Category Archives: Street Cars

Naturally Aspirated Ethanol Gains?

For those interested to know how E85 goes on a high comp NA LS motor, have a read.

After upgrading my Corvette ECU (2009 to a 2012) & putting in some LSA injectors & a flex fuel sensor, I figured I should run it on the dyno to check power, air-fuel ratio, since I just used GM injector data from a factory LSA car & then used the short term fuel trims to get it in range while cruising around on the street.

Anyway, ye old stock LS7 with it’s 11:1 compression, has a rather aggressive factory timing map & uses other tables to pull timing for air & coolant temps. however it still ends up using the knock sensors to pull additional timing.

Since I don’t like the idea of the motor rattling, then pulling timing, my timing map starts with a good 3-5 degrees less @ WOT where it matters with the slightest bit of knock being detected (mainly to see if adding E85 would remove it) Result = 453-455whp (17 degrees & 5400rpm) on Pump 98 Octane.

I then loaded in 22lts of E85 into the tank, ran car until ethanol content stayed consistent at 36%. Ran same timing as pump & seen a 10hp increase up top where it was previously registering knock – 464whp.

Next I added 2 degrees across entire map, now making 469whp, but picking up more power from 3600-6200rpm. Still registered slight amount of knock above 6200 nothing concerning but mentioning it as timing is still only 20 degrees at this point.

Putting in additional degree of timing made no more power as it detected more knock & thus pulled it back out again.

62% Ethanol Update

Timing wise, the engine took 1 more degree of timing then the 36% from the other day, so played with the fuel. The 490 & 499hp runs were done at a faster ramp rate (Shoot8F).
Total gain from Pump98 ~ 30WHP.

Total Ignition Timing