Crank Reference Angle/Rotor Phase

[dhegge]

Guys,

Could some one please explain to me the proper way to setup the Crank Reference angle and Ignition timing for a FAST/SFI module? I have been told that all that really matters is that the timing idle retard be zero'd/disabiled and that the light agrees with the ECM. But I suspect there is more to it than that.

Also,
I believe I may be having a Rotor Phase problem that is causing eronous timing readings and spark scatter.

I am using an MSD ignition that has both the Cam Sync and Magnetic outputs from the reluctor since I don't have room for a Crank trigger.

Doug
375CI Twin Turbo (1008HP at The Crank/w Ignition Problems)

 

[bobc455]

Doug-

If the ECM shows the same as the timing light, then that is set up properly, at least as far as the crank reference angle.

As far as the rotor phasing issue you describe, let me describe a problem that I had and it's solution- you don't describe your symptoms in detail, but from what you do say it sounds like what I went through.

My car would idle fine, etc., but would run funny with more advance. Turns out that the spark would jump to the wrong terminal in the distributor, causing all kinds of misfiring.

For me, the solution was to offset the distributor 15 degrees from actual- in other words when my ECM says 0 degrees, I'm actually at 15 degrees. At WOT the ECM says 21 degrees, that's actually 36 degrees at the engine. That 15 degree offset brings the rotor nearer the proper elecrode so that it fires on the correct cylinder.

My crank reference angle is set at 60 degrees, but in theory it should be set at 45 now.

I am told that if I switch to a different distributor that uses a larger cap (mine is about the size of a regular points-style cap), that I wouldn't have to offset the 15 degrees like that. But then I'd be spending several hundred dollars to fix a problem with no symptoms. Granted that it's a band-aid, but it works.

I'm not saying that's the fix for your car, but it's something to consider.

-Bob Cunningham
bobc@gnttype.org

 

[Craig Smith]

Bob,

A much less expensive solution to your problem would be to offset the reluctor wheel in your distributor 15 or 20 degrees so that you could have the proper reference angle and correctly phase your rotor. Many distributors have the reluctor wheel pinned in. Knocking the pin out and redrilling it works for many people.

It's a common problem. Most distributors have the reluctor phased with the rotor, assuming you will feed the pickup directly to an ignition system. It can be something to deal with when a computer is controlling the timing. The more power you make, the more likely it is to be a problem. A bigger cap is a better cap, I say. But if spending the dough on a new distributor doesn't have much appeal right now, this may do the trick for you.

Hope this helps.

 

[dhegge]

Reverese Wires Caused Phase Problem

Final Chapter/Update

As it turns out the wires coming out of the distributor where reversed. e.g. the reluctor pickup polarity. Once we flipped
the wires everything came in perfectly. We are funning like 65 degrees of reference angle but it is phase on the mark at
30 degrees the motor sounds very happy! Thanks for the tip Jim! and Jack/Racetronix also suggested this on this board. FYI
Bob you may have this problem?

As for the phaseable rotor the only think I can find is a pro-cap and I don't know if that wll work with the Dual Sync/EFI
distributor or not. Any ideas? I guess in a typical application MSD distributor and no ECM people don't really care they just adjust the housing until the timing is where they want it and don't worry about the fact that the Polarity is actually wrong!

If you want to find ou if your polarity is correct just flip the wires the correct position is the one with the least amount
of retard according to MSD.

Thanks for all the Help,
Doug
One more problem down, who knows how many to go?

 

[dhegge]

Confimation

Craig,

I received this snippit from Dan @ White Racing RE phasing problems: Could you please eloborate.

"FAST told me that improper phasing will also cause an electronic "delay" in the front end of their electronics thereby causing the timing to change as the engine revs."

Thanks,
Doug

 

[TurboTR]

That applies to having the VR pickup polarity backwards too. I think there are maybe some Hondas running around like that

TurboTR

 

[Craig Smith]

What MSD considers to be positive and negative is opposite of what we consider it to be. If you run what they say is positive to the positive lead on the FAST harness you will have a problem. Follow our wiring instructions and you'll be OK.

Glad everything is worked out!

 

[dhegge]

RTFM

Doh! Okay if you read the fine print I guess it does say this. I wonder how many other people are running with the incorrect phase surely I can't be the only one who did this Thanks for all the help and such a great product. Back to Dyno tuning we are going to shoot for 1200HP up from 1000HP today now that we finally have the timing correct