martyrobertsdj

iTrader: (1)

Right........

MBC fitted for a while, but set under fuel cut (just)
Knocklink sensor fitted where it's supposed to be (bolt below intercooler)
Take car out for a run....no LED's (other than dim green)
Thrash **** off car....one/two green LED's until rev limiter, then up to orange/bright red
FCD fitted and adjusted a couple of clicks
Tentatively drive car..all seems ok, so boot it!!
Still only one/two green LED's
Turn up MBC to get about 16psi boost
All still seems ok, but still only same LED's

Does this seem right?? FCD is obviously working, because I got fuel cut at lower boost previously (when originally fitting MBC)
Do you think I'm safe to put a bit more boost on??? Actually...MBC seems to have very little adjustment left!!

What do you think for a safe maximum boost pressure??
(I always run Optimax or Super Unleaded/Millers Octane Booster)

Any advice greatly appreciated

Cheers,

Marty

zhastaph

I use a Dawes on my MY99 STi. I find that the max I can safely push the boost on mine is bout 17psi, once i start getting close to 18psi I get the odd amber/red flash from the KL.

IMO the problem lies with the OE fuel pump and regulator, at higher boost levels the pressure in the cylinders begins to overwhelm the fuel pressure at the injectors supplied by the fuel pump. This results in less fuel being supplied when actually more is required, once a certain threshold is passed the result is knock.

As for what pressure to set your boost at, you should aim for the highest that you can get it that you see no ambers on your knock link under any conditions.

nom

A lot depends what MY, martyrobertsdj. The turbo simply gets more inefficient (depending on which one!) the higher the boost, and will just produce hotter air at higher boost rather than any more charge. i.e. there's no point going above a certain boost level.
Each car - within each MY - will also vary, some taking more boost, or requiring more octane booster for the same boost level (can't take as much advance), etc. Looks to me that you're going about it the right way, though! Det cans are always a good move, but the KL isn't bad at all, especially if it's set to maximum sensitivity?
Another thing - the more boost you set, the less advance you can run. Advance is a good thing . I've found that a good compromise on the 'standard' turbos is ~17psi - should be very safe (not forcing anything) as long as the fuel is high enough octane rating (judge by the KL as you already are), although other do like higher boost, it all gets a bit 'diminishing returns' if you ask me

martyrobertsdj

iTrader: (1)

The car is a MY98 UK car with full de-cat.

I was thinking of going for an electronic boost controller, as the current MBC seems to be struggling to get more than the 16psi.

Maybe it's actualy the turbo that is struggling??

I do find that the boost drops significantly above say, 5000 rpm. Is this a characteristic I can overcome with a better boost controller?

Cheers for the input so far peeps.

Marty

manny

agree with nom.......i had intermittent red flash on the KL, came to the conclusion the TD04 turbo was just superheating the air leading to det.....turned the boost back a bit and nothing other than one green. Its not worth being greedy for that extra tiny amount of boost!!