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DOHC SOHC Ion Updated 1/05 For the most recent list of the fastest five cars click here. |
Tuning Your Turbo Saturn - Part 3by: Qksl2I'm not going to go into how exactly to set your timing, or what to set it at.Why? Because that is for you to figure out, for your car. I have a good idea of what a timing map for your car should probably look like. But refer to Psychological Tewning for a discussion on why, exactly, I'm not going to tell you. All I can say is to start with the boost low, and do everything only one step at a time. You'll learn, but only by experience. Think of each response you make in a rational sense: by making only one change at a time and reviewing what that change resulted in, you'll in no time have a good map setup. On the dyno. Set up your timing map conservatively, at first. Start at low boost, and get your raw fuel work done. Pay careful attention to spool up and peak torque, and also make sure to make runs in third and fourth gear. Why? Make sure that the changes in load by different gear ratios and the time over load differences don't' exceed your fuel delivery and heat things up. You'll see this by high EGT's at the top of a long pull. This is a situation where A/F might be just fine, and you won't even see knock, but your EGT's will be high and you can absolutely blow your motor. "But my a/f was fine and there was no knock!??" I can hear it now… If your knock resistance threshold is high enough, there won't be any detectible knock, but the high cylinder pressures and combustion temperatures held over a long period of time can and will destroy your motor. Got it? Typically this is a condition you will face using race gas, and that is why race gas is dangerous. A sense of false security lol asscroft lol is really the problem. This is the most likely cause of failure for DSM's, as they have a great closed loop knock/timing circuit, but the motor cannot save itself from high EGT's. Our cars seem to respond very well to a good bit of timing under boost. This has been recently illustrated by Chris (tebriel) who just put down 311whp at 17psi on a fifty trim turbo with no timing control whatsoever. Is timing control important? Very. How did he do it? Good fuel tuning. Was it safe? Well, we really don't' know. It seemed to work and still is, but without ignition tuning, a bad tank of gas or changed airflow by different parts could mean the end of that motor in a short time. Despite this, running 25 degrees of maximum timing is what held his motor together. EGT's remained low due to the strong timing. I've tuned cars before on the dyno where we'd pick up 30 plus lb/ft of torque by just a single degree of timing. What does this mean? It means drop the boost and add another degree, see what that does. Keep adding timing and watch your EGT's drop. When they level off, you've gone far enough. However, as you're adding timing, you need to watch knock very closely. See above as to why. I'VE GOT A GAS PROBLEM, DOC
The sound and feel of a rich or lean condition is remarkably similar,
yet different. Bucking under partial throttle is usually lean, but
not always. Just with boosted saturns it is usually due to leanness.
Low RPM bucking on a stand a lone is due to the enrichments working
well for higher RPM but not compensating for the poor VE values
at low RPM, and attempting to add the same amount of extra fuel
despite that. A rich misfire will sound soft, and muted. It is almost
hollow and low in tone, as one cylinder or two will misfire at a
time. As you rev the motor, it will sound like a WRX, which is,
essentially, like two two cylinders. The other time a Saturn sounds
like WRX is when it has a blown motor. Don't ask me how I know.
A lean condition will sound like a hard crack and snap as you attempt
to rev it. You will also likely hear the turbo try to spool…
good but not. You'll want to add more FINAL WERDS
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