs at about 1500 RPM at 70 MPH and the coach rides and handles perfectly. The high torque at low RPM makes all the difference since.it doesn't have to spin up to a high RPM to make the required horsepower as do the smaller engines.
I love my ISM and I want to try to wear it out.
My lucky phone call resulted in a u320 coach. Poetic justice in a good way for an old Foretravel salesman/sales manager. Add Aqua hot and its even better.
Adding in the mid entry WTBI 40' and the Foretravel gods took care of us IMO.
After rv'ing in countless brands and floor plans while in the biz the u320 is a revelation.
Cm and ray hit it over the fence.
X3
Our 36' U295 came to us with Cummins C8.3 325 with Banks Stinger package. We've had it for 4 1/2 years, ~60K miles, and so far:
it starts reliably
it shuts down reliably
it accelerates the coach with towed vehicle at a reasonable pace
it doesn't overheat the coolant, even climbing mountains in hot weather, if we pay attention to conditions
it doesn't overheat the turbocharger if we pay attention to conditions
it cruises well at 65 mph and will run 75 on flat ground if you are patient
I don't know what the torque and horsepower curves look like, but performance is satisfactory for a 33K pound RV combination. Folk with electronic engines generally report better fuel mileage in similar coaches, but our fuel mileage is reasonable for the system we have.
We will stick with "pretty much stock" on mechanical issues, and our "extras" will be aesthetic changes.
It's fun and interesting that people like to explore different ways of customizing their "rides."
Before buying, I researched the difference between the mechanical and electronic c8.3's. The internet experts seem to say that the mechanicals often get slightly better fuel mileage. I really didn't if it was electronic or mechanical. Mechanical is simpler to fix; electronic gives more data.
I did more research into the electronic stuff and found that I could get an OEM setup scan tool for the tranny and electronic engines pretty easily (and just some $$$$).
But, I wanted a 34' coach and this one popped up. I'm really happy with it. I wish it were even shorter, but this works out nicely.
The u320's have lots of extra stuff on them I really don't want. I don't want all the systems and the aquahot. That extra HP sounds great, but there is a fair amount of extra weight too. The difference in "more torque" between the 8.3 and m11 isn't that great....a few hundred RPM.
I've never had complaints about power. Sure, I haven't climbed the Rockies, I don't tow 10,000lbs, but what's the rush?
If I do the banks mods and go from 325hp to say around 400, I'm almost up to m11 territory. The HP isn't needed for going down the level (probably 75% or more of most people's driving). Making HP requires fuel.
My temp gauge has never moved off 180deg. Even climbing mountains.
And if I ever really get grumpy, I can buy bigger...or put in bigger engine. Repowering is cheaper than a new coach!
A mechanical C series should have a Bosch P7100 pump. That pump was used in hundreds of different applications/calibrations and can supply enough fuel for more horsepower than your transmission can handle.
(Your modification scheme will follow a similar formula to the guys who build 2nd generation Dodge trucks.)
Boost and EGT gauges. Reliable accurate information is NECESSARY when running a modded diesel. The EG thermocouple should be installed in the manifold pre turbo.
You can likely get noticeable gains by optimizing the wastegate rod adjustment and pump calibration (Fuel plate, Timing, AFC). You do not need any new parts at this stage other than the gauges mentioned above.
If you want to spend some dollars do the following:
Larger Turbo/Exhaust You likely have a Holset HX40 (not certain on this) and can fairly easily bolt on an HX50/55. Or a hybrid HX40/50. The Holsets are semi modular and you can mix and match. I believe the Banks Stinger package replaces just the hot side of the turbo. After you pick a turbo run the biggest free flowing exhaust system possible.
Holset Turbo Model Information (http://www.myholsetturbo.com/modelinfo.html)
Custom Fuel Plate Many options out there... Here is a good place to start.
http://tstproducts.com/tstpowerkitwithoutvideo.aspx (http://tstproducts.com/tstpowerkitwithoutvideo.aspx)
The above done right can build a solid 450HP C series. You will have enough fueling capability to hurt the engine if driven incorrectly. You MUST have a pyrometer and you MUST learn to drive accordingly.
The next stage adds upgrading the inter-cooler and fuel system... Then you could add water/methanol injection or propane injection.
With the right gauges and understanding of how to drive it a 600HP C series would thrive in a Foretravel.
