RE: Re: Fwd: Performance Cooling Questions

[Jonas Karlsson <jkarlsso@metabolex.com>]

Scott F. Williams wrote:

>That wouldn't be an amazing amount of trouble. (to wire in a knock 
sensor) >The only thing is that it'll undo
>whatever benefits that I've got with my moderately high 
>compression ratio (10.8:1).
>That is, if the knock sensor just dials back the timing and 
>reduces power anyway,
>then what's the point? I'd rather find another way, short of 
>running race gas on the
>street, to reduce the pinging.

Well, I've been thinking about the banefits/drawbacks of a knock sensor 
system, and here's the conclusions I've made. 

I don't think that the knock sensor will really hurt performance all that 
much, mostly because it only retards timing when it knocks.  It might 
actually help (dunno for sure) by keeping your ignition as far advanced 
as allowed without knocking. If the "knock point" (the degree of advance 
at where you get knock) changes a lot, then the knock sensor will 
definitely help. If the "knock point" is steady then you won't have the 
benefit of a constanly optimized ignition advance. 

Another perspective is that knock is bad. Bad for performance and Bad for 
the engine. Keeping it under control is important, and will keep your 
engine alive for long time. A knock sensor is the just the "big guns" in 
keeping Knock under control. Knock just doesn't get past it. Thinking of 
it this way, it is not the KS that hurts performance, but the KNOCKING 
that causes the KS to "do it's thing"  that hurts performance.

Even after you get a KS wired in, you still need to do all of the other 
things to keep the engine from knocking (reduce cyl head temp, higher 
octane fuel, well formed combustion chamber for optimal flame 
propagation, etc.), otherwise you won't see much benefit. 

Without a KS and without taking steps to reduce knock, you are hurting 
your engine and that's not nice.

HTH

Jonas
85 Scirocco



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