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Unread 01-22-2014, 05:32 AM   #1
Camaro16
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1998 ZJ 
 
Join Date: Dec 2011
Location: Belfast, UK
Posts: 328
Any way to advance the timing on a 1998 4.0?

My Jeep runs on LPG - basically propane. Starts on propane, drives on it, and stops on it - no need for petrol at all.
Naturally I'd like to take advantage of it's 112 octane properties, but there isn't much point cutting the head, etc. if I can't adjust the timing to suit. And I know I can't do that via the dizzy.
A quick google brought up adjustable CPSs as a way to do it - are these available at all or is it a case of "butcher your own"?

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Unread 01-22-2014, 08:04 AM   #2
JS97ZJ
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1997 ZJ 
 
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Adjustable CPS?
Interesting concept!
As far as I know our petro burning ZJ's computers have a set parameter that it seeks out as engine conditions change. Installing chips and attempting to change distributor position (fuel timing) does nothing. The computer will adjust itself in order to get the best o2 readings.
The only way of making any difference (here in the states) is to get an after market performance PCM.
Just for the record, what kind of performance do you get with propane?
Our propane is sold here by weight and I can get propane for $0.50 /lb here in my neck of the woods.
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Unread 01-22-2014, 08:37 AM   #3
Camaro16
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I don't notice any performance difference at all, it's a new kit just fitted. Here it's half the price of gasoline and gives you roughkly the same mileage, maybe -10% mpg. I think the only trouble you might have is that I understand in the US Propane tanks have to be fitted outside the vehicle - mine is an original old kit, with a big LPG tank under the floor beside a very small gasoline tank in case you run out - all replacing the original fuel tank! So it'd satisfy the "outside the car" rule as well... a bit like this... http://www.tinleytech.co.uk/acatalog/Jeep.html
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Unread 01-22-2014, 09:17 AM   #4
1slo_camaro
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can you post pics of your setup? I am pretty damn intrigued by this. Propane is cheap as hell compared to gasoline at 3.17$/Gal
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Unread 01-22-2014, 09:42 AM   #5
Camaro16
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I'll try, at the weekend when it's light when I get home!
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Unread 01-22-2014, 10:46 AM   #6
Camaro16
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Here's a pic of your typical LPG/Gasoline tank setup, under the floor. Note that the tanks are designed to be stronger than the car chassis - so they will deform the chassis around themselves in a crash, rather than explode.



And a typical 6-cylinder setup on a jeep - you can see the injectors and the black propane hoses running to the manifold.



Here's the kit I used - http://www.tinleytech.co.uk/acatalog..._End_Only.html (6 cylinder version)

Best bit is, all you need is a laptop and you can map the fuel to your heart's content. Now I want to advance the spark, but the propane ECU doesn't control that, the PCM does - so I have 112 octane fuel and standard ignition timing!
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Unread 01-24-2014, 12:56 PM   #7
Exdecuk
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Quote:
Originally Posted by Camaro16 View Post
Here's a pic of your typical LPG/Gasoline tank setup, under the floor. Note that the tanks are designed to be stronger than the car chassis - so they will deform the chassis around themselves in a crash, rather than explode.



And a typical 6-cylinder setup on a jeep - you can see the injectors and the black propane hoses running to the manifold.



Here's the kit I used - http://www.tinleytech.co.uk/acatalog..._End_Only.html (6 cylinder version)

Best bit is, all you need is a laptop and you can map the fuel to your heart's content. Now I want to advance the spark, but the propane ECU doesn't control that, the PCM does - so I have 112 octane fuel and standard ignition timing!
Patrick

FlyinRyan can reprogram the PCM to take advantage of what you need. I was going to do this when i get round to the head, cam install. Only thing is if you ever run out of gas (LPG) running timing to take advantage of the higher octane (i thought it was 118 but have been proved wrong before) there could be some serious detination going on using our petrol reserve.

Strangely enough, i just spent all day cleaning mine up and painting it again (hammerite smooth black) and its exactly the same as the pic you posted, i was gonna take some pics tomorrow but no need now :-)
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