while talking trash at a local cruise in the subject of octane requirements came up. i've got a 69 chevelle and the octane needs are pretty much set by compression and timing. are the new style computer controled engines (knock sensors) able to use different octane levels by controlling ignition advance? in other words will they run on regular and really come to life with premium?
more mental masturbation than anything, thanks for the input

The way I understand it, they are optimized for the "designated" grade of fuel. If you add "more" the computer doesn't care and nothing changes. Put a lower grade of fuel in though and it will crank back the tuneup to allow for the change in fuel. Like my daily driver is optimized for 95 Octane. Well, nice 'cause I can't get it here in the states so the U.S. versions are cranked back to use 92 Octane in its 11:1 motor. If I use 87 I probably wouldn't even notice unless I jump on it and notice the loss in power. If I did put more than 92 in, I wouldn't realize any gains. The whole thing is drive by wire anyway, no distributor, no throttle cable, nothing but wires. Computer is God. At least that's what my owner's manual says.

The last post was correct however there is alot to be said about relationships between a computer controlled car's tune vs. octane. You can tune the computer to be optimal for the higher octane which yields noticable power gains. I'm involved alot with LS1 motors and everything is just VERY different. For example, an optimal timing table will take out not more than 22 degrees total timing on a mildly modded LS1. You try running a N/A Small Block on 22 tot. and tell me how that works for you!!! New cars run off a OBDII computer that is more hackable than any system prior to it so changing timing tables and fuel delivery curves for octane, elevation and temperature can generally increase power on an LS1 by as much as 20RWHP...STOCK!! Add cold intake and a free-flowing exhaust and you're in business. By the way, in regards to your knock sensor question. Generally it is not affected by higher octane but your O2 sensors should be the ones you're looking after. :cool:

I would love for someone to "find" 20 or more RWHP in my Jag. MORE is better :D So, I've seen articles on hacking the LS1 but does anyone know if "all" of the ODBII computers are 'hackable' if that's a word? I have a test mule if anyone cares to tinker...... Let's see, Flowmasters / K&N air box / computer curve = tire smoke!

Believe it or not your Jag most likely uses a Ford CPU. Give this site a quick read on tunes..
http://www.cmotorsports.com Then call Dave over there at 702-798-8504. He's a pretty good friend of mine. They have always done GM programming and now are doing Ford as well. Tell Dave Keith from lvfbody referred you. They happen to also be the only authorized BMR dealer in my area which is where I got all the suspension for my Chevelle :cool: Good luck!!

Yep, there is some Ford content. It does use a Jag motor (4 cam V8) and ZF 6spd auto (same as BMW 7 series and Bentley) Some of the chassis parts are the same as Lincoln LS. Who knows, maybe the computer is Lincoln also. I'll give them a shout. Thanks for the info.
graemlins/thumbsup.gif

No prob! He'll you're not that far away. Come get your car tuned and have a few graemlins/beers.gif on me while you wait. The shop is right next to LVMS. Some strategic planning on your part could get you some good entertainment while you're out here. :cool:

Remember, your motor can knock or ping if either there is too much timing, or the compression is too high.

If the compression is too high, it will knock no matter what the computer does to the timing. The only cure would be higher octane fuel. Obviously, if you have spark knock, the computer will record a "hit" (knock), and retard it a specified amount until the sensor records no more hits.