The BSA A7-A10 Forum

Bikes, Pictures, Stories & more => Chat, Offtopic, Meetings & Everything Else => Topic started by: MikeN on 14.05. 2010 22:26

Title: fuel consumption and performance
Post by: MikeN on 14.05. 2010 22:26
I was thinking. In the 50's and 60's a typical medium size family car,like an Austin Cambridge or Cortina or something would trundle along and return about 25-30mpg (imperial gallons).A smaller car like a Morris minor or A35 maybe 35-40ish mpg. A typical high performance motorcycle of the period like an BSATri/Norton etc twin would easily out perform these cars and still average 60-70mpg.
 Nowadays with improvemnts in design a typical medium size car can do 40-50mpg and a small one can do 50-60mpg or even more.
With this in mind, i would expect a modern sports bike ,(whatwhat ever the present day Japanese equivelent of the Road Rocket or Bonnie is), to be returning around 100mpg.
I dont know anything about modern bikes,but I suspect this is not the case.if not .Why?
Mike
Title: Re: fuel consumption and performance
Post by: Triton Thrasher on 15.05. 2010 06:18
.if not .Why?
Mike

Because fuel economy is not a big selling point for sports bikes.
Title: Re: fuel consumption and performance
Post by: MikeN on 15.05. 2010 17:01
Im sure, but then I doubt anyone bought a Bonneville with economy in mind either.
And yet it would still have been way faster and considerably more economical than a car of the time.
Title: Re: fuel consumption and performance
Post by: Triton Thrasher on 15.05. 2010 17:51
Ride a Bonneville fast and it will do about 40mpg. That's not fantastic economy.

A modern bike doing "fast Bonneville" speeds might manage 40mpg too.
Title: Re: fuel consumption and performance
Post by: MikeN on 15.05. 2010 21:00
Ride a Bonneville fast and it will do about 40mpg. That's not fantastic economy.

A modern bike doing "fast Bonneville" speeds might manage 40mpg too.

OK ,Thats the point im trying to make. You say an old Bonneville has similar fuel consumption to a modern bike ridden at Bonnie speeds.
Whereas im pretty sure a modern car will use a lot less fuel than an equivelent car from the 50's at similar speeds .
Or, it can also go considerably faster and still be using less fuel than the old car.
Title: Re: fuel consumption and performance
Post by: duTch on 14.01. 2014 23:19

 Did a search for 'fuel consumption', and this came up.

  At the end of '76, I did a impromptu trip Brisbane to Sydney on my '58 R.Rocket. It was when there were fuel strikes/shortages, so I strapped a gallon oil can full on the back.
 Did about 65-70 mph all the way,where possible (was just before radar guns !), and on the return trip I filled up just out of Ballina, and made it back to Holland Park, (almost central Bris.) I think was just on 200 miles so works out about 65 mpg (?), with I think a 3-1/2 gallon tank.

  Now to current bike,(A10 Plunger, 7.25 cr, S/R head) the tank holds 13.75 litres, a bit smaller than it should be, and I have to fill up about every 100 miles (+10% for inaccuracy in speedo-1620 with 2.0metre wheel circumference).

 Unless all my conversions are out of whack that = ~ 40-45mpg

 This doesn't seem good enough- slightly better on 98 than 91, but roughly the same, and performance too.

  Any clues? is fuel gone to crap that much??
Title: Re: fuel consumption and performance
Post by: muskrat on 15.01. 2014 03:46
It sure has Dutch.
I'm getting 50 MPG out of the A7 sitting on 60 MPH. In about '81 the same bike got me at least 60 MPG.
On a good day I get 40 MPG out of the cafe and 28 *eek*MPG out of the rHonda phore. 20 MPG out of the 4.2Lt 6 cyl Ford ute.
12 MPG out of the A7SS on methanol  *eek*.
Price for 98 here is $1.75/Lt = $7.95/gal
Cheers.
Title: Re: fuel consumption and performance
Post by: terryg on 15.01. 2014 07:55
Hello Musky - so you're paying about half the UK petrol price AND getting a better ration of sunshine.  I'll try not to think about that for too long.
Title: Re: fuel consumption and performance
Post by: KiwiGF on 15.01. 2014 10:15
My A10 (30hp?) before new 376 carb 50mpg keeping below 70mph, after new carb 60mpg, my 2010 Triumph 675 Street triple (108hp) ridden sensibly ( which is hard to do) 50mpg, but it does a lot less ridden fast   *lol* *wink2*

My 1988 honda GB500TT (40hp) which I sold a few years ago to buy the A10 did around 80mpg even when thrashed. Is that more than the 500 goldie it was imitating?

