High octane

[Mike Kast]

How high is to high? I always run amaco 93, I have heard there's a place near charlotte raceway that sells racing fuel. I thought that to high an octane can burn up the pistons. You guys with the chips can get away with a higher octane than I can with a stock 3.0, right?
The reason I'm asking is because of something I just read on the "cleaning fuel injectors" thread thats been floating around since 2001

[Zeke]

Mike, I'm far from an expert, but as a racer of many years, I've certainly heard my share of theories. Octane is a pre ignition suppressant. In other words, it's harder to ignite and may burn slower once it's ignited. I don't see how that could be harmful to your pistions, much less burn them.

Too much octane to my sources simply means less than optimal performance and a waste of your fuel money. IMHO, though, it is better to error on the side of protection for your engine. But, I wouldn't put much race gas in there unless you know what you are doing.

Race gas is formulated for racing. I'm not trying to be silly or flipant. There are compounds used in race gas that are not needed for everyday driving and if allowed to sit, may be harmful to your system. There certainly are not any injector cleaning agents in race gas as the formula calls for performance. The gas is not laden with non energy producing compounds. That having been said, some of the stuff I've heard identified as race gas ingredients would take the paint off your car.

I digress for a moment: I once visited a race track for an event shortly after a Formula 1 test session. They left behind an empty 55 gallon drum with a few drops of fuel in the bottom. I had to explore. I've never smelled anything like that before or since. That was back in the days of unmonitored fuel composition and the stuff was said to cost about $40 a gallon according to Bob Varsha, then of ESPNII.

[sammyg2]

Premium gasolines usually have a slightly better detergent additive package so they "might" clean injectors a little better, but I doubt you would be able to notice the difference. Even regular grade gasolines now days have good detergents. If you have a stock US spec 3.0 you are wasting money burning premium and going to an even higher octane racing fuel will only empty you wallet and could reduce your performance.
If I were you I'd run Chevron regular or midgrade and see if you detect and difference. Chevron has a very good detergent package. If your engine runs better on premium it probably means you have more ignition advance that the engine was intended to have.

[Mike Kast]

I am completely clueless about all of this so I thought I'd throw it out there. Thank you guys. I have no clue if it runs the same on regular or premium and until I get it back on the road I can't experiment. There are no Chevron stations around here as far as I know. I saw a thread some time back on "What is the best gasoline" And noted that no one voted for Amoco and Chevron was the clear winner.
But as far as I can tell my choices are Exxon and Amoco.

I am thinking all my assumptions about octane are based on advertising hype and I really know nothing at all about it more than what you guys just wrote...
Its always interesting when I become enlightened about my total ignorance about something I have always taken for granted...lol...

[KFC911]

Mike, I've always run Amoco 93 (exclusively) in my sports cars (and boat) too (...but the cheaper 87 stuff - no particular brand) in my other cars. I've always known that I might be pi$$ing my money away, but it has given me piece of mind to 'think' that I used the cleanest gas available. Although I haven't used Techron yet, I think you'd be just fine w/ the 93.

[targa911S]

Now my early S car is supposed to run on at least 98. It runs OK on 93 but as much as anybody can say about wasted money, it just plain runs better on 100 octane racing gas. Idles better for sure. I can't say that it makes a noticable "at speed" differance but at idle..it has a purr like a happy cat. Now this is a car with high compression from the factory and MFI. I can't say about the CIS and how it would respond. My guess is that you would be wasting your money and possibly hurting your engine more than helping.

[Mike Kast]

I have run about 4 bottles of the stuff through my car since I've owned it. And it helped but the injectors were the symptom. The source of the problem was coming from the tank. The tank has been cleaned. Now I am dealing with the residual effects of all the crap that was in my tank.

My ruff estimate is that 11,700 gallons of gas has been run through that tank over the last 25 years. There is a whole bunch of potential for contaminents entering the system at that volume. Plus the varnish...

[sammyg2]

When I first bought my SC the injectors were suspect also. Instead of trying to add magic stuff to the fuel I elected to change all the injectors and the fuel filter. I paid about $21 each for the inectors.

Many, many years ago I had an old VW bug as my daily driver. A friend convinced me to try this special fuel cleaner additive. I did. About 20 fuel filters and three fuel pumps later I pulled the fuel tank and had it professionally cleaned.
the additive did it's job, to the point where it stripped most of the inside of the fuel tank and everything else down to clean metal. Hand fulls of crap ended up clogging everything and messing up an otherwise fine running car.
That was the last time I ever used a fuel additive.

[Mike Kast]

Sammy...
I am also suspect of magic potions. $21 each for injectors? Where? I guess that was some time ago. I'm not ready for that yet anyway. But if it comes to that, I will do it! It has been an expensive Porsche month for me... And everything I am doing is basically maintenance. No upgrades. I'll post pictures when I'm done. I'll have the finest looking right rear wheel well in town! Cleaner than its been in 20 years I bet. Every item meticulously detailed. And as soon as I start her up, it will never look that good again...lol... Ahhhhhhhhhh...life is good!

