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Discussion Starter · #1 ·
What are the advantages and disadvantages to 101+ octane "race" fuel. Is this harmful at all to our G's, or would it be OK to use at the track when getting time slips? Does it really help you squeeze out some extra HP? Don't know much about this stuff, so any help is appreciated.

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The thing with 101+ is how it burns. Higher compression engines usually require higher octane for more controlled burning conditions, otherwise detonation occurs. The reason people run race gas at the track is for cleaner combustion, and if their engine has modifications that would require such fuel. For example, if you set up your engine timing to be optimal, so that the spark ignights only a couple of degrees from TDC you may need high octane fuel to allow for no premature combustion (one form of detonation).


I hope that does explain it... it always makes sense in my head, but when I type it it sometimes gets confusing.

To be a little more helpful, this is what happens.

When the piston compresses the gas in the cylinder the temperature of the gas increases (simple chemistry - volume decreases, pressure increases, therefore temp increses.) As it increses it is possible for it to ignite prior to the spark. This is pre-detonation, it is an uncontrolled reaction and causes shockwaves within the cylinder which leads to the destruction of pistons and valves and such forth. The high octane gas ignites at a higher temperature, allowing you to increse compression, which increses the pressure put on the gas. So there you go. Welcome a small portion of combustion 101.

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Discussion Starter · #5 ·
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Gardiner

On a stock engine you would just be wasting money. A good quality 92-94 octane is all we need in our cars.
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Cool Gard. You learn something new every day! Thanks!

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Gard, especially with our ECU's it would take several days to realize any gain that may come with higher octane.

If we could prove that our knock sensor was actuating during driving with 91 octane, then a higher octane would help. But ift he knock sensor is not retarding timing during normal driving, you are wasting your money.

Even so we are talking about < 10 hp here (NA, turbo/SC is another story)
 

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With the Technosquare ECU, 91 octane gas is not good enough. I was detonating with Chevron 91 octane gas (CA sucks for good gas). Tossed in some 100 octane to pull the octane level up and the sucker made 4 more HP, but more importantly stopped detonating.
 

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We could hear the pinging that the engine was making.

4hp could be a fluke, yes. I want to keep higher octane gas in there to keep my engine safe though. Not being able to push much higher than 5000-5500rpm is pretty lousy.

About the consistency, my first run was 4hp lower than my 2nd run. So I take the performance numbers with a grain of salt. The other G35s that ran were pretty consistent though (+/- 1-2hp) (about 13 of us were there).
 

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The only time higher octane is of any benefit is if the car pings on the recommended grade, the timing is advanced, compression is higher than stock, or the car has forced induction. Pinging occurs when the spark occurs too early in the cycle. If the fuel/air charge is not compressed enough (i.e. harder to light) the charge explodes rather than burning at a controlled rate. The two means of eliminating this condition are to a) use higher octane fuel which is more resistant to ignition and burns slower and cooler (roughly 1 degree per point of octane) or b) retarding the ignition timing. This is exactly what happens when the knock sensor detects pinging. In response, the computer pulls out timing to prevent the pinging.


High octane fuel is a waste of money except for the following situations: Very old motor designed to run on higher octane fuel stock, Modified compression on your stock engine, seriously advanced timing on stock engine, turbo or supercharger on engine and you want to run higher levels of boost, or engine with lot's of miles that has carbon deposits built up in the cylinders which creates hot spots or raised compression which leads to detonation.


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Interesting comments from Chenga, as I have not heard a collective howl about detonation from everyone using a TS re-flashed ECU and 91. Is that the exception rather than the rule, or have I been missing similar comments?

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I'm going to try it out on the road with some Unocal 76 gas instead of Chevron. Hopefully I did just get a bad batch of gas.

Technosquare does advance the timing, but I would hope they wouldn't advance it so much that I'd need to add 100 octane to the crappy 91 octane in CA.

I'll keep posting when I find out if it's going to be ok. We're gonna stick a mic in the engine bay and drive around to see if it detonates.
 

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Too bad I don't know more about modding an Infiniti, but if you search on Autotap you might find some good help. On the Vette we can run an Autotap that tells how everything is running. Like I said earlier, your engine can be detonating and you would never know unless you had some electronic way of reading the sensors and ECU. Good luck
 

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You guys are, as I've said all along, a bunch of amateurs.

Look, it's a known fact that gas in California is for weenie cars. You can run a lawn mower with it, however, even a riding mower. That's about all it's good for. There is no gas produced in California by any refiner that is any good for any real performance cars. Period. Unlike the gas in New York and New Jersey, for example, -- gas for real cars with octane ratings as high as 94 or 95 -- you need to use additives if you live in a weenie state like California. Just open the Yellow Pages and look for Chemical Distributors. Then arrange to buy 5 gallon drums of xylene and toluene. Xylene carries an octane rating of 118, toluene slightly less, as I recall. These were the very fuels used by Formula One cars not too long ago. Mix them in equal proportions and add about 10% by volume to your gas. Problem over. As I said, you guys are a bunch of amateurs.
 

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<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Originally posted by brit1072

You guys are, as I've said all along, a bunch of amateurs.

Look, it's a known fact that gas in California is for weenie cars. You can run a lawn mower with it, however, even a riding mower. That's about all it's good for. There is no gas produced in California by any refiner that is any good for any real performance cars. Period. Unlike the gas in New York and New Jersey, for example, -- gas for real cars with octane ratings as high as 94 or 95 -- you need to use additives if you live in a weenie state like California. Just open the Yellow Pages and look for Chemical Distributors. Then arrange to buy 5 gallon drums of xylene and toluene. Xylene carries an octane rating of 118, toluene slightly less, as I recall. These were the very fuels used by Formula One cars not too long ago. Mix them in equal proportions and add about 10% by volume to your gas. Problem over. As I said, you guys are a bunch of amateurs.
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Post those pics of your pice of shit or go back to your hole, troll.

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Actually in Jersey the normal high octane is 93 with the occasional Shell station selling 94 octane to morons who are willing the pay the addition $1.50 on top of prices for 93 octane. I've seen a few shell stations selling 100 octane for about $5 (give or take) at the pump


 

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Toulene is 114, Xylene is 118.

Xylene will eat away at the rubber and plastic, so it's not safe to use a lot of Xylene in your gas mixture.

Toulene is safer, but it's used in explosives and drugs. Buying toulene in bulk is probably going to attract attention from the authorities.

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Originally posted by brit1072

You guys are, as I've said all along, a bunch of amateurs.

Look, it's a known fact that gas in California is for weenie cars. You can run a lawn mower with it, however, even a riding mower. That's about all it's good for. There is no gas produced in California by any refiner that is any good for any real performance cars. Period. Unlike the gas in New York and New Jersey, for example, -- gas for real cars with octane ratings as high as 94 or 95 -- you need to use additives if you live in a weenie state like California. Just open the Yellow Pages and look for Chemical Distributors. Then arrange to buy 5 gallon drums of xylene and toluene. Xylene carries an octane rating of 118, toluene slightly less, as I recall. These were the very fuels used by Formula One cars not too long ago. Mix them in equal proportions and add about 10% by volume to your gas. Problem over. As I said, you guys are a bunch of amateurs.
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