Anyone ever converted an XC90 V8?
 

As above really.

I'm looking at getting myself one for family duties, so was wandering if it's ever been done?
Don't know how the Yamaha V8 would behave on LPG, or even where the tank would go as I've not even had a good poke around one yet.

Cheers,

Steve

They have and can be done. The do need a well specced system. Tank if you go for one in place of teh spare wheel there is not a great deal of space. You can fit a 65ltr in or a bit bigger if you add a skid plate

Even in V8 form, are you sure? It's a tart's car. A homoerotic, hairdresser's shopping trolley, come pram... all but a quick one;)

Careful now, drive it for long enough, and you suddenly find you need a bus-width to get through anywhere. I'd get rid if I were you, before it starts. Their owners all seem to struggle. Must be catching.

And don't leave it too long? You might er..

Turn.

If you're walking towards it, teapot fashion, I'm sorry.


It's probably too late.

Erm... Yeah.

Too late.

http://i1137.photobucket.com/albums/...pspvyszprq.jpg

Did you get the lpg conversion? How much did it cost and any drop in performance?

They can be done - I was looking at one on e-bay last year.

I dont think he has done it yet.

Performance should be the same on both fuels

really nice!

looks well in black.

That pram;) would look good down Old Compton St.
I'm sure Classic will correct me, only you'll always get some drop-off in torque/power simply because the gases are able to run higher compression ratios and advance over petrol. And with the engine hobbled by the fact that it needs to run petrol some of the time, you can't up the CR to the higher levels the gases would like.

Advancing the ignition when running a gas conversion offsets this but not all the way. The 'Gas of the Gods', CNG needs highest, followed by LPG. If hte engine had its valve timing, CR, and ignition without consideration to the BiFuel petrol requirement, I summise that you might actually see power increases. CNG is in many ways, and LPG to some extent, superior to petrol. For kick-off there's littel sludge creation, and no neat fuel to flush the oil down the bores and no issues with fuel atomisation and metering to gas, because it's already a gas. But the car has to be set-up for lower compression ratios etc to run petrol too.

You wouldn't drop your CR for petrol and expect no ill effect would you? Well, you're doing this with LPG, whereas any old skool boy-racer knows skimming your head is the route to cheap power.

Is gas better for yoru engine?: My engine oil back from Blackstone Labs after 28,000 miles had a report to change it at 30,000 next outing. Try that with petrol. CNG is very clean, and LPG cleaner.

With a NA engine there is some power loss. This can be evened out by using atiming advance processor to advance teh timing. Higher CR would be better but would cause issues with petrol.

Turbo engine dont have the issue

My XC70 with the 3.2 IS6 engine runs equally well on gas as it does on petrol. One feature of the Prins VSI system is that if you floor the accelerator quickly, it switches back to petrol so you're probably never going to be able to get an accurate 0-60 time to see if there is any drop in performance.

Thats a bit naff how your prins has been set. The 3.2 is not massively demanding and should not struggle on full load running on LPG

Thank you 'classic' that makes some sense to me... I think. But even with a turbo upping the charge, each cycle, it's doing that with petrol too, so because the engine has to be set-up to manage the lower octane petrol, the problem still hasn't gone away, it's just been eased? What have I missed? I'm guessing in a turbo set-up, you 'could' up the boost under LPG/CNG thus effectively upping the CR thru' other means. Do I have htis right? If so, do most cars allow you to do this?

On my NA car I do have a small drop-off, in peak power and torque, which I would expect, yet it's only noticeable if I press-on in a licence-losing style so frankly I'm not bothered.

And 'Mr Jones' has a set-up (rightly or wrongly) to negate the perceived issue. How should it be set?

The ECU retards the ignition on petrol with the boost.

You do not loose any power with LPG due to the CR as this is the same for both petrol and LPG. Yes LPG could run a higher CR and make more power. LPG does have a lower calorific value so you need to use more than you do petrol to make the same power. The fuel then takes up a bit more space causing you to loose the 1% of power. Old mixer systems loose more but not major

Thanks classic, I bow to your greater knowledge here.

Sorry to sound dim on this, so LPG has lower calorific values than petrol for a given volume. This I understood.

Apple for the teacher, help me here, I'm the sad anorak that would really like to grasp this, please, marks out of ten for the following...

1) Because we can't increase the capacity of the engine when running gas, for any given swept volume cycle of the engine, less energy is going in with LPG, so because we are forced into less energy going in, we must expect less energy out.

2) We could negate the effect of 1) by increasing the boost when running LPG by whatever proportion of energy we are short-measured. Hence if there's 5% less energy per stroke 'going in' running LPG, ideally we would up the boost by said 5% (solely on LPG, mind) and we're on a level with petrol. Because now, per cycle, we are putting the same energy in.

3) Does my point about some of the power loss is brought about due to the CR being fixed by petrol's lower CR requirement stand? In an ideal world you would up the CR when running LPG, only we can't?

4) You wroteOK, so unless this can be changed, this is another power-killer for LPG, because it may have lower calorific value, but it does like more advance. Really we would advance the ignition a tad running LPG. Do systems allow you to do this?

