Tuning for AFR and timing
I have tuned most of my FWD on the track for many years. Does it work and be relatively safe, kind of. Kind of for the simple fact of your are trying to tune in a uncontrolled enviroment with alot of factors that don't stay consistent. Don't get me wrong, you can get it close but never its full, safest potential of making power.
The dyno is the place to be for the simple facts of consistency and predictability. For any car that is considered a daily driver you really are shooting to find the motors MBT and nothing more. On a dyno it allows you to find this fairly easy and in the most safe enviroment possible. Finding MBT is a comprimise of both A/F ratio and timing (especially on pump gas), not a extreme amount of timing or a really lean A/F ratio.
My method of tuning a race gas map was to first have a optimized pump gas tune that I had known was good. I tuned the car for pump gas first dialing in the A/F ratio across the rpm range with a known safe timing map. Then I would increase the timing either 1 or 2 degrees at a time making any small adjustments I needed to the A/F accordingly. I would increase timing untill I saw the torque curve start to drop and/or lost peak torque. This would allow for a optimum torque peak and a nice torque curve that would be knock resistant because once this happened I knew that I was anywhere from 3 to 5 degrees away from running into knock. This method works well for cars that a FI but lower compression, it will not work as well for high compression motors as they can reach knock threshold before MBT is fully reached (i.e why you would run race gas). From there it is alot easier to draw a conclusion where your motor will like its timing/AF ratio and makes its best power most importantly, SAFELY. All this is in consideration ou know a target boost level and from there you can adjust it accordingly.
After all of the years of tuning a car on the street/strip I will never go back there to find a cars full potential (once again especially on pump gas). The way I look at it is if you spend this much on a car why not make sure your tune is spot on in a enviroment that is perfect for it, the dyno. I think the $200-250 for 2 hours would be well spent in knowing your cars potential and then getting it to work the next day
. Just my 2 cents....
The dyno is the place to be for the simple facts of consistency and predictability. For any car that is considered a daily driver you really are shooting to find the motors MBT and nothing more. On a dyno it allows you to find this fairly easy and in the most safe enviroment possible. Finding MBT is a comprimise of both A/F ratio and timing (especially on pump gas), not a extreme amount of timing or a really lean A/F ratio.
My method of tuning a race gas map was to first have a optimized pump gas tune that I had known was good. I tuned the car for pump gas first dialing in the A/F ratio across the rpm range with a known safe timing map. Then I would increase the timing either 1 or 2 degrees at a time making any small adjustments I needed to the A/F accordingly. I would increase timing untill I saw the torque curve start to drop and/or lost peak torque. This would allow for a optimum torque peak and a nice torque curve that would be knock resistant because once this happened I knew that I was anywhere from 3 to 5 degrees away from running into knock. This method works well for cars that a FI but lower compression, it will not work as well for high compression motors as they can reach knock threshold before MBT is fully reached (i.e why you would run race gas). From there it is alot easier to draw a conclusion where your motor will like its timing/AF ratio and makes its best power most importantly, SAFELY. All this is in consideration ou know a target boost level and from there you can adjust it accordingly.
After all of the years of tuning a car on the street/strip I will never go back there to find a cars full potential (once again especially on pump gas). The way I look at it is if you spend this much on a car why not make sure your tune is spot on in a enviroment that is perfect for it, the dyno. I think the $200-250 for 2 hours would be well spent in knowing your cars potential and then getting it to work the next day
. Just my 2 cents....
Last edited by fid; Sep 25, 2007 at 03:21 PM.
I've heard this before too.
On the pump gas, is that 11:1 across the rpm range or just at redline?
The reason I ask is that my AFR's start out near 15 and roll down under 12 @ 5k and about ~11.5 @ redline. I'm a newbie to learning AFR's and all, so bear with me.
On the pump gas, is that 11:1 across the rpm range or just at redline?
The reason I ask is that my AFR's start out near 15 and roll down under 12 @ 5k and about ~11.5 @ redline. I'm a newbie to learning AFR's and all, so bear with me.
I thought I had mentioned it in this thread, but it must have been another. There is some debate about how to to do it, but my method has always been to run it richer at peak torque and lean it out gradually at high rpm. The idea is that at peak torque, or peak airflow per revolution, cylinder pressure is highest, and therefore more fuel to control knock. As cylinder pressure, airflow/rev, and the ECU's percieved load drops with rising RPM, you can afford to lean it out some for a little more power.
For example, 11.0 at peak torque, holding to 4500 or so, then gradually leaning out to 11.5 at redline. Or set it for 11.5 across the board, and then just richen up the 3500-4500 area, I've done it both ways. These motors are more tolerant of leaner mixtures on pump gas then DSM motors, without a doubt. But the power gain was still always pretty low for me, so 11:1 is still a good recomendation for a typical tune IMO.
What I've been finding most recently with the stock ECU is that the partial boost areas are too lean for my liking. Foot braking on the highway last night to hold boost at 5, 10, and 15 psi showed that the ECU did go into open loop, but didn't add enough fuel. Doing a little work in this area has always helped me prevent knock on the spoolup from ruining the rest of the pull. This is especially important on the street where you can roll into it at any RPM, not the same 3000 or so you always use on the dyno. Pick an RPM, foot brake to hold the RPM, and adjust the load with the throttle, not unlike a load bearing dyno (safety first of course, don't be stupid about where/when you do it). I think this area of stock ECU tuning may be largely overlooked by the average user, but I'm still new to that particular field.
For example, 11.0 at peak torque, holding to 4500 or so, then gradually leaning out to 11.5 at redline. Or set it for 11.5 across the board, and then just richen up the 3500-4500 area, I've done it both ways. These motors are more tolerant of leaner mixtures on pump gas then DSM motors, without a doubt. But the power gain was still always pretty low for me, so 11:1 is still a good recomendation for a typical tune IMO.
What I've been finding most recently with the stock ECU is that the partial boost areas are too lean for my liking. Foot braking on the highway last night to hold boost at 5, 10, and 15 psi showed that the ECU did go into open loop, but didn't add enough fuel. Doing a little work in this area has always helped me prevent knock on the spoolup from ruining the rest of the pull. This is especially important on the street where you can roll into it at any RPM, not the same 3000 or so you always use on the dyno. Pick an RPM, foot brake to hold the RPM, and adjust the load with the throttle, not unlike a load bearing dyno (safety first of course, don't be stupid about where/when you do it). I think this area of stock ECU tuning may be largely overlooked by the average user, but I'm still new to that particular field.
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David Buschur
Evo Engine / Turbo / Drivetrain
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Jun 22, 2008 06:20 AM
