Turbo loosing psi after fast drive

Re: Turbo loosing psi after fast drive (Matts_SW20)

Thu, 06 Jun 2019 21:33:43 GMT

5SGTE
You done an intake pressure test?

I have not, I'm installing a CT20b this weekend. If the problem persists I'll be looking into this.

feral4mr2
Matts_SW20
So if I loose 4 runners would that necessarily decrease boost pressure by turbo?

No. The turbo and wastegate determine the amount of boost seen at the manifold. Piping as well given if there's a leak you'll see less at the manifold.

Yea I thought so. I'll change the turbo and see if I still have this phantom boost leak

Re: Turbo loosing psi after fast drive (feral4mr2)

Fri, 31 May 2019 12:50:23 GMT

Matts_SW20
So if I loose 4 runners would that necessarily decrease boost pressure by turbo?

No. The turbo and wastegate determine the amount of boost seen at the manifold. Piping as well given if there's a leak you'll see less at the manifold.

Re: Turbo loosing psi after fast drive (5SGTE)

Fri, 31 May 2019 11:08:01 GMT

You done an intake pressure test?

Re: Turbo loosing psi after fast drive (Matts_SW20)

Thu, 30 May 2019 21:16:38 GMT

So if I loose 4 runners would that necessarily decrease boost pressure by turbo?

Re: Turbo loosing psi after fast drive (Knightrous)

Thu, 30 May 2019 19:46:22 GMT

Matts_SW20

I thought TVIS was only a 4A thing. This could be a potential cause. I've ran diagnostics on the car and it hasn't recorded a knock code but it could be that maybe? Such a frustrating issue.

Gen 1 & 2 3SG motors featured TVIS. Gen 3 dropped it (Like Gen 3 4AG's)

Re: Turbo loosing psi after fast drive (Matts_SW20)

Thu, 30 May 2019 18:07:06 GMT

Thanks for the input all. The Phantom boost leak is still eluding me. I've been hammering the car to work all week and not being able to replicate the fault. Really cold mornings the car will have a cough at peak boost but this is likely my EBC just regulating pressure as it wouldn't normally spool up that fast.

feral4mr2
Timing advance/retard alters the point of ignition (spark) in the compression cycle. It cannot alter the maximum boost at the inlet manifold set by the wastegate.
I'd be more inclined to look at the wastegate operation and ebc.

Yea I've spoken with Robk about this as well I was misguided thinking pulling timing would result in boost drop. We're convinced its a boost leak that only happens on some occasions but no idea where to start. I think it's time to just bite the bullet and swap in my CT20b

chausta
Has the tvsv been disabled?

Yes, the turbo is not monitored by the ECU anymore it all go's through the EBC and I have a FCD to stop the boost cut.

grosso
If its a gen II you have tvis which is controlled by you the ecu, if knock is detected it will close the butterfly and you will have only four intake runners open above 3600rpm. After the car has been switch off and restarted it normally reset back to standard if it does not detected it again. This will affect what you feel. Hard corning low fuel in tank can give a lean out, create knock. Just double check for boost leaks etc.

I thought TVIS was only a 4A thing. This could be a potential cause. I've ran diagnostics on the car and it hasn't recorded a knock code but it could be that maybe? Such a frustrating issue.

Re: Turbo loosing psi after fast drive (92 Hard Top)

Tue, 28 May 2019 12:17:31 GMT

If its a gen II you have tvis which is controlled by you the ecu, if knock is detected it will close the butterfly and you will have only four intake runners open above 3600rpm. After the car has been switch off and restarted it normally reset back to standard if it does not detected it again. This will affect what you feel. Hard corning low fuel in tank can give a lean out, create knock. Just double check for boost leaks etc.

Re: Turbo loosing psi after fast drive (chausta)

Tue, 28 May 2019 01:31:42 GMT

Has the tvsv been disabled?

Re: Turbo loosing psi after fast drive (feral4mr2)

Mon, 27 May 2019 23:17:22 GMT

Timing advance/retard alters the point of ignition (spark) in the compression cycle. It cannot alter the maximum boost at the inlet manifold set by the wastegate.

Retarded ignition can actually premote earlier spool via higher EGT's, can also provide less/sluggish power, but as above not lower the amount of boost seen at the inlet manifold.

I'd be more inclined to look at the wastegate operation and ebc.

Re: Turbo loosing psi after fast drive (Matts_SW20)

Mon, 27 May 2019 21:34:56 GMT

Something is reducing my available boost and I couldn't think of anything that would be other than timing. I assumed that if its retarding the timing then thats reducing cylinder pressure and the subsequent pressure to spool turbo? Forgive my lack of knowledge I'm no engineer.

Re: Turbo loosing psi after fast drive (feral4mr2)

Mon, 27 May 2019 21:30:14 GMT

timing retardation doesn't reduce the amount of boost from the turbo.

Re: Turbo loosing psi after fast drive (Matts_SW20)

Mon, 27 May 2019 21:24:29 GMT

These were my thoughts as well the turbo is not monitored by the ECU anymore. But it gets killed by something in the engine which I assume is it pulling timing given there's little else it could do that would reduce boost pressure.

Re: Turbo loosing psi after fast drive (feral4mr2)

Mon, 27 May 2019 21:21:18 GMT

i fail to see how even if the ecu has detected detonation and retarded timing that the boost pressure would be dropped, the turbo will still boost to what the ebc is set to.

Re: Turbo loosing psi after fast drive (Matts_SW20)

Mon, 27 May 2019 20:57:51 GMT

I've never really had the issue on cold mornings. If anything its when the engine is hot. Could be detonation but I hope it isn't.

I actually hope its the turbo because I have a CT20b ready to go on. The existing CT26 turbo has done 270,000k's so it's probably time for the upgrade. The only thing that bugs me is, wouldn't the problem be consistent if it was turbo related? This is why I think it's a faulty sensor or some electrical gremlin.

Re: Turbo loosing psi after fast drive (Carmikey)

Sun, 26 May 2019 17:13:52 GMT

What condition is your turbo charger in? I've had the same symptoms in a friend car, ended up being a worn seals in his turbo from memory. I'm sure there are other like reasons.

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