Interesting experiment: Duc V-One

[gregp]

This is an interesting (apparantly successful) experiment:
http://thekneeslider.com/archives/20...0cd5f9e191%2C0

[gregp]

I am very surprised by the lack of comment on this post....

[gregp]

Without clicking on the link, it is a 2 valve Ducati, modified to run on one firing cylinder, and the other modified to be used as a supercharger. This single cylinder configuration makes more HP than the standard V-twin configuration.

[Paul_E_D]

I read through the thread. I'm not qualified to comment, other than I'd like to think a supercharged single cylinder roadracer could weigh under 350 wet... THAT would excite me.

[DuncanMoto]

I'm wondering what kind of mileage that thing would get.

[csmutty]

I'd like to see the cases cut in half on this motor so I can see how it works up close and personal.

[RoyalewitCheese]

i think its pretty cool. i would never do that for an extra 15 horse and all that clutter all over the bike.

but i do think its sick

[Kurlon]

I'd like to see the cases cut in half on this motor so I can see how it works up close and personal.

You wouldn't see much exciting, from the heads down it's bog standard Duc VTwin. The only change is the vertical cylinder has it's head reworked so it's a 310cc air compressor feeding a storage tank.

[gregp]

Do you think that the valve train runs double speed in the charging cylinder?

[csmutty]

Do you think that the valve train runs double speed in the charging cylinder?

Probably. All it would require is a cam.

[joeswamp]

It's interesting, but I'd be really surprised if it were better than hopping up the engine in a conventional way. Piston engines are so highly developed that engineers have tried almost all the big ideas, you've gotta figure someone's researched this concept rigorously (probably 50-60 years ago) and concluded that the benefits weren't worth the trouble.

[Danz19899]

i dunno for whatever reason I'm skeptical of this. Just doesn't make sense in my mind, I'd love to see a dyno test to confirm this.

Just seems odd that a single cylinder can make that much power compared to the twin. The other cylinder as a pump would be a huge waste of energy IMO but what do I know lol

[Paul_E_D]

Probably. All it would require is a cam.

No cam on that head. Just one way reed velve like a 2 stroke...

[brady]

i dunno for whatever reason I'm skeptical of this. Just doesn't make sense in my mind, I'd love to see a dyno test to confirm this.

I'm with you there, and let's add the 2500rpm higher redline? That really doesn't make sense to me. Aren't reciprocating mass and valvetrain usually the limiting factors? Have either of these changed that much, if at all here?
[paging Graham]

[Paul_E_D]

I'm with you there, and let's add the 2500rpm higher redline? That really doesn't make sense to me. Aren't reciprocating mass and valvetrain usually the limiting factors? Have either of these changed that much, if at all here?
[paging Graham]

See above post. There is NO cam/valve gear on the rear cylinder. That's how he raised the rev ceiling.

[obsolete]

I'm pretty ignorant on the timing of the strokes normally for that bike but it seems kinda weird that there's probably a time that the combustion cylinder is on the intake stroke and the supercharger cylinder is trying to compress air. I know that momentum will carry the pistons through the gap in power but it does seem like that would be more parasitic than beneficial. But I have no clue really, just my impression.

[Kurlon]

Couple items:

1) 620s are in a pretty tame state of tune out of the box, factory cam timing and ignition are set to keep the revs sane and get a wide, mellow power band. The engine can very easily survive higher revs but you have at least tweak the cam timing to make any power doing so.

2) It's a 'single' with perfect primary balance thanks to retaining all the reciprocating bits of a 90 degree twin, so it'll spin up with less vibration than a MX'er and it's counter balancer. The Supermono used the same principle but replaced the slave piston with a pivot arm to reduce overall weight.

3) The bike isn't supercharged at all times, the slave cylinder builds pressure in a storage tank. It's only when you go WOT that the bike uses that built up air pressure to put the bike into boost. It's kinda like a hybrid, if you're not at WOT you're building up temporary stored go juice. Hit WOT and you get to burn it for a limited duration. That's how a cylinder of matching displacement can keep up with the other. Granted, setup right using reed valves it's moving twice as much air in theory operating on an effective two stroke cycle...

4) Friction in the slave cylinder can be reduced by going to a single ring setup, piston coatings, slightly looser bore, etc.

[brady]

good points, but:

1. the article says it's a a 2v 1000CC
2. understood
3. no mention of WOT, and looks like the compressed air tank is in addition to the constant supercharging effect: "the air tank under the seat, limited to 40 bars, which is good for a 10 second burst of compressed air when acceleration begins after which the blower's output kicks in." Looking at the intake plumbing in the photo below seems to verify constant supercharging as well. [PS: the builder does verify this in a comment down the page.] I still don't understand how a supercharged single can produce more torque than a twin of twice the displacement (peak torque excepted).
4. I understand the friction improvements possible, and it only has half the valvetrain, but aren't valvetrain rpms limited more by mechanics than total mass?

not trying to nitpick, just trying to understand all of the claimed improvements.

