Thread: Timing advice
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Old 02-27-2006, 11:40 AM   #9
Speedworks801
Scooby Newbie
 
Member#: 43461
Join Date: Sep 2003
Location: Utah
Vehicle:
2004 STI
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I will tell you what I have done in the past. I look a basemap for your car and look at what timing values they used at what boost level. I also look at a dyno for your setup or as close to it as possible. Look at where peak torque is. Peak torque = Peak cylinder pressure. Because an engine is a glorified air pump it has an rpm range where it pumps most efficiently this is a curve that is best represented by your torque curve on a dyno. As this torque is low, adding timing (TO A POINT!) adds to cylinder pressure, adding boost adds to cylinder pressure, leaning out the a/f ratio adds to cylinder pressure. But remember that fuel is also coolant for the combustion process and you should always stay to conservative a/f ratios especially for long freeway pulls where this cooling is critical to engine life. We tune drag cars very differently than road-race cars or freeway racers. This torque curve is a representation of the only two things that really make a car go. OXYGEN AND FUEL Every mod you put on a car is involved in producing more of one of these two ingredients. The way you manage these is really what tuning is all about. It's hard to talk about any of this stuff without wanting to talk about all of it because a complete understanding helps you with each part. Enough said.

Depending on your setup the information may be easily accessable or difficult to find. Look at what you have changed in relation to the basemap you are using and you can usually create a pretty good basemap. This point I cannot stress enough STAY TO THE CONSERVATIVE SIDE! The difference between ringlands and happiness is usually only about 3 degrees. 3 degrees on a dyno may only cost you 20hp depending on your setup. So take the 20hp loss and keep your motor. EGT's also help. You've probably stumbled across the concept that pressure equals temperature. EGT's become an indication of a/f and timing. Make sure you use other people's egt's as a guage to see how you compare. If you are dramatically different, chances are something is not as it should be.

So for a street tuned dynoless map I always keep the boost a little lower than I probably could, the timing a few degrees low, paying special attention to peak torque (this is where most damage occurs) and the a/f's a little rich. In the end you may make it to the dyno and find 20hp or 50hp but the key phrase here is "make it to the dyno". Know what I mean?

Best of luck
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