Fuel Recommendations for 14:1 or more compression

ralph85 · Post by **ralph85** » Fri Nov 30, 2007 6:03 pm

This is an alum headed, 6 inch rod, SBC 434 w/ a relatively small cam (260/270 @ .050). Assuming gas, what octane?

Thanks.

David Redszus · Post by **David Redszus** » Fri Nov 30, 2007 7:00 pm

You will need the minimum octane that will prevent detonation.

Then you have to find which fuel runs best in your engine. Fuels with similar octane values do not run the same or make the same power.

Speedster400 · Post by **Speedster400** » Fri Nov 30, 2007 7:42 pm

C14 would work nicely with that specific camshaft.

David Redszus · Post by **David Redszus** » Fri Nov 30, 2007 11:20 pm

C14 does not have a good RVP, does not have light front ends, has too many tails.

A much better choice (if you had to use VP fuels) would be C25.
Better everything.

Really serious racers will have special fuels custom blended to their needs.

383Malibu · Post by **383Malibu** » Sat Dec 01, 2007 9:33 am

Either DRT or Q16, both oxygenated fuels from VP, would make more power than C14 or C25.

David Redszus · Post by **David Redszus** » Sat Dec 01, 2007 10:43 am

383Malibu wrote:Either DRT or Q16, both oxygenated fuels from VP, would make more power than C14 or C25.

When we compare the BTUs of heat energy per pound of air burned, we find that all fuels produce the same energy (excepting nitro additives). Yet the performance results in a specific engine cannot be predicted. Even in engines of similar design.

Remember that oxygen is not a fuel. Oxygenated fuels have less energy than non-oxygenated.

SWR · Post by **SWR** » Sat Dec 01, 2007 10:51 am

David Redszus wrote:
383Malibu wrote:Either DRT or Q16, both oxygenated fuels from VP, would make more power than C14 or C25.
When we compare the BTUs of heat energy per pound of air burned, we find that all fuels produce the same energy (excepting nitro additives). Yet the performance results in a specific engine cannot be predicted. Even in engines of similar design.

Remember that oxygen is not a fuel. Oxygenated fuels have less energy than non-oxygenated.

Remember then that with oxygenated fuels you can stuff more of it in there,and still have oxygen to burn it...

David Redszus · Post by **David Redszus** » Sat Dec 01, 2007 11:14 am

SWR wrote:
David Redszus wrote: Remember that oxygen is not a fuel. Oxygenated fuels have less energy than non-oxygenated.
Remember then that with oxygenated fuels you can stuff more of it in there,and still have oxygen to burn it...

Yes that is sometimes true depending on the amount of oxygen in the fuel. For oxygenated race fuels, they are usually limited to about 3% oxygen. If we run a fuel/air ratio of 8%, the actual amount of ingested oxygen from the fuel is 0.24%. Thats only a quarter of one percent which is much less than inlet air cycle to cycle variations.

The observed performance benefits of oxygenate fuels is a result of other combustion factors, not the amount of oxygen in fuel.

Alcohols are another story. They tend to provide a substantial increase in charge density resulting from inlet air cooling. But that only works if the fuel is substantially evaporated.

383Malibu · Post by **383Malibu** » Sat Dec 01, 2007 1:08 pm

David - I'm not trying to be argumentative, but regardless of the technical jargon, I am aware of recent tests on the dyno and on the track that have shown properly tuned N/A combinations to make more power with DRT and Q16 then with C25.

David Redszus · Post by **David Redszus** » Sat Dec 01, 2007 6:44 pm

383Malibu wrote:David - I'm not trying to be argumentative, but regardless of the technical jargon, I am aware of recent tests on the dyno and on the track that have shown properly tuned N/A combinations to make more power with DRT and Q16 then with C25.

That could well be possible for a specific engine, since each engine tunes somewhat differently. Even on what appear to be sister engines.

Common practice among engine builders is to tune mixture and timing for a certain fuel and then simply substitute other fuels for comparison. This is never valid since the engine must be retuned for each fuel tested.

It could also be a function of the condition and quality of the fuel being used. VP has been notorious for their inconsistency.

One factor to consider is that DRT is not a legal fuel for many applications due to its high dieletric value and its failure to pass the Germane Reagent A test.

I am not familiar with Q-16 and do not have any specifications on that fuel. If you have detailed technical specifications on Q-16, I would be happpy to review them and offer an opinion. Race fuel is what I do for a living.

RayJE Carburetors · Post by **RayJE Carburetors** » Sat Dec 01, 2007 6:57 pm

VP SVO5 will make more power on that engine ....from dyno experience... in OZ its SVO5 .. im not sure what its labled as in the US.
its cheaper than C25 and C14 out here..... couple of weeks ago we were dynoing a ex pro stock truck 358 splayed valve engine, SVO5 made 15HP more than C25 and 8 HP less than ROO25 ( i think in the US it was labled Outlaw Pro Stock).

On 13-14:1 comp engines it is the fuel we like to run....

Ed-vancedEngines · Post by **Ed-vancedEngines** » Sat Dec 01, 2007 7:06 pm

You will need the minimum octane that will prevent detonation.

Then you have to find which fuel runs best in your engine. Fuels with similar octane values do not run the same or make the same power.

Best answer.

You never need more octane fuel than the engine needs to prevent auto-ignition.

The fuel recommendations here are surprising me. 14.00 -1 statc comkpression is nothing unless it is street driven. That would be tough.

I would think that any 110 to 112 octane would more then plenty. Actually a 106 or 108 would be if it is available.

Ed

383Malibu · Post by **383Malibu** » Sat Dec 01, 2007 10:00 pm

383Malibu · Post by **383Malibu** » Sat Dec 01, 2007 10:02 pm

David Redszus wrote:...It could also be a function of the condition and quality of the fuel being used. VP has been notorious for their inconsistency...

In light of this statement, what fuel do you favor?

Ed-vancedEngines · Post by **Ed-vancedEngines** » Sun Dec 02, 2007 12:26 am

I have used Sunoco Blue 112 with up to 15.00 -1 on Dyno Pulls, and there is no problems.

Speaking of VP. On thier webpage they do give lots of recommendations of which fuel to use and when.

I just think it is redundant a waste of money and a loss of power when anyone is using a stronger octance fuel than they need for their combination and use.

Additional fuel octane is not additional power ingredients. It is the opposite.

Ed