Thread: V8 engine modifications for LPG

yep read that after i posted.
Can unichip completely control ignition timing, still in conjunction with with 3.9 dizzy arrangement? We touched on electronic control on another thread where I was asking about ignition curves. Incidentally, after some experimenting I've now disconnected the vac advance entirely (the flat spot just got annoying) but it's still plenty happy on PULP low & mid revs, I don't drive it at redline either.
I'm not that fussed if petrol performance is not ideal as long as it runs,, basically as long as it doesn't ping and carry on.
So in this regard I'd be happy to get the dizzy recurved to suit LPG & spend the cost of a unichip on the engine.

For what its worth my County has a 4.2 high comp motor with a recently (last year) fitted Crow xr3000 dizzy re curved for gas and a high energy coil. Gap is 85 thou for the plugs .That lot cost $445.00 and it is sweeeeet as
Absoloutly purrrs.
Well I gotta tell some one

Originally Posted by oldzook

yep read that after i posted.
Can unichip completely control ignition timing, still in conjunction with with 3.9 dizzy arrangement? We touched on electronic control on another thread where I was asking about ignition curves. Incidentally, after some experimenting I've now disconnected the vac advance entirely (the flat spot just got annoying) but it's still plenty happy on PULP low & mid revs, I don't drive it at redline either.
I'm not that fussed if petrol performance is not ideal as long as it runs,, basically as long as it doesn't ping and carry on.
So in this regard I'd be happy to get the dizzy recurved to suit LPG & spend the cost of a unichip on the engine.

Dan, yes it can, it can have several different Maps for fuel and Itgnition timing, as you know the standard L/R computer doesn't control ignition, only fuel, when the Unichip is fitted they remove the black box that controls ignition timing and the Unichip takes over that part as well as fuel. So the ignition can be mapped for optimal Petrol performance and when you switch over to LPG a different ignition timing map optimised for LPG is switched on and you get a much better performance outcome, speak to the mechanic at Graham Coopers in Sydney, I think his name is Wade, Regards Frank.

**** I'd be telling everyone who'd listen too. Just walk up to people in the fruitshop or the newsagent... "psstt, just tweaked my V8"

Originally Posted by Tank

PLR, may I suggest that instead of spending big money HC pistons and shaving heads, you have a UNICHIP fitted and have it Dyno tuned to run optimally on ULP and LPG. The UNICHIP will allow the Tuner to adjust fuel and IGNITION Timing to suit both fuels. The big compromise with LPG and Petrol (Dual Fuel Setups) is that timing is usually set for optimum performance on Petrol and performance on LPG falls away because of the difference in IGNITION timing required between the 2 fuels. An LPG system requires MORE initial timing advance and LESS total advance, Petrol is the opposite. When I get my LPG system installed I will be having a UNICHIP fitted, something for you to consider, Regards Frank.

G`day Frank

Yes , agree with the idea .

I was going to give an idea of what the complications of altering the ratio and work up to ignition and injection .

My engines have either needed rebuilding or with the 4.0 was new and modified for LPG .

Haven`t had the need or want to modify a good running engine .

The 3.9 i`ll do will be from bits picked up on the cheap over time as at present i don`t have a use for one .

Also have another 4.0 in a crate that needs some work ( crack behind liner ) but again no use at present .

Gotta have a interest and that`s mine

For the outdated type of LPG setup we`re discussing , not sure about Unichip though , i though it piggybacked the ECU which doesn`t have an effect on ignition but i`ve been wrong before .

Also the cost was a concern for me , i thought somewhere around $1500 but again i could be wrong .

The best way i think would be to use Vapour injection haven`t looked into it very much but the underbonnet gear and ECU to piggy ( not sure on software )

The same brand that a mob in Melb will fit for $1700 extra with a LPG fit up can be bought from another country for around $700 with an ABN plus around $200 to freight .

Haven`t been intersted enough as yet to follow it up but sometime in the future .

I`ve got some approx figures for LPG curve somewhere i think

Cheers

SVI works in conjuntion with the original ECU for injector signals & an interface had not been developed when I had LPG fitted and there comment was that with the influx of conversions making the SVI work on anything other than the latest popular models wasn't going to happen any time soon.
I also did a bit of delving into importing the basic kit, but the above was of course going to still be an issue.

Originally Posted by oldzook

SVI works in conjuntion with the original ECU for injector signals & an interface had not been developed when I had LPG fitted and there comment was that with the influx of conversions making the SVI work on anything other than the latest popular models wasn't going to happen any time soon.
I also did a bit of delving into importing the basic kit, but the above was of course going to still be an issue.

G`day Dan

Sorry i don`t understand what you mean by interface not developed ?

The LPG ECU for the vapour injection piggybacks (interfaces) the Cars Injection ECU ?

What they call Gen2 lpg uses an ECU etc

This mob in Melb fit vapour injection to both type Rovers , sequential and non , however i don`t know what happens with ignition with non .

Was it the ignition they were telling you about ?

Cheers

Originally Posted by PLR

G`day Frank

Yes , agree with the idea .

I was going to give an idea of what the complications of altering the ratio and work up to ignition and injection .

My engines have either needed rebuilding or with the 4.0 was new and modified for LPG .

Haven`t had the need or want to modify a good running engine .

The 3.9 i`ll do will be from bits picked up on the cheap over time as at present i don`t have a use for one .

Also have another 4.0 in a crate that needs some work ( crack behind liner ) but again no use at present .

Gotta have a interest and that`s mine

For the outdated type of LPG setup we`re discussing , not sure about Unichip though , i though it piggybacked the ECU which doesn`t have an effect on ignition but i`ve been wrong before .

Also the cost was a concern for me , i thought somewhere around $1500 but again i could be wrong .

The best way i think would be to use Vapour injection haven`t looked into it very much but the underbonnet gear and ECU to piggy ( not sure on software )

The same brand that a mob in Melb will fit for $1700 extra with a LPG fit up can be bought from another country for around $700 with an ABN plus around $200 to freight .

Haven`t been intersted enough as yet to follow it up but sometime in the future .

I`ve got some approx figures for LPG curve somewhere i think

Cheers

When a UNICHIP is fitted the fitter removes the L/R ignition module from the side of the distributor and the UNICHIP takes over the ignition timing, the beauty of it is that the UNICHIP allows more than one map of ignition timing, allowing for optimal LPG timing and Petrol timing, if you have a good running engine there should be no need to run higher compression for LPG performance because of seperate Timing maps with UNICHIP, best of both worlds. To get higher compression it is not wise to shave heads as described earlier in this post, High compression pistons would be the way to go, Forged pistons run bigger clearances and rattle a bit till warmed up, Cast pistons are cheaper and longer lasting, by the time you rebuild your engine it will cost around the same as a UNICHIP anyway, your choice though, Regards Frank.