Brim to brim...

Message
Author
Pinger
Member
Posts: 277
Joined: Tue Feb 11, 2020 5:08 pm

Brim to brim...

#1 Post by Pinger » Tue Sep 22, 2020 8:40 pm

Brim to brim as we all know is the most accurate method for ascertaining fuel consumption with petrol and diesel. Is is as accurate with LPG?
A remark by another LPG user along the lines of 'the tank accepts what it does on its own whim' and some numbers I saw today got me to wondering.

I did a brim to brim today at the same pump (with 113miles between them) and some seven hours between fills. Half way into the (there and back) journey the fourth light went out and the knowing (from its first fill) the capacity and the mileage I calculated 15.4mpg. The overall figure from the brim to brim dropped to 13.8.
Where's the missing 10%? The return leg would have had to have been below 13.8 and while I was more running into a strongish headwind and inland is that enough to return the disparate figures? Or. is filling an LPG tank such an inexact science to render the figures meaningless (given both calculations rely on (three separate) tank fillings to maximum capacity)?

Gilbertd
Advanced Member
Posts: 8545
Joined: Wed Apr 09, 2008 10:00 am
Location: Peterborough

Re: Brim to brim...

#2 Post by Gilbertd » Tue Sep 22, 2020 9:04 pm

Ignore the lights on the switch, they are notoriously inaccurate. On mine I fill the tank and get all 4 lights, after 50 miles it drops to 3, after 70 it's down to 2, 80 shows 1 and the red light comes on after 100 miles but I can do over 200 miles before it runs out. I suppose I could play around with the settings but it doesn't seem worth it. Headwind affects my car (having the aerodynamics of a small bungalow), as does tailwind, inclines and just about everything else you can think of. For example, on my trips to the south of France I always get more miles per tank on the latter part of the journey than at the beginning as there's more uphills on the first part of the journey than the second. Due to the aerodynamics, or lack of, cruising speed makes a difference too. I drove to Latvia and back last week and was stopping to fill up every 200 miles or so. On one fill I achieved 214 miles on 51 litres but had been stuck at 50 ish mph for hours on single carriageway roads in Poland. Another fill took 64 litres after 203 miles.

You've got it right by using the same pump but a change in temperature will alter the amount that goes in (as it alters the density) so really you need to average it out over a number of fills.
96 Saab 900XS, AEB Leo, sold
93 Range Rover 4.2LSE, Lovato LovEco, sold
97 Range Rover 4.0SE, multipoint, sold
98 Ex-Police Range Rover 4.0, AEB Leo, daily motor
96 Range Rover 4.6HSE Ascot, AEB Leo, my spare


Proud member of the YCHJCYA2PDTHFH club.

Pinger
Member
Posts: 277
Joined: Tue Feb 11, 2020 5:08 pm

Re: Brim to brim...

#3 Post by Pinger » Tue Sep 22, 2020 9:35 pm

My return leg should have balanced out the headwind and elevation change for the same reason you site - traffic. In my case when I think about it it was slow enough to deprive me of top gear so not exact science. It was the first opportunity to try and get a handle on mpg just driving and not test driving.
Which tank's temperature has the bigger influence on filling? I'm guessing the one being filled - in which case later in the day (with a tank inside a warmer cabin) it doesn't flatter my figures!
On level ground, can the gauge lights be trusted between intermediate lights eg between the third and second lights being extinguished (which would be 19 litres on mine)? What about the readings the AEB software shows?

Brian_H
Intermediate Member
Posts: 1931
Joined: Mon Jan 23, 2012 12:21 pm
Location: Milton Keynes

Re: Brim to brim...

#4 Post by Brian_H » Tue Sep 22, 2020 9:50 pm

The cars tank will be cooler though from having been emptied. It does vary a bit though I find anyway particaully between pumps (you only have to see how quickly some fill compared to others on the same car to see that effect).

