Page 1 of 1
X-Tau and a very big cam
Posted: Fri Jun 30, 2006 5:45 am
by whittlebeast
The motor I am tuning now idles at around 950 in gear and 1500 out of gear. The cam is huge. About 80 KPA at 950, 55 KPA at 1500. The X-Tau appears to cause a huge hunt for idle speed when on. Is it ok to just zero out all the X-Tau valued below say 1200 RPM Do I need a 1200 cell and a 1250 cell to make the transition fast from zero X-Tau to normal X-Tau. Right now it is reasonable on normal TPSdot only. Do I back some of that off to say half when I turn on X-Tau. This thing get about 5 MPG so...experimenting is a little pricy.
AW
Posted: Fri Jun 30, 2006 6:53 am
by grippo
Andy,
You can' t set tau =0 because the code divides by tau - it will force itau to 1 no matter what you set. 1 is the lowest value. It may be we need a special test to turn tau off if the tau at the rpm, map you are at is set to 0, but I don't know how things will react if you move back and forth between a tau = 0 and tau = 1 situation. If tau = 1 doesn't help, then we may have to experiment - after I solve the flash burn/ wheel decode problem.
As far as reducing tpdot AE when X-tau is on - I suspect a mix of the two will be optimal - that's what lance found. We just don't have anywhere near the data base to say this definitively.
Posted: Fri Jun 30, 2006 6:59 am
by whittlebeast
All I know is when I turn on X-Tau the X-Tau gauge hunts back and forth and so does the idle. The table is I think default and the X is set to like 30 Have not realy tried other things as I was fighting a different issue at the time and ....
AW
Posted: Fri Jun 30, 2006 7:58 am
by whittlebeast
Is it 1 or .01 that is the lowest that Tau can be set to? The numbers in the table go from about .33 to .01 as I remember.
AW
Posted: Fri Jun 30, 2006 5:57 pm
by grippo
Andy, I'm sorry I'm used to looking at the code where tau is in secx100 so 1 is .01in MT. Use .01 as the lowest value of tau; you can and should also lower X. I would lower it to 5 or 10 % and lower the taus near idle to .01. If this is still causing problems then I don't think X-tau is going to help in the idle region. If you are basically happy with the tpsdot AE except for maybe 1 or 2 places thaen see if X-tau helps there. If so, then we can try a code mod that will allow a 0 tau to kill any fueling enrichment in the idle region but leave things as they are in the region where it helps..