Ducati Sporting Club UK > General > Idle Chat > Twin Pulse

[andyb]

Nobody posted anything about the fact that the GP team are going to use the twin pulse engine at Assen? They tested yesterday at Cataluna,

[dickieducati]

yeah quicker lap times than during the race i believe

[andyb]

bttt, spose its a bit too significant a move from Ducati for us to comment, best we carry on talking about nail bombs etc....
....that didnt take long!

[phillc]

I'm not an expert either, but from what I can see on the Ducati Website the engine has an "irregular firing order."

A little websearch through Google revealed this article:

http://www.motorcycledaily.com/19feb...technical.html

"
CAN YOU EXPLAIN HOW THE TWINPULSE WORKS?

Although it has four pistons, the Twinpulse maintains the typical characteristics of a twin-cylinder engine. Unlike a conventional four-cylinder unit, which has four distinct combustions for each complete cycle – that is, two turns of the crankshaft – the Twinpulse only has two. This is obtained by simultaneous combustion in the two cylinders of the same bank. The effect, which we have called Twinpulse, cannot be obtained by a four-cylinder engine by simply changing the firing order; it is necessary to design the entire engine with this function in mind, because many internal organs, which are stressed in a different and more ‘traumatic’ way, must be built to the right size."

Same article has lots of good info on Desmosedici and Testastretta engines.

Phill

[Edited on 16-6-2004 by phillc]

[dickieducati]

twin pulse engines fires like a v twin. ie 2 cyliders fire together then the other 2 fire together. they should give the same traction characteristics as v twins.

at the moment the engine fires 4 times per cycle each cylinder firing one after the other.

i think it may have been a power issue when they first tested the twin pulse a year or so ago.

should sound like a proper ducati too.

[antonye]

The reason that the 4 cylinders can't do it is because the pistons on the crank are offset with each other, so they are not able to be paired and fired simultaneously.

[andyb]

The twin pulse is virtually using the four cylinders as a pair of two, just like bolting two v twins together. DEickies right, should give the characteristics of the v twin we've come to love.

The current model engine uses the four cylinders as individuals, firng one after the other, bit like a vfr, rvf honda.
Thats why it screams.....

If you remember, they tried both engines at the beginning of the desmosedici project and opted for the latter.

So wonder what theyve developed or changed to swap? Never the less, its either a gutsy move, or one of desperation.....

[andyb]

Funnily enough Antonye, i disagree with you there.
On inline fours there are really only two firing orders 1243, of 1342. Either way, the pistons are paired, 1 and 4, 2 and 3.

On each pair one being on the firing stroke the other on the exhaust, and so on.

So in theory they could pair the firing strokes up, outside two, inside two...... etc

[antonye]

Originally posted by andyb
Funnily enough Antonye, i disagree with you there.
On inline fours there are really only two firing orders 1243, of 1342. Either way, the pistons are paired, 1 and 4, 2 and 3.

On each pair one being on the firing stroke the other on the exhaust, and so on.

So in theory they could pair the firing strokes up, outside two, inside two...... etc

It depends on the position of the conrods on the crank - the offset angles they use - which in turn affects primary balance.

You would only be able to pair the pistons in a four if they were at 180° to each other - then you're into a parallel twin type of arrangement. As you say, pairing the outer cylinders (1+4) with the inners (2+3) would mean you didn't suffer from latitudinal forces.

If your crank uses a 90° setup, then you wouldn't be able to match pairs because one piston would be at TDC as the other is at BDC. I believe this is the norm for 4 cylinder production bikes?

Firing order doesn't really matter - it's the alignment on the crank.

Interestingly, the Honda RCV is a 5-cylinder split in a 2-3 V-arrangement. The bank of 2 cylinders have a different bore (larger) to the bank of 3 cylinders to ensure that they two halves weigh the same, thus providing perfect primary balance.

The reason for splitting it is because the frontal area of a 2-cylinder bank is much smaller and it makes the bike more streamlined.

However, I believe this isn't the first time such an arrangement has been used, but the origins of it escape me.

Clever stuff!

[andyb]

Sadly, this sort of thing excites me...
Wouldnt it be good to have this sort of imput at the functions where we meet the riders?

What about meeting the top mechanics and having an imput from them?