it has been said that using higher octane while n/a status is no good cuz the ecu can tell and changes things around...

can sumone explain this in more detail for me.. does the ecu add a lil timing, mess with the fuel, or what??

i know about detonation, and that since our cars run rich stock, it shouldnt matter. i would just like to know the exact things the ecu does to compensate for the higher octane gas...


what happens, or is the result of the ECU change when you run with higher octane and an AFC?? since the afc sets the fuel, does the ECU still do other things to offset the increased octane??

fill me in porfavor, tia

03 srt-4 13.130@112.47mph (n2o, stock turbo, 10/2003)
now: 20g, portfueler, bpu+++ (track/dyno times tbd...)

i farted on your wiki

I think thats crap. I've ran race gas in my car and it pulled faster with more torque. It ran exceptionaly well when I was on race gas and in very cold temps (10 degree with -20 wind chill, gotta love Chi-town ) my car felt mean with that stuff in it's belly!

I did hear some crap about race gas messing up your factory valve because of slow burn rate and higher temp. Bla Bla Bla what ever.

Think about it. How could your motor tell that the fuel it's burning is burning slower? maybe if the o2 sensor readings were messed up because the fuel is still burning when it exits the ports and hits the A/F sensor.

Unless your running alcohol I wouldn't worry about it.

I think so. I didn't start datalogging until after I put on the SAFC, but it shouldn't matter. Yes, I am adding less fuel, but octane does give me more timing. However, I have never seen the ecu (95) add more than 20 degrees.

I'm not sure if without the SAFC, if it gets to 20 on 87 octane (because theres more fuel to prevent detonation), and never advances beyond that. Maybe I'll start experimenting. Ask around your local chapter to borrow an OBDII datalogger and check the timing differences between low and high octane.

-George

bump.... wat ive gotten so far is what has been posted to this thread, and that our cars are tuned for 87 octane....

thankyou for your posts, but im still lookin for more insight.

tia

03 srt-4 13.130@112.47mph (n2o, stock turbo, 10/2003)
now: 20g, portfueler, bpu+++ (track/dyno times tbd...)

i farted on your wiki

Nobody has seen more than 20 degrees of advance from what I've read opf those who datalogging. The Neon ECU that will take advantage of premium fuel more, Will get as high as 25 degrees advance. The AFX race computer for the Neons (and hopefully soon for us) will go as high as 30 degrees advance.

So yes our ECU seems to be set for 87 octane. But I run premium anyway. I have an ignition amp that at lower rpms ruuns 10 degrees spark and a much stronger spark at higher rpms. Ultimately timing control is needed to take full advantage of higher octane fuels.

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i don´t know much about us.ecus, butjapanese and european ecu´s are going up to 40 degrees ! i have read it out with the original "mut2".
40 degrees at 98oct in stock engine and no boosters or something else.
can somebody post the partnumber of the us.ecu please and i will check if i find differences to my one

4g63n/t
drive fast and kick ass!!!!
excuse my english!
NOS-wet-kit,s-afc,underdrive pulley,remus-exhaust
225 goodyear eagle f1,8x18 OZ racing rims
turbo gs-t

Ummm, OK. Do you mean no one STOCK has seen more than 20 deg?

I am looking into exporting my logs from my palm logger into a usable format. On one particular run I hit 23 degrees in 2nd gear @6.5k rpm and 20 deg in 3rd @6.4k rpms. This WAS with the SAFC leaning out my 95 ecu at about 11% since my 6k and 7k settings were -8% and -14% respectively.

I didn't notice any change in the timing when lowering my settings to around -5 and -11 in that range, but that's not to say I wouldn't get any where near 20% to that at 0 and 0. When I find the export utility I will go out for an all 0 safc run and let you guys know. I don't think I will be able to get down to 87 octane anytime soon, however.

-George

i can´t speak for stock american ecu´s but my is going up to 40
but i use 98 octane fuel ( must use mitsu say it in europe)

4g63n/t
drive fast and kick ass!!!!
excuse my english!
NOS-wet-kit,s-afc,underdrive pulley,remus-exhaust
225 goodyear eagle f1,8x18 OZ racing rims
turbo gs-t

I've been using premium on mine since I bought it and I'm reluctant to going back to regular. I used to have a 98 Mirage and I used to put the "Plus" fuel in. Then one day, I was short on cash and put regular in, 5 mins. later, CEL came on. Took the car to satan, and he said the(i don't remember the exact name)was dirty. They cleaned it up and cleared the error. In other words, I'm not sure about going back to 87 octane cause my car might start acting up.

Here are two screen shots of a datalog I did with the OBD-2 datalogging software and interface. Both shots are of the same data, just different display methods. Take note of my spark advance; labeled "SPARK ADV" in screen shot 1 and "SPKAD" in screenshot 2. This was on 93 octane.

NOTE: I did not post the pics directly into my response. Just click on the below link and you can view both screen shots.
http://home.columbus.rr.com/klipz/images/obdscreenshots/




Eric Madden

so u were gettin forty sum degrees advance?? wtf,

thanks for the info allz! i am still tryin to learn about the octane/ecu crap and will hopefully get my pocketlogger software soon.

03 srt-4 13.130@112.47mph (n2o, stock turbo, 10/2003)
now: 20g, portfueler, bpu+++ (track/dyno times tbd...)

i farted on your wiki

But, was this at WOT? I see >35 degrees too, just only when I'm cruising.