Grand prix GTP 1999 S/Ced running off 87 octane mods - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 11-14-2006, 02:35 PM   #11
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Default Re: Grand prix GTP 1999 */Ced running off 87 octane mods

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Originally Posted by 19bonnie95
My friend has been running his 99 gtp off 87 octane to save money. He always ran 93 octane but he says its safe to run 87 octane if he babys it. He has custom donpipe u bend delete 3.4 inch pully intense pcm drilled 180 t-stat K+N cold air intake. Is he right is it safe to drive on 87 octane if he babys it he says max 2 lines of boost on his gauge when getting onto the freeway......
FWIW, if he TRULY doesn't ever go into boost more than like 1 or 2 bars on the stock boost "gauge" then he should probably be fine. (2 bars on that thing is only a little over 1psi) Not sure why he would do that with mods, but if thats what he is honestly doing, I don't think he would see KR with that little amount of throttle. I've never looked at an Intense PCM timing table that closely so I'm not sure what it does for part throttle timing, but that would be the main factor really.

However, even with 93 octane that car would probably get KR. Its barely modded enough for the 3.4 pulley as it is. If I were him, I would definately be running 93 octane. If he really adds it up, and actually figures his gas mileage, he probably isn't saving that much money if any. You typically will get worse mileage with lower octane fuel so it doesn't really save you any money to run it.
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Old 11-14-2006, 03:34 PM   #12
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Default Re: Grand prix GTP 1999 */Ced running off 87 octane mods

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Originally Posted by dbtk2
If he really adds it up, and actually figures his gas mileage, he probably isn't saving that much money if any. You typically will get worse mileage with lower octane fuel so it doesn't really save you any money to run it.
Right on the money. I get better mileage by far the higher my octane goes.
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Old 11-14-2006, 03:49 PM   #13
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This can be done, I know someone personaly with a 99 GTP that he runs on 87 octane. He has tons of mods including a cam and headers which suggests a performance orientation but his current focus is gas mileage.

He runs a 3.4" pulley with 21* at WOT and up to 44* timing at cruise with no signs of KR.

Still, I think it'* a rather pointless excersise but it can be done.

Cheers,
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Old 11-14-2006, 06:18 PM   #14
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Quote:
Originally Posted by Foghorn
This can be done, I know someone personaly with a 99 GTP that he runs on 87 octane. He has tons of mods including a cam and headers which suggests a performance orientation but his current focus is gas mileage.

He runs a 3.4" pulley with 21* at WOT and up to 44* timing at cruise with no signs of KR.

Still, I think it'* a rather pointless excersise but it can be done.

Cheers,
Let'* not encourage people to try something when the car you're talking about is probably a very unique setup.
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Old 11-14-2006, 06:18 PM   #15
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im the guy with the 99 GTP.. I am at school right now (Auto Tech) and I just scanned with a GM Tech II Scanner. I am safe.. the way I drive it i am gettin no knock.. and even when its to the floor i only get 4*... it was only 3 but once it got hot it went to 4..



my instructor says that if I have a knock (ping?) sensor that it retards timing when it hears knock to make it safe.. retarding timing only makes me lose horsepower. the sensor is there to keep me safe and knock is bad, but not going to hurt me other than in HP.. this is a 50year old dude who was the manager of a ford dealearhsip for 15 years, and has been doing this stuff all his life.
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Old 11-14-2006, 06:19 PM   #16
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he also said that 87 octaine burs hotter (more btu?) and you will get better gas milage with 87..
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Old 11-14-2006, 06:23 PM   #17
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Your shop instructor obviously has no experience with supercharged high-effective-compression ratio engines.

If you have KR, the knock ALREADY HAPPENED. And no, you will get WORSE gas mileage with 87 octane. There'* about 1000 L67 engine owners here that will tell you that. I think we know a bit more about it than the guy you're listening to.

I have two L67'*. One bone-stock, the other not. BOTH get better mileage with the proper octane. If you're getting 4° of KR this time of year, you're in SERIOUS trouble when spring rolls around.

Sell the car if you can't afford the gas. Or go back to a stock pulley ASAP and run MID-grade.
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Old 11-14-2006, 06:26 PM   #18
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thanks for the advise.. but I will be running 93 when spring rools arround.. and yes I am going to sell the car.
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Old 11-14-2006, 06:28 PM   #19
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also.. its not a DHP PCM.. its a custom tune by a powertuner..
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Old 11-14-2006, 06:28 PM   #20
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Then why are we having this conversation?
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