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LPG

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Range Rover Blues:
I've had starting probs like that recently, they reached a peak (no pun intended) greenlaning in Derbyshire, all the stopping and starting the engine.  One of the lads I was with said 'ECUs gone'.
Swapped it for another, now the car is back to normal, and I'd been told the hot-wire ECU was pretty reliable too.  Scary thing is S/H they cost much more than the 3.5 ECU.

To get the best out of LPG you need to make compramises, here's a copy of a PM I sent to a fellow member over Christmas (to save me a lot of typing).


You didn't say what lump yours has, wether it's EFi or not but I'm surprised it runs better on Gas when cold.
Anyhow, a little technical stuff for you:
Octane rating, a measure of the fuels resistance to self-ignition, 4 star was 98 octane, 2 star was about 92, unleaded is 95 octane and therefore equivelent to 3 star!
This is the reason I think that LR revised the timing for later V8s from 6 degree BTDC to 4 deg, unleaded is more likely to pink (you probably know that).
LPG is about (depending on who you ask) 112 to 115 octane! (holy c**p batman).
LPG has a lower calorific value than petrol (less power)
LPG burns more slowly than petrol (possibly responsible for the lower calorific value!)
Now running on LPG and petrol is a compromise, an ideal LPG engine would have a compression ratio of about 12:1, you'd never get a petrol engine to start up at that and the timing would be so retarded as to make it pointless, the fuel would still be burning as it left the cylinder, and the exhaust valves would not last too long!
So to get the best from LPG in a petrol engine you have to go half and half.
Now, the cretin who owned our car last actually skimmed the cylinder heads to raise the C/R and then had to retard the timing back to 3 degrees BTDC, trouble is at high revs on petrol this isn't enough and the engine would destroy an exhaust valve in a minute or less.
So that's not the answer.
Timing, ah yes but if you advance the timing permenantly you will find it hard to start on petrol and destroy the engine damn quickly in the process, what you need is to advance the timing only when on LPG.
In fact because of the ludicrously high octane rating of LPG you can advance the timing so far that the engine produces what's known as negative work, a term more common in diesel engines, wherein the burning gas tries to stop the cylinder finishing it's compression stroke!
All this without any self-ignition.
How to achieve this, well I bought an Iwema ignition advance processor from Chris Perfect and would recommed you visit his website for further information www.chrisperfect.com.
This little box of tricks allows you to advance the timing while on gas by 1.5, 3, 4.5 or 6 degrees, with a few other little tricks up it's sleeve as well. Bad news, it's £150 plus. See how I love helping other folk's spend money.
While your at it, has anyone told you to close up your plug gaps yet, by about 3 thou. This is because LPG is so hard to ignite (high octane you see). I have just fitted a set of Iridium plugs from Chris (at £8 each) and I think they are making a difference. On the first long run after all this stuff came I saved well over a penny a mile, maybe nearer two!
Thing is the car is now misfiring again (I hope it's that plug lead I damaged while fitting the plugs and not another valve) so it's not running at it's best but I have plenty more power now and hardly notice the difference on LPG as opposed to petrol. the car sounds better at full chat too!

Hope this helps, if so you may want to copy it to a forum and get other folk's input too.

Happy new year
Andrew

muddysteve:
Seems like a can of worms this LPG business. I really love driving the V8 (so much i take it to work instead of the missus metro even though it costs me a tenner a day more  :?  ) I just like the idea of it costing sensible money to run. The chrisperfect website is very informative and i like the idea of having a LPG tank where the petrol tank goes and running on gas permanently  :shock:

Why's life never simple?  I dont mind spending decent money on a kit but dont want it to end up a white elephant  :cry:

Has anyone got any experience of running a carbed engine on LPG only?


Cheers

Steve

oooh me brain hurts  :?:

Range Rover Blues:
I don't think you can go gas only, besides, what woulfd happen if you ran out?  The problem with the UFO tank in place of your fuel tank is the £00 for a side-mounted fuel tank, oh yeah, and it's asking to be hit by something.  I'm looking into a skid for mounting a single 36L tank in with the fuel tank, having cut that in half.  All this would then be inside my tank guard.

BIG_ORANGE_90:
Could an lpg tank be made in the shape of a 110 rear tank?

Bush Tucker Man:

--- Quote from: "BIG_ORANGE_90" ---Could an lpg tank be made in the shape of a 110 rear tank?
--- End quote ---


Erm....
In one word - No.

It's a pressure vessel & needs to be a uniform shape to allow for a constant phsyical strength.

Have you ever seen a square divers oxygen tank, or Calor Gas bottle??

it would be a nice idea & allow easier fitting solutions though.

Off-hand I think it's compressed to about 2000psi?? (in order to 'liquidise' it)

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