12.5 :1 compresion CP 495cc

[Kuma]

What do you think,
new Timbo 495 motor, 12.5 compresion CP piston, should I run it on 91 pump gas or 100 LL Av Gas?
Running in the dunes, I've got a CR500 that detonates on pump gas under the type of loads it sees in the sand, put it on Av Gas and it runs great!
would there be any advantage in running AvGas in the 'dale or should I be good with the pump gas?
Race Gas is out of the question so don't even go there, that is why I opted for the lower compresion piston.

[cdsracer]

Has this engine been dyno tuned?

[desertbound]

QUOTE (Kuma @ Oct 23 2008, 11:21 AM) <{POST_SNAPBACK}>

What do you think,
new Timbo 495 motor, 12.5 compresion CP piston, should I run it on 91 pump gas or 100 LL Av Gas?
Running in the dunes, I've got a CR500 that detonates on pump gas under the type of loads it sees in the sand, put it on Av Gas and it runs great!
would there be any advantage in running AvGas in the 'dale or should I be good with the pump gas?
Race Gas is out of the question so don't even go there, that is why I opted for the lower compresion piston.

I ran 91 pump gas on a 12.5-1 compression machine all day long. I personally don't like Av Gas. On a molecular level it is made to be ran at altitude. In theory it could cause problems at sea level. I know people run it all the time, but it has just never sat right with me.

If you are not comfortable running pump gas, Torco makes an octane booster that will boost pump gas up to 110 octane. It comes in five gallon cans and will treat 50 gallons at 110 ocatane and 80 gallons at 100 octane. A lot of actual pro street nhra guys use it. It's $50 for the 5 gallons, but it comes out way cheaper than race gas. And it doesn't leave deposits in the motor or fuel tank like other octane boosters.

Or you could always find a place that has VP street blaze. It's 100 octane and I can find it out of the pump at a few stations around here.

[Kuma]

QUOTE (desertbound @ Oct 23 2008, 11:47 AM) <{POST_SNAPBACK}>

I ran 91 pump gas on a 12.5-1 compression machine all day long. I personally don't like Av Gas. On a molecular level it is made to be ran at altitude. In theory it could cause problems at sea level. I know people run it all the time, but it has just never sat right with me.

If you are not comfortable running pump gas, Torco makes an octane booster that will boost pump gas up to 110 octane. It comes in five gallon cans and will treat 50 gallons at 110 ocatane and 80 gallons at 100 octane. A lot of actual pro street nhra guys use it. It's $50 for the 5 gallons, but it comes out way cheaper than race gas. And it doesn't leave deposits in the motor or fuel tank like other octane boosters.

Or you could always find a place that has VP street blaze. It's 100 octane and I can find it out of the pump at a few stations around here.

I'm one of those guys that has run Av gas for years with no problems, I had it checked for octane by a freind that tests gas for Shell, it tested at 106, this was quite a few years ago, and the octane comes from lead like the old days.
I like the smell too, I prefer the smell of race gas but Av gas generally runs about 50 cents more than pump gas, sometimes it's the same?

Has not been dyno tuned, but it has Timbos Map for this Motor, I'd like to get it tweeked in but the time frame is not there for this trip. I don't plan to thrash on it too much and will be watching the status lights for over heating.
Ran it on the street for a while doing ring break-in, seemed to run good. that was with pump gas, but other than a dyno, I don't think that there is any way to load it like paddle tires pulling a steep slip face.

[cannondale27]

It depends what elevation your running at.I could never get away with pump gas around here.

[Kuma]

QUOTE (cannondale27 @ Oct 23 2008, 03:20 PM) <{POST_SNAPBACK}>

It depends what elevation your running at.I could never get away with pump gas around here.

Were talking Glamis!
300 to 900 ft

[cannondale27]

I would not run pump gas there.Looking for trouble.I am at 650ft.

[MX Quad Dad]

QUOTE (desertbound @ Oct 23 2008, 02:47 PM) <{POST_SNAPBACK}>

On a molecular level it is made to be ran at altitude. In theory it could cause problems at sea level. I know people run it all the time, but it has just never sat right with me.

I brought this theory up to a fuel rep at a airport I was doing some repairs at, and he had a quick reply that an airplane needs and uses the most horsepower at take-off.

[cannondale27]

AV gas is fine.More power to be had out of real race gas but AV wont hurt anything like pumpgas will.

[Kuma]

I'm back from the dunes, I did a blend of 50/50, should have brought the pump gas up to around 96 - 98, ran fine with no indication of detonation or pinging.