Tuning WOT a/f: linear or richen near peak TQ?
03-21-2012, 01:37 PM
#1
Tuning WOT a/f: linear or richen near peak TQ? In my tuning books, it is mentioned that a/f tuning for WOT should richen the mixture near where the engine makes peak TQ, then lean back out to desired a/f ratio.
stoich (at cruise)---power enrich on WOT (~12.8)---fatten near peak torque---lean back out for peak HP (~12.8)
But on nearly all dyno sheets I see from professional shops, the a/f is set to be a constant.
Which is the preferred method? Is there really a benefit of being a little richer for better peak torque before leaning out to ideal a/f for HP?
stoich (at cruise)---power enrich on WOT (~12.8)---fatten near peak torque---lean back out for peak HP (~12.8)
But on nearly all dyno sheets I see from professional shops, the a/f is set to be a constant.
Which is the preferred method? Is there really a benefit of being a little richer for better peak torque before leaning out to ideal a/f for HP?
03-21-2012, 06:37 PM
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I have found that most combinations want to be richer just before and at peak torque - generally around 12.5... The key is to optimize the timing and AFR to get the most torque and horsepower out of the given combination - that takes time and effort to find out what each one wants.
Also, it is important to work on getting the most area under the curve - not just the peak points. As a car accelerates, it is only at the peak points for a very short time - if you work to find out what the combination wants to make the most torque/power under the entire curve, you will have a quicker car...
There are some combinations that want a relatively flat AFR curve... or dyno graphs can be that way because the tuner is inexperienced/lazy or they are using a tailpipe sniffer wideband that isn't accurate enough to show the difference...
Also, it is important to work on getting the most area under the curve - not just the peak points. As a car accelerates, it is only at the peak points for a very short time - if you work to find out what the combination wants to make the most torque/power under the entire curve, you will have a quicker car...
There are some combinations that want a relatively flat AFR curve... or dyno graphs can be that way because the tuner is inexperienced/lazy or they are using a tailpipe sniffer wideband that isn't accurate enough to show the difference...
03-22-2012, 10:48 AM
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IMO - most of those charts you see coming out of shops are flat because it's all about the money...and time = money. Tuning doesn't bring in the big bucks for a shop. So, getting cars in and out quickly is how they avoid taking a loss on the job. Sad, but true...as I said, IMO.
Personally, I think of richening up at peak torque to be a bit of a safety feature. If you end up gaining a little from it as well, awesome. From my understanding, that's when cylinder pressures are highest. Having a little extra padding in that part of the curve is always a good idea.
Personally, I think of richening up at peak torque to be a bit of a safety feature. If you end up gaining a little from it as well, awesome. From my understanding, that's when cylinder pressures are highest. Having a little extra padding in that part of the curve is always a good idea.
