Fuel Additive / Higher Octane Fuel & Knock Retard...?
01-25-2004, 12:04 PM
#1
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Fuel Additive / Higher Octane Fuel & Knock Retard...? Just wondering what you guys use, and what is safe/ best to use.
I keep reading posts about people mixing 50/50 with normal & high octane. Where do you guys get this? The only thing I have found around me are octane boosters (STP, Outlaw....) and leaded gas that is high octane.
I only use Amoco 93 octane in my car, but even with that gas my car still gets "slight" knock from time to time around 3900 RPMs (ATAP data logs). Going to dyno for a baseline in a couple of weeks and would like to find some good fuel to make sure I dont have any KR.
TIA,
-Nick
I keep reading posts about people mixing 50/50 with normal & high octane. Where do you guys get this? The only thing I have found around me are octane boosters (STP, Outlaw....) and leaded gas that is high octane.
I only use Amoco 93 octane in my car, but even with that gas my car still gets "slight" knock from time to time around 3900 RPMs (ATAP data logs). Going to dyno for a baseline in a couple of weeks and would like to find some good fuel to make sure I dont have any KR.
TIA,
-Nick
01-25-2004, 03:17 PM
#2
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"slight knock" is NORMAL!!! You can't possibly build an engine and expect the design to cover ALL operating environments and variables - that is what that sophisticaed knock detection in the LS1/LS6 is good at. Adding octane to an engine that is not optimised for that specific rating is a waste of money. Unless you have recalibrated teh advance curves, milled the heads or changed valvetrain/cam and or pistons, anything more than R+M 91 is just $ out the tailpipe.
Beyond that any of those "octane boost" chemicals are not only marginally effective in eliminating preignition, but can and do cause contamination to the crankcase (oil) and leave unwanted deposits on the internals. Don't look for correcting a possible problem with a "band aid".
I have reason to suspect that even 100LL Avgas would show a few percent of indicated KR under some regimes, and any small amount of KR is transient anyway - a basic non issue for performance.
As long as your adaptave spark table is at 100% and your car is in optimum tune, go ahead put in "Ultra 94" for comfort - but anything beyond that is detrimental IMHO.
Beyond that any of those "octane boost" chemicals are not only marginally effective in eliminating preignition, but can and do cause contamination to the crankcase (oil) and leave unwanted deposits on the internals. Don't look for correcting a possible problem with a "band aid".
I have reason to suspect that even 100LL Avgas would show a few percent of indicated KR under some regimes, and any small amount of KR is transient anyway - a basic non issue for performance.
As long as your adaptave spark table is at 100% and your car is in optimum tune, go ahead put in "Ultra 94" for comfort - but anything beyond that is detrimental IMHO.
01-25-2004, 04:47 PM
#3
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Originally Posted by emarkay
"slight knock" is NORMAL!!! You can't possibly build an engine and expect the design to cover ALL operating environments and variables - that is what that sophisticaed knock detection in the LS1/LS6 is good at. Adding octane to an engine that is not optimised for that specific rating is a waste of money. Unless you have recalibrated teh advance curves, milled the heads or changed valvetrain/cam and or pistons, anything more than R+M 91 is just $ out the tailpipe.
Beyond that any of those "octane boost" chemicals are not only marginally effective in eliminating preignition, but can and do cause contamination to the crankcase (oil) and leave unwanted deposits on the internals. Don't look for correcting a possible problem with a "band aid".
I have reason to suspect that even 100LL Avgas would show a few percent of indicated KR under some regimes, and any small amount of KR is transient anyway - a basic non issue for performance.
As long as your adaptave spark table is at 100% and your car is in optimum tune, go ahead put in "Ultra 94" for comfort - but anything beyond that is detrimental IMHO.
Beyond that any of those "octane boost" chemicals are not only marginally effective in eliminating preignition, but can and do cause contamination to the crankcase (oil) and leave unwanted deposits on the internals. Don't look for correcting a possible problem with a "band aid".
I have reason to suspect that even 100LL Avgas would show a few percent of indicated KR under some regimes, and any small amount of KR is transient anyway - a basic non issue for performance.
