V8 engine modifications for LPG

[100I]

I'm just planning ahead here for some more serious mods to suit LPG a little better:cool:,,

I will want to up the compression ratio - probably to around 10:1 seems appropriate without being radical as it will still be dual fuel, albeit ULP only which I don't mind. I'll also give it a more appropriate camshaft profile.

A few questions; As the rover V8 is renowned for it's longevity - likely due in part to it's low compression, low stress design - is it up to this CR in the long run or will bottom end durability suffer?
Is it simple enough to just shave the heads to achieve this? Is there enough valve to piston clearance? Especially considering the intention of fitting a high lift cam. Will I have to change pistons to achieve this? For that matter will the OE hold up to it or am I up for forged items?
My engine is only 150k young so I couldn't justify a full house rebuild yet. (SWMBO would also take some serious convincing:whistling:)
What sort of other consequences such as manifold fitment, lifters etc?

Has anybody done 'the package' to their 3.9?

Yes I know all this info is probably either somewhere on here or out there, and I have searched a bit but it's scattered and I'm as lazy as anyone else:p

[PLR]

G`day Dan

I thinks it`s probably a B suffix engine but is it A OR B suffix ?

I`ve got a 3.5 with that type ratio was 9.35 std

Also a 4.0 with similar ratio was 8.23 std

Almost have enough bit to do a 3.9 but lacking a block at present

Starting point is which 3.9 A or B suffix

Cheers

[100I]

G`day Dan

I thinks it`s probably a B suffix engine but is it A OR B suffix ?

I`ve got a 3.5 with that type ratio was 9.35 std

Also a 4.0 with similar ratio was 8.23 std

Almost have enough bit to do a 3.9 but lacking a block at present

Starting point is which 3.9 A or B suffix

Cheers
Gday Peter,

It's engine# is 38D38437C and it's currently a low comp.

So with experienec of 2 engines similar, presumeably on gas, did you find it a worthwhile exercise? Is that CR about on the money? Have you cammed them or anything else?
I don't think I could go much more on PULP could I?
Plus I read a post where JC mentioned problems with an engine of his on LPG. He had around 11-odd and found it was too much due to a change of LPG formula to a formula with dramatically reduced octane rating nowadays.

cheers

[PhilipA]

You will have big problems shaving heads to get CR, the ports will not line up with the manifold,and you will have to machine the manifold. Also you will have to machine a rocker pedestals. A lot of maths.
Everything will then be unique to your motor.
By your question you probably should not attempt this.


The best /correct way to get CR in a 3.5 is to fit HC pistons. I think you can readily get 9.75 (TVR)and maybe over 10:1 from UK as the P6B had over 10:1.
It should be all right with over 10:1 as the first engines were this when they had lots of lead.
Regards Philip A

[100I]

Thanks Phil,
yes I was afraid of that, oh well have to do it properly

[walker]

If you could keep us all filled in on how you go about it it would be appreciated. I am building a Rangie ute at the moment and once the body is finished I will start on the motor.
At the moment I have a 4.6 block with 3.5 heads on it. The ute is going to run straight gas and like you I want to up the CR to about 10:1 at least. I was going to jsut do it by getting the heads shaved but it sounds like that is not possible.

[100I]

Adam, I might be keeping an eye out for your engine build instead:D. With a house build keeping me busy there is an extremely good chance you will beat me to it if I have to go to all the effort of tearing the engine down...

Now I just had a thought, do I have to completely strip it, can it be done in-chassis?
Do the pistons clear the crank?

[rovercare]

Adam, I might be keeping an eye out for your engine build instead:D. With a house build keeping me busy there is an extremely good chance you will beat me to it if I have to go to all the effort of tearing the engine down...

Now I just had a thought, do I have to completely strip it, can it be done in-chassis?
Do the pistons clear the crank?

Why bother even building a motor if you just going to short cut it all the way:mad:

Buy yourself a dial indicator and some good instructional books on blueprinting and engine building and do the job properly

30though of the heads will not lift compression that much, you need to do the math for exact amounts, its a simple formula

[100I]

Such as? It's barely got 150k, mostly lazy highway work. As far as I can tell the engine is in very good shape, the cams aparently show wear at 200plus, what else should I do? Maybe pull the heads off anyway and get them serviced, but aside from perhaps some carboning they should be in good shape too I'd like to hope. Should the crank have any wear at this mileage?

[PhilipA]

By the way Dan, What I said about head shaving applies to an 8.35 or whatever your 97 Disco is, for BIG shaves such as the 100thou that you would need.

