Omega Owners Forum
Chat Area => General Car Chat => Topic started by: miniator on 13 April 2010, 10:14:48
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Morning,
Been a while since i sold my Elite, though i will probably be back in an Omega in the next few months but with a long distance commute it will be LPG'd.
My question is though, is there a noticeable loss in power in the x30xe engine?
Have been doin research and the general consenus is 10-20%...which is a fair wack IMO. Has anyone ever dyno'd an omega before and after LPG fitment? or even just after!
Regards Dale
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With a sequential injection (SGI) LPG system the losses will be much less. In my opinion, they are not noticeable during driving.
Kevin
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some lpg services say %5 to %7..
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No loss of power whatsoever ... and if you think how the ECU works it is fairly obvious why !!
There is a difefrence in mpg however .. and it NOT because LPG is less efficient (in fact LPG has a higher calorific value) .. but because most folks don't understand how an engine ACTUALLY works ...
Engines do NOT burn a "volume" of fuel .... but a "mass" .. or weight .... (think about it .. the MAF senses the MASS of air and adds a MASS of fuel to get the correct ratio) .. but we buy our fuel by volume .. litres or gallons.
LPG is lighter than petrol so for the same volume you get fewer kilos/(pounds), so less MASS for the same volume.
That is why mpg figures are worse for LPG ... if the calculation were done on miles per KILO they would be as near as dammit identical.
IMHO the best way to compare LPG to petrol is by "pence per mile" .. and I'm saving around 10p per mile by using LPG ... from 23.28 p /mile on petrol to 14.05 p /mile on LPG.
Those figures include many miles of towing a 1600Kg caravan at just-about-legal speeds ..so I would notice any power loss.... but it doesn't happen.
HTH
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interesting entwood.
I was under the impression that although LPG has a higher RON (100 or there abouts) it has a lower energy content compared to 95 ron unleaded hence the lower power output and increased fuel burn of an engine that has been converted.
The compression must be raised in the converted engine for LPG to produce the same power.
I am however aware of what i shall save, a £1400 conversion here in NI will break even for me in 9 months.
The reason i ask about the loss of power is that my old x30xe was producing around 240bhp and was manual so went pretty well.
Ill probably be getting an auto this time (provided i like the test drive). So with running LPG and having an autobox Im concerned that the performance of the car will be effected...obviously im not expecting the pace of my old car.
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interesting entwood.
I was under the impression that although LPG has a higher RON (100 or there abouts) it has a lower energy content compared to 95 ron unleaded hence the lower power output of an engine that has been converted.
The compression must be raised in the converted engine for LPG to produce the same power.
.....
You are partly right in that, if you were designing an engine for LPG from scratch, you would run higher compression than for petrol and would probably advance the ignition timing a little. These are not easy to adjust when converting a vehicle, so there is a compromise in doing so that loses you some power and economy.
In addition, you are injecting LPG into the intake as a vapour whereas petrol is injected as a liquid. The liquid fuel takes up less volume than the vapour. This means that more volume is available to get air into the cylinder when running petrol. More air means more fuel can be burnt in each cycle of the engine which means more power. So, there is always some loss of power when running a SGI LPG injection setup versus the same engine running on petrol. As someone who runs such a setup I can say it's not a noticeable loss on the road.
A "mixer" style LPG system is much worse, because the vapour is added to the mixture much earlier in the intake and displaces more air. Anyone installing a mixer on a GM V6 is heading for trouble anyway, though, so we'll discount that.
There are liquid phase LPG injection systems around. They are in their infancy, expensive and not that reliable yet, but they do allow the engine to develop more power on LPG than on petrol because the LPG is kept as a liquid until it reaches the cylinder.
Because the LPG boils at a much lower temperature than petrol, liquid injection of LPG absorbs a lot of heat from the air as it is injected, making that more dense, so it has a kind of "charge cooling" effect.
Kevin
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thanks for that kevin, that does make more sense to me now.
Now to find the right car.... cheers
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calculating difference not that easy..
Air fuel ratio is 14.7 in ideal conditions but for lpg the ratio is 17.1 and their calorific values depends on the type of fuel and mixture of LPG ..
so the only real way is to check on dyno for some specific LPG and fuel..
in my post %5 to %7 difference is tested on dyno with a newly installed LPG set by some LPG installers (BRC) compared to 95 RON.. but imo even it can change with UK fuels.. and of course a clogged LPG filter can change the situation more than that..
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and of course a clogged LPG filter can change the situation more than that..
Fair play, Cem, your English has come on leaps and bounds ;D
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Further to James's post, How long have you been learning English, CEM?
just thinking how long we would have to study to be as proficient as you in YOUR language!!
Well Done!!
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and of course a clogged LPG filter can change the situation more than that..
Fair play, Cem, your English has come on leaps and bounds ;D
;D thanks James.. :y
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No noticable difference on mine, equal oomph on either fuel :)
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about same for me, 2.2 has limited power anyway ::)
Extra weight over the boot helps traction though, and through the twisties its noticeably more stable!
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about same for me, 2.2 has limited power anyway ::)
Extra weight over the boot helps traction though, and through the twisties its noticeably more stable!
cut 1/5 th of springs you wll see stability ;D but at the expense of horrendous comfort :-/
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about same for me, 2.2 has limited power anyway ::)
Extra weight over the boot helps traction though, and through the twisties its noticeably more stable!
cut 1/5 th of springs you wll see stability ;D but at the expense of horrendous comfort :-/
LPG is a free lowering kit, especially with a 90L tank. I really must replace the shocks as with full tank of gas, it can get a bit bouncy ::)
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about same for me, 2.2 has limited power anyway ::)
Extra weight over the boot helps traction though, and through the twisties its noticeably more stable!
cut 1/5 th of springs you wll see stability ;D but at the expense of horrendous comfort :-/
LPG is a free lowering kit, especially with a 90L tank. I really must replace the shocks as with full tank of gas, it can get a bit bouncy ::)
erm.. I mean bad comfort ;D
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I don't notice any loss of power :y :y
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calculating difference not that easy..
Air fuel ratio is 14.7 in ideal conditions but for lpg the ratio is 17.1 and their calorific values depends on the type of fuel and mixture of LPG ..
By mass, that's correct, although at maximum power you need to be running about 12.5:1 on petrol for best power (and to avoid melting things) and the same goes for LPG.
A given mass of petrol takes a much smaller volume than a similar mass of LPG vapour, though, and this is what limits the power available from a conventional SGI system.
so the only real way is to check on dyno for some specific LPG and fuel..
Agreed. I need to get my little black box out and test it on the A32 my private test track one day. It's certainly a small enough power drop that it's not noticeable when driving.
Kevin