Bad fuel economy

scarecrow · Post by **scarecrow** » Tue Nov 30, 2010 9:19 pm

I stand corrected then.

I think the pay through the nose route would be the only one open to me if I were to achieve the safe if set up properly part.

Post by **mat_fenwick** » Tue Nov 30, 2010 9:36 pm

It's not a difficult job, given common sense and a reasonable level of mechanical aptitude. If buying a kit new then it should come with suitable (generic) instructions. You then need to get it checked by an approved installer, who will only be able to give you a certificate if they have had the training for the particular kit you fitted, and some are reluctant to do that...

But done well, LPG works well. Payback time on an economical (by V8 standards) vehicle will obviously be considerably longer. Just under 500 notes for a suitable system.

DavidRutherford · Post by **DavidRutherford** » Tue Nov 30, 2010 9:47 pm

saintjamesy89 wrote:How easy would it be to do a DIY LPG conversion on the TU?

Not hard. What you need is a tank that is less than 10 years old so it's still in certificate, a filler, plastic coated pipework, a mixer and a controller kit. If you get all parts second hand, install yourself and then get a local friendly LPG certifier to certtify it, then you're away.

LPG is an excellent fuel for an internal combustion engine really. Burns lovely and cleanly, meaning you have very little engine damage, oil comes out clean. It's about 110 octane too, so if you were feeling very devoted, you could set up an engine with a higher compression ratio and get remarkably good efficiency...

.. or just save some cash on fuel... y'know.. whatever...

saintjamesy89 · Post by **saintjamesy89** » Tue Nov 30, 2010 9:57 pm

Hmm, this sounds very interesting. AND they have a LPG kit for a DIESEL? I would never have thought that would work.

They also do a kit for twin carbs. Wait.

I feel a project on its way. Twin 40 carbs. Flowed head. Increased compression ratio = one 'fast' and cheap to run BX14.

Post by **mat_fenwick** » Tue Nov 30, 2010 10:08 pm

Increased compression ratio (if done to the extent to get the full benefits of the high octane rating) would mean it would struggle to run on 97 octane petrol...

What I've thought about (and mentioned before) is using a switchable supercharger (like Mad Max) to increase the effective compression ratio only when running on LPG.

The diesel kit uses LPG in addition to diesel, and gives some performance and economy gains. Don't know if the latter offsets the fact you would then need to fill up with 2 fuels though...

electrokid · Post by **electrokid** » Tue Nov 30, 2010 10:16 pm

AND they have a LPG kit for a DIESEL? I would never have thought that would work.

LPG doesn't replace diesel as it does in a petrol engine - the idea is that you use less diesel + some LPG. There have been problems with LPG in diesel engines and it's less popular now.

MULLEY · Post by **MULLEY** » Tue Nov 30, 2010 10:38 pm

Never even realised that you could have an lpg'd diesel

Kinda sounds wrong to me & how on earth does it work as lpg seems very different to derv.

citsncycles · Post by **citsncycles** » Tue Nov 30, 2010 11:14 pm

Gearing on the 1.4 is about 19mph per 1000 so at 70 its about 3700

I thought mine felt high geared when I bought it - the GS is pulling 4500rpm at 70mph

!

I'm also quite happy with the fuel consumption, but I guess it's all down to what you're used to - on the motorway the GS can return 35mpg in the summer, but last winter on the commute to work that dropped to 26

!

LPG sounds interesting, although I'll save that project for the Marshall when I get that far - I've been told to expect 14mpg if I'm lucky with that one

kiwi · Post by **kiwi** » Wed Dec 01, 2010 9:37 am

Roverman wrote:Gearing on the 1.4 is about 19mph per 1000 so at 70 its about 3700

Thats assuming the accuracy of the speedometer in to that.

(see my thread re Revs v speed v GPS)

Post by **Tim Leech** » Wed Dec 01, 2010 10:32 am

kiwi wrote:
Roverman wrote:Gearing on the 1.4 is about 19mph per 1000 so at 70 its about 3700
Thats assuming the accuracy of the speedometer in to that.

(see my thread re Revs v speed v GPS)

Im just going off the brochure.

DavidRutherford · Post by **DavidRutherford** » Wed Dec 01, 2010 12:09 pm

MULLEY wrote:Never even realised that you could have an lpg'd diesel Kinda sounds wrong to me & how on earth does it work as lpg seems very different to derv.

When diesel engines run, they always have an excess of air in the cylinder, which even on full power can be as much as 20%. This is effectively "wasted" air, as it uses up engine capacity. By introducing some LPG into the inlet air, far more of that excess air can be used to mix with fuel, and hence produce power.

The engine has to run as a hybrid, as it still needs a diesel injection to start combustion, as there's no spark plug.

electrokid · Post by **electrokid** » Wed Dec 01, 2010 12:09 pm

how on earth does it work

Not very well apparently - which is why it's not so popular now

I heard rumours about damage to some types of engine - not good news.

It needs some diesel in there to get ignition by compression in the normal way - that ignition sets fire to any LPG that's in there as well. Last I heard was the maximum LPG fuel load was around 50% so you're still going to be using half the diesel you'd have used anyway. By the time you've paid for the conversion the savings are unlikely to be worth it. Only half the soot but from memory the flame temp of LPG is hotter so sooty deposits that once helped the valves seal properly get burnt off leaving them vulnerable to failure.

DavidRutherford · Post by **DavidRutherford** » Wed Dec 01, 2010 1:10 pm

electrokid wrote:
how on earth does it work
Not very well apparently - which is why it's not so popular now

I think half the problem is that very few people know how to set one of these systems up properly, and so there 's very little push to sell them.

They also do not yield the same savings as a spark-ignition engine conversion, so there isn't the same financial benefit. The real benefit is the increase in power output of the engine.

MULLEY · Post by **MULLEY** » Wed Dec 01, 2010 4:52 pm

Cheers for the info David.

It would be interesting to actually know what the real world savings would be, at 1st i was thinking if it was anything like a petrol conversion could you be getting near the 100mpg mark

But i'm guessing from what's been said that this won't be achievable & its nearer 10-15mpg at most?

kiwi · Post by **kiwi** » Wed Dec 01, 2010 8:06 pm

Roverman wrote:
kiwi wrote:
Roverman wrote:Gearing on the 1.4 is about 19mph per 1000 so at 70 its about 3700
Thats assuming the accuracy of the speedometer in to that.

(see my thread re Revs v speed v GPS)
Im just going off the brochure.

I realised that and was just pointing out that the speedometer and as I also got told accuracy of the reve counter "MAY" affect it.

Quite a few aspects can come into play regarding the fuel economy of an individual vehicle some of it is due to the carb but other factors to consider as well.

A classic mistake often made it seems more and more each day is the calculation to miles per gallon

You buy your fuel in Litres then convert it to gallons what figure you use can affect that number. How many litres do you think a Gallon is?