crcain

Recently my two friends and I were all tuned at the same time. We all run Autronic and all drive Evo 6. There was an interesting difference in terms of ignition timing between the cars that I thought was worth talking about.

Without going into too much detail the specs of the three cars were:

#1: buschur 2 litre + ported head, 9:1 CR, +1mm oversize valves, HKS 272, Evo 9 turbo

#2: forged bottom end 2 litre, 8.5:1 CR, stock head, Revolver cams, fererra springs, evo green, ported intake mani, exhaust mani, and TB

#3: magnus 2.4 + ported head, 8.5:1 CR, std size valves, MAD spec Piper cams, AMS GT35R + HTA, Magnus intake mani

In terms of power.. the #1 and #2 cars recently went to the track. #1 ran 11.9 trapping 119mph... #2 ran 11.6 trapping 116mph (lifted before end of track). 1.9 60 fts for both. #3 has not run at track due to oil leak issue but it was obviously a lot more rapid than either of the smaller turbo cars.

The point I'm trying to get to though is the following... at 2 bar of boost... the #1 car takes almost 10 degrees more timing than the #2 and #3 cars. I think the answer to this is primarily camshaft selection. The Revolvers and Piper cams are quite aggressive with big lift, while the HKS 272's are more mild. Is that likely the main reason for the difference in ignition timing the cars can take?

Nez136

iTrader: (10)

Data logs?

meckert

iTrader: (11)

No logs needed... in short yes...to your assumption....normally a more aggressive cam will give you more cylinder pressure---hence more HP higher in the rpms... You see this in NA cars as well...

crcain

Yeah I was thinking.. a more aggressive cam pulls in more air on the intake stroke, and therefore when compressed you have a greater cylinder pressure, and therefore have to run less timing than a more mild cam.