I like this gauge.
https://www.spatechnique.com/product_pages/productdetails.cfm?id=376 (https://www.spatechnique.com/product_pages/productdetails.cfm?id=376)
It has programmable alarms for boost/EGT and can drive an external circuit and a 2nd set point to trigger a water misting system (as an example)
Lots of options for mechanical engines.
Have Fun!!!
(Just for reference)
http://assets.bankspower.com/manuals/45/96381.pdf (http://assets.bankspower.com/manuals/45/96381.pdf)
From your fuel plate link: "These kits do not work on the '97 and later 300 or higher horsepower mechanical engines. "
I didn't buy an RV to go fast. Trying to get more HP for bragging rights is foolish. I like reliability.
Okay, I'll bite... just to satisfy my curiosity, what options are there for the ISC series engines? Obviously, a resonator, and of course even with out any mods a Pyro gage is a good idea, but since Banks stopped offering the ISC Power Pack and Stinger options (apparently because of the Ottomind controller for the engine no longer being produced), a web search primarily brings up these "Chip" modules. A resonator is going on at the earliest opportunity (well, the earliest opportunity that makes sense in terms of project priority), but just interested in gathering information about other options at this point...
Don
Just have to remember as an example, that a 5.9 ISB Cummins has a B50 life of 350,000 miles. As modifications are made, some may drop that down both because of the modification itself and also because of the necessary increased driver awareness for items like the EGT. Others, like the exhaust, may have a positive effect on engine life. A free flowing muffler may reduce back pressure on the downstream side of the turbo resulting in lower EGT at any throttle setting.
Pierce
Don,
Chipping an electronic diesel engine will give it more fuel but without giving it more air/boost, you will see more smoke and higher, possibly dangerously higher EGTs. No one wants to be sitting on the side of the road a thousand miles from home having made a $20,000 mistake. Modification over what the factory thinks best has to be a very careful and well researched process.
I still remember a chipped Dodge PU that was wicked fast even pulling a long horse trailer. A couple hours later, he was sitting on the side of the road going into Winnemucca with his hood up.
Pierce
being stupid about hot rodding anything tends to be expensive, seems the way for hard lessons and hard heads. my ism will go lots more power & torque, but the coach design for radiator, transmission & structure are not designed for it, if it were there would be a ISX in place of the ism500
there really are folks who can destroy anvils with a feather !
My experience with Exhaust Gas Temp / EGT / Pyrometers is that the probe produces millivolts and the dash gauge converts millivolts into temperature reading. Since every installation is different in length of probe wire lengths, types of wire, size of wire, etc, the gauge 'should' be calibrated to the probe with its finished wire run. Calibration may include sticking probe in know temps like boiling 212 degrees & freezing 32 degree solutions. This calibration and installations without calibration can lead to incorrect gauge readouts.
We recently changed to much better solution. VEI Systems manufactures their pyrometer with a 'hardwired' permanent controller that resides in the engine compartment. Calibration is done during manufacturing and none is needed or possible when in our hands. We then use ordinary pre-existing automotive wires to connect the dash gauge to the engine located controller. I know of no other EGT gauge that takes this approach.
Here is the VEI probe/controller which must be used with their gauge:
http://www.veisystems.com/ws/sensors-accessories/19-egtpyrometer-probe-controller.html (http://www.veisystems.com/ws/sensors-accessories/19-egtpyrometer-probe-controller.html)
V1 Series Pyrometer/Exhaust-Gas Temperature Monitor - VEI Systems (http://www.veisystems.com/ws/v1-series-single-gauges/32-v1-series-pyrometerexhaust-gas-temperature-monitor-.html)
We are also using a matching VEI boost gauge, although it is probably similar to other boost gauges on the market.
http://www.foreforums.com/index.php?topic (http://www.foreforums.com/index.php?topic) 537.msg150063#msg150063
Our coach goes down the road at 29K (Non slide U320 with a "weekend" load of gear) and has a rated 450HP... Thats 65lbs/HP and for the types terrain we run on the West coast I would like more.
Going fast is not the goal; Maintaining speed on hills is... Being able to merge at speed is... Passing in a safe manner is...
Being passed by loaded log trucks is something best avoided.
As far as longevity goes I would not hesitate to say a properly maintained carefully optimized C8.3 would outlast the rest of the coach. With the one disclaimer being you never let your pre turbo EGT get above 1200 (And if it was my rig the limit would be 1150). Would the ultimate longevity be less, of course it would. Would it matter... very likely no.
