Gas Prices!!
Safety Car
Joined: May 2006
Posts: 4,290
Likes: 140
From: Salem NH
I don't know about TBI vettes.
But I know in the later masks highway mode will run around 15-16:1 AFR, with a lot of advance for increased economy. If 'premium fuel' is not detected (i.e, the flag not set) it will run a little differently.
I think if you can't afford to purchase the gas for the vette, maybe you should sell it and buy an economy car. Or buy an economy car and drive the vette on weekends. Or you you can run low octane fuel, let the ECM retard the crap out of your timing and make the car accelerate like an iron duke.
-- Joe
But I know in the later masks highway mode will run around 15-16:1 AFR, with a lot of advance for increased economy. If 'premium fuel' is not detected (i.e, the flag not set) it will run a little differently.
I think if you can't afford to purchase the gas for the vette, maybe you should sell it and buy an economy car. Or buy an economy car and drive the vette on weekends. Or you you can run low octane fuel, let the ECM retard the crap out of your timing and make the car accelerate like an iron duke.
-- Joe
Last edited by anesthes; Mar 13, 2008 at 02:58 PM.
Melting Slicks
Joined: May 2007
Posts: 2,382
Likes: 2
From: Kathleen FL
That's because you globally retarded the timing 4 degrees (if it was set to 6* btdc originally), not necessarily due to the 87 octane fuel. I could run race fuel in my car, but if I knocked the timing back 4 degrees across the board, I'd get the same results you did. A valid experiment would have been to run the 87 octane fuel, make no other changes, and data log the amount of knock counts / spark retard before and after the octane change.
Le Mans Master
Joined: Apr 2000
Posts: 6,341
Likes: 1
From: Shelton CT
As long as I can afford it, I won't mind buying High octane for my vette.
It's expensive, but I get better TR and Mileage than with 89, wouldn't even try '87.
If I get poor enough not to be able to afford gas, I'll yank the engine and buy, a by then common fuelcell conversion.
It's expensive, but I get better TR and Mileage than with 89, wouldn't even try '87.
If I get poor enough not to be able to afford gas, I'll yank the engine and buy, a by then common fuelcell conversion.
Safety Car
Joined: May 2006
Posts: 4,290
Likes: 140
From: Salem NH
That's because you globally retarded the timing 4 degrees (if it was set to 6* btdc originally), not necessarily due to the 87 octane fuel. I could run race fuel in my car, but if I knocked the timing back 4 degrees across the board, I'd get the same results you did. A valid experiment would have been to run the 87 octane fuel, make no other changes, and data log the amount of knock counts / spark retard before and after the octane change.
I'm glad you brought this up. See how much power he lost by reducing the advance by 4 degrees.
This is why when we built race motors, we keep advancing the timing until it stops making more power on the best octane we can buy locally (93 as of late).
I can't wait for E85 to come out locally. with E85 at 106 or so octane, I should be able to run around 32-34 degrees of advance with 6-8psi of boost.
-- Joe
Safety Car
Joined: May 2006
Posts: 4,290
Likes: 140
From: Salem NH
There was a lot of audible pinging when the timing was up there. After all, the motor is about 11:1 compression static compression. The new 847 cam bleeds off some cylinder pressure, but when timing is up, it can't bleed enough that it will ping horrendously. I don't think it would be possible to datalog since I'm running carbed. But hey, its cool to know that you can run 87 octane on a high compression motor as long as your timing is down. It just won't run as well, but it runs good enough for the average Joe who knows a mild 350's powerband enough not to complain.
-- Joe
Melting Slicks
Joined: May 2007
Posts: 2,382
Likes: 2
From: Kathleen FL
I have it currently at 36. That is the sweet spot for the motor. Anymore, it will ping. And any less, it will feel laggy. I've verified this with many hours of testing and tuning. Well, as long as I drive with finesse, the car can get as high as 14 in the city and 24 on the highway. Once the foot is on it, the fuel economy will drop like a rock.
Burning Brakes
Joined: Mar 2008
Posts: 881
Likes: 24
From: Coquitlam BC
Other than the fact that octane reduces knock (and doesn't add power) I just don't understand the gist of this whole thread. In the first place, why buy a Vette if you're worried about gas prices? If you're looking for economy you need to drive it less and keep your foot out of it. But where's the fun in that? Suck it up and enjoy it. Economy cars are just transportation; Corvettes are a driving experience!
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From: PA
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by anesthes
I don't know about TBI vettes.
Originally Posted by anesthes
I think if you can't afford to purchase the gas for the vette, maybe you should sell it and buy an economy car. Or buy an economy car and drive the vette on weekends. Or you you can run low octane fuel, let the ECM retard the crap out of your timing and make the car accelerate like an iron duke.
-- Joe
-- Joe
I am a little surprised that you, as my fan club, my groupie, who likes to follow and study my lifestyle, my every move, doesn't already know more about my ignition timing, and my ECM retardation of my timing. You are slipping. At least you didn't miss an opportunity to take a pot shot, regardless of how lame.
RACE ON!!!
Instructor
Joined: Feb 2008
Posts: 158
Likes: 0
From: Houston TX
IMO, the knock sensors will take care of you. Depending on where/how you drive, lower octane fuel won't hurt your mileage.
You can make up your own mind by doing your own tests. Buy a half tank of regular unleaded and listen for pinging. If you ping, let off the gas a bit. Log your mileage.
