If you're willing to do a little carburetor tuning, E85 could be a budget high-octane fuel
Environmentalists and car crafters make strange, if not odd-opposite, bedfellows. The greenies are all over this not-so-new, environmentally friendly, renewable resource ethanol fuel that even has GM pushing it in its television ads. So what's all the fuss about and why should it interest you? Forget about greenhouse gases and that whole Al Gore political football. The real reason is simple: E85 fuel is a combination of 85 percent ethanol and 15 percent gasoline. Ethanol is an alcohol fuel made from the distillation of corn or other sugar-based carbohydrates, like beets or sugar cane. Straight ethanol has a race-gas-style octane rating of 115. Mixed with 15 percent 87-octane pump gas, E85 lowers this to between 103 and 105 and generally sells for less than 87-octane gasoline. You read that right. We're talking the equivalent of 105-octane race gas for the price of moose-piss pump gas.
There's much more to this story that you need to know, and the devil is most definitely in the details, so you've got to read this whole story to get the facts straight. Yes, you'll have to modify your carburetor to use it; yes, your mileage might suffer by as much as 20 percent; and yes, E85 is not available everywhere-yet. But we successfully tested this stuff in a 12.5:1 compression small-block Chevy against race fuel, and we not only made good power, but we also made a little more torque to boot. Now are you interested? And if you're already thinking this might make a great fuel for a supercharged or turbocharged engine-congratulations-you're thinking like a true car crafter.
Using E85 requires dramatic increases in jet changes and metering block modifications to s
What is Ethanol?
Think moonshine and you're on the right track. The stuff of Appalachian legend also makes an outstanding fuel. But don't confuse ethanol with methanol, which is a completely different fuel distilled from wood or coal. Ethanol is an oxygen-bearing fuel with a chemical makeup of C2H6O. That formula adds power by carrying its own oxygen (nitromethane is CH3NO2-lots 'o oxygen). By way of its three-carbon chemical construction and that single oxygen molecule, the Btu (British thermal unit) heat output of ethanol is not nearly as robust as that of gasoline. The numbers tell the story. One gallon of ethanol is worth 76,000 Btus, while gasoline is around 114,000 Btus. E85 is created by adding 15 percent gasoline to ethanol, which ups the heat count to roughly 83,000 Btus per gallon. By way of comparison, methanol generates a mere 56,800 Btus per gallon, or almost exactly half the Btus of gasoline. This means E85 creates roughly 27 percent less heat output per gallon than gasoline. This is partly why we must burn around 25 to 30 percent more E85 (at wide-open throttle) compared with gasoline to achieve similar results. Stamp this number on your forehead because this volume change is critically important when it comes time to modify the carburetor to flow more fuel.
Part of the switch from gasoline to E85 involves reducing the size of the high-speed air b
Because we must burn more E85 than gasoline to make the same amount of heat in the combustion chamber, E85 is currently not the dashing hero as an alternative daily-driver fuel. While there is a 27 percent reduction in heat, ethanol's strong octane rating allows the use of a higher static compression ratio to take advantage of that resistance to detonation. This means if you were to run E85 in an 11:1 or 12:1 compression engine, E85's higher octane would prevent detonation, which would allow you to run this higher compression ratio and take more advantage of the reduced Btu heat output by squeezing the existing air and fuel a little harder to make more power. The kicker is that right now, E85 is priced only about 30 to 50 cents a gallon cheaper than gasoline. During research for this story, we priced E85 at a gas station in Ames, Iowa, at $2.60 a gallon, which is significantly below the price of 93-octane premium at $3.05 per gallon and far less expensive than $5 to $6 per gallon for 100-octane unleaded race gasoline. Higher-octane race gas is even more expensive. With reduced mileage, E85 only becomes economically attractive from a mileage standpoint when E85 is significantly cheaper per gallon. Also keep in mind that the government is currently subsidizing ethanol at around 50 cents per gallon. If ethanol use increases dramatically in the next few years, expect the government to yank that subsidy in order to cash in. The other big problem with E85 is availability. Because corn is the most popular base stock for ethanol, the Corn Belt states of Iowa, Nebraska, Missouri, and Minnesota are the places where E85 is most prevalent. There are only 15 states that do not offer E85, concentrated mainly in the upper northeast United States along with Alaska, Hawaii, Arkansas, Louisiana, and Alabama. The entire state of California has only one bulk outlet, in San Diego, where E85 can be purchased by the public. But take heart, this situation is rapidly changing, and within a year or two, the E85 landscape could change. But for those of you in the Midwest states, you have no excuse for not checking this stuff out.
