This weekend I plan to add about 4 gallons of unleaded 100-octane racing fuel to about 8 gallons of 91-octane fuel already in my tank. Will all this gas mix properly together or is there some type of separation in my gas tank that will prevent all of it from mixing. I ask this question because from some pictures I have seen, the gas tank seems to be separated into two sections on the driver’s side and passenger’s side. I hope my question makes sense.

Thanks,

Clayton from Las Vegas

 

You'll be fine, do a couple of figure 8's and it'll mix great, but skip the octane boosters at the stores!

 

Thanks Nuts,

That is what I was thinking about doing. I guess I’m a little “NUTS” too.

Clayton from Las Vegas

 

I agree with "NUTS'S" assessment, Clayton. Regarding adding the 100 oct stuff, just be sure it's unleaded and resist the temptation of 'adding more', thinking that more is better.

Too high of an octane and your computer will see it and make the necessary 'adjustments' which will end up costing you horsepower.

And in spite of all those who insist that octane boosters worked for them, over the years I have never found one that does much of anything except make my wallet lighter.

Good luck at the track and let us know the results.

 

Check this out:

http://forums.corvetteforum.com/show....php?t=1412465

 

Put the 100 in first then add the 91...

VR

 

Clayton i recently started using Torco. Before my twin turbo install i would have occasional pinging at WOT during the summer months. This will be my fifth tankful using Torco with no issues. All i need is one bad tank of gas and boooom Joel is the forum distributor for Torco. Any questions feel free to ask him. Great guy http://www.jbsblownc5.net/

 

Can you explain that in more detail?

 

I don't know the "details" of what goes on inside the "brain" of that computer, but I have first hand experience that running a significantly higher octane fuel than what the car is tuned for will result in lower output.

This doesn't seem to be a problem on a carbureted engine as much as it is on a computer-controlled fuel-injected one. My 440 powered drag Fury loves the extra octane, while my heavily modded C4 (now history) as well as my current C5 suffered from using straight 100 octane unleaded fuel...and not the "corn-based" version of it either, but straight honest to goodness gasoline.

Maybe someone with more smarts than me on the subject can offer a better technical explanation for what happens to cause that drop off in power.

 

Why do you need over 92 octane?
Just a question.....are you TT or blown or running more timing?
More octane is the ability of the fuel to resist spontaneously combusting during compression, before the plug fires. The higher the compression due to either forced induction or engine designed compression ratio, will raise the temp of the air/fuel charge untill it ignites by itself. The more octane, the higher compression you can go before it pre-ignites. That is pretty much all the octane rating is for. Its resistance to preigintion. Anything higher than your engine / driving habits/ loads require, is a waste of octane/money.
Why does it seem that your fuel economy or power is less with 100+ octane?
Maybe because you are WOT more of the time because you expect more power for the money spent. Not to mention most vehicles at 94 octane will never preignite, so they are already making max HP.
The computer wont adjust for too much octane, only not enough octane because it will ping/knock and the knock sensor will reduce timing which lowers cylinder pressure and temps. Lower timing means less torque and power and less gas mileage.

 

I am trying the higher-octane fuel to see if it stops the pinging at WOT. Here in Vegas it is 100+ and it is a common problem here. Other then the 100-octane racing fuel, all we have is 91 at best. I’m not sure if it is the timing or carbon buildup. I will be having the carbon removed in a month or two when I have my supercharger installed. I plan to have it tuned for 91-octane, but it will probably need a little help. I am still going back and forth between adding a little racing fuel and using Torco after the S/C. So this is just a test to see what changes it makes. A mechanic friend of mine drove my car and said the knock sensors are definitely backing off the timing. I will post the results after tomorrow.

Thanks,

Clayton from Las Vegas

 

Remember: the higher the octane, the SLOWER the burn rate, so in many instances, especially in hot cammed cars like my 65' L76, the entire mixture will not complete ignition before the exhaust valve is opened and forces unburned fuel out the exhaust.

