100 Octane
10-13-2004, 02:50 PM
#1
100 Octane Ran 100 Octane at the track the other day (not by choice, was low on gas by the time and had to fuel up @ $4.75 a gallon...) Anyway, I had a few good runs (for a newjack) and I was wondering how much of that (if anything) was attributable to the 100 Oct.
I think I read that the PCM is set up to work most efficiently on 93 Octane, so that the 100 probably didn't help much. Can someone confirm that????
I think I read that the PCM is set up to work most efficiently on 93 Octane, so that the 100 probably didn't help much. Can someone confirm that????
10-17-2004, 01:39 PM
#4
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Originally Posted by mako22
ttt any confirm on that?
10-17-2004, 04:55 PM
#6
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to understand you have to first know what that octane rating is telling you.
the higher the octane , the slower burning the gas is,
this is a good thing and a bad thing.
if you add 110 octane to a bone stock car and do nothing to tune it, then the fuel itself holds less energy and you will lose hp.
thats the bad side,
the good side is that when your fuel is slower burning it also means it is more stable and less susptable to detination, in a FI car it means you can turn the boost up safely without detination caused buy increased static compression,
on a NA car it means that you can increase the timing advance futher, which will spark the fuel earlyer in the compression cycle expanding the gas more as it is compressed, thereby raising the static compression (almost like boost) inside the cylinder resulting in more hp...
or something like that
the higher the octane , the slower burning the gas is,
this is a good thing and a bad thing.
if you add 110 octane to a bone stock car and do nothing to tune it, then the fuel itself holds less energy and you will lose hp.
thats the bad side,
the good side is that when your fuel is slower burning it also means it is more stable and less susptable to detination, in a FI car it means you can turn the boost up safely without detination caused buy increased static compression,
on a NA car it means that you can increase the timing advance futher, which will spark the fuel earlyer in the compression cycle expanding the gas more as it is compressed, thereby raising the static compression (almost like boost) inside the cylinder resulting in more hp...
or something like that
10-17-2004, 06:04 PM
#7
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Jaberwaki did a great job of explaining it. I also remember that CHP did a little test a while back on different octane levels (can't find it on their site though)They had a 327 SBC with like 9.5:1 compression. It was making max HP and TQ with regular 93 pump gas and XX total timing. Then they drained the fuel cell and added 100 octane and power fell some, so they bumped the timing up another 2 degrees. They were now where they were on the first run. The drained the fuel cell and put in some insane 110 or higher. Power fell even more. They had to increase total timing another 4 degrees just to get back where they were on the first run.
The point is that there is a kind of octane curve for every engine in a sense. You'll keep making the same (if not more) power as you raise octane levels to a point where the engine isn't burning the more stable fuel efficiently and power will begin to drop.
Wow this post got long very fast...
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10-17-2004, 07:50 PM
#8
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good point, i think something was missing from there test however , what they failed to point out was that 9.5 to one cr is VERY pump gas freindly, but with the 110 octane they could have bumped the compression up another full 2 points and found about 35-40 more hp.
10-20-2004, 10:14 AM
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"maybe your car's got lots of carbon buildup causing a lean condition...if u felt that 100 oct. helped?"
You're misunderstanding something.
Carbon buildup will increase compression enough to make 87 ocatane knock in some cars. A way to test if it is just octane knock is to put in 93 (or whatever) fuel and if the knock goes away, you know compression is to blame.
This has NOTHING to do with being lean.
You're misunderstanding something.
Carbon buildup will increase compression enough to make 87 ocatane knock in some cars. A way to test if it is just octane knock is to put in 93 (or whatever) fuel and if the knock goes away, you know compression is to blame.
This has NOTHING to do with being lean.