We chose a Crane roller with a bit more duration than we normally would choose for a stree
The Octane Game
The definition of octane is rather confusing. It's also called the antiknock index (AKI) and refers to a fuel's ability to suppress detonation. The higher the AKI number, the better the fuel's ability to prevent knock. Octane by itself does not add power to your engine. However, a low-octane fuel will not allow a performance engine to achieve its optimal ignition timing and power due to detonation. Detonation is defined as uncontrolled combustion where high cylinder pressure can auto-ignite end gases in the cylinder that tend to increase the opportunity for this process to be self-sustaining. This creates a massive pressure spike that literally rattles the pistons in their cylinders and kills power. Using a higher-octane fuel allows an engine to take advantage of an ideal timing curve without causing detonation. Once that timing has been achieved, there is no advantage to using higher-octane fuel.
You may have seen octane stickers on gas pumps that list the AKI using the equation R + M / 2 = Octane. The R stands for research octane number (RON) while M represents motor octane number (MON). RON is always much higher than MON, which is why the AKI uses an average of the two numbers to best represent the AKI for street-driven engines. The accompanying chart lists both RON and MON for ethanol and methanol plus a couple of popular race gasolines so you can get an idea of how ethanol and E85 compare.
Quick Fuel Technology supplied the annular discharge 850-cfm mechanical-secondary carb for
Straight ethanol has an AKI rating of 113-115. E85 is generally rated at between 100 and 105, depending upon the manufacturer. The E85 we tested, supplied by American Ethanol out of Chicago, is rated at 105. E85 is most often blended with 87-octane gasoline, since it is the least expensive. Another advantage to ethanol is that the greater volume of fuel required also tends to reduce inlet air temperatures, where evaporating fuel pulls heat out of the incoming air temperature.
|Octane Chart |
| ||RON ||MON ||R+M/2 |
|Ethanol ||129 ||102 ||115 |
|Methanol ||133 ||105 ||119 |
|VP C-16 ||117 ||117 ||117* |
|VP SB 100 unleaded ||106 ||96 ||100* |
|Rockett 100 unleaded ||106 ||96 ||100** |
|*These numbers were taken directly from |
VP's Technical Bulletin on Fuels.
|**From Rockett Racing Brand information |
Completed and on the dyno, our Ed Taylor-built 355 ran flawlessly once we got past too-hot
Air/Fuel Ratio Chart
This accompanying chart offers comparisons of E85 and straight ethanol (or Jack Daniels, if you prefer), to gasoline. Stoichiometric is the term used to refer to the chemically correct air/fuel ratio that also creates the least emissions. This is also the air/fuel ratio most production engines are tuned to achieve at part-throttle. A leaner fuel mixture can generate better mileage, while a fuel-rich ratio generally will make more power by ensuring most of the air is used to create power.
By reading this chart, you can see that the air/fuel ratios for E85 are substantially richer than for gasoline from a percentage standpoint. What we found on the dyno was that we needed to increase E85 fuel flow through the carburetor by roughly 30 percent compared with gasoline. In a fuel-injection system, this could have been easily accomplished by merely increasing the volume of fuel flow (using the base fuel map) by one-third. This is a rough rule of thumb, but we found it to be pretty close for the purposes of our testing.
