This is another issue i have been playing with. Quite extensively on my 91 GTA(current driver) and a lil bit on my 91 Formula(it never ends). I can wholey understand the reasoning behind it and it has been a basis for hotrodding for years.

Every attempt i have made at bringing in the total curve faster basically results in me getting into kinda nasty detonation and when i play with and back it out the only way i eliminate it is to go back to where i started and that is to the timing curves i have more or less established as about as good as i can get(I use a g-tech for timed runs) without knock under wot conditions...

On my GTA i run about 27-28(w/ PE) degree from 4800 rpm as that is as much as she will take without entering the knock zone.

I am going under the assumption that my car would run faster if the total curve was in sooner. I have tried additional fueling thru PE, AE(just curiousity) and thru the VE table itself and retuning the region. I tried it before and during the areas i was encountering knock. I have also tried to bring the curve in at 3200(lightly) and at 3600 and 4000rpm and all my results have ended up the same. Am i missing something simple? The car runs and drives near flawlessly for me at this point and I've almost eliminated the stumble/weak pulling bottom of 2nd gear when it wont downshift into first(every stock tpi i know does this and its irritating)..

Maybe my car just likes the timing the way it is.................
thanks and later
Jeremy

 

The engine tells you what it wants.
Don't try and tell the engine what you think it needs.

The trick is to run the LEAST timing consistant with max performance. Not the other way around.

If your just looking for an out and out race engine and might be winning money that's entirely different. But for a muffled street car timing just ain't that critial.

Too much timing, and too rich always feels fast, but might not be the fastest way down the strip.

 

I've taught myself well that too much timing and too much fuel feels good but doesnt work out too well lol.....

Most of my issues were from me trying to bring the curve in quicker and advance the timing some in the higer ranges to see if it would help. Everything i tried came up with one result: knock knock knock.

I have spent a lot of time on the timing tables in this bin. Almost all of the chips have been timing table mods, changing the VE when a discrepancy was found. Once i got those 2 the best i was able i experimented with, more/less PE fueling , until i got the best runs in using a stopwatch and mph A to mph B to help eliminate wheelspin. So im fairly confident what i am running may well be about as good as she can get. (unless u want to head to IN Grumpy lol) I guess it looks like im leaving the timing tables alone for now :-)

Any suggestions as how to help in reducing the dead spot when you hit the throttle (WOT) and your at the bottom of 2nd gear? Most all TPI cars I know/tune /drive/race/etc have that incredible lag at the bottom of 2nd at WOT(where yout not going slow enuff to clip first but just hang onto the bottom of second). I have been playing witht the PE in the area along with some timing shifts at the occurence using diacom information. I have lessened the prob noticeably, but it still tends to lug at 2-3k even when wot(again only bottom of 2nd gear WOT).....


Just looking for new things to try and eliminate the factory driveability issues that bug me

thanks
Jeremy

 

whats your AE fueling multiplier at 2-3k rpm look like ?

 

AE by RPM?
Which table is that?.

 

Granted this is from a turbo motor, but look at the timing when in the normally used N/A areas. Oh, this editing in source code so there's no pretty table values, and to get to degrees timing just dividing by 3 will get you close.

If you want to run a lean cruise then you need to get into a fair amount of timing to light the charge, but if you want to keep the temps down in the chamber and reduce the chance of detonation, then you give up a little mileage for doing something like this. I went from 30 MPH in a lean cruise setup to about 27 doing this. AND I also picked up almost 10 PSI of oil pressure. With the piston being that much cooler from the lower timing, and fuel cooling (not at 14.7 AFR), the crankcase temp, and oil loads were that much less.


Map: 20 30 40 50 60 70 75 80 85 90 95 100 ; Rpm:
68, 68, 68, 68, 68, 57, 57, 57, 46, 46, 34, 34; 400
68, 68, 68, 68, 68, 57, 57, 46, 46, 46, 34, 34; 600
68, 68, 68, 68, 68, 68, 63, 57, 51, 51, 40, 40; 800
57, 57, 71, 71, 71, 68, 63, 57, 51, 51, 40, 40; 1000
57, 57, 74, 74, 74, 71, 68, 61, 57, 54, 51, 51; 1200
57, 57, 77, 77, 77, 74, 68, 60, 57, 57, 54, 54; 1400
57, 57, 80, 80, 80, 74, 68, 63, 60, 57, 54, 54; 1600
57, 57, 80, 80, 80, 74, 68, 63, 63, 60, 57, 54; 1800
57, 57, 74, 74, 74, 68, 68, 68, 63, 63, 60, 57; 2000
57, 57, 74, 74, 74, 68, 68, 68, 68, 63, 63, 63; 2200
57, 57, 74, 74, 74, 68, 68, 68, 68, 68, 63, 63; 2400
57, 57, 74, 74, 74, 71, 68, 68, 68, 68, 68, 68; 2800
57, 57, 74, 74, 74, 71, 68, 68, 68, 68, 68, 68; 3200
57, 57, 71, 71, 71, 71, 71, 71, 68, 68, 68, 68; 3600
57, 57, 71, 71, 71, 71, 71, 71, 71, 68, 68, 68; 4000
57, 57, 71, 71, 71, 71, 71, 71, 71, 68, 68, 68; 4400
57, 57, 71, 71, 71, 71, 71, 71, 71, 68, 68, 68; 4800

Getting the AE stuff correct is time consuming, but for me it's made all the difference in how the engine acts, and how much timing the ENGINE NEEDS.