Poor MPG

Message

Mud · #1 Post by **Mud** » Thu May 22, 2008 3:08 pm

Hi everyone,

I own a BMW 330ci.

I had an LPG conversion done in Aug last year.

I do about 95% motorway miles and the rest is town driving, with petrol I was averaging 30MPG but with LPG just 18MPG, I would have expected it to be about 25-27MPG with the gas.

Could this be down to a poor map on the gas system?

I have installed a BRC Sequent: GMC

Thanks

uncouth · #2 Post by **uncouth** » Thu May 22, 2008 4:41 pm

Hi there

I drive a bmw 330i Sport Automatic.

I do mainly town driving with a splash of motorway. I am currently averaging 22.5mpg on Gas. Dunno about petrol as I don't like using it.

My driving style is moderate to spirited.

adebov · #3 Post by **adebov** » Thu May 22, 2008 7:46 pm

Mud wrote:..........Could this be down to a poor map on the gas system?........

Well, something's not quite right.
I have a BRC sequential system fitted to my Accord, and have pretty much the same driving pattern.
Average mpg with petrol was around 35.
With gas, I get between 27-30, without changing my driving style.

One thing I have noticed, I seem to get a lower mpg running on Flogas, than Calor (around 28 on Flogas, 30 on Calor).
It could just be my imagination, but it seems like every time I fill up from a Flogas station, I measure a lower mpg (on refueling) compared to if I'd last filled with Calor.
Haven't tried BP autogas (just too expensive).

Mud · #4 Post by **Mud** » Thu May 22, 2008 9:42 pm

I have had one service done on the LPG system, and they did apparently tweak the "mapping" as I mentioned to them that sometimes in 1st gear the car would stall if I pulled away gently.

They said to me at the time that the gas map was almost the same as the original ECU, but with more pressure (or whatever is the appropriate term) at the lower end as the gas has less calorific value than petrol.

Still going from 30MPG to 18MPG is a big difference, I am getting about 260 miles from 60 litres of gas.

Oh and I generally just fill up at Shell and a BP.

uncouth · #5 Post by **uncouth** » Sat May 24, 2008 8:49 pm

This may not be applicable in your case, but when I first had my car converted I had problems. As part of the problem solving process I replaced my DISA controller (See my thread on problems section for details) and my MPG went from 18 to 22-23.

betty · #6 Post by **betty** » Fri Jun 06, 2008 11:07 pm

I had Romano fitted recently on a saab 9000 2.0 LPT auto and can get 48 litres of gas in.Achieve 210 mile sapprox.I guess I would have expected more as well.Runs well and new plugs gap reduced 10% as advised by installer.I fill at ASDA and assume it is FLOGAS?51.9p in Govan,Glasgow.
Any comments?
John

uncouth · #7 Post by **uncouth** » Fri Jun 13, 2008 11:30 am

"I have had one service done on the LPG system, and they did apparently tweak the "mapping" as I mentioned to them that sometimes in 1st gear the car would stall if I pulled away gently. "

Poor MPG and stalling matches the symptoms of failing Vanos seals perfectly. I've just had my vanos seals replaced with 'Viton' ones as the manufacturer seals made from 'Buna' are cr4p; the 'Buna' ones are badly designed and start to degrade due to a combination of synthetic oil and high temperatures (LPG runs hotter that petrol and may accelerate the degredation) and I _strongly_ suggest you consider it, I wish I had discovered this earlier as it would have saved me a lot of heartache.

http://www.beisansystems.com/

Also, don't think that because it seems ok on petrol it cannot be the case. At first my problems just manifested on gas, but after another month or so petrol started to splutter too. If you read that site it will tell you how to diagnose if yours are starting to fail.

Incidentally what mileage is on your car?

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