NNBD

guys im with a rallyteam that drives with mitsubischi EVO's and we're having a big problem with one car.....every turbo on that car dies.....all of them !
I'll try to descibe the situation and the problems.

Well, the big problem is, every turbo we put on this car...it dies. It takes just one rally to destroy its turbo's which is about 600km !
Every time the axial bearings die...we upgraded these bearings...they still die

The car ís a Mitsubischi EVO 7, its a group A car and modified where legal according to regulations. I don't know EVERYTHING exactly by heart but this is what i know.
Engine, Most engines in our cars just last 1 season...i think it was brand new before this season but it could be a used one, but at the beginning in top condition. At the moment 1 cylinder is leaking (bad compression).
The engine has group a performance cams (don't have any spec's that i know by heart)
The engine has group a pistons and rods (hi compression, 1:9 or a bit more).
Turbo is running at 1,8 - 2 bar boost, thats about..ehh 26 to 30 psi.
Turbo has a group a air inlet restrictor (38mm i believe)
Downpipe is hi flow 3" downpipe.
Exhaust is 3" front to back......completely open pipe.
Turbo is a stock EVO 7 turbo.
Stock oil feed
Stock oil return.

All our cars are about the same...all running as much mods as legal.

Then about the tune, its running on a MOTEC M800 (Like all of them do). Very clean fuel, ign and boost maps. It's running WITH ALS (anti lag system), but not as much ALS as the rest of the cars have since the turbo seems to die very very fast. ALS tuning is the same as the rest of the cars, but we limited it by shutting the throttle a bit more at idle so it has less air.
It didn't have a dumpvalve since we don't like them we like to keep as much air in the chargepipes as possible so we have a good throttle response.Exessive air is just pushed back into the air inlet filter...the turbo keeps spooling because of the ALS system. Turbo's don't like ALS but normally it should hold together for about 2500 km.
Last time we did have a dumpvalve....it still died.

We drive with 1 EVO 4, completely rebuild (it competes with, and beats world rally cars !) its running about the same tune and setup as the evo 7 and no problems at all. We have an EVO 6 that also is about the same tune...no problems there
And we have another EVO 7 thats 98% the same as the EVO 7 that kills every turbo. Same setup, about the same tune, just a little bit less turbo pressure since the girl thats driving it just went from a Group N to completely tricked out group A (thats going from about 240hp ??TQ to about 310Hp and 550TQ...yes the restrictor is a pain in the ***).

So all cars have about the same tune, about the same setup, same boost pressure except for the 2nd evo 7. All running pretty some ALS except for the one with the problems.....

What could be a problem ?? We normally log air inlet temp, air inlet pressure, exhaust temp (except for the killing evo7 since we just had to order a new thermocouple amplifier..it died), engine temp......and lots more thats not important for this problem.

We're going to fix the evo7 exhaust gas temp sensor and adding a feed oil pressure sensor. We would also like a exhaust air pressure sensor but can't find a sensor that can hold op to 900-1000 degrees celsius

All data we have now from all the cars is about the same but still one seems to eat turbo's for breakfast

what oh what could be our problem .

Blohardt

Obviously if you're losing bearings it's a coking issue, and coking occurs because of high EGT's and/or restricted oil flow. Also, pushing still burning air/fuel mixture into the exhaust manifold isn't helping any off throttle, but if you're running heavily lean you're compounding that problem. You should probably get the EGT sensor fixed, or even get one of the fancy multipoint EGT setups since it's an actual race car and you should expect reliability. Oh, and your cyl number 1, with the low compression, i'm sure that's blowing by like a ----------er at 30 psi, spewing all sorts of stuff into the crankcase. What's your PCV setup? If you recirculate the top of your catch can it can play havoc with the management by introducing mad unburned hydrocarbons into the intake stream. Bottom line, don't trust the tune, fix what's broken, and get the sensor you need working so you can diagnose the problem.