Cummins sells a 600HP C series for marine use. The marine duty cycle is tougher than the automotive duty cycle by a significant margin. Access to unlimited cooling is why it works.
OEM's are held to a reliability standard that is limited by the nut behind the wheel. They can't release a calibration that an operator can damage. The aftermarket is a bit less constrained here but they also have to assume a less than careful operator... I am running under the belief that the people hanging out around here do not fit the last category.
Cheers
Chris
This is on Quick Serve. Never got an email back from Cummins regarding dyno plot. I have a friend that is Cummins distributor looking into it for me.
FR90200 RATING,FUEL Fuel Rating
Advertised HP: 325 @ 2200 RPM
Secondary Adv HP: N/A @ N/A RPM
Governed HP: 305 @ 2400 RPM
Governor Regulation (%): 9.5
Torque Peak (lb ft): 915 @ 1300
Fuel Pump Manufacturer/Model: Bosch P7100
Fuel Pump Mounted Angle: 35 degree
Governor Type: RQVK
Boost Control Provided: Yes
Fuel Pump Type: Inline
High Pressure Fuel Line ID (mm): 1.8mm (0.07in)
Low Idle Setting: 750
High Idle: 2710
Engine Application: Automotive
SUPP Emission Test (gms/BHp-hr BSNOx): 6.0
CPL: 2169, 2191
Certified By: None, EPA
Export
Certification Year: 1997
Engine Cylinders: 6
Engine Family: C Series
Structure Code: 02 EBM
Manufacturer of Record:Cummins
Fuel Type: Diesel
Cylinder Head Material: Moly
Peak Power: 325
Governor Break RPM: 2475
Derate to No Air Curve
Provision: No
FP Gear Timing (deg crank):
0 deg retarded
Engine Design Phase: Current Product
Engine Aspiration: Charge Air Cooled
High Altitude (>10K feet)
Rating: No
Managed Torque: No
Speed Sensor Location: N/A.
Easy mod was to remove the hex nut on the Bosch fuel pump and turn the visible wheel in about two turns.
Marked the edge with finger nail Polish so you can see it turn.
Worked on all engines. No heating. No smoke. Did a lot.
Shame no banks kits.
What does turning the wheel do?
And what does turning the one or two screws with male hex wrench do?
The cover is a 8mm hex. After removal a vertical wheel is exposed. The edge is serrated.
Mark the wheel for a reference with fingernail polish and rotating the edge of the wheel turns a screw in and increases the fuel flow.
A short drive after adjustment shows additional performance on all bosch pumps.
Naturally I am not suggesting violating any emissions rules or trans capacity or cooling systems capacities.
Just a hypothetical discussion. Correct?
Lots of customers smiles long ago
Bob, How about a picture of this wheel, I have the 5.9BT CAC using the Bosch inline injection pump in the FL60 Freightliner rated at 190 hp, does fine, but moe fine is OK too.
Cutaway of P-7100, showing items being discussed. Ignore all the Bubba comments after the first couple posts...
12 Valve AFC Mod's - New England Turbo Diesel Power (http://www.newenglandturbodieselpower.com/Forums/showthread.php?t=925)
Thank you Chuck, that is a great break down.
Thanks Bob for the star wheel explanation and Chuck for the great link to the cut-away pump.
I once saw a tech remove the plug and adjust the star wheel, which I think I now see what happened.
It seemed the star wheel was mounted facing the rear of the coach with the turning toward the side of the engine.
But in a separate action the tech used a T-handle long male hex tool to reach in and turn one or two screws.
Don't know if a cover plate was removed before reaching to the screws. The tool was positioned toward the side of the engine. Do you know what was being adjusted with the T-handle hex wrench?
Also in Chuck's cut-out link, I am not sure how the cut out is oriented to our motorhomes.
What is top and what faces the rear of the coach (front of engine)?
Ya'll are getting into stuff few people really have business messing with. These guys that crank up all the stuff on their pickup trucks are playing a completely different game than us. A) few of they actually pull any weight--their trucks are 5,000lb B) They are ignorant to the long term reliability problems they are causing.
Turning the "star wheel" doesn't increase power. It adjusts how much fuel is allowed to the engine before full boost is built up. The purpose of this is to reduce black smoke on acceleration.
Changing/removing/adjusting the fuel plate changes the max amount of fuel that is injected. At the 325hp mark, mine is pretty far up there.
More fuel can be added to make more power. Changing the fuel plate gets to a point, then displacements and what not inside the injection pump need to be modified.
