BLUE TII

I've tried retarding the timing, advancing it, making it rich and lean. Nothing seems to help. The only way it will go away all the way is if I cut the fuel in those load ranges but then it will be a little grumpy once I get back on the gas.



Have you tried playing with the throttle pump settings to keep it from getting "grumpy" when you get back on the gas after leaning out those load ranges?

rotarygod

I have found a way for those with distributers to play with negative split. It is kind of crude but works well. On the distributer, adjust split to zero. Then disconnect the leading vacuum advance only allowing the trailing to remain. This will allow the trailing to advance by up to 15 degrees in front of the leading plugs. The stock system on the 1st gens have a vacuum switch that shut of vacuum to the advance below 1000 rpms so it will still idle just fine. If you didn't have this solenoid you would have 15 degrees of advance at idle. I am currently running my GSL-SE this way and it actually runs really good. Very surprising. As I get on the gas and rpms and loads increase, the negative split slowly goes away until it is at zero. It's crude but effective and anyone can try it. If you are running a turbo with a distributer, the second you hit boost it would just go to zero split but in vacuum you'll stay in negative split.

heretic

The RX-7 distributors I have played with had more advance in the trailing can than in the leading.



So, if you have static split at zero or near zero, you would be going negative under vacuum.



I wonder if the negative split you propose would overcome the lack of leading advance? Then again there is always something to be said for firing the spark plugs as late as possible.

j9fd3s

[quote name='heretic' date='Jul 27 2005, 05:04 PM']The RX-7 distributors I have played with had more advance in the trailing can than in the leading.



So, if you have static split at zero or near zero, you would be going negative under vacuum.



I wonder if the negative split you propose would overcome the lack of leading advance? Then again there is always something to be said for firing the spark plugs as late as possible.


[/quote]



playing with the turbo motors, sometimes retarding the timing helps the turbo spool up much quicker.

mazdaspeed7

[quote name='j9fd3s' date='Jul 27 2005, 09:48 PM']playing with the turbo motors, sometimes retarding the timing helps the turbo spool up much quicker.


[/quote]





because the fuel is still burning through the exhaust manifold/turbo.

coldfire

i started the negative split discussion in the other forum

http://www.rx7club.com/showthread.php?t=443709



you can look at the maps posted there, he is running quite a lot of negative split under full vac.

j9fd3s

[quote name='mazdaspeed7' date='Jul 28 2005, 07:08 AM']because the fuel is still burning through the exhaust manifold/turbo.


[/quote]



yeah. ca gas is weird, you cant run much advance before you can hear it pinging away

setzep

[quote name='BLUE TII' date='Jul 27 2005, 02:05 PM']I've tried retarding the timing, advancing it, making it rich and lean. Nothing seems to help. The only way it will go away all the way is if I cut the fuel in those load ranges but then it will be a little grumpy once I get back on the gas.



Have you tried playing with the throttle pump settings to keep it from getting "grumpy" when you get back on the gas after leaning out those load ranges?


[/quote]



Is this what you've done? I haven't tried this.