omega_rugal Posted September 13, 2016 Share Posted September 13, 2016 A very simple question for those who had made this conversion themselves i got a complete "x-branded" complete LPG system from a wrecked 89 cherokee which had the venerable I6 4.0 AFAIK this truck was running entirely on LPG since it was converted, i cleaned up and i can say i`m ready to do the job once i get free time note: i have never done this before so... once i have bolted everything on and got every hose in place... do i just drain/burn the leftover gas and let the LPG in? or should i disconnect the fuel pump, inyectors? anything? what your guys think: 1- let the gas dry out, switch to LPG and never look back 2- there`s one or two more steps to take in account in order to NOT fry your Comanche... Link to comment Share on other sites More sharing options...
DirtyComanche Posted September 14, 2016 Share Posted September 14, 2016 I need more details to tell you anything useful. Pictures of what you have and info on how it was installed on the Cherokee. Link to comment Share on other sites More sharing options...
omega_rugal Posted September 14, 2016 Author Share Posted September 14, 2016 I need more details to tell you anything useful. Pictures of what you have and info on how it was installed on the Cherokee. hard to check that out, the cherokee wasn`t mine, must be torn to pieces right now, but i got the lpg system for free so i can`t complaint, i have: 1- a vaporizer unit, with both in/out water hoses, a low pressure hose and a solenoid actuated high pressure valve 2- a mixer that goes between the throttle body and the air filter.. never seen those the only thing missing is the tank, someone else beat me to it, and i know for certain it works because it was running, but the transmission didn`t work and the frame too bent to be usable i`m at home now, the equipment is in a friend`s house who`s giving me a hand with the conversion, i`ll take some pics tomorrow... Link to comment Share on other sites More sharing options...
DirtyComanche Posted September 14, 2016 Share Posted September 14, 2016 That was an actual dual fuel setup. I'm not a fan of them. But if you just want to run it as a propane only setup I would pull all of the Renix EFI stuff, just leave the injectors and rail to plug the holes in the intake manifold, and drop a GM HEI distributor in it. That would be basically the best setup in regards to power and reliability. Why do you want to run propane? Link to comment Share on other sites More sharing options...
omega_rugal Posted September 14, 2016 Author Share Posted September 14, 2016 That was an actual dual fuel setup. I'm not a fan of them. But if you just want to run it as a propane only setup I would pull all of the Renix EFI stuff, just leave the injectors and rail to plug the holes in the intake manifold, and drop a GM HEI distributor in it. That would be basically the best setup in regards to power and reliability. Why do you want to run propane? GM HEI? does it bolts right in or needs modding? and yes i would like to run propane only, way cheaper where i live than gas... Link to comment Share on other sites More sharing options...
DirtyComanche Posted September 14, 2016 Share Posted September 14, 2016 Be careful with propane appearing cheap. It has only 80% of the BTUs as the same amount of gasoline. To use a GM HEI, IIRC, you need to get an inline 6 version and you need the drive gear off an AMC 360 distributor. I don't know if other models will work or not, it was years ago when I did mine, but the info is out there as it was a common swap into carbed CJs and YJs. Link to comment Share on other sites More sharing options...
omega_rugal Posted September 14, 2016 Author Share Posted September 14, 2016 Be careful with propane appearing cheap. It has only 80% of the BTUs as the same amount of gasoline. To use a GM HEI, IIRC, you need to get an inline 6 version and you need the drive gear off an AMC 360 distributor. I don't know if other models will work or not, it was years ago when I did mine, but the info is out there as it was a common swap into carbed CJs and YJs. well i don`t plan to race it or enter a towing contest, i can take a 80% cut in power as long as i can drive around all day Link to comment Share on other sites More sharing options...
DirtyComanche Posted September 14, 2016 Share Posted September 14, 2016 It's not the power cut that's the issue, it's that it takes you that much more fuel to get somewhere; a gallon of propane will only get you at best 80% as far as a gallon of gasoline. There also tends to be other losses as MPFI (even the Renix setup) is quite efficient when it comes to controlling the A/F ratio, whereas the older demand regulated propane setups are just not that good. When I did my conversion I used an Offenhauser (sp?) intake meant to put a 4 barrel carb on a 258 (I just modded it a bit) and an Impco 425 mixer, Model E regulator, and a VFF30 lockoff. I don't feel there was any appreciable power loss compared to running the Renix setup with the restrictive intake manifold and throttle body. I did spend some time trying to get the timing dialed in as well as possible too, which is a big thing, you will need a good dial back timing light to do this as you're going to be running a lot of advance. Link to comment Share on other sites More sharing options...
