Timing HP loss.
05-21-2004, 10:08 PM
#1
Timing HP loss. Okay here is the deal.
Today I was talking to my tuner and he said something I disagreed with.
I am trying to figure out if my theory is correct or not.
The issue is timing.
I have 11.85:1 CR in my Camaro. 2 weeks ago while having it tuned I had nasty spark knock. The tuner pulled timing, then pulled more and then some more. I was around 18-19 degrees until about 5000 RPM's, and from there until 7000 RPM's I had between 19-21 degrees. I am running 93 octane.
I asked him "dosen't pulling all that timing out of the motor kind of make it pointless to have higher compression" He said no that timing dosen't really mean that much. I said "Well if I were to install a set of 6.0 heads that flowed identical to the LS1 heads I have and therefore lowering the CR to 11.2. Then ran 26-30 degrees of timing wouldn't my power be about the same?" He said no I would make more power running less timing with more compression.
I then asked him "If I were to add race fuel and add timing to the motor because of the better gas what would happen?" He said probally nothing that again timing wasn't really that important and the higher octane gas wouldn't do much.
I personially disagree with about everything he said but want to know if I am just plain stupid, or if he was having a huge brain fart.
Thanks everyone.
Today I was talking to my tuner and he said something I disagreed with.
I am trying to figure out if my theory is correct or not.
The issue is timing.
I have 11.85:1 CR in my Camaro. 2 weeks ago while having it tuned I had nasty spark knock. The tuner pulled timing, then pulled more and then some more. I was around 18-19 degrees until about 5000 RPM's, and from there until 7000 RPM's I had between 19-21 degrees. I am running 93 octane.
I asked him "dosen't pulling all that timing out of the motor kind of make it pointless to have higher compression" He said no that timing dosen't really mean that much. I said "Well if I were to install a set of 6.0 heads that flowed identical to the LS1 heads I have and therefore lowering the CR to 11.2. Then ran 26-30 degrees of timing wouldn't my power be about the same?" He said no I would make more power running less timing with more compression.
I then asked him "If I were to add race fuel and add timing to the motor because of the better gas what would happen?" He said probally nothing that again timing wasn't really that important and the higher octane gas wouldn't do much.
I personially disagree with about everything he said but want to know if I am just plain stupid, or if he was having a huge brain fart.
Thanks everyone.
05-22-2004, 08:29 AM
#2
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For every engine combo, at each rpm, there is an optimum point to fire the spark, based on many factors: octane (burn rate), compression, volumetric efficiency (amount of air+fuel), combustion chamber shape, etc. Retarding beyond that point lowers the total energy pushing the piston down. Advancing before that point also lessens total energy, and eventually leads to preignition.
No ifs, ands, or buts. It's the tuner's job to find that perfect point. Some combinations will want 40 degrees of advance, some 30, some 20, etc.
So if you change compression ratio by changing parts, you may or may not change the optimum amount of timing. But what you've really done is added an incremental amount of energy that will be released with each power stroke. Will this new combo need more, less, or the same advance? - who knows, and in fact it doesn't matter. There is more potential energy that can be extracted, regardless of where best timing advance is found.
As for your final question, you should trust your experienced tuner.
By the way, higher octance gas contains slightly less total energy than lower octane gas, and it burns slower. You go with higher octane when you need a slower burn due to the engine parameters (compression ratio, chamber shape, VE, etc); "high octane" makes power because it's in a highly-tuned engine, not because of the gas quality.
Joe B
No ifs, ands, or buts. It's the tuner's job to find that perfect point. Some combinations will want 40 degrees of advance, some 30, some 20, etc.
So if you change compression ratio by changing parts, you may or may not change the optimum amount of timing. But what you've really done is added an incremental amount of energy that will be released with each power stroke. Will this new combo need more, less, or the same advance? - who knows, and in fact it doesn't matter. There is more potential energy that can be extracted, regardless of where best timing advance is found.
As for your final question, you should trust your experienced tuner.
By the way, higher octance gas contains slightly less total energy than lower octane gas, and it burns slower. You go with higher octane when you need a slower burn due to the engine parameters (compression ratio, chamber shape, VE, etc); "high octane" makes power because it's in a highly-tuned engine, not because of the gas quality.
Joe B
05-22-2004, 09:32 AM
#3
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Originally Posted by Joe Bronikowski
For every engine combo, at each rpm, there is an optimum point to fire the spark, based on many factors: octane (burn rate), compression, volumetric efficiency (amount of air+fuel), combustion chamber shape, etc. Retarding beyond that point lowers the total energy pushing the piston down. Advancing before that point also lessens total energy, and eventually leads to preignition.
No ifs, ands, or buts. It's the tuner's job to find that perfect point. Some combinations will want 40 degrees of advance, some 30, some 20, etc.
So if you change compression ratio by changing parts, you may or may not change the optimum amount of timing. But what you've really done is added an incremental amount of energy that will be released with each power stroke. Will this new combo need more, less, or the same advance? - who knows, and in fact it doesn't matter. There is more potential energy that can be extracted, regardless of where best timing advance is found.
As for your final question, you should trust your experienced tuner.
By the way, higher octance gas contains slightly less total energy than lower octane gas, and it burns slower. You go with higher octane when you need a slower burn due to the engine parameters (compression ratio, chamber shape, VE, etc); "high octane" makes power because it's in a highly-tuned engine, not because of the gas quality.
Joe B
No ifs, ands, or buts. It's the tuner's job to find that perfect point. Some combinations will want 40 degrees of advance, some 30, some 20, etc.
So if you change compression ratio by changing parts, you may or may not change the optimum amount of timing. But what you've really done is added an incremental amount of energy that will be released with each power stroke. Will this new combo need more, less, or the same advance? - who knows, and in fact it doesn't matter. There is more potential energy that can be extracted, regardless of where best timing advance is found.
As for your final question, you should trust your experienced tuner.
By the way, higher octance gas contains slightly less total energy than lower octane gas, and it burns slower. You go with higher octane when you need a slower burn due to the engine parameters (compression ratio, chamber shape, VE, etc); "high octane" makes power because it's in a highly-tuned engine, not because of the gas quality.
Joe B
05-24-2004, 09:42 PM
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Originally Posted by LS1derfull
I have to disagree, higher octane race fuels have more BTU's and more potential energy than say 93 octane pump gas.
See http://www.medfordfuel.com/frequentl..._questions.htm
How much Octane do I need?
Only enough to stop preignition and/or detonation. Remember there are other important factors in power output than just octane. Octane is not the measure of the fuel's power output, it is only a measure of its resistance to preignition and detonation in an octane engine.
Only enough to stop preignition and/or detonation. Remember there are other important factors in power output than just octane. Octane is not the measure of the fuel's power output, it is only a measure of its resistance to preignition and detonation in an octane engine.