There is no problem with say 20-30thou, but that only gives you about .6 or .8 additional compression.
Even then I have a few problems with the gaskets all lining up. ( I have taken 50 thou off tin heads and use composite gaskets)
I have a leak at the rear valley seal, I think because the rubber split, and its a dog of a job for a small oil leak, so I have deferred it.
Regards Philip A

[PLR]

G`day Dan

Yep or C suffix , all i was trying to do was work out what you have and yep the engines are for gas .

The heads you have are the smaller combustion chambers and also have the stem seals that fit onto the top of the guides .

The stem guides are longer on these heads ( outside the port ) and the valve/piston clearance is less of a concern than the spring retainer fouling the top of the stem guide

But only when using a high lift cam , the earlier heads , eg ERC 0216 used on early EFI and later carby engines are able to take more lift without modification .

The heads can be machined to raise the ratio , for the inlet manifold fitting , the heads are machined again on the port face .

There`s a formula to work out how much need to come off the port face from the amount taken off the head surface so the manifold will fit as normal .

Because the heads sit lower the rocker pedestals will probably need shims but again a formula to work out how much .

So it can be done and the math is there to get it right .


The best and easiest way to raise compression is with pistons but they need to be got at the right price or not economical . ( i got a high comp 3.9 set for $100 so for me it is )

I could go on for pages but i`ll just put some stuff , lpg/ratio related.

LPG produces more heat than petrol and raising the ratio also produces more heat than std .

EFI need to run within a specific heat range to work properly not as important on carby

In theory the difference 8:1 and 10:1 is little although there is a measureable increase in economy/power till it`s too high .

Below 8:1 the difference is large .

In practice the difference between 8:1 and 10:1 is/could be noticeable . ( about 10/15kph over the top of a local hill )

The ratio has to be physically measured to use the math to get the ratio of any specific engine . ( meaning your 3.9 will be similar to my 3.9 but not the same )

A general idea can be got from factory figures but the physical figures will often not tally with them .

As far as is it worth while i don`t have a comparison because gas and high comp came together with the 3.5 and the 4.0 was done for lpg from new and petrols there but not used much .

I intend to do it to a 3.9 as well if that means anything .

The same heads used on each engine , stainless in/ex valves Kline guides , a little above std lift but little .

I won`t say how much was removed from the heads but the combustion chambers are a bit smaller than the 28cc later heads .

On the 4.0 more metal was removed and it`s been 3 or 4 yrs ( i think ) but did replace the thicker 10 bolt comp gaskets with thin 14 bolt comp gaskets couple of month back and haven`t worked out the ratio but it`s possibly higher than needed .

Don`t know if i`ve actually answered anything or just rambled .

Cheers

[100I]

G`day Dan

Yep or C suffix , all i was trying to do was work out what you have and yep the engines are for gas .

The heads you have are the smaller combustion chambers and also have the stem seals that fit onto the top of the guides .

The stem guides are longer on these heads ( outside the port ) and the valve/piston clearance is less of a concern than the spring retainer fouling the top of the stem guide

But only when using a high lift cam , the earlier heads , eg ERC 0216 used on early EFI and later carby engines are able to take more lift without modification .

The heads can be machined to raise the ratio , for the inlet manifold fitting , the heads are machined again on the port face .

There`s a formula to work out how much need to come off the port face from the amount taken off the head surface so the manifold will fit as normal .

Because the heads sit lower the rocker pedestals will probably need shims but again a formula to work out how much .

So it can be done and the math is there to get it right .


The best and easiest way to raise compression is with pistons but they need to be got at the right price or not economical . ( i got a high comp 3.9 set for $100 so for me it is )

I could go on for pages but i`ll just put some stuff , lpg/ratio related.

LPG produces more heat than petrol and raising the ratio also produces more heat than std .

EFI need to run within a specific heat range to work properly not as important on carby

In theory the difference 8:1 and 10:1 is little although there is a measureable increase in economy/power till it`s too high .

Below 8:1 the difference is large .

In practice the difference between 8:1 and 10:1 is/could be noticeable . ( about 10/15kph over the top of a local hill )

The ratio has to be physically measured to use the math to get the ratio of any specific engine . ( meaning your 3.9 will be similar to my 3.9 but not the same )

A general idea can be got from factory figures but the physical figures will often not tally with them .

As far as is it worth while i don`t have a comparison because gas and high comp came together with the 3.5 and the 4.0 was done for lpg from new and petrols there but not used much .

I intend to do it to a 3.9 as well if that means anything .

The same heads used on each engine , stainless in/ex valves Kline guides , a little above std lift but little .

