Ok, i've heard that we have a timing retard chip in our ECU's on the 420a. This, to my understanding, retards the timing when you put sub-par gas in the high comp 420a. My question is, a) am I utterly full of it on this one? and b) is this timing retard permanent, or how long will it take to undo the "damage" of putting crappy gas in your car?

matt

>Ok, i've heard that we have a timing retard chip in our ECU's
>on the 420a. This, to my understanding, retards the timing
>when you put sub-par gas in the high comp 420a. My question
>is, a) am I utterly full of it on this one? and b) is this
>timing retard permanent, or how long will it take to undo the
>"damage" of putting crappy gas in your car?
>
>matt


We do have a "knock" sensor that detects detonation, to retard the timing. It's not the greatest sensor though, so it doenst work the best. By using a higher octane fuel, the motor will not detonate as easily, and hence will keep the igntion timing more advanced, and make more power that way. The timing is constantly changing, all the time. It wont stay one certain way regardless of what you do( except for WOT, it stays fairly consistant and steady. The 420A is designed to not get much detonation at all, even using 87 octane fuel.

thanks...so in short, is it worth the power gains on naturally aspirated engines (like mine) to use 93 octane gas?

matt

no, there are no power gains by using higher octane. im not big on the science thing, but from what i understand the octane rating has to do with how the gas combusts, and not wether its "better" or "worse". now once you start modding the engine, the octane rating will need to go up to avoid detonation and knock, but thats once you get into serious mods like tuboing. for the majority of NA applications, even with a few mods, the lowest grade is still fine.

to sum it up, lower octane gas isnt "dirtier" (although were conditioned to think so by the gas companies), its just....different. good ol' 89 for me, thank you.

I'm not sure that I agree. I read here or somewhere else a long time ago that there was not gain with high octane so I stopped buying it. I wen't with low octane for a while and then one day after letting me girlfriend drive my car (and making her fill it up) I noticed a pretty good gain. I asked her what she put in and she said it was high octane and I've used it ever sense.

The gain wasn't huge or anything but it was there.

The octane rating is a rating for resistance to detonation, and how fast the gas burns; higher octane actually burns slower.

The ECU should have a max advance it will use as long as it doesn't detect knock. Now in my opinion this set isn't advanced enough, but then that's what the AFX ECU is for. So if your ECU is pulling timing on lower grade then switching to a higher octane will produce power. When you upgrade to higher compression or Turbo, or Nitrous you do want to use high octane to prevent detonation.

Side Note: some of the Neon guys actually disconnect their knock sensor to prevent this pulling of timing. Now I don't think this is worth the rist. Especially as you add more, and more mods, this could get dangerous. But supposedly the knock sensor picks up a lot of drivetrain/valvetrain noise that it will sometimes pull timing for. Maybe if you had a track car only, and your own knock sensor... but I would not recommend this for a daily driver.



15.9 @ 86.7mph

Injen CAI, 55mm TB, P&P Intake, Crower Cams, Hooker Header, ERT/Catco Cat, GS-T Muffler, AFX UDP, Crane Ign Amp, S-AFC

Octane itself just designates the relationship between Octane (8 carbon chain) and Heptane (6 carbon chain). 93 Octane gas means approximately 93% Octane and 7% Heptane. Heptane is very unstable and combusts prematurely under pressure/heat w/o spark, which is what "knock" is (yeah history channel). Anyways my point is if there is a knock sensor, it'll probably adjust for knock before we'd notice it, and we do have a higher compression engine. I'm not sure if I notice much in the way of gains, but i'm not totally sure (havne't timed it). ANd yes, both fuels are equally clean.

Kinda random quesiont though: Were can I get an AFX ECU? and How much damage will I be doing to my engine by advancing the timing farther if I use the higher octane (i.e. how far is timig advanced)

matt

i used to put 91 in my car, but it was slower and didnt have as much pep in it as it did when i put in 89. i dont have the mods for it to be necessary to put in 91+ so good ol 89 for me too :-)

AFX ECU:
http://www.howellautomotive.com

It will advance timing roughly an addition 6 degrees. Running premium gas = no problem. The ECU still has the ability to pull some timing dependant upon the knock sensor and other fctors. Unless you are running high comression above 10.5:1 I wouldn't even think twice about the amount of advance. Probably won't come into play until over 11.5:1, dpending upon cam grinds, etc.



15.9 @ 86.7mph

Injen CAI, 55mm TB, P&P Intake, Crower Cams, Hooker Header, ERT/Catco Cat, GS-T Muffler, AFX UDP, Crane Ign Amp, S-AFC

so if i'm not running increased compression the ECU isn't a useful mod? SOrry for the confusion, and I really appreciate the time...

thanks again,
matt

No no no. It's a great mod high compression or not. But when you start running high compression or high levels of boost the more advanced timing of the AFX is too much and causes detonation. So when you are high copression you might have to worry about pulling back some of that timing. Through an ignition amp with a timing retard module. It has much better fuel maps and timing curve for stock compression and bolt ons. At higher compression ratio's you can't run tming as advanced without detonation.



15.9 @ 86.7mph

Injen CAI, 55mm TB, P&P Intake, Crower Cams, Hooker Header, ERT/Catco Cat, GS-T Muffler, AFX UDP, Crane Ign Amp, S-AFC

thanks I appreciate it alot...
now i'm just debating whether to get an AFX ecu and eventually turbo my car, or just buy a GST...

thanks again,
matt