My 1999 1400 v twin suzuki (60 hp?) does 60mpg when ridden sensibly but weighs a LOT.

Conclusion? Modern bikes are around that use much less fuel than 60 year old bikes with similar hp, but hardly anyone buys them?
Title: Re: fuel consumption and performance
Post by: unclerob on 15.01. 2014 10:24
Back in the 80's I used an A10 for commuting to work ...a 40 mile trip...and used to easily get 60mpg but I think the difference then was how much easier it was to get about. I used to try and do the whole trip without coming to a stop and putting my foot down....and often managed it!
Doubt you could do that nowadays...
Title: Re: fuel consumption and performance
Post by: Ethelred on 15.01. 2014 10:25
Interesting what Musky and Dutch are saying about the drop off in economy because of modern fuel. It makes modern car fuel economy seem even more impressive, or perhaps it's just formulated to work better with fuel injection.
If economy was an issue with bikes then someone would have built a modern diesel multi by now.
Title: Re: fuel consumption and performance
Post by: bsa-bill on 15.01. 2014 14:52
I'm with Dutch and unclerob - can only be our modern fuel

Used to get 60 mpg two up on the Flash in the 60s now much much less probably 40 - 45
Title: Re: fuel consumption and performance
Post by: Butch (cb) on 16.01. 2014 12:12
My Picanto does pretty much the same mileage as my larger bikes. And if you'll excuse the mixed units that's around 10 miles (what my speedo/odo reads in) per litre (what they sell our gasoline in).

Certainly emissions kit has had an effect.

Talking mpg, my little V50 manages maybe around 55, and my A10 really ain't that good. The Sportster is not too bad. I'm sure that my '79 750 Bonnie in the day and despite being absolutely hammered everywhere, all of the time, would manage 60 - 65.

Even accepting the high performance of modern motorcycles I think that the mileage they can manage is absolutely shocking. I'm thinking that Honda have produced something quite recently focussed on economy using effectively half of one of their car engines. But it still gives, to my mind, poor returns.

As things stand I don't see that the modern motorcycle can really be viewed as serious transport.
Title: Re: fuel consumption and performance
Post by: KiwiGF on 16.01. 2014 23:03
Another factor in the mix....Im going to Auckland jn a weeks time to see the classic bike show. Abouf 2000km round trip for my street triple. I estimate 120l of petrol needed cost at circa $250 nz, and 20% of my tyres worn out which as they are circa $600 the pair works out  at a cost of $120nz....

So the cost of tyres makes modern sports more expensive to run than cars and older bikes  as well......

But a modern tyre has FAR more grip than a skinny wm2 tyre!
Title: Re: fuel consumption and performance
Post by: duTch on 17.01. 2014 09:41

 Ok just to confound things a little, since owning my Guzzi (850T), from '92, I've consistently ranged 200 miles (yes, miles- it came from the US) till I hit reserve, and it takes 20 litre to refill from there.

 Using around town (reluctantly), it's down a bit, but did a trip up the coast last weekend, and as per usual right on cue- 200 mi>reserve..... 10 mile per litre (16 k/l).
 
 So that kind of throws theories to the wind...??  (I usually run on BeePee 98 since Super dissappeared)
Title: Re: fuel consumption and performance
Post by: bsa-bill on 17.01. 2014 10:51
Just had a thought (happens now and then)

Aerodynamics, not to many of us here use fairings as far as I can see in pictures, and they do make diiference as you find the first time you brake with one fitted.
Doesn't explain the difference from then ttll now though    and modern bikes are usually faired to some extent - it's a factor though     
Title: Re: fuel consumption and performance
Post by: Briz on 17.01. 2014 11:15
A lot of you guys are comparing apples to oranges. Yeah, modern sportsbikes make comparitively poor gas mileage, but they make 4 times the power! You cant make power without burning fuel.
If you built a mega-strong A10 and boosted it to make 150hp, that'd get lousy mileage too.
And nobody buys something like a huyabusa as serious everyday transport!