The lights display what the software is set to - and that value can be effected by a few things, any resistance in the wiring being one, a sender that doesn't work properly being another. If its a multivalve we are talking about here (which I think it is given your other posts) the small size of the sender limits the difference your going to see between full and empty somewhat.

One of mine only gets upto about 1.8v at full, another other shows around 4v full dropping to under 1v when empty. Some of that depends on the type of sender as well, the typical one used is a 0-90 ohm one, but that doesn't mean thats what you might have. They will look identical apart from markings, but some give readings over a range, others give 1 of 4 or 5 values depending on the pointer position (for older systems with little to no electronics or adjustment, typically an open loop mixer type system).

You might have some luck with adjusting the values in the software, if your struggling to get it to work properly it may be easier to remove the sender from the tank, and move the pointer about with a screwdriver on the back (magnetic) to see if the readings it gives make any sort of sense. If its going all over the place, the sender is probabbly shot. if it has a fairly linear movement it should be ok, this would allow you to see what the readings are based on the pointer position and then adjust the software to suit. You'd then probabbly want to fine tune it with actual use, best way to do that is to work out your range, then use that to reference what voltage is shown at the appropiate fractions of that range.

Trapped air also has some effect if its a new tank from what I've been told, depending on the type of tank this can be avoided. If the tank has been vented (multivalve removed after its had some gas in it) and the valve is towards the top, then its probabbly not an issue. You'd see that by filling that slows down to a crawl before stopping as a likely symptom of that. One of mine suffers from it but haven't got round to addressing it yet.

Pinger
Member
Posts: 277
Joined: Tue Feb 11, 2020 5:08 pm

Re: Brim to brim...

#5 Post by Pinger » Tue Sep 22, 2020 10:53 pm

For now at least, I'll be filling from the same pump - this is rural Scotland, the next nearest pumps are 30 miles in opposite directions.
All I was really wanting was to be able to do accurate brim to brim calculations to monitor ongoing changes in set-up and calibration as the apply to proper not test drives. I could have used the fuel between the third and second lights going out I'd have settled for that but today was the first I've seen the fourth light go out cleanly (ie not on and off over 10+ miles) and that was because I was on the flat of the coast as opposed to the very hilly region I live in.
The AEB software I think reads between 0 and 255. When I got home (8 miles from filling the tank as full as it would go) it was showing '1'. And it should have been about a half gallon down from full. If I can work out what each increment is in litres maybe I can use the AEB to check actual journey mpg. Testing (including calibrating on the driveway (zero miles covered))is screwing up any attempts at working out mpg. When the opportunity for a 'proper' drive arises, I want accurate before and after fuel levels numbers to know the fuel used. Once I get a handle on the mpg, I'll do what everyone else does and just work on range!

One thing that will probably impact on mpg is over-run fuel cut off. Currently disabled, I'd like to see exactly the mpg gains from it vs any drivability issues it can throw up and let that influence the degree to which I deploy it - or don't. That kind of monitoring is what I'm after. I'm spoiled by that being easily done with purely petrol cars.

It would also be useful to have all the AEB parameters displayed on a small screen in my line of sight while driving - but with that idea I'm probably somewhere between barking at the moon and pissing in the wind.

Brian_H
Intermediate Member
Posts: 1931
Joined: Mon Jan 23, 2012 12:21 pm
Location: Milton Keynes

Re: Brim to brim...

#6 Post by Brian_H » Tue Sep 22, 2020 10:57 pm

Not sure if you can use a bluetooth dongle on your system? - The KME I've got will do this (and was a reason for choosing that ecu for an additional vehicle), and display some data in an app. Will depend on your specific ECU really. More chance with newer kits than older ones.

Pinger
Member
Posts: 277
Joined: Tue Feb 11, 2020 5:08 pm

Re: Brim to brim...

