8v92 475hp exhaust issue

tr206 · August 25, 2022, 04:32:29 AM

Quote from: chessie4905 on August 24, 2022, 06:13:09 PM
tap a pressure gauge after the turbo and see what it is at full throttle in 3rd. May need to run tube and gauge to rear side side window and duct tape fast and have someone watch and report.

Agreed. Only way to take the guess work out of it.

luvrbus · August 25, 2022, 05:18:20 AM

Take a IR gun read the temp at all 8 ports on the manifolds they should all be close on both sides, then read the tip of the 5 inch pipe,the 5 inch pipe is not your problem though ? how hot is getting and how long does it take to overheat, back pressure will make the 8v92 smoke terrible, another? does the engine have a bypass blower, with the IR compare the reading on dash gauge if you haven't yet by the size of the radiator you mention sounds like it is the right size for a Eagle with the 8v92,the exhaust pipe should go out the rear on a Eagle not the radiator side

TomC · August 25, 2022, 08:17:26 AM

8V-92TA is THEE hardest engine to cool (except of course if you have a 12V-71TTA). Many have put a second radiator-like Ed Van. Mainly because most of the buses came from the factory rated at 400hp. Then pump them up to 475 or 500hp and the over heating starts. Many times a 2 tow aluminum radiator will cool better than a 5 or 6 row copper/brass. Good Luck, TomC

luvrbus · August 25, 2022, 09:12:57 AM

Eagle and Prevost usually don't have a cooling problem with a 475 hp 8v92.MCI never rated a 8v92TA over 360 hp till the C with the rear mounted radiators those would run cool at 450 hp

tr206 · August 25, 2022, 06:05:25 PM

Clifford I will have to get a ir temp reader. It would get to 200 degrees 2/3's way up a mild hill in the dakota's it was about 90 plus degrees OAT (radiator mister seemed to have no cooling effects) I wouldn't let it go higher so I would pull over it took a good 5 minutes to cool to 180 I finely thought about taking the straight through muffler off that night the next day was cooler and it ran cooler 185/190 in the hills still cancel our trip and went home. Don't know what a bypass blower is? I've got a 1/8" npt weld in bung coming to plumb in a back pressure gauge it's cheap then I will know for sure or not. Like I said earlier I brought it home changed to a 5" exhaust and the oil and headed west a month later then the heating issues started. I will let everyone know what the readings are in two or three week. Thanks to all for know.

luvrbus · August 25, 2022, 07:04:38 PM

Quote from: tr206 on August 25, 2022, 06:05:25 PM
Clifford I will have to get a ir temp reader. It would get to 200 degrees 2/3's way up a mild hill in the dakota's it was about 90 plus degrees OAT (radiator mister seemed to have no cooling effects) I wouldn't let it go higher so I would pull over it took a good 5 minutes to cool to 180 I finely thought about taking the straight through muffler off that night the next day was cooler and it ran cooler 185/190 in the hills still cancel our trip and went home. Don't know what a bypass blower is? I've got a 1/8" npt weld in bung coming to plumb in a back pressure gauge it's cheap then I will know for sure or not. Like I said earlier I brought it home changed to a 5" exhaust and the oil and headed west a month later then the heating issues started. I will let everyone know what the readings are in two or three week. Thanks to all for know.

Back pressure on the 8v92 is 3.0 in mercury that is about 1.5 psi could be tough to read with a cheap gauge,those engines need to be around or above 1700 rpm when under a load to keep cool

RJ · August 25, 2022, 08:26:21 PM

Quote from: tr206 on August 25, 2022, 06:05:25 PM
I brought it home, changed to a 5" exhaust and the oil and headed west a month later then the heating issues started.

tr206

If I'm looking at your photos correctly, it appears that you have at least five, if not six, 90º elbows, plus two 45º elbows in your exhaust plumbing. Going to my charts from my days in the pool industry, you've basically got the equivalent of just under 70 FEET of straight pipe restriction in your system! I think this is a lot of your overheating issue.

If this were my Eagle, I would come straight off the turbo into a 90º "sweep ell," then down to another "sweep ell" pointed towards the rear of the coach and finally into/out of a 5" resonator with a short, straight tailpipe. Or leave the resonator out, as the turbo muffles a lot of the exhaust noise anyway. All of this should be on the curbside of the engine.

FWIW & HTH. . .

RJ

tr206 · August 26, 2022, 03:57:38 AM

Clifford thanks for the spec's. my theory is I will try 0 to 8 psi gauge if it's restricking it should show. and RJ you may be right we will see.

luvrbus · August 26, 2022, 06:30:08 AM

When you need it you never can find it,I am looking for my Detroit engineering bulletin 134 that tells you the size of pipe and the restrictions for 2- 90 bends in a exhaust system on a 8v92

robertglines1 · August 26, 2022, 08:54:04 AM

your transmission isn't running hot=extra heat? Downshifting on grade? my trans (8v92 with allison) in last coach ran 20 deg higher than engine until I got correct fluid in it. FWIW

buswarrior · August 26, 2022, 11:13:51 AM

My favorite, is that dash gauge correct?

All you have to do is breathe on the old wiring in the engine room and you can screw with the resistance...

You were in there swinging pipes around...

The wildly inaccurate behaviour of old dash gauges and their never replaced wiring have made more work for more busnuts...

Happy coaching!
Buswarrior

tr206 · August 26, 2022, 07:51:09 PM

What is the "correct" tranny fluid I am assuming whatever type of atf they put in at the rebuilder is correct not sure? As far as temp gauges there are two separate temp gauges both are close to the same readings one on the motor and one indash. I will see what the backpressure is if it to high I might just get some of that insulated stainless chimmey run it up the corner of the bedroom and run the exhaust up through it and out the top of the roof that way there is only one 90 degree rest straight and would blow the noise up too. What do you think?

buswarrior · August 27, 2022, 03:18:44 PM

The gauge on the motor can be read during your indicated hot conditions?

Everyone agrees sitting parked, but...

Nothing linear about the irregularities of a dash gauge. Real temp went up 3 degrees, dash gauge goes 15...

I had an assistant, with an IR gun, shoot the big pipe coming off the top of the engine, down through the floor access, heater needs to be calling for heat to ensure some flow, and the assistant can call out the readings and driver can compare the dash gauge "in the moment"

With some big money and big headaches on the line, you gotta be sure you really have a temp climb...

Happy coaching!
Buswarrior

tr206 · August 27, 2022, 06:49:27 PM

You are correct buswarrior. I have to get a good ir gun. I have compared the gauges on the way down as fast as I can walk back and forth while it's cooling down for what that's worth. Still gonna start with backpressure check I got to know.

Utahclaimjumper · August 28, 2022, 06:11:16 AM

The interesting part of this saga is your statement that you did not have a problem ,,,until you "fixed" the problem.. You have been on a goose chase since..>>>Dan