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Discussion Starter #1
is it worth it to get a race gas tune with stock internals
 

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Too Soon, Junior!
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110 octane will probably slow down the flame front propagation velocity enough that you'd lose a tad bit of power with your current mods and tune. I don't think it's necessary unless you're running a ton of advanced timing or high compression.
 

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On a stock motor, unless the tune is very agressive, anything over 87 octane will not do anything. The point of higher octane is to avoid detonation.

But on the other had race fuel smells awesome. I like to throw a few gallons in my car everyonce and a while just for the smell.
 

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On a stock motor, unless the tune is very agressive, anything over 87 octane will not do anything. The point of higher octane is to avoid detonation.

But on the other had race fuel smells awesome. I like to throw a few gallons in my car everyonce and a while just for the smell.
Thats false. The 87 part anyways. My car is tuned for 93. Im not 100% sure, but it lets you run more timing. If I put 87 in my car, the ****er would be pinging like a mofo.
 

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you can run some 104 and get tuned on it to throw a lil more timeing at it...

you will wont need c16 or nuttin like that...and btw 104 doesnt seem like anything special..not like c16/q16..

so its worth it if you want to throw a lil more timeing at it yes..but it just depends on how far you want to take it on stock motor..
 

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Slow what kind of wheels are on your GT? Car looks sexy. Needs a chin spoiler though
 

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Slow what kind of wheels are on your GT? Car looks sexy. Needs a chin spoiler though
That's an old old picture lol I don't even think his car is red anymore.
 

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yep car hasnt been red for 2 1/2 years now lmao and yes they where deep dish chrome 18 fr's
 

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On a stock motor, unless the tune is very agressive, anything over 87 octane will not do anything. The point of higher octane is to avoid detonation.

But on the other had race fuel smells awesome. I like to throw a few gallons in my car everyonce and a while just for the smell.
haha this made me laugh so hard bro
 

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Too Soon, Junior!
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Thats false. The 87 part anyways. My car is tuned for 93. Im not 100% sure, but it lets you run more timing. If I put 87 in my car, the ****er would be pinging like a mofo.
It's fairly true for stock motors :yes. Your car is supercharged, which means that the cylinder pressures are greater than NA engines. 93 octane fuel resists detonation more than 87, but the flame front propagation velocity is also slower, which means that the spark plug can fire further before the piston reaches TDC, a procedure called timing advance (colloquially called more aggressive timing, or more timing). The reason for this is that due to the advanced timing, the cylinder pressure will have built up enough to drive the piston back down for the expansion process of the 4 stroke engine by the time the piston has swung just a few degrees past TDC. With timing that's backed off (retarded), the piston is moving back down already when the cylinder pressures become high enough to actually apply force to the piston. This timing loss takes power from the engine, as essentially a significant percentage of the expansion process (the power stroke) is being wasted as the piston is expelling work to create a vacuum in the cylinder. Ideally, as soon as the piston reaches TDC, the cylinder pressure increases and forces the piston back down to actually use the entire expansion stroke to create power, but the timing of this is difficult to get perfect since there are a thousand different factors that affect flame kernel propagation and pressure expansion in a combustion chamber. The 93 octane makes it so that due to the increased cylinder pressure from the spark plug firing early and igniting the combustion elements during the compression stroke, the volatile environment caused by engine heat and pressure doesn't preignite the fuel near the piston and cause detonation. The timing tables from the factory on 4.6 2V motors are a bit on the conservative side, which is why 20bhp can be had from the 4.6 simply by increasing the WOT timing a few degrees.

The same principle applies to your supercharged engine. Due to the increased cylinder pressure and rise in temperature from before and after the combustion process, higher octane is required so that the increased pressure and heat does not ignite the fuel with disregard to the spark plug firing.

In a mostly stock NA engine, anything higher than 87 is just wasting money and a little bit of power. Even though the Diablosport and SCT 93 octane timing tables advance the timing by 2-3 degrees at WOT, this is conservative enough to run 91 or even 89 (if you're feeling lucky) without causing detonation.

Anyway, I'm only scratching the surface of engine operation here, but the moral of the story is that high octane fuel isn't necessary on a 4.6 2V unless it's tuned for it, runs high compression, or has forced induction (that includes nitrous since N2O is just FI via a chemical process rather than a mechanical one). The lowest octane fuel you can run without running into detonation is the fuel that will give you the most power.
 

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Discussion Starter #14
Ok so it's not worth it hahaha I was just checking... So if I had forged internals and an already aggressive tune would it be a good idea?... Idk if u noticed but the car is boosted
 

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Too Soon, Junior!
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There are guys running around with 600rwhp daily drivers that run on pump gas. The only situation where I'd use race fuel for a daily driver is if I were limping my car to the tuner after installing a supercharger or turbo running high boost. Other than that, it's not really worth the trouble or cost. For a track-only car though, it probably won't be a bad idea since the engine is going to be enduring quite a bit of punishment.
 