I have a friend that overhauls injections pumps and injectors. These devices are very complex and take a lot to set up. "Just turning" a screw or nut here and there doesn't even begin to explain how much you can mess the fine balance of a perfectly running engine up.
BUT, if you understand what is going on, how all the components work, and totally realize the risks, then you can crank up the fuel and get more power!
Looks great. Someone must have a downloadable fuelplate template(s) to allow easy copying. Nice to have a template with a HP/torque graph included for each profile. Looks pretty easy to go overboard.
If the pump were mounted in a PU, what you are looking at would be facing the back of the PU. In a diesel pusher, it would face the front of the coach. The opposite end away from the engine crankshaft pulley. The pump plugs into the timer driven off the timing gears/chain. The top is up in the photo.
Has Dodge every put a strong trans in anything?
Pierce
Cummins engineer at a show long ago mentioned Chrysler had asked about turning down the torque on the early 5.9's.
To give an update to this project. I just did a 20 mile test drive down the interstate with my 4.33 rear end that I installed. I now have a 80-85mph coach with no sweat! But, my goal was to get around 75mph at 1800rpm in 6th gear. Well, 1800rpm gives 74 mph; exactly what my calculations predicted in the spreadsheet I put up earlier in this thread.
With stock 5.13 gear I had 62mph at 1800rpm in 6th gear, now it's 74mph 6th gear 1800rpm. And it pulls the minor hills we have around here no problem. I was speeding up to see how everything felt and I looked down and was doing 82mph!!! I couldn't even tell. The engine was only at 1950rpm!
My vibrations also seem to be gone, and I believe this is due to the slower spinner driveshaft.
There is a tiny bit more noise and gear whine. This is because I got a used differential out of a truck and it doesn't have "coach quality gears" that are very polished. I touched up the gears a bit, but the whine is hardly noticeable; with the radio on, it is insignificant.
I'll run it around for a while and see how it handles the rockies. I might should've gone with 4.11! Anyway, so far I am highly pleased. I can now run 70mph and the coach loves it.
I used to add heavier rear end oil to curtail the sounds on 300 cat oreds.
I swapped the rear end out on my own. I had to pull the yoke off the used rear that I bought and install a closed yoke. I just bought a new yoke ($100) because I didn't want to mess with the existing rear end in case I had to reinstall it. The diff weighs 250-300lbs. I used a harbor freight motorycle lift to install it--plus some nice redneck rigging. It's not that tough of a job, but it takes some thinking and some muscles.
I was told that after enough miles the tooth finish polished itself smoother.
To reduce the noise a reset of the backlash was necessary if memory serves me.
Would be great to have a factual comparison of climbing ability (same hill, same entry speed, speed at top and gear/RPM at the top) and MPG.
And would I get all that data without spending a week driving around various hills and gathering information both before and after? I have a mechanical engine, real time MPG isn't practical. I did post facts of what new RPM vs MPH are. And I posted a spread sheet with the calculations showing what changes in RPM will be for given MPH in respective gears. The calcs match up to what I observed on my test ride regarding RPM vs MPH readings.
Subjective observations show that there is plenty of power on the highway....which makes sense, because gearing was analyzed against dyno data given by cummins.
Pictures of the process, sort of, LOL.
Krush,
Are those magnets inside the housing not far from the drain plug?
This still leaves you with a closer set of ratios than our 4 speed with a better first gear and a taller sixth gear than our fourth gear so better fuel mileage. I expect you will be very happy with it on hills.
Pierce
Admire your work. Krush. And great photos!
jor
The rectangle are indeed magnets. The pictures shows "as found" before I cleaned them off. I'll get some miles on it and see if maybe I should've done 4.11! Regardless, the 4.33 is a HUGE improvement.
I got all the tricks figured out for swapping it out now. I had to do this evolution twice...the first diff they sold me was the wrong one! And I'll freely admit I should've have double checked to see if the axles fit on the floor before installing it--I know better. Anyway, the second install of the correct unit went much smoother.
The only other step was swapping yokes. It took a bit of figuring and trial and error to get the tooling right, but I used the wheel lug multiplier I got a while back and had to buy a 1inch drive 35mm socket. The nut for the yoke is 1000ft-lb. Then I just used a two jaw puller to get the old yoke off. Installed removed and installed a new seal.
