Topic: Racing gas in a SOHC4

[Spikeybike]

A gas station down the way from my house has recently started selling 100 octane.

i'm sure eventually my curiosity will get the best of me, just wondering if anyone has tried it in a "stock to lightly modified" sohc4 .. 

 

[BlackMax]

it won't do a thing for you.   "Racing gas" is just regular old gas with additives so that it burns a bit slower and can handle more heat before it self-ignites (as if when you have a 14:1 compression ratio or a blower pumping 30 psi or ridiculous spark advance).

Energy content:

   gasoline 89 octane-       114,000 btu/gallon
   racing gas 100 octane-   114,000 btu/gallon (actually, probably slightly less )

I'd skip it;  but if you must...

[michrobi]

If you want gas that makes a difference, regardless of the internal combustion engine you use it in, try a couple gallons of 130 octane avgas (aviation gasoine). It's green like lime coolaid, won't harm your engine, and as close to alcohol performance as you can get with commercially available petrol. These days it's a little difficult to find, but check your local small craft airport. One of the private fuel suppliers will probably sell you some.

The 100 octane gasoline you are thinking about is the same as 91 octane with a little +10 octane boost additive mixed in. A bottle of Redline race additive will last for years and be just as good if not better.

That info above is from my Dad. He's a shift super at the Chevron refinery. You used to be able to buy avgas at a Texaco nearby, but that's been years ago.

[BlackMax]

The point is, if your compression ratio is 9:1 you need 87 or maybe 89 octane gas.  Any higher and you ONLY doing the following:

1) spending more money
2) going slightly slower, all other things the same
3) depending on the additive used to increase octane, damaging the engine (while going slower)

[Gordon]

The point is, if your compression ratio is 9:1 you need 87 or maybe 89 octane gas.  Any higher and you ONLY doing the following:

1) spending more money
2) going slightly slower, all other things the same
3) depending on the additive used to increase octane, damaging the engine (while going slower)

Exactly.  It's a common misconception that octane = power.  But it doesn't.  I'm sure the gas companies aren't in a hurry to dispel that myth either, since they can charge more for higher octane.   

[Old Scrambler]

Somewhere in my readings HONDA reported the lower octane fuel actually performed better at very high rpms.  They switched down to the low 80s for their race bikes many years ago.

[Achmed]

This is just a curiosity for me, but, ridiculous spark advance+high octane gas=what kind of performance compared to a finely tuned stock setup?

[michrobi]

Octane has little to do with performance. It's a measure of resulting sound, not burn potential. In the 80's when manuals were written about gas and the effect on engines, it was leaded gas they used, not unleaded. A very different chemical. Adding alcohol to an engine, 9:1 or otherwsise, will = more power. That has absolutely nadda to do with octane, it's about combustion velocity. Try the avgas, you'll like it.

[NitroHunter]

Here's an interesting link...

http://www.drivingethanol.org/motorsports/racing_fuel_characteristics.aspx

"For example, if gasoline is run at its preferred max power air fuel mixture of 12.5/1, it will release approximately 19,000 BTU's of energy, where ethanol run at its preferred power stoichiometric of 6.5/1 will release approximately 24,400 BTU's. By comparison, methanol releases slightly more, about 27,650 BTU's. The more ethanol there is in gasoline, the more powerful it is as a motor fuel. Typically, you can expect at least 5% more horsepower at the rear wheels of a vehicle running on E-85 than one burning gasoline only."

As far as race gas in a stocker goes, in my XH/S record holder (SOHC Honda 750, Stock) I ran ERC 110 gasoline. The manufacturer told me it kept the engine running cooler (than the very high leaded fuels like Av Gas) by removing more heat during the exhaust stroke. The circle track guys didn't tend to overheat when using this fuel.
Performance wise, IN THIS BIKE, it was worth .15 second and 1.5 mph on the dragstrip in back-to-back runs the only time I tested it against pump gas.
On the street, it was worth a bike-length over my buddies 750, and would pull 5-7 mph greater top end.
It also cost $3.85 a gallon back when premium was about 98 cents.
But the exhaust smelled really good...

[BlackMax]

Here's an interesting link...

http://www.drivingethanol.org/motorsports/racing_fuel_characteristics.aspx

"For example, if gasoline is run at its preferred max power air fuel mixture of 12.5/1, it will release approximately 19,000 BTU's of energy, where ethanol run at its preferred power stoichiometric of 6.5/1 will release approximately 24,400 BTU's. By comparison, methanol releases slightly more, about 27,650 BTU's. The more ethanol there is in gasoline, the more powerful it is as a motor fuel. Typically, you can expect at least 5% more horsepower at the rear wheels of a vehicle running on E-85 than one burning gasoline only."

