Foretravel Motorhome Forums => Foretravel Tech Talk => Topic started by: rpettway on October 24, 2013, 03:02:15 pm
Title: 6V92TA DDEC Overheating
Post by: rpettway on October 24, 2013, 03:02:15 pm
I have been looking at a U300 GV with the 6V92TA DDEC engine. I was doing a lot of research on this forum and others. I've noticed there have been several discussions IRT these engines running hot. I found an interesting article online that addresses this. Although this specific forum is talking about the 6V92 in marine applications, I would think that the logic might hold true for the same engines in MHs. I also saw an old post where John Twork, mentioned this same thing IRT his Cummins. I'm sure this has already been discussed somewhere in this forum, but I didn't see it ....... yet. Anyway, I found it very informative and hope that it might help someone else.
RPMs by themselves are not bad. All things considered I'd rather have 400HP out of the engines at 2000 RPM than at 1500 RPM, because to get the HP out at the lower RPMs requires more torque to be developed, which is harder on the engines.
The paradox with diesels is that at lower RPMs you get little airflow and boost, and the consequence of this is that they run hotter combustion chamber temperatures.
That spells trouble.
By running at a higher RPM you increase the AIRFLOW through the engine. Remember folks, the air pumped is more-or-less controlled by the RPM - the more times the piston comes down in a unit of time, the more air is blown through the cylinder. Airflow is GOOD, as it controls EGTs, valve and seat temperatures, and piston crown temperatures. The controlling factor of course is that as RPMs increase reciprocating loads increase, but so long as you remain within design limits on RPM you're ok there.
In 625HP DDEC trim, the 6V92 is WAY beyond its output power design limits. I would not own those engines at that level of tune, because I'd be scared to death of the overhaul monster showing up every 500-1000 hours, with possible catastrophic failures in the middle, and that's if I treat them nicely!
If you HAVE those engines, the way to get out of that box is to depitch the props by 2" or more. This will drop the output demand significantly and allow the engines to breathe. You will run a higher RPM for a given cruise, but if you're ok with the speed you develop at that RPM, and keep cruise RPMs to no more than 1950 or so or even 2000 I'd be happy with this.
I would consider pyrometers MANDATORY on those engines in order to detect incipient problems before they burn huge holes in your pocketbook. If you have 'em, you'll notice that the EGTs go down significantly for the same speed if you depitch the props and run a higher RPM. The reason for this is the increased airflow through the motor.
The 6V92 industrial engine's maximum CONTINUOUS RPM level is specified at 2100. Now granted, this is at far lower power outputs, but the point holds - there's nothing wrong with the RPMs provided you're not loading the engines too heavily.
A common fallacy is that you can compensate for overpropping or too-high output by just throttling back. This is only true up to a point. The problem with throttling back is that you're demanding the same output but doing so at a lower RPM, which means you're demanding more torque from the motor (since HP is torque over distance per unit of time, and distance covered by a unit of time is controlled by RPM.) High torque output from low displacement engines at low RPMs can only be achieved with the byproduct of creating a LOT of heat due to fewer "breathing" cycles (which cool things.)
Drop the pitch and run the RPMs up a bit. Your engines will be happier and live longer.
Title: Re: 6V92TA DDEC Overheating
Post by: Brad Metzger (RIP) on October 24, 2013, 05:01:27 pm
My first coach was a 1989 , U-300 and 6V-92 . I ran that thing hard on a regular basis . Not one time was there a hint of over heating .Seams like it wanted to run hard as it got better and better . It had the best sound I ever heard coming from a diesel . If it would have had a lot more horse power I probably would still have it as a second coach . I kept it for two years after I bought our third coach for about a year , but finally broke down and sold it . I had happy times with that coach . Always took it to dirt race tracks as I am a Sprint Car Race fan .Got some pressure from my DW as we don't need two coaches etc etc . Oh well , life is short , take a deep breath and smile . Brad Metzger
Title: Re: 6V92TA DDEC Overheating
Post by: rpettway on October 24, 2013, 05:14:51 pm
Dave, do you or anyone else know of anyone on here that has modified their 6V92 to say 400hp? Could the Allison HT 746 ATEC transmission handle that much hp?
Title: Re: 6V92TA DDEC Overheating
Post by: Pierce & Gaylie Stewart on October 24, 2013, 05:34:54 pm
Rory,
The engine sleeps at 350hp. 525/535hp is more realistic max for these engines in a boat where cooling is much easier but will drop the TBO down a thousand hours or so. Still, they usually go through a couple sets of turbos (usually two turbos on each engine) before the engine needs rebuilding. Good video on youtube showing a fire dept ladder truck 6V-92TA pulling 515hp on the dyno after an overhaul: Detroit Diesel 500Hp 6V92TA DDEC3 Titan Fire Truck Engine on the Dyno Part1 (http://www.youtube.com/watch?v=3xy527eJ4Jw#) Single turbo too!
The horsepower is limited in our U280/U300s by the radiator placement and size regardless of engine brand. Most of the serious problems that U300 owners have is related to the drive belt used to spin the hydraulic pump that drives the hydraulic radiator fan motors. Foretravel recommended the wrong belt (6 rib) and really never took the time necessary to carefully align the pump mounting bracket, tensioner and the motor itself. Not only should they have have 8 grooves on the belt, but the tensioner can't be at a different angle or pointed in a different direction or the belt will ride on a pulley edge and will fail before it's time.
