I programed in a basic timing map similar to the one you posted earlier. I can't remember if you e-mailed this link to me, or posted it on the forum, but I am looking at a printout from a web site of yours for a timing map, which I then proceded to emulate in principal, in my ECU's spark map, with mods made for the boost section of the map. It all seems to run fine, but I feel there are likely gains to be made here if I had any basis for changes. What have you done, if anything, and what does your map look like these days? Do you know of any way to personaly tune the timing map without a dyno? What would you look for in feel or sensor responses to indicate you were changing things in the right direction?

I am told the real horse power gains to made in tuning come from timing, and not fuel. Maybe from fuel too, but that is pretty straight forward considering you can simply watch your O2 sensor and know what is happening in that regard. Timing seems to be the mystery question tht is always answered with, "take it to a dyno."
Sam

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I haven't touched timing yet, I am going to wait until I get my o2 readings to match the AFR I want at that particular point so it doesn't rely too heavily on o2 sensor correction then I will tinker with timing.

I accidentally left my main switch on (leaving the MS2/v3 and edis ignition module on) and woke up to a dead battery so it may take a while. Hopefully I can recharge it, optima deep cycle yellow top but it was at 4.8V so I doubt it.

The trouble is that you need some sort of feedback to tell if your timing is optimized. With fuel you can use a wideband sensor. But with spark timing it's hard to read things directly. While you can notice if it is knocking or not, that doesn't tell you if it is making the best power (in fact, the engine typically makes best power significantly before it knocks). The only things that can tell you that are cylinder pressure readings or measuring the horsepower.

There's a few cars out there with ion sensing ignitions that can read the cylinder pressure by the behavior of a low current across the spark plug gap. I don't think the Accel DFI can do that. You could use a crank angle sensor plus a pressure probe in one cylinder, although these probes aren't cheap. I seem to remember that the typical ones used in serious engine research cost around a thousand dollars - at least, that's what I was told when I stalled an engine on a dyno and broke one back in college.

The usual rule is that with optimum spark timing, the maximum cylinder pressure occurs about 16 degrees ATDC. Also, half the fuel should be burned at 10 degrees ATDC when the timing is right. But in practice, it's much easier to measure horsepower output than it is to measure cylinder pressure as a function of crank degrees.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

Drag strip!

Lou

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Home of Slant6-powered fun machines since 1988

http://www.charm.net/~mchaney/homedyno/dynokit.htm


I've had one for a couple of years. Pretty slick

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes