story by per schroeder • photos by perry bennett
There are a lot of myths surrounding the various types of gasoline we use in our street and race cars. Which one will help us get the most power? Which one is the best bang for the buck? Do we really need race gas? If so, which type? There’s precio…
Very interesting
So, basically, if you don't have high compression or forced induction, you don't get much from race gas. Hard not to be snide at this point..
I was interested to see the methanol and e85 results, at least. I guess the whole thing is more relevant to people who have a really hard time gaining 4 hp due to class rules. The only thing limiting the power of everything i own is my own laziness, pretty much.
What i'm curious to know is whether i'm going to gain power going from race gas to e85 on a turbo minivan that's maxed out the airflow of the turbo. Hopefully time will tell.
Pretty much what I'd expect. More octane only helps if you're knock limited and having to pull timing on the lower octane fuel. And oxygenated fuels need to be fed in larger quantity, but make more power (hence E10, E85 and methanol making more power).
In a race if you're running E85 of M1 aren't you going to have to carry twice as much weight? At what point is that worth it over a 20-40 minute spec miata sprint race? Carrying 10 gallons vs 20 gallons seems like it can really add up.
Methanol in particular is a real pain to use. The dirt track racer were using it but they all went back to gas.
What's missing from the article is a good explanation of why you see the power increase with alcohol. Yes, it increases octane and available timing, but the article states at the beginning that even on the 87 octane cheap gas the engine was still able to reach MBT without inducing knock.
As I understand it, the win comes because you get more energy burning hydrogen atoms than you do from burning carbons. Since otto-cycle engines are ultimately limited in power by how much atmospheric oxygen they can intake, the fuel with the highest H/C ratio will give the most power. Methanol gives you 4:1, ethanol 3:1, and gasoline something around 2.5:1 (it's a blend of a bunch of stuff). Pure hydrogen would be even better, but it's got some challenges in adapting the fuel system. :)
The oxygenation in the alcohols is a red herring, while it increases the number of oxygen atoms in the combustion chamber that doesn't net you any more power because the oxygen came in already 'burnt' (that is, already bonded to a C on one end and an H on the other). You had to put in much as much energy to break those bonds and free the oxygen as you get out of reforming them, so it's a zero factor.
Man, when I saw it was an article by Per I thought he was back on staff and did a little "Whoop". Not to dis the current staff 'cause I love the magazines, but I miss Per's work being there to enhance the mags that extra bit.
In race cars, one advantage of alcohol is that it tends to run cooler and the anti-knock quality allows higher compression or boost.
An engine needs to be built to run alcohol.
In reply to codrus:
Thanks for explaining that indepth and all sciency but not too egg head so i could still understand!
Interesting story... Thank you for writing it. And maybe I even learned something...
I read this story in December when it was published and was very impressed with the test. However, after reading it a second time I think there is a major failure in this report, not the stats. The test should clearly indicate that the results are only applicable when the vehicle can be tuned for each fuel. So if you are applying this to your street car or any other vehicle for which the mixture, timing, fuel pressure, etc. cannot be individually adjusted, the results are mostly not applicable. The perfect example is the first 2 fuels tested the 93 and 87 octane E10. If your car comes from the factory tuned for 91 or 93 and then you run 87 (regular) your vehicle MAY compensate for it and not knock but that likely means it will cut the timing and some power. Now if any of my M cars which call for 91 WOULD only loose 1 per 100 horsepower and the fuel cost 10-15% less in todays market, I'd be running the 87 all the time. But in most cars not quite as sophisticated or highly tuned as my M's but calling for 91 may not adjust easily to 87 and run poorly or loose more power. That's why the most important part of this story is not necessarily the actual power differences BUT that if you have the ability to adjust all the engine setting, some fuels will produce varying horsepower, torque and consumption. I think that this is mostly missed by the way the "results" are presented. Looking at the results why would anybody ever buy premium fuel if it only cost them less than 1% in power but saved them 10-15% in price. The reason why they don't is that most of us drive our cars everywhere and the results can be much graver that a 1% horsepower loss. So if you have a race car who's fuel system is fully tunable, this report is very helpful. If you don't have a race car like that or are thinking that this applies to your daily driver then the article has clearly confused your understanding of the test.
^Because that's that specific car. A Miata with relatively low compression compared to today's vehicles.
I can promise my BRZ which runs 12.5:1 compression stock, will lose more than 1% on 87 from the computer pulling timing.
I once had a Chrysler that was designed to run on high test (93 today) ,I found that I could run it on regular (87) as long as I kept a light foot. Too much throttle and I would get the marbles in a can rattle It was just an experiment.
Pulling timing to run on lower octane fuel has an MPG penalty on top of the power penalty. So in the end, it may or may not even be cheaper.
