compression ratio & boost
Turbo Mini Forums

hi iam running std turbo pistons total seal rings phase2 cam cr of 8.55-1 now the question is what boost is a safe option with this spec also has an intercooler thanks scott

That isn't sufficient information to give an answer.

What fuel mixture, intake temps, ignition timing is a starter.. even then it's a guess.

That's what rolling roads are for.

well I'd put at least 16psi into it.

Edited by minimole23 on 4th Nov, 2011.

theres lots of variables there scott .........But in short!!!

with an efficient! good intercooler well placed and high octain 98+ RON uk fuel.... and MAX ignition advance of 22 deg 16 to 18 psi is not out of the question
and of corse a cool day ambient no more thean 20c

hope this puts you in the picture scott

yeh thats grate i know theres a lot to take into account just a guide is all i was after after reading up on hear i thought 24degrees was a safe timing figure at max advance so am i wrong in thinking this steve? should i just set max advance to 22degrees? & is that with high octain? what would i set it with 95ron?iam after a safe road engine/car so not after it on the limit i be happy with a safe 15-16psi to be honest

for a fun/safe road car try 10psi into it daily and 15psi for fun.

personally i'd run 20psi on it without worrying too much :)

Sounds good but its not my daily so only for fun still unsure about the timing tho will I stick to 22deg iam still on the dizzy so can't do anything fancy

I have a similar spec , P2, 8.6:1 and use 20psi for the majority of the time.

Anything less and it feels like there's something wrong with the car now.

Be warned, it's very hard to turn it down.

In the 13's at last!.. Just

Iam liking the sound of this more & more like I say if I can run 15-16 psi I be happy (I think)

The way I look at it you don't want to your dynamic compression radio to go much above 14.5-1 so on standard pistons 20 psi may see you nearer 15 not the end of the world but you will have to keep an eye on your temps.

Own the day

It's more to do with the temperature of the inlet charge than the boost pressure.

If you could guarantee 25 deg C air then you could run even higher without det.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Well iam getting a bigger intercooler & I have an intake temp gauge so will know exactly what the temp will be at the plenum chamber but am I right in thinking 15-16 psi shouldn't be a problem & in a safe zone for reliability? & what should I set the timing to at max advance? Doest 22deg sound right like steve said? & is that at 95ron instead of ultimate/v-power ect

It should be fine on that boost level. If you're fitting a Air inlet temp sensor, you'd be ebst to fit it in a hose so you get a true reading. If you fit the sensor in the plenum you'll get heat soak.

The best place is just after the cooler, as that would generally be in a place where it won't be effected by heat soak.

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1/4mile in 13.2sec @ 111 terminal on 15psi

The sensor is hooked around the plenum inlet pipe & just in the air stream as its a wire so didn't think that would have problems with heat soak

Is it really necessary to restrict advance to 22 degrees ? I am running 28 degrees on 8.2 CR and 15 psi and it seems to work pretty well.At the RR session the operator said that he thought it needed MORE advance !

22 I agree is conservative, however it is a known value which will be safe until you get on the rollers.

When trimming advance you will find the power at a certain revs and throttle will increase to a plateau, stay at the same level, then tail off. You are aiming to be at the very start of the plateau, using the minimum timing to get the best power.