So here is the scenario. The belt is out of alignment, frays and breaks. The driver does not see the temp going up and does not see the warning lights because they are blocked by the steering wheel for many drivers. The first clue he has is the DDEC automatically reduces power for 30 seconds or so allowing the driver to get to the side of the road before it shuts the engine down before it can harm itself. But the driver is not in a good location so he or she decides to hit the computer override button and drive it further. This repeats itself until the engine is severely damaged. A U300 lost it's belt in a uphill tunnel and rather than turning on the four way flashers, the driver roasted the engine finding a good place to park it. The 6V-92TA is an inframe rebuildable engine but not if the heads are cracked and the block has overheated so much it's dimensions have been distorted.
And for the tensioner: Many posts describe a bad tensioner idler wheel jumping up and down at idle. Mine did this but in taking a careful look, I realized the wheel was at an angle and causing the belt to try and move to the side several times a second. As it moves to the side, it forces the wheel down until it the belt snaps back to a more normal position. Once I shimmed the tensioner to the correct angle (it was off just over 3 degrees), it was as smooth as glass. When I had it off, I spun it to make sure the bearing was not worn or dry, forced a little oil into it and stuck it back on. That was 30K ago.
So, if the CORRECT BELT is mounted and riding IN THE CENTER of the tensioner idler pulley and all the angles match, there won't be a problem. Otherwise, spend an hour moving things until they line up the way they were designed to be. This should be checked if any belt wear is seen.
And finally, I slow down, gear down and don't let it get above 200 degrees on long grades in the summer.
Pierce
Title: Re: 6V92TA DDEC Overheating
Post by: Pierce & Gaylie Stewart on October 24, 2013, 06:21:24 pm
Dave,
The YouTube 517hp engine was a DDEC III. I think our Detroits in Foretravels are all DDEC II engines. The II will have a rectangular 12 pin plug under the dash where it meets the driver's outside wall. DDEC II also has the 4" thick computer mounted on the top of the engine with 5 plugs, all on the passenger's side with a fuel connection on the opposite side used to cool it. DDEC I engine computers are 2" inches thick and have a round 9 pin plug under the dash. Adding HP should be no problem II vs III.
The 6V-92TA engine is 9 liters or 552 cubic inches. Even built as robust as it is, one HP per cubic inch absolute max is about all anyone can expect and have it live a reasonable time.
Dave, I think aux radiators in the nose would be the only way to add more HP. Easy to mount but getting the coolant up front would be more of a challenge.
Pierce
Title: Re: 6V92TA DDEC Overheating
Post by: rpettway on October 24, 2013, 11:49:40 pm
Dave,
It is a side radiator. Thanks for all of the great info.
Title: Re: 6V92TA DDEC Overheating
Post by: coastprt on October 25, 2013, 12:27:28 pm
Rory,
After checking, I realized I had the same problem with the hydraulic fan pump belt tensioner on my 93 U300 as Pierce described. I used a washer and a magnetic angle finder to realign it using the same procedure he brilliantly recommended in his prior posts on the subject. Rather than trying to replace the tensioner which was still good, he figured out that the problem was in the alignment of it which caused the the situation. The prior owner had replaced the fan pump, both fan motor seals, and hoses in 2007, but used a 6 rib belt which is not the proper belt for this application and I noticed was fraying and bouncing around too much.
I realigned the tensioner and replaced the belt with an 8 rib one and now it is operating very smoothly. I check it periodically and so far the new 8 rib belt looks good. An easy inexpensive DIY fix to a potential costly problem. Thanks Pierce.
If you're Gulfport, look me up and I will be glad to show you my U300 and take you for a ride in it. My 36' 93 U300 with the DD6v92/ 350HP has plenty enough power for me, a great sound to it and I enjoy it a little more each time I get to drive it!
Jerry aka Murph
Title: Re: 6V92TA DDEC Overheating
Post by: Pierce & Gaylie Stewart on October 25, 2013, 01:07:10 pm
Thanks Jerry! Might take you up on the visit. You copied what I did exactly. The big, heavy tensioner and pump mount is also a big part of the key if the belt doesn't center on the tensioner idler. It has four bolts into the block (hard to see without a small mirror) that can be loosened and the mount moved fore and aft. Moving the mount is the only way to center the belt on the idler if it is off to one side. A round file could be used to elongate the four bolt mounting holes if it won't move far enough. The hydraulic pump also has either 2 or 4 bolts ON THE PULLEY keeping the pulley in a fixed position. Loosen these and the pulley can be moved on the shaft to align it with the crank pulley after the main mounting plate has been moved.
And as far as the 6 groove belt goes, our Toyota RAV4 has a 7 groove serpentine belt to just run the small alternator, AC and water pump. The big hydraulic fan motors on the U300 must use at least 30 horsepower requiring a hefty belt to do the job over a long period. I did call a bus conversion company as well as contacting a Gates Corp. belt rep at the factory. They both recommended fitting an 8 groove belt to match the number of grooves on the crank and hydraulic pump pulley.
Pierce
Title: Re: 6V92TA DDEC Overheating
Post by: rpettway on October 25, 2013, 04:20:06 pm
Great information Jerry and Pierce. I hope to be working on my own sometime in the very near future. I can't wait to get started. I would also love to try that, mounting a radiator up in the nose as you have mentioned Pierce. Do you know if anyone has actually done that? I have seen that mentioned a couple of times now. Both times may have been by you, but I don't recall. Jerry, I will definitely give you a shout the next time I'm down in Gulfport.
