KG engine head modifications

[Tony Hoffman]

Well, you have several options here. 
 
First, a longer duration camshaft has the effect of lowering the static compression ratio. This usually evens out back close to the dynamic CR around 3000-3500 RPM, depending on engine efficiency. This is one of the reasons big cams loose torque (there are several others, which aren't relevant here).
 
So, you can add a bigger cam to your head, and this may help. You can also try running the engine cooler. This decreases detonation quite a bit. The usual combination is cooler thermostat, cooler radiator fan switch, and make sure the radiator is in good working order. YOu might also want to run a larger oil cooler, as the oil gets sprayed onto the bottoms of the pistons to cool them. You might also try a bigger intercooler (does a KG even have an intercooler?).
 
You don't mention why you have the boost so low. Is there detonation or preignition going on at higher boost levels? Is it just for peace of mind? It is possible to run a turbo engine that high of CR, as the 1.8T is 9.3:1. The key is to design the whole package around it. By going with a larger cam, lower opperating temps, etc, you may get away with not lowering the CR. The significant advantage to the higher CR is torque at low boost levels. That's why the 1.8T is more responsive off boost.Then again, maybe you just want it to run as stock. 
 
Hope this is of some help,
Tony Hoffman

Christo Atanasov <quattro at elit-auto.com> wrote:
Hi all,

First I really does not know for which subforum is my question - for MB specific, or for WR specific, because it is KG specific :). 

I have an '85 Audi 200 with KG motor for some reasons it has static CR of about 9.9:1 (too many head removals and regrinding of the head) so for now I drive with boost of about 0.2bars. Now I plan to use another head from WC engine (solid lifters) and make some modification of it chamber (about 3cc more volume - cutting edges beside of valves in order to achieve something like this http://quattro.elit-auto.com/temp/Image015.jpg). Then I plan to put Multi Layer Steel head gasket from 2.5TDi engine which is approximately 1mm thick, so I think I'll finish with static CR of slightly under 8.5:1. I know that factory CR for KG engine is 8.8:1, so my MAC-05A wants to manage ignition of engine with such CR. First question is - how this difference from 8.5 to 8.8:1 will affect performance. How about if I swap camshaft with WC camshaft. It has about 10 degrees longer intake and exhaust phases and 10 degree overlap between exhaust close and open of the intake valve. You can seen camshaf
t specifications at Huw's website: http://www.humanspeakers.com/audi/engines.htm (very useful information. Thanks a lot Huw!) I think that with this setup will be better if I lower static CR. This wide phase camshaft may give me higher dynamic CR, so I think my ignition ECU will be happy with it.

What do you think - what will be better choice, to go with WC camshaft, or to keep my original KG camshaft, maybe a little bit retarded - intake to start about TDC, instead of those 4 degrees BTDC.

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