Pupshot gets flushed with SD? Is this true for LS2 (E40) as well? Any way to recoup it or compensate without going back to MAF? I was wondering why the GTO I'm tuning feels soggy and goes lean on tip in...Originally Posted by Chris@HPTuners
Pupshot gets flushed with SD? Is this true for LS2 (E40) as well? Any way to recoup it or compensate without going back to MAF? I was wondering why the GTO I'm tuning feels soggy and goes lean on tip in...
Its the transient fueling not "pumpshot". The LS1/LS2 uses an "airshot" as Chris said.
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Apparently not when you convert to SD?
It still uses it. But like Chris said it's complex. Transient fueling has to do with how much fuel goes onto the port wall and how fast it evaporates or moves past the valve.
BTW: I've used it on a couple magnacharger cars and on a few APS twin turbos to settle down some lean transients in SD mode.
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So what does Accel/Decel ratio and Maximum Mass do in this equation?
That's one I haven't played around with yet. Hoping to get some time to experiment.
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Oh, ok. What was he referring to not working without the MAF then?
Dunno. I've had good luck with it. Hope I wasn't deluded...LOL
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Sticky!
I call STICKY!
ok im at such a loss at what to do with the lean spike. I have a 122hh on a ls2 GTO E40 ecm. Im on the standard OS with a 1 bar and using MAF for fueling, I got my AFR right on the money except for where it spikes. anyone wana take a shot at it?
Hmm... not consistent is it? Went rich like it's supposed to in the 2nd screen shot but lean in the 1st. Try making the impact factor higher. Try a 40% increase as a trial on the 100 Kpa line and blend down to 80 Kpa and see if it improves the lean shot.
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soo.... i discovered that irridium plugs arent the best for my setup.... i threw some TR55's in and the lean spike basicaly went away along with now its idleing much better than before. Thanks for the help though
AHA! Another mechanical solution to a mechanical problem! Thanks for posting up your solution!
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I discovered another slip on my part.... i didnt match the highest cell on the Low Hz MAF to the lowest cell on the High Hz MAF..... its running extremely well now
Since I got my new motor, the transient fueling has been extremely erratic - both in sd and maf only. It goes like this - rich dip on map decrease, lean spike on map increase. Do I lower the evap table or raise the impact factor table?
Try raising the impact factor. You shouldn't need to mess with the evap table as the gasoline evaporates the same regardless of port wall impact.
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Hmm.. ok.. damn i wonder if its tuned for 10% eth blend gas? Probably not! I just thought that my new motor would have different evap conditions.. I will try increasing the impact factor. How much % would be a good starting point? Will this take care of both the rich and lean swing? Pretty sure it will, just want confirmation! Thanks!
2006 Trailblazer SS - Stalled, Cammed, Tuned, Turbo'd, Built, and Stroked.
Runs on cash, blood, sweat, and tears...... and 93 octane.
2007 Cadillac STS-V - Stock.
Since this is kind of a new area for most you will have to experiment and report back.
Let us know!!!
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The Impact factor gain table references the MAF. What if you are running in SD? In my case, this table is set to 1 across the board.. Regardless, if I were to eliminate the MAF (rather than setting the fail freq to xyz), what would happen?
Why isn't it recommended to adjust the evap factor in conjunction with the impact factor. I understand it makes no difference whether or not impact increases by 2x and the evap stays the same versus impact by x and evap -x. Still don't feel right fudging values.
I have been trying to solve a lean spike on map increase and its driving me nuts. Even when driving normally the A/F sways lean to 'normal'. I'm running open loop. Its as if its referencing two different values, the MAF hz table and then lean spiking via transient table. Its my understanding that the transient table gets its fueling values via VE. Is this correct?
Last edited by Blades; 11-19-2008 at 10:01 AM.
2006 Trailblazer SS - Stalled, Cammed, Tuned, Turbo'd, Built, and Stroked.
Runs on cash, blood, sweat, and tears...... and 93 octane.
2007 Cadillac STS-V - Stock.
Even in speed density mode, the PCM is still calculating a g/cyl airmass which is then turned into g/s based on RPM and number of cylinders. For transient fueling, it doesn't really matter where the g/cyl or g/s number came from (both MAF and VE can provide both numbers!), as long as it's correct. If your VE table or MAF transfer isn't correct, you have little hope of getting the transient fuel tables correct.
The amount of fuel deposited on the wall is higher when there is lower absolute airflow in the ports. Likewise, evaporation rates increase with increases in both temperature and airflow.
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