#7 Post by Pinger » Tue Sep 22, 2020 11:20 pm

Brian_H wrote:
Tue Sep 22, 2020 10:57 pm
Not sure if you can use a bluetooth dongle on your system? - The KME I've got will do this (and was a reason for choosing that ecu for an additional vehicle), and display some data in an app. Will depend on your specific ECU really. More chance with newer kits than older ones.
Alas my dumb phones (and the reception for smart phones where I live is so bad snails go door to door because it's faster than sending a text) won't support such a thing so I'd need another screen and at these things I am totally useless.
I do have an MP3 player which operates on Android, has a camera (video and still) among other features and has Bluetooth. How I load the AEB software onto it though I have no idea. If I could, I wouldn't need Bluetooth as I can run a USB cable from engine bay to cabin. I seem to recall loading it onto a lap top with Windows 7 was onerous to the limits of my capability. That said, I'll have another look at the AEB software and see if it's possible. It would be a big help if it worked.

Gilbertd
Advanced Member
Posts: 8545
Joined: Wed Apr 09, 2008 10:00 am
Location: Peterborough

Re: Brim to brim...

#8 Post by Gilbertd » Tue Sep 22, 2020 11:36 pm

No, it isn't possible to use a Bluetooth dongle with the AEB 175, it's old school serial data, even getting it to talk using USB can be a bit hit and miss. When the lights change is always a bit iffy at the best of times, partially due to the fact that the sender isn't that accurate. It's driven by a float in the tank but there's no baffles so when on the move the liquid level will be sloshing around all over the place. I know mine reads lower on a sweeping left hander and higher when going right. It also reads higher when going uphill than down. So although it always drops from 4 to 3 lights after 50 miles, if I take a nearby right hand, uphill turn, I can get all 4 lights on when I've done over 60 miles since filling up.
96 Saab 900XS, AEB Leo, sold
93 Range Rover 4.2LSE, Lovato LovEco, sold
97 Range Rover 4.0SE, multipoint, sold
98 Ex-Police Range Rover 4.0, AEB Leo, daily motor
96 Range Rover 4.6HSE Ascot, AEB Leo, my spare


Proud member of the YCHJCYA2PDTHFH club.

Brian_H
Intermediate Member
Posts: 1931
Joined: Mon Jan 23, 2012 12:21 pm
Location: Milton Keynes

Re: Brim to brim...

#9 Post by Brian_H » Wed Sep 23, 2020 4:52 am

Ah hadn't realised it was a 175 being used. So no as you say not possible there.

Pinger
Member
Posts: 277
Joined: Tue Feb 11, 2020 5:08 pm

Re: Brim to brim...

#10 Post by Pinger » Wed Sep 23, 2020 9:46 am

Gilbertd wrote:
Tue Sep 22, 2020 11:36 pm
No, it isn't possible to use a Bluetooth dongle with the AEB 175, it's old school serial data, even getting it to talk using USB can be a bit hit and miss. When the lights change is always a bit iffy at the best of times, partially due to the fact that the sender isn't that accurate. It's driven by a float in the tank but there's no baffles so when on the move the liquid level will be sloshing around all over the place. I know mine reads lower on a sweeping left hander and higher when going right. It also reads higher when going uphill than down. So although it always drops from 4 to 3 lights after 50 miles, if I take a nearby right hand, uphill turn, I can get all 4 lights on when I've done over 60 miles since filling up.
Yep, where I live is so hilly (and the truck is parked nose down on a steepish driveway at home) that 'lights out' can span 20 or more miles. Yesterday on the flat of the coast was the first time one light had gone out and stayed out.

Your comment re ''even getting it to talk using USB can be a bit hit and miss'' also gets a 'yep'. There are times when I hook up the lap top I get the TPS and rpm and that's all. It's way beyond O2 sensors being at temp as it can happen after a spirited drive when I hook it up without even shutting the motor down and mere moments from coming to a halt. Eventually, I will get the O2 and actuator displays but it can take a few minutes and no amount of engine off/on or exit / re-open makes any difference. I've also had the system freeze where only a hard shut down (off button) of the lap top worked.

