Regarding the use of LPG in turbo diesel engines, I think there are three reasons for it to be done. Not that I'm likely to do it at this stage.

1) Improve turbo spoolup: Add LPG to increase exhaust temperatures and thus the energy and volume of the exhaust gases. Don't know if this is even possible as off-boost we're in a N/A situation and I don't know if relatively small amount of LPG will yield any useful result. Also, unless one's got a hybrid turbo, it's unlikely to be a problem.

2) Improve economy: I haven't seen any case studies but there MUST be some available given that this stuff is used in the haulage industry. That it can improve economy seems generally accepted though.

3) Improve power: Add relatively lots of LPG on WOT to improve maximum power through increased cylinder temperatures and pressures.

4) OK, so 4, not 3. Adding LPG post-turbo, pre-intercooler on the inlet side. If it's cold, it will have an extra intercooling effect, even as a gas.

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If one wanted to achieve more than one of the above benefits, I think the only real way to do it would be through a mapped system. Adding LPG in relation to the perceived state of the engine. Doesn't need to be too fancy but I think it need s to be 3D.

With LPG being additional fuel, plus the likelihood that a remapped car runs richer at the top end, merely adding lots of LPG is likely to result in more smoke, not less. There's a finite amount of O2 in the cylinder and the LPG is likely to want its share. So running with LPG would require the diesel injection to reduced. This in itself yields a benefit though, assuming the duration is reduced as late diesel injection can be a major contributor to smoking.

Disclaimer: I'm not an expert and as I stated above, I'm not plannignt o do this. However, it is an interesting subject and I've been following whatever threads and info. has been available.

J.

Jason (devonutopia) has done it and will no doubt, be along later to answer all of your questions.

However, his can does seem to have had a few issues since th esystem was installed.

Jason (devonutopia) has done it and will no doubt, be along later to answer all of your questions.

Were there any questions in his post?

Chris

Were there any questions in his post?

Chris

:rofl:

OK, I've actually read it now. A quick glance through it and I though "Our resident LPG/Derv expert will know all about that"

Temps don't necesarily go up, they may even go down.

More power - yes

Better fuel economy - about 10mpg on derv better in my experience (had it on for a good 5k miles now).

Problems - none

Mine is different from Jason's in that it's the UK Powershot, which is called Powershot 2000. Although similar it's not identical in behaviour.

Power delivery is very smooth, on mine it's set to very low levels of propane injection.

Yeah, mine's a little different in that UK systems appear to be linked to the throttle settings, so there is a degree of electronics involved, Whereas mine is from the States and is purely mechanical. It works solely off a T piece in my boost gauge pipework, and the lpg is regulated by the PSI boost pressure through 2 regulator. Starts injecting around 3 PSI and the amount of injection increases as boost rises.

My main issue at the moment with it appears to be due to the fact my car is so highly tuned as it is. I have a fixed amount of air / fuel mixture, and the lpg has merely added more to the fuel side of things (even though it is injected in vaporised gas form) So my smoke issue has not gone away, in fact sometimes it is even worse. So for full use of lpg, I believe you either need a standard car where there is room for more fuelling, or have a tuned car with a big turbo capable of flowing more air.

I'm currently looking to replace my vnt20 based hybrid turbo with something that will do just this. Big compressor wheel should mean a greater flow of air at the same boost pressures I get now, therefore giving me more power (and the extra air will help with combustion of the extra fuel the lpg is adding to the mix)

I have to say I'm happy with the economy at the moment. I assumed with the lpg being totally disconnected from the electronics of the engine, that the fuelling of the diesel would not alter, but somehow I think it has realised that there is some strange alien fuel being added into the engine, and it has cut back the diesel a bit. Quite easily get mid 50s on a long journey, and usually get high 50s on my 40mph dawdle to work along the coast. Before I fitted the lpg and started using Millers diesel power plus I was lucky to be getting mid 40s.

The system only cost me around £550 compared to the UK £1200+vat fitted. That was about £250 for the unused powershot system, imported by someone else, £250 for the doughnut tank and pipework, then another £50 for a gauge, LED level bit for my dashboard, and some bits and bobs.

I think the fuel economy side of things is caused by the LPG improving the efficiency when you're on a fairly light level of boost, it gives a bit more torque etc so to stay at a particular speed less derv is required.

Theory as regards the smoke - pretty much the same between the UK & US system, i.e. it's already effectively overfuelling with diesel so there just isn't anything the LPG will add to that, if nothing else the LPG will burn = use some oxygen = more derv left over = more smoke.

However when you're being 'fairly smooth' on the go-pedal the smoke appears to be reduced on mine.

Fuel economy for me sure is a big plus, less frequent filling up on the derv, and LPG is about a tenner or thereabouts most of the time.

oh yeah. the only visible smoke on mine that I see is on 75% to 100% wot. thing is there's not really any extra power there due to it just smoking, so I can make decent fast progress on perhaps 210bhp, by just using 75% throttle. It can be frustrating to boot it at 75% and get nothing but black smoke out the back and only a "bit" more power... :(

Temps don't necesarily go up' date=' they may even go down.

[/quote']

Got any info. on the temperature situation. I assumed adding something that burns hotter would increase the temperatures. Within the cylinder, I'm fairly sure it does. I'd be astonished (but possibly wiser) if it didn't.

Where is the gas introduced on your systems? Is it pre-turbo or afterwards?

J.

Pre-turbo, IIRC that side of things is in common between the UK/US system.

This page is quite handy I think:

clicky

Relevant section on the EGT:

LPG promotes more complete combustion, so some of the heat that used to escape through the exhaust pipe is now being converted into mechanical power and transferred to the wheels

In reality I reckon the EGT probably goes up when you are flooring it hard.

It ignites at a higher starting temperature, but it's caloric (sp?) value is lower than derv IIRC so that may be another reason.

"plannignt" - cripes! Must have had a harder day in work than I thought

I think at higher RPMs the EGT will rise due to insufficient time for the burn... which is why diesels are crap at higher revs anyway. Though it's not inconceivable that diesel "can" work work spark ignition. As long as the temperatures are high enough, the mixture can be lit off.

Just drank a King Cobra, going to have to sign off now...

J.

I reckon the perfect system would be one much like used on some lorry (turbo)diesels. There are some out there which have an ECU to control the propane injection. It is used to give the same torque/power (to avoid damaging gearbox/clutch etc) at reduced derv use.

For the kind of use Jason & I are after, a little extra power is not the biggest problem

I think the ideal combo is to have the amount of propane flow 'capped' when there is nothing left to burn, and you may well be right on 'not enough time to burn' as well. Mine is currently still set as it was delivered, I'm pretty sure it could be set to cut in lower and have a little more propane going in.

Gonna have to get mine custom mapped soon, it's definitely not making the most out of the equipment fitted at the moment :(

I think rather than having the lpg capped, simply supply more air to burn it all.

I think rather than having the lpg capped, simply supply more air to burn it all.

Not NOS too

I'd say combining NOS, LPG & derv would sound like the way to 'boom'

Some kinda CAI or (even bigger) turbo should work though

In my case I'm gonna try to shield the bits that I want to keep cool (air box, intake stuff generally post FMIC) and try to insulate some of the hotter parts under the bonnet to get the heat out via the exhaust.

Mine only has a generic map so it's definitely not making the most of the LPG, will have to remap it with LPG in mind to get best performance without laying down a smoke screen that would get the local police too interested

Some kinda CAI or (even bigger) turbo should work though

oooh, yeah. Just hope progress is made quickly on this and it might be possibly in for Trax and Czech trip.