As long as your adaptave spark table is at 100% and your car is in optimum tune, go ahead put in "Ultra 94" for comfort - but anything beyond that is detrimental IMHO.
I know that a little knock is normal, and the timing curves look completely normal on my car even when I do see Knock (<2deg) so I was not all that concerned. Just wondering what was out there and what you guys thik about it.
Last edited by niphilli; 01-25-2004 at 07:55 PM.
01-25-2004, 06:07 PM
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The real answer is octane boosters use trick wording in their labeling.
When they say lets say 7 points gain, the end user thinks then its boosting 7 octane higher when it really is POINT 7 which is 0.7 which is no real gain.
They also will effect the O2s and over time using booster will reduce the life of them.
As to mixing pump gas with racing gas, some makers like Union76 do make an unleaded 100 octane but the issue is this type of gas burns at a slower rate which is not great for fast burning heads so if wanting to use it do not go overboard use no more then like a 25/75 race/street gas ratio.
With proper tuning and AFR you do not need either, have no knock and have good WOT timing.
I suggest you reconsider using that mucked up MAF as a cause.
When they say lets say 7 points gain, the end user thinks then its boosting 7 octane higher when it really is POINT 7 which is 0.7 which is no real gain.
They also will effect the O2s and over time using booster will reduce the life of them.
As to mixing pump gas with racing gas, some makers like Union76 do make an unleaded 100 octane but the issue is this type of gas burns at a slower rate which is not great for fast burning heads so if wanting to use it do not go overboard use no more then like a 25/75 race/street gas ratio.
With proper tuning and AFR you do not need either, have no knock and have good WOT timing.
I suggest you reconsider using that mucked up MAF as a cause.
01-25-2004, 06:49 PM
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Your car should run great on 93 octane. Every 5,000miles, I run fuel injector cleaner thru the engine. Another point: You have an SLP 85mm MAF, In order to use this MAF correctly with the PCM, the MAF table needs to be re-calibrating for the after-market MAF. Have you done any PCM tuning?
EDIT: You should never have to rely on octane boosters. Tune the PCM for whatever fuel you have.
EDIT: You should never have to rely on octane boosters. Tune the PCM for whatever fuel you have.
01-25-2004, 07:55 PM
#6
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Originally Posted by Team ZR-1
The real answer is octane boosters use trick wording in their labeling.
When they say lets say 7 points gain, the end user thinks then its boosting 7 octane higher when it really is POINT 7 which is 0.7 which is no real gain.
They also will effect the O2s and over time using booster will reduce the life of them.
As to mixing pump gas with racing gas, some makers like Union76 do make an unleaded 100 octane but the issue is this type of gas burns at a slower rate which is not great for fast burning heads so if wanting to use it do not go overboard use no more then like a 25/75 race/street gas ratio.
With proper tuning and AFR you do not need either, have no knock and have good WOT timing.
I suggest you reconsider using that mucked up MAF as a cause.
When they say lets say 7 points gain, the end user thinks then its boosting 7 octane higher when it really is POINT 7 which is 0.7 which is no real gain.
They also will effect the O2s and over time using booster will reduce the life of them.
As to mixing pump gas with racing gas, some makers like Union76 do make an unleaded 100 octane but the issue is this type of gas burns at a slower rate which is not great for fast burning heads so if wanting to use it do not go overboard use no more then like a 25/75 race/street gas ratio.
With proper tuning and AFR you do not need either, have no knock and have good WOT timing.
I suggest you reconsider using that mucked up MAF as a cause.
I am actually talking about the Z. The T/A has never had any issue with KR...Apparently it is very common for the Z06s to have a little bit of KR in the 3900-4200 RPM range (2degrees or less). Apparently with the CR bump these cars also got more sensitive CPU programming to prevent detonation. It is very common to see low octane timing tables & a little KR in these cars from what I have read.
01-26-2004, 04:10 PM
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Here in S. Calif. Union 76 sells 100 octane. Then you get a blend chart off there web site. Super here is only 91. So if you mix the 100 with the 91 like 7 gal. of 100 to 4 gal. of 91 you get 96.7 , works for me. About $5 a gal. so I always blend.
