Quote:
Originally Posted by Vegas69
I'm surprised you spent so much time tuning on fuel you will rarely use. Did you dyno it in street trim?
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Sorry -- but I have to say that statement is just a bunch of hoohaw...
You'll guarantee that a motor won't be AS susceptible to detonation on the dyno with higher octane fuel... and especially the use of this for finding (experimenting with) the max timing settings etc without running into trouble. This is an extremely smart decision on the dyno operators part.
The actual power difference between 91 octane and say 100 octane is so negligible it's hardly worth discussion. And it's been proven that the tuning set up for 91 octane and 118 octane can be exactly the same - same jet sizes - same timing.
Having said that.... If I tuned on a dyno with 100 or 110 then I'd probably pull out 2* of total timing for the street -- AFTER I found the max I could run - just because pump gas is so "variable" these days.
Octane rating is defined as the resistance to detonation a fuel has in an internal-combustion engine. The higher the number, the more resistance it has. That is why engines with higher compression require higher-octane fuel. As a result of its resistance to detonation, it has a resistance to burn as well. This resistance to burn is a non-issue in motors tuned to the edge; the edge being just before detonation occurs. When a pump-gas engine is subjected to a higher-octane race fuel, it may result in a decrease in power from an incomplete burn.
Here's the deal -- the higher the octane - the less resistant to detonation -- that also means it's less resistant to BURNING as well.... If you're going to run an engine on the ragged edge - then best to run on higher octane and not hurt the motor - particularly if you have maximum timing etc so max power. But todays OXYGENATED fuels actually burn really well because they carry what? Extra oxygen! In a N/A engine that's a plus!
Stick 100 or 110 in an engine tuned for best power on 91 and you might see a LOSS of power... not an add. Funny -- and OPPOSITE of what one would think huh!