I won`t say how much was removed from the heads but the combustion chambers are a bit smaller than the 28cc later heads .

On the 4.0 more metal was removed and it`s been 3 or 4 yrs ( i think ) but did replace the thicker 10 bolt comp gaskets with thin 14 bolt comp gaskets couple of month back and haven`t worked out the ratio but it`s possibly higher than needed .

Don`t know if i`ve actually answered anything or just rambled .

Cheers
Not at all Peter, very informative as usual, and ties in with rovercares advice of blueprinting it rather than just wacking some new slugs in and not neccesarily getting a result.
With a smaller 4cyl engine I've no doubt at 150k it would be tired and want the works, but at the other end of the spectrum I've heard it's not uncommon for large engines in truck or earthmoving equipment to only receive as much as neccesary, say only one piston replaced if damaged. I thought these would fall somewhere in between and the major components like crank & liners etc would be good for well over 300k at least.

Phil, yes mine's not even a high comp to start with so I was afraid it would be a heck of a lot of metal off, with all the knock on effects.

[PAT303]

What do you want.To build an engine to get more go or LPG compatible?The standard v8 will run just fine on both so why not save time and a lot of money by just porting the head and a new cam,maybe exhaust and drive it.The v8 is very keen when performance mods are used.I don't think the work and money involved justifies the work you want. Pat

[PLR]

G`day Dan

Just read mine and the hill is a comparison .

The difference was with the 3.5 i fitted Felpro composite gaskets which are around the same thickness as 10 bolt factory composite gaskets 3.9/4.0/4.6 .

By removing the tin gaskets and fitting Felpro the ratio was lowered and the 10/15 kph over the hill was the outcome .

My heads are only any use on my engine by machining them the way they are , they are only any good to raise comp and useless else where .

I only have experence with taking big bits off pre 10 bolt heads and know it can be done .

With later 10 bolt heads ( as yours ) i don`t know what the outcome would be taking big chunks off .

The 10 bolt heads are a different casting as well as method to 14 bolt heads .

In my case for a 3.9 i intend to use 9.35 pistons , 10 bolt heads and the thin 14 bolt comp gaskets .

I haven`t looked too closely yet but it will come out around 10 this way maybe a bit more .

Yep your right , a cared for 3.5 bottom will do many many klms as will a cared for 3.9 .

The 4.0 bottom has yet to really prove its self and being a totally different bottom than either the 3.5 or 3.9 , time will tell .

Cheers

[100I]

Well, something in between was what I had in mind.
Like I say, I can't justify the works as such.
I don't need a tyre shredding crate motor (I have neither the funds, time, shed space or enthusiasm), but being on LPG by upping the compression I was envisaging a little better efficiency both performance & economy wise. I'm not talking a radical cam job either of course, just what's commonly called a torque cam or an economy cam. Again I'm not an expert but I was of the belief this is just basically higher lift but essentially no change to duration.
If these engines do respond well to porting and a cam, and that is a cheaper & easier way to get the same result, then I'm certainly open to that.

[100I]

G`day Dan

Just read mine and the hill is a comparison .

The difference was with the 3.5 i fitted Felpro composite gaskets which are around the same thickness as 10 bolt factory composite gaskets 3.9/4.0/4.6 .

By removing the tin gaskets and fitting Felpro the ratio was lowered and the 10/15 kph over the hill was the outcome .

My heads are only any use on my engine by machining them the way they are , they are only any good to raise comp and useless else where .

I only have experence with taking big bits off pre 10 bolt heads and know it can be done .

With later 10 bolt heads ( as yours ) i don`t know what the outcome would be taking big chunks off .

The 10 bolt heads are a different casting as well as method to 14 bolt heads .

In my case for a 3.9 i intend to use 9.35 pistons , 10 bolt heads and the thin 14 bolt comp gaskets .

I haven`t looked too closely yet but it will come out around 10 this way maybe a bit more .

Yep your right , a cared for 3.5 bottom will do many many klms as will a cared for 3.9 .

The 4.0 bottom has yet to really prove its self and being a totally different bottom than either the 3.5 or 3.9 , time will tell .

Cheers
Ok, conversely, can the 3.9 be fitted with tin gaskets for the opposite effect? Perhaps in conjunction with some mild head work etc as above this would probably give that little bit I want. I was all set to give it an exhaust when I bought it as I had driven a few older RRC and one in particular with just a 350 holley and exhaust went a hell of a lot better off the bottom. But then I heard & read that headers do diddly for a 3.9 and I do not want an annoyingly loud tail pipe for minimal gains.

[Utemad]

What about computer mods?

