Fuel Consumption - Optimum Speed

[snowrat]

I am interested to know what the optimum speed is for the best fuel consumption on the Bongo.
I just used the run from fill then fill back to top method of measuring my mpg on a run of just over 300 miles.
I tried to stick between 55 and 65 mph (according to sat nav) and believe it has significantly increased my fuel economy.
I got 34.56 mpg on a run that was 2/3 motorway and 1/3 a roads. I wasn't that strict so next time I get chance I'll try to improve more.

Is 56mph the optimum on all vehicles, or what is it for the bongo, anyone know?

[dunslair]

Zero mph...... If your only interested in economy.

[M 80NGO]

L'oreal cruises nicely on motorways at 2250 rpm which equates to 64 mph, she's in top gear and in the power band not changing up and down gears at the slightest whiff of a hill.

Even on back roads she runs nicely at just over 2000 rpm 57mph

[mikeonb4c]

I am interested to know what the optimum speed is for the best fuel consumption on the Bongo.
I just used the run from fill then fill back to top method of measuring my mpg on a run of just over 300 miles.
I tried to stick between 55 and 65 mph (according to sat nav) and believe it has significantly increased my fuel economy.
I got 34.56 mpg on a run that was 2/3 motorway and 1/3 a roads. I wasn't that strict so next time I get chance I'll try to improve more.

Is 56mph the optimum on all vehicles, or what is it for the bongo, anyone know?

That's pretty much what I'd have said speedwise. At that speed the turbo is reasonably well spooled up (much below 55 and speed can bleed off too easily on an incline, resulting in autobox dropping down a gear), and wind resistance (which rises as the square of the speed, more or less, I believe) is not yet too fierce. Its a bit hard to keep to that speed on motorways and enjoy the driving, but its a great speed on 'A' roads through good scenery, which is one of the great pleasures of Bongo motoring. Even so, that's a very good MPG. I suspect that the fuel pumps on Bongos vary in how well they are set up to meter in fuel - you seem to have a good one

[rita]

I am interested to know what the optimum speed is for the best fuel consumption on the Bongo.
I just used the run from fill then fill back to top method of measuring my mpg on a run of just over 300 miles.
I tried to stick between 55 and 65 mph (according to sat nav) and believe it has significantly increased my fuel economy.
I got 34.56 mpg on a run that was 2/3 motorway and 1/3 a roads. I wasn't that strict so next time I get chance I'll try to improve more.

Is 56mph the optimum on all vehicles, or what is it for the bongo, anyone know?

The secret is the highest MPH with the lowest RPM,looks like you have got it (about) correct.

Cheers.

[snowrat]

Thanks for the quick responses. Pretty much backs up my data. I just wasn't sure if the 56mph you always hear stated is for a standard saloon car rather than the brick of a Bongo.
From what you say Mike and Rita, providing the revs keep you constantly just into in the top gear range economy will be best?
M8ongo, that's pretty much what I have ended up doing, just in the 2000-2250 revs band which gives me approx 60mph.
Thanks Dunslair, although the only time I tend to do that when sat in 'The Talivan' is when it points towards the Borders

Before this last trip I was driving around at about 75mph and getting between 27 and 30 mpg, although I am pretty sure on a trip through France at around 75mph I was getting 30 mpg.
Unfortunately, around town on <2m journeys in winter it is as low as 18 mpg or 23 mpg in summer (if you can call it that).

Very happy with the 34.56, but will try for more!

[briwy]

And if the auto box could be made to change into top gear earlier it would be even better.

[mikeonb4c]

Thanks for the quick responses. Pretty much backs up my data. I just wasn't sure if the 56mph you always hear stated is for a standard saloon car rather than the brick of a Bongo.
From what you say Mike and Rita, providing the revs keep you constantly just into in the top gear range economy will be best?
M8ongo, that's pretty much what I have ended up doing, just in the 2000-2250 revs band which gives me approx 60mph.
Thanks Dunslair, although the only time I tend to do that when sat in 'The Talivan' is when it points towards the Borders

Before this last trip I was driving around at about 75mph and getting between 27 and 30 mpg, although I am pretty sure on a trip through France at around 75mph I was getting 30 mpg.
Unfortunately, around town on <2m journeys in winter it is as low as 18 mpg or 23 mpg in summer (if you can call it that).

Very happy with the 34.56, but will try for more!

