Anyone ever put a larger displacement motorcycle engine in a 914? The VMax features a compact v-4 that makes 197bhp, 123 lb/ft torque and will peel your face off. Obviously it weights a lot less, but then I got to thinking about other options. We just got a Triumph Rocket III in stock and it's a 2.3 litre inline 3 cylinder. Makes 146 bhp and 163 lb/ft torque. Both motors are pretty compact and feature a shaft drive 6-speed transmission.

I think the transmission mating would be the most difficult, but what about adapting the motorcycle transmission somehow? I picture connecting the drive shaft to a rear differential of some sort. Or...if you could mate the shaft drive from the bike somehow to the 901, you could essentially have 30 different gearing combinations. All I would do is mount a hand clutch somewhere, maybe near where the rear brake is, and replace the heater lever with a simple hand shifter that would link to the bike's transmission. You could ALWAYS have the right gear, but you might need an extra hand or two, or a co-driver to manage the second transmission lol.

One major benefit would be the lighter weight and the smaller radiator size, which might be able to be placed in a wheel well or somewhere besides the front trunk.

This sounds crazy and over engineered to me, and probably not worth the effort, but I'm 27 and I'll hopefully be involved with teeners for the next 73 years (assuming I make it to 100, which is my goal), so I've got plenty of time to become a car building pioneer lol. Feel free to poke as many holes in this plan as you like. Won't hurt my feelings a bit.

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Lots of Lotus 7 type cars use motorcycle engines...

-Steve

Motorcycles converted into trikes are using IRS rear ends now, that may be something to look into...

kind of like this one from a t-bird super coupe....

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WOW that looks like a lot of work.. and not much Room

Or stick with the trailing arm suspension and use one of these...

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GSXR 1000 powered fiat X1/9

http://www.youtube.com/watch?v=cQM3krBmqbg

I'm building one this winter ....

The x19 is smaller & lighter than a 914. Mass has a lot to do with the survivability of the bike gearbox in a car. (the GSXR 1000 and hayabusa seem to have gearboxes that hold up a bit better than the R1 and CBR's)

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The engines typically have very little low end torque, which makes them difficult to drive, the transmissions have no reverse gear, and they rip your face off because they are in a much much much lighter vehicle. The owners of bike engined lotus 7 based cars even comment that the engines dont have that much torque for that 1300lb car... Add another 800lbs and your looking at an even worse situation.

Your much better off with a car based build.

Exactly right. I have a Seven replica as well as motorcycles so know both, and there's no way in hell I'd put a V-Max or any other moto engine into a 914. Even the Seven replica is 1150 lbs with engine and transmission. You could get that down to 900 lbs with a motorcycle engine/transmission, maybe less, but you'd still be down torque. I saw a rear-engine Mini conversion in the U.K., an almost all plastic car with a Hayabusa motor in the back that probably weighed 800 lbs. That would work. If you can get your 914 down to 800 lbs that would work too, but good luck with that, and even so it wouldn't last long pushing that much weight around.

Why do people fail to realize the weight difference between a bike and a car and how that might matter? Do we have to explain it?

Ahem....Goldwing! 1800cc flat 6 118hp / 167 tq (stock), Fuel injected, sequential 5 speed with reverse gear on a vehicle that tips close to 900lbs.

What does the fiat weigh? I've always heard they were heavy. I see that one is a racecar. A teener racecar can be 1600 with a -4.

What does that one weigh?

I haven't weighed it yet but it is very light. My son and I easily pushed it up on the ramp trailer. Every panel is 'glass except for the door skins. The car currently has about 50lbs of lead bolted into the passenger footwell from when it ran GP.

I'd hazzard a guess that it is about 1000# without the motor/gearbox/axles...

I say put TWO V-Max engines in there and hang on.

awesome...
I googled and found various stock weights from 2015 to 2130
so about the same... maybe slightly lighter than a teener depending upon year
PCA club racing accepts the stock weight of early bumpered cars at 2149 in street trim

I'm very aware of the weight difference between a car and a bike. My 914 came with a 67 hp, 99 lb/ft bus motor and I had a blast driving it. So I guess my question is: Other than flywheel weight, does it matter where the motor comes from? If a motor makes a certain amount of torque and hp, does it matter if its a type 4 or from a Yamaha? I've seen lots of money thrown into a type 4 that has a lot less than 200hp and 130lb/ft torque.

I do understand that a 914 wouldn't be the best choice for a motorcycle engine swap. Most motorcycle engines make 0 power below 5k, but some of these motors are different. The rocket III starts making power at 1200 rpm or something like that..

I would expect the strength of the gears to be vastly different. Made light to pull 900lbs to high rpm but not made to pull the weight of a car.

For example how would a 901 do under a Mack truck?

That's a good point, I'm pretty sure I'll end up doing a suby swap eventually anyway, I just couldn't stop thinking about that bike ride lol. I should NEVER ride in a 914-6, but I don't think I would be capable of turning a ride down lol.

google the busa Miata....

the use the gear reduction in the tranny case 2/1 and gain the torque.

it's being done.

http://www.motoiq.com/MagazineArticles/ID/...e-Thinking.aspx

Sure, but keep in mind that motorcycles are made to be lightweight, so that's what motorcycle engines are designed to push around. They reduce internal friction by running larger (almost race) clearances, the bearing shells are narrower and thinner, rings are thinner, very short skirted pistons for high RPM's, lighter rods, crank's lighter with smaller journals, etc, etc. So they do make large HP and torque for their size, but give up strength and longevity to do it. When I dump the clutch in my car I've been breaking CV joints, in a Hayabusa powered 914 I'm pretty sure I'd be breaking crankshafts. A nice LS1 will produce more HP than a 14 liter Cummins diesel, but if you put an LS1 into a semi truck you need to adjust your expectations, for obvious reasons. I'm not familiar with the Rocket engine except from photos, so it might be a truck, I don't really know.

Don't misunderstand, I'm all in favor of swaps and moto powered cars can be fun. Like I said, I have a Seven replica, have met some of the Hayabusa/Fireblade people in England and seen their cars. And original Morgans, of course. But all those cars are a lot lighter, and the work involved with that swap is nothing to sneeze at, so if you're going to do all that work hopefully the HP/weight gain will be worthwhile. Especially if used on the street. Bob does great projects, and that Fiat has a history in the VW world, so I look forward to see how his turns out.

It's always fun to stir the pot, my only advice is to study it carefully before you decide. And who knows, maybe if a bunch of moto engined 914's show up the Porsche purist/concours contingent will look on me with less skepticism. Nah... probably not.

It's a lot more than just raw torque and hp. First off, it's about torque and hp at given rpms. Look at the torque curve of a four banger car motor, and compare that with the torque curve of a motorcycle engine that is rated for even twice the same power. You'll see that there is NOTHING near the bottom end where you need it to accelerate a car away from a standstill. Second, and more importantly, it's about how much load the drive-line is under when accelerating. The internals of the motorcycle engine don't need to be that beefy to withstand the load of accelerating even a 600 lb chassis. The internals of a car engine need to be a lot stronger to withstand the load of accelerating a 2000 lb chassis. This is why MC engines can be so small and light. The crank, rods, etc do not need to be very stout when they're really not subjected to much load. Those same internals for a car need to be a lot stronger as they are working against a much heavier load.

-Josh