Fuel Econ/Tuning

[Ride_on]

My 87 360 GLE has done 200,000, well looked after and a lovely running engine. I used to work 25 miles away for about 15 years and had 10 300 series including the above car and a few others. Sometimes I would speed, but mostly I drove at about 60. Here's what I remember;

360s (inj or carb) - no better than 30mpg, whatever I did
1980 340 1.4 - maybe 35mpg
1985 340 1.4 - An amazing 45mpg
1986 340 1.7 - Maybe 35mpg
940 Turbo HPT - 24mpg (think I managed 30mpg stuck with a slow driver in another car driving 600miles round Scotland (50mph), and a recently cleaned ignition)

A family member claimed they got 30mpg regularily from their 940 LPT.

I really would not try leaning out the mixture too much, it should be just be at the lower end of the scale. I usually find its very hard to measure so I just aim for the middle. I tried messing about with it in my first 340 and ended up burning the valves. After a valve lap it was a different car, quieter, torquey, 35mpg.

I never tried driving at 50mph, but I think that might significantly improve average MPG going on the 940 results.

[trabitom99]

Basically, the slower you go, the more your fuel economy improves. If you find a stretch of road where you can do 40 all day in fifth, then you'll be getting better economy than 50, 60, 70, 80, etc ...

My personal "best" in a 300 - a 50 mpg (Imperial) run to the UK and back, at a steady 50mph, in a B14.3E-engined 343 (a downtuned 64bhp version), when I was seriously strapped for cash. No fun at all, the biggest problem is lorries on your tail.

My personal "worst" - 23,5 mpg in a B200F 360 on a full-throttle Autobahn blast. I average about 30 mpg with this car, although I don't do much town driving in it.

In stop and go traffic, under 20mpg is realistic though, even with a well-tuned engine ...

Tom

[classicswede]

Both my dad and brother get best MPg in their 240 GLT's at 80 - 90 MPH (spedo). I can only put that down to the high gearing. With carb models 240 best would be at 70. Best MPG is more a case of rev range - you need to be doing between 2500 - 3000 rpm engine speed.

A lot of the 360 injection MPG problems are down to the ecu mapping. Andy with the MS fitting is getting quite good MPG from what I remember.

The other option is to switch to cheaper fuel

[volvosneverdie]

The other option is to switch to cheaper fuel

as soon as lpg conversions get cheaper than cars themselves, i plan too.
we'll all be on hydrogen by then probably.

[classicswede]

Well 300 series prices are rising

There is a very good offer on the tanks for 360's so at the moment while taht offer lasts I can do a 360 mixer conversion for £700 with spare wheel tank.

To pay for that you will need to put in £1400 (or £700 of petrol eq) of LPG - if you do many miles that does not take long.

so if you put in £35 of petrol a week that would take you 20 weeks to pay for teh conversion and after that you would be saving £17.50 a week

or if you were putting in £70 a week it would be 10 weeks and then a saving of £35 a week

[volvosneverdie]

Maths make perfect sense man.
£700 up front and the petrol down to your end is the stumbling block though.
Lot of money these days.
Dont think many have got that lying round at the moment.

[Speedy88]

Also LPG does tend to explode in accidents...

[magnumpi]

Just my 2pennys worth i did 550 miles in 2 days last week saw 120 on the clock at least a few times (yes a private test track ) and did £90 of fuel with my Williams on my 1.4 diff.

[classicswede]

Also LPG does tend to explode in accidents...

Not true that tbh. The cases of LPG expolsions/fires have been down to LPG leaking in the car. In a correctly installed system lpg leaking would not cause a fire inside the car as the lpg is vented to outside should there ever be a leak. LPG does have a strong smell so you will know if it leaking.

I do know of a LPG converted VW camper that caut on fire do to a petrol leak and teh only thing left of it was the LPG Tank!

VND £700 is a lot to stump up in one hit. I'm sure one day somehwere will start do finance for LPG conversions. The downside with that is having to pay intrest would make it take a bit longer before you actualy start saving.

[Speedy88]

Fair enough, I've only heard that from a (reliable) American friend but they do make their cars out of cheese over there. If I ever start communting huge distances again I'll consider it.

[classicswede]

I@ve never heard of a LPG explosion in the us but gas (petrol to us) tanks expoding is was very common. Ford had problems with one ofs car that basicaly if you had a crach the petrol tank would explode. Ford being ford worked out it was cheaper to pay compensation for injury's and death's that it would be to change to desine of the car!!! Now that is accounatnts for you

[Ride_on]

Hydrogen storage is still a long way off, needs a significant development to make it feasible. You can do your own electric conversion for a few £1000, and get a range of maybe 30 miles, spend a bit more on Lithium batteries and you can get 100miles.

Speaking of hydrogen, I am currently awaiting the Car Mechanics long term test result of an HHO conversion. I have a feeling it might work on a 360 because of the generally bad burn pattern. Basically you electrolise water in real time with the alternator and feed the HHO mix directly into the engine. Apparently it super cleans the engine (like a steam clean) and helps with burn pattern.

On first inspection it looks a bit perpetual enginey, but as a burn aider it might actually work. The one they generally reviewed looked a bit Heath Robinson and dangerous to say the least. Apparently they started with too low rated relays which fused keeping the thing on after engine off, an explosion resulted. From memory they claimed 5-15mpg improvment, I'm not convinced but keeping one eye on it.

Anyone heard of this?

[volvosneverdie]

an explosion resulted. From memory they claimed 5-15mpg improvment,

im guessing thats from before the explosion?

[Ride_on]

It was different cars, they have converted lots, its their day job. Said BMW where too well fuel managed to make much difference, or maybe well burning but did make some.

[classicswede]

I've come across this and I know someone in Scotland that does it.

On a petrol engine you need to lean off teh carb a touch to get full use of it. About 10 - 15% fuel saving sound about right from what I've seen of producing on the fly. With a derv engine similar gains are also possible but with the added advantage or a small power boost.

Google it and you will come with with a few US forums covering the sebject. One day I might have a bash as it.