Regular gas Corvette conversion
Team Owner
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From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
I probably wouldn't say the ECM 'compensates' for different grades of fuel because that may be a slightly inaccurate way to describe the function of the knock control portion of the ECM.
I would say it 'tries' to protect the engine from the ill effects of lower than reccomended fuel octane.
I would say it 'tries' to protect the engine from the ill effects of lower than reccomended fuel octane.
I say TOMATO.
My point is that some owners feel its necessary to run Premium fuel all the time. The recommended minimum octane for the L98 is 87. Anything less can cause excess knock counts, maybe engine damage.
What component of the engine control system adjusts timing vs knock counts? Maybe its the ECM!
So to assist 89er consideration of changing the compression ratio to use lower octane fuel, I'm suggesting that he merely pump from the "other" nozzle.
It's so easy, even a caveman can do it!
Racer
Joined: May 2006
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Originally Posted by JrRifleCoach
Like I said, the ECM will compensate.
Originally Posted by JrRifleCoach
If your so sure, why don't you post this as a separate thread. I'll bet you'll find your mostly alone in this belief.
Advanced
Joined: Oct 2006
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From: Huron OH
OK, so if i don't have knock at wot with say 87 octane then i don't need to buy the better stuff for performance? If that is so then why do they sell 110 at the strip and they do seperate dyno runs with different octane getting different hp #'s?
Team Owner
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From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
Actually, what you said was, "The ECM will compensate for the different grades of fuel..." See post #6 where you said it or post #7, where I quoted your having said it. Reread post #7 to learn that the ECM can never know the octane rating of the gasoline. If it can't detect "different grades of fuel", how could it possibly "compensate for them???
Why should I post a separate thread on this? I am simply following up on the subject at hand. That is a statement and an example of how the system works. You might be right about me being in the minority, but I hope I'm not, because that would speak poorly about the number of forum members that understand how the ESC system works.
Why should I post a separate thread on this? I am simply following up on the subject at hand. That is a statement and an example of how the system works. You might be right about me being in the minority, but I hope I'm not, because that would speak poorly about the number of forum members that understand how the ESC system works.
Last edited by JrRifleCoach; Mar 18, 2007 at 08:14 PM.
Le Mans Master
Joined: Jun 2006
Posts: 5,642
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From: One day you're a Comet...the next day you're dust... Arkansas
High octane is like extra large pants. Any one can wear em, but it's really only necessary for fat people.
The skinny people can save money and buy small pants (low octane) that suit them better.
A fat person can fit into skinny pants, but might blow a hole in the inseam if any detonation occurs.
Then of course you still have all the skinny kids buying fat pants because they think they're better.
The skinny people can save money and buy small pants (low octane) that suit them better.
A fat person can fit into skinny pants, but might blow a hole in the inseam if any detonation occurs.
Then of course you still have all the skinny kids buying fat pants because they think they're better.
Team Owner
Joined: May 2002
Posts: 24,337
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
110 octane is sold at the strip because idiots that don't need it buy it, and many that do need it that are running lots of boost or very high CRs.
Whose dyno runs are you referring to?
A car with zero knocks on 87 octane should make about the same power with 91 octane or 110 octane.
JR, the subject has been debated numerous times on here, but some people just refuse to believe the facts. I guess if they've been wasting extra $$ for years on high octane, it's a little hard to accept. Of course, if you're testing for knock counts, you should do it on the hottest day with the car as hot as it'll ever get on the street or track.
As far as the ECM, I'm not sure what years have learning ability, if any, but I think it simply retards timing when knock occurs, and then slowly advances it back, you'll feel it when you're accelerating like someone pulled the parachute. The key is knock will occur. It does nothing to prevent knock based on the octane level as your post implies.
Last edited by CentralCoaster; Mar 18, 2007 at 08:14 PM.
Team Owner
Joined: Sep 2003
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From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
JR, the subject has been debated numerous times on here, but some people just refuse to believe the facts. I guess if they've been wasting extra $$ for years on high octane, it's a little hard to accept. Of course, if you're testing for knock counts, you should do it on the hottest day with the car as hot as it'll ever get on the street or track.
As far as the ECM, I'm not sure what years have learning ability, if any, but I think it simply retards timing when knock occurs, and then slowly advances it back, you'll feel it when you're accelerating like someone pulled the parachute. The key is knock will occur. It does nothing to prevent knock based on the octane level as your post implies.
As far as the ECM, I'm not sure what years have learning ability, if any, but I think it simply retards timing when knock occurs, and then slowly advances it back, you'll feel it when you're accelerating like someone pulled the parachute. The key is knock will occur. It does nothing to prevent knock based on the octane level as your post implies.
So, the ECM will compensate for different octanes by adjusting timing based on knock counts.
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Team Owner
Joined: May 2002
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
It's like having an electric shock collar on your dog that zaps him everytime he leaves the property, only in this case your dog will never learn, he'll keep running into the street.
As opposed to using the right octane level, the car will hardly ever knock.
Last edited by CentralCoaster; Mar 18, 2007 at 08:39 PM.
Thread Starter
Racer
Joined: Dec 2006
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EXACTLY! If the knock counts rise, the ECM backs down the timing to compensate. Change fuel grades and the ECM will maintain the highest timing value until knocking appears.