Couple items:
1) 620s are in a pretty tame state of tune out of the box, factory cam timing and ignition are set to keep the revs sane and get a wide, mellow power band. The engine can very easily survive higher revs but you have at least tweak the cam timing to make any power doing so.

2) It's a 'single' with perfect primary balance thanks to retaining all the reciprocating bits of a 90 degree twin, so it'll spin up with less vibration than a MX'er and it's counter balancer. The Supermono used the same principle but replaced the slave piston with a pivot arm to reduce overall weight.

3) The bike isn't supercharged at all times, the slave cylinder builds pressure in a storage tank. It's only when you go WOT that the bike uses that built up air pressure to put the bike into boost. It's kinda like a hybrid, if you're not at WOT you're building up temporary stored go juice. Hit WOT and you get to burn it for a limited duration. That's how a cylinder of matching displacement can keep up with the other. Granted, setup right using reed valves it's moving twice as much air in theory operating on an effective two stroke cycle...

4) Friction in the slave cylinder can be reduced by going to a single ring setup, piston coatings, slightly looser bore, etc.

[Kurlon]

Hrmmm... dunno why I thought it was a 620... d-oh!

So, theory says if you double the air pressure, you get twice the HP. In this case one cylinder is moving 1000cc of air every 2 RPM, the other is consuming 500cc every 2 RPM, so that on paper accounts for matching the HP output of the stock twin. Add in cam timing/alternate grind on the power cylinder, head work, etc and that should easily account for the additional 15hp observed. At partial throttle, the second cylinder doesn't need all the air the system can supply, so that would line up with his comment that it goes over 2 bars at partial throttle and would boost his claims of a near flat torque curve.

As far as the raised rev limit, the 1000ds is an oversquare motor, 94 x 71.5mm to be exact. The same bore and stroke as my ST3. Normal conservative rule of thumb says 4000'/min max piston speed for a cast piston, aka 8500 RPM red line, 6000'/min for a proper forged setup or 12800 RPM red line. Topping at 10k matches my ST3 and is well within the safe range for good pistons.

The valve train is normally the other limiting factor, as you have to fight valve bounce with stiffer and stiffer valve springs as the speeds go up and your cam profile gets more and more aggressive... Wait, this bike has Desmo valve operation, never mind. Twist it and enjoy.

[rbrais]

i dunno for whatever reason I'm skeptical of this. Just doesn't make sense in my mind, I'd love to see a dyno test to confirm this.

Just seems odd that a single cylinder can make that much power compared to the twin. The other cylinder as a pump would be a huge waste of energy IMO but what do I know lol

I would think that a turbine supercharger would be much more efficient and lighter. Remove the rear cylinder and stick it there.

[obsolete]

It really sounds like the type of thing that non-efficient engineers love. Basically a Rube Goldberg machine to get minimal gains while normal performance enhancing methods would have done just as good with less effort/cost. It's cool and interesting but I dunno about practical or better.

[BluGixxer]

I think its awesome, the best thing I think about the whole general idea is the vibration reduction, you can always throw a different style super charger or blower, make it lighter and quicker and all that, but using what's there and improving it , having the second cylinder as a counter balance to get rid of vibration,it just kinda fits, its already there, so use it, besides blowers are more efficient by natural design , more power that you don't need and can't use on the street, awsome !!!!
I want to get blown !

[xsiliconkid]

It's interesting, but I'd be really surprised if it were better than hopping up the engine in a conventional way. Piston engines are so highly developed that engineers have tried almost all the big ideas, you've gotta figure someone's researched this concept rigorously (probably 50-60 years ago) and concluded that the benefits weren't worth the trouble.

A DS1000 with hi compression pistons and race cams will get 112Hp to the rear wheel. And, I bet the more important torque curve looks better without the need for higher RPM's to get the HP.

[obsolete]

I think its awesome, the best thing I think about the whole general idea is the vibration reduction, you can always throw a different style super charger or blower, make it lighter and quicker and all that, but using what's there and improving it , having the second cylinder as a counter balance to get rid of vibration,it just kinda fits, its already there, so use it, besides blowers are more efficient by natural design , more power that you don't need and can't use on the street, awsome !!!!
I want to get blown !

More balanced than what? It's already a twin.

[Kurlon]

A DS1000 with hi compression pistons and race cams will get 112Hp to the rear wheel. And, I bet the more important torque curve looks better without the need for higher RPM's to get the HP.

Actually, that was part of the gains on this unit, very VERY broad spread of power by using higher boost at lower RPMs / throttle. The higher RPM redline is just a bonus of using your own ECU and tossing the overly restrictive factory setup. This is a race bike after all.