With all of the talk about light weight, high horsepower replacement engines for our favorite Porsche, have we forgotten all of the lightweight, high revving 4 strokes out there? There are dozens of possible alternatives currently being housed in various motorcycle brands. Are there any working examples of this type conversion out there? Thinking besides the lightweight, they tend to be compact and have smaller cooling, electrical and mechanical systems. Would seem using one for a conversion would be a no brainer. What am I missing?
Thanks

I think torque would be a problem if using a motorcycle engine not to mention that many of those engine make power above the 12,000 rpm mark.

I've seen videos of a Fiat X 1/9 hillclimber with a Hyabusa engine. Fast as hell and really screams. No sure I'd want to sit in traffic with it though.

Torque.

Do a search and you'll find a few threads. All talk about no torque for a driver

Well my setup is being built to rev to 8250 reliably... I mean sure on race gas I'll be shooting for 500+, but my street tune will probably be over 400 and my mountain tune between 250 and 300....



The biggest issue with a street bike engine is very few of them have over 75lbs of torque and ONLY at way high RPM's. When driving around town under say 5k rpm's you only have a tiny amount of torque available which makes driving around town either a chore or it makes you FEEL like you have to rev the piss out of it to drive it anywhere..

Torque yes, but don't forget bikes don't have reverse, so you have to adapt a cheesy starter motor/gear reduction thing if you want it. They do rev like mad, and sound cool, but after building one, I actually re-converted it to a type 4 Supervee/Hewland I had built.

"There are dozens of possible alternatives currently being housed in various motorcycle brands. What am I missing?"

My initial thought was..."motorcycle brands"..., oh, like Honda or Suzuki car engine swaps. Sorry, but still think of those cars as "motorcycle brands".

I guess my brain was not thinking enough outside of the box. (Need more coffee).

What about a Harley swap?

[quote name='Hank914' date='Mar 5 2016, 09:32 AM' post='2311586']
"There are dozens of possible alternatives currently being housed in various motorcycle brands. What am I missing?"

My initial thought was..."motorcycle brands"..., oh, like Honda or Suzuki car engine swaps. Sorry, but still think of those cars as "motorcycle brands".

I guess my brain was not thinking enough outside of the box. (Need more coffee).

What about a Harley swap?

It will sound like a low revving slug.

If you look at the typical T4 or /6 build, the torque and Hp (number) are still fairly close to each other. With the T4, stock or performance, it's damn near the same number.

In fact for the street I say the torque is the more important number.

lots of info here dispels some of the myths
http://www.motoiq.com/MagazineArticles/ID/...e-Thinking.aspx

You're really transmission limited. Acceleration is a function of tractive force which is a function of transmission output torque. You just need a transmission geared for the engine you want and you'll be good to go. The stock bike transmission really isn't geared correctly for our application, but if you had more car-friendly gear ratios it could work. In the Miata link they remove the bike transmission from the equation altogether to solve that problem.

The Miata build link is super cool, thanks!

No it wouldn't be a good fit. No, we haven't forgotten that there are light weight engines out there (that wouldn't be a good fit). You are missing quite a bit. Have you ever driven a car powered by a bike motor?

Tony

Hey chill out Uncle Cracker......I asked the question because I didn't know, and hadn't seen this type of conversion.

What about something Boxer or in "V" configuration.

Honda Goldwing, BMW, ect

....TORQUE THIS

https://www.youtube.com/watch?v=AgwzHJo3IXM

"Uncle" Cracker (Kind of like the sound of that...how do you change one's UN?)

PS: You never answered my question young'n...

Tony

Nope

I'll take that as you have no experience...here is my 4-stroke, bike-powered P1 prototype. This car weights 850 pounds wet. A light 914 with a bike motor would still be twice that - there is absolutely no way, no how it would make for a good power plant for a 914 conversion. The bikes transmission and clutch are already challenged at my cars weight. I have to slip the clutch quite heavily just to get moving - not good for any street driven vehicle (anyway). I'm sorry I was so hard on you, being new and all. Welcome to the World.


Tony "Uncle" Cracker



Click to view attachment

myth busted

https://www.youtube.com/watch?v=JGvLMg0DY0o

Its all about usable power

But the engine i would say generally makes the personality of the car

So i think turbo chared straight 4 or a straight 6 would be ideal

But something about ethl glycol and huge radiator s just seems so un porsche to me



My goal would always be like 290 horse and 290 tourque
The so called limit of the transmission

I see videos of him hooning around and doing doughnuts, not driving around in stop and go traffic or in the hills or mountains.

Easy to rev it and dump the clutch to smoke the tires, but that doesn't show us how it is in the real world...that being said, I love it!

Wonder how much lighter that Miata is than a standard 914?

I'd want to dump as much weight off the 914 if going this route.

Motorcycle engines in cars

Link above shows more examples.

Using the stock transmission would be silly...why bother with a poorly geared transmission? If one could install a different engine then they should have the skills/means to upgrade the transmission to something better.

The problem is with allot of bike motors, the transmission is integrated into the engine case - they are ONE unit. There is no separating them. The OTHER problem is they make peak torque atvpower and very high rpm's. My engine makes peak power at 12,500 a Busa about 9,500 - my engine has maximum torque of 79 ft lbs. Someone try to pull this off and I'll race them to 130 mph - I'll start out in 4th gear too...

T

Ever seen the connecting rod of a Cummins big truck engine? 14 liter straight six with a connecting rod almost the size of your forearm. Funny thing, that engine only puts out about 400 horsepower, as much as a healthy LS engine.

So why is no one putting LS engines into over-the-road trucks? Exactly the same obstacles. You can put a rev-happy bike motor into an EXTREMELY lightweight car and it will be at home on a race track, there are lots of examples. But when that same car is over 1000 lbs and in traffic the benefits disappear in a hurry and its life is shortened exponentially. No joy.

Joy you say you want...........here's a flying refridgerator:

https://www.youtube.com/watch?v=wTjVEKYhJXg

Back when I was fixing cars for a living, I had one of these come into the shop:



It's a Honda 600 convertible, built in 1965. It has a 600cc motorcycle engine, connected to the rear axle by a long motorcycle chain. To get reverse, Honda put a gear in the center of the sprocket that spun the wheels backwards. That gave you 6 sequential gears, both forward and reverse.

Well, the owner had just bought the car, and he said it didn't pull very strong. When I examined the car, the original engine had been replaced with a 1100 Honda Hurricane motor, complete with Kerker header and a bunch of high performance mods. It had 10 inch X 10 inch wheels and tires, full harness assemblies on both sides, and the Hurricane instruments had been beautifully grafted into the dash.

I said it sounded fine, and asked him to take me for a ride. Well, he was shifting at about 2500 RPM. Needless to say, shifting that early killed all the performance. So I asked if I could drive, and he let me. About the time I hit 6K on the tach, I hear a loud "OOOOOHHHHHH SHHHHIIIIIITTTTT!!!!!!" come from the passenger seat. I then proceeded to smoke a brand new Corvette up until the next light. After that the vette got me for about