Lower timing will make your EGT's INCREASE, allow quicker spool up and allow more boost BUT your HP will decrease do to the lower timing. Also you will probably notice lower throttle response.
Higher timing will lower EGT, more your turbo spool a tad slower, but will gain HP if your not detonating.
I know most think the opposite, but this is the way it goes. On the GNs running a translater we usually pull 4-6 degrees from the bottom end (under 3500rpm) then add 6 back on top which helps the car spool better (because the hotter EGT spike) and then adds the timing back for more HP.
The 'combustion' happens before top dead center (TDC) right? The more advance you have the longer the time between the combustion and TDC. So the more advanced the spark the more that 'cumbustion' is still going to be compressed as the piston comes up to TDC. This generates a lot of opposing forces and a byproduct of that is heat. Also think about the further advance you have the more time there is before the exhaust valves open to release the hot (post combustion) mixture. So more advance exposes the combustion chamber to the heat longer then less advance. Maybe TurboMike's obseervation of a lower EGT with more advance is because the engine is absorbing more of the heat before the gases are finally released to the exhaust piping.
This is just how I've thought it thru... if anyone wants to shoot me down please fell free.
92 Laser RS-T FWD
[This message has been edited by Quadcylla (edited October 06, 2000).]
I've definitely heard consistent views with what Mike has explained regarding timing adjustments.
Are there any reliability issues with going from, say, 5 degrees retard at 4,000 RPM to 7 degrees advance by 6,000 RPM? Also, for drag racing what would be the better alternative: retarding initially and then advancing later or just advancing across the board to realise better hp? I guess if you are launcing at 5,000 RPM the timing retard never comes into play.
Im not sure how the fuel and timing maxtrix is setup on Mitsu, but timing has to do with rpm and load also. (side question: Does SpeedPro/FelPro make a unit for mitsu???)
With a turbo car in general, you want to taper your timing to go lower with load and rpm. How much, I'm not sure (Im used to GrandNationals) At 25psi on the Buick i would run about 24 degrees timing on the top end. Each car is different. Some like more boost less timing. I believe the smaller turbo cars would benifit from more timing and less boost due to the efficency of the turbo not being to well at higher boost.
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