KrisR

iTrader: (2)

Hello all. Its been awhile since I've posted on this forum. Been out of the LS1 loop for awhile. I just picked up a 2000 C5 FRC with a TSP 228R cam, PRC ported 5.3s, longtubes, LS6 intake, etc. Currently tuned for E85.

The car generally drives and idles nice, but occasionally will pop/backfire out of the exhaust randomly at idle. Long term fuel trims are in the -4 to -5 range at idle and STFTs hover near zero. The car only has around 15-16 degrees of timing at idle. Could it be that it wants more idle timing to fully burn the fuel?

It has between 26-28 degrees at WOT, which also sounds a little low to me for E85.

Thoughts? Thanks!

EDIT: plugs are TR6s of unknown age, and wires are some Moroso ones, also of unknown age.

Rhino79

iTrader: (7)

From what I have seen during my e85 tuning is that at low to mid load/rpm areas, the e85 and 93 oct timing will be close to the same, maybe slightly higher on e85. WOT does sound low, but I have tuned some setups that made max power at 23* at wot which would be about right for the timing you have on e85 if that was the case. Sometimes small chamber heads on larger displacement has really high dcr and it requires less timing than normally needed on a stockish chamber/displacement setup.

I would try to bump the idle timing up to near 20* and see how it likes it.

rmata

iTrader: (34)

Try around 20-22 degrees at idle. Then start raising wot 1 degree at a time until it knocks or you feel like it's no longer making any power. A dyno would be helpful