Here's one to pick your brains......

[strx7]

My corolla - (with 5SGTE) currently has a bit of an odd issue. Its got boost, comes on boost just like usual, but when it does come on boost, its like there is invisable 2 tonne trailer attached holding it back. Have checked for things like brakes sticking on, but they are all fine. Did some runs with the wideband on it, and the A/F Ratios are pretty much spot on. It doesn't appear to be missfiring (exhuast note sounds right) and its not knocking, its just lacking power. I thought I might have a boost leak, the boost guage is plumbed in to the plenum chamber, so If i had a leak it would have to be between the plenum chamber and the head, which basically means it would have to be either of the 2 manifold gaskets. Cant hear an obvious leak, and one would think it would be running pretty rich if its getting 16psi at the plenum chamber and therefore its injecting 16psi of air worth of fuel but only getting a couple of psi worth of air at the engine itself.

Did a cold compression test, remembering its got 264 degree cams in it, and had 165psi even across all 4 (which points to nothing being astray internally)

Anyone got any ideas? this one has me stumped......

[mjrstar]

I'll take the long shot theory first:
cambelt tensioner is not set correctly, as rpm increase your tensioner isn't holding tension and the cam timing goes retarded.

or: something else is retarding the sh it out of your ignition timing.

[strx7]

whatever is causing it, happens just before the end of the last run at the autocross last sunday. Will pull the front cover off and check the cam timing.

Have checked the cam timing, thanks for the suggestion, and it is exactly as I had set it when i put the engine together.

anyone else got any ideas????

[Paulio]

Out of curiosity, what type/brand of wastegate are you using?
Standard or aftermarket computer?

Comparing with someone here who has a similar issue.

Paulio

[strx7]

Haltech E6X ECU.

Wastegate was a tial style cheap and nasty, but it was having issues and i was having issues with consistant boost control, so have changed it to a genuine tial gate and my boost control is now sweet.

Boost delivery seems just like normal, just it is severly lacing in pull/power.

[cedwards]

how does it feel rolling downhill with the clutch in?
No drivetrain bearing issues?

[strx7]

how does it feel rolling downhill with the clutch in?
No drivetrain bearing issues?

Not that I can hear.

[CelicaGT8]

Cam timing?
Knock sensor?
Injector pulse?
Blocked Exhaust?

[strx7]

Cam timing?
Knock sensor?
Injector pulse?
Blocked Exhaust?

There is no knock sensor in the system. we tune with knock sensors mounted to the head and listen for knock with headphones, the ecu runs no closed loop knock control.

if there was an injector pulse issue, it should have shown on the runs we did with the wideband oxy sensor on it.

if it had a blocked exhuast, i would have thought it would have been slow to come on boost, because that is one of the things i gave some good hard thought too aswell.

I might try putting a timing light on it tomorrow at say 4000-5000rpm and just see if the timing stays on the mark or not (can lock the timing in the ecu) to elimate the RPM retard possibiity

[CelicaGT8]

can lock the timing in the ecu)

Cool, i want one.
It could be the exhaust timing,
The dizy is on the intake cam so that and the crank could be right and the exhaust off, perhaps check that...
Boost leak?

[loose_unit]

You havent accidentally set the advance limit to 0 or anything silly like that?

[Adamal]

You didn't chuck your turbo in the dryer with the rest of the laundry and accidentally shrink it, did you?

[CelicaGT8]

You havent accidentally set the advance limit to 0 or anything silly like that?

Thats a good point,
What about the fuel pressure regulator? Is it getting a good vaccume feed?

[strx7]

It was running mint for 450odd km. Did 2 good runs at the autocross all good, about 150metres from the end of the 3rd run, it felt to be lacking power, but was boosting right. so whatever has happened to it, happened during the 3rd run. Put some new plugs in it, did a compression check, changed the wastegate. Boost control is now sweet as, but it seems like its got a 2 tonne trailer on the back - and I can assure you that there isn't.

I flow tested the regulator 2 weeks ago, was working mint, fuel pressure appears to the be exactly the same as when i was flow testing it, if it was lacking pressure it should have been lean on the wideband.

[postfach]

Is the clutch all good?

[l1ttle_d3vil]

the corolla done similar to what you described on the way back from the drags, except it didn't have any boost and couldn't hear the turbo spooling. Turned out the c-clip came off the actuator arm and the wastegate was completely open.

Your symptoms sound very similar to what mine felt like - but you've got boost?

[strx7]

yip, its got upto and including a good solid 18psi, but driving the car you would't really believe it, it just doesn't feel like its boosting anywhere near that much.

[crispy'86]

Nothing silly like one of your hose joiners from the intake to the turbo are slightly leaking under boost?
Or maybe fuel pump issue.? not getting enought fuel to the engine when the higher demand for fuel comes in with full boost?
Blocked fuel filter

[strx7]

1) we wouldn't get 18psi at the plenum chamber

2) a/f ratios are sweet, indicating it not be a fuel related issue

[Bazda]

Id say blocked muffler.

I've had this happen to me twice before. And seen it on 2 other cars.

I did a conversion to a 4agte, car would boost the same, sound the same, a/f was all good, timing was good, had me stummped for a week!.
Took the exhaust system off and it was alive again. So started cutting up the ex system and found the resonator to be blocked.

My old car, it started to slowly get slower, same symptons as above, the flexi in the ex system had collapsed.

Dad had a VR4 in the garage, coulndt figure why it got slower from the time they put in cams till 1 week after. Blocked flexi.

Out at Manfield, a customers escort just wouldnt pull, we even took the carbs off to clean them out, found to be a blocked muffler.