Title: Re: 6V92TA DDEC Overheating
Post by: Dave Cobb on October 25, 2013, 05:08:09 pm
Kent Speers added one to his U225 that I bought. It was easy for him to do. He just tapped into the heater core hoses, and added a valve to shut off in the winter. Think he got it off ebay, small racing unit mounted near the AC condenser.
Title: Re: 6V92TA DDEC Overheating
Post by: D.J. Osborn on October 25, 2013, 05:28:52 pm
After checking, I realized I had the same problem with the hydraulic fan pump belt tensioner on my 93 U300 as Pierce described. I used a washer and a magnetic angle finder to realign it using the same procedure he brilliantly recommended in his prior posts on the subject. Rather than trying to replace the tensioner which was still good, he figured out that the problem was in the alignment of it which caused the the situation. The prior owner had replaced the fan pump, both fan motor seals, and hoses in 2007, but used a 6 rib belt which is not the proper belt for this application and I noticed was fraying and bouncing around too much.
I realigned the tensioner and replaced the belt with an 8 rib one and now it is operating very smoothly. I check it periodically and so far the new 8 rib belt looks good. An easy inexpensive DIY fix to a potential costly problem. Thanks Pierce.
If you're Gulfport, look me up and I will be glad to show you my U300 and take you for a ride in it. My 36' 93 U300 with the DD6v92/ 350HP has plenty enough power for me, a great sound to it and I enjoy it a little more each time I get to drive it!
Jerry aka Murph
I've always liked the sound of the two-stroke Detroits, and it sure would be fun to see and hear yours!
Title: Re: 6V92TA DDEC Overheating
Post by: coastprt on October 25, 2013, 08:55:37 pm
I've always liked the sound of the two-stroke Detroits, and it sure would be fun to see and hear yours!
Your welcome anytime Rory and David. Bill Chaplin is due to roll through here sometime between late November and early December. I look forward to seeing and hearing his U300 also. The weather here is really nice this time of year with cool temps and low humidity. http://www.facebook.com/MississippiGulfCoast/photos_stream (http://www.facebook.com/MississippiGulfCoast/photos_stream) Also, fresh Gulf seafood and ice cold beer make for a great combination! b^.^d White Cap Seafood Restaurant Menu (http://www.urbanspoon.com/cities/159-gulfport/restaurants/1471779-white-cap-seafood-restaurant/menu)
Jerry aka Murph
Title: Re: 6V92TA DDEC Overheating
Post by: rpettway on October 25, 2013, 08:59:13 pm
I can't wait to get back home Jerry. Every time I go home (Slidell) to see family, my first stop is not to see my sister or my mom, but to get a shrimp poboy. They are more than welcome to join me or meet me, but they understand the priority.
Title: Re: 6V92TA DDEC Overheating
Post by: Pierce & Gaylie Stewart on October 25, 2013, 09:37:03 pm
Great information Jerry and Pierce. I hope to be working on my own sometime in the very near future. I can't wait to get started. I would also love to try that, mounting a radiator up in the nose as you have mentioned Pierce. Do you know if anyone has actually done that? I have seen that mentioned a couple of times now. Both times may have been by you, but I don't recall. Jerry, I will definitely give you a shout the next time I'm down in Gulfport.
Kent used his front heater plumbing to move the coolant and then mounted a couple radiators up front in his U225. He can tell you how effective it was. When I get some time, it would be fun to figure out how to bring a couple of 1 1/2" or 2" pipes from the rear to the front. There is enough room above the propane tank and the storage compartment would not be a challenge but don't know about the short distance between the floor and the water tank. With that done, the hydraulic pump could be removed and electric fans installed in the rear and front. If you did it yourself, the cost would be a fraction of what a replacement radiator would be plus gain 25-30 horsepower. As it is, I don't think there is an affordable electric fan(s) that can move as much air as the hydraulic setup does.
Pierce
Title: Re: 6V92TA DDEC Overheating
Post by: Bill Chaplin on October 26, 2013, 07:54:51 am
Check with Kent and Dave Cobb as to how effective that was.
Title: Re: 6V92TA DDEC Overheating
Post by: Dave Cobb on October 26, 2013, 09:06:26 am
Kent might have a different take on his repair.
But my take was the single unit mounted behind the AC condenser was in "blocked" air, that was being effected by the condenser. Plus there is really no exit for air from the top of the Grand Villa style nose body shape. If I were to try to improve things, I would suggest a lower location more inline with the grill openings, or at least not behind the condenser.
The bigger thing for the rear radiator model U225 was keeping the front of the CAC clean. It tended to get dirty very quickly. My first cleaning revealed to me that the fan blades were white, not black. So that became my indicator of when to rinse. Using a Hudson sprayer to reach back and around places worked great. Using Simple Green Extreme for aluminum worked great, with a hose spray rinse.
Last thing was to realize I had a good flat land coach per Bob in CA, and not Dave M's coach's power under my right foot.