Here's anecdotal evidence based on my LS2 Trailblazer SS:
I normally run premium unleaded in it because I like to romp hard and often. HOWEVER, I've run the following experiment multiple times (to make sure it wasn't a fluke): On a long trip, say 500 miles round trip, I've run regular unleaded to my destination, and premium back home (or vice versa). There is a noticeable increase in mileage using regular unleaded (typical driving will be hours on end at 70-ish mph with the cruise on). I'll typically get 16-18 mpg pure hwy on premium, and 17-19 mpg pure highway on regular.
Melting Slicks
Joined: Jan 2008
Posts: 2,514
Likes: 30
From: Friendswood TX
Just run 93.
When you look at the big picture... at .10 cents more a gallon, even with 18 gallons of gas, it only $1.80 more for the whole tank. Will that $1.80 really make a difference to your wallet? Not mine... Ill stick with 93...
When you look at the big picture... at .10 cents more a gallon, even with 18 gallons of gas, it only $1.80 more for the whole tank. Will that $1.80 really make a difference to your wallet? Not mine... Ill stick with 93...
Safety Car
Joined: May 2006
Posts: 4,290
Likes: 140
From: Salem NH
And a lot of other things.
I am the only TBI owner that has posted up to the point of your post. As usual, your comments are misdirected and off subject. I made no comment about being able to afford gasoline for a Corvette. I merely advised the OP, saber7469, who DID comment on gasoline prices and informed him of the effects of octane. I vehemently oppose any form of waste and will advise where appropriate to help stem it.
I am a little surprised that you, as my fan club, my groupie, who likes to follow and study my lifestyle, my every move, doesn't already know more about my ignition timing, and my ECM retardation of my timing. You are slipping. At least you didn't miss an opportunity to take a pot shot, regardless of how lame.
RACE ON!!!
I am the only TBI owner that has posted up to the point of your post. As usual, your comments are misdirected and off subject. I made no comment about being able to afford gasoline for a Corvette. I merely advised the OP, saber7469, who DID comment on gasoline prices and informed him of the effects of octane. I vehemently oppose any form of waste and will advise where appropriate to help stem it.
I am a little surprised that you, as my fan club, my groupie, who likes to follow and study my lifestyle, my every move, doesn't already know more about my ignition timing, and my ECM retardation of my timing. You are slipping. At least you didn't miss an opportunity to take a pot shot, regardless of how lame.
RACE ON!!!
I just re-read my post. What I was saying was, "I don't have experience with the TBI computers, I dont know how they are coded". I then
explained highway mode on the later bins. I also didn't take an opinion either way as to the OP's question.
I'm glad you decided to take this as me talking directly to you, then turn it around into an insult at me. Good work, once again.
The rest of the post it was a generalization, geared more towards the OP.
And I don't "follow your lifestyle". I posed a question on the forum "who do you think you are!?" on a thread, and I got numerous PM's, some from people who actually KNOW you. I almost feel bad for you now.
-- Joe
Last edited by anesthes; Mar 14, 2008 at 11:32 AM.
Instructor
Joined: Feb 2008
Posts: 158
Likes: 0
From: Houston TX
500 mile trip:
Regular @ 19 mpg @$3.00/gal = $78.94
Premium @ 18 mpg @$3.30/gal = $91.67
Difference = $12.73. Not a fortune, but it is free money, assuming I'm driving in a mellow manner for the road trip.
Team Owner
Joined: Oct 2004
Posts: 81,241
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From: altered state
St. Jude Donor '05
Race Director
Joined: May 2005
Posts: 11,992
Likes: 1,331
From: Middletown, DE
NO! Octane is nothing more than a measure of a gasoline's anti-knock properties. If it doesn't knock on low octane, the only thing you get with higher octane is the ability to tell your neighbor that your Corvette is such an animal that you HAVE to use the expensive stuff. Except for rare isolated cases, super premium is for the oil companies to make excess profits from the "nothing but the best for my baby" crowd.
RACE ON!!!
RACE ON!!!
You are a very knowledgeable guy, but you are dead wrong on this one. Read the D$#ned owner's manual for the LT1: "Use premium unleaded gasoline rated at 91 octane or higher. You may use middle grade or regular unleaded gasolines, but your vehicle may not accelerate as well." You can certainly run 87 in an LT1, and you will not hurt the car. BUT, the LT1 is DESIGNED for optimal performance using 91 octane. Compression, timing, etc. The lower octane stuff does not run as briskly, and will get worse fuel economy. Lots of us LT1 owners have tried the low grade stuff and we've seen the results. The thing just feels more sluggish, and we wind up filling up a bit more quickly. BTW, if you are running a PCMforless chip as many of us do, I believe you are better off running 93 because it's tuned just a bit more aggressively to use that stuff.
Safety Car
Joined: May 2006
Posts: 4,290
Likes: 140
From: Salem NH
-- Joe
Melting Slicks
Joined: May 2007
Posts: 2,382
Likes: 2
From: Kathleen FL
Why do you say that? I like the idea of mostly ethanol, its much higher octane . It burns about 30% than straight gasoline, so you would need to size the injectors a hair larger, but for right around the same price (and in some situations cheaper) you can build an e85 car with more ignition advance, or more boost.
-- Joe
-- Joe