88_vette

Ok quick run down. I'm tuning my engine/burning my own chips. I've gotten pretty far, and I'm pretty much done with the fuel tuning. Timing is another story.

I started with the LT4 timing curve. I have a mini-ram and figured this would put me close to that style of intake. It runs really well. Problem is I get a little poping in the exhaust and I guess what seems to be some back fire. Nothing major but noticable. I can change the timing and it goes away and the car seems to run just as well. Why would timing cause this? I had a SR before and never had this issue when playing with the timing.

Also this base timing thing. I had it at 6* and told the ECM what I wanted the timing to be and even programmed the chip with my base timing so it could do it's math. Well I noticed a power loss. I put it back at 8* and then chaged the chip to reflect this. SO in the end I should have ended up with the same timing. However the performance increase was noticable. Why would the base timing effect it if in the end the overall timing was the same??? :crazy: :crazy: :banghead: :confused: :confused:


[Modified by 88_vette, 10:36 PM 4/23/2004]

CorvetteZ51Racer

The timing can cause the popping if the burn isn't far enough along when the exhaust valve opens. I assume that when you change the timing to get rid of that, you're advancing it slightly.

As for the 8* vs 6* thing...are you simply changing the base timing in the program and not on the distributor? If you don't change it in both places, you are not ending up with the same timing.

Vett-eight-nine

S.O.S.
You mean, advancing the timing at the distributor alone, won't end up in the change taking place? My car disagrees. Please clarify
"If you don't change it in both places, you are not ending up with the same timing"[/QUOTE]

65Z01

The base timing set at the dist is an absolute but isn't the timing curve dynamic, i.e. depends on sensor data?

If so, setting "base timing" in software wouldn't be quite the same as doing it mechanically.

88_vette

maybe that's it. I felt a difference when the base time was changed mech. I guess this not being ECM controled it took effect no matter what the ECM wanted to do.

I was thinking along the lines of that unburned thing, but really didn't know if it made since.

Thanks guys.