Title: Re: 6V92TA DDEC Overheating
Post by: D.J. Osborn on October 26, 2013, 09:43:43 am
Your welcome anytime Rory and David. Bill Chaplin is due to roll through here sometime between late November and early December. I look forward to seeing and hearing his U300 also. The weather here is really nice this time of year with cool temps and low humidity. http://www.facebook.com/MississippiGulfCoast/photos_stream (http://www.facebook.com/MississippiGulfCoast/photos_stream) Also, fresh Gulf seafood and ice cold beer make for a great combination! b^.^d White Cap Seafood Restaurant Menu (http://www.urbanspoon.com/cities/159-gulfport/restaurants/1471779-white-cap-seafood-restaurant/menu)
Jerry aka Murph
Thanks for the open invitation. It sure is tempting! That area of the Gulf is beautiful and we love great seafood. It's just a shame that pesky little things like jobs keep us from taking advantage of it right now. Retirement, come quickly!!
Title: Re: 6V92TA DDEC Overheating
Post by: RRadio on October 26, 2013, 03:22:29 pm
If I had a side radiator model I'd replace the huge muffler with a straight pipe, or a resonator, and mount the auxiliary radiator on the other side of the engine. I'd cut a grille for the cold air to enter and duct the hot air out the bottom of the coach. I'd install a second alternator that would power the electric fans only. It would not be connected to the coach's electric system at all, only the radiator fans. Then I'd get rid of the failure prone hydraulic fans and belt driven pump and attempt to install a direct drive power steering pump like the rear radiator coaches have... or just sell the side radiator coach and buy a rear radiator coach and pocket the leftover $10,000-20,000 price difference! :) ...Let me think for a moment, uhmmm, yeah, I'll take that second option for sure.
Title: Re: 6V92TA DDEC Overheating
Post by: Pierce & Gaylie Stewart on October 26, 2013, 04:55:01 pm
Scott,
Your idea has good potential. There is plenty of room on the driver's side to mount a radiator without getting close to the muffler. A heat shield might be needed but that's about it. The OEM muffler has a 5" in/out and has a nice sound to it. A straight pipe or resonator replacement would be very noisy and do nothing for power. The Jake would then become unusable in any populated area. With that additional radiator, electric fans could be used on both sides and your idea of a second alternator is good and could be used for the engine batteries as well. Perhaps just replacing the hydraulic pump with it using the same belt/tensioner/mount with only a grooved pulley needed on the alternator. The fans could just blow the air towards the inside like the stock fans do on the other side. No need for ducting. The cost for the alternator would be only $100 or so if you did it yourself. An custom aluminum radiator could be ordered that would not need as much support as the OEM unit or a truck radiator could be used. Would want a stock grill like on the other side so it would not look too Joadish. All in all, a good idea worth looking at but would need a bit of engineering to support the radiator securely.
The rear radiator models are not 102" wide and the 6V-92TA is derated down to 300hp.
With proper maintenance, the hydraulic pump/motor is pretty reliable but it would be nice to have it out of there plus extra horsepower and better mileage.
Title: Re: 6V92TA DDEC Overheating
Post by: RRadio on October 26, 2013, 07:32:21 pm
Getting rid of the huge muffler would probably cool down the engine bay noticeably and lose a lot of weight. The turbocharger creates a huge exhaust restriction and I presume it muffles the engine somewhat. I suspect a straight pipe wouldn't be too noisy but I'd try it and then replace it with a resonator if noise was an issue. I have a retarder instead of a Jake Brake on my coach so I wasn't considering local Jake Brake ordinances. I think getting rid of the muffler would allow plenty of extra clearance, which I would want near the radiator / fans / duct work. My coach has a rear radiator so I would definitely duct the hot air out the bottom of the coach so it wouldn't go through the rear radiator. I think an automobile alternator would be able to power the electric radiator fans. I doubt a truck alternator would be required. Automobile alternators are powerful on today's cars. I don't want a 102" wide coach. The chassis is the same width. All they did was make the body hang out beyond the wheels, which looks ridiculous to me. They wasted the extra 6" in the hallway instead of putting it in the bathroom where it would be a benefit. The 102" wide coaches cost about twice as much as the earlier coaches and there's no way they're worth it. The wisest course of action is to buy the rear radiator coach and immediately replace the fiberglass radiator fan with a nylon fan so it won't explode and destroy the radiator, then pocket the $10,000-20,000 you saved. Stewart & Stevenson, or any other Detroit Diesel service center, can plug their hand held computer into the DDEC and tell the 6V92TA that it's 350, 450, or any horsepower you want up to about 550 I'm told. They told me it would cost as little as $50 and only take a few minutes. No need to change the injectors or the turbocharger. I considered it but didn't do it because I wasn't completely sure the Allison transmission was rated for the extra power. Stewart & Stevenson's Allison transmission shop said it would be okay, but I don't really need any more power. I already pass 600 horsepower coaches pulling toads up steep grades, mainly because they weigh twice as much as my coach. If I ever want more power I'll investigate the maximum power the Allison transmission can handle. I know I can add two more radiators to handle the extra heat. I doubt I'll ever do any of these modifications though. I'm very satisfied with my coach the way it is. The longer I own it and the more I work on it the more convinced I am that I stumbled upon the exact perfect coach for me. When I first bought it I had no idea what I was doing, only knowing what I'd read on this forum and what a few friends had told me. If my coach burned down or got stolen I'd go find another one exactly like it ...but without the pink drapes next time hopefully :)
Title: Re: 6V92TA DDEC Overheating
Post by: John Haygarth on October 26, 2013, 07:59:29 pm
Pink Drapes Scott???? just what I have been looking for :P :P When I did the muffler out thing almost 2 yrs ago the first thing I noticed was the huge reduction in engine compartment heat. It was "night and day difference" and at night our bed was not hot like it usually was after a long drive. The pyrometer on the Banks also told me the manifold temp was way less than before the mod'. So for those 2 things alone it was worth it. The bonus was it DID make a difference to power and climbing ability. I did not go for the fancy Aero one just a regular Fleetguard and the sound is nice. John H
Title: Re: 6V92TA DDEC Overheating
Post by: Tim Fiedler on October 26, 2013, 08:07:24 pm
Scott, great to hear after your early challenges. A great attitude about face :-)
Title: Re: 6V92TA DDEC Overheating
Post by: Chuck Pearson on October 26, 2013, 09:36:23 pm
Good suggestions, especially the resonator as long as you don't have a Jake as it'll make it legally unusable in a lot of places where you really need it, like those little towns right at the bottom of a 7% grade. The ones with a tight curve right as you enter town.