Zebvance Posted September 14, 2016 Share Posted September 14, 2016 Also, correct me if I am wrong... but if you are going to use a typical forklift propane tank, those are about 8 gallons. SO, lets say your Mj is getting 15 mpg city (which is what i see around here as a avg for the 4.0). When running LP account for the 20% loss in fuel efficiency (referring to statement earlier) you will be taking a 3 mpg hit. (15mpg x 0.20= 3 mpg) therefore, (15mpg - 3mpg =12mpg) Now most Comanche fuel tanks are 18 gallons compared to the 8 gallon forklift tank. So right there you are taking another big hit for the amount of miles between fill ups. For comparison with a stock Comanche you can get some where around (15mpg x 18 gallons = 270) 270 miles between fill ups. With your LPG you are looking at (12mpg x 8 gallons = 96) 96 miles between fill ups. So unless you had multiple tanks full ready to swap in, in the bed. Or were running a dual tank set up, you really limiting where and what you can do with your truck. Not to mention that you would most likely have to go out of your way just to fill up seeing a how there are not LP refill suppliers on every corner. So are you really saving that much in fill ups to go through all that trouble? What are you really planing on doing with the truck? Wheeling,DD, weekend driver? The reason most people that switch to propane is not for the price of gas, its because with a propane set up you can go wheel at extreme angles without having to worry about fuel spilling out of your fuel tank and being able to use a carbed engine without it getting choked out with fuel on inclines/declines. Link to comment Share on other sites More sharing options...
DirtyComanche Posted September 14, 2016 Share Posted September 14, 2016 The reason most people that switch to propane is not for the price of gas, its because with a propane set up you can go wheel at extreme angles without having to worry about fuel spilling out of your fuel tank and being able to use a carbed engine without it getting choked out with fuel on inclines/declines. Yup. And with the older demand regulated propane setups you need very little wiring. The only wires I needed were to power the ignition, and for the starter and alternator, since I used a vacuum lockoff and you only really need the primer when the engine is quite cold. Don't get me wrong, I was happy with my setup, but it was a wheeler only at that point. Swapping bottles is a pain in the @$$ if you're driving on the street, and most permanent tanks that will fit a Comanche are bed mount and take up a ton of space. Link to comment Share on other sites More sharing options...
omega_rugal Posted September 14, 2016 Author Share Posted September 14, 2016 I drive around town carrying things, usually not heavy stuff but i do come and go all day... i don`t have the tank yet but i plan to get one that fits on the truck bed transversaly so it can double as a bench seat for 2.. oh and believe me, where i live gas is so @#$%ing expensive (and will come up and up) while LPG is cheap enough so you can drive twice as much for the same $$$ Link to comment Share on other sites More sharing options...
Rockfrog Posted September 17, 2016 Share Posted September 17, 2016 You can make some power back by upping the compression ratio ... Factoring in that propane is equivalent to 110 Octane. Sent from my SGH-I337M using Tapatalk Link to comment Share on other sites More sharing options...
DirtyComanche Posted September 20, 2016 Share Posted September 20, 2016 You can make some power back by upping the compression ratio ... Factoring in that propane is equivalent to 110 Octane. Sent from my SGH-I337M using Tapatalk Not really worth it in his case. Link to comment Share on other sites More sharing options...
Rockfrog Posted September 20, 2016 Share Posted September 20, 2016 No, but can be done, I used to have a 300-6 I was building as a propane motor. 240-6 head, 390 Pistons, custom intake, then the kids came and I had to stop being a Ford guy. Sent from my SGH-I337M using Tapatalk Link to comment Share on other sites More sharing options...
omega_rugal Posted November 4, 2016 Author Share Posted November 4, 2016 forget about that system, my friend liked it so i let him have it, now i got another LPG system, this one is complete, except for a few hoses that are a little old, everything seems to be working, so i get back to my original question: does the renix will work "out fo the box"? i mean with LPG it`s only job of the ECU will be the ignition, if the ECU thinks it`s running on gasoline, it will send the right signal to the ignition coil right? Link to comment Share on other sites More sharing options...
DirtyComanche Posted November 4, 2016 Share Posted November 4, 2016 Yes, it will, it doesn't know any better. Likewise, you can drop a HEI in a Renix and leave it to only control the injectors. Edit, the timing curve will be way less than ideal. At the very least get a high altitude CPS or mod the one you have. Link to comment Share on other sites More sharing options...
omega_rugal Posted November 5, 2016 Author Share Posted November 5, 2016 mmm modding a regular 4.0 distribuitor to run without the ecu would be better... but that gotta wait for now... Link to comment Share on other sites More sharing options...
omega_rugal Posted November 22, 2016 Author Share Posted November 22, 2016 it works tested with a regular lpg tank and runs fine except that during desacceleration sometimes stalls, needs some tuning... just hope to not be overlooking something and break it later... Link to comment Share on other sites More sharing options...
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