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Old 09-27-2016, 12:38 AM   #1 (permalink)
Rogue Engineer
Join Date: Apr 2011
Location: Cottage Grove, OR
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E85 in 2001 Civic DX - It works!

I want to share my experience getting my '01 civic DX to run E85. I've only taken the car out twice so it's still pretty fresh and I have a couple of tests to do that I would also like to share. I believe the method that I have used will prevent the car from running on gasoline, although I think a mixture of up to 4 gallons E10 gas and the balance (7 gal I think) of E85 will run.

The method I used involved installing injectors from an RSX-S of the same generation as the civic. I believe the stock injectors are 240 cc/min and the new ones are 310 cc/min. I was shooting for a 30% flow increase to account for the increased fuel requirements over gas needed to meet stoichiometric conditions. I got them off ebay last week for $66. They were shipped doused in carb cleaner, so my mailbox had a telling odor upon my arrival.

I had understood that the injectors would be a direct swap with the exception of having to use longer fuel rail mounting posts. The stock posts are M6X1.00 and I think the new ones need to be at least 35 mm long. I got 40 mm bolts to replace the posts, but they were a little too long. In the same trip to the hw store I managed to think ahead enough to get a 100 mm long piece of all thread. (I have to mention that I had to put everything back together the day before because I didn't have the posts. I didn't know what size to get!) I cut the all thread roughly in half with a hack saw and smoothed the cut ends down with a flat file. I observed how the threads on the factory end came together and worked my end to look the same. I slowly threaded the factory nut onto the cut edge and worked it back and forth until I was sure it would go on smooth when I went to do the install. I was pleased that it took much less time than other attempts during past projects. I got zinc coated all thread, so maybe I was remembering trying to do it on a stainless piece.

There is a spacer that holds the fuel rail at the correct height so that when you tighten its mounting nut it won't crush the injector. You have to use a larger spacer. I used the stock ones and a big nut. It made the spacer a little over twice as high. When I used the wrong size spacer the first time I put it together I over tightened the fuel rail mounting nut and broke off a small tab on the injector that serves the purpose of I think keeping the injector aligned radially and vertically. It's really small so I think it's just there as a mechanical reminder. I tried to make a new one and failed and now the car is running fine with no leaks without the tab. I inspected the position of the injector relative to the fuel rail, the head, and the injector mounting clip after I tightened the fuel rail down and it looked the same so I carried on.

When using the longer posts, and the longer injectors, the fuel rail doesn't slide into position very well. I put the rail and injector assembly in first, having put motor oil on the injector o-rings, and then held the spacers in place while I put the rail mounting bolt in from the top. I installed the factory edge of the bolt into the aluminum threads of the head below.

I also removed the air filter housing mounting rod that is attached to the head before installing the fuel rail to make space. To reinstall it required about 1/4" worth of washers. The same bolts worked fine, and the filter housing seems to fit fine on the throttle body. Getting those 10 mm bolts on and off would be a lot easier with a ratcheting wrench.

Prior to doing this swap I had run the car on up to 4 gal of E85 with the balance of the tank being E10. I think the tank holds about 11 gal. Above 4 gal I got an over lean MIL code. The stock ECU has a fuel trim parameter that can compensate for the increased fuel demand, but it only goes so far. I think +- 25% I think the way fuel trims work is they increase the injector duty cycle by the same factor across the entire fuel map. With the stock narrow band O2 sensor the ECU just looks for stoich A/F ratio and adjusts the trims until the condition is met. Using larger injectors sized to supply the increased fuel needs of E85 over gas puts more fuel through for the same duty cycle, and the ECU uses the fuel trim to fine tune your calculation.

I read and though about this a lot before doing it, and I'm sure I could have provided a bunch of links and not repeated writing what other people have done, but I wanted to put together the whole package in my specific experience in case anybody is trying to do something similar. Maybe somebody will save a trip to the hardware store.

I will measure the fuel economy, as well as the fuel trims and share them here. I was getting about 36 mpg driving fast, about 40 mpg driving slow. I have michelin hydro edge tires and full moon hub caps.

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MobilOne (10-03-2016)