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BMW M50b25 vs Yamaha R1 engine, what would be better for a build? what are the biggest diferances rather than weight BMW 194 kg Yamaha around 80kg. Wicht is a better, cheaper and easier build?

S52 if you are doing a BMW engine same size and weight 80 more horses. They would be very different cars. The BMW one would be a great driver for the street or track. BEC are not so good on the street. 14-1500lb car vs 1100lb car. R1 engined car would be a hoot though. A lightly tuned S52 can put 230HP
to the wheels and in a 1400 lb car that would be fun.

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Volvo 240/P1800 Based Locost
2004 Aprilia Mille Factory
1988 Volvo 240 5 Speed ( For Sale)
2002 Toyota Tacoma
1999 BMW M3

"Better" for what? That'll answer the question right there. I agree, track car = bike engine, street car = car engine. The car engine route is most likely cheaper. Easier to build... depends how the bike engine is coupled to the drive wheels. If the solution is already in hand they're about even, otherwise the car engine wins. Yet another issue is how well suited to the bike engine the differential ratio is. That can either be a non-issue or a real show-stopper, so it's either another toss-up or the car engine wins again.

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Midlana book: Build this mid-engine Locost!, http://midlana.com/stuff/book/
Kimini book: Designing mid-engine cars using FWD drivetrains
Both available from https://www.lulu.com/

Yeah i think im going with the BMW engine because i think its a lot easier build and less expesive. Wanna take it easy on my first build. It will be mostly street driven so dont need a bike engine yet but i love the idea

I don't really think it'll be "easier" for one engine over another,well maybe it is actually easier to fit the MUCH smaller bike engine which includes the transmission(that S52 is tall and long without including the transmission).Of course the BMW engine will offer a much more relaxed ride,provide reverse and still have more than enough power to cover the added weight.The bike engine build will outdrive the car engine by quite a bit I suspect.

As others have said, which is "better" depends upon what you want to use the car for. To give you an idea of my impression of driving a BEC right after I got a few 100 miles on my car take a look at this article on my website,

http://dmr-architect.com/~locouki/driving-a-bec.html

A BEC can be safely driven on the street but it is like a Cheetah on a leash. Nervous and always ready to take off after something (especially so with 3.9:1 rear end gearing). You don't want to sneeze and press the gas pedal too far if you are in a lower gear when following another car!

The car engine will give you plenty of performance due to the light weight of the car. The original Lotus 7s raced with less than 120 hp and actually started out in life at 48 hp.

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"My junk is organized. At least is was when I put it wherever it is." -olrowdy
Completed building GSXR1000 CMC7, "Locouki"
Website: http://projekt.com/locouki/

I can get a bmw 325 for under 1000 euros here, i dont think i could even get a bike engine for that money. The car will mostly be used for street driving and with a little engine tuning im around 200hp that is probably enough for me atleast for now. So i think im going with the bmw engine. How about drive terain does everything fit or do i have do find a chasis plan fir the e36