[PLR]

Ok, conversely, can the 3.9 be fitted with tin gaskets for the opposite effect? Perhaps in conjunction with some mild head work etc as above this would probably give that little bit I want. I was all set to give it an exhaust when I bought it as I had driven a few older RRC and one in particular with just a 350 holley and exhaust went a hell of a lot better off the bottom. But then I heard & read that headers do diddly for a 3.9 and I do not want an annoyingly loud tail pipe for minimal gains.

Yes the tin gaskets can be used although the 14 bolt comp gaskets wouldn`t be alot thicker .

It had to get a measurement from them as they tend to self-destruct when the head comes off .

Possibly with a tin gasket the torque to yeild head bolts ( as yours ) wouldn`t be required and cheaper ordinary head bolts could be used .

Our 4.0 uses ordinary bolts but part of the reason for the change of head gaskets , mentioned earlier was because i don`t think the ordinary bolts exert as much pressure as the yeild bolts .

Another theory on the yeild bolts is they can be part responsible for liner shift in 3.9/4.0/4.6 because it is put forward that because of the extra pressure they evert .

They can distort the alloy around the liner which can cause the cracks in the block which allows the liner to shift .

For mine this is much more feasable theory than the pourous block theory but i undestand many like the sound of pourous block .

The headers/extractors on ours , made a big difference midrange on the 3.5 replacing std carb single manifolds .

The 4.0 has only ever had them so don`t know .

Cams are a science by themselves , i have limited infomation on them .

I get them when needed from a place that machines them , i`m sure the off the shelf ones work well but cost more than i`m prepared to pay .( last one $180 3or4yrs ago add $100 for a shelfer then )


I`ll stop now before i go on

Cheers

[Tank]

G`day Dan

Just read mine and the hill is a comparison .

The difference was with the 3.5 i fitted Felpro composite gaskets which are around the same thickness as 10 bolt factory composite gaskets 3.9/4.0/4.6 .

By removing the tin gaskets and fitting Felpro the ratio was lowered and the 10/15 kph over the hill was the outcome .

My heads are only any use on my engine by machining them the way they are , they are only any good to raise comp and useless else where .

I only have experence with taking big bits off pre 10 bolt heads and know it can be done .

With later 10 bolt heads ( as yours ) i don`t know what the outcome would be taking big chunks off .

The 10 bolt heads are a different casting as well as method to 14 bolt heads .

In my case for a 3.9 i intend to use 9.35 pistons , 10 bolt heads and the thin 14 bolt comp gaskets .

I haven`t looked too closely yet but it will come out around 10 this way maybe a bit more .

Yep your right , a cared for 3.5 bottom will do many many klms as will a cared for 3.9 .

The 4.0 bottom has yet to really prove its self and being a totally different bottom than either the 3.5 or 3.9 , time will tell .

Cheers
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.

[100I]

Utemad, save for idle speed etc, I think the computer is next to redundant in our engines when running a conventional convertor & mixer. Unless you mean SVI systems or http://www.gore-research.com.au/

I think what I'm seeking is to basically get it breathing & burning the LPG properly and just generally optimise the suck squeeze bang blow.

[Utemad]

Utemad, save for idle speed etc, I think the computer is next to redundant in our engines when running a conventional convertor & mixer. Unless you mean SVI systems or http://www.gore-research.com.au/

I think what I'm seeking is to basically get it breathing & burning the LPG properly and just generally optimise the suck squeeze bang blow.

I was talking more along the lines of what Tank said. Although my petrol only D1 computer has had something done to it by the Davis mob in Sydney before I bought it.

[100I]

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.

[DeeJay]

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:cool:
Absoloutly purrrs.
Well I gotta tell some one:)

[Tank]

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.

[100I]

:lol2:

**** 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"
:burnrubber:

[PLR]

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

[100I]

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.

[PLR]

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

[Tank]

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.

[PLR]

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.

Thanks Frank ,

As said i didn`t know also was typing when you posted your first explaination , don`t doubt what you say just didn`t see it .

" Not wise to shave heads as described " which description and why ?

I`m always happy to learn the reasons for doing or not doing something .

I`m interested in learning anyone ideas as to why and for no other reason than to understand .

Do you have an idea what a Unichip costs ?

Cheers

[100I]

I don't know exactly how it works in detail, it's part of their secret I guess. 12mths ago I could not find anyone in Brissy with a good enough working knowledge of anything at all to do with SVI, so I gave up looking & waiting in the end & chose a regular system.
Basically you can't fit SVI to any car you please just yet, only select vehicles so far but the list is growing.

