vl5150

I just installed these a few weeks ago on my 1990 and found a few things while logging the factory computer and using my wideband.

My VE tables were all off and needed modification. The factory AE was causing a lean spike to 15.2:1 before dropping down. My PE was still factory and was still too rich (~11.0-11.5:1) as has been reported here before.

So I have the lean spike mostly handled and have the PE in the mid 12's and that seems to be a good area for E10 gas. I dropped the PE mode on the TPS 7% and it really likes that as well.

My target for the E10 on my tune is 14:3 to one. Stoich for E10 is lower and my knock counts went through the roof with 14:7 target.

My latest log showed 8 knocks in a 40 min drive. So far so good.

bjankuski

Just a side note: The car always targets Stoich in closed loop and you cannot target an actual AFR, that is determined by the fuel itself. The O2 sensor is looking for the correct ratio of O2 in the exhaust and will adjust the fuel trims (BLM) and (INT) to achieve that ratio. All you can do is adjust the VE table to minimize your BLM correction.

vl5150

My bin has a parameter called stoichiometeric air fuel ratio. It was set for 14.7 and that was what was showing up on the wideband (along with knocks using E10). When I changed this to 14.31, the wideband was showing 14.2-14.3 when at cruise. This dramatically reduced the knocks as well.

So this parameter looks like you're able to tell the computer what stoich is and it then corrects toward this new setting, correct? Or is there something more to this parameter?

bjankuski

The computer uses that number to determine a pulse width based on the injector size and desired AFR. After the pulse width is determined the computer adjusts the pulse width using the O2 sensor and any trims are added in and the BLM is modified. The actual AFR while in closed loop operation will be whatever the fuel you are burning actually requires to achieve Stoich operation. The car cannot operate at a commanded AFR because it does not have WB O2 sensor. If Stoich for the fuel is 14.3 that is where it will run, if Stoich for the fuel is 14.7 that is where it will run. If you dumped in E85 with a Stoich of 9.8 that is where it would try and run but it would have issues with WOT because you would probably run out of injector, but if you had enough injector and pump it would run.

The long and short of this is changing the 14.7 target in the tune to 14.3 probably did not change the AFR, what it did was adjust the amount of correction required on the BLM and the reduction in knock counts was probably related to other items, like WOT timing or fueling.

MrWillys

The o2 automatically adjusts for the e10.

Lambda 1 is always Lambda 1 no matter what you drive your car on, the o2 sensor doesn´t care if the AFR are 14,7 or 9.765... it measures the available o2 in the exhaust gases.

Taken from:

http://www.ls1.com/forums/f63/how-ru...ls1-e85-33448/