high octane fuels

[Indy GT]

Thanks Kendall! I appreciate your technical posts as well as Shadowman's, BlackIce's and others. We do what we can....

Long winded at times (which undoubtedly Frank will comment) but just trying to help others understand some of the misconceptions and complexities of our cars and engines.

 

[fjpikul]

Kendall, don't encourage the engineers.

 

[t32b]

$1.59/gal? Ahh the benefits of government subsidies...

We got the e85 up here and i run it in all my high hp blown cars. 1.59 a gal right now:banana and i only have to drive no more than 10-20 miles to get it.

 

[mousecatcher]

Because octane is a measure of detonation resistance, a higher octane fuel actually burns or combusts at a slower rate than a lower octane fuel.

I don't see how that follows.

Just found this: http://www.nsxprime.com/FAQ/Miscellaneous/FuelAdditives.htm

 

[Indy GT]

Mousecatcher-

We have been down this road before. My reference to "This concept does take some thought." was specifically for you.

I again ask YOU to explain why you do not think my statement is factual.

My authority is the engineering textbook, "Internal Combustion Engines and Air Polution" by Edward F. Obert Professor Mechanical Engineering, University of Wisconsin.

Will you resond this time?

 

[BlackICE]

From mousecatcher's link

...When you can precisely control the point at which the fuel will ignite, maximum performance of the engine can be achieved, and power-robbing knock and ping will be eliminated. Knock and ping are a result of abnormal ignition, or multiple flame fronts colliding within the combustion chamber during the compression stroke...

...The burn rate of a fuel is a measurement of the time required for complete combustion of the air/fuel mixture. The notion that octane ratings affect the burn rate of fuel is about 180-degrees from reality; burn rate is a function of several variables, and the two are completely independent, although there is generally a correlation between octane ratings and burn rates...

I think we are playing with semantics here.

The important thing to remember is that a FGT fueled with pump gas in the range of 91-93 octane isn't running anywhere near the MBT (Max. brake torque) spark advance. Therefore, by increasing the octane rating of the fuel, one can, with the adjustments to the A/F and spark curves, extract more torque and horsepower from the engine than otherwise possible with fuels of lessor octane. But as Indy stated this is not risk free and far from easy to optimise under all operating conditions. The tuning parameters are multi-dimensional, based on an infinite combination of RPM, load, IAT, ECT, spark advance and a/f ratios. Ford chose to setup the car for bullet proof operation and is VERY conservative in it's tune. It leaves some HP on the table on high RPM and it the throttle response is less than ideal during transient operation. Many have aftermarket tunes focus primarily on top end performance numbers, maximizing torque at high loads and RPM; dyno numbers will be impressive to the customer, while part throttle low RPM operations are less than stellar.

If you car runs great with your current tune and gas, filling up with higher octane gas will do NOTHING for HP without modifying your tune as well.

Here is some more reading material for Frank

http://www.sae.org/students/presentations/powertrainc.ppt

 

[mousecatcher]

Mousecatcher-

We have been down this road before. My reference to "This concept does take some thought." was specifically for you.

I again ask YOU to explain why you do not think my statement is factual.

My authority is the engineering textbook, "Internal Combustion Engines and Air Polution" by Edward F. Obert Professor Mechanical Engineering, University of Wisconsin.

Will you resond this time?

sorry, i didn't realize i hadn't responded some other time.

octane is a measurement of resistance to pre-ignition, not a measurement of rate of flame front propagation. seem like independent properties to me. i will review the text you cited (and BlackICE's reference) and reply.

 

[JOETWINT]

Just want to make sure the FGT owners here on the Forum understand and do not misinterpret "octane" for "power". The oil companies over years of implicit advertising have insidiously paralleled to two concepts to the general population. I would hope our FGT constituency is smarter than the general automotive fuel purchasing public and can understand and disassociate the two terms.