You should be in top gear well below 2000rpm, from memory, I can chug along in top gear at around 1300rpm having got to 40mph, teased it into gearbox lockout (top gear as it were) then held gentle throttle pressure whilst speed dropped back to maybe as low as 35 mph (and my speedo is 100% accurate with 17" wheels). Trouble is, at those low revs the turbo is not spooled up and the Bongo will end up dropping out of top gear at the slightest oppostion/incline. I'd set 50mph as min speed (bends and safety permitting!), and 60-65 as max speed, and anticipate inclines by getting speed up a bit towards the 60mph end (turbo at fullish chat) and then allowing it to die off gently to to 50mph if its a short incline.

But if you get more than 35 mpg, you will be doing exceptionally well. I assume yours is 2WD?

[snowrat]

I'll be playing about with some variations and your suggestions Mike, as I now see a challenge to see how much I can get. I was surprised to get over 32mpg.
It is a 2 wheel drive, although hadn't seen any better mpg over my friends 4wd up until now.

[mikeonb4c]

I'll be playing about with some variations and your suggestions Mike, as I now see a challenge to see how much I can get. I was surprised to get over 32mpg.
It is a 2 wheel drive, although hadn't seen any better mpg over my friends 4wd up until now.

Serves to remind just how much man can achieve over machine, with a little thought

A guy who used to be on here (callsign 'Torchwood') teased his Bongo to over 40mpg. To achieve it he folded his wing mirrors (hmm not great for road safety but...) and he fitted a throttle lock type cruise control. He really knew his stuff and knew that maintaining a constant throttle setting and letting speed decay, was the most fuel efficient approach, which is why I mention allowing it to decay on inclines (but only if the incline ends before the Bongo drops a gear, otherwise, try and hold in the turbo-spool-up zone). But the biggest contributor in getting him to 40 mpg was fitting oversize RAV4 wheels to the rear axle. I've toyed with fitting oversize tyres to my rear axle when renewal time comes up (4WD owners - don't try this as you'll wreck the viscous coupling if you don't match rolling circumference on all 4 wheels) but whether I'll bother.....not sure. The Bongo looks quite cool with the rear end sitting up a bit (although that must increase drag a bit, even though downforce might improve roadholding and handling at speed ha ha). Of course, there are no shortcuts to get 2 tons up a hill, or to accelerating it. If you have oversize wheels, the Bongo will just drop out of top gear more easily / not go into top gear as easily, due to increased backload from the wheels. But they do seem to help overall, when cruising, and provided the inclines are not too steep.

[rita]

And if the auto box could be made to change into top gear earlier it would be even better.

You are so correct,would it be possible to tap into the electronic gear shift mechanism and fit a woggle stick.

Cheers.

[snowrat]

40 mpg is impressive.
I thought about changing the wheels for cosmetic reasons but stuck with the standard spec assuming they would be best matched to the Bongo.
I do suffer in winter and around town from cold starts, when it stays in 3rd gear until warm (I believe).
Overrriding this and getting it to go up the gears quicker may help, if it is easy to do of course.
I have always run with snow and mud tyres too, which probably doesn't help, but also may not harm.

[mikeonb4c]

And if the auto box could be made to change into top gear earlier it would be even better.

You are so correct,would it be possible to tap into the electronic gear shift mechanism and fit a woggle stick.

Cheers.

It's been discussed before and I think the conclusion was it could be done but at some risk and with some uncertainty as to usefulness. At this point, I guess the discussion about a manual Bongo starts, as having human command allows them to achieve better urban MPG than the autoboxes. But they are under-geared for cruising, so no benefit there unless you fitted over-size wheels. And personally, I love the autobox: its part of the luxury of Bongo cruising.

[dave_aber]

I did play a wee bit with the TPS, and with a slight adjustment you can make it change up earlier, and you can make it VERY reluctant to drop out of lockup. On my initial test, if I was above 55mph, and I stamped on the throttle, it refused to drop gear.

I did consider making up a wee resistor network box to allow me to offset the TPS electrically by increasing / decreasing resistance offset.

Still on my round tuit list though

(And the modified TPS setting didn't appreciably help MPG)

[mikexgough]

pretty much the figures I achieve..... if your Bongo is well serviced too it all helps.... I tend to stick to 2250-2500 max .... like the others.... I find a few mpg improvement on 25% Veg Oil...