LPG. Bollocks or a great idea?
Turbo Mini Forums

Rather than actually getting off my arse and putting a new radius arm on and the engine back in, I'd rather sit here and share some thoughts. Running LPG.

LPG is for gays who have realised that their V8 range rover is actually a rich persons car in more ways than one. You take a cut in performance at best. You actually take a horsepower cut and use more litres of lpg, even though it's cheaper.......

The snag is duel fuel systems. You have to compromise. You lose optimal power output by having to ensure that the compression ratio is low enough to prevent detonation with petrol, and probably 95 octane petrol at that... So, what if you didn't need to run petrol? What would it be like?

A bit of detail is calorific value versus octane rating allowing more advance<>torque. So, your petrol burns hot, allows you to expand your gases and produce so-so power. You're limited by the octane. LPG has a much higher octane and slightly less calorific value, so you can run a higher cr for a given boost.

How much? I hear you cry. Well, about 15:1 which is enough to make the mini just about impossible to start on a starter motor. (I have a mate who ran a 14.5:1 Cr on an 850 mini racer in the 60's and they had to tow start it). It would be different with boost as you could start the engine and actually turn it before your turbo wound up. You could wind it up seriously.

I'm not sure how much, but running LPG only would allow some serious boost...... Or, think of it this way..... No mega dished pistons, no superduper cylinder head, no decompression plate. Just whack it on and go for it.

Looking at the price of fuel and realising that mine does about 14/G, it's perhaps worth a consider.....

I wonder if any of you lot have considered it in more than just an idea detail......

Anyone run a gas mini?

Bugger off, I'm getting there.

ask wolfie if its any good......

would have thought you would need ,a mordern mapped fuel injected car to put gas on , but then again i know nought

Everyone knows that instructions only have to be read if the thing doesn't work....

A guy i work with has an astra 1.6 with LPG Fitted from factory. He says its great, alot lot lot cheaper than petrol and im sure he says he fills it every 3-4 weeks which costs him about £20

1/4 Mile 14.3secs 96Mph Terminal 10psi of boost.


Fibreglass Parts? - http://www.tdkracing.co.uk/
Split Rims? - http://www.force-racing.co.uk/

I think Robert is running LPG in his Mini.

http://www.turbominis.co.uk/forums/index.p...id=222255&fr=25

Edited by Rob H on 9th Jul, 2008.

I think you're right about the metering mm. I wonder how the more simple systems work. I wouldn't be doing it for cheapness, I was more concerned about how I could stick my blower on my N/A engine and get away with it. I sold my LowCr engine. I haven't read my books for a while, but IIRC, the relationship between boost/det is linear.

Let's say (v roughly) you need to drop 1 unit of CR for 5PSI. Obviously, starting with my 11:1 engine and effectively running fuel which will cope with 15:1. According to my rough as fark calculation, that would allow 20psi of boost on LPG, or tolerate my 12.5Psi blower pulley rig.

My engine is going back in in the next few days and it would be good to sling the blower back on. I don't really want bits of piston wrecking my nice gearbox.....

I'll see if I can get some more info about what bits would be needed....

Bugger off, I'm getting there.

Raising the compression ratio increases the efficiency of the engine

The efficiency is equal to the one minus one above compression ratio to the power of gamma minus one. Gamma is about 1.4.

You get about 60% for 10:1 and 66% for 15:1. So you get a 10% increase in efficiency.

The calorific value of the LPG is about 10% less than petrol.

quod erat demonstrandum

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

(this is totally OTT)

Since we are dealing with LPG and not GPG, it might be possible to dope the fuel with something to bring the calorific value up a bit without influencing the octane number that much. There are quite a few chemicals for the job.

It would conveniently place your engine able to run methanol/nitromethane as well. (assuming the thing is geared for an engine about 2.5L).

The increased efficiency might offset the lack of benefit due to the lack of calorific value. However, you would be able to run quite high boosts. I reckon for those of you with seriously low compressions, as well as the added colling effect from the evaporating gas, it would be possible to run very high boosts indeed.

I assume there is something about it somewhere. In a mini magazine of several years ago, there was an aussie guy who ran a mini on gas and a lysholm blower. His was an economy car IIRC.

I think it might be more easy than you think... (ish)

Bugger off, I'm getting there.

Don't over estimate the benefits of cooling by the gas evaporating.

As it evapourates it displaces the oxygen it needs to burn.

Having said that, detonation is not caused by cylinder pressure but by temperature. So if you can cool the charge without dsplacing the air, you are on to something.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Having said, increased pressure would hinder evaporation.