So, the ECM will compensate for different octanes by adjusting timing based on knock counts.
So, the ECM will compensate for different octanes by adjusting timing based on knock counts.
And lowering the compression will keep it from pre-igniting without spark. Thanks for the feedback that says if I lower the compression I can leave the timing as it is.
Team Owner
Joined: May 2002
Posts: 24,337
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
It'd be easier to buy an ECM emulator from Craig Moates.
You could then have an 87 octane program with reduced timing advance tables, and simply switch between that and your stock program on the fly.
You could then have an 87 octane program with reduced timing advance tables, and simply switch between that and your stock program on the fly.
Racer
Joined: May 2006
Posts: 293
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Originally Posted by JrRifleCoach
EXACTLY! If the knock counts rise, the ECM backs down the timing to compensate. Change fuel grades and the ECM will maintain the highest timing value until knocking appears.
So, the ECM will compensate for different octanes by adjusting timing based on knock counts.
So, the ECM will compensate for different octanes by adjusting timing based on knock counts.
Le Mans Master
Joined: Dec 2002
Posts: 5,270
Likes: 3
From: Seattle Area WA
High octane is like extra large pants. Any one can wear em, but it's really only necessary for fat people.
The skinny people can save money and buy small pants (low octane) that suit them better.
A fat person can fit into skinny pants, but might blow a hole in the inseam if any detonation occurs.
Then of course you still have all the skinny kids buying fat pants because they think they're better.
The skinny people can save money and buy small pants (low octane) that suit them better.
A fat person can fit into skinny pants, but might blow a hole in the inseam if any detonation occurs.
Then of course you still have all the skinny kids buying fat pants because they think they're better.
Racer
Joined: Jun 2000
Posts: 292
Likes: 3
From: Chico CA
Interesting thread. I recommend contacting Alvin at pcmForLess.com, and have him make a custom chip for your ECM.
Tell him that you need a specific chip programmed for Mexican gas. Tell him the octane available, the particulars about your car, and he'll do the rest. Like spark advance curve, fan temps... all kinds of stuff.
Then when you get back from Mexico, yank that chip and get back to higher octane gas like was intended for your car.
Alvin made a custom chip for my 1990. Part of the question and answer was: "I promise to use 92+ octane gas at all times." That enabled him to program other parameters for the ECM to get the best overall performance from my otherwise stock 1990.
He can do the same for a particular (and short-term) Mexico trip.
Realize that... at some point with low-octane gas (like 84 or less) - no amount of programming is going to help. The simple physics of the compression ratio will mean that the engine will knock - like tap-shoes on a steel staircase. As mentioned earlier, you can get away with 87 octane. But that's just it: you're getting away with it, to the detriment of performance.
That's my opinion, and I'm sticking to it!
Tell him that you need a specific chip programmed for Mexican gas. Tell him the octane available, the particulars about your car, and he'll do the rest. Like spark advance curve, fan temps... all kinds of stuff.
Then when you get back from Mexico, yank that chip and get back to higher octane gas like was intended for your car.
Alvin made a custom chip for my 1990. Part of the question and answer was: "I promise to use 92+ octane gas at all times." That enabled him to program other parameters for the ECM to get the best overall performance from my otherwise stock 1990.
He can do the same for a particular (and short-term) Mexico trip.
Realize that... at some point with low-octane gas (like 84 or less) - no amount of programming is going to help. The simple physics of the compression ratio will mean that the engine will knock - like tap-shoes on a steel staircase. As mentioned earlier, you can get away with 87 octane. But that's just it: you're getting away with it, to the detriment of performance.
That's my opinion, and I'm sticking to it!
Last edited by BadjerJim; Mar 18, 2007 at 10:02 PM.
Thread Starter
Racer
Joined: Dec 2006
Posts: 292
Likes: 0
Interesting thread. I recommend contacting Alvin at pcmForLess.com, and have him make a custom chip for your ECM.
Tell him that you need a specific chip programmed for Mexican gas. Tell him the octane available, the particulars about your car, and he'll do the rest. Like spark advance curve, fan temps... all kinds of stuff.
Then when you get back from Mexico, yank that chip and get back to higher octane gas like was intended for your car.
Alvin made a custom chip for my 1990. Part of the question and answer was: "I promise to use 92+ octane gas at all times." That enabled him to program other parameters for the ECM to get the best overall performance from my otherwise stock 1990.
He can do the same for a particular (and short-term) Mexico trip.
That's my opinion, and I'm sticking to it!
Tell him that you need a specific chip programmed for Mexican gas. Tell him the octane available, the particulars about your car, and he'll do the rest. Like spark advance curve, fan temps... all kinds of stuff.
Then when you get back from Mexico, yank that chip and get back to higher octane gas like was intended for your car.
Alvin made a custom chip for my 1990. Part of the question and answer was: "I promise to use 92+ octane gas at all times." That enabled him to program other parameters for the ECM to get the best overall performance from my otherwise stock 1990.
He can do the same for a particular (and short-term) Mexico trip.
That's my opinion, and I'm sticking to it!
Thread Starter
Racer
Joined: Dec 2006
Posts: 292
Likes: 0
Thread Starter
Racer
Joined: Dec 2006
Posts: 292
Likes: 0