If your 300 hp Detroit is overheating under normal use then there's a problem with it. Could be the powerplant, could be the driver. I've never seen the temp on 300 Cummins rise over 190, dead of summer, loaded and pulling a light toad. That tells me 300 hp gets the job done, question is does it do it in the style you want. Long 7-8% pulls are at 32-40 mph max, rpms near 2K. It will pull like this all day long, singing a sweet song and never breaking a sweat. As far as more speed up hills, calls for a 400+ hp engine and away you go. You'll pay in fuel though. No reason a Detroit in good shape shouldn't do at least as well, and some say better, without overheating.
Title: Re: 6V92TA DDEC Overheating
Post by: RRadio on October 26, 2013, 10:00:47 pm
...wait until a Harley Davidson is right by your tailpipe and hit the Jake Brake ...preferably in a tunnel :P
Title: Re: 6V92TA DDEC Overheating
Post by: Chuck Pearson on October 26, 2013, 11:28:30 pm
For sure, If you have a Jake Brake setup, it does not matter if you have the best muffler or a straight pipe, the use of the exhaust brake is forbidden,
Guess I was talking from a practical standpoint, believe Kent said you couldn't hear his J. Brake due to muffler. Don't think this would be the case with straight pipe.
Title: Re: 6V92TA DDEC Overheating
Post by: RRadio on October 27, 2013, 12:23:08 pm
Hahahaha! Dave is my hero! :)) I only bought a Foretravel because I've always wanted a two cycle Detroit Diesel. It's the ultimate engine. I've never liked any diesel engine except the two cycle Detroit. I love the sound and the power. It's so drastically different than today's Cummins powered coaches. I like to stand out from the crowd. Have you noticed today's Cummins coaches have that cheap sounding little high speed gear reduction starter on them but the Detroit has cool sounding full size starter motor... and then when it fires up everyone looks over at me and sometimes they ask if I've got it on high idle or something. A guy asked me if I had a 12 or 16 cylinder engine the other day. It's kinda like when I start up my 1965 Chevrolet with the big direct drive starter motor and straight through exhaust and everyone turns around to see what car made that cool sound.
Title: Re: 6V92TA DDEC Overheating
Post by: coastprt on October 27, 2013, 01:03:45 pm
Here's a couple of videos for all the 2cycle detroit lovers out here especially for Pierce and any any other firemen on the forum. It's music to my ears! Enyoy! b^.^d
Also would get rid of that muffler, go with the resonator, free up the engine, never ran a 6V-92, but the 8V-92 at 600+ hp loved the resonator. Running with a straight pipe is way too harsh, just adding the resonator cuts the harshness way back to a useable non complaining level. As mentioned the reduced heat, both engine compartment and engine exhaust temp. It is a win win.
Dave, Back when resonators were first being discussed on the Forum, the subject of a resonator on a 6V92 came up and I remember that the advice was that it would be way too loud. I understand for you that's probably not true. What's your estimate of what the "average" person would think?
Title: Re: 6V92TA DDEC Overheating
Post by: RRadio on October 27, 2013, 03:24:19 pm
Since we're way off topic I'd like to take this opportunity to point out that my 6V92TA DDEC doesn't experience any overheating, even climbing steep Rocky Mountain grades at high altitude. My radiator is less than a year old though, and I presume the average coach this age has a much older radiator. I didn't experience any overheating with the 23 year old radiator even climbing steep grades in the Appalachian Mountains. I always watch the temperature gauge as I climb steep grades... Now that we're back on topic briefly, has anyone else noticed that the turbocharger on the 6V92TA really screams at high altitude? I presume the thinner air at high altitude allows the turbine to hit a much higher rpm than it does in denser air at sea level. Normally I can't even hear the turbocharger at sea level. Also I noticed I get a little puff of black smoke out the tailpipe for a moment when I take off from a standing stop at high altitude. After a second or two the turbocharger spins up to speed and there's no more smoke. I normally never see any black smoke at sea level, even when I mash the accelerator from a standing stop. I don't notice any power loss from sea level to 10,000' elevation. I'm at 7,000' currently in Santa Fe NM. I love the multistage turbo/supercharged engine, though I admit I never considered high altitude use when I bought the coach. It's just one more cool thing I discovered after I bought it. My previous experience with a diesel engine on high altitude climbs was 25 mph in the slow lane at 10,000' but my 6V92TA is way more advanced than that other diesel, which was a Ford... still can't believe I drove a Ford, hopefully nobody saw me... it definitely WASN'T mine! :))
Title: Re: 6V92TA DDEC Overheating
Post by: Pierce & Gaylie Stewart on October 27, 2013, 10:58:17 pm
Dave,
Have the pump below the alternator on the passenger's side. Probably about the same spot as yours. Was your stock muffler a five incher on your larger Detroit? Wonder if the 5 inch muffler works on ours but would be restrictive on the 25% bigger displacement engine you had?
