gasoline prefrence

[WADS56]

Torco 112 in the 79
shell 87 in the 93lx

[PKRWUD]

Originally posted by Chevyguy
When I was towing my big block back from Mi with my mustang, I ran into pinging problems when I hit the uphill grades on the NY thruway. The Gas that I had filled with was 87 octane with 10% ethanol. Even though alcohol has more octane, it also has less btu/gal and burns at a lower air/fuel ratio. something like 6:1 vs 14:1 for gas, this is why alky carbs have giant jets. So.. adding 10% alcohol to gas is like watering it down, and can cause some leaning out. I had to fill up with some 94 Octane before I got to Mass since there is a high elevation pass.

Running more Ignition lead will feel like more compression since it builds cyl pressure. But.. it is different, the fuel is still burning longer, and more compression does probably give more power than low compression and more timing.

Our Sprint car small block has 14:1 pistons, just under a .700" lift cam (I'm not allowed to share the exact specs ), is N/A, and has the magneto set to 32 degrees of advance. It runs on straight methanol. We would not be able to run it on 110 octane. Since methanol supports so much more compression, why wouldn't gasoline with 10% methanol be good for street performance? If it was 87 octane before the methanol, what would adding 10% methanol change the octane to?

Take care,
-Chris

[curtis73]

It would work if the carb or EFI were re-calibrated. Carbs are set to deliver a set ratio of liquid to air, assuming that the liquid is gasoline and the air contains 21% oxygen at STP (standard temperature and pressure) When you add 10% alcohol to gasoline you basically only have 95% of the weight you had before. The carb will still deliver the same amount of liquid and you will have a lean burn.

EFI will try to keep the mix at 14.7:1 assuming your are burning gasoline. Since methanol's stoichiometric ratio is somewhere in the 6s-to-one, it will also run lean.

My guess is that your carb on your meth racer is jetted for about 6.4:1.

Methanol doesn't have a higher octane rating. If you were to test it using r+m/2 like the gas companies use it would probably come in at around 60-65. It supports more compression because of its other combustion qualities: latent BTUs, combustion speed, and its lack of exothermic heat. Alcohol burns slow, cool, and it takes a lot more of it to get the BTUs that gasoline has. Adding methanol to gasoline effectively reduces its BTUs, Doesn't really impact Octane rating (if so, one point at most because there isn't that much in it) but causes your engine to run lean.

Using Methanol in gasoline is a cheap way to help emissions as it adds oxygen which does something else... Reduces NOX?

My opinion? It sucks for the street, hurts MPGs, washes down the cylinder walls, and I'm tired of Big Brother telling me that I (even though I have the only internal combustion engine for 3 miles) I have to run pathetic and potentially damaging fuel in my babies. To me, that's like passing a law that says baby food isn't allowed to contain vitamins, minerals, or anything healthy. They are making laws that adversely affect our personal property.

*stepping off soap box*

Curtis

[PKRWUD]

Okay. I see what you're saying. BTW, I completely agree, and avoid ARCO like the plague because of their methanol additive, but suddenly started to wonder if methanol couldn't actually help, provided the engine was prepared for it. Just so that I'm clear, I wasn't going for an arguement at all. I like throwing out ideas sometimes and learn from the intelligent ones who reply. Thanks!

Take care,
-Chris

BTW: It's not carbed

[Mr 5 0]

catcher:

Quote:

so mr 5.0 running 94 with an advance in your opinion is better than running stock with 87 is that the general consensous


Absolutely. Been proven tens of thousands of times in street-driven Mustangs. Advancing the timing is a standard little engine 'modification' that's been around forever because it generally delivers good results if done correctly.

Using higher octane gas to compensate for possible detonation after advancing the initial timing is somewhat of a necessity. How high? You may well get by with 89 octane, or 92 or 93. Depends on a number of variables.

I just use Sunoco 94 out of personal preference based on good experience over time. I recommend it (with advanced timing) but it's certainly not mandatory. As I said, 92 or even lower octane might be fine.

For my engine's sake, I just don't care to experiment to see how low an octane I can get by with and not have a problem. As I said, this approach has always worked for me in my 5.0 and many other vehicles I've owned.

Of course, on a stock engine with factory advance (liike my wife's Mazda), I use good old 87 octane but I always buy name brands from a trusted station in my area.

[curtis73]

PKRWUD.... I'm drooling! I love Hilborns. I always wanted to take a hilborn setup, convert to EFI, add plenums on top of each bank, and run twin turbos, one plumbed into each plenum, equalized by a 1" tube between plenums. This should maintain killer throttle response, have some amazing high end HP and nice street appeal

[PKRWUD]

Originally posted by Mr 5 0
For my engine's sake, I just don't care to experiment to see how low an octane I can get by with and not have a problem. As I said, this approach has always worked for me in my 5.0 and many other vehicles I've owned.

That right there is the number one secret to having a long life, healthy engine. Make up your mind, and stick to it. Screw what somebody else does. Folks who change their habits and preferences about as often as they change their sheets end up with a junk vehicle.

IMHO.

Take care,
-Chris

[7000rpmisheaven]

There is another good reason for doing it the way Mr. 5.0 does it. Having any detonation is bad. But minor or slight detonation may not be clearly audible.

[Chevyguy]

I did forget to make one point about Ethanol or Methanol as a fuel. As you may know engines running on pure alky will make more power than a gas motor, hence Gas, Alky, and Top fuel nitromethane classes. The trick there is the motor is set up for the differences.

Ford has made some duel fuel and FFV vehicles which can run on Methanol blends. There is a refractometer in the fuel line which calculates the alcohol content and adjusts the fuel injection parameters to compensate.

I remember Ford made a special supercharged Cobra that ran on M-85 or Gas. This was a showcase for the FFV program, The car had two sets of injectors, and I belive an adjustable boost pressure gate. When the 85% methanol blend was used both sets of injectors were used and the car produced the most horses, as the gas level rose, the second bank of injectors were shut off and the boost was lowered.

My point was adding oxygenated additives to fuel is a political decision and does not make real good sense.

Some food for thought!

[chatcher]

well i have always run 94 sunoco in my car and thanks to this post i feel good about my choice to do so im also happy to see all the great info being thrown out in this post ive learned alot
as soon as my car is back on the road ill adjust the timing to take better advantage of my gasoline prefrence but thats another post