XUD Normally Aspirated tuning

Why? Assuming a correctly matched transmission and don't mind the motorbike engine exploding at some point?

Christian.

Hmm, you could have a point there - not sure if the 2.5TDi (that's what it is - direct injection) was ever used in anything Pug. And I'm guessing it's a completely different 2.5 litre lump to the 2.5D in the Relay/Boxer.

Peter

Actually I am not.

53 MPH (or 88!) have nothing to do with it. If you take any object at all of any size, it always takes 4x the power to push it through the air at twice the speed. Or if you prefer the drag increases with the square of the speed.

What I said was that any two vehicles with the same frontal area / shape do NOT have the same drag. A longer one really does have less. So a train has less drag than a single carriage at the same speed. In both cases it will take 4x the power to double the speed.

The truck being bigger (better reynolds efficience) and longer (better drag coeficient from a given frontal area) has more drag than the van. BUT less so than would be expected by frontal area alone. The truck is MORE efficient square foot for square foot as far as drag is concerned.

And a flat plate (very short truck) with the samer x section as the block has a worse cd than the block.

And two blocks together, have a better cd than the one by itself, and is the long truck!

Sorry but the truck does not care what package your 200bhp comes in. Gas turbine, electric motor, bike engine, lots of hampsters, clockwork etc. BHP is a direct measure like kw, or volts, or inches.

Now just because you choose to not believe a bike engine will not do the same job does not make you right! Physics says otherwise.

Because physics and facts upset him! You can tell because of all his carefully explained reasoning! In reality it would accelerate harder since you just dumped half a ton of useless gutless noisy pig iron...

He "likes" to think his macho gutless but heavy diesel engines make more power than a pidly little bike engine! Even if he is wrong.

When it comes to propelling a vehicle torque is meaningless unless you know the rate of torque production. Because what we really need to know is torque available at the wheels, and this would by definition be the same at the same power!

What sort of transmission would enable a fragile thing like a bike engine to pull 40 tons of artic?

Halmyre

Its hypothetical, but if you insist... First of all we are talking about

200bhp so maybe not an artic but whatever truck has 200 hp...

Connect the bikes gearbox output shaft directly to the gearbox input shaft on ya truck. Nothing will break then since the bike is designed for the level of torque it makes and so is the truck gearbox. It might not last

200,000miles but it would last a few months at least.

A simple gearbox.

If the bike engine is capable of producing 200bhp without disintegrating, then a gearbox will be capable of converting that to whatever speed/torque combination is required. The bike engine will have loads of revs and low torque, which the gearbox converts to low revs and high torque required to drive the truck.

The reason it won't work in practice is that the 200bhp bike engine will be unable to operate continuously at such a high power, particularly as the truck will be going slowly and not producing the sort of airflow over the engine required for adequete cooling. It will work for some time, until the bike engine expires at being expected to run at high power for so long. In a bike application, the full power is only used for brief periods of acceleration. To maintain even a very high speed requires only a fraction of its peak power, unlike the situation when driving the artic.

Christian.

True generally but airflow isnt the reason since they are all water and oil cooled nowadays! Leon moss (dead now unfortunately) tested a 750 on the dyno nat peak power for 24 hours once... Too see what wore out on a production racer. When stripped nothing measurable... So it may go for a surprisingly long time.

Lack of torque.

Ah, more efficient. Makes sense now.

Err 420BHP/1850lbft?

...at 1200RPM....

Lets do it simply... You have a big heavy slow engine that makes say 100 bhp, You have a tiny motor that is ten times smaller, makes the same power at ten times the rpms...

The tiny motor makes ten times less torque. But revs ten times higher.

Now your "big" engine makes say 100lb ft torque. Your small engine makes ten times less! Only 10lb ft torque...

To get the same road speed in each gear the small engine needs a ten to one gear ratio... So now both hit rev limiter at say 30mph in 2nd gear.

But to do this the smaller engine needs ten times the rpm so is geared ten times lower.

10 LB FT x ten times the ratio = 100 lb ft. SAME RESULT as the big engine turning slowly.

After this if you dont get it I suggest you may take up football as a career.

burgerman

Sorry I would have replied sooner, I was just enjoying elsewhere in the thread! :)

You can do pretty much the same changes to a diesel as you can to a petrol - induction, exhaust, cylinder head, camshaft - except it's rarely done because turbocharging is much cheaper per gain.

Unfortunately, this XUD has a mechanical injection system and in the absence of a turbocharger, there's not much you can do here.

A turbocharger, or XUDT conversion, is the most sensible suggestion I can make... Or trading it in for a more powerful one?

Yes I do, see above ! I never mentioned gearing !

Yep, once gearing is factored in. You never mentioned that in your original post.

...which was never mentioned.

Yes, I know this :)

But the torque at the wheels is the same ! There is no lack !

Once you've stuck a gearbox on the end, you can multiply the torque as you wish. So the bike engine can make the same torque at the wheels as the truck engine !

Aye, but a fair few of the miles my van does (between home and depot, and between depot and the area the deliveries are) are on the open road, where having that bit more power would reduce the stress on the engine, and probably save fuel. That's where Merc CDIs are good - you get 3 different levels of tune (80/110/130bhp) for the same size engine, which, in theory, should all consume the same amount of fuel when idling or doing stop-start work, so I'd go for the 130 every time. If I could get one at a good price. For the current round I'm considering getting a MWB low-roof 213CDI (2.8 Tonne GVW compared to 3.5T for the 313CDI) or even a SWB, as my SWB Master manages fine size-wise, and the 2 series Sprinters are cheaper to start with, plus less desirable than the 3s, so probably more chance of a decent discount, especially with a low roof SWB/MWB one. Bloke I was chatting to got offered an imported brand new 313CDI LWB for £13k, and someone else I deliver to got his 316CDI MWB low-roof brand new for £23k, so I reckon I could get a 213CDI MWB low-roof for around 13-14k if I'm lucky.

Aye. I don't want something that's just going to be stressed on the main roads where progress needs to be made, which will just end up using more fuel anyway...

Peter