5) Not sure I see why. I can see that the metering will not be good, and we'll lose power becasue of this, but why would an old mixer system suffer more than proper kit in any other respect. Apart from better metering by reading the lambda etc, what is it that proper kit does that an old mixer doesn't?

6) So you do (kind of) lose more power because of the lower CR, but because you can't do a thing about that, we live with it. Or conversely you don't lose more power because of the lower CR because the ECU you install tricks up the advance and boost to get round this issue in other ways. I'd assume by Boost increase and ignition advance?

7) Am I getting my higher octane and further advance requirements remixed-up?
a) LPG needs more advance because it has a slower flame-front? Hence is slower to ignite? Correct?
b) LPG has a higher octane but it is of no advantage in a BiFuel conversion set-up because this property is hobbled. The engine can't be changed back and forth to suit each fuel?

Which bits do I have right/wrong?

In short if I have hte above about right, for there to be little or no power losses running LPG, what does a top-end install do to achieve this? Aside from more advance, or a altered advance curve, do they up the boost on gas for example?

This fairly in depth but here goes

LPG has a calorific value of 46.1 MJ/kg and petrol is 45.8 MJ/kg so in weight has a higher value. However, its energy density per volume unit of 26 MJ/L is lower than that of petrol (about 0.5–0.58 kg/L, compared to 0.71–0.77 kg/L

This means we need to put more LPG in than petrol to make the same power

1) no we are putting in practaly the same energy (what is lost is the tiny amount of air lost that is replaced with the extra fuel)

2) see above

3) As the CR is the same for petrol and LPG no power is lost.

4) It is possible with some ECU's to advance the timing or it can be done via seperate processors. The gain is so small on LPG it is rare to be done but is essential with CNG

5) The power loss with mixers systems comes from teh restriction on teh air intake introduced by the LPG mixer

6) LPG could make a fraction more power at WOT but we are only talking a small amount. Where a higher CR would really come into play would be at part throttle and would make the engine more efficient with the higher effective CR under part throttle.

7) a) LPG does not need more advance but can use it
b) either way things will be slightly comprimised for one or the fuels. Either way the CR is striking a balance between part and full throttle. Timing advance for LPG is an option to get the most of what is there but the improvemnt is so small its bearly worth it. The advance that can be used is in mid range.

With LPG the engine will work perfectly fine under all conditions as it has been set for running petrol. With CNG that is not the case, it needs a lot more advance to run correctly

Thanks classic, so CR being below what LPG likes means, power does take a hit over what it would ideally be, but it's not the major factor. What is, is the lower density which compared to petrol this either depriving hte engine of fuel or air relative to petrol.

I had not realised CNG was so different to LPG in it's requirements. Thanks.

CR is a complex thing as in most conditions regardless of fuel used drastically higher CR could be used as the cylinder is not being completly filled. It is WOT that limits how much CR can be used and is then traded off with timing.

CNG and LPG burn very differntly

I kinda grasp that CR is dependent on far more than fuel, combustion chamber shape and no least what the chamber can take with a full chrge of fuel and air. But it's been a long time since i read up on this stuff, I'm an electronics engineer, no motor tuner! I'm worried about hassling you but please a few more related Qs?

1) Am I correct is saying the reason LPG needs more advance than petrol, and CNG still more, is the slower flame-front.
2) Both are harder to ignite in the first anyway, correct?
3) But if this so, why am I told they run hotter, when I would expect cooler, or is it that once alight the flame is hotter?
4) In the ideal engine, one that only runs on one of the gases, removing any comprmises to run petrol, how would this 'ideal-engine' differ?
5) So a little bit of where I came in... no matter how much I thkweam and thweam, in three theoretical engines, Petrol; LPG; CNG, each optimised for its particular fuel, 'theoretically' we will never finish with the same power with the gas fuelled engines because no matter what else you do, the density of hte gases, means that per cycle the gas-engines will never able burn as much energy, simply because you've less room for the oxygen needed to burn it.

1) yes
2) yes
3) knowing the answer to 1 and 2 is the expert in the pub wrong? Well mostly yes he is wrong. The burn is not as hot. The engine will not run any hotter or cooler as the running temprature is controlled by the cooling system. Is the pub expert right in any way? Yes a little as LPG does not have any cooling effect or lubrication it is harder on the valves.
4) the engine would not differ much, possibly a slightly higher CR and a ignition map optimised for the fuel
5) The energy for a given volume is the limiting factor with vapour dosing. Direct liquid injection could possibly give more power than petrol but that would take some working out

Thanks 'classic' I have it now. In our three theoretical engines, petrol remains king, if by a small margin. Direct liquid injection of LPG could topple petrol's crown, however this is clearly is not an option with CNG.

So all the bullplop about higher octanes of the gases is all very well, but in practice it's not going to easily topple the issue of less energy per cycle in the first. But all this is a point of interest to me, but in the real world, entirely academic. I am glad you've cleared up the 'LPG runs hotter' point. That never made any sense.

I tell you what though, as I've said before, my Blackstone Labs test on my oil has it good for 30K. I suspect LPG is nearly as clean. Try that on petrol.

Thank you for your clarifcations.