What are the main factors affecting real world mpg on a bus?

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What are the main factors affecting real world mpg on a bus?

Post by passion4 » Wed Nov 02, 2016 12:55 am

I'm running a stockish set-up, 1600cc (it might be a 1641?) twin port, single 34 pict 3 carb, oil bath filter, electronic ignition, stock height with RGB's and 195/80/R15 8 ply tyres and I'm averaging 24-28mpg.

It's not been on a dyno or anything, so is this about right or should I be expecting more, say mid 30's? If so, what needs to be done or looked at first?

All assuming a sensible driving style! :wink:
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Re: What are the main factors affecting real world mpg on a bus?

Post by Hongkongphooey » Wed Nov 02, 2016 8:18 am

Lol, 70 year old engine technology in a vehicle shaped like a brick, 24-28 isn't bad :-)... Maybe a swap to a Scooby lump with modern fuel injection and a 5 speed gearbox?.... :P
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Re: What are the main factors affecting real world mpg on a bus?

Post by wizard 1066 » Wed Nov 02, 2016 8:10 pm

We run a 1776 motor and beetle GT IRS gearbox, 195x65x15 tyres and if driven carefully could just manage 30 mpg on a long run, about town its usually down to 25mpg or less if we drive it with some speed, so your not far off the mark.
Last edited by wizard 1066 on Sat Nov 05, 2016 8:21 pm, edited 1 time in total.


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Re: What are the main factors affecting real world mpg on a bus?

Post by JonnyCJ » Fri Nov 04, 2016 7:32 pm

wizard 1066 wrote:...and if driven carefully could just manage 20 mpg on a long run...
Should that read 30 mpg ?


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Re: What are the main factors affecting real world mpg on a bus?

Post by passion4 » Fri Nov 04, 2016 7:48 pm

So is getting 35mpg+ an unrealistic expectation then?
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Re: What are the main factors affecting real world mpg on a bus?

Post by wizard 1066 » Sat Nov 05, 2016 8:25 pm

Depends on how far you press that right foot, along with how you drive, last week in wales we only managed about 20-25 as it quite hilly, and had to rev the engine above 3000 rpm often to get up the hills, on the motorway at 3000 rpm it gives us 65 mph on the flat road.

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Re: What are the main factors affecting real world mpg on a bus?

Post by Sweet Rides » Mon Nov 07, 2016 9:38 am

passion4 wrote:So is getting 35mpg+ an unrealistic expectation then?
Chris, as you know I have broadly the same set up as you except my engine is a 1600 single port. For genuine (gps) 60mph French motorway cruising I always get a pretty steady 32 mpg. I don`t know what it is around town, but I guess mid to late twenties. I would say that realistically 35+mpg would only be achievable with a very light foot, bit of a tail wind and 45-50mph cruising, but with those factors it is potentially possible.

Also I think single ports have the MPG advantage in a bus as they are inherently more torquey which really helps the momentum of pushing a brick like shape and also have a considerably smaller carb, so are have less capability of gobbling up so much fuel too :wink:


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Re: What are the main factors affecting real world mpg on a bus?

Post by passion4 » Mon Nov 07, 2016 10:01 am

Hi Spence, I don't really understand the difference/advantages between single/twin port engines, although I know everyone's seems to rave about the 1500 single port unit!

Then there is the touted mpg advantages of going 34/36 twin carb as well over the relative simplicity of stock single carb?

Yeah my speedo is a couple of mph out when compared to TomTom sat nav on my phone, but I'm due another European road trip soon, so it will be interesting to compare figures to the recent Scotland one…
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Re: What are the main factors affecting real world mpg on a bus?

Post by readyboy61 » Mon Nov 07, 2016 11:11 am

i can get 33mpg on a motorway run with 1776 twin 34ict carbs at 60mph, 185/65/15 tyres on a AH code IRS box, i dont think i can get any more mpg out of it without a rolling road. What i found made a massive diference was getting the fuel pressure correct for the carbs, many just slap the fule pump on and forget the pressure should be adjusted.
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Re: What are the main factors affecting real world mpg on a bus?

Post by wizard 1066 » Mon Nov 07, 2016 10:38 pm

What fuel pressure regulator are you using, had mine on the rolling road and they said the idle jest were running rich and it might have to do with the pressure, got twin 34 on it.

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Re: What are the main factors affecting real world mpg on a bus?

Post by e m p i » Wed Nov 09, 2016 9:39 pm

Fitting a filter King regulator deffo makes difference to mine. We regularly see 30-32 mpg on a run fully loaded. But if I'm in a rush I can easily get that down to 22-25 mpg :lol:
I've got 1776, Weber 40's, 1303s box and 195/60x14 rear tyres. Mine was set up on a rolling road so although it was a while ago it's still fairly spot on.
Here you go
http://www.dellorto.co.uk/shop/car-acce ... ator-67mm/
Hopefully they've sorted out the instructions because they showed the in/out the wrong way round when I bought mine :lol:
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Re: What are the main factors affecting real world mpg on a bus?

Post by readyboy61 » Thu Nov 10, 2016 9:33 am

e m p i wrote:Fitting a filter King regulator deffo makes difference to mine. We regularly see 30-32 mpg on a run fully loaded. But if I'm in a rush I can easily get that down to 22-25 mpg :lol:
I've got 1776, Weber 40's, 1303s box and 195/60x14 rear tyres. Mine was set up on a rolling road so although it was a while ago it's still fairly spot on.
Here you go
http://www.dellorto.co.uk/shop/car-acce ... ator-67mm/
Hopefully they've sorted out the instructions because they showed the in/out the wrong way round when I bought mine :lol:

I have a filter king also, anti clockwise to reduce pressure? I didnt need to change mine as it was about 3psi out of the box
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Re: What are the main factors affecting real world mpg on a bus?

Post by flatbeat » Thu Nov 10, 2016 2:09 pm

Filter Kings are meant to be set at 3psi at the factory but I've regularly come across them producing 5 psi which will cause all sorts of probs with Webers...that like 3.5 psi but will cause even more probs with Dells that really don't like more than 3 psi.
Packed a few belongings and headed out to Pirates Cove. In my buddy’s old grey Kombi we rolled until the gas got low.....

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Re: What are the main factors affecting real world mpg on a bus?

Post by flatbeat » Thu Nov 10, 2016 2:10 pm

Filter Kings are meant to be set at 3psi at the factory but I've regularly come across them producing up to 5 psi which will cause all sorts of probs with Webers...that like 3.5 psi but will cause even more probs with Dells that really don't like more than 3 psi.
Packed a few belongings and headed out to Pirates Cove. In my buddy’s old grey Kombi we rolled until the gas got low.....

1965 11 Window aka 'Rustina'.
1961 Beetle.


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Re: What are the main factors affecting real world mpg on a bus?

Post by flatbeat » Thu Nov 10, 2016 2:11 pm

wizard 1066 wrote:What fuel pressure regulator are you using, had mine on the rolling road and they said the idle jest were running rich and it might have to do with the pressure, got twin 34 on it.
34's actually prefer as little as 2 psi....
Packed a few belongings and headed out to Pirates Cove. In my buddy’s old grey Kombi we rolled until the gas got low.....

1965 11 Window aka 'Rustina'.
1961 Beetle.

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