Is it correct to assume that there is more ethanol in winter fuel? My 924s has a programmable EDIS ignition in it from a 93 escort wagon. I have had it mapped to run 93. In the past 87 would cause it to run rough to the point I suspected knock (never actually tested / listened).
Now fast forward 2 years and about 3 weeks ago I had no choice but to put 87 in it and it ran fine. In fact it seemed to run better than the 93. The only mechanical difference is I have changed plugs. I went to a resistor plug with the same heat range (stock 924s plugs are non resistor) and I had a FPR going bad that finally failed (new one installed about 3 weeks ago). BTW the FPR failed at full fuel pressure with the new one I am getting much better millage.
So have things changed in the last 2 years with fuel making 87 more knock resistant? Is winter gas more knock resistant (more ethanol). Is it the resistor plugs? Are the "voices" convincing me that I can run 87 and save $.20 a gallon?
dean1484 wrote:
Is it correct to assume that there is more ethanol in winter fuel?
No, it's always less. Since Ethanol doesn't like to evaporate cold, it's always lowered for the winter.
My 924s has a programmable EDIS ignition in it from a 93 escort wagon. I have had it mapped to run 93. In the past 87 would cause it to run rough to the point I suspected knock (never actually tested / listened).
Now fast forward 2 years and about 3 weeks ago I had no choice but to put 87 in it and it ran fine. In fact it seemed to run better than the 93. The only mechanical difference is I have changed plugs. I went to a resistor plug with the same heat range (stock 924s plugs are non resistor) and I had a FPR going bad that finally failed (new one installed about 3 weeks ago). BTW the FPR failed at full fuel pressure with the new one I am getting much better millage.
So have things changed in the last 2 years with fuel making 87 more knock resistant? Is winter gas more knock resistant (more ethanol). Is it the resistor plugs? Are the "voices" convincing me that I can run 87 and save $.20 a gallon?
First- misfire is not knocking. You can get a lot of knock and outside of the sound of a ball peen hammer being punded into the engine, the engine will run fine. More than likely what was happening was the difference in evaporation causing the misfire. The big knob that is adjusted between winter and summer is how easily the fuel evaporates- the fuel needs to evaporate easier in the winter, but is made harder in summer to keep evaporative emissions less. So I would guess you found a source of fuel that considered hes fuel, where it takes a lot to get it to evaporate.
As for knock and winter- with the lower ambient temps, one of the leading reasons for knock is significantly reduced- hot air- so you CAN run lower octane in the winter with a lot less risk. My Miata will give me some tip in knock in the heat of the summer, sometimes even on 91- but wintertime, I suspect I can tolerate worse than 87.
Anyway- next time your car misfires- if you can get high speed a/f in the exhaust, I suspect you will see a major hole in how it's running. That's what we see, for sure. And, without a doubt, it's a major pain to work around. It's one of the ways I wish the Federal emissions requirements were the same as California's- the tighter fuel spec is far better for overall emissions.
Good luck!
Eric
Non-resistor plugs are getting to be a pain to find. I found a set of NGK non-resistors as bosch seems to have stopped selling them at least for my car.
If you have to use resistor plugs you are suppossed to use non-resistor wires, but I really don't know what the impact of resistor plugs and wires being used is.
I am using wires that are for the EDIS system (for a 94 mustang V6 with EDIS)
The plugs the same heat range as the Porsche plugs. They are the resistor plugs used in the 94 mustang. I have gaped them to the EDIS ignition spec.