As far as race gas in a stocker goes, in my XH/S record holder (SOHC Honda 750, Stock) I ran ERC 110 gasoline. The manufacturer told me it kept the engine running cooler (than the very high leaded fuels like Av Gas) by removing more heat during the exhaust stroke. The circle track guys didn't tend to overheat when using this fuel.
Performance wise, IN THIS BIKE, it was worth .15 second and 1.5 mph on the dragstrip in back-to-back runs the only time I tested it against pump gas.
On the street, it was worth a bike-length over my buddies 750, and would pull 5-7 mph greater top end.
It also cost $3.85 a gallon back when premium was about 98 cents.
But the exhaust smelled really good...

E85 "Flex Fuel" vehicles get 20-30% WORSE mileage on ethanol compared to gasoline.  That can't really be debated.   Eth/Meth contains way less energy per gallon than gas.  So, you have to use more of it, to do the same work.  The only way around this:  You could build a totally different engine, that could utilize the thermodynamic advantage that eth has over gas......and break even or possibly even come out ahead.  But again, you'd have to build a whole new engine, and it would be one that wouldn't run on pump gas.   The trick is, although eth/meth has was less energy dense per volume, it does have a higher octane rating (about 110).  So, you could build a 14.5:1 compression engine, and run it on E100.   In this case, you would increase the thermodynamic efficiency of the fuel.  This means that burning the fuel would produce more mechanical energy (transferred to the crankshaft) and less heat energy (out the exhaust) when compared to the same fuel (eht/meth) in the 9:1 compression engine.  This is where ethanol could catch or even pass gasoline; but, you CAN'T DO IT IN THE SAME ENGINE.  If you have lower compression, ethanol is a total loser.  If you have high compression, ethanol works, but pump gas doesn't.   This is why Flex Vehicles are garbage.  They work with gas, but get 30% less mileage if you use E85. 

1) Ethanol contains about 79,000 BTUs per gallon PERIOD
2) Gasoline contains about 114,000 BTUs per gallon, PERIOD
3) Diesel contains about 130,000 BTUs per gallon, PERIOD

......just wanted to point out a few things.

http://www.fueleconomy.gov/feg/flextech.shtml

[tinman25]

But the exhaust smelled really good...

im with you there is something about that smell

[Beans]

avgas is awesome. used to use it in my stand up jet ski last year when I had it and it made a big difference.   I also have used it in my dirtbike.  its now been harder for me to get since they won't sell it to me any more at my local airport.

[Leino]

I don't know are we talking about the same E85 they sell in Sweden, but I've seen some
impressive results with E85 on dragbikes.
Much cheaper than any racegas and works very well in high compression Pro Street Bike engines and of course in turbo's with some serious boost too.

Unfortunately they don't sell that stuff in Finland so I'm stuck with racegas over 5 times the price...

[aptech77]

FYI, avgas is illegal to run in street/water vehicles. Do get caught.

[jmuthaf]

on my stock 77 k6 750, i ocasionally run 1 gallon of 110 leaded fuel with 3 gallons of 93. On regular 92-94 pump gas this bike will ping under a good load. With this fuel mixture equaling about 96.5 octane the bike runs flawless! it idles smoother and is more responsive. Though the bike only calls for 92 pump gas, this runs alot better!

[Gordon]

on my stock 77 k6 750, i ocasionally run 1 gallon of 110 leaded fuel with 3 gallons of 93. On regular 92-94 pump gas this bike will ping under a good load. With this fuel mixture equaling about 96.5 octane the bike runs flawless! it idles smoother and is more responsive. Though the bike only calls for 92 pump gas, this runs alot better!

Your bike does not call for 92 pump gas, at least not in the octane rating method used today.  What was 91 or 92 when these bikes were made is now 87.  Same resistance to detonation, different number.  If your engine pings when running 92 octane then something is off.  Possibly a timing issue or excessive carbon build-up in the combustion chamber. 

[bucky katt]

my k4 doesnt run right on the 92/93 octane here. she runs best on the 87, and i put 89 in during the hottsest months.

[MoTo-BunnY]

on my stock 77 k6 750, i ocasionally run 1 gallon of 110 leaded fuel with 3 gallons of 93. On regular 92-94 pump gas this bike will ping under a good load. With this fuel mixture equaling about 96.5 octane the bike runs flawless! it idles smoother and is more responsive. Though the bike only calls for 92 pump gas, this runs alot better!

Your bike does not call for 92 pump gas, at least not in the octane rating method used today.  What was 91 or 92 when these bikes were made is now 87.  Same resistance to detonation, different number.  If your engine pings when running 92 octane then something is off.  Possibly a timing issue or excessive carbon build-up in the combustion chamber. 

+1 These same myths about needing high octane gas* abound in the air-cooled VW crowd - different octane system used back then RON, while now it is AKI
*(in an otherwise stock, properly tuned engine)

http://en.wikipedia.org/wiki/Octane_rating#Difference_between_RON_and_AKI

[Don R]

Some of you may have noticed that today's pump gas does not store very well. Real race gas will store longer. There is a bike shop nearby that will only put race gas in the bikes in the shop.