alfriedesq

Am running STI vii new age motor all stock - except have BPM 3" exhaust

I am having massive boost spike problems and even with a elctirc boost controller and a very low gaion setting the boost is hartd to control

Anyone have any ideas on what i can do ??

Thanks !

Deep Singh

Hi there.Similar problems over here also.My standard 7 is peaking at 1.4 and decatted ones were spiking at 1.7 bar.Some people are experimenting with different restrictors and also replacing the 2 port boost solenoid with a 3 port one.I'm having the 3 port fitted before I decat.Thats as far as my knowledge goes I'm afraid hopefully one of the more technically minded will give more details.

Deep Singh

What fuel are you running on and have you got a Knocklink to pick up any det.

mutant_matt

The trouble is that when fitting a full de-cat exhaust, the OE wastegate can be fully open and boost can still be rising (saw this on Jonno's STi @ PE the other week).

It doesn't matter what you do, if the wastegate is fully open and boost is still rising then I guess there's nothing a boost controller/solenoid is going to be able to improve upon.

I guess the answer is a more restrictive exhaust, probably coupled with some form of boost control (restrictor/EBC/Dawes/re-mapped Boost maps etc. etc. ).

Presumably, the other answer is a new turbo with larger wastegate but then you're looking at a re-map for the new turbo...can of worms....

Matt

Dave T-S

This will give you some info...


http://www.scoobynet.co.uk/bbs/threa...threadid=80851

but unfortunately may not give you a solution.......

alfriedesq

MAN - looks like a nightmare !I think it looks like the wastegate is too small as it makes the same problem with the stock soiloid and with the blitz SBC - even on the lowest gain setting

I'll try swaping turbos tonight to the PE 1820 and see if a slightly better wastegate helps to keep matters under control???

carlos_hiraoka

Alfried,

Why don't you first try by fitting back your OEM exhaust system, or at least the OEM downpipe.

Carlos H.

alfriedesq

It seemed from what I was reading on that other forum that othere were having the same (but slightly less) boost spike and fall even with totally stock exhaust ! Besides - stock is NO answer for ME ! I am looking for big HP

There has to be some way around this problem without having to use that joke downpipe the car comes with >>????

In addition to the question about the stock wastegate being able to handle the flow of this turbo ; I have questions abou wether the AVCS may eb the cause of this problem

I had a 2002 US WRX engine in my car before this sti one and I used the same VF30 turbo with no ILL effects of boost spike or anything similar - was using the same BPM tiwn dump downpipe and Blitz SBC boost controller

Therefore - it seems the problem - if any - is relative to the STI motor - - - thats why i suspect its the AVCS - esspecially since I can feel the touruqe curve chaging when the boost is falling off the spike - (seems tha cam is changing then)>???

carlos_hiraoka

Alfried, r u using the same uppipe on the new STi engine, that you were using on your previous WRX engine ?????

Carlos H.

BretMan

Matt:

Are you using a downpipe with a seperate wastegate and main outlets? The power engineering one (T75) has two separate outlets with pipe walls in-between.

I remember in previous discussions on downpipes, there were problems due to the direction of flow out of the wastegate hitting the plate or pipe wall (i.e. at an angle towards the main outlet) causing backpressure which stopped the wastegate working propertly.

This could be solved by using an open mouth downpipe like the Scoobysport one.

I think its pretty unlikely that any turbo unit would be designed with a wastegate too small to vent the pressure it generates?

alfriedesq

So far - I have the stock exhuast manifold and the stock upipe from the JDM STI 01

In the WRX I had a modified straight uppipe and cusco headers

I am going to throw in the cusco headers, perrin 2" uppipe and PE1820 turbo tonight and see if the Blitz SBC can gain control of the boost curve ???????

alfriedesq

OK guys - I fixed the problem

BTW - i am running a 2 " uppipe - BPM twin dump down pipe and 3" turbo back with no cats

All you need to eliminate the boost spikes is a bigger turbo with an upgraded wastegate actuator - I am using the PE 1820

Maybe there might be upgraded actuators that you can get seperate from the turbo

BUT - I think it was the combination of a slightly slower spooling turbo AND the better acutator which solved the boost spike problem !!

mutant_matt

Bret,

At this moment in time, I'm using nothing as I just sold my MY00 and my STi should be with me in a few weeks. At the moment I'm just an interested party. What you said about the restrictive OE exhaust makes sense, but, Jonno's JDM STi7 that went on PE's rollers had a full decat system (can't remember which one but it was something like SS DP, HKS Hyper + an up-pipe) and he was the guy who had his wastegate completely open with boost still building. I think he ran something like 1.5bar on that run and got 337bhp because of it....

