Rear end gear change from 5.13 to 4.33 on 8.3 Cummins u270

Topic: Rear end gear change from 5.13 to 4.33 on 8.3 Cummins u270 (Read 5317 times) previous topic - next topic

Re: 8.3 325hp mechanical torque and hp curve

Reply #50 – October 16, 2014, 11:25:12 am

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.

Re: 8.3 325hp mechanical torque and hp curve

Reply #51 – October 16, 2014, 12:35:50 pm

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[/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 3060 R

Pierce

Re: 8.3 325hp mechanical torque and hp curve

Reply #52 – October 16, 2014, 02:16:30 pm

This site has more specs on it as well for transmissions (convertor details, etc). 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.

Re: 8.3 325hp mechanical torque and hp curve

Reply #53 – October 16, 2014, 02:35:22 pm

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

Re: 8.3 325hp mechanical torque and hp curve

Reply #54 – October 16, 2014, 02:44:02 pm

No plan on turning over a perfectly good diff for $150. Plus, if I have to swap it back in......

Re: 8.3 325hp mechanical torque and hp curve

Reply #55 – October 16, 2014, 06:25:51 pm

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)

Re: 8.3 325hp mechanical torque and hp curve

Reply #56 – October 16, 2014, 07:51:51 pm

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

Re: 8.3 325hp mechanical torque and hp curve

Reply #57 – October 16, 2014, 08:50:34 pm

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.

Re: 8.3 325hp mechanical torque and hp curve

Reply #58 – October 16, 2014, 09:13:14 pm

I love my ISM and I want to try to wear it out.

Re: 8.3 325hp mechanical torque and hp curve

Reply #59 – October 16, 2014, 09:42:08 pm

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.

Re: 8.3 325hp mechanical torque and hp curve

Reply #60 – October 16, 2014, 09:59:45 pm

Re: 8.3 325hp mechanical torque and hp curve

Reply #61 – October 16, 2014, 10:20:03 pm

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."

Re: 8.3 325hp mechanical torque and hp curve

Reply #62 – October 16, 2014, 11:48:21 pm

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!

Re: 8.3 325hp mechanical torque and hp curve

Reply #63 – October 19, 2014, 11:32:20 am

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

Custom Fuel Plate Many options out there... Here is a good place to start.

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

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

Re: 8.3 325hp mechanical torque and hp curve

Reply #64 – October 19, 2014, 12:03:45 pm

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.

Re: 8.3 325hp mechanical torque and hp curve

Reply #65 – October 19, 2014, 12:39:56 pm

Quote from: squeezer – October 19, 2014, 11:32:20 am

Lots of options for mechanical engines.

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

Re: 8.3 325hp mechanical torque and hp curve

Reply #66 – October 19, 2014, 02:38:14 pm

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

Re: 8.3 325hp mechanical torque and hp curve

Reply #67 – October 19, 2014, 02:53:01 pm

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

Re: 8.3 325hp mechanical torque and hp curve

Reply #68 – October 19, 2014, 03:08:43 pm

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 !

Re: 8.3 325hp mechanical torque and hp curve

Reply #69 – October 19, 2014, 03:19:54 pm

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
V1 Series Pyrometer/Exhaust-Gas Temperature Monitor - VEI Systems
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 537.msg150063#msg150063

Re: 8.3 325hp mechanical torque and hp curve

Reply #70 – October 19, 2014, 07:07:37 pm

Quote from: krush – October 19, 2014, 12:03:45 pm

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.

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

Re: 8.3 325hp mechanical torque and hp curve

Reply #71 – October 19, 2014, 08:57:39 pm

   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.

Re: 8.3 325hp mechanical torque and hp curve

Reply #72 – October 19, 2014, 10:58:10 pm

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.

Re: 8.3 325hp mechanical torque and hp curve

Reply #73 – October 19, 2014, 11:37:44 pm

What does turning the wheel do?

And what does turning the one or two screws with male hex wrench do?

Re: 8.3 325hp mechanical torque and hp curve

Reply #74 – October 20, 2014, 12:24:57 am

Quote from: Barry & Cindy – October 19, 2014, 11:37:44 pm

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

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