|Air/Fuel Ratio |
| ||Gasoline ||E85 |
|Stoichiometric ||14.7:1 ||9.7:1 |
|Max power (rich) ||12.5:1 ||6.9:1 |
|Max power (lean) ||13.2:1 ||8.4:1 |
This is what happens when you use a standard-heat-range spark plug in a high-compression m
Since everybody knows that small-block Chevys grow on trees in Southern California, we stopped outside Ed Taylor's Ventura shop one afternoon and picked a ripe 12.5:1 compression 355ci short-block for our test. Fitted with a strong Scat steel forging crank and I-beam rods rotating assembly with a set of SRP forged pistons, we opted for more compression to really put E85's octane rating to the test. Next we bolted on a set of Dart Platinum iron 215cc heads fitted with 2.05/1.60-inch valves. These are the latest wet-flow-technology heads available from Dart, and our flow data reveal the 215s to be a good choice for this test.
Since we wanted to push this small-block a little harder, we opted for a complete mechanical roller cam setup from Crane that pushes the valves open to 0.561 inch lift with 250/258 degrees of duration at 0.050 inch tappet lift. Combined with Crane's recommended valvesprings and set of titanium retainers, we also added a set of Crane Gold Race 1.6:1 rockers to ensure the valvetrain easily spins to 7,000. Moroso supplied the oil pan and pump that we filled with lightweight Royal Purple 5W-20. Since this was an rpm application, we went with an Edelbrock Super Victor single-plane topped with a Quick Fuel Technology 850-cfm annular discharge carburetor and an MSD billet distributor and 6AL ignition box. For the exhaust, we used a set of Hedman 1 7/8-inch headers hooked to a pair of 2 1/2-inch Flowmaster mufflers.
While the engine ultimately made 466 hp, our goal had little to do with ultimate power. (As it is, this engine made 1.3 hp/ci.) Of much more concern for this test was an engine that was both durable and repeatable and would allow us to evaluate the differences in fuel between race gas and E85. From that standpoint, this little 355 was a success.
One of the first things we learned is to invert the float bowl to level the float and then
At first, we thought all we had to do was plug bigger jets in a standard metering block to compensate for the less Btu output of our E85 fuel and we'd be in business. But after our test and in talking with the guys at Quick Fuel, there's more to this business than a quick jet change. They told us our test with the standard Quick Fuel metering blocks indicated it might be better to start with methanol-style metering blocks and then add the internal air bleeds that will help establish the proper fuel curve. This is because a standard Holley metering block maxes out in terms of fuel delivery with jets around 92 and a 0.070-inch power-valve channel restriction (PVCR). Increasing the jet size or PVCR beyond these points delivers a smaller percentage of fuel-flow increase. This is why drilling out the PVCR on our billet blocks didn't help all that much. It should have drowned the engine in fuel, but it was actually only worth a small percentage of additional fuel. The part number listed in the parts list is basically a methanol metering block configured with bleeds tuned for E85. This will guarantee sufficient fuel-flow capability to feed any normally aspirated engine.
The Dyno Test
Our test concept was simple-run the engine on race gas, establish a repeatable power baseline and then modify the carb with new metering blocks, change fuel to E85, and see what happens. After we repaired the damage from our experiment with heat-ravaged spark plugs, the motor responded with a pleasant and repeatable 460 hp on a 50/50 mix of 117-octane race gas and 91-octane pump gas. In theory, this produced an AKI of 104. After a few jetting and timing experiments, we came up with a peak horsepower number of 466 at 6,800 rpm. Now we were ready to test the E85.
E85's increased volume requirement demanded we drill the secondary power valve channel res
The only real changes we made to the Quick Fuel 850 annular-discharge carburetor to use the E85 fuel was to swap in the Quick Fuel E85 metering blocks and change the high-speed air bleeds on top of the carburetor. We knew going in that E85 would demand a bunch more fuel, and that's exactly what transpired. The jetting combination actually knocked on the door of 100 secondary jets, and that's after we had already added a power valve to the secondary side that was not used on gasoline. With 99 rear jets, we decided to drill out the power valve channel restrictors in the secondary metering block from 0.070 to 0.080 inch in diameter to give us some jetting room.
In discussing this change with Quick Fuel, we were told the problem was likely a restriction after the main well, perhaps in the drilled passage leading to the annular boosters. Increasing the size of this passage would ultimately reduce our overall jetting requirements.
