110 octane

[meltman]

Originally Posted by EZWood

So i went down to my local napa, bought five gallons of 110 octane put it in on E. more power, better response. filled it up the rest of the way with 91, lost some of the power and response. what im wondering is what is the limit where its a waste for octane level? Anyone have an opinion on this?

You dont seem to understand what octane does in a fuel. Higher octane prevents detonation. It burns slower and more controlled. That allows you to run more ignition advance and/or boost in an FI car. That's what makes more power, running more agressive profiles - profiles that would damage the engine otherwise with detonation.

You dont benefit any from running 110 octane over premium as that is what the factory tune is done on. The ECU isn't going to run a more aggressive map than the one meant for premium because there ISNT one programmed.

Even if you went to the dyno and extracted as much power as possible from that fuel you're not going to net much of anything over premium without rebuilding the engine with much higher compression pistons for a higher static CR or boosting the hell out of it.

[serialk11r]

Originally Posted by meltman

Ah but note that he said he filled it with 91. Now it's probably just the placebo effect in this case, but 91 vs. 93 should have a small difference.

[meltman]

Originally Posted by serialk11r

Ah but note that he said he filled it with 91. Now it's probably just the placebo effect in this case, but 91 vs. 93 should have a small difference.

Only if knock is detected and the ECU retards the ignition advance.

So honestly... probably no difference in reality.

[serialk11r]

Originally Posted by meltman

Only if knock is detected and the ECU retards the ignition advance.

So honestly... probably no difference in reality.

The owner's manual says fill with 93, 91 is okay if that's all you have, but you may hear slight knocking. If the manual admits that you may get some knocking with 91, then I think it's safe to say there should be a small difference, easily perceptible or not.

[meltman]

Originally Posted by serialk11r

The owner's manual says fill with 93, 91 is okay if that's all you have, but you may hear slight knocking. If the manual admits that you may get some knocking with 91, then I think it's safe to say there should be a small difference, easily perceptible or not.

Again, only if you actually knock and the ECU detects and retards timing. There's a whole lot of factors involved.

[EZWood]

Originally Posted by jedibow

I am the link ninja!

http://www.ft86club.com/forums/showthread.php?t=8691

for those that are too lazy to read...

Factory fresh datalogging...

This doesn't tell us much. We would need two to compare. Whether you would like to call this a placebo effect, or whatever negative response, I noticed a difference in output and throttle response in very hot weather. What is a condition that would cause an engine to knock? I'm sorry I forgot, it's hot weather, low octane, high boost, and high compression. Now in case y'all in the Midwest have been living under a rock, aren't aware of the climate around the country, or flat out have a low reading comprehension, I live in one of the hottest regions in North America, I do not have access to a pump that produces an octane higher than 91 octane, and guess what? It is approaching the hottest time of the year for un in the northern hemisphere. So having said all that nonsense, I currently am experiencing conditions that meet two of the criteria that would cause an ecu to retard timing due to knock. The temperature is in excess of 110 Fahrenheit all day, and my vehicle has a high cr. I am not saying that my car can make full use of the higher octane, I'm not saying that this gas is by any means anything that could be considered economical, but hey we didn't buy a Prius, at least I didn't, and I'm having fun, in my book that is all that matters.