Replaced Turbo, Now Sluggish

[GTScotT]

Ill assume thats what happens when the car pulled all fuel and had to be restarted after it hit 15psi plus.

i have this strange image in my head that after you put the turbo in, it boosted to 15psi, cut and has been a dog ever since. is this what you are trying to say?

either way, comp test time.

[Sparky206]

not at all, it was very progressive, from the start it felt like something wasnt right, certainly wasnt a situation where i floored it to redline and wondered what happened.

I've had problems with boost creep before, so im very cautious about over boosting

[aerofocker]

when you back off the throttle in a throttle boddied engine on overun the engine creates a vacume, on both the exhaust side and the inlet side so these engines can infact suck things into the engine through the exhaust,im quite sure of this,although its normaly the gtrs that do this,do a compression test. im not talking shit.

Edited March 5, 2010 by aerofocker

[GTScotT]

+1 comp test, cant stress enough.

but for a different reason

[Sparky206]

Took the cat off just then and its not blocked at all, could see straight through it all the way around, and was only minimal bits of ceramic in there which i tapped out. Took the car for a very loud run around the block and there was no improvement, still struggled to build boost and would not hold with the wastegate.

Will borrow a compression tester during the week and ill get those results.

Although there still 2 things i cant work out

1. The metal shaft + bolt that held the ceramic wheel on is still missing. There is not a chance that it made it passed the cat, so where else could it be?

2. The wastegate is not operating. Its the 2nd one I've tried and i have the same hose as i used on the old turbo connected straight to the actuator.

Cheers guys

[DirtyHands]

Took the cat off just then and its not blocked at all, could see straight through it all the way around, and was only minimal bits of ceramic in there which i tapped out. Took the car for a very loud run around the block and there was no improvement, still struggled to build boost and would not hold with the wastegate.

Will borrow a compression tester during the week and ill get those results.

Although there still 2 things i cant work out

1. The metal shaft + bolt that held the ceramic wheel on is still missing. There is not a chance that it made it passed the cat, so where else could it be?

2. The wastegate is not operating. Its the 2nd one I've tried and i have the same hose as i used on the old turbo connected straight to the actuator.

Cheers guys

not sayn anything bad against the blokes the did ya the rebuild, but are u sure the shaft my never have left the turbo?? or if the shaft was snapped into smaller pieces it may just have found its way out during travel back home..

[Sparky206]

I was the one who took the turbo off, so i saw it first hand, the shaft had sheered off flush with the seals.

Had more of a think about it, as some of the intake hoses were a bit of a squeeze to get back on, if i have a split in one post compressor wheel, would it not just be acting like a large bleed off valve, which would then give me the symptoms i have like long spooling time, hearing spooling but not seeing boost, boost struggling to build past 5psi till 5500rpm+ and my waste-gate not working?

Someone with a bit more knowledge care to tell me if im on the right track?

[GTScotT]

theres actually no shaft mate. the rear wheel and shaft is 1 piece on a ceramic item, so the shaft is also ceramic.

hope that clears it up.

[Sparky206]

Cheers, certainly does, one less thing to worry about

[Al]

It is definately possible, and has happened many times, that a blown turbo has also damaged the engine. Due to the speed the wheel is spinning, when it shatters, fragments can easily be shot back into the cylinders.

Do a comp test mate and make sure your engine is still healthy.

It is also possible that you may just have an air leak somewhere, but if you have already double/triple checked all the clamps, pipes and hoses, you need to start looking elsewhere and check the engine.

[aerofocker]

sounds like the downpipe is catching the wastegate?

[**RB2530**]

I was the one who took the turbo off, so i saw it first hand, the shaft had sheered off flush with the seals.

Had more of a think about it, as some of the intake hoses were a bit of a squeeze to get back on, if i have a split in one post compressor wheel, would it not just be acting like a large bleed off valve, which would then give me the symptoms i have like long spooling time, hearing spooling but not seeing boost, boost struggling to build past 5psi till 5500rpm+ and my waste-gate not working?

Someone with a bit more knowledge care to tell me if im on the right track?

A waste gate hose that is badly split will 'not' result in a lower boost...It will result in a 'higher' boost which is uncontrolled because the wasetgate will be closed all of the time..It is the same as disconnecting your waste gate...Don't forget the wastegate is sprung closed and is opened by boost pressure...

I still think it has something to do with your BOV...The spring in the stock BOV is quite weak and will be forced open by the boost pressure if the there is no boost pressure on the back of it to keep it closed..This will give you the symptoms you are seeing...The reason the boost still increases with rpm is that the airflow exiting the post compressor side is passing through the BOV which in itself is a restriction that will increase in pressure drop with increasing airflow...It may not necessarily be an incorrectly placed or split hose, but a problem with the BOV itself...Diaphragm split etc etc...

As a test, try connecting a boost line from the post compressor side to the BOV nipple.....or even better do the coke can trick with the BOV..ie cut a coke can open, make it flat and place it between the BOV flange on the intake and the BOV itself effectively blocking off the BOV. And remember whenever you do anything like this don't get the car on the street and give it a bootful...You should know your car well enough to detect changes without giving it WOT...

A comp test is good idea but I would expect for the severity of what you are seeing, the comp would be so bad that the engine would sound like it was a cylinder or two down...It would be extremely unlikely that the damage to each cylinder is 'even' enough to still sound ok...Each cylinder would need to have ingested similar quantity / size of debri etc etc...

As for the ECU tune...I really doubt it is the cause...The ECU is very tolerant to changes (waiting for doubters to appear). I use stock R33 GTSt ECU on RB25/30 and make 270-280rwkw with very healthy AFRs. Engine has done 70,000 kms like this...You just need to understand it properly.....

[Sparky206]

Bit of an update, had a fair crack at it over the weekend and ended up sorting it all

It ended up being 2 issues

First issue was there was a boost leak somewhere. I bit the bullet and just took all the intake hoses off again and re did them all as tight as possible. Then boost leak tested it with a air compressor and it held perfect. This sorted the car running like shit, it was smooth again but still free boosted.

Then i checked the wastegate actuator with the compressor and found that it was hardly opening at all. Ended up being the bracket it was mounted on has the arm at a too sharp angle, so that it was opposing the wastegates arc at a certain point. Changed the mounting position with a few modifications to the way it was mounted so that it was more straight on which fixed the issue.

Cheers to all that had a go at diagnosing, now just goto fix the boost creep problem the cars always had.....