[dd74]

I used 100-octane in my SC engine earlier this year. It idled a bit better, but truly did loosen a whole lot of crap...in my wallet.

[sammyg2]

I just checked my source, prices jumped big time. Less than 2 years ago I paid $21 each for injectors, now they are almost twice that for new Bosch. Maybe something to do with the exchange rate of the dollar vs. Euro?

[Mike Kast]

well then... Since this seems to be a somewhat popular subject-
This thread here and the subject in general has me wondering
Any Toluene veterans out there?

(This is purely a a curiosity question, I am already convinced 93 is more than enough for me and my 3.0)
What about the off the shelf octane booster products? Why not buy a couple of bottles of those instead of racing fuel?

[briankeithsmith]

I run 100 octane in my 930. I primarily do it because I track the car and have already experienced first hand the issues that can occur from running 93 octane on the track, and pre-detonation.

Anyway, my car does run slower with 100 octane and idles rougher until it is warm. But, it is saving my pistons I guess...

Brian

[briankeithsmith]

And Mike, I get my 100 Octane at the Petro Express just down the street from Charlotte Motor Speedway (2 miles from my house).

If you check in your area, I am sure there is at least 1 station that will have it.

$4/gall.

Brian

[sammyg2]

Ok, we'll go over this one more time. More octane WILL NOT produce more power. It is not better for your engine. It is something you need only if you have increased the effective combustion pressures on your engine too high for regular gas.

I've working in the refining business for 23 years.
In the early 80's I made my own racing fuel, the best I could do was 117 octane. I used platformate as a base, added neutralized alkylate, added toluene and as much tetraethyl lead as I could keep suspended.
The engine I blended this for needed it as it was a supercharged Chrysler Hemi that was radically built. Basically a hand grenade. It needed all the octane I could give it because I was seriously overdriving the blower on an engine that had too much static compression. basivcally an alcohol spec motor running on gas.

You can put anything you want in yor tank and it will not give you more power with your stock engine except a hydrocarbon/nitrogen molecule like nitromethane. Triple nitrogen/hydrocarbon molecules would be even better, we refer to them as tri-nitro, as in trinotrotoluene(TNT) or glyceroltrinitrate (nitroglycerine). They are a little hard on the pistons.

In that link someone refers to triptane and says it will increase octane to 140. Not bloody likely. If that were true the oil refineries would be all over it.
Octane booster is a total joke. It is mostly alcohol. methanol, ethanol, whatever. If it says it will increase octane 4 points that means 4/10ths of one octane.

So, unless you change you compression ratio of mess with the timing a whole bunch, you don't want or need more octane on a stock 3.0.

[red-beard]

Thanks Sammy! A sane voice in the choir...

[Superman]

No. High octane gas will not hurt anything. Low octane gas can burn pistons, but not high octane gas. The difference is in the temperature/pressure combination at which it will spontaneously combust. High octane gas combusts at a higher temp/press combination. This allows tricks like high compression pistons.

[Mike Kast]

thanks Sammy. I'm not looking for more octane for power. Someone on another post mentioned that his mechanic told him to mix racing fuel and techron in one tank to clean out the system before he brought it to him for a tune up. Its been so long since I have driven my car I don't hardly remember why I care.
I'm just curious...

[beepbeep]

Sammy:

very interesting reading, thanx for the info. Now one simple question:

What about using nitromethane in street car? What are the effects and how should engine differ from stock if running on, say 20% nitro and 80% gasoline?

Reason i wonder is that i fiddled with model engines as a kid, blending lot's of nitro in the mix.

Thanx!

[Quicksilver]

Originally posted by beepbeep
Sammy:

very interesting reading, thanx for the info. Now one simple question:

What about using nitromethane in street car? What are the effects and how should engine differ from stock if running on, say 20% nitro and 80% gasoline?

Reason i wonder is that i fiddled with model engines as a kid, blending lot's of nitro in the mix.

Thanx!

Nitromethane makes for lots of detonation, which will eat your pistons up in a matter of seconds. It works fine when the engine is correctly designed for it but a gasoline engine can't take it. Nitro has a higher quantity of stored BTUs then gasoline (by volume). This means that you are releasing more heat energy on each combustion stroke. Nice and easy, just tip the bottle. There is a reason that they call nitro "Pop". It reduces octane drastically and makes an engine detonate like crazy (pop, pop, pop...)

A diesel is designed to fire solely from detonation. A glow plug engine is just a step removed from being a diesel engine and is designed to deal with this type of combustion extreme. The only real limitation for a model engine's nitro intake is once you get past 70% nitro you are really limiting the quantity of oil you are putting in the motor.

Drag cars can use nitro because their motors have a required life span of about 5 seconds. I read a funny story quite a while ago that pointed out the extreme detonation that is normal in a top fuel car. The funny car in question had the magneto (distributor) blown off the car at the 60' mark on its run. It still completed its 1/4-mile in less than 5 seconds with no ignition system! It was completely fired by detonation.(Is there a Top Fuel Diesel class?)


Wayne