More poke from my V8 on LPG

Hi,
I'm running my 110 V8 on Lpg. Now while it runs great on petrol, just as you would expect a V8 to, on gas its very flat.
Its running a single point system through the SU carbs. Not that i can't live with it the way it is but i've been told that i can fit a more efficient LPG set up to improve things.
I've tried to post on the LPG forum but they don't like my email address so i can't register.
Any LPG experts on here?

your abit stuffed on carbs..but you could do the obvious and service the lpg system, ie filters etc
is your power valve set up propery?
then prehaps advance the timing, there is a cheapish module from aeb that advances timing by3/6/9/12 degrees when switched to gas.
other than that you need to go mulitpoint, which you could do, but it involves also installing efi petrol system as the gas ecu is a piggy back on the petrol system..
but going efi would also help your petrol power/mpg too..so a win win situation..and its quite easy really..

the biggest single improvement is sort the timing , so it swaps when changing from one to the other as previous poster has said .

I'm pretty sure that the timing is already adjusted to work best on gas, I'm thinking this as it idles high on petrol which I took to be a symptom of advanced ignition timing.
Are there any links to converting to EFI threads?
Is there a single carb set up that is affordable (not edelbrock ) that will work better?

dont think single carb will be any better !

do you have a mixer ring on each carb?

johndregg said:

I'm pretty sure that the timing is already adjusted to work best on gas, I'm thinking this as it idles high on petrol which I took to be a symptom of advanced ignition timing.
Are there any links to converting to EFI threads?
Is there a single carb set up that is affordable (not edelbrock ) that will work better?

Click to expand...

no..its a comprimise..carbs are old fashion and crap..AS IS SINGLE POINT lpg..

re efi..ebay or friend?..buy complete efi setup..ie manifold,pipes,maf loom and ecu..cost less than 200..i sold whole lot for 100..

then 2nd hand multipoint front end for about 100 again..you have tank etc..so for about 300 ypou have efi and multipoint...efi conversion is real simple.efi is plug and play..ASSUMING you have a brain that works with electrics and nuts and bolts..THAT is not an insult..some do.some dont, some can play an insturment some cant...some can paint with oils some cant do better than matchstick men..JUST IS.

but if you can its EASYYYY

Discodad is selling an EFI set up with LPG ask him

there you go...sorted!

still a 3.5 in a 110 though..sold mine...55mph!!! joking me!!

Most LPG converted motors are set for petrol/LPG on the ignition timing, a huge amount of extra umph can be gained by setting up for LPG only and its even free to do.
My 3.5 is set on the o of before and runs like a dream, if I need to swap back to patrol its just a quick spanner job to adjust
Give it a go?

fett said:

do you have a mixer ring on each carb?

Click to expand...

Yes.

zen said:

no..its a comprimise..carbs are old fashion and crap..AS IS SINGLE POINT lpg..

re efi..ebay or friend?..buy complete efi setup..ie manifold,pipes,maf loom and ecu..cost less than 200..i sold whole lot for 100..

then 2nd hand multipoint front end for about 100 again..you have tank etc..so for about 300 ypou have efi and multipoint...efi conversion is real simple.efi is plug and play..ASSUMING you have a brain that works with electrics and nuts and bolts..THAT is not an insult..some do.some dont, some can play an insturment some cant...some can paint with oils some cant do better than matchstick men..JUST IS.

but if you can its EASYYYY

Click to expand...

I'm ok with the spanners and methodical with electrics so I'm pretty sure I could plumb that lot in, I just wasn't sure it would be worth it.

Dr_evil said:

Discodad is selling an EFI set up with LPG ask him

Click to expand...

Looked at his advert, it's a single point system on an injection motor, think I'm being advised to go multipoint here?

yes you are...but if its cheap enough. (not seen) then the efi setup is needed...YOU MUST GET EVERYTHING...loom,manifold,ecu maf etc..for a 3.5...

johndregg said:

I'm pretty sure that the timing is already adjusted to work best on gas, I'm thinking this as it idles high on petrol which I took to be a symptom of advanced ignition timing.
Are there any links to converting to EFI threads?
Is there a single carb set up that is affordable (not edelbrock ) that will work better?

Click to expand...

As suggested, you need to try more advance on gas, probably turn the dizzy about a quarter of an inch, when its right mark the dizzy and body with tipex, same on petrol , advance till it pinks under load then knock it back a tad and mark with tipex

Easy to try, advance when on gas, if idle increases then you are going the right way.

My 3.5 V8 on twin gas rings in the SU's would fly but timing needed to be advanced when turned from petrol to LPG or it was crap

If your running on gas the carbs/efi should make no difference, unless its multi point gas.

I cant comment on a 3.5 but I have a 3.9 that runs on gas through a single point controlled by a lamda sensor and it runs way better on gas than it does on petrol.

So I suppose its down to how much ££££ your going to spend to how much your going to gain.
Theres no way Id spend ££ on a multi point system as Im quite happy with the performance of my single point.

You be better to get it setup correctly before you jump in to buying stuff

Our 3.9 Thor has the same timing for gas as petrol, we don't notice a big difference in power.

Single-point is always going to be a compromise, but with care it can come close to multipoint.

The big issue with single point is getting the mixture and all the other parameters set up optimally for LPG as well as petrol.

The multipoint systems tend to use all of the controls and sensors on both gas and petrol, so your fuel trims don't swing too much from one to the other fuel.

A carburated 3.5 has none of these facilities and can only run on fixed settings I believe, so the gas mixing is vitally important to get right.

Having only run on a 3.9 Thor, I can't be more help than to say to look at the mixture and mixing, the timing should be fine as it is.

Peter

soooooooooooooooo disagree...i have 10 degree more timing at 0 bar..and 6 at .6 bar..

now those who have not tried multipoint or indeed direct liquid injection, should in my oppion keep shut...

and to those who run same timing on petrol and gas REALLY ought to try advancing on gas....the difference is large..ie 1 sec off 0-60 or 2-3 mpg..

mulipoint..no back fires..precise fueling..better safty..more power..more mpg..WHY you think mulipoint was developed??

JUST my oppion, though its correct..(lol)

Hi all
Thought I would put my 2p worth into the debate. I have a land rover 90 with 4.2 v8 on SU carbs an an open loop LPG system, I also have a range Rover L322 with a multipoint LPG injected system. The landrover 90 although open loop I have a wide band Lambda system to ensure it is always in tune, open loop systems are fine if kept in tune unfortunately they go out do tune frequently and need constant tweaking. I also have Megajolt system with 2 maps for LPG and petrol so although I have a simple LPG system I have some modern tech the get the engine running in peak performance.
The multipoint system is excelant in the range rover and you really can't tell the difference between gas and petrol, it runs an absolute dream with no tuning necessary. I have the software for the LPG system and service it myself.
I keep the simpler system on the 90 because I like the originality of the carbs and I believe that the multi point works better with the modern vehicle ECUs than the simpler ECU from hot wire system.

As I say I am no expert but as Zen says I am better ant playing with engines/ vehicles than painting or writing so any spelling errors please excuse.

Mick

I suppose I need to verify my timing before commenting further. I'll get back to you in a day or two.