911

Have an Sti v3 with apexi FC 20g TD05 etc.
The turbo is a rebuilt AndyF and is great, but one thing; the boost builds quite early, ie 1bar @ 3400, pushes 1.4/1.45 bar @ 5500 but then falls off to 1.1/1.2 at 7000 ish

Well Lane saw the car run 407 x 340 so it all works well, but what components can cause the boost to fall?
There is quite a preload on the actuator already. The dump valve is stock re circ Sti v3
Full engine spec:

Gruppe S headers/helix up-pipe/TD05 20g/3'' decat open neck
550cc injectors/Walbro/parallel fuel rails
Apexi FC/3 port Solenoid/ AndyF map
Sti8 TMIC

Ant ideas please where I might start to get the boost to hold 1.4 to the red line?

Graham.

Pavlo

They often exhibit this problem in my experience. Open neck downpipe seem to suffer paticularly badly. But I've also seen them creep just as often.

Paul

stevebt

iTrader: (8)

just before my gearbox fell apart it drove really slow for some reason could be the makings

911

I thought it could be the waste gate cracking open so shortened the arm (effectively) by moving the actuator back 5 mm. Did that the day before the 407 x 340 Well Lane runs.
Maybe I need to ignore it, just get the feeling that there is some more to be had if I knew the way to hold it.
Thanks for the replies.

Graham.

P20SPD

iTrader: (1)

Split intercooler?

alanbell

iTrader: (6)

This has happened twice with mine , Both times a split weld on fmic, I know you have a top mount , But worth a look, >> cost me a nice shiny fmic, Free if you buy my car ???? LoL

APIDavid

iTrader: (4)

We've got a similar problem here with a car [ nominally an STi Vers 2 ] that we've been working on. It's got FMIC, Link ECu, TD05 / 20G, tubular unequal headers, 550's etc etc and we can't get the boost above 1.2 / 1.25 bar consistently.


Pat Herborn and us [APi] worked like demons on it last week trying all manner of things including adding a ' Dawes ' - Fully wound in it just won't make more than 20 psi and drops off. The engine will run round to 8000 in every gear but it just seems to lack sparkle.

Any suggestions [ that we haven't already tried ] would be welcome.

David APi Engines / APi Impreza
www.apiengines.com

P20SPD

iTrader: (1)

David, they are the exact same symptoms that Alan had with his car. The splits were tiny, and given that a couple of the rally boys have had the seams of the STi8 Top mounts come apart under pressure, it could well be that in grahams case.

911

Good thought.
A simple radiatore type pressure test will see to it using a foot pump and a bath of water or soapy water.

Thanks for the idea!

Graham.

stevebt

iTrader: (8)

bolted my turbo back on today and mine is only peaking at 0.7 bar max cant be putting up with that

David MY99

i'm running a heavier (1.0bar) actuator,and it holds now 1.5 bar till 7500 rpm
With the standard 0.6bar actuator you won't be able to hold boost at higher RPM.
And even with the new actuator i'm running 90% DC at the Apexi AVC-R from 7000 til 7500 RPM

Mark A

iTrader: (1)

Or may be you've sucked up half of the midlands!!

911

No, only when pipes fall of FMIC's can you do that (happened to Carman)

I like the leaking TMIC theory.
Where do you get a heavy duty actuator from?

Car is still mighty quick as it is

Graham.

Andy.F

Graham, yours is probably the highest power level I've taken a std airbox to on a 20G, I'm not sure what their flow limit is but it could well be starting to have an effect here ?
What we need to be wary of is jacking shut the wastegate to produce more boost and finding that the net result is less flow. If the turbo is not making boost on the std wastegate actuator then it is 99% certain to be because there is some other limitation in the system. The other 1% is that the turbo is knackered but you would know about that ie smoke/noise/no boost, if they fail they do it big time !

Andy

911

Thanks Andy.
I am sure the Turbo is very healthy!
I have finally bought a boost gauage to be mounted on the steering column between the tach/speedo so i can see it. Only my daughter wants to drive with me doing boost hold checks ( ) and she's not to accurate.

I think the exhaust is ok for flow (3'' decat) but to open up the induction leads to so many issues, but i feel there is a mod to be tried to increase the panel filter area/inner wing hole. Infact, is this where the bottle neck may be, the hole in the wing?
If I joined the two holes in the inner wing together I double the inlet area when they are both channelled to the air box.
Will have a look this weekend.
Apart from the strange tick-over, the car runs so well I'm worried to upset the settings mid racing season. there is a big break in july, so maybe will try then in earnest starting with the TMIC. I recal MEF saying that he took his apart and silicon'd the header tanks together and re-crimped the joints.
Maybe I should go FMIC soon, but that goes against the grain for some reason.
Thanks as ever to all for the ideas.

Graham.

P20SPD

iTrader: (1)

??

911

P20;
The ?? may be aimed at Andy's thoughts?
I looked at the stock filter chamber over the w/end.
Seems to me the hole over which the housing is screwed is about the same cross sectional area as the hole post the panel filter, so, if the hole in the wing is too small, then the inlet hole to the MAF is too!
Still think it's a leaking TMIC, but I'm the type who rushes off to change the power station to fix the light that's gone off instead of checking the fuse...

As ong as the car keeps winning/second in class I'll leave it till the winter/season close in Oct and have a good look then.

Graham.

P20SPD

iTrader: (1)

LOL @ powerstation

?? more aimed at you, to see if you had done anything

911

No, sadly we have had big family probs iyswim so the Impreza got a quick wash instead (bling) and the P1 wheels back on for the big run to Barbon Manor and on to Harewood this weekend coming.
Got to get my daughter back from Uni too .....she wants to have/race the 911 or the Sti in that order.
She drove the Sti ar Curborough before she had passed her test

Graham.