Hypermilling on LPG

[pmiulian]

So, things have happened in the last 2 weeks. I got a SG - yeeeeii
And it turns out, it is all worth it. I already had a vacuum gauge installed, but the SG showed me that I didn't know how to use / interpret the vacuum gauge.
With a little SG, a lot of P&G and some DWL, it seems that I am going from a 27 mpg city driving, to an unbelievable 38 mpg city driving. Not 100% sure of that, but that's what the SG indicates. I just filled up the lpg tank and I'll have to wait for the next fill-up for the official numbers.
So all of this is city driving - I can't wait to get a chance to test it on the highway.
Great tool this SG - it does open your eyes on stuff that you thought you knew. Also, it's addictive

[pmiulian]

I did a 950km trip this weekend and I tried P&G on the highway. The car was fully loaded, but the FE was poorer than I expected. So I got 37MPG highway driving, using P&G, compared to the 38 mpg of city driving. This can`t be right. I`m doing something wrong.
I did use a full grill block upper and lower grill. And the speeds for my P&G were usually 40 - 60 mph or 45 - 65 mph.
Maybe I`m not accelerating as I should, or maybe the speed I use is to high.

[euromodder]

Originally Posted by pmiulian

This can`t be right. I`m doing something wrong.

Did you calibrate the SG first, using a few actual fill-ups ?

Maybe I`m not accelerating as I should, or maybe the speed I use is to high.

You should accelerate rather swiftly at a fairly high engine loading (LOD on the SG), say 75-80 %, using low revs - in the highest gear that the car can handle.
This puts you in the range where engines usually get their best BSFC, i.e. where most HP is produced for the gas being used.

[pmiulian]

I really don`t need to calibrate the SG. When I use it, I just target for the best FE ... so it doesn`t matter how wrong the SG numbers are, as long as they are consistent. Besides that, I have an additional lpg tank which the ECU doesn`t know of - so the SG will get data from the gas tank which is always full.

I think that my SG shows me the actual HP that the engine produces, not the % of power used. At idle I get LOD=2, and when accelerating I get LOD to 30-40.
From what I understand, the BSFC says that my engine ( 1.3 gasoline ) is most efficient between 1800rpm and 2200 rpm, so I try accelerating in this range. On highway driving, I get to 3000 rpm - that is the rpm for 65 mph.

[pmiulian]

Ok, so I've been playing with the SG and managed to improve my city mpg. From an usual 27 mpg I managed to get to about 33 mpg and on some trips I got close to 35 mpg. I did this by using the engine in the 1000 - 1500 rpm. I have to say that the mpg numbers are pretty low, but the driving feeling suffers a lot.
My best consumption was done when the traffic was light, but otherwise it's very hard to keep up with the others using the engine in that rpm range. The engine is small and not very powerful by default, and the lpg doesn't help.
I tried searching for ways to improve the torque in the low rpm area ( at around 1k rpm ), but not much can be done without serious mods to the engine.
The only "tune" that I can think of is messing with the air intake so that I can move the torque curve to lower rpm.
I know that lpg has a high octane and I could mess around with advance but last time I serviced the car, I've been told that the engine pings a lot, so I would rather leave it alone.

[RiceCake]

Increase the compression ratio and the timing. Then it'll "boss mode."

Propane, LPG, LNG; they're all rather high octane fuels. Converting a regular car to run on it means it runs, sure, but rather half-heartedly for what its being fed.

[pmiulian]

I`ve noticed something interesting when running on lpg.
It seems that I get better FE going 100 to 110 km/h than going 80 or 90.
I think that it is because the lpg ecu has some problems in the lower rpm. At 105 km/h the engine stays at about 3000 rpm. That is the peak torque rpm - so it seems that the lpg gets along better with the overall car configuration at that rpm.
If I run on gasoline, I get better FE at about 85-90 km/h.

[pmiulian]

Just did a 881km trip, with about 50km in town driving and the rest on the express.
I used almost 55 liters of lpg. That gives a FE of about 6.25l / 100 km.
It is one of the best FE that I managed to get running on lpg. This time I used the vacuum gauge and kept the vacuum at about 15, with slow acceleration.
With this level of throttle the car would go at about 80 to 85 km/h.
Pretty slow, but eventually I got there.
So the FE would translate to 37.64 MPG ... on lpg.
Considering the price difference between lpg and gasoline, it would come to an equivalent gasoline FE of about 3.6 l/100km ( that is 65.34 MPG ). It`s better than a diesel

[320touring]

Is your car a single point LPG system?

My 328i does 270 miles to 50L of LPG driving sensibly,

and 230 flat out..

can you guess which is more fun?

[pmiulian]

Hey - I've read about your car ( in your posts ).
There is a bit of a difference between our cars
Mine has a 1.3 liter engine and a mind-blowing 84 HP from the factory. By now probably 20 of those horses are dead.
But the car goes - I call it donkey - because it`s lazy, grey but keeps on going without requesting too much food.
So the most fun with my car is doing trips ... I've seen most of my country with this car.
I get the best feeling knowing that it is reliable, comfy ( it has very soft suspensions ), and it`s very cheap to run.

The funny fact is, that by using my car, especially on LPG, it`s cheaper for me to use the car than the train or other public transport. And that is for one person using the car - not talking about bringing someone else with me.
Even in city driving, with the low FE, I get the same price going to work as using the public transportation.

Oh - I forgot - my engine is 1.3 sohc MPI ( multi point injection ) and the lpg system is a Tomasetto stag 200.