The following chart illustrates the massive increase in fuel-flow area required when running E85. Despite these changes, this did not require a dedicated methanol-style carburetor. All we did was mildly modify both metering blocks. Otherwise, this was a typical Quick Fuel Technology gasoline 850-cfm carburetor. As an example, just changing from a 72 to an 80 primary jet is a jet area increase of 39 percent.
As you can see from the horsepower chart, the E85 surprised us with a sizeable midrange power increase over the race-gas blend that Quick Fuel claims is typical for an ethanol or methanol type of blend.
E85's greater fuel-volume demand will also place a greater load on fuel pumps. This small
We also noticed that once we increased the E85 fuel flow sufficiently to make the engine happy, it seemed like the engine was much less sensitive to small changes in fuel flow. Duttweiler said this is also typical of a methanol engine. Generally, a gasoline engine will respond to a jet change of two jet sizes, but once the fuel flow was close, it seemed the E85 package was more forgiving and less touchy in terms of power gained or lost. We did not get into timing requirements with E85 because of time constraints. Total timing was maintained at 34 degrees.
Overall, the test was successful, and it's clear E85 has earned a high-octane place in the performance-fuel market. There are still several issues that are as yet unclear in terms of how well gasoline fuel delivery systems will react regarding long-term use of E85. Our research on the subject has uncovered conflicting information. We spoke to a couple of fuel-pump companies, and they claimed their pumps should not have a problem with E85, since ethanol is not nearly as corrosive as methanol. More experience over a longer period of time will dictate any extended-use limitations with E85, but the future for an alternative fuel that can make big power is certainly bright. And now you can let those tree-huggers know they're not the only ones using yellow to go green.
Click here for the E85 fuel test dyno chart
|Jet and Air-Bleed Chart |
|Primary ||Gasoline ||E85 |
|Jet ||72 ||90 |
|PVCR ||0.070 ||0.070 |
|High-speed bleed ||32 ||25 |
|Jet ||80 ||96 |
|PVCR ||Blocked ||0.080 |
|High-speed bleed ||32 ||25 |
|Parts List |
|Description ||PN ||Source ||Price |
|Scat 4340 crank ||435010-2 ||Summit Racing ||$989.95 |
|Scat 4340 I-beam rod ||25700P ||Summit Racing ||$199.95 |
|SRP forged pistons ||140674 ||Summit Racing ||$534.39 |
|Crane roller cam ||118591 ||Summit Racing ||$435.99 |
|Crane roller lifters ||11519-16 ||Summit Racing ||$309.95 |
|Crane valvesprings ||96870-16 ||Summit Racing ||$209.95 |
|Crane titanium ret. ||99669-16 ||Summit Racing ||$287.39 |
|Dart Platinum 215cc ||catalog ||Summit Racing ||catalog |
|Edelbrock Super Vic ||2925 ||Summit Racing ||$207.95 |
|Quick Fuel 850 carb ||Q-850-AH ||Summit Racing ||$638.60 |
|E85 metering block ||34-106 ||Summit Racing ||$125.00 pr. |
|MSD distributor ||85551 ||Summit Racing ||$225.95 |
|MSD-6AL box ||6420 ||Summit Racing ||$229.88 |
|MSD plug wires ||31189 ||Summit Racing ||$78.88 |
|Royal Purple 5W-20 ||RP01011 ||Summit Racing ||$11.95 qt. |
|American Ethanol||Powerbuilt Tools/Alltrade|
|Chicago, IL||Long Beach, CA|
| || |
|Crane Cams||Quick Fuel Technology|
|Daytona Beach, FL||Bowling Green, KY|
| || |
|Duttweiler Performance||Royal Purple|
|Ventura, CA||Porter, TX|
| || |
|Innovate Motorsports||Sportsman Racing Pistons|
|San Juan Capistrano, CA||Huntington Beach, CA|
| || |
|Mr. Gasket Co.|| |
|Cleveland, OH|| |
|216/688-8300, ext. 500|| |