Alfriedesq,

It seems I was right then, which is actually a bad thing. I was hoping there would be a solution which would not require the changing of the Turbo (though I suspected the worst )

Perhaps you can get a VF30 but with a larger wastegate? (so the Turbo looks like the OE for warranty purposes... )

Matt

mutant_matt

One other thing I just remembered, Grant has a full SS system including up-pipe and is using a Dawes to control boost. He is running 1.25 bar with no peaks (I think). So if a Dawes can control it, why can't an EBC and of course, the fact that the Dawes seems to be controlling it contradicts my previous staement that the Wastegate is too small......

If you can (depending on the exhaust) solve it with restrictors, that makes more sense because presumably, the wastegate is partially open during spool up, restricting the speed at which the spooling takes place which presumably enables the ECU to maitain (just about) control. With the Dawes, the Wastegate is kept completely shut until Target boost is achieved and then the Wastegate is opened. This creates a rather fast spool up ( ). If the wastegate was too small then surely, at this point, overboosting/spiking would result??????

HELP!

Matt

mutant_matt

I think I need to do some datalogging with Delta Dash in Grants car to see what's going on...I'll see if he's game....(and Jonno too perhaps).

Matt

Arron

Matt you seem to have done your homework, after reading these replies I see a lot of talk about the VF30 turbo, I have a uk spec STI and it has a VF32 turbo, does this mean I too will have the boost spikes or as the turbo is a different model will I be ok to do a full de-cat with no probs.

Arron.

mutant_matt

Arron,

YHM and have you read the other (long) STi boost spiking thread?

Q for peeps, is it a VF30 or 32 on the STi? I thought it was a 30 but can't think why I thought that....????/

Anyone?

Matt

Deep Singh

I hope Jonno does'nt mind me posting this but things have moved on a bit.After a little fix he now says he spikes to about 1.3 bar max and holds 1.2 to 1.3bar(which dependant on gear seems ok).Importantly he has a Knocklink which shows no det at all(SUL and OB)Before the fix he was spiking over 1.5 bar and had some det.He is running a full decat and uppipe.(Jonno I hope you d'ont mind me posting this )

Arron

Sorry made a mistake it's not a VF32 it's a VF35.

Arron.

Pete Croney

Jono has replaced his 2 port solenoid with a 3 port. No other mods and no spikes beyond what the standard exhaust causes in 5th and 6th.

This means that the wastegate is sufficiently large, but its control is pants in standard form.

Dave T-S

Yup, confirm its a VF35.

mutant_matt

Pete,

How does a 3-port vs 2-port improve boost control? Has Jonno changed the restrictor too?

Matt

alfriedesq

There are NO boost spikes - PERIOD - at all after swapping out the turbo !

mutant_matt

Wouldn't expect there to be alfriedesq, but that's rather more than many people are willing to do.

Matt

Deep Singh

Agree with Matt,its hardly a real world answer for most of us.Matt I'm quite sure its without a restrictor but I should know for sure by tonight.I'll mail you if you like.

BruceWarne

Would also like to know about 2-port vs 3-port solenoid. Is the 3-port a Subaru part? Is it a drop-in replacement? Where can I get one?

Thanks
Bruce

BretMan

Checked it out in NZ - It is a Subaru part made by Denso. I think it as fitted to earlier years models?

The cost over here is $290 NZD which is around 1345 Rand or around £91 GBP.

Fitting is pretty easy - I think it even has the same electrical connector - just a bit of minor plumbing replacing the T-piece and maybe lengthening a pipe or two if necessary.

Anyone comment on why a three port is more effective than a two port? - my guess is it gives quicker response without having the T-piece/restrictor in the equation?

BruceWarne

Thanks!
Do you have a link to that info?

BretMan

Not specifically for that part, but the company concerned is Maclennan Performance in NZ:

www.maclennanperformance.com

Dave T-S

Bob Rawle here brdevelopments.com put me on to the 3 port solenoid fix (I haven't done it, waiting to see what comes with the PPP - zzzzzzzzzzzzzzzz ).

[Edited by Dave T-S - 5/15/2002 9:05:21 AM]