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Old 09-06-2010, 09:58 AM
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Running on e85 fuel, results

After studying Cliff Ruggles' excellent book, "How to Rebuild and Modify Rochester Quadrajet Carburetors", I began to rebuild the carburetor with the idea of converting it to a dedicated e85 carb. The trick, of course, is understanding that the carb needs to be "fattened up" somewhere between 17% and 34% to create the proper richer air/fuel ratio. I based this on the recommended 20-40% increase to run pure ethanol and adjusted down to compensate for the 15% gasoline in the fuel.

A great help in understanding tuning and the importance of calculating the metering area was found in the online essay, "How to Tune a Q-Jet" by Lars Grimsrud. He is considered a master tuner and has numerous technical essays online.

The carb I purchased for modification is from a 1976 Pontiac 400 or 455 application, identical part number to the one on the car. I ended up modifying the original carb and the newly rebuilt one, back and forth, until I started seeing improvements.

I am not finished finely tuning both carbs, yet, but I've achieved some interesting results that run contrary to what some have said I should expect from the conversion, namely a loss of fuel economy and a drop in power. Instead, the highway fuel mileage is the same with what the car ran before, that is, on economy conservative driving mode, which is what concerns me. Of course, it sucks down fuel at WOT, just as any powerful engine will, but it doesn't appear to be any worse than on gasoline, nor do I care. The power is roughly equal or even slightly better, judging by testing with the G-Tech performance computer and quarter mile trap speeds.

Driveability is excellent: I had to adjust the idle mixture screws out 6 1/2 turns to get the highest and steadiest vacuum readings. I also advanced the distributor a bit, though some argue e85 likes to be retarded a little and I need to experiment more to see which produces the highest trap speeds. Subjectively, the engine seems to idle more smoothly and also seems to run quieter, especially noticeable at idle and low cruising speeds. The car also seems to produce more bottom-end torque judging by how easily the tires spin, though the computer has not picked up this difference.

Overall, I'm very pleased with the performance on e85 and feel there's still plenty of room for improvement to optimize the engine for this fuel, such as raising the compression. It's like having the luxury of running 105 octane racing fuel all the time with the added benefit of chemical intercooling.

Thanks to Cliff for answering some of my technical questions and great service in getting the rebuild kit I needed and repairing my throttle plate. And thanks to Lars for posting much-needed tuning advice for free.

This is my combo so far for my 455 with 6x heads: #80 primary jets with .044 primary rods, .135 fuel inlet seat, .094 idle mixture screw holes, small nitrophyl float adjusted to within 1/4 of the top, CH secondary metering rods. APT adjusted as per Lars' instructions. I'll post updated modifications if they result in a measurable improvement in performance.

Note: I'd also like to suggest that my fuel consumption may have been much better on the original (before converting to e85) gasoline settings if it wasn't running so rich. The best I've been able to achieve was close to 16 mpg, (4L60 2.73 gears) and that is what I'm getting on e85. Still, I'm skeptical I could ever get 20 mpg on gasoline under even the best circumstances, (though I once got 24 mpg going downhill from the mountains to the piedmont!) Also, I am not tuning with a wideband air/fuel meter, yet, so I can't quantify how lean it is running, however the engine seems to "like" the new fuel and the temperature gauge is cool as always, detonation non-existent.

With e85 able to support 14 or 15:1 compression ratios or high-boost in supercharged applications, the potential for super power increases surpasses pump gas applications.

I'd like others to post their experiences with this fuel, rather than opinions based on unproven assumptions.

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Old 09-06-2010, 10:23 PM
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Where do you purchase your E85? I live in Washington State and there are only 4 places statewide that sell it. 3 of them being on military bases. It also costs about twice as much as Premium unleaded.....
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Old 09-06-2010, 10:26 PM
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I apologize for the fuel station count, there are actually about 12-15 scattered across the state, prices are not what they were last time I checked either...again my own ignorance, it seems to me though with the "advantages" of e85 to get from one station to the next while traveling I would have to use a regular fuel station along the route...I think your research is a great oppertunity fo rsoem of us to look at the option of fule choices...for now, and for me a regular fuel station will have to suffice

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Old 09-07-2010, 11:52 AM
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e85 fuel prices & availability

Agreed: If it wasn't inexpensive and abundant I probably would not have made the switch. We have it here in town at $2.15/gallon and thanks to Spinx and Hickory Point gas stations it has spread well throughout this state of South Carolina.

If I drive conservatively on the highways my 300 mile range should keep me from running out. And until I decide to up the compression to 12:1 or higher or bolt on a blower, for now, I can change it back to run on premium by swapping back the old jets. I've gotten pretty good at pulling the airhorn off from all the tuning sessions. Also, as I wrote, I do have two Q-Jets, and once I nail the optimum set-up, I can also put the other one back into gasoline mode and swap carbs in under ten minutes. No, it's not flex fuel, but it beats the expense of an electronic fuel injection system. Remember, too, that if I put gas in it'll just run real rich, so I could probably limp home or to the next e85 stop.
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Old 09-08-2010, 02:28 AM
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I must say I am quite envious, my 2001 2.2L 5 speed S10 with 18.3 +2.7 gallon reserve tank yeilds about 24 mpg at 65-70 mph with an older canopy on it.

My wife is dreading driving our 86 C2500 3/4 ton with rebuilt 454 and a 1963 camper that weighs in at about 1350 pnds to her fathers 218 miles away...

I was thinking about my S10 and what if anything I need to do to run E85..? It is a flexfuel but how will mixing the current fuel with the E85 work?

I am thinking about giving it a try to see how the truck runs as I dont drive it too much (82k miles since 2001) and I have located a service (cough cough) station about 4 miles away just outside of Joint Base Lewis-McCord.
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Old 09-08-2010, 05:25 AM
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Good Stuff......
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Old 09-08-2010, 09:58 AM
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Quote:
Originally Posted by muddi1
I must say I am quite envious, my 2001 2.2L 5 speed S10 with 18.3 +2.7 gallon reserve tank yeilds about 24 mpg at 65-70 mph with an older canopy on it.

My wife is dreading driving our 86 C2500 3/4 ton with rebuilt 454 and a 1963 camper that weighs in at about 1350 pnds to her fathers 218 miles away...

I was thinking about my S10 and what if anything I need to do to run E85..? It is a flexfuel but how will mixing the current fuel with the E85 work?

I am thinking about giving it a try to see how the truck runs as I dont drive it too much (82k miles since 2001) and I have located a service (cough cough) station about 4 miles away just outside of Joint Base Lewis-McCord.
A Flex Fuel vehicle will run on any combination of E85 to "normal" gasoline, but will perform best using one or the other.

The best scenario would be before adding E85 to the tank, run out as much of the fuel now in it, as is practical. Then tank up w/the E85.
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Old 09-08-2010, 11:40 AM
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E-85 is readily available in OHIO and sells for $.40-60 cheaper than 85 octane pump gas.

The 2 biggier towns Norwalk to the North and Mansfield to the South have 2-3 stations each.

I have heard you get 30% less mileage from E-85 and need some changes to your fuel system components.

E-85 seems to like 12:1 CRs also.
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