30MPG at 60-80mph - 325i. Problems? Advice please!

[e301988325i]

Some AFM/MAF allen key adjustment done - idles well

What has this been adjusted too?

Any figures? (CO%)... You would need a gas analyser to do this by the way....

What was the CO level before you started adjusting?

Going to get my one done soon at a friendly MOT station, as Im suspicious that its been messed with previously.... Would like to know what is the benchmark/optimum CO% figure for a stock factory healthy M20 2.5?

1% or just under

[Barnz]

I think it's the 4.10 final drive - she's about/under 3000 rpm at 70mph.

Minicooper172 - 440 miles? HOW THE F***!!!! JEALOUS!!!

So what's up with my engine, why so thirsty? Is it even worth considering the LPG investment if she's a bit of a dog to start with?

I know how to drive 'economically' - it was a pain for me to even achieve the numbers above. I can get 48mpg on the motorways with my N42 engine at 70mph with cruise control on...

First decision is "can I fit the LPG conversion myself?". If yes, then in my opinion it's a no brainer and you should go for it.
If you can't fit it yourself then bear in mind that as long as you buy decent LPG kit, it will roughly halve your fuel bills for the duration of your ownership AND you'll be able to either sell the car for more than the going rate or sell the kit on in here.....recouping some of your money.

Don't know about anyone else but wouldn't fit an LPG kit myself and I know a bit about cars..... I know the LPG cost is about 45-50p here in UK, but does the car perform the same? Does it do the same MPG if you measure in MPG with LPG? Lots of PG.....

[N00b]

Don't know about anyone else but wouldn't fit an LPG kit myself and I know a bit about cars..... I know the LPG cost is about 45-50p here in UK, but does the car perform the same? Does it do the same MPG if you measure in MPG with LPG? Lots of PG.....

Personally, I wouldn't fit a kit myself either.....but lots of people in here are confident and able enough to do it.
The car performs no differently while running on gas, although you lose around 15% of your economy due to the lower calorific value of gas. So 30mpg on petrol will return around 27ish on gas.....but gas is half the price of petrol so you're still quids in.

[Brianmoooore]

Don't know about anyone else but wouldn't fit an LPG kit myself and I know a bit about cars..... I know the LPG cost is about 45-50p here in UK, but does the car perform the same? Does it do the same MPG if you measure in MPG with LPG? Lots of PG.....

If you 'know a bit about cars', then you'll know there's no reason why there should be any reduction in performance! Why should there be?
Propane is a much more suitable fuel for an internal combustion engine than petrol, as an engine needs to run on a gas/air mixture, not a liquid, and LPG readily becomes a proper gas if its pressure is reduced and a bit of heat added. Unlike petrol, which only becomes a pseudo gas in the form of suspended droplets, which will readily drop out of suspension if given half a chance.
This leads on to the other major advantage of LPG - because petrol drops out of suspension so readily in a cold engine, much more petrol than is needed has to be fed into the engine while its cold to compensate for this, and the excess fuel makes a good job of destroying the oil lubricating film for the pistons in the bore, resulting in the majority of engine wear taking place during this phase.
LPG has no such problems, as reflected in my LPG fuelled 226,000 mile M50B25 engine, which still has compression figures similar to when it was originally run in.

[N00b]

^^^
Is it an urban myth that Rolls Royce used to bench run-in their engines on LPG?

[Adil786]

think you need to buy a diesel 106 matey

Thanks.

A thirsty engine can be caused by one or many things running off-optimal. I'm not talking about tyre pressures, aerodynamic drag, but more the general condition of the motor.

Since I'm trying to restore a M20B25 lump back to good condition (as close to new as poss without rebuilding the bottom end - I've done the top already), I'm trying to see if the motor needs fine tuning, or if i have bigger probs like not building compression ( that = more work than I'm prepared to do without doing other checks first ).

Simple things like checking the thermostat, air leaks on the intake, holes in the exhaust, etc are useful checks, as suggested by other zoners (thanks all by the way).

I doubt a 106 lump is going to really help me diagnose a problem, or solve it. Unless you're saying that BMW need to learn some lessons from the french?

[Adil786]

Some AFM/MAF allen key adjustment done - idles well

Any figures? (CO%)... You would need a gas analyser to do this by the way....

A general tweak with allen key and test with engine warm. Sure it's not exact, but she idles much better than before - well, once she's warm the throttle is much more responsive and she still pulls hard.

Good advice about getting it measured properly though - and good to have a target figure.

[Adil786]

Don't know about anyone else but wouldn't fit an LPG kit myself

as reflected in my LPG fuelled 226,000 mile M50B25 engine, which still has compression figures similar to when it was originally run in.

If that's not a convincing case for LPG, I don't know what is!

Barnz - I'm more than happy to do the work myself and will do in the near future.

[Brianmoooore]

Don't know about anyone else but wouldn't fit an LPG kit myself

as reflected in my LPG fuelled 226,000 mile M50B25 engine, which still has compression figures similar to when it was originally run in.

If that's not a convincing case for LPG, I don't know what is!

Barnz - I'm more than happy to do the work myself and will do in the near future.

Red touring in my sig. also has a 200,000 mile LPG (M20B25) engine in it as well, which also performs like new.
As some of you will know, this particular touring is now dead, but the engine (and gas kit) will live on, almost certainly in my cab., which has half the mileage, but worryingly low compression figures!

[Barnz]

Don't know about anyone else but wouldn't fit an LPG kit myself

as reflected in my LPG fuelled 226,000 mile M50B25 engine, which still has compression figures similar to when it was originally run in.

If that's not a convincing case for LPG, I don't know what is!

Barnz - I'm more than happy to do the work myself and will do in the near future.

Brian & Adil -
Thanks for all the info, very useful. Sorry wasn't saying LPG is bad, in fact I'm looking into using it now in my next car..... just rather get someone more qualified to fit it than me. I know "a bit" about cars and that's it..... my point
Love to try an LPG car out someday..... sick of +£1 prices!
Thanks guys, no offence!