Diesel motorcycle. Would you buy one?
Discussion
There is a new derv bike coming out in 2009 i am reliably informed.
It promises a turbocharged, 660cc parallel twin engine, with 8 valves, twin-cams and 100 bhp.
Very low emissions via 2 cats. and 75 mpg average is mentioned.
But would you buy a diesel bike?
It promises a turbocharged, 660cc parallel twin engine, with 8 valves, twin-cams and 100 bhp.
Very low emissions via 2 cats. and 75 mpg average is mentioned.
But would you buy a diesel bike?
Edited by Beemer-5 on Monday 14th April 10:56
In principle, I’d have no problems with a diesel bike. There is more energy in diesel than in petrol so, on paper, it’s a better fuel. (It’s just harder to get at that energy.) The issue would be about how the power/torque is delivered and how usable the bike is. The problem with a small turbo charged diesel engine is that while it may have a high torque figure, the spread of torque is traditionally very small and thus will be difficult to ride without a very large number of gears. Perhaps the answer is to attach the engine to a CVT gearbox but that may end up too heavy.
I would have thought that the spread of torque would have been no more an issue than in cars tbh, five or six well spaced gears should be able to keep the bike in the torque curve easily enough.
Personally I think it sounds great, a 75mpg super-commuter would be right up my street. My only concern would be poor throttle response from the turbo diesel.
Personally I think it sounds great, a 75mpg super-commuter would be right up my street. My only concern would be poor throttle response from the turbo diesel.
I'd have one as a torquey tourer come commuter I guess but would miss the noise of the sporty petrol engine. The last time I tried to separate my commuter from my sports bike left me disappointed with both and combining the roles to me blade so how long I'd be happy with it would be anyone's guess.
I think it could be good in the right circumstance... Loads of torque, geared right to use it instead of reving loads and it could be quicker and more flexible than a lot of bikes out there.
It'll be the price that decides it though...
Who cares if you get 75mpg instead of 40 mpg ?
Diesel (1.15 per litre * 4.5 * 6000)/75 = 414 spent on fuel
Petrol (1.10 per litre * 4.5 * 6000)/40 = 742 spent on fuel
So, in a 6000 mile year you will save £328... but I bet it'd cost more to buy in the first place and go through more rear tyres because of the torque... so that would eat into the economy further.
Basically, as a money saving exercise I think it will be a false economy... Now, if they can make it a special fun wheelie machine, that is comfortable and has good tank range, I'd be interest.
It'll be the price that decides it though...
Who cares if you get 75mpg instead of 40 mpg ?
Diesel (1.15 per litre * 4.5 * 6000)/75 = 414 spent on fuel
Petrol (1.10 per litre * 4.5 * 6000)/40 = 742 spent on fuel
So, in a 6000 mile year you will save £328... but I bet it'd cost more to buy in the first place and go through more rear tyres because of the torque... so that would eat into the economy further.
Basically, as a money saving exercise I think it will be a false economy... Now, if they can make it a special fun wheelie machine, that is comfortable and has good tank range, I'd be interest.
hiccy said:
I would have thought that the spread of torque would have been no more an issue than in cars tbh, five or six well spaced gears should be able to keep the bike in the torque curve easily enough.
Personally I think it sounds great, a 75mpg super-commuter would be right up my street. My only concern would be poor throttle response from the turbo diesel.
I think that's my point. Acceleration is a key feature of any bike over about 125cc, even for bikes traditionally branded as tourers, where, with cars acceleration is less of an issue. The extra weight a car carries (compared to a bike) means that small petrol cars have poor acceleration anyway so the issues of a small torque spread from a diesel engine can be masked by the high torque output. Petrol or diesel, you still get pretty poor acceleration.Personally I think it sounds great, a 75mpg super-commuter would be right up my street. My only concern would be poor throttle response from the turbo diesel.
With a bike, even a 400cc petrol engine (never mind a 600cc petrol), will give a broad enough spread of power due to the phenomenal rev range that acceleration is good with even a relatively small number of gears. (If you can count 6 as a small number of gears.) If the small diesel is restricted in revs (as most diesels are) then you will not have that big spread thus will need more gears. It’s the same way that big twins offer more torque but less revs than IL4s but with a small diesel, I expect that different would be even more pronounced.
With a 5,200 rpm limit and a predicted 180 kgs dry weight, it shouldn't need more than 6 gears.
100 bhp is Kawasaki Z1000/Z1100 power, remember, from not so many years ago and they were considered to be very fast!
Of course nobody is going to choose it over a GSXR1000, or even R6, but i think as a commuter/tourer it would be great.