A small screen on the dash would be a massive help. I get that in steady state cruise the AEB will adjust to stoich but with all the hills and bends here I am by necessity on and off the throttle and watching the transients would maybe pin point any over (or under) fuelling. Lap top on the passenger seat is fine to a point but the roads here are so narrow as for that to be hazard in it's own right. I've come too close too often already to leaving the road for it to be viable in everyday driving. Maybe the AEB scanner is what I need but I seem to recall them being quite pricey and Covid is not being kind to my income.

Brian_H
Intermediate Member
Posts: 1931
Joined: Mon Jan 23, 2012 12:21 pm
Location: Milton Keynes

Re: Brim to brim...

#11 Post by Brian_H » Wed Sep 23, 2020 6:06 pm

There would be very little needed to hookup a multimeter to the output from the sensor and place it somewhere sensible if its just the level your after looking at to work out where to set it? Should be able to be done near to the front end loom and bring it to somewhere suitable to see it?

Brian_H
Intermediate Member
Posts: 1931
Joined: Mon Jan 23, 2012 12:21 pm
Location: Milton Keynes

Re: Brim to brim...

#12 Post by Brian_H » Wed Sep 23, 2020 6:13 pm

You might also find a proper serial port to work better than a usb one. If you have an old laptop with a proper com port (getting harder to find one that still works now of course with a decent battery) that might be best, even if its running an older version of windows.

Pinger
Member
Posts: 277
Joined: Tue Feb 11, 2020 5:08 pm

Re: Brim to brim...

#13 Post by Pinger » Wed Sep 23, 2020 6:38 pm

Brian_H wrote:
Wed Sep 23, 2020 6:06 pm
There would be very little needed to hookup a multimeter to the output from the sensor and place it somewhere sensible if its just the level your after looking at to work out where to set it? Should be able to be done near to the front end loom and bring it to somewhere suitable to see it?
For that I'm going to look and see if I can calibrate the tank level as it shows on the AEB screen. Zero is full. 255 is - either the theoretical 120 litres or actual 100 litres from that. Any idea which. Then, I could just check it before and and after a journey to calculate mpg - and without having to go and brim the tank every time.
If I wanted a more accurate instantaneous display - I'd look at wiring it to the petrol gauge and the petrol tank to the lights if that would work. As it is, I trust the lights enough not to let me run out of LPG.

On the dash it's the O2 and actuator display I could most usefully use. The O2 output is simple voltage. What drives a stepper motor I've never understood. If I could configure those to read on small voltmeter gauges.... But the more I think about it the more I realise I'd need the actuator represented as it is on the lap top - just a much smaller display. I did have a look at my Android MP3 player but it's touch screen has lost its calibration so badly it can't even be recalibrated so not going anywhere with that!

Pinger
Member
Posts: 277
Joined: Tue Feb 11, 2020 5:08 pm

Re: Brim to brim...

#14 Post by Pinger » Wed Sep 23, 2020 6:48 pm

Brian_H wrote:
Wed Sep 23, 2020 6:13 pm
You might also find a proper serial port to work better than a usb one. If you have an old laptop with a proper com port (getting harder to find one that still works now of course with a decent battery) that might be best, even if its running an older version of windows.
Aha! Just had a look at the lap top I use for this (an older one) and it has what I assume is a serial port on it. But the cable I have is USB (and serial at the AEB ECU end). Do I need then a cable with serial connections both ends and would that enable a better more predictable connection? What type of serial connection is it if I have to go looking for a cable?

Brian_H
Intermediate Member
Posts: 1931
Joined: Mon Jan 23, 2012 12:21 pm
Location: Milton Keynes

Re: Brim to brim...

#15 Post by Brian_H » Wed Sep 23, 2020 8:07 pm

Your probabbly stuck without buying another cable then, though if your older laptop isn't running windows 10, you might have more chance convincing it to behave better. The port on the ECU won't be serial as such, as the voltages will be wrong (your lead converts between 2 different standards to make it work). Don't plug a normal serial lead between the two even if it will fit, you won't get it to work and may damage either of them in the process.

