how much timing?

[Shannon Clark]

Here is my timing map. Its set up KPa vs RPM. For those that dont know 10 KPA=1.45 psi. I am running about 8.5 to 1 compression and 30 psi boost. What do you guys think about total and curise timing? I am thinking about bumping it up some.

[ericbowling]

Heath can probably jump in on this one but as far as comparing Timing on Gas and Timing on E85 you may be able to get away with a little bit more on E85 than gas but I run the exact same timing that I ran on Gas. Hope this helps..

[Heath Daniel]

shannonclark the best thing I think to do here is just tell you how we have ours set-up. We are running a 355 with 8.5:1 static compressions as well but with a 6-71. We don't run nearly as much "boost" (back pressure in the intake manifold) as you do but we are still moving a lot of air and fuel. Our total timing is set at 38 degrees all in by 3000 rpm (old school mechanical advance). I have heard of other combinations actually being able to take timing out and picking up after they converted to E85 but if we run any less than 38 total ours runs like a pooh. We have an (old school) MSD universal boost timing retard that is set to pull 1 degree of timing out per pound of boost starting at 2 pounds up to a total of 12 degrees. The most boost we have made is about 9 pounds so that works out to a total timing of 24 degrees at max boost for us. I don't know if this helps you any. Pardon my ignorance but I just don't know enough about what you are working with to really make any recommendations as to how or how not to set it up. What I do know about E85 is that ethanol is slow burning but, and here is the kicker low octane gasoline is fast burning. E85 is of course part low octane gasoline which lights off first in the combustion process. The gasoline burning is what gets the ethanol to start it's burn, not the ignition timing so that is why you don't find much variation in timing from a straight gasoline setup. If anyone else wants to jump in on this one they are more than welcome. I'm going back to turning some screws and changing some jets and KPA my butt out of this one for now.