losing hp when using race fuel?

[Ed the SOHC]

I missed the conversation with rage2 explaining when you lose hp if you use race fuel. Can you explain it again? and why?

[Ekliptix]

just a guess:
race fuel has a higher octane. higher octane gas is harder to burn/less combustable which is good to prevent detonation in high compression engines/FI engines/advanced timing. So if you are not close to detonation, using a less combustable gas may give you less power.

[rage2]

Alright, here's the conversation from yesterday. With buh_buh's car, he's not getting any detonation at all with his timing settings, so there's no need to go with a higher octane fuel. Higher octane fuel doens't magically give power, it gives power by raising the detonation limit so you can run more agressive timing, or more boost. Since he's not at the detonation limits, there's no need to move to a higher octane. With race fuel (VP103 for example), the burn speed is slower, so with identical timing/boost settings, you lose a bit of power. Of course in cars like mine, that lost power is easily recovered by adding another 10psi of boost and a few degrees of timing.

[Davan]

That makes sense. I always wondered the same thing.

I've been told by a few people I should run premium, and always said no. Now I can explain why not, make it sound like I know what I'm talking about...

[Speed_RaSiR]

What about high octane and VTEC? Any info on that?

[James]

So Is this true with Premium gas too?(91-91 octane) my car has only had Premium gas its whole life. But I wonder, is it really worth it?, its only a 1.6, or does engine size even matter?

[Davan]

I think compression and timing have more to do with it, than engine size.

Most VTEC engines require premium, do they not?

[rage2]

Originally posted by Davan
I think compression and timing have more to do with it, than engine size.

Bingo.

If the manufacturer recommends 87, use 87... any higher is completely useless.

[cocoabrova]

What about the Chevron Super Supreme Plus you can get in Van. (94 octane)... Is that going to make much of a difference over the 92 Esso here? And can someone please verify this thing that I heard about Hondas (especially VTEC-equipped) should NEVER use the 93 Mohawk Supreme-soemthing about the ethanol and Honda engines....

[James]

Originally posted by rage2


Bingo.

If the manufacturer recommends 87, use 87... any higher is completely useless.

So if Toyota says use 87, should i just switch to 87 now? because the car has only ever had 90+ octane. I dont care about the price of the gas, i was just curious if it is Actually doing anything?

[rage2]

Originally posted by James
So if Toyota says use 87, should i just switch to 87 now? because the car has only ever had 90+ octane. I dont care about the price of the gas, i was just curious if it is Actually doing anything?

90+ isn't doing anything for your engine.

[rage2]

Originally posted by cocoabrova
What about the Chevron Super Supreme Plus you can get in Van. (94 octane)... Is that going to make much of a difference over the 92 Esso here?

Sure, for my car, I can turn up the boost and get more power without detonation. 92 octane I can run 12psi max, probably 16psi for 94 octane.

For stock cars, it won't make a difference at all.

[G]

Originally posted by cocoabrova
What about the Chevron Super Supreme Plus you can get in Van. (94 octane)... Is that going to make much of a difference over the 92 Esso here? And can someone please verify this thing that I heard about Hondas (especially VTEC-equipped) should NEVER use the 93 Mohawk Supreme-soemthing about the ethanol and Honda engines....

I used Husky once in the Prelude and that was enough for me. It made my idle bounce all over the place at idle.

[G]

Originally posted by James


So if Toyota says use 87, should i just switch to 87 now? because the car has only ever had 90+ octane. I dont care about the price of the gas, i was just curious if it is Actually doing anything?

People buy Primium gas thinking that the quality is better but I don't think this is the case.

[James]

Originally posted by rage2


90+ isn't doing anything for your engine.

So, its basically pointless to be running premium? what about when i hopefully turbo the engine next summer? I will need premium then right? would it be better to just keep using premium till then, or is the difference marginal? sorry for all the dumb questions.

[rage2]

Originally posted by James
So, its basically pointless to be running premium? what about when i hopefully turbo the engine next summer? I will need premium then right? would it be better to just keep using premium till then, or is the difference marginal? sorry for all the dumb questions.

It depends... you'll know when your engine knocks =).

[Ferio_vti]

Some cars that require high octane end up getting some engine knock. I'm not sure what the deal with that is... Can anyone give some input??

[rage2]

Originally posted by Ferio_vti
Some cars that require high octane end up getting some engine knock. I'm not sure what the deal with that is... Can anyone give some input??

No new cars have that problem. Some high output engines are tuned really close to the limits of pump fuel, those engines are smart enough to recognize really light knock and retard timing and remember to keep the timing back to avoid future knock. Unless your car is a M car or AMG car, I doubt you'll run into such issues. Like I said, follow the manufacturer recommended octane and you can't go wrong.

[kenny]

For those of you who fill up with premium just for the additives that are only found in premium fuel, you can save yourself a small chunk of change by using midgrade fuel. Gas stations only carry two kinds of fuel, regular, and premium. Midgrade fuel is just a mix of the two. For those of you who fill up with premium for extra performance, when your car only needs 87 octane fuel, you're just wasting good money that can be spent on pho.

[2000impreza]

if you can advance your timing for higher octane i think it would be worth it. other wise its just a waste of money unless you are running some sort of forced induction.