Octane in and of itself has nothing to do with BTU (or potential heat energy) content of a fuel. It is only a measure of detonation resistance which becomes more necessary as internal BMEP (brake mean effective pressure) increases due to increased compression ratio or advanced spark timing. Because octane is a measure of detonation resistance, a higher octane fuel actually burns or combusts at a slower rate than a lower octane fuel. This concept does take some thought. It is so convenient to think that filling the fuel tank of your 87/91 octane engine with 93+ octane fuel will get you more power…..but it just will not and you are wasting your money.

Trust me that I do not believe just adding octane on a given tune can make more power alone.........rather the car was able to be tuned more aggressively (timing,boost) on it as a result of it having higher octane rating.Thanks anyway though:thumbsup

 

[Shadowman]

I will add just one more thing

The operational differences between 91 and 93 are certainly measurable and yet modest however if one were to simply use 104-116 octane fuel and not increase the static or created compression and/or add more lead to the spark aka advance the gal will actually lose power; now for many this will make no sense at all.

Takes care

Shadowman

 

[JOETWINT]

I will add just one more thing

The operational differences between 91 and 93 are certainly measurable and yet modest however if one were to simply use 104-116 octane fuel and not increase the static or created compression and/or add more lead to the spark aka advance the gal will actually lose power; now for many this will make no sense at all.

Takes care

Shadowman

Absolutely!

 

[kumar]

I will add just one more thing

The operational differences between 91 and 93 are certainly measurable and yet modest however if one were to simply use 104-116 octane fuel and not increase the static or created compression and/or add more lead to the spark aka advance the gal will actually lose power; now for many this will make no sense at all.

Takes care

Shadowman

yep

I just need it to be able to run 17psi/16 deg timing on 93 versus 22psi/18-20 deg timing on 104.

Adding the 104 to the 17psi/16 deg tune would make less hp.

 

[kumar]

anyone have opinions about torco?

This chart is apparently 1 quart of torco and 10 gallons of 91 octane pump gas.

Torco is convenient in that you can just carry a quart container with you in the car and add whenever you want.

 

[BlackICE]

Torco uses MMT. Do a search on MMT octane and make your own opinion to whether or not to use the product. Chose your boost product, MMT, MTBE, ethanol, toluene, xylene, or just use race gas.

 

[OzGT]

I used to be a fan of the NOS racing and used it a lot in my '03 Cobra but it I kept getting plug fouling, which I now believe is a side effect of the MMT in it(what my tuner reckons). It was made worse in periods where the car was in different places like paintshops and detailers as the idiots would just jump in and move it before it was warmed up despite the fact you can tell easily when depressing the accelerator too hard that it's cold (given it will splutter). So I will definitely avoid products using MMT from now on.

 

[ThatPhilBrettGuy]

Toluene smells nice if nothing else :biggrin

I remember watching the F1 cars of the 80's and that heady sweet smell as they roared past. They were running up to 80% toluene in the fuel. 5.5 bar boost and 1100-1300bhp...out of a 1.5L (91.5 CI) 4 cylinder. Unreal.

 

[BlackICE]

Toluene works well if you keep the percentages below about 30%. Too much and it doesn't vaporize well, leading to hard starting and misfires, especially in cold weather. The F1 guys heated the fuel.

From

http://en.wikipedia.org/wiki/Toluene

Note the last sentence. If you buy too much of the stuff, you may get a visit from the DEA!


Toluene can be used as an octane booster in gasoline fuels used in internal combustion engines. Toluene at 86% by volume fueled all the turbo Formula 1 teams in the 1980s, first pioneered by the Honda team. The remaining 14% was a "filler" of n-heptane, to reduce the octane to meet Formula 1 fuel restrictions. Toluene at 100% can be used as a fuel for both two-stroke and four-stroke engines; however, due to the density of the fuel and other factors, the fuel does not vaporize easily unless preheated to 70 degrees Celsius (Honda accomplished this in their Formula 1 cars by routing the fuel lines through the muffler system to heat the fuel). Toluene also poses similar problems as alcohol fuels, as it eats through standard rubber fuel lines and has no lubricating properties as standard gasoline does, which can break down fuel pumps and cause upper cylinder bore wear.