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asiansensation78 is right on the money! the bottom line is that the lowest octane fuel you can get away with will yield the most power.

we ran 110 octane leaded race fuel in our road race cars, but we were also running between 12 and 13:1 compression and advancing the timing so far that the spark plugs were firing before we hit the start button.

and i agree race fuel smells great!!!! we were even thinking of creating air fresheners in the shape of fuel cans that smelled like race gas! A close second, of course, is the smell of tires and brakes during extreme braking (from turn 5 at Road America, for example)!!

i'll finish by saying that running avgas (aviation fuel, such as 100 low lead) is not a good idea either as the specific gravity is lower than street fuel which causes it to run "leaner".
 

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It's fairly true for stock motors :yes. Your car is supercharged, which means that the cylinder pressures are greater than NA engines. 93 octane fuel resists detonation more than 87, but the flame front propagation velocity is also slower, which means that the spark plug can fire further before the piston reaches TDC, a procedure called timing advance (colloquially called more aggressive timing, or more timing). The reason for this is that due to the advanced timing, the cylinder pressure will have built up enough to drive the piston back down for the expansion process of the 4 stroke engine by the time the piston has swung just a few degrees past TDC. With timing that's backed off (retarded), the piston is moving back down already when the cylinder pressures become high enough to actually apply force to the piston. This timing loss takes power from the engine, as essentially a significant percentage of the expansion process (the power stroke) is being wasted as the piston is expelling work to create a vacuum in the cylinder. Ideally, as soon as the piston reaches TDC, the cylinder pressure increases and forces the piston back down to actually use the entire expansion stroke to create power, but the timing of this is difficult to get perfect since there are a thousand different factors that affect flame kernel propagation and pressure expansion in a combustion chamber. The 93 octane makes it so that due to the increased cylinder pressure from the spark plug firing early and igniting the combustion elements during the compression stroke, the volatile environment caused by engine heat and pressure doesn't preignite the fuel near the piston and cause detonation. The timing tables from the factory on 4.6 2V motors are a bit on the conservative side, which is why 20bhp can be had from the 4.6 simply by increasing the WOT timing a few degrees.

The same principle applies to your supercharged engine. Due to the increased cylinder pressure and rise in temperature from before and after the combustion process, higher octane is required so that the increased pressure and heat does not ignite the fuel with disregard to the spark plug firing.

In a mostly stock NA engine, anything higher than 87 is just wasting money and a little bit of power. Even though the Diablosport and SCT 93 octane timing tables advance the timing by 2-3 degrees at WOT, this is conservative enough to run 91 or even 89 (if you're feeling lucky) without causing detonation.

Anyway, I'm only scratching the surface of engine operation here, but the moral of the story is that high octane fuel isn't necessary on a 4.6 2V unless it's tuned for it, runs high compression, or has forced induction (that includes nitrous since N2O is just FI via a chemical process rather than a mechanical one). The lowest octane fuel you can run without running into detonation is the fuel that will give you the most power.
No i know that, but the OP is supercharged too. The argument I was making is, the guy said on the stock motor (stock compression, stock cams, stock heads) that its pointless to run above 87. Which is false. Even NA, the car will make more power with fuel with a higher octane rating.

But, the argument I was trying to make is that the op is supercharged too. I wasnt talking about NA cars lol. :hug
 

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yep car hasnt been red for 2 1/2 years now lmao and yes they where deep dish chrome 18 fr's
I thought they were FR's they look good. **** what color is your car now? Need to update that sig pimp
 

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No i know that, but the OP is supercharged too. The argument I was making is, the guy said on the stock motor (stock compression, stock cams, stock heads) that its pointless to run above 87. Which is false. Even NA, the car will make more power with fuel with a higher octane rating.

But, the argument I was trying to make is that the op is supercharged too. I wasnt talking about NA cars lol. :hug
i did a little research and stand corrected. cars will make more HP on higher octane fuel but it's not for the reasons i would have thought.
(this is why i love these forums...)

this article was from HotRod magazine and i thought it stated it quite well...

Conclusion:
Frankly, the results of our test were a bit confounding. We consulted the chemists at Super 104+ and our pal Tim Wusz at 76 to help figure out what had happened. Here’s what we learned:

First, the octane booster did work. However, we saw that octane alone does not deliver horsepower; it only allows more complete utilization of the hard parts in the engine. Wusz said, “An engine does not know what the octane rating of the fuel is, unless it is too low”; note that we made less power by adding booster to 91-octane fuel. The lower the octane of the base fuel, the more benefit you’ll get from octane booster.

Also, the Edelbrock heads on our test motor have high-efficiency combustion chambers that are very tolerant of low octane levels, and their aluminum construction helps, too. Older chamber designs may not be as efficient and may succumb to abnormal combustion more easily.

But most of all, we discovered that our presumption that higher-octane fuels burn slower than lower-octane fuels (and therefore require more ignition lead) is largely incorrect. There are too many other fuel-formulation issues at work to assign a general rule about octane. Race fuel tends to have a more powerful formulation than pump gas, regardless of octane rating, because it is denser and can release more power and heat. (Note that we made the best power with 114 octane with the least ignition lead, indicating it had the fastest burn time.) California pump gas is blended with methyl tertiary-butyl ether (MTBE), alcohol, and other ingredients damaging to performance. Knowing what we know now, we’ll always experiment with ignition timing—both higher and lower settings—when we change fuels rather than presuming that more power can be made with more octane due to more timing.
 
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