Thread: distributer curves?

Tweet

I would like a little understanding on the curve of a distributer and what makes them relative to performance applications. Tell me anything!

The advance curve controls the rate and amount of timing advance in the ignition. Different engines like different advance. No one curve is going to work on every engine....

Some engines like the advance to come in early and a a very quick rate, others want the advance to start at a higher rpm, and come in slowly and smoothly....then blown, turbo'd, and NOX engines have to have some of the advance taken away as the rpm increases....

Josh---main thing is that you won't be able to start it with the amount of advance that makes the best power/economy--it will kick back against the starter--so you need a means of accomplishing one of two things-----retarding it from the power setting so you can start it or advancing it from the starting position so it makes some power---the curves thing just civilizes it a little

So, what would you call an aggressive curve?

an agressive curve???? its not a matter of being aggressive----its what you want out of your engine--for me? I'll take a crank trigger or locked out dist and only turn on the ignition after the engine has turned over a couple of times or use a MSD starter retard switch

If you have the rest of the engine to handle it, cam, light reciprocating mass, excellent fuel flow and air/fuel distribution, correct rear gearing, etc., then you can curve the distributor to get full advance in quickly, say by 2300 rpm. Your compression ratio also has a lot to do with advance rates and total advance... A 10.0:1 motor with the wrong cam events is going to detonate like crazy with 36 degrees advance. A light weight car with tall (numerically) gears will accelerate hard with the same fast rate and high total advance, but it depends on a lot of other things in the engine and drivetrain. The total advance number and the rate at which the timing advances is a fine tuning method. When done correctly, it will maximize the performance potential of an engine.... But, if you put a fast rate in the wrong setup, the car can have a terrible bog, and the engine can rattle itself to death from too much timing coming in at too fast a rate.

The advance curve is nothing more then a fine tuning issue. Optimizing it and tweaking the rest of the engine is probably only going to result in numbers that can be seen on a dyno or a time slip..... On the street, tuning the advance curve in the distributor correctly can avoid detonation, but it has to be done too match the rest of the components in the engine and not as a cure all for low or poor performance.

In one of my sbf's, running in a 2400 pound 5 speed car on E-90 fuel, with 11:1 compression, I ran 35 degrees total advance with no vacuum advance and all the timing was in by 2200 rpm......and the MSD would start pulling some of the advance out at 6,000 rpm. This same setup in a heavy car on the street running pump gas would death rattle itself to pieces!!!!!

advance should be all in before the front wheels come back down after the wheel stand