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E85 vs. 114-Octane Race Gas on the Dyno With a Boosted Small-Block!

Engines Of The Corn

Richard Holdener Jan 19, 2019
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Let’s face it; if you are a car guy (or gal), this is a great time to be alive. Performance has never been easier or more powerful than it is right now. One of the most impressive routes to improved performance has to be boost. If there really is any replacement for displacement, it has to be positive pressure. The power gains offered by the many forms of forced induction are sizable, and therein lies the potential problem. While adding boost to almost any engine can improve the power output by 40-, 50-, or 100-percent (or more), this is only possible with sufficient octane. Call it power, call it torque, or even call it cylinder pressure, there is a finite limit to just how much the combustion chamber will tolerate on any given octane. The lower the octane, the lower the amount of boost and/or timing than can be run. Less timing and/or boost means only one thing, less power. In the world of high performance, race gas rules and pump gas drools!

As wonderful as high-octane race gas sounds, there is, of course, a downside: the price. The great thing about something like premium-unleaded pump gas is that it is both affordable and available, but it lacks the power-giving octane of race gas. Unfortunately, race gas is more than just a little more expensive than pump gas, so you have to decide whether the extra power potential is worth the price. For most of us, trips to the track almost always necessitate at least a few gallons of the good stuff, you know, just so we can crank it up and run a good number to go brag about to our fellow enthusiasts online. But this begs the question, what about the everyday enjoyment? Spending a few extra bucks for track trips is one thing, but having to shell out double (or triple) the price of pump gas on every fill-up is something most of us won’t even consider. What if we told you there was a middle ground, a fuel that comes straight from the pump (in many areas), costs less even than regular pump gas, and offers plenty of power-enhancing octane? What is this magic elixir? Well, the pump says E85, but it goes by the street name of corn!

The E85 designation is actually a bit of a misnomer, as it implies a mixture of 85 percent ethanol and 15 percent gasoline. Though this seems straightforward enough, the reality is that the actual blend varies greatly. According to the U.S. governing body (regulation ASTM 5798), the ethanol content of E85 can range from as low as 51 percent to as high as 83 percent. Obviously, this variation can substantially alter the tuning requirements for any combination. The reason for this is that ethanol and gasoline have different stoichiometric values (the ideal ratio of air and fuel to support complete combustion). For gasoline, the stoichiometric value is 14.7:1, while E85 is 9.8:1. What this means is that it requires more E85 to reach the same air/fuel mixture as gasoline. What this also means is that some of the cost savings of E85 (being less expensive at the pump compared to pump gas) is offset by increased fuel usage (meaning a reduction in fuel mileage). The ethanol can also be corrosive to some fuel systems not designed for the alcohol-based fuel. As we mentioned earlier, and the reason for this test, is that E85 has a much higher octane rating than pump gas. In fact, the Rockett Brand E85 we tested rivaled the 114-octane race gas we compared it to. As a side benefit, the ethanol-based E85 offered a substantial decrease in inlet air temps, further warding off harmful detonation, irrespective of the increased octane.

Now that we know the pluses and minuses of E85, let’s see how well it works. Right off the bat, any contest between 112-octane E85 and premium unleaded pump gas (91- or 93-octane) would be no comparison. The E85 offers more power, even before we get into the added ability to run more timing and/or boost from the lack of octane on the pump gas. Knowing this, we decided to compare the E85 to race gas, in this case, Rockett Brand 114-octane. The use of race gas allowed us to run full timing on both of our blower combinations and demonstrate the added benefits of just the E85 (with no changes to the A/F ratio, timing, or boost). For our engine, we chose our power-adder ready BluePrint Engines 383 stroker test mule and opted to try this test on two very different blowers: a Weiand 6-71 roots and a ProCharger F-1A-94 centrifugal unit. So let’s see how corn can help your blown engine push out more power.

002 E85  Blueprint  6 71  Procharger  Weiand 2/17

The test engine used for both our superchargers was a power-adder ready 383 crate engine from BluePrint Engines. The small-block stroker featured forged internals, low compression, and fancy aluminum heads.

003 E85  Blueprint  6 71  Procharger  Weiand 3/17

For our first race fuel versus E85 comparison, we installed a polished Weiand 6-71 supercharger onto the boost-ready BluePrint small-block.

004 E85  Blueprint  6 71  Procharger  Weiand 4/17

The dual-quad adapter allowed us to install a pair of blower-specific 750-cfm Holley carbs. Though not designed for E85 use, we made them work with a simple jetting change.