Jerry,
I can tell right away that is not a 350hp engine. It left the stop sign like a rocket. Would think it was turned up to 450hp or more. Our 8V-71s had 285hp, no turbo and a 4 speed plus CL manual trans. The automatic keeps the boost up when it shifts. Impressed with that fire truck. Probably has about 5000 lbs of water on board too.
Scott,
Your 300hp engine does not have the same cooling requirement as the 350hp engine. Ours does not overheat but on long grades with high outside temps in summer, I have to back off and gear down to keep it no higher than 200 degrees. Santa Fe is 7000 feet or higher depending where you are in town and without a wastegate turbo system, the horsepower and cooling requirement are about 75 percent of what they are at sea level. Yes, they do leave a little black smoke taking off at altitude but nothing like a mechanical diesel. With a waste gate, you can keep full horsepower to over 7000 feet. The point where the boost starts to drop is called the "critical altitude" and the power starts to drop off above this altitude. But we don't have a waste gate on ours so we start to lose HP as soon as we leave sea level. Assuming you are at 7500 feet with your 300hp Detroit in Santa Fe, your radiator only has to cool 225 horsepower. Plus, the temperature lapse rate will drop the temperature 3.5 degrees for every thousand feet above sea level so the ambient won't be a as much of a challenge as is would in Las Vegas. I never had to have AC on any home in Santa Fe but Albuquerque is a different story.
Geared starters save weight, never a bad thing, especially when you have to R&R one.
Would like to hear from anyone who has had their DDEC reprogrammed for more HP.
Pierce
Title: Re: 6V92TA DDEC Overheating
Post by: JohnFitz on October 27, 2013, 11:43:37 pm
When I first bought our coach in 2001, I took it into DD for service plus a dyno test (it's a rear radiator 300 hp 6V92). Without me even asking the tech told me not to think about increasing the HP as it wouldn't be allowed by DD. He told me the change goes through DD's computer system which would dis-allow it. I have no idea if he was telling me a line or not. He did tell me the way to drive it is to floor the pedal and let the DDEC and ATEC decide on shifting. I didn't know then but know now that the rear radiator has all it can handle. And because the 350hp 6V92's of subsequent years needed to have the 700 series transmissions it make me think my 648 might be at it's limit too. I concluded if I want more HP, I need to buy another coach.
I did have an overheating problem with my coach but I seems to be unique to my coach and have never figured out why. Over the years I've talked with a lot of U300 owners (with rear radiator 300 HP engines) and none ever seem to have problems I've had. I've replaced the radiator, water pump, and thermostats- all to no avail. I verified the fan speed, pulled the blower to inspect the intercooler for blockage and even added a turbo and exhaust blanket. After years of using a misting system on the radiator, I added a second radiator on the drivers side using electric fans (75 amps total). In the most severe conditions the temp will still get up to 210 -which is right at the max operating limit (as defined by DD). Others have mention the driver as a cause, but with the DDEC, there's no such thing as over fueling it and the ATEC won't let you lug it. On 6%+ grades, its running at about 2100 rpm at about 37 mph (in I think 3rd gear?, maybe 2nd?) but the mister is no longer required. I removed the battery isolator and have the fans on the house battery. When I need full power (up a grade) I make sure the boost switch is off. I figure I'll remove alternator HP burden going up hill and then turn the boost switch on when HP isn't needed on the downhill.
Title: Re: 6V92TA DDEC Overheating
Post by: Pierce & Gaylie Stewart on October 28, 2013, 12:36:57 am
They should be able to reprogram the DDEC II but you would need 5234775 injectors ($200 plus each) plus a different turbo housing with an A/R (area to radius) ratio of 1.23 (from 1.08). At least $1500 in parts. Or could buy the eBay 6V-92TA 400hp Seagraves fire truck engine ($1500) with anti-freeze in the oil and use the parts or fix it.
But then it would overheat with the rear radiator.
Pierce
Title: Re: 6V92TA DDEC Overheating
Post by: Pierce & Gaylie Stewart on October 28, 2013, 12:55:05 am
John, do you have a 600 series transmission that locks up? Lock up drops the trans temp a lot and with the trans/engine heat exchanger, it takes a fairly decent thermal load off the engine too. Lock up is like having 50-75hp more.
I can really see it in city driving with a lot of first and second gear work. Trans temp goes up in a hurry when I'm out of lock up.
I have turned on the front dash heater to cool it on occasion.
Pierce
Title: Re: 6V92TA DDEC Overheating
Post by: Pierce & Gaylie Stewart on October 28, 2013, 01:17:18 am
John,
Read your post again. 2100 rpm and 37 mph is in second gear lockup in ours. Has shifted twice so it seems like third but is second gear. Third is good to 57 mph and fourth to 82 mph.
Low tire pressure will cause the engine to work harder, run hotter.
Pierce
Title: Re: 6V92TA DDEC Overheating
Post by: JohnFitz on October 28, 2013, 08:28:13 am
John, do you have a 600 series transmission that locks up? Lock up drops the trans temp a lot and with the trans/engine heat exchanger, it takes a fairly decent thermal load off the engine too. Lock up is like having 50-75hp more.
I can really see it in city driving with a lot of first and second gear work. Trans temp goes up in a hurry when I'm out of lock up.
