LPG or E85 conversion, what's involved? - Fuelly Forums

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Old 09-04-2008, 08:47 AM   #1
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LPG or E85 conversion, what's involved?

Ok, so that title is quite broad, but I've really been thinking about LPG conversion and only hinderance is I really don't have any money to spend and some kits are over $1k. Then I thought about E85 and saw all that's really neccessary is making sure you have no rubber fuel lines (mine are all steel) and bigger injectors or just increasing the pulse widths to my current injectors. I found a site that sells a box that does just that but it's retardly overpriced: http://www.flextek.com/shop.htm I could build 2 megasquirts for that and all I really need is a broader PWM wave.

So, start with E85, my vehicle is a '94 K1500 with a SBC 350. Probably one of the most common engines out there and any kit we can design with proven results would have a great market. My fuel line is all steel, but I need to know, should I worry about my fuel pump internals at all on E85? Other than that I will just make my own little ECU box thing from spare electronics to hook to my normal injectors. Is there anything I'm missing?

LPG is well documented and I'm hoping I can buy used parts and mix and match and try to keep it under $300. My only concern is turning off the fuel pump and injectors. My truck has EFI and an ECU but the ignition is not electronic so I don't think I should have any worry about the ECU messing anything up. But should I? What would the ECU do if it was reading wacky values from the O2 sensor? As long as it's only output is trying to increase PWM or something to injectors which I already grounded out then it can't harm me. Any thoughts?

Lastly, and this is the biggest hassle, to get the most out of both systems I need to increase my compression in my truck. It's probably only 8.5-9:1 now and I've read LPG can run anything from 14-17:1 and E85 12.5-13.5:1. So I thought, for cold weather starting I need to keep gasoline, but if I have increased compression that won't work, so I should go for a dual E85/LPG system. Does E85 have any cold weather issues?

Also LPG is 110+Oct and I thought E85 was just about that (like 105-110), so why are the CR numbers so different. What's a good, reliable CR for these fuels, 13:1 maybe?

I guess it's kind of a moot point because I want something simple, pulling and milling the heads and getting a thinner HG will likely only get me to 10:1 if that and I really don't want to deal with different pistons and their expense. Would even different pistons be enough though? Would I need to mill the block too to reach those numbers? That must involve remove the entire engine.

Anyway, I haven't even looked at LPG or E85 costs to see if there's any point to this idea but haven't seen a really good discussion on either idea on a SBC 350 either and would think it'd be a pretty hot topic.

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Old 09-04-2008, 09:44 AM   #2
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On a 94 K1500 with a 350 it already has fuel lines to handle the alcohol. The biggest problem with E85 in that vehicle is cold starting. The computer will automatically compensate for E85 because the o2 sensor will report a lean condition and the computer will step up the injectors till it gets a reading its happy with. For starters try filling up with E85 when you already have 1/2 tank of gasoline. This will be E48 if you are already running a 10% ethanol blend, or E42 if you are using pure gasoline. Try this and see what your results are. If you find it starts ok, and runs fine step it up and run higher concentrations of E85. If your vehicle complains or lights the CEL (Check Engine Light) then back off. You may be able to get away with using E85 for most of the year except for the coldest winter months, depending on your local climate. I would love to try E85 in my 98 K1500, but its really not available in my area. Remember your mileage will go down running on E85(Alcohol does not have as many BTU's per gallon as gasoline), so E85 will not be an economical choice unless its at least 10% cheaper than gasoline. You may be better off trying to find a station that sells pure gasoline with no ethanol in it. This will increase your MPG, and even though it may cost a little more may be worth it.


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