KG engine head modifications

Fri Sep 30 04:11:44 EDT 2005

Thanks a lot Tony!

It was strange for me to hear that wider cams lower CR, but after reading your e-mail I find some information about this and it is true. (Still can't imagine why). You are right, I didn't mention why I keep boost so low - reason is that I have a lot of detonations if I drive in city traffic, and engine gets hot. If there is a fresh air flow it is better. Oh I forget.. I drive with highest octane fuel that I can get (OMV pretend that it is 100 Octane). About intercooler - Yes KG have stock double pass intercooler like early MC, a few months ago I switched to single pass cooler from Lancia Kappa (almost same volume but single pass). I'll try with colder thermostat any way, now I have a little bit higher engine temp. Yes you are right modern turbo engines operate in even greater CR, but they are whole new thing. Latest Audi 2.0TFSI engine have CR over 10:1, but it is FSI engine and I think that injecting fuel directly into combustion chamber greatly reduce temperature of fuel/air mixture. Also these engines have modern engine management, and smaller chargers than my K26.. When I saw K03 of 1.8T for first time I start laughing, it's look more like turbo from small diesel engine. After drive A4 with this engine I understand why. It has no lag, starts pulling in a very lows revs.. It is extremely pleasure to drive such car in a town. But to mine problem, so after reading your answer I think that I can skip head work for those 3cc of more combustion chamber, and instead to use wider cams from WC (still have doubts about this 10 degree overlap in a turbo application), cooler thermostat, and a thicker TDi gasket.

I'd like to thank you again.. Your post was very helpful for me!

Regards,

Christo Atanasov

  ----- Original Message ----- 
  From: Tony Hoffman 
  To: Christo Atanasov ; quattro at audifans.com 
  Sent: Thursday, September 29, 2005 7:54 PM
  Subject: Re: KG engine head modifications

  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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