Now, the 2 jaw puller didn't work for the closed yoke (the leadscrew wasn't long enough). So I made a special tool, like the OEM one. A piece of pipe with two holes in it that fits in the closed yoke part, and just put a steering wheel puller inside the pipe. Pulled it right off. Now with all the tooling made and available, the task isn't that complex---but still bull work shoving 300lbs around!
Also, first install I used what Meritor calls for in manual, 5699 RTV (and what they originally used). But second time I used Loctite 518 anerobic. RTV is a pain to clean and doesn't give me time to assemble. 518 also doesn't cure when exposed to air, so excess inside doesn't make a mess.
The one picture is of the removed 5.13 unit with polished gears. There are definitely polished and very smooth. But for less than $500 all in (minus labor), can't beat a good used unit.
Awesome project, and great photos. Certainly not recommended for the "average" shade tree mechanic (like me)...
The 4.11 would lower highway revs a bit but raise EGTs some at the same speed and decrease coolant flow. You might end up spending more time in a lower gear. Think you made a good choice and good documentation too.
I would love to bring our 60 mph revs down about 100 rpm but with our four speed, it would make first a little taller than I would like. Right now, it's too tall to climb our driveway so have to back up it.
Pierce
When we were drag racing in the sixty's we used white lead to set up a rear gear.
The old school newspaper method is the best--- set up the gears so the paper is crimped as you rotate it through the gears. If it cuts the paper it's to tight, and if it doesn't crimp the paper it's too loose. Works every time.
Yes and you can position the contact area where you like on the ring & pinion for a long lasting quiet setup.
End of year update. I have about 15,000 miles on the 4.33 gears and am totally happy. For rolling hills I manually select 5th gear and it handles them great. For real hill climbs, down to 4th and just climb the hill at 2200RPM and 59mph. No noticeable gear noise.
On the level in 6th gear the engine just purs along at 70-75mph with plenty of power (1800rpm). 60 to 65 is even lower rpm with plenty of power.
Figured the 4.33 would be perfect. Glad you like it. How about mileage? Would think it would be good for one more MPG. Always satisfying to do it on paper and then have it work out perfectly.
Pierce
I think mileage may have improved slightly. But, it's not a fair comparison because before I was driving 62-64mph and now I drive 70-75. So any increase in mpg was lost due to increase in average speed.
I seem to be getting 8.5 to 9mpg. But again, I cruise 70-75 when able. Top speed was about 95mph, for those that are curious.
Wind drag from 62-64 to 70-75 decreases my mileage more than 1 mpg
It may be the same too. Really, I didn't notice a change in fuel mileage--if there was it was small. But I do drive much faster now. So the takeaway is that I can't
truly speak if there was an improvement in fuel mileage. But, all else being equal, it appears mileage improved with the gear change.
Also, I forgot to put in my update the following information: A main reason for this gear change was to reduce/eliminate vibration that I had over 65mph. Also, it was to prevent failure of the p3 bearing that many FT owners have had replaced in the transmission. I feel that the vibration and failure is caused by the drive-shaft spinning too fast while going 65mph or faster. The higher rear end ratio has eliminated this problem and hopefully I will never have the p3 bearing problems that others have experienced.
An update: Been almost two years and another 10-15k miles (nearly 30,000 total). All is great, no issues. Any slight increase gear whine at highway speed is negligible and is covered by wind noise. On rolling hills I manual select 5th gear. On flat, I cruise ~1700rpm at 70. If no rush, I tend to cruise around 68mph.
This gear change really shines on the flat land. But it also puts the power range in better use for hills too.
Thanks for the update, seems logical. Does it seem that 5th (overdrive) gear puts you back at 5.13? Does it act like you have a shiftable rear axle, with overdrive 5 & 6th gear.
With the 4.33 the 5th gear is basically just like 6th was with the 5.13. Somewhere in this thread or another I have my excel spreadsheet where I did all the calcs. It kicks down to 5th as needed, but I usually run in eco mode so it doesn't shift as much. The problem with eco mode is that by the time it shifts down to 5th, it may be too late and RPM will be much below peak power. If there is going up/down in shifting a lot, I just put it in 5th. I treat 6th as a true overdrive for flat land cruising.
Kicking down to 4th gives max HP RPM (2200RPM, I think) right at 59mph. This works well for most hills. The only downside is that if it is really steep, the jump from 4th to 3rd is pretty large....if can't keep speed in 4th going up the hill, I may be climbing at 42mph at 2200RPM in 3rd. A 10 speed would really make the 8.3 pull a lot better on various grades.