I have turned on the front dash heater to cool it on occasion.
Pierce
Yes, it has the lockup (3rd and 4th). I did put in a large (24" x 23") oil to air cooler for the transmission but it didn't do too much. Put it in just before the stock heat exchanger to give the engine the coolest transmission oil. Later, when I installed the 2nd radiator, I had to removed it because I just couldn't fit both in the same space.
I used to run the dash heater too before I installed the misting system - but I could never really tell the difference with it on - there's just so much heat to reject. That was also when I was only using the OEM temp gauge. I replaced it with a digital which was better, but I now have a VMS unit and it's a good 8 degrees cooler than digital dash gauge. So my problem was never as bad as I originally thought but numbers I posted above (210) are with the VMS. For my vintage engine there is no shutdown for engine overtemp, but there is a fault code list for overtemp which I have never had trigger on my engine.
Title: Re: 6V92TA DDEC Overheating
Post by: JohnFitz on October 28, 2013, 08:30:15 am
Read your post again. 2100 rpm and 37 mph is in second gear lockup in ours. Has shifted twice so it seems like third but is second gear. Third is good to 57 mph and fourth to 82 mph.
Low tire pressure will cause the engine to work harder, run hotter.
Pierce
I do pressure checks on tires before each day's run - I run at least 10 psi over placard - 90-100psi (placard is 80 psi).
Title: Re: 6V92TA DDEC Overheating
Post by: Pierce & Gaylie Stewart on October 28, 2013, 10:20:22 am
Dave,
I remember in the old days, ALL Mexican buses were Detroits, either with a GM sidewinder setup or fore and aft like Dina, Solex. The latter always just had the two exhausts go straight down (looked like 4") and then made a 90 out the back on each side w/o muffler. They did sound a bit like they had a "cam" at idle but above that, it was like a NASCAR green flag start. U.S. buses were almost all Detroits but had mufflers.
And speaking of exhaust, has anyone noticed the difference between European truck exhausts and those in the U.S.? They run all truck pipes down toward the ground. Must figure the particulates will settle faster but you have to roll up the windows and put the air on recirculate to avoid breathing it.
John,
My knowledge is microscopic compared to Fire Department, bus company mechanics. They could easily have a tip that might solve your problem and are usually really friendly. One other thing, have you ever checked for products of combustion in the cooling system? I bought a 3.4 Jag sedan with a new 327 chevy in it. The owner could never keep it cool and had replaced the radiator and tried several other fixes after the engine conversion but to no avail. The day I bought it, I tried torquing the heads and found they were well below specs. After tightening them, I never had a problem and it ran cool as a cucumber.
Pierce
Title: Re: 6V92TA DDEC Overheating
Post by: prfleming on October 28, 2013, 08:36:58 pm
I have been considering programming up my 6V92TA. It seems to me that if I go from the stock 300 HP to 400 HP, it's not like the trans and radiator will see this power all of the time, just when I lay into it, say to accelerate to merge on a freeway.
Going down the freeway with the cruise on at 70, I don't see that the engine will be putting out any more HP than it does now to maintain that same speed. The heat generated should be the same.
So, I don't see the harm in doing this. For sure, I will want to watch temps on a long grade, and if necessary, downshift and work the engine a little less till I top the hill.
Title: Re: 6V92TA DDEC Overheating
Post by: Pierce & Gaylie Stewart on October 28, 2013, 09:11:24 pm
Peter,
You probably saw the Seagraves fire department video. What a rocket! It probably had an engine like the one for sale on ebay. Would be a good deal even if you just used the turbo housing and injectors. Detroit 6V92TA Ddec 400 Horsepower Engine Motor | eBay (http://www.ebay.com/itm/Detroit-6V92TA-DDEC-400-Horsepower-Engine-Motor-/161076109773?pt=Other_Vehicle_Parts&hash=item2580e261cd&vxp=mtr) Not sure if just programming the DDEC would do it.
The 517hp ladder truck engine would be even better but would probably break the trans.
Would find someone really savvy on Detroit 2 cycles before I went too far. Sure would be nice to send some coolant up front. Perhaps down the left center and through the back of the generator compartment. If you moved the AC condenser, you could stick a wide but short aluminum radiator from the left to right grill with a couple of fans and then do the same below with the removable plates out of the way. Would have to get rid of the two hitch receivers. Mounts would be pretty easy and no body work to do or grills to install.
Probably could take some $$ home from unbelieving Monaco owners. They sure are fun.
Will follow your progress.
Pierce
Title: Re: 6V92TA DDEC Overheating
Post by: RRadio on October 28, 2013, 11:25:07 pm
My 300 horsepower rear radiator 6V92TA totally outran a new bus with a big Cummins and a tag axle without a toad today on the steep grade climbing up from Espanola to Santa Fe. The big bus was right behind me and floored it to get a run for the hill but he didn't even make it up beside me before he started losing ground and fell back about 1/8 mile by the time I cleared the top of the grade, then he flew past me on the other side of the hill course. I had my cruise control set at 60 mph just like always and didn't get any run for the hill, just let the DDEC do its thing like usual... Someone please explain to me why I need more power? ;D ...I'm not averse to paying Stewart & Stevenson $50 to turn up the power but I've driven my coach all over the country and never needed it. I honestly can't see any power loss, even at 10,000 feet.
