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CFI to MPFI conversion with LPG

5K views 17 replies 9 participants last post by  copscatchme 
#1 ·
Hey guys,
Just looking for some help from anyone who has successfully completed a CFI to MPFI conversion with a LPG gas system on the engine. Just wondering if the fuel pump, injecctors and computers are standard, or have been tinkered with to run the gas. Also, when hooking up the new manifold, does the timing need to be played with.
 
#3 ·
all the gear would be standard, but youd need a new gas throttle body to fit the mpefi one. you also need to work out the electrical side - what hookups do you need to make on the new loom for the gas system. this is whats getting me...

id also have to move the mixer, as its where the mpefi airbox is...
 
#4 ·
Is having LPG that important too you guyz?
If performance is what you want, why not just pull that darn
gas system out and run standard fuel?

Brent
 
#5 ·
Yeh Brent, I thought about it but I have one small problem- its straight gas, not dual fuel. I don't have the petrol tank or pump- though it would be easy enough to get from a wrecker i suppose. But I do enjoy being able to fill up a tank for $20 and run the car in the city for about 350km. It get up to 450-500 if running country miles. The other problem with gas is in the summer. The temp gauge runs so hot on a hot day that the air-con, apart from having serious performance withdrawing issues, over heats the engine.
I figured that the mixer would have to be moved- me brothers car has a braquet for that so moving it wouldn't be too hard, but the trottle body I could see was different. Aside from that, wiring I hate doing, and can clearly see that it has a shit load of lose wires which would need to be matched. Would buying the whole system - gas, throttle body, mixer and manifold be worth it from a wrecker? Would they charge a shit load more for the added. $200 to $300 is well within budget but if it cost a lot more I reckon that I might just sell and get an EA series II with mpfi and start working on that.
 
#6 ·
well either way youd have to find a mechanic to do the wiring for you... i dont think theyd charge much more for the couple of gas parts required

and brent, its cool having dual fuel. the power loss isnt huge, and the cost benifet kicks ass. i can do 400KM on ~$25 of gas. id be broke if i was doing that on petrol. and if i ever need a run from the lights, just flick over to petrol (the nitros switch) and i have "normal" performance (plus a few hundred kilos of steel in the boot)... mpefi would just make for more performance on petrol i guess.
 
#7 ·
Hey guys.

In the past few weeks I have had to play around with my gas system wiring quite a bit. Basically, it is not complicated at all.

There are probably one or two wires that would need to be changed if you do a MPi conversion. A gas place would charge hardly anything to do this I’d assume.

Also, I'll second what J has said in response to the LPG systems.
 
#9 ·
OK, well this is how my gas system works. Its not an impco setup, just the average setup.

There is a wire that is connected to the gas converter, this is what controls the converter (On/Off) its a simple 12V signal.

There is another wire connected to the fuel pump relay.
Every time you turn you ignition on, the fuel pump is run for a few seconds to get the pressure up. The gas is connected to this wire so that when you are about to start your car, the converter purges, allowing gas to enter the intake.
When you start the car, the pump stays on. This also gives a constant signal to the converter.

The only difference between having the car in ULP mode, or LPG mode is whether the injectors are firing or not. In the LPG mode, the injectors are shut off, and the converter signal connected, and vice versa.


All the wiring of the gas system is identical from the CFI to the MPI, and you don't need to alter it. The only wire you will need to re-connect is the injector shut off wire.

Relocating the converter is easy. Get a mounting bracket from a mpi from the wreckers. Install it so that it is on the intake manifold side of the engine, near the washer bottle.
The copper pipe running to the converter can be bent and moved easily. Connect the signal wire to the solenoid as it was previously. Then all you need is a mixer for the mpi intake, and the pipe going to it from the converter.
Done.

It’s late, I hope this is making sense.

Ciao.
 
#10 ·
cool man, thanks for your help.

my setup has wires that hook on to the MAP sensor at the base of the connector, and also to the TPS. These hookups are on a seperate loom that plugs into the main loom which runs around the engine bay, so id have to change these over. im also unsure as to where it hooks into the injectors, as i havent seen anything under the hood. Right near the ECU there are three wires that hook into the factory loom and run to a black box under the hood with some writing on it - i forget the details, but it has a LED to set "TPS ZERO SETTING", a trimpot and some other stuff. Also, i cant start my car on gas, it always starts on petrol and the injectors switch off over 1500RPM - so it hooks into the tacho as well.

I thought the MPEFI loom runs from the fuel pump relay block, around the back of the engine, where it hooks up to the engine loom (sensors), and down into the cabin to the ECU? This is what someone (i think thegrk) mentioned when they replaced the loom. If i took it out, id sure as hell find out what the gas system hooked up to - but i wouldnt know where to replace things if the colours were different!! I presume the MAP and TPS sensors would hookup the same, just the extra injector signals to interrupt i guess.

hellofalongpost... hehe.

thanks for your help bass!

Jase
 
#17 ·
copscatchme said:
Hey guys,
Just looking for some help from anyone who has successfully completed a CFI to MPFI conversion with a LPG gas system on the engine. Just wondering if the fuel pump, injecctors and computers are standard, or have been tinkered with to run the gas. Also, when hooking up the new manifold, does the timing need to be played with.
You mention somewhere that your running straight gas. If this is the case, converting to MPEFI isn't going to do much. When your running gas, the injectors/fuel pump etc arn't used.

Basically, all a gas system needs is a throttle body, which is exactly what you have with CFI.

Ford is/has worked on a DGI (Direct Gas Injection) that does use the injectors.

Kieron
 
#18 ·
Hey Guys,
thx for the info, definately look into the wiring issue. Kieron, thx for the info- I think Bass touched on the idea that the gas works on pressure not injectors. The main reason that I want this conversion is that the noise from the engine bay is really anoying, gotta have the stereo cranked so its not as annoying. This is even at low revs, so it ain't the tranny, and the fan noise is just something we all have to put up with. My bro car is an EB with MPFI- I made sure that he found and absolute beauty- EB falcon S with extractors, 2.5 zorst, 16" FTR alloys, XR interior, dual fuel, straight body and only 220,000 on the clock for $5500, anyway- it runs a shit load quieter cept for the zorst. Also am looking into hooking up the fuel again. Its annoying living with the fear that if you run out of gas, you need a tow instead of a Jerry can.
Just another question- went to the guys at Smithy's in Bayswater looking into gas Research kit. They recommended that if you want that conversion done- you should get MPFI straight gas for the kit to have best effects. Grabbed all the info and it just appeared to be a carby which improves the air / gas mixture to improve performance. I could be mistaken, but that's another reason that I wanted it done. They quoted me $700 for the CFI to MPFI conversion.
 
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