The easy 300-mile tank range would make it 'quick' on a long, A to B journey!
My Kawasaki Z1 had 82 bhp and was considered fast, this thing will be faster yet do 75 mpg and the in-gear shove will be huge.
100 bhp is Kawasaki Z1000/Z1100 power, remember, from not so many years ago and they were considered to be very fast!
Of course nobody is going to choose it over a GSXR1000, or even R6, but i think as a commuter/tourer it would be great.
The easy 300-mile tank range would make it 'quick' on a long, A to B journey!
My Kawasaki Z1 had 82 bhp and was considered fast, this thing will be faster yet do 75 mpg and the in-gear shove will be huge.
Beemer-5 said:
With a 5,200 rpm limit and a predicted 180 kgs dry weight, it shouldn't need more than 6 gears.
100 bhp is Kawasaki Z1000/Z1100 power, remember, from not so many years ago and they were considered to be very fast!
Of course nobody is going to choose it over a GSXR1000, or even R6, but i think as a commuter/tourer it would be great.
The easy 300-mile tank range would make it 'quick' on a long, A to B journey!
My Kawasaki Z1 had 82 bhp and was considered fast, this thing will be faster yet do 75 mpg and the in-gear shove will be huge.
But the issue is where within the 5200 rpm range there is usable torque. From my turbo diesel car experience a max rev range of 5200 actually means that your going to have nothing below about 2000rpm and little above 4500 rpm giving a usable range of only about 2500rpm.100 bhp is Kawasaki Z1000/Z1100 power, remember, from not so many years ago and they were considered to be very fast!
Of course nobody is going to choose it over a GSXR1000, or even R6, but i think as a commuter/tourer it would be great.
The easy 300-mile tank range would make it 'quick' on a long, A to B journey!
My Kawasaki Z1 had 82 bhp and was considered fast, this thing will be faster yet do 75 mpg and the in-gear shove will be huge.
An 80bhp slow revving petrol engine (such as a twin) will max a say 8500rpm (and that’s very slow) but will also pull from about 2000rpm but can pull cleanly all the way to the red line giving a usable rev range of 6000rpm, more than double that of the diesel.
This means that, in order to get a reasonable spread of speed (say from 0 to 140mph) the diesel will either have to be very high geared making slow speed acceleration difficult or the rider will have to live with the fact that the engine comes ‘off turbo’ every time there is a change of gear. (Or there will have to be a lot more gears on offer.)
Edited by black-k1 on Monday 14th April 12:46
Who's making it? What is it?
Can see the market if it's a courier/commuter special or an off road trail/enduro type but not for much else.
It might be worth noting that the army have been inviting tenders for despatch bikes for years now that run on "nato standard fuel" i.e derv' to you and me.
Can see the market if it's a courier/commuter special or an off road trail/enduro type but not for much else.
It might be worth noting that the army have been inviting tenders for despatch bikes for years now that run on "nato standard fuel" i.e derv' to you and me.
i think it'd be worth trying to see how it works. i like the sound of some turbodiesels, all you need is LOTS of turbo howl to cover the bag of spanners 
however unless they've finally cured the throttle lag diesels always seem to have i can see it being a pain in the arse to ride. it'll be like having 4ft of slack in your chain so you struggle to get the power on when you need it while cornering etc.
however unless they've finally cured the throttle lag diesels always seem to have i can see it being a pain in the arse to ride. it'll be like having 4ft of slack in your chain so you struggle to get the power on when you need it while cornering etc.
Turbo lag isn't much of an an issue, with a vehicle weighing so little.
A Caterham R500 Evolution has 250 bhp, from it's n/a 1998cc engine and has 'lag' all the way to 5,000 rpm! Nothing happens much, but the low weight, of 450 kgs, means that it doesn't really matter.
A bike weighing a tiny 180 kgs, but with 100 bhp, will be fine, what lag there is won't matter like it would if it was pulling 1,400 kgs.
A Caterham R500 Evolution has 250 bhp, from it's n/a 1998cc engine and has 'lag' all the way to 5,000 rpm! Nothing happens much, but the low weight, of 450 kgs, means that it doesn't really matter.
A bike weighing a tiny 180 kgs, but with 100 bhp, will be fine, what lag there is won't matter like it would if it was pulling 1,400 kgs.
dern said:
Beemer-5 said:
A Caterham R500 Evolution has 250 bhp, from it's n/a 1998cc engine and has 'lag' all the way to 5,000 rpm! Nothing happens much, but the low weight, of 450 kgs, means that it doesn't really matter.
How can an n/a engine exhibit lag?Gassing Station | Biker Banter | Top of Page | What's New | My Stuff