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1500 Timing Curve
- Thread starter Morris
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Morris
Yoda
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I mapped my advance using a utility created by someone in the Megasquirt community. My low end advance goes as high as 55! The map I have works pretty well for the most part, but I am getting some thunking on hard accelleration out of 2nd and 3rd. Car runs super smooth (even with my pesky valve problems) but kinda lacks low end git.
RobSelina
Jedi Warrior
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55 degrees! wow!
I suspect that's part of your problem. Dial it back so you're in the 10-12 degree range at idle and up to 30 degrees at 5000 RPM. It can come on pretty early based on how my car runs. 24-28 degrees at 2500 RPM doesn't seem to cause any predetondation....
I suspect that's part of your problem. Dial it back so you're in the 10-12 degree range at idle and up to 30 degrees at 5000 RPM. It can come on pretty early based on how my car runs. 24-28 degrees at 2500 RPM doesn't seem to cause any predetondation....
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Rob,
I certainly agree. If it really is 55 degrees I would expect burned valves, melted pistons, & such. 24 to 28 crankshaft degrees at 2,500 rpm & the remaining advance to 34 degrees at 3500 to 4000 should be very close to optimum.
Morris,
The total advance under load at what ever rpm should be limited to around 34 degrees. Beyond this point you will likely get "silent" detonation. You won't hear it but tremendous damage can be done. You could go a little more with a "slow burn" chamber design, & a little less with a 'fast burn" chamber.
With 55 degrees, it may lack "low end git" because the timing is so advanced that the combustion pressure is trying to drive the piston back where it came from.
The equivalent of 55 degrees at very light throttle settings might be reasonable, as long as it retarded 20 degrees or more when load was applied. That's what a vacuum advance does.
D
I certainly agree. If it really is 55 degrees I would expect burned valves, melted pistons, & such. 24 to 28 crankshaft degrees at 2,500 rpm & the remaining advance to 34 degrees at 3500 to 4000 should be very close to optimum.
Morris,
The total advance under load at what ever rpm should be limited to around 34 degrees. Beyond this point you will likely get "silent" detonation. You won't hear it but tremendous damage can be done. You could go a little more with a "slow burn" chamber design, & a little less with a 'fast burn" chamber.
With 55 degrees, it may lack "low end git" because the timing is so advanced that the combustion pressure is trying to drive the piston back where it came from.
The equivalent of 55 degrees at very light throttle settings might be reasonable, as long as it retarded 20 degrees or more when load was applied. That's what a vacuum advance does.
D