005 E85  Blueprint  6 71  Procharger  Weiand 5/17

The carbs were controlled by a dual-quad linkage, while an Aeromotive fuel pump ensured plenty of fuel flow to the carb inlets.

006 E85  Blueprint  6 71  Procharger  Weiand 6/17

The blower and crank pulleys allowed us to adjust the boost pressure supplied by the Weiand 6-71 supercharger. We made no changes to the 37-tooth crank and 36-tooth blower pulley combination during our test.

007 E85  Blueprint  6 71  Procharger  Weiand 7/17

The small-block was configured on the engine dyno with a set of 1 3/4-inch long-tube headers and MSD billet distributor.

008 E85  Blueprint  6 71  Procharger  Weiand 8/17

First up was the Rockett Brand 114-octane race fuel. For you tech nerds, check out the specifications listed on the typical inspection data sticker.

009 E85  Blueprint  6 71  Procharger  Weiand 9/17

The 114-octane race fuel was compared to the Rockett Brand E85. Rocket listed the octane rating for their E85 as 112, but E85 from the pump can vary greatly.

010 E85  Blueprint  6 71  Procharger  Weiand 10/17

Naturally, it was necessary to dramatically increase the jet sizing (fuel flow) when running E85. The jetting on our dual quads went from 76/87 to 99/99 once we switched over to the E85 (to maintain the same A/F ratio on our Lambda meter). E85 has less potential energy compared to gasoline, which is why mileage suffers with E85, but we’re using it for its other benefits.

011 E85  Blueprint  6 71  Procharger  Weiand 11/17

Running the supercharged 383 on 114-octane race fuel allowed us to get aggressive on the tune. We dialed in 30 degrees of total timing and ran the A/F ratio at 11.8:1. Run with 114-octane Rockett race fuel, the supercharged 383 produced 643 hp and 589 lb-ft of torque at 11.4 psi. After jetting the blower carbs for E85, the power output jumped to 700.1 hp and 646 lb-ft of torque. In addition to the power gains, the E85 dropped the inlet air temps by over 70 degrees, from 166 degrees to 92 degrees!

012 E85  Blueprint  6 71  Procharger  Weiand 12/17

After the successful test on the 6-71–blown small-block, we shifted gears and installed a ProCharger F-1A-94 centrifugal supercharger.

013 E85  Blueprint  6 71  Procharger  Weiand 13/17

Unlike the 6-71, the F-1A-94 supercharger was run with a single blow-through 850-cfm Holley carb along with a carb bonnet. In preparation for the blow-through system, we installed an Edelbrock Victor Jr. intake and 1-inch carb spacer. The spacer allowed us to run a temperature probe under the carb.

014 E85  Blueprint  6 71  Procharger  Weiand 14/17

The one major difference between the blower tests was that we employed an air-to-water intercooler on the blow-through F-1A-94.

015 E85  Blueprint  6 71  Procharger  Weiand 15/17

Like the test with the 6-71, it was necessary to dramatically increase the jet sizing on the CSU carburetor when switching to E85.

016 E85  Blueprint  6 71  Procharger  Weiand 16/17

We duplicated the race fuel/E85 test on our 383, but this time the stroker was equipped with a ProCharger F-1A-94 centrifugal supercharger. Run on 114 Rockett Brand race fuel, the supercharged small-block produced 787 hp and 667 lb-ft of torque. After switching over to Rockett Brand E85, the power output jumped to 815 hp and 687 lb-ft of torque at a very comfortable 13.5 psi. The gains were not quite as dramatic on this application as the 6-71, possibly because the intercooler had already significantly cooled the charge air (thus limiting the cooling effect of the E85), but it still shows the power gains possible by running E85 in your boosted application.

017 E85  Blueprint  6 71  Procharger  Weiand 17/17

Photos by Richard Holdener

Sources

Westech Performance
Mira Loma, CA 91752
951-685-4767
www.westechperformance.com
ProCharger
Lenexa, KS 66215
913-338-2886
www.procharger.com
Blueprint Engines
Kearney, NE
800-483-4263
http://www.blueprintengines.com
Edelbrock
Torrance, CA 90503
800-416-8628
www.edelbrock.com
MSD
El Paso,
888-258-3835
MSDPerformance.com
Holley/Hooker
270-781-9741
www.holley.com

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