That said, there is often little rhyme or reason to mileage, and like horsepower figures, owner estimates are often...ummmm...imaginative! Friend of mine once had an early 70s Lincoln Continental; 7.6ltr big block and the weight of the titanic. Reckoned he got 22mpg. Yeah right!.
Title: Re: fuel consumption and performance
Post by: KiwiGF on 17.01. 2014 11:23
bsa bill, your onto it very likely, aero dynamics might very well be a factor here, cars have progressed a lot with aerodynanmics, but maybe bikes not as much? There is only so much one can do to improve the aerodynamics of the average biker, and of course fairings are generally only fitted to the modern sporty bikes which are not meant to be good on fuel anyway.

The BMW range might give a clue as to why bikes have not progressed as well as cars in terms of fuel consumption? Have they progressed?

Re modern engine tech, I've recently done the valve clearance job on my triumph street triple and that was a real eye opener for me, requiring moving lots of bits out of the way to do the job, it has no carbs just throttle bodies with computer controlled injectors, half the 8 hour job (required every 8000 miles) was unplugging and re connecting the engine electrics!

Title: Re: fuel consumption and performance
Post by: Butch (cb) on 17.01. 2014 14:25
Aerodynamics certainly becomes a factor at higher speeds – somewhere beyond 60/70 per I’d guess. I took my ZRX (or whatever it is – it’s the Lawson looking thingy) down to Strasbourg last year for a few days riding the twisties out that way. Out on the mountain roads with significant changes in incline and all types of curve which keep speed down but running an awful lot of throttle in lower gears the usual mpg wasn’t much compromised. The run there and back from Calais (around 400 miles each way) taken at high speeds – sometimes around 120/130 indicated for stretches really hoovered up the gas.

I’d still expect a mid-sized bike with good performance to be considerably better than they are.
Title: Re: fuel consumption and performance
Post by: chaterlea25 on 17.01. 2014 21:05
Hi All,
""Friend of mine once had an early 70s Lincoln Continental; 7.6ltr big block and the weight of the titanic. Reckoned he got 22mpg. Yeah right!.""

Reminds me of the story about the forecourt attendant who asked the owner of such a beast
"can you turn it off so as I can catch up!!!!  *yeah* *yeah* *yeah*

John
Title: Re: fuel consumption and performance
Post by: duTch on 08.02. 2014 00:23
  Read through again, missed some bits, Kiwi- maybe I need a 376, instead of my 389...¿
It's interesting to see how other bikes consume, but I was really only curious about comparing A10/7 consumption, bikes of similar specs, like there's a difference between my plunger and the Road Rocket, 357/356 cams, and 7.25/8.~ pistons, and crank- wheel sprocket ratio(?), but basically same.
 Also my Gutzi comparison is with only itself over a 20 year time frame, a couple of weeks
ago did a trip to Tamworth, ~380 miles each way, and still had the same consumption rate as always- 200 miles/20 litres tank, on cue....!
       *beer* *beer*
Quote
Back in the 80's I used an A10 for commuting to work ...a 40 mile trip...and used to easily get 60mpg but I think the difference then was how much easier it was to get about. I used to try and do the whole trip without coming to a stop and putting my foot down....and often managed it!
Doubt you could do that nowadays...
*eek*

    Yeah sometimes I forget to do that too....
Title: Re: fuel consumption and performance
Post by: Triton Thrasher on 08.02. 2014 10:03
Hi All,
""Friend of mine once had an early 70s Lincoln Continental; 7.6ltr big block and the weight of the titanic. Reckoned he got 22mpg. Yeah right!.""

Reminds me of the story about the forecourt attendant who asked the owner of such a beast
"can you turn it off so as I can catch up!!!!  *yeah* *yeah* *yeah*

John

I had a 1967 Mercury coupe, with probably similar 6.4 litre V8 Ford engine. You could get 14 mpg.