(Bit off topic) turbo lag...

Bruce Plecan nacelp at bright.net
Wed Jan 10 16:17:43 GMT 2001


Intake valve closing timing is critical, along with overlap.
Just considering CR is falsehood.
You can make more HP by using more boost, but in non boosted situations you
can wind up with a really lame engine.   Which brings application into
focus.
Bruce


>
> >What kind of high CR are you planning to use? 9 - 9.5 to 1 is about as
high
> >as you can get if you use 102 octane race fuel. With 98 unleaded, 8.5 -
8.8
> >is probably very high. If you compress more, you'll reach the knock limit
> >really early under boost and you'll need to set your spark advance to a
> >(much) less than optimal point, negating most of the benefits of
> >turbocharging.
> >
> I have to disagree with the concept of CR and turbos. Yes a lower CR does
> allow you the ability to run higher boost numbers without retarding timing
> too much, but I know of at least 2 (there are plenty more) guys that are
> running 1.8L 4 cyl with a stock static CR of 10.0:1. The key is careful
> tuning and a good programmable system. I know that they don't run higher
> then 102 octane fuel, and they are making some good power #'s. That being
> said it does require very careful tuning. I am building a turbo motor
right
> now (2035cc 4 cyl DOHC) and I plan on running a static CR of 9.0~9.2:1
> depending on how the head gasket spacer I am using turns out. Going to run
> this on 92 octane with ~10-14lbs of boost depending on what I can tune it
> too. Of course I am going for a full programmable (in my case an
> aftermarket) EFI system
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