Hi all, I have just installed a knocklink on my sti 4. I am getting only background noise until about 6000rpm, then it seems to light up an extra bulb per 1000rpm. At around 8000rpm, the red light comes on.
All I have on the car is a twin dump decat downpipe, Blitz centre and backbox.
I have noticed that since fitting the downpipe, my max boost sometimes hits 1.5bar, although mostly its only 1.2/1.3.
I use optimax but no octane booster.
I know ideally I should get an aftermarket ecu fitted and mapped but I cannot really afford to chuck this amount of money at the car at the moment.
Does overboost cause my care to run lean? Shall I stick the original downpipe with the cat back on or use some octane booster?
Any ideas much appreciated.

 

It's more likely to be a boost/ignition issue, although it's possible that the fuel pump is struggling with 1.5bar.

Try using something like NF octane booster, and see if this helps. This will tell you if it's ignition related.

If it works, you have the choice to continue using it, or use something like a Dawes device to reduce the boost.

Mark.

 

Thanks for the advice, do you know where I can get hold of some NF??

 

Got mine from RCM
http://www.nfeurope.com/stockists.htm

 

Do you think putting the cat back on would solve the problem?

 

It is more than likely that the free flowing catless twin dump down pipe is causing your overboost problem. I would suggest as Mark did earlier to fit a dawes device to keep the boost at its correct level around 1.1 / 1.2 bar until you can afford to get something that will control the required amount of fuel / ignition / boost control i.e. remap or new ECU / piggyback of some kind.

 

I have had similar problems with my STI 4 RA. I too had a twin dump downpipe and that was overboosting/creeping in 4th and 5th. After asking the question on here it became apparent the the twin dump was causing the problem. I take it your car has a VF23 ? If so you may want to try a different type of downpipe like an openneck design. Even a Dawes and electronic boost contoller could not stop the creep.

I run octane booster and that helps but if you can't afford a remap then I would seriously consider either putting the cat downpipe on or getting yourself an openneck pipe.

I think others would agree 1.5 bar on that turbo is too much considering standard boost is 15.7 psi (stand to be corrected)

I'm currently running a cat downpipe (not got round to fitting my new openneck yet) and with my apexi boost contoller run 18psi. If I run more boost than this I get det at 6000+ but knocklink is quiet up to 7k at 18psi.

Hope this helps

 

Again, thanks for the replies. I have a vf24. How do both the twin-dump and openneck downpipes differ in gas extraction. I have heard of this problem before, however nobody could tell me why??

 

So I learnt here the gas from the wastegate interfears with the main pipe gases causing creep. As soon as I put the cat back on solid boost controlled by the apexi.

See this thread - http://bbs.scoobynet.co.uk/showthread.php?t=370248

 

Think I might stick the cat pipe back on and see what happens. Atleast I won't be over-boosting. Hopefully this will reduce detonation. Unfortunatly my knock link wasnt fitted until after a the decat.
I may then invest in a scoobyworld vortex backbox and centre section.
Any thoughts or experiences' with these products?

 

i have got the same overboost problem on my mcrae. Wasn't sure what was wrong so the garage came and collected it on a lorry just incase. Anyway they found the problem and have turned the boost down, but still slightly there. The thing that gave it away was it was juddering when accelerating. Gotta take it back to em and they said they'd turn it down slightly more so should solve it.

 

How did they turn the boost down? Boost controller? Also, what caused the overboost?

 

I asked that at the time (what caused it), they didn't give me an answer, hinted that i had turned it up, considering i wouldn't know how or even if you can (bear in mind i only have owned an impreza for four weeks, one week of which its been off the road cos of this problem) do this kinda tells me they were looking for a reason themselves, gotta speak to them tomorrow so i shall ask em see what they say.

Not had a boost controler fitted, they told me they had reset the ecu so guess thats how its controlled, as i said i don't know myself so cant answer i'm afraid mate, i'll post up when i speak to em.