Haltech rotary trailing map settings?

[gmonsen]

let me try this another way. could some of you guys just look at your "rotary trailing timing" map and go to the 2000+ rpm map accessed by hitting "N" from the main trailing timing map and tell me what your timing split in degrees is from 0 psi to 15 psi? thanks, gordon

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[MikeL]

[This message has been edited by MikeL (edited June 12, 2001).]

[tims]

starts at 12 and goes all the way to 13 at 15psi. anywhere from 10 to 15 degrees seems to work without any noticable difference. not much to be gained on the trailing side from my testing.

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Tim Spencer
Pennyweb/RealRide.com Racing

[setzep]

All this talk about "split" has got me a little confused. I understand that the split is the deg between leading and trailing but what I don't understand is why the split gets higher as boost builds (like on Mikes map). I also understand that the leading should always fire before the trailing. How do you guys have your timing set? What changes so much to cause the big split? Is it the trailing being retarded all those degrees or is it a combo of both changing (leading being advanced and trailing be retarded??)

Any incite would be great!

[MikeL]

The fuel/air mixture will burn (propagate) at a constant rate regardless of rpm.

As rpm increases, the time between leading and trailing plug firing needs to increase as there is less time for the flame to propogate at the higher rpm.

Crazy, huh? Just imagine a mixture that has to burn completely in a given amount of time. The time allowed to burn decreases as rpm increases. Giving more time between plug firings allows the flame to propagate more fully.

I hope that someone else can explain this better than I have.

Mike

[setzep]

Ok, I understand that you need to advance the timing at higher RPM's to start the fuel on fire earlier but I guess I just need to see some #'s or a graph of some sort to teach me how all this works. Does the trailing timing stay the same all the time?? or does that change with boost/rpm? I guess I'm just wondering what changes when the split changes (the leading, trailing or both??)

[MikeL]

As rpm and therefore boost increases, the timing advance is lowered.

At the same time that the advance number is going down, the trailing advance is dropping and, the degrees of split between the two is increasing.

Check out the below screen shots of a recent dyno run of mine. The first one shows the advance at 32° and trailing at 27°. That's 5° of split.

The second screen shot shows higher boost, less advance, less trailing advance AND, more degrees split between the two. At 14° advance, the trailing advance is 3°. That's 11° of split between them.

The third screen shot shows how that is set and that it did what it was asked to do.

Mike

[tims]

the split is based on the leading timing, so if the split is 10 then the trailing will always be 10 degrees behind the leading. so as the timing changes in relation to map pressure/vacuum the trailing follows along at the same differential. my map only varies 3 degrees from start to finish 10-13. Somewhere between 10 and 15 degrees seems to work the best at WOT. there is no absolute number you have to use.

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Tim Spencer
Pennyweb/RealRide.com Racing

[Cosmo Donk]

Guys, also check out the Single Turbo Forum for another thread like this one.

[setzep]

Thanks a lot Mike! That data log chart helped me out very much!. Now I can go talk about timing split to all my V-8 buddies, think they'll get it?? Nahh me neither