The only reason any cars are sold at all that can run on 87 is consumer perception. Very few modern engines can't benefit from 89 or 91 with proper tuning. Consumers think that paying a few cents more for 93 is ridiculous and means the car is more expensive to feed, even if it gets better mpg.
I really wished there had been a test of a fuel additive like Torco. I understand this engine didn't "need" more that 93 octane. While I need just a tad more than 93 offers I cannot get and don't want to carry round large quantities of E85. My solution is adding 12 ounces of Torco to five gallons of premium pump gas. I wonder how many others do something similar and how it squares with pricey 100 octane racing fuel? This test doesn't help much (it seems) for us with turbos that are cranked up.
In reply to Scargod:
I agree. I run a supercharger on my Miata. Like you, since I put a lot of street miles on my car it isn't real practical for me to run super fuel.
GRASSROOTS & CLASSIC: Please do a follow up test with 93 and additives!
pretty much what I expected to happen.. except for the 93octane non-e. I did not expect that to perform like the 87 octane stuff.
I got into a few internet Arguments about using 93 octane on the street. While I had no numbers to back up HP and torque, I had solid, above EPA estimates, MPG numbers to to show that 93 octane gave my stock, 1999 Hyundai Tiburon a good 3 to 4 empeegees above the 87. That alone told me that the higher octane stuff was making more power by keeping the computer from pulling the timing
Nice to see a scientific study show that moonshiners weren't crazy in running white lightning in their car's tank as well as their own.
In all of my Honda cars , 87 octane wasted money and 91 was too expensive for the return, so normally 89 did the trick. And a 3 to 1 mix of 89 to 91 was the best for power and economy all round. You could feel the difference. Just my 2 cents.
In reply to the staff of Motorsport Marketing: Here's one reason why I buy your magazine at the newsstand.. I too like Alcohol fuels but you should have mentioned how toxic Methanol is compared to Ethanol. While it is the cheapest per gallon fuel the nearly double requirement raises it's cost up there.. Yes it does make more power than ethanol but the ease and low price of E85 more than offsets it's power and lower cost.. I treat my E 85 to a 5% upgrade with race gas. It increases the octane by a significant amount while adding nominally to cost. Pure Ethanol is 114 octane. Imagine how low octane the gas blended with ethanol is to drop it to pump numbers!!!!!! A little 114 Octane seems to make a real difference..
I'd love to see you do a test of that same engine Turbo/supercharged, where the real advantage of alcohol would come out..
bmwpc wrote: ...The test should clearly indicate that the results are only applicable when the vehicle can be tuned for each fuel. So if you are applying this to your street car or any other vehicle for which the mixture, timing, fuel pressure, etc. cannot be individually adjusted, the results are mostly not applicable.
I rather agree with you. The article almost wasn't on fuel, but more on engine tuning for a particular fuel.
Kinda thought the article made much ado about essentially nothing with regards to the tiny differences in base gasoline fuels. Especially in light of the substantial difference methanol gave.
Interesting article and results too. I think the usefulness of the test is limited to pointing out that you need to do your own testing on your own car to see what works with your particular setup. The fact that the advantages of the alky couldn't really be taken advantage of because of the relatively low compression of the engine should have been mentioned in the article. For example, try a high alky fuel in something like a brz and watch that thing wake up! I wonder if people who have tuned their brz for E85 still feel like the car is underpowered? Just wondering. It would be nice to be able to run E85 for track events and go back to pump gas for street driving for dual purpose vehicles. Course in my area, I have to drive 140 miles to get E85 so its a moot point for me.
Several questions have occurred to me since that article came out.
First what base was the gasoline in the E85? 50 octane? 87 octane? 91 octane? 105 octane?
Second. How much boost/ power will that Miata tolerate with gas, race gas, E85? And methanol.
Third. Heat range of spark plugs? Will a cooler heat range produce more or less power using gas race gas E85 and methanol.
frenchyd said:Several questions have occurred to me since that article came out.
First what base was the gasoline in the E85? 50 octane? 87 octane? 91 octane? 105 octane?
Second. How much boost/ power will that Miata tolerate with gas, race gas, E85? And methanol.
Third. Heat range of spark plugs? Will a cooler heat range produce more or less power using gas race gas E85 and methanol.
I can't answer the first two questions but I can answer the second part of the third.
The heat range of a spark plug is a number representing the plugs ability to dissipate heat. The plug (and everything else in the combustion chamber) heats up during the power stroke and needs to cool off enough before the intake stroke (or injection cycle in the case of a DI engine) that it won't ignite the incoming air/fuel charge on contact (an uncontrolled combustion event referred to as pre-ignition). If it cools off too much deposits will build up on it leading to early plug failure. Unless you're experiencing pre-ignition then heat range will have no effect on engine power or any other aspect of engine performance.
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