With the GXP using the LD8 Northstar... - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


Bonneville GXP/ Northstar Powered Cars Discuss your Bonneville GXP and/or any other Northstar powered Olds or Cadillac... Including the 3.5L Twin Cam V6 (Short Star ) 4.0L and 4.6L Northstar V8's. Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 06-16-2006, 07:45 PM   #1
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Default With the GXP using the LD8 Northstar...

Does running only 93+ octane bump horsepower up from the stated 275 HP rating? I ask this because as we know the LD8 N* is designed to be capable of surviving on regular 87 octane gasoline. Hopefully though, not too many folks will force it to do so. I will always be using an octane rating of 93 or more however. With the advanced electoronic controls of the N* being capable of learning from its various input sources - it would seem reasonable that it would be able to learn to push the timing up further, etc. allowing for a small, but definite, increase in power. I am thinking along the lines of maybe 5 horsepower - but still a nice little increase.

I think this would definitely be the case, as you can be assured that the stated rating of 275HP was obtained with standard grade 87 octane gasoline as it meets the minimum requirements for this engine. Just as you can be assured that the stated 300HP rating (I know, depends on what year) for the L37 N* rating was obtained using premium grade fuel of at least 92 octane which meets the minimum requirements for that engine.

I think that should definitely be the case. Let me know what you guys think...
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Old 06-16-2006, 09:25 PM   #2
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Default Re: With the GXP using the LD8 Northstar...

Quote:
Originally Posted by 1999Daytona500PaceCar
Does running only 93+ octane bump horsepower up from the stated 275 HP rating? I ask this because as we know the LD8 N* is designed to be capable of surviving on regular 87 octane gasoline. Hopefully though, not too many folks will force it to do so. I will always be using an octane rating of 93 or more however. With the advanced electoronic controls of the N* being capable of learning from its various input sources - it would seem reasonable that it would be able to learn to push the timing up further, etc. allowing for a small, but definite, increase in power. I am thinking along the lines of maybe 5 horsepower - but still a nice little increase.

I think this would definitely be the case, as you can be assured that the stated rating of 275HP was obtained with standard grade 87 octane gasoline as it meets the minimum requirements for this engine. Just as you can be assured that the stated 300HP rating (I know, depends on what year) for the L37 N* rating was obtained using premium grade fuel of at least 92 octane which meets the minimum requirements for that engine.





I think that should definitely be the case. Let me know what you guys think...



I think that 275 number was with premium fuel. I sure can tell a difference in high speed performance with premium compared to regular. The owners manual states our car can run on 87 due to knock sensors but for max perforomance use 93. The older Northstars required 93 or high but since ours is the newer design with knock sensors we can get away with regular and no problems. 275 hp with premium cause if the engine could make more power you could have been sure pontac/cadillac would have promoted that fact.
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Old 06-16-2006, 09:28 PM   #3
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I want to stress again....you dont want to have too much power going to the front wheels of these cars. Drive a SS impala or any car with the supercharged 3800 as well as the 3.5 maximas. Lots of tire melting low end but its just not a smooth application of power. Anything over 300 hp and I want rear wheel drive like your trans am.
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Old 06-16-2006, 10:49 PM   #4
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There is no 'power' to be had in premium fuel unless you have timing retarded for knock.

Premium fuel (higher octane) is harder to ignite than 87. If your car doesn't need it, running it won't do you any good.

In addition, the additives and detergents in premium fuel are identiacal to low and mid-grade.
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Old 06-17-2006, 02:27 AM   #5
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I have said this several times here, ... the LD8 was designed for premium. It is stated as such in the Owners Manual. Knock sensors or not it is a 10-1 compression engine and no where will you find stated it is ok to run on regular fuel. I have heard from others that their dealer says it'* ok and that is BS. The dime - 20 cents a gallon you save a gallon is not worth it. Knock sensors retard timing and gives you worse gas mileage and less acceleration.
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Old 06-17-2006, 03:09 AM   #6
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my owners manual states that premium fuel is recommended, but regular can be run at a lower performance level. I'd say just run premium and be done with it.. I see quite a difference in fuel economy anyways by running premium as well.
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Old 06-17-2006, 11:18 AM   #7
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Quote:
Originally Posted by Custom88
my owners manual states that premium fuel is recommended, but regular can be run at a lower performance level. I'd say just run premium and be done with it.. I see quite a difference in fuel economy anyways by running premium as well.
in my 4.0 Aurora, its supposed to be run on 91+ ONLY, however, i never cared enough to actually use it until recently.. With the Premium in the tank the car runs about 5* cooler, and i get 10% better fuel mileage (20mpg on 87 octane / 22mpg on 93 octane)... since 93 is only about 10% more expensive than 87, im not really spending any more on gas because of increased economy, and i definately get a bit more zip out of the car with teh high-test fuel
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Old 06-17-2006, 01:36 PM   #8
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I just wanted to get your thoughts... Thanks! I always run 93+ in all our vehicles and all my prior vehicles as well. To clarify one thing though, the L37 version of the N* came out in 1993 as the original N* and required Premium fuel - but the LD8 version of the N* came out in 1994 and only required 87 octane fuel. This is when the difference in HP levels came about to make a real difference in the various upper level models (SLS vs STS).

I will see if I can find anything about the details of the testing done to rate the HP of manufacturer'* engines so I can post it here. But I as I understand it, an engine was required to be tested with the fuel which met its minimum requirements. Since that is the way most vehicles will be driven - and thus people are not complaining that they bought a vehicle with an advertised HP level of XXX that is stated to be fully capable of running on 87 octane fuel - yet, when run on the 87 octane fuel the vehilcle will never produce the advertised HP. That is why we have the government regulations to protect the consumer. (Yes, they don't always protect - sometimes they hurt!) So that is why I believe there is a slight bump in HP from the continuous use of 93+ octane as the engine management system adjusts. I know that much of this has recently changed with the updated SAE methods to certify horsepower - which I truly believe is for the better- but I will see what I can find.
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