Toyota MR2 Message Board - View Single Post

Enthalpy · 06-13-2008, 06:41 PM

At a high level, you set the fuel with known-conservative spark, then advance the timing. Initially do it by a few degrees, then as you approach optimal, slow down. You know you are approaching optimal by keeping old runs on the dyno screen and doing a "power vs. advance" estimate. Do each run at the same temps (can't stress this enough). This is when I LOVE the huge cooling I have on my dyno! I can properly tune much faster than a shop that has no cooling. I have a blower that pumps 45 mph outside air through a 3' X 3' hole straight onto the intercooler and radiator. I have a separate blower for side-mounted MR2s.

You will either hit knock or a spot where torque flattens out and further timing advances don't produce more torque. Obviously, set the timing just shy of this limit. If you hit mild detonation, stop and back off a few degrees. Do this using runs at full throttle, and load-holding at part throttle.

Reset the fuel if your indicated AFR changes. That usually means you started with excessively conservative timing to begin with, and timing changes are actually changing the chemistry of the exhaust or the temp of the probe.

This can also happen if you don't know how to set an air temp offset curve, or if your IAT isn't placed in the correct spot. I flat out refuse to tune a car with the IAT placed pre-turbo. Even clever algorithms like what Autronics use can't completely compensate.

For expected hill racing (I live in the mountains), I will load-hold and purposely heat soak everything then set the temp offsets to keep things safe. I usually like to see EGT data when doing this.

If 1/4 mile racing ONLY, don't worry about part-throttle at all. It's wasting the client's cash. If road-driven or course-racing, set the part throttle spark and fuel.

I personally charge more if the customer wants ABSOLUTE perfect drivability. This requires multiple days to get right (cold mornings and warm afternoons). In one day, I can deliver good drivability, but to perfectly dial in things like cold start, you have to have it multiple days.

06-13-2008, 06:41 PM	#4 (permalink)
Enthalpy EMS Harmonizer Join Date: Feb 2006 Location: Denver, CO Posts: 1,226 Thanks: 8 Thanked 55 Times in 43 Posts My Google Map iTrader Rating: (2/100% )	At a high level, you set the fuel with known-conservative spark, then advance the timing. Initially do it by a few degrees, then as you approach optimal, slow down. You know you are approaching optimal by keeping old runs on the dyno screen and doing a "power vs. advance" estimate. Do each run at the same temps (can't stress this enough). This is when I LOVE the huge cooling I have on my dyno! I can properly tune much faster than a shop that has no cooling. I have a blower that pumps 45 mph outside air through a 3' X 3' hole straight onto the intercooler and radiator. I have a separate blower for side-mounted MR2s. You will either hit knock or a spot where torque flattens out and further timing advances don't produce more torque. Obviously, set the timing just shy of this limit. If you hit mild detonation, stop and back off a few degrees. Do this using runs at full throttle, and load-holding at part throttle. Reset the fuel if your indicated AFR changes. That usually means you started with excessively conservative timing to begin with, and timing changes are actually changing the chemistry of the exhaust or the temp of the probe. This can also happen if you don't know how to set an air temp offset curve, or if your IAT isn't placed in the correct spot. I flat out refuse to tune a car with the IAT placed pre-turbo. Even clever algorithms like what Autronics use can't completely compensate. For expected hill racing (I live in the mountains), I will load-hold and purposely heat soak everything then set the temp offsets to keep things safe. I usually like to see EGT data when doing this. If 1/4 mile racing ONLY, don't worry about part-throttle at all. It's wasting the client's cash. If road-driven or course-racing, set the part throttle spark and fuel. I personally charge more if the customer wants ABSOLUTE perfect drivability. This requires multiple days to get right (cold mornings and warm afternoons). In one day, I can deliver good drivability, but to perfectly dial in things like cold start, you have to have it multiple days.