Not sure if it was piggybacking or not.
What I managed to glean & the way it was explained to me at the time was the vapour injectors mimiced the original EFI (I gather using appropriate resistance values to make sure the ECU still 'thought' it was operating the petrol injectors) and it's this 'interface' that has to be specced for each vehicle's/manufacturer's ECU. What other differences between ECUs someone with EFI background might know. Whether directly operated by ECU or detoured via a piggybacked chip I don't know.
There was no mention of remapping ignition and such though so presumeably it just used the factory mapping, ignition curve and knock sensors in the usual way (and of course mine has none).

There were/are several SVI systems available or being developed in Europe tho so I'm sure some are more complex & adaptive - perhaps along the lines of a unichip style piggyback & injector 'mimic' all in one, which would be logical.

If I did understand it more I bet I'd be making a few dollars right about now:wasntme:

[Tank]

Thanks Frank ,

As said i didn`t know also was typing when you posted your first explaination , don`t doubt what you say just didn`t see it .

" Not wise to shave heads as described " which description and why ?

I`m always happy to learn the reasons for doing or not doing something .

I`m interested in learning anyone ideas as to why and for no other reason than to understand .

Do you have an idea what a Unichip costs ?

Cheers
Because of the V8 configuration with an inlet manifold seated between the heads the height of the heads i s crucial because the inlet manifold has 3 surfaces, if you shave a large amount off the head surfaces, that brings the heads lower on the block and the 3 surfaces of the manifold have to be machined to match the surfaces they seat on. It also creates the problem of your rocker arms being closer (by the amount shaved off the heads) to the pushrods, which is akin to having longer pushrods so adjustments need to be made to accomodate.
Coopers in Sydney supplied and fitted a UNICHIP and Dyno-Tuned my previous Disco, which was not fitted with LPG, for $1500, it would something to think about if you dont want to rebuild your engine, Regards Frank.

[PLR]

G`day Dan

Yes , it`s hard to unfurl this is some of what i`ve found and part what i think but haven`t looked at ignition .

There are things called Emulators , what the do is tell the ECU the injectors are still working as normal .

They wire into the injector circuit .

On D2 and P38a they are required because the warning bells and whistles will show .

On a D1 they can be used but are not really needed ( though it may be a requirement for the ECU signal ) as in the way yours works now .

The LPG ECU piggybacks the EFI ECU , takes the signal from the EFI ECU and uses this to tell the LPG ECU when to open and close ( time ) the lpg injection .

The LPG ECU then uses the signal to alter the time of opening for LPG injection which is different to EFI injection .

Basically the Emulator fools the EFI ECU into thinking things are as normal .

The LPG ECU parasites the EFI ECU to use its signal and alters it for LPG .

On a D1 same applies but less work for the LPG ECU because of the simpler system .

The ignition , i`m not sure , don`t know if the GEMS or BOSCH have the range but in theory the knock sensors are supposed to alter timing for max before pings happen and are supposed to be able to run different grades of petrol .

The D1 because of the Dissy woulds still need more work though it may be that the LPG ECU can and does have the capacity for both ignitions

Cheers

[PLR]

Thanks Frank

I misunderstood your meaning of not wise , i thought you may have meant detrimental to the engine .

I have learnt something from the discussion though .

The 4.0 had an oil leak at the front of the engine which was a split end seal for the inlet gasket .

I torqued to spec and because of the head mods and after reading your post it dawn that clearence was possibly the reason .

On refitting i used less tension and it hasn`t leaked since but your post help to finalise the leak cause .

The Rover inlet manifolds are different to most V8s like Ford GM etc .

They only have 2 surfaces and the gasket seals the valley not the actual manifold .

To make the inlet manifold fit the heads are machined on the port surfaces and the inlet manifold is left untouched .

To raise the compression this way the scenario would be a dual fuel Disco taht has sticky valves ( common because they run rich ) .

Having a preference for LPG , while the heads are off the decision is made to raise the comp ratio .

Most of the cost will be as usual , the extra will be some more machining on the heads ,the cost of shims and alot more time to do it properly .

This will workout much more cost effective than fitting new pistons etc and will acheive a similar outcome .

I wouldn`t recommend anyone does it this way , there is alot of measuring not only dial and mic etc but ccing piston tops and chambers and as you say the rockers not only need lifting they have to run in the right place on the valve stem end for extended life and it`s time consuming .

It`s for sure a do it your self job it would be very expencive to pay to have the work done other than the machining of the heads which needs an engineer of coarse .

In my case i can do it pay for machining and it does work but i also understand what your saying .

Cheers