IS THIS TRUE OR NOT???
Pro
Joined: Dec 2002
Posts: 601
Likes: 0
Re: IS THIS TRUE OR NOT??? (QuickSilver97)
I remember racetronix chiming in and recommending that all FI cars stay over half tank because it created more reserve? A full tank helps weigh my tail end down so I can get a little traction! :smash:
Thread Starter
Instructor
Joined: Oct 2002
Posts: 163
Likes: 0
From: whittier CA
Re: IS THIS TRUE OR NOT??? (BLOWN IN NC)
very very interesting, some people are laughing about it, while others are not as skeptical about this.
but to clear things up, i did not misunderstand. He specifically told me that adding MORE than 1/2 tank helps.
JBBlownC5: i tried to send you an email
Can anyone elaborate what he said in regards to "adding 5 more gallons"?????? Is this with a 1/2 tank????
but to clear things up, i did not misunderstand. He specifically told me that adding MORE than 1/2 tank helps.
JBBlownC5: i tried to send you an email
Can anyone elaborate what he said in regards to "adding 5 more gallons"?????? Is this with a 1/2 tank????
Le Mans Master
Joined: Apr 2002
Posts: 6,927
Likes: 3
From: Glendale NY
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15-'16-'17-'18- '19
Re: IS THIS TRUE OR NOT??? (A Z06 In CA)
I'll have to agree with Z06 Quinn, and SAXN8R that if the PCM picks up a bad octane reading, it will retard the timing.By adding at least 5 gallons of fuel it will reset the timing table for a more advanced timing :flag :steering: :flag
Instructor
Joined: Jan 2001
Posts: 227
Likes: 0
From: Las Vegas, NV
Re: IS THIS TRUE OR NOT??? (A Z06 In CA)
My old man once told me "chase the money trail and you'll fnd the answer." His wisdom surely applies here... if we want to know if GM DID establish a computer setting that would retime the curves when the tank is less than half full we need to ask why they would do it. What economic advantage is there for GM? Is there money to gain/save? E.g. - would the car get better gas mileage and/or avoid a gas guzzler tax? Would there be lower maintence/warranty repairs due to a leaner running car on bad gas? Where could GM make/save money by adding additional capabiltities to the car?
I am not sure what I believe at this stage... except that it isn't yet clear to me WHY GM would do this. Until this question can be answered I don't believe it. :skep: I could speculate :rolleyes: , but there's a forum already set up for the speculator crowd... the C6 forum. :D
Cheers,
L76
[Modified by L76, 6:21 PM 2/11/2003]
I am not sure what I believe at this stage... except that it isn't yet clear to me WHY GM would do this. Until this question can be answered I don't believe it. :skep: I could speculate :rolleyes: , but there's a forum already set up for the speculator crowd... the C6 forum. :D
Cheers,
L76
[Modified by L76, 6:21 PM 2/11/2003]
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Melting Slicks
Joined: Feb 2001
Posts: 3,360
Likes: 1
From: DFW TX
Senior Member
Cruise-In III Veteran
Cruise-In IV Veteran
Re: IS THIS TRUE OR NOT??? (66ImpalaLT1)
If I get any detonation, I will have to drain my gas and put some new gas in.
As others have said there are (2) Spark Advance tables in the LSx PCM's - High Octane and Low Octane, with about a 4-6 degree difference in timing. After excessice knock retard is detected the PCM switches from the normal High Octane table to the Low Octane table. Once the car is filled up the PCM will assume you have better gas and switch back to High Octane. On the cars I tune I usually leave the Low Octane table untouched and adjust timing in the High Octane table unless otherwise requested by the customer. On a Supercharged car both tables need to be adjusted accordingly, because even the stock Low Octane Spark Advance can be too much for boost.
:chevy
Race Director
Joined: Aug 2000
Posts: 11,188
Likes: 0
From: Scarborough ME
Re: IS THIS TRUE OR NOT??? (Y2Kvert4me)
I find it difficult to believe.
They can't even make a tank sender unit that knows if it's full or empty, how on earth would it know when it's at half? :confused: :D
:cheers:
They can't even make a tank sender unit that knows if it's full or empty, how on earth would it know when it's at half? :confused: :D
:cheers:
Safety Car
Joined: Dec 2000
Posts: 3,888
Likes: 0
From: Humble, Tx
Re: IS THIS TRUE OR NOT??? (Godspeed)
If I get any detonation, I will have to drain my gas and put some new gas in.
Or you could just drive conservatively until all the bad gas is gone.
As others have said there are (2) Spark Advance tables in the LSx PCM's - High Octane and Low Octane, with about a 4-6 degree difference in timing. After excessice knock retard is detected the PCM switches from the normal High Octane table to the Low Octane table. Once the car is filled up the PCM will assume you have better gas and switch back to High Octane. On the cars I tune I usually leave the Low Octane table untouched and adjust timing in the High Octane table unless otherwise requested by the customer. On a Supercharged car both tables need to be adjusted accordingly, because even the stock Low Octane Spark Advance can be too much for boost.
:chevy
Or you could just drive conservatively until all the bad gas is gone.
As others have said there are (2) Spark Advance tables in the LSx PCM's - High Octane and Low Octane, with about a 4-6 degree difference in timing. After excessice knock retard is detected the PCM switches from the normal High Octane table to the Low Octane table. Once the car is filled up the PCM will assume you have better gas and switch back to High Octane. On the cars I tune I usually leave the Low Octane table untouched and adjust timing in the High Octane table unless otherwise requested by the customer. On a Supercharged car both tables need to be adjusted accordingly, because even the stock Low Octane Spark Advance can be too much for boost.
:chevy
Race Director
Joined: Nov 2000
Posts: 11,221
Likes: 899
From: CA
2017 C5 of the Year Finalist
St. Jude Donor '08
Re: IS THIS TRUE OR NOT??? (A Z06 In CA)
I heard from a reliable source that on the Corvettes, (possibly othe made GM cars) that when these cars get BELOW 1/2 a tank of gas that the timing curve is NOT as strong as when the car had over a 1/2 tank of gas.
As far as SCed cars, My experience is that I do hit the knock senser sometimes after gasing up and then getting on it as I get back on the freeway. My car is tuned pretty close to the line and seems to need to find its spot once I gas up. With SCed car that have high flow fuel pumps and boost-a-pumps, like mine, I find it very important to keep it over 1/4 tank of gas. If I don't and get on it, I seem to suck air.