| mikels |
11-11-2014 02:32 PM |
Quote:
Originally Posted by Vince@MSperfab
(Post 579632)
Its common on RPM-MAP based ecus in race applications for the lowest MAP bins to be set at the max vacuum that you can pull while opening the throttle quickly. When you quickly close the throttle quickly at high-load, high-rpm, you can often get the MAP to dip below that value and it will cause a rich condition that produces popping and flames. You can tune it out by spreading out your MAP bins, but it will lower the resolution of your fuel tables in the normal operating range and hence isn't usually done in race applications.
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Controller is GM E67 and is using MAF primary control with parallel speed-density control. So I have seen what you are speaking of, but this is slightly different.
Flames are result of how quickly ramp out of PE (power enrichment) combined with spark control when transitioning from on throttle to off throttle to DFCO (de-acceleration fuel cut-off).
Non-issue from an engine standpoint - from a visual, well, it barks flames on lift-throttle transitions from high airflow.
While there are many changes I can make that could reduce this effect, we haven't had time to revisit cal since last development trips to Gingerman and now OUSCI. That and some of those potential changes would be undesirable such as how quickly power drops when reducing accelerator pedal (@ 950hp, when you lift, you likely really want to reduce power.....)
Mark and I were talking that we've reached point where more power is not likely to result in much improvement of lap times (never thought I'd say that.....). Ability to maintain fluid temps at this power level has been a challenge as well - but Mark is now able to run 20 minute sessions in any ambient with controlled temps and no drop in delivered power.
First 7.0L supercharged engine (for road racing) we did at Thomson's in 2009 made 780hp/830tq. We are now at 950hp/970tq (1010hp/1020tq on E85). Amazing what refinements can bring paying attention to the details.
Dave |
