Fuel octane vs concistancy
 

I have made the jump from Super Stock to .90 and t/s class racing. I have always been limited to 112 octane for the combos i ran, but now with the new car and engine combo i am ready to freshen the engine and am wondering if i can expect more consistancy with the higher octane levels. the engine is currently @ 14:1 and requires C16 or an equivelant. I will look at options between dropping compression to run VP98 through to 16:1 compression.

Your thoughts are appreciated.

Ian

Re: Fuel octane vs concistancy
 

Once was told that the Q-16? (the oxygenated one) would make the car as consistent as a dragster on alky, would have to change to bigger jets obviously, He ran on Sunoco 16 and would switch to that VP stuff at big $ bracket races. I am just telling you what I was told, I never got around to trying it. Mine was pretty good on just Sunoco 116.

Re: Fuel octane vs concistancy
 

I run a Super Rod car on alcohol and it is Deadly using a Number 1 stop and a Rupert carb!
Been running alcohol since 1996,and would never go back to gas.!!!!!!!

Re: Fuel octane vs concistancy
 

14.1 compression hardly requires C-16 fuel .
My Big Block combination has 15.9 to1 and runs perfectly on C-14 or, for the last 2 seasons on Sunoco Maximal Red.
At 14 to1 , depending on the cam and ignition timing Sunoco Blue or VP C-12 should be more than adaquate for a throttle stop application.
While oxygenated fuels such as Q 13 or Q16 have some benefits, there are many drawbacks to it , personal safety being my biggest concern . ....MTBE is nasty stuff, and the fuel requires more attention as far as storage in the fuel system.
In the big picture , fuel cost $ per gallon from one grade or brand to the other is minimal.
Run the higher compression, the car will be more consistant when heat and humidity go up than a low compression setup.

Re: Fuel octane vs concistancy
 

For a standard race fuel look for VP X16, NOT C16. Vaporization properties are better for a NA engine, and the price is better. VP113 is another option that is reasonably priced, lightly oxygenated but most engines just need around a couple sizes larger jets.

Re: Fuel octane vs concistancy
 

Consistency has a lot more to do with the brand of race fuel and the blend than with the octane level. Once your engine has the octane it needs, adding octane won't make any difference.

Re: Fuel octane vs concistancy
 

Consistency has a lot more to do with the Lean/rich of the tune than the octane.
Get her to lean and the air goes up a couple of numbers she falls off. Get it too rich and the air goes down and she slows up because she is way too rich. There is a sweat spot in the tune. It is usually a "Window" and that is what you need to find at your track, the conditions you run in. The oxygenated fuels seem to have a little larger "Window".

Re: Fuel octane vs concistancy
 

I prefer the VP Q-16 myself.

Re: Fuel octane vs concistancy
 

I ran my 565 on Renegade 116 and then VP X-16. Engine has just under 15 to 1 compression.

It ran very well on both and was generally very predictable.

Tried Q-15 for a few races this year. Just jetted up 3 numbers. Q-15 is a 50-50 mix of Q-16 and C-15 I'm told.

Results were more power but consistency due to dips in throttle stop rpm intermittently gave me fits...

I have fought this t-stop issue for what seems like forever......and it occurs with an inline stop or a disc plate stop....

Switched back to Sunoco Maximal for my last 2 runs this past weekend and both runs were normal without t-stop rpm drops and this was using the disc stop.

I did not like handling the Q fuel or the smell.....and from what I see and know.....you really need to have a carb done and tuned on the dyno for the fuel your using. The Oxygenated fuel was not for me....

Re: Fuel octane vs concistancy
 

Rich said " ..and from what I see and know.....you really need to have a carb done and tuned on the dyno for the fuel your using. "
I totally agree. You can zero in on the lean rich "window" & nail down the changes in power that occur when the "Air Changes". It helps your combination with consistency and predictability.