Serial port would look like the one on the end of this card, but if you don't have the matching lead you may be stuck anyway.
https://www.amazon.co.uk/StarTech-com-N ... B002LITGA4

Gilbertd
Advanced Member
Posts: 8545
Joined: Wed Apr 09, 2008 10:00 am
Location: Peterborough

Re: Brim to brim...

#16 Post by Gilbertd » Wed Sep 23, 2020 8:22 pm

If the laptop is old enough to have a serial port, there's no way it would be up to running Windows 10. Are you sure it is a serial port? 9 pins arranged in two rows rather than 15 pins in 3 rows (and usually blue) which is a VGA port used to connect to an external monitor.
96 Saab 900XS, AEB Leo, sold
93 Range Rover 4.2LSE, Lovato LovEco, sold
97 Range Rover 4.0SE, multipoint, sold
98 Ex-Police Range Rover 4.0, AEB Leo, daily motor
96 Range Rover 4.6HSE Ascot, AEB Leo, my spare


Proud member of the YCHJCYA2PDTHFH club.

Brian_H
Intermediate Member
Posts: 1931
Joined: Mon Jan 23, 2012 12:21 pm
Location: Milton Keynes

Re: Brim to brim...

#17 Post by Brian_H » Wed Sep 23, 2020 8:36 pm

I have a Dell D630 which does run windows 10, and does have a serial port on it. It is a bit slow though and has been upgraded to make it run windows 10 (Ram and SSD).

LPGC
Installer
Posts: 4071
Joined: Wed Sep 29, 2010 6:01 pm
Location: Yorkshire
Contact:

Re: Brim to brim...

#18 Post by LPGC » Wed Sep 23, 2020 9:25 pm

I find that for computers / laptops old enough to have serial ports there are no drivers available for W10 anyway, not even for W7.
Full time LPG installer
Servicing / Diagnostics / Repairs to all systems / DIY conversion kits supplied with thorough tech support
Mid Yorkshire
2 miles A1, 8 miles M62,
http://www.Lpgc.co.uk
Twitter https://twitter.com/AutogasSimon
07816237240

Pinger
Member
Posts: 277
Joined: Tue Feb 11, 2020 5:08 pm

Re: Brim to brim...

#19 Post by Pinger » Thu Sep 24, 2020 9:09 am

Gilbertd wrote:
Wed Sep 23, 2020 8:22 pm
If the laptop is old enough to have a serial port, there's no way it would be up to running Windows 10. Are you sure it is a serial port? 9 pins arranged in two rows rather than 15 pins in 3 rows (and usually blue) which is a VGA port used to connect to an external monitor.
On the back of the lap top it is the three row port.
When I looked at Brian_H's link then compared them, the difference was obvious.

I do have an even older lap top that has a serial port that has two rows of pins. One row has 13 and the other 12. The lap top has no battery though and is a bit on the slow side. It is retained though for other (work related) purposes and mains powered.

Pinger
Member
Posts: 277
Joined: Tue Feb 11, 2020 5:08 pm

Re: Brim to brim...

#20 Post by Pinger » Thu Sep 24, 2020 9:20 am

LPGC wrote:
Wed Sep 23, 2020 9:25 pm
I find that for computers / laptops old enough to have serial ports there are no drivers available for W10 anyway, not even for W7.
The lap top I am using was sourced specifically for being W7 as it is (apparently) the easiest to get Delphi cloned software to work with and I needed to interrogate the smart at the time. Loading the AEB software from the disc was an involved process but it works (albeit reluctantly at times).

When I loaded the same disc into my W8 lap top I couldn't make any progress in downloading from it.

Yesterday, I did 'send' the AEB programme from the lap top to the MP3 player and as the contents of the MP3 player displayed on the lap top screen, it was there. However, with the MP3 player disconnected from the lap top there was no sign of it and due to its touchscreen being out of calibration, little possibility of finding it.

I do have another device I could try loading the AEB software onto (if that can be achieved by clicking 'send' that is). It runs on a Palm OS and is about 13 years old. Nothing to lose by trying though my optimism isn't sky high.

Post Reply