V-Twin

[DannytheRadomski]

The typical set-up for most FSAE cars now is either an inline-4 600cc sport bike engine or a 450cc single, but I was wondering about twins.

The main problem I see with a twin is that there aren't very many of them. There's the Aprilia, but it seems like everyone avoids that like the plague. Other than that, the only one I can think of that isn't 250cc or two stroke is a 400 made by Suzuki, but it is on a bike that is only on the Japan market.

Anyhow, the reason I was bringing twins up was that I was wondering if they are a good medium between the sporty, thirsty 4s and the frugal singles. Do they produce more competitive power and more competitive fuel economy than the other two configurations can do on their own?

The only twin I see as good though is the Aprilia because it comes as either a 450 or a 550, so it isn't too small to be underpowered or too big to offset the economy. An answer I know I'll inevitably get is that the engine is only good if the car is set up for it. As BigBird might say you wouldn't want a parfait with steak instead of strawberries, but I also think you can assess an engine beforehand to see if it is a good place to start.

Thanks for any and every reply.

[Jay Lawrence]

There are several teams that use the Aprilia (here in Australia we at least have USyd). As far as I know, the primary issue is with starting, though I'm not sure why this is such a big hurdle for the teams that use this engine. Other options include the Suzuki SV650 engine (Tokai University from Japan used this), which cylinders de-bored. There's also the Ducati 620 (not sure of the actual capacity but they are typically over quoted). Auckland have been developing their own V-Twin + transaxle for a few years now out of 2 x YZ (WR?) 250F engines. For me, a V-Twin would be quite ideal, as they are typically more compact than a 4 whilst producing more power in a smoother manner (lower pulses for turbo, for example) than a single, and lend themselves to transaxle attachment. However, my feeling is that of the V-Twins currently on the market, the only one that seems suitable 'out of the box' is the Aprilia (which most teams struggled with at some point/are still struggling with). They are very expensive too.

[tromoly]

Chatting with teams at Michigan, IIRC the biggest issue with the Aprilia is here in the States parts availability and tuning knowledge are lacking, making engine development a bit slower than other engine designs.

[Big Bird]

True, I'm not big on steak for dessert. And I probably would have said something like that. I'm obviously getting predictable...

Aside from availability. V-twins aren't really the ideal shape for one of our cars. V-twins are narrow across the crank (great for reducing frontal area on a motorcycle), but they tend to be longer and or taller in side view due to the splayed cylinders. And practically, intake and exhaust will tend to be more complex to design and manufacture.

I have seen one Ducati powered FSAE car, sounded lovely but the car was quite long.

Cheers,

Geoff

[jlangholzj]

Chatting with teams at Michigan, IIRC the biggest issue with the Aprilia is here in the States parts availability and tuning knowledge are lacking, making engine development a bit slower than other engine designs.

I've never worked with the ape but I can't see it being any more of a hurdle than any other motor. Unless you're talking about little tricks internally to the motor to squeeze more out of it. Anything externally (intake, headers, fuel maping, comps etc) should be on par with any other motor. Everything that I've seen about them is that they're just a very fickle motor, sometimes they're happy, other times they're not and nobody is really sure why. Also don't they have a pretty ridiculous service schedule?

[tromoly]

Everything that I've seen about them is that they're just a very fickle motor, sometimes they're happy, other times they're not and nobody is really sure why. Also don't they have a pretty ridiculous service schedule?

I've probably forgotten what was exactly said, this sounds right in regard to the tuning issues people have had.

[Mbirt]

True, I'm not big on steak for dessert. And I probably would have said something like that. I'm obviously getting predictable...

Aside from availability. V-twins aren't really the ideal shape for one of our cars. V-twins are narrow across the crank (great for reducing frontal area on a motorcycle), but they tend to be longer and or taller in side view due to the splayed cylinders. And practically, intake and exhaust will tend to be more complex to design and manufacture.

I have seen one Ducati powered FSAE car, sounded lovely but the car was quite long.

Cheers,

Geoff

To quote Firenze's FSUK 2010 event program entry:
"The basic idea of our cars is to
build it around two main
components: the driver and
the unavoidable Ducati twin
cylinder engine. The presence
of the Ducati engine is a pride
of ours, as we have the only
official sponsorship in F-SAE
series, and a challenge, as its
shape is not easy to position
in a race car. But what a
lovely sound when it roars!"

Sounds like steak parfait to me.

As for the Aprilia, I can think of a few examples of teams rising to new heights of success after dumping it and choosing engines that better fit the design philosophy of the car. Kansas used to run an Ape (2009 is the last one I recall), switched back to a 4 cylinder, and has scored 861 and 825 points at Lincoln the last 2 years respectively. A powerful, reliable 4-cylinder is a good fit for rocketing their car around the SCCA nationals courses. EPM (Montreal) switched from a monocoque and Ape to Rotax DS450 and spaceframe this year and placed 14th at Lincoln (their first sanctioned competition of the year) to jump 222 spots in the FS-World ranking. I can't speak for them to attribute previous performances to problems with the Ape v-twin, but I did observe lots of trouble just getting it to start at several events.

[DannytheRadomski]

I feel like this thread is starting to become "What are the logistics like for the Aprilia V-Twin?" So let me attempt to return this back to my original intention. Do twins make a good compromise between 4cylinders and singles, balancing power and fuel economy?

[AxelRipper]

http://youtu.be/_vZ6WFfiLvk

My, that Duc does sound nice. I never quite realized how tall that motor is though. I would've thought that it would be pretty easy to package due to the laid down front cylinder. Just pack it under your driver (as they appear to have done (referencing some other videos and pictures).

In my opinion, the best way to to it would be to make a full drivetrain package, integrating 2 250cc cylinders with a transmission and diff of some sort in the back. Could create a really nice tight low CG package with it. Also, Same engine would have a near-180 degree bank angle

[DannytheRadomski]

So Auckland's V-Twin minus the crank angle?