13 replies to this topic

[MIGLIACARS]

OK i use my car for racing only.

 

1293cc

7 port head

omega pistons.

arrow rods

jenveys

rotrex blower

intercooler

dta

bk450 h/g

 

 

i race for around 20 mins at a time.

 

the will be running around 10.5 psi when the new pulley arrives.

 

what compression should it be running

8-1

8.5-1

9

 

etc etc

 

no guesses just accurate advise please. 

 

 

 

 

 

 

[Turbo Phil]

What are your charge temps, what octane fuel are you using ?

Phil.

[MIGLIACARS]

I dont now my charge temps.

 

the intercooler is big, and the guy at rotrex says if i can get 10.5 psi out of the supercharger the system must be good if this helps.

 

I run normal pump fuel super plus as per the race regs

[mini13]

well, for that boost with a rotrex, and considering you've got an ally head I'd say 9-1,

 

Also what cam, are you running as this has an effect on the compression ratio.

[MIGLIACARS]

its a cast minisport head.

cam is a kent, it has 112 degrees of advance

[mini13]

Chap I know is running 9:1 on a turbo with 12 psi and it does pretty well,

[HUBBA.HUBBA]

Id say 8.3

[Gr4h4m]

I run 8.7 with 10psi suck through

[welshdan]

Id go 8.5 or slightly lower. May be a trade off of some power vs reliability

[HUBBA.HUBBA]

Id go 8.5 or slightly lower. May be a trade off of some power vs reliability

Like 8.3

[welshdan]

Well i ran 10 psi on my old turbo motor, compression ratio of 8.7:1 on standard metro non turbo pistons. 8.5 set up properly should be ok

[HUBBA.HUBBA]

There's a fine line between 'should be ok' and relibility. Imo, I wouldn't compare a supercharger set up to turbo set up.

[welshdan]

You cant say one figgure for sure. There are a lot of variables. State of tune, if its intercooled or not, fuel octane, ambient temps...

You could run 7:1, bit if the fueling and advance were all wrong you will still ruin your engine in a spectacular way within a very short space of time...

[HUBBA.HUBBA]

You cant say one figgure for sure. There are a lot of variables. State of tune, if its intercooled or not, fuel octane, ambient temps...
You could run 7:1, bit if the fueling and advance were all wrong you will still ruin your engine in a spectacular way within a very short space of time...

Just going by expert advice i had been given and passing it on.