NNBD

well, why don't trust the tune, i mean, its the same tune as the other evo 7 but it has just a bit less boost.
I don't think its a coking issue. Coking is when the oil burns and degrades so it gets sticky on the bearings. These bearings just eat away....only the axial bearings. The radial bearing is just a bit damaged cause the axial bearing is damaged and we stopped on time. When the radial bearing looses it..we normally break the wheels, axles etc.

I do think its getting enough oil, i believe its the pressure difference between the turbine and compressor wheel what causes it to eat away the bearings (to much load). But how this is possible...we don't know. Its very very strange. All logged data looks the same from every car, all tunes are pretty close to each other. And well, WRC's run even more boost we tune the boost pressure regulator let it boost up to 30psi, above 5500 we let it drop since it has an air restrictor, we try not to overspool it too much.

Also, what do you exacly mean by "pushing still burning air/fuel mixture into the exhaust manifold isn't helping any off throttle" ? (its probably just my english )
Its not that we're running lean, not at all, also our AFR's are very consistant. With ALS we just retard the ignition up to -70 degrees, and add a bunch of fuel, so we get an mixture burn in our exaust manifold. This way we force the turbo to keep spooling. This is just for a very short period.

PS: Yes the engines do get worn out...well thats just part of the game. 1 season, 1 engine. mostly brand new engines from mitsu
hell we even bought brand new evo street cars and took them apart for parts....cheaper than pretty new 2nd hand

NNBD

btw, PCV valves....as far as i know we run open PCV's no catchcan...just let it ventilate in the air.

boosted_b16

is it just me or does running 26-30 psi on a mitsu 16g turbo seem high? for one thing that turbo has to be wayyyy out of efficeny range and maybe thats what is poping the turbos?

WTF

thats what i was thinking but im not expert

jeffescortlx

I bet it's a combination of over boosting and antilag.
Have you checked your feed pressure?
Sure your not getting ching chang meow 16g's?

CspecRun

Can't help with ur problem, but I'm fascinated by the cars u are describing and their setups...Some pics would be really cool(of cars and engines)...

Blohardt

I'm only suggesting checking the tune, you really can't tell how the a/f ratio is without a wideband lambda or an egt gauge, you really never know, especially when you run the motors that hard, they can change and most definitely vary from motor to motor, and the IAT's can change in a wink when you run a smaller turbo at the bleeding edge of efficency. If you want to monitor the exhaust gas pressure, why not just get a conventional MAP sensor and attach it to like a 6 ft coil of very thin copper tubing, which you can coil up and tap into the exhaust manifold. The air stack inside the tubing and the copper should dissapate the exhaust heat while still giving an accurate MAP reading, and I'm sure that can be integrated into the MOTEC. It seems like your ALS is pretty agressive, i've read that WRC cars usually use like 50 degrees btdc, and in light of the axial bearing wear, i would guess that the shaft is getting slammed pretty hard, and it could be the transition into the ALS is really punishing in this case. I would also venture a guess a pop off valve might be making the problem worse, because you're loading up the exhaust side heavily and totally unloading the intake side in the name of keeping the turbine speed up. But once again, you say you've got a perfectly working car with a more or less identical setup. I suppose clipping the turbine a little would be out of the question to reduce your backpressure a little, i would guess you need all the blade area possible with the restrictors you run and the torque produced. Just throwing a couple ideas out there.

NNBD

During testing, driving or racing...motec always logs all data (all sensors that are on the car...you name it). We check EGT, Air inlet temp, engine bay temp, engine temp, AFR, Boost reading, drive speed, and TPS reading during every service (so every 4 heats). We monitor them very closely !
I do think that the pop off valve can increase the problem, but not nessecairy since we DID run les ALS than on the other cars, and with a pop off valve we don't shove the air back into the air filter. Turbo's don't like that too much eighter. Its hard to tell what would cause more damage.......
We're also thinking of logging the turbo RPM's

The mitsu turbo is a stock turbo since it cannot be replaced due to regulations. It is legal to swap the turbine housing for a EVO 5 housing what should be an advantage (i personally don't know it exactly...it does make a difference..that was the department of someone else in the team).

Without the restrictor the turbo can do even more But well, yea with the restictor boost pressure is dropping when above 5700 rpm

about the pictures, ill add some tomorrow