Title: Re: 6V92TA DDEC Overheating
Post by: prfleming on October 29, 2013, 06:17:11 am
Scott:
Great story. On our last trip we were climbing up the hill coming out of Duluth going back to Minneapolis. My son down-shifted into third, and spun up the turbo to 2000 RPM just as we hit the bottom and put the pedal to the metal. We lost about 100 RPM on the hill, and held 1900, topping the hill at about 50. The Detroit sang it's song all the way. Cars passing on the left gave us a good look going by.
On your question, who needs more power...(you're missing the point)... ;) My wife asked the same thing... It's the fun and excitement of modifying something to go faster!
Title: Re: 6V92TA DDEC Overheating
Post by: RRadio on October 29, 2013, 10:08:38 pm
The new coaches get heavier and heavier every year. I'm told the new coaches are now up to 50,000-60,000 pounds, or in other words, more than twice the weight of my coach fully loaded, which it never is of course. I've never had any coach pass me climbing up a steep grade, and I've driven it all over the country in the year and a half since I've owned it. The 6V92TA is a real strong performer, which is why I bought it... that and the fact that it's the ultimate diesel engine. ;D
Title: Re: 6V92TA DDEC Overheating
Post by: RATC1956 on October 30, 2013, 02:50:59 pm
Dave, do you or anyone else know of anyone on here that has modified their 6V92 to say 400hp? Could the Allison HT 746 ATEC transmission handle that much hp?
Dave, I would not do anything to that 6V92 Detroit, that Detroit diesel does not recommend. The 6V92 is a dinosaur in today's standards, it is a 2 cycle diesel, by pumping too much fuel you are definitely going to run into overheating problems at low rpm's. Anytime you have a mechanical diesel and you're going to put more fuel to it make sure you have a pyrometer installed on the hot side of your exhaust. Any of 71 series 92 series Detroit's are noted for burning fire rings due to internal combustion chamber high temperatures. They are great reliable engine as they are. But do yourself a favor do not let any shade tree mechanic get into that governor and pump system or put oversize injectors into it. Because all you're looking for is throwing $10,000 out the window. Your new or engines of today you can squeeze a lot more horsepower out of them, at the ECUs have failsafes programmed into them to eliminate the chance of over fueling that causes overheating problems, they also are equipped with air to air cool air going into the engine, which keeps your internal engine temperatures down.
Title: Re: 6V92TA DDEC Overheating
Post by: RRadio on October 30, 2013, 09:41:17 pm
These are DDEC engines, which are electronically controlled. You have to take it to a Detroit Diesel service center such as Stewart & Stevenson and have them plug their hand held computer into the DDEC computer to raise the horsepower. There's no need to change injectors or turbocharger or anything, just pay the man the money. The only issues would be the condition and capacity of your radiator and the maximum amount of power your transmission can handle. Ask Stewart & Stevenson's Allison transmission shop before you have their Detroit Diesel shop turn up your horsepower. You'd be okay to turn a 300 up to 350 but you probably wouldn't notice much if any difference in performance. Fire engines were usually 450 horsepower, so that would probably be a reasonable horsepower to aim for, but you should already be able to outclimb any coach on steep grades if you're lightly loaded, so what's the point? The new coaches weigh twice as much as yours and get heavier every year and they've probably hit the wall at 600 horsepower now. They'd probably need over 700 horsepower to pass you climbing a steep grade... just saying
Title: Re: 6V92TA DDEC Overheating
Post by: Pierce & Gaylie Stewart on October 31, 2013, 10:12:25 am
Dave, I would not do anything to that 6V92 Detroit, that Detroit diesel does not recommend. The 6V92 is a dinosaur in today's standards, it is a 2 cycle diesel, by pumping too much fuel you are definitely going to run into overheating problems at low rpm's. Anytime you have a mechanical diesel and you're going to put more fuel to it make sure you have a pyrometer installed on the hot side of your exhaust. Any of 71 series 92 series Detroit's are noted for burning fire rings due to internal combustion chamber high temperatures. They are great reliable engine as they are. But do yourself a favor do not let any shade tree mechanic get into that governor and pump system or put oversize injectors into it. Because all you're looking for is throwing $10,000 out the window. Your new or engines of today you can squeeze a lot more horsepower out of them, at the ECUs have failsafes programmed into them to eliminate the chance of over fueling that causes overheating problems, they also are equipped with air to air cool air going into the engine, which keeps your internal engine temperatures down.
In order to require a pyrometer on a 2-cycle Detroit, you would be talking about a boat installation with an additional couple of hundred horsepower or more on a 6V-92TA. I know that some 5.9 Cummins PU owners with chipped engines see 1250 degrees on hills. We stopped adding fuel at 1100 degrees on 4 cycle diesels to stay on the safe side in the old days. Plus, they smoked a lot with too much fuel.
2 cycle diesels use a huge amount of air and it would be very unusual to see an EGT reading of above 900 degrees. They have both the big supercharger as well as a turbo plus 4 exhaust valves so the air really whistles through them. With the low exhaust temperature, they produce a different set of compounds and is probably the reason for the "Greyhound Bus Station" smell we all got used to in the 50's. The high volume of air is another reason to check the "tell tale" air cleaner restriction gauge frequently. I replaced ours with visible lines for the amount of restriction. That way, I can plan for an air cleaner change rather than waiting for the indicator to suddenly change to red.
Like Dave said, too far advanced injector timing has been the cause of piston/ring failures in the mechanical days. We had a Jaguar customer that did most of his own maintenance but ran too much advance and put holes in the pistons.