MR2 Boost when hot

[thornz]

During todays trackday, I noticed that after a few fast laps, the boost was dropping from its usual pressure. Its completely standard car, and usually boosts around 8-9 psi, but after a few laps, it was dropping to aorund the 5-6psi level. What could be the cause of this? Would it just be the heat build up in the engine bay? Or is there a more serious issue behind this? Any suggestions for troubleshooting this?

[sergei]

During todays trackday, I noticed that after a few fast laps, the boost was dropping from its usual pressure. Its completely standard car, and usually boosts around 8-9 psi, but after a few laps, it was dropping to aorund the 5-6psi level. What could be the cause of this? Would it just be the heat build up in the engine bay? Or is there a more serious issue behind this? Any suggestions for troubleshooting this?

I assume this is 3SGTE?
do you get CEL when that happens?
I assume it is in limp mode, thus "bleed" VSV is disabled.
Or perhaps something simple as intercooler is not up to task and inlet tempt is too high hence limp mode.

[thornz]

Im assuming CEL is a warning light?? Nothing came up on the dash, and yes its a 3sgte. Hmmm, limp mode would sound correct, as when the car isnt up to temp, its boosts to the same level.

[Twolitre]

Jumper TE1 and E1 of the diagnostic terminals in the engine bay and if you can't decipher the codes then tell us how many times the check engine light flashes inc long pauses.
What mods have you done?

[iOnic]

There won't be any stored CEL codes if the CEL isn't on. That and it won't be in limp mode unless he hits boost cut (he'd definitely know about that and he certainly wouldn't hit boost cut on a 100% factory engine @ 9psi)

Sounds like heatsoak on the stock intercooler.

[thornz]

There won't be any stored CEL codes if the CEL isn't on. That and it won't be in limp mode unless he hits boost cut (he'd definitely know about that and he certainly wouldn't hit boost cut on a 100% factory engine @ 9psi)

Sounds like heatsoak on the stock intercooler.

Heatsoak was my initial thoughts as there was no warning lights, and the car still ran fine. And on the way back home once it had sat cooling for a while, it was back running full boost.

So is there a cure for the heatsoak apart from fitting a bigger cooler?

[Boosted_162]

There won't be any stored CEL codes if the CEL isn't on. That and it won't be in limp mode unless he hits boost cut (he'd definitely know about that and he certainly wouldn't hit boost cut on a 100% factory engine @ 9psi)

Sounds like heatsoak on the stock intercooler.

Heatsoak was my initial thoughts as there was no warning lights, and the car still ran fine. And on the way back home once it had sat cooling for a while, it was back running full boost.

So is there a cure for the heatsoak apart from fitting a bigger cooler?

The cheap and rangi way to do it, is by disconnecting the air temp sensor on the engine lid. The fan on the intercooler then runs permanently.

[thornz]

I like rangi if its free and works

One other quick question, I'm gonna do a oil and filter change this week some time. Where is the best place to dispose of waste oil? Do most dumps have a place to dispose of it?

[KwS]

a couple of the ones in chch do. uh, the one over wigram way does for sure. There is one that doesnt.... its over ferry way, but cant remember what that area is called. atleast, they didnt when i was last there.

[thornz]

a couple of the ones in chch do. uh, the one over wigram way does for sure. There is one that doesnt.... its over ferry way, but cant remember what that area is called. atleast, they didnt when i was last there.

Cheers mate.

[Twolitre]

There won't be any stored CEL codes if the CEL isn't on. That and it won't be in limp mode unless he hits boost cut (he'd definitely know about that and he certainly wouldn't hit boost cut on a 100% factory engine @ 9psi)

Sounds like heatsoak on the stock intercooler.

Not all codes put the CEL on. It's quick and easy to check your ecu for codes to eliminate other possibilities.
Surely a heat soaked intercooler wouldn't cause the turbo vsv to close would it?

[AJz]

i would have said boost leak but if its fine on the way home that doesnt make sense.

you could try disabling the vsv but of course you would need to give it death to get it real hot, thats assuming next track day is a while away.

ya havnt had any probs before taking it on the track ?

[fivebob]

Surely a heat soaked intercooler wouldn't cause the turbo vsv to close would it?

Not on a Gen II 3S-GTE, there's no manifold temp sensor

The VSV will close if the engine temp is too high or too low, or if the intake air temp is too low.

[Twolitre]

So therefore whether or not the IC was heatsoaked would not be causing the lack of boost. It is more likely that the water temperature was too high or the sensor itself may even be faulty.
If there's no codes and everything checks out you may as well block off the vsv and run an aftermarket boost controller.

[thornz]

i would have said boost leak but if its fine on the way home that doesnt make sense.

you could try disabling the vsv but of course you would need to give it death to get it real hot, thats assuming next track day is a while away.

ya havnt had any probs before taking it on the track ?

When I first got the car, the malfunction warning lamp came on, which turned out to be just some loose wiring, which put it into limp mode. But since then have had no dramas whatsoever with it.

Surely a heat soaked intercooler wouldn't cause the turbo vsv to close would it?

Not on a Gen II 3S-GTE, there's no manifold temp sensor

The VSV will close if the engine temp is too high or too low, or if the intake air temp is too low.

Its a gen1 3sgte if that makes any difference?

[iOnic]

It's a Gen2 3SGTE and a Gen1 SW20. MR2's don't come with the Gen1 3SGTE - ST165 Celicas do

[thornz]

It's a Gen2 3SGTE and a Gen1 SW20. MR2's don't come with the Gen1 3SGTE - ST165 Celicas do

Ahh okay

[Akane]

IIRC you get that when excessive knock is detected, it happened to me many times when I was down at meremere during the day, but less during the night, I have my boost set to 1.1bar and at times drop to 0.5bar when this happens, the VSV disables.

If I get a clean run I'll get mid to low 13's, but when it happens (most likely on 2nd gear after the launch), I'd get mid 15's.

It goes:

1) Lineup
2) Launch 1st gear, moderate wheelspin all the way to 6krpm, boost is normal at 1.1bar
3) chop to 2nd, boost stuck at 0.5bar
4) If I play with the throttle a bit, let it off and back on, sometimes it'll come right back to 1.1bar


Try retard timing a bit and see if it helps.

[Twolitre]

Akane do you run an aftermarket boost controller AND the vsv plumbed in together?
I don't know of anyone who's managed to do that and maintain constant boost levels. It is the norm to disable the vsv when running an aftermarket boost controller.

[MAGN1T]

Another possibility is an exhaust leak. Cast manifolds can warp and unseal but only when excessively hot. No you won't nessecarily hear it either.

Steve