Curious about detonation. I would have thought it was due to the "flammability" of the stuff. If you jack the pressure up, the heat goes up accordingly, hence it goes off. I suppose if you remove as much heat to start with with, when you compress it, the whole lot doesn't go over critical pressure/temp. I'd rather use "density of heat".

I suppose if you had a problem with evaporated gas displacing air, you could do something like have a hydrogen peroxide injector.... but there are probably laws against that

Bugger off, I'm getting there.

my car is very economical on a run, you have a little less power though

Can you give us a rundown how it's rigged and how it's optimised for LPG?

I'm pretty serious about doing this. I have a 12HF01 MG engine 10.2CR and if I whack my blower on it, I'll be able to post it 12.5psi. That would be different to either turning a new pulley or having to sculpt a head.

Bugger off, I'm getting there.

no idea bud i bought it like it

all i know is it costs £20 to fill up and i get about 230-250 miles from a tank

Hi,
I'm looking into this as firmware with full table switching is available for my ECU. :)
Don't know where I'll put the gas tank though!
Cheers,
Gavin. :)

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My Mini build diary

stu , im running my van on lpg , and no petrol , it was built to run this way , it puts out 133 bhp as opposed to what i think would have been 150 odd ,so its dropped 17bhp.
economy wize , could only manage a 10.5 to one cr ,so its at about 23 worst and 35 best id say generally 27 on short trips . the cam is not the best for economy , i think it would be 25/39 on petrol .
i have a 90 litre tank so usable capacity 72 litres ,,range varies from340 to about 500 depending on use .

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

This is good stuff. Can you shed any light on what the gubbins is? I'm aware of my webers, su's and FI but the hardware for gas is vague.

This is sounding like a goer

Bugger off, I'm getting there.

How do you intend getting the gas, into the engine ??

If injection, will the cylinder charge robbing still occur ??

For big boost and gas, you lose out on the cooling effect of injecting finely atomised fuel into the airstream ( either carb or injection )

Charge temp sensors wont pick that up as normally they arent situated to read it, but it will happen.

just some points to consider perhaps ??

But LPG will be the way forward in the short term I think given petrol prices. Although it wont last once everyone starts using it.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Hi,
LPG gubbins consists of the vapouriser, this has hot water from the engine running through it to stop it freezing up. The shut off solenoid is usually attached the this.
The now vapourised gas goes into engine by either single or multipoint injection. The single is a continuous spray (I think) whereas multipoint is solenoid injectors ala EFi...
Cheers,
Gavin :)

VEMs Authorised Installer / Re-seller. K head kits now available!

WB/EGT gauges. Click here for customers write-up

Visit www.doyouneedabrain.co.uk

My Mini build diary

I will be going SPI then.

This is just a "throw the mini on the road for the summer" rather than a "do it properly".

Sadly I have just spunked £3K buggering around in Australia and the proper build is on hold......

Bugger off, I'm getting there.

yes gavs right , theres a ring in the inlet ,42mm on mine ,recommended for thie kit was a 32mm ring ,but that was tooo restrictive ,it has a row of holes in the venturi part of the ring ,and the gas going in cos of the ventrui vacuum . its v simple .

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

http://www.flexdi.com/

Looks interesting. (the vid link). I didn't bother watching all of it, but I assume the CR is controlled by boost, so if you want to give it major beans, you put avgas in and the computer jiggery pokery optimises everything for huge hp, or is it a 70mpg job.....hmmmm.

Tell me more about this ring, does the kit have a name so I can have a peer... Have you got any photos? I'm going to ideally get as much secondhand stuff as possible and just lash it up. I'll probably go suck through and just remove the bosses of the valve guides and open the exhaust ports up a little.

Any direction would be hugely appreciated. Cheers

Bugger off, I'm getting there.

Hi,
It's a gas ring LOL!
Ebay is a good place for LPG kits and pics
Cheers,
Gavin :)

VEMs Authorised Installer / Re-seller. K head kits now available!

WB/EGT gauges. Click here for customers write-up

Visit www.doyouneedabrain.co.uk

My Mini build diary

bear in mind stu , if you go suck through you have a inlet and turbo and maybe intercooler full of a very explosive mixture ... let me know how it goes ?

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

You never suck through an intercooler. Mine is basically a V-max setup. Blower on a log manifold (that's the way I'll rig it). A blow off valve would do. Just something to take the edge off it if it does flash back. I wouldn't bother with a burst plate or anything which buggers it like that.

This will be a disgraceful bodge up, but it'll be one for the books. I've got a gearbox to build in the meantime and have just realised, I sold my ally flywheel as well.

Bugger off, I'm getting there.