I ran 105 Octane in my car and it absolutely HATED it....

Basic rule of thumb is use the lowest octane you can without engine pinging.....

Higher octane does NOT mean more horsepower....

 

this comes up all the time in the ducati forums and what he just said is right. i have to run as close to 100 as i can with my high comp. 383 in my 75 to get it to run right, if i dont it pings like crazy. My c-5 runs just fine on 93 or 92. i ran 87 in my 72 and could not tell the difference between it and 93. high octaine burns slower, lower octaine burns faster. run what burns completly in your car with no ping.

 

The 100 octane unleaded fuel will mix linearly with your 91 octane. The LS1 doesn't seem to benefit from anything greater than 93 octane. I mix it in the hottest months for the same reason.

Add just a smidge over 3 gallons of 100-octane per 10 gallons of 91-octane and you'll arrive at 93 octane average.

 

Seems to me it would be cheaper to just use Torco

 

I used to have to mix 5 gallons of 100 octane in with 91 gas to get me where I needed to be. It was expensive, and a pain in the butt to drag 5 gallons around when I would not be near a 100 octane station.

About 4 years ago, I got turned onto Torco. Now I carry around a Quart instead of 5 gallons...

Never looked back!!!

JB

http://www.corvettekillstories.com/p...Torcopromo.wmv

 

Run the lowest octane you can. Too high will only lose HP if you don't need it. You can re-time the ignition for more advance to compensate for the slower burn rate, but if you are already making your peak cylinder pressure at the correct ATDC sweet spot, then you won't be gaining anything.
I would suggest using Meth injection over Octane Boost! It helps reduce carbon build-up, and cools down the IAT.

 

How does water injection compare to meth injection? The former sounds more desireable, as you can find water anywhere - I wouldn't know where to begin to even look for methanol around here.

 

First, the computer only “sees” engine knock, it is oblivious to the octane of the gasoline in every other respect. No knock and it changes nothing.

Yes, higher octane gas has a slower burn rate than lower octane gasoline and using a higher octane than is needed will result in the combustion process taking longer and possibly making less power because the crankshaft will be at a different point in it’s rotation. Even then, the difference is small enough to be hidden or compensated for by other variables.

It is important to remember what engine knock is. It is the combustion process brought to a hasty end by a spontaneous explosion rather than a controlled burn. Engine knock occurs when the pressure and temperature in the cylinder are high enough when combustion is occurring that the remaining unburned fuel mixture spontaneously ignites. Therefore the key to preventing knock is to keep the pressure and temperature below the threshold that causes knock to occur.

Higher compression ratios raise the pressure and make knock more likely to occur. The maximum pressure and temperature occur some time after the spark occurs. If the spark is delayed so that the point of maximum pressure is after TDC then the downward motion of the piston will somewhat counteract the pressure rise from combustion causing the maximum pressure to be lower, which explains why retarding the spark reduces the possibility that knock will occur.

Hot spots in the combustion chamber and using a spark plug that has a heat range that is too high can have the same effect as increasing spark advance and increase the possibility of knock that is called pre-ignition. Combustion chamber design can either enhance or reduce the ability of the engine to reduce knock.

There are three ways to increase the octane rating of gasoline. The use of gasoline molecules with an inherently higher rating will work. Blending in an inherently higher octane fuel, such as toluene, works too. Another way is to blend in a compound that is not a fuel in itself but serves to raise the octane rating of the fuel. In the past, tetraethyl lead was commonly used but today other less effective but safer compounds are used. Torco is one of the most effective compounds that are used today.

Water or methanol injection work to lower the temperature of the mixture, increasing its resistance to knock. Water is less effective but it is often blended with alcohol to increase its effectiveness. GM did this in the early ‘60s with the Olds F85 Cutlass that used a turbocharger with a high compression aluminum V8.

 

.... and convenient......carry a can in your car and not have to search for stations with 100 octane


DH