BTW - This is a mega-thread - over 4000 views now...

I've played with virtually all the combinations (see earlier in this thread), and decat from turbo back does not give a mega problem, or one that probably can't be controlled with restrictors, but adding the up pipe *does* send the boost spiralling to 1.7 bar.

Still no cheap as chips cure for that as far as I have heard (adding a Unichip or similar is NOT a cheap fix!).

Personally, I would ONLY now fit an up pipe with a flexi joint in, a la MRT, NOT a solid one.


All IMHO, of course.......

Dave,

The Unichip can't really control the boost either - that's why Grant added the Dawes (which does).....

Matt :)

Ah Dave, but the one thing you didn't do was change the restrictor and this is the ONLY thing that needs doing ;)

Pete,

I had my restrictor drilled out to 0.9mm, from the std 0.75mm. The spikes are still to about 1.4ish bar in 4th gear, WOT. Fully std exhaust.

I will try 1.25mm. Theoretically, it should make the car *slower* right? The boost will build slower as the wastegate opens sooner.

Right?

Dave did you not try a restrictor when you decatted yours?

RT

At 1.25mm the car is a lot quicker than standard to get on boost, but boost is controlled. Remember at this size, it still overshoots by 0.1bar to 1.2bar.

Urm Pete, this is a 1.25mm restrictor with std exhaust. Not a decat. Will it still be quicker?

If you guys replace the restrictor with a small flow control valve then you will have a lot more accuracy of control and they are only £7 + VAT. Won't look standard, but then neither does a new exhaust!

Roger

1.25 would be much too much for the standard exhaust. I think you are going to have to experiment with different drill sizes or follow John's advise and get an adjustable restrictor.

John can probably give you a URL for an adjustable one, on-line/mail order.

Deep Singh
Carolyn's was decatted on 1st March. 1.7 bar boost spikes weren't a widely known problem then.


Ah Pete, I know, but when we discovered it produced spikes, we preferred someone else to do the research at that point so we could come back when it was fixed - the lazy approach;)

[Edited by Dave T-S - 5/24/2002 1:40:17 PM]

Pipemore in Glenrothes, Fife, Scotland supplied my flow control valve with the right size of barbed hose fittings on either end. I posted all the details in an old thread - I presume the hose size is similar on the STi. The thread link I posted in my original contribution to the Drivetrain FAQ thread "Flow control valve replacing restrictor". In the spec of the valve you can tell the orifice size the valve will go up to - judge this by the size of restrictor - my restrictor desired size was 1.35 mm and I used a valve with about 2.5mm adjustable orifice and it ended up about 5 turns out of 10 and very easily and accurately adjustable.

[Edited by john banks - 5/24/2002 1:42:26 PM]

John and Pete, many thanks!
:D

Hi Guys,
Not so good today have 1.8bar on the defi!!

Jonno.

Jonno

Got your message. In the post :)

Ok, this is an interesting subject, and one I have a vested interest in ;), but I have kind of lost the plot as to who has or hasn't cured the problem at this point!

It now seems that a full decat *including* replacement up pipe is the problem combination, so let's ask the question again:

Who has fitted a full decat, including up pipe, and *definitely* cured the 1.7 bar boost spikes? If yes, is it a UK or JDM spec car and what was done to fix it?

Ta!

I can vouch that without the uppipe but with DP.Mid and backbox 1.25mm restrictor sorts the problem on my JDM.Bretman has the same experience.

Absolutely Superb !!!!

I should be ordering my decat system soon....yeeee haaaaa !!!!

Please post any updates as they may arise BretMan and Deep :) Thanks.

What BHP and torque figures do you think conservatively you can expect from your decatted systems on your JDM STI-7's ?? 300 bhp and 290 ft. lbs. of torque ????

Deep, is there much change in exhuast sound with your full scoobysport decatted system ??

Cheers,
Ray

Razor,will only answer you from now on if you promise me free accomadation in the Bahamas

Hi Guys,
My JDM STi 7 Has SS-up Pipe, SS-down, Hks TT Centre & Rear, Aps Ind Kit .

Having changed from a two port to a three port (everythig was okay till the later part of last week) so things only gone pear shaped over the past few weeks, anyway Mr C is putting a few restricters in the post to me to try out.... Will try and change back to the two port tommorow and see what effect this has!!.

Ray,
Did a power run @ PE and i acheived 337Bhp & 295 Tqe, all with the above except for running the standard two port BS.

Hope that helps.

Cheers Jonno.

Thanks Jonno,
Keep us posted !

Uhh...Deep, that depends, are you beautiful girl in your low to mid twenties ?? :) If not, no dice :)

Ray

Thanks Jonno. We'll see what effect the restrictors have.

Any more?

bttt


Please see my 2.5" vs. 3" exhaust post :) Need answers I am ready to decat my car now !!! :)

Cheers,
Ray
JDM STI-7

bttt

Jonno:

Just to confirm - in our testing over here the 2 port was much more consistent.

The 3 port did work *sometimes* but gave different results in different runs.

And yep, I consider it sorted now.

BTW 337 hp - whats that in KW?

Bretman

Cheers - so remind me - what mods do you have, and what was done to cure the spikes.

bttt

Jono have you fitted them yet?

bttt

Another bit of feedback regarding decatting the STi7....

Removed the up pipe from Carolyn's car today and put the OEM (sleeved) pipe back on.

The total system is now back to standard, and it has cut the peak boost back from 1.5 bar to 1.35 or thereabouts.

What was interesting - when the up pipe was removed, the bottom gasket (between the up pipe and exhaust manifold) had disintegrated on one side. This is a triple layer laminated solid steel gasket:eek: . I can only conclude that unless the gasket was faulty (difficult as it is laminated steel) then it was running some VERY severe EGT's. This gasket has disintegrated in 2500 miles......

I remain convinced that the up pipe is the villain of the piece here, not the downpipe.

Interesting to note that in all the PPP development work Prodrive have left the OEM up pipe firmly in place.....


[Edited by Dave T-S - 4/6/2002 11:26:28 PM]