The Technical Questions Thread

[Matra et Alpine]

Takes more force to open valve, so the F1 developments on pneumatic open AND close proved that it took LARGE mechanisms to open. More than the weight of the cam and the opening control at the time didn't give a great advantage.
I expect to see this all revisited as modern ECUs enable engine designers to use valve overlap to adjust the effective compression ratio. Still fun things to be done at the top end of an engine
Renault persever using the high pressure hydralics already present for steering etc.


Back to the point re Desmo, it's a practical nightmare as the slightest variation in wear between the opening and closing surfaces means lash is introduced which can be catastrophic. Also, trying to do variable valve timing with Desmo is near impossible and requires LOTS of additional gearing/levers. Pneumatic is computer controlled and so varibale valve timing only needs to worry itself about the mechanics of opening and lket the computer/pneumatics close it when and as needed.

Desmo is like Porsche air-cooling. Retained LONG after it's benefits were lost due to marketing pressures. Not a great solution, but a Duc without Desmo woudlnt' sell Likewise a non V-twin Ducati porst bike is a no-no.
Going to be intresting what the response is regarding trellis frames.
Like Desmo, till now Ducati claimed that it was a great design advantage they had -- pure marketing BS

[Kitdy]

What about desmo on street bikes where pneumatics aren't allowed, do the benefits of VVT on their opposition outweigh the system? Has desmo VVT been done anywhere?

I am gonna have to look into these trellis frames.

Why aren't V4s used in some litrebikes but used in MotoGP?

It seems to me Ducati is a company stuck into the past and that their setup is inferior for litrebikes - hence they upped the displacement and had the rules changed like you said Matra. My buddy says their sportbikes handle better though, and I think that the 1098 is way better looking than any of the Japanese bikes so I am a bit partial to Ducati even though I typically like forward thinking companies.

I mentioned before, but why no direct injection on bikes yet?

[Matra et Alpine]

DIrect injection doesn't give much benefit over throttle body injection. Very short path from injector to inlet. Also injection has always had a problem that the much higher vibrations present in bike engines caused "chatter" of the injectors making them fail.

Re V4 it's about packaging. The V4 allows for a narrower engine. Frontal area is a BIG issue in bikes. Check out a V-twin Duc compared to competition and it looks about 25% narrower -- that's 25% less resistance WSB bikes have to based off a street bike and the out and out performance of a sportbike is now better met with straight 4s. Others have had V4s in the past and still one of my most favourite bike is the Honda VFR !

Nobody's tried to build desmo vvt afaik as the simplest of analysis points out the failings and difficulties. Desmo on street bikes is an "issue" that most Duc owners don't realise until it's service time ! Mate's have sold Ducs on rather than face the hundreds of £££s for a desmo service For looks and soudn they are great.

..... until you park an MV-Agusta F4 beside it .... or a Benelli triple


... handling .... well it so much depends on the rider .... having ridden with a Honda instructor on a Pan European while we were all on various sports bikes proved that point Duc's aren't particularly fast turn in bikes in street trim - certainly not an R1 or Gixxer .... also every one I've seen used in anger has a steering-damper to cope with the rake !!


EDIT: Aprilia RSV4 is a V4 road bike entered into WSB.

[NSXType-R]

What is the drag coefficient of a Lamborghini Reventon?

[LeonOfTheDead]

Originally Posted by NSXType-R

What is the drag coefficient of a Lamborghini Reventon?

I would say it's unknown since it's not included in the released technical data.

[NSXType-R]

Originally Posted by LeonOfTheDead

I would say it's unknown since it's not included in the released technical data.

It looks pretty damn unaerodynamic, kinda like the Countach, which is probably just a brick anyway. I thought of that when you brought up the exhaust pipe of the new Murcielago drop top. But then again, the F-117 bomber (it really isn't a fighter) has really bad angles and still flies. But then again also, it's fly by wire, so the computer interprets that stuff, I think.

All in all, it might be aerodynamic, it might not be.

[Matra et Alpine]

According to Evo the Reventon ....
"Wind-tunnel testing has resulted in improved air-flow through the openings all over the new bodywork and a drag coefficient down to 0.27 from the original 0.30"

[NSXType-R]

Originally Posted by Matra et Alpine

According to Evo the Reventon ....
"Wind-tunnel testing has resulted in improved air-flow through the openings all over the new bodywork and a drag coefficient down to 0.27 from the original 0.30"

That's quite good then. Thanks.

[fpv_gtho]

Originally Posted by NSXType-R

But then again, the F-117 bomber (it really isn't a fighter) has really bad angles and still flies. But then again also, it's fly by wire, so the computer interprets that stuff, I think.

All in all, it might be aerodynamic, it might not be.

It really depends on what you mean by aerodynamic. Producing lift or not producing drag? Something like the F-117 despite its shape still produces lift. The computer control and the fly by wire though keep it in the air becuse it'd be too unstable without it.

[NSXType-R]

Originally Posted by fpv_gtho

It really depends on what you mean by aerodynamic. Producing lift or not producing drag? Something like the F-117 despite its shape still produces lift. The computer control and the fly by wire though keep it in the air becuse it'd be too unstable without it.

The aerodynamic comment was directed towards the Reventon.

[Kitdy]

Why was the Miura's engine transversely mounted?

[f6fhellcat13]

Originally Posted by Kitdy

Why was the Miura's engine transversely mounted?

to save space

[Bob]

Originally Posted by NSXType-R

It looks pretty damn unaerodynamic, kinda like the Countach, which is probably just a brick anyway. I thought of that when you brought up the exhaust pipe of the new Murcielago drop top. But then again, the F-117 bomber (it really isn't a fighter) has really bad angles and still flies. But then again also, it's fly by wire, so the computer interprets that stuff, I think.

All in all, it might be aerodynamic, it might not be.

Regarding the F117 - its angular shape has really quite bad properties, its highly unstable and would not fly without tons of computing power.

[culver]

The F-117 doesn't need a ton of computing power. It was design in the 1980s. A ton of 1980s computing power = iPod in today computing power

[f6fhellcat13]

Originally Posted by culver

The F-117 doesn't need a ton of computing power. It was design in the 1980s. A ton of 1980s computing power = iPod in today computing power

In fact, that is the reason for its shape. The computers back then could not handle the millions of angles that would make up a curved body, so they created it out of nice flat planes.
Hey, I bet this had at least 64 kbs of RAM! Impressive.