Toluene has also been used as a coolant for its good heat transfer capabilities in sodium cold traps used in nuclear reactor system loops.

Toluene can be inhaled for its intoxicating effects. Low to moderate levels can cause tiredness, confusion, weakness, drunken-type actions, memory loss, nausea, loss of appetite, and hearing and color vision loss. These symptoms usually disappear when exposure is stopped. Inhaling high levels of toluene in a short time may cause light-headedness, nausea, or sleepiness. It can also cause unconsciousness, and even death. Toluene may negatively affect kidney function.[7]

Toluene has also been used in the process of removing the cocaine from coca leaves in the production of Coca-Cola syrup.

 

[t32b]

Bingo, you're right. I don't know why power would be down. I could venture a guess about slower combustion, maybe even incomplete combustion, but don't really know.

I will add just one more thing

The operational differences between 91 and 93 are certainly measurable and yet modest however if one were to simply use 104-116 octane fuel and not increase the static or created compression and/or add more lead to the spark aka advance the gal will actually lose power; now for many this will make no sense at all.

Takes care

Shadowman

 

[AlohaGT]

Toluene can be inhaled for its intoxicating effects. Low to moderate levels can cause tiredness, confusion, weakness, drunken-type actions, memory loss, nausea, loss of appetite, and hearing and color vision loss. These symptoms usually disappear when exposure is stopped. Inhaling high levels of toluene in a short time may cause light-headedness, nausea, or sleepiness. It can also cause unconsciousness, and even death. Toluene may negatively affect kidney function.

After reading this thread, I'm afraid I feel like I've been snortin' this stuff. :confused

 

[Fast Freddy]

anyone have opinions about torco?

This chart is apparently 1 quart of torco and 10 gallons of 91 octane pump gas.

Torco is convenient in that you can just carry a quart container with you in the car and add whenever you want.

DO NOT USE TORCO

it f-d my vipers tune (went lean) by corroding my spark plugs, fuel injectors and 02 sensors. i was mixing 1 quart with 13 gallons. it resists detonation but has terrible side effects......

you can get two tunes for your GT and install a flip switch that allows you to flip a switch to advance your timing like i have on my Lightning. advance timing tune for race gas and standard timing for pump gas all with the flip of a switch. Diablo Revolution is one to name a few.......

 

[mousecatcher]

My authority is the engineering textbook, "Internal Combustion Engines and Air Polution" by Edward F. Obert Professor Mechanical Engineering, University of Wisconsin.

I reviewed [parts of] that textbook (great text, BTW) and didn't find anything linking octane rating to rate of combustion. in fact, the opposite.

section 9-12 talks about a high combustion rate causing an apparent knock (and thus decrease in octane rating) using "the standard instrumentation", but that this is a false reading caused solely by the rate of combustion and not because of detonation. a fix to the instrumentation to prevent this false reading is then proposed. (the 3rd edition, my reference, was published in 1973, so one thing i'd love to know is what has changed since then.)

parts of chapter 4 talk extensively about burn rate and there is no mention of octane rating.

even in my most pessimistic (to my argument) reading of the text, the only link i see is that a faster burn rate might translate to a lower octane rating, however the converse is not true.

in the link i posted, you can see that Sunoco Race Fuels states that octane and burn rate are not linked, and in fact their fastest burning fuel has one of the highest octane ratings (the opposite of what you are claiming is the relationship between these variables). you can also find this information directly on Sunoco's web site. VP Racing Fuels isn't 100% clear, but they make an attempt to dissociate these two variables from each other.

now then, i leave it to you to point out where the text leads one to conclude that higher octane = slower burning. i certainly could be wrong; i didn't "study" the text, i just gave it a cursory review. but i also use the statement from Sunoco to support my position.

it's a thick text so i think it's fair to ask you to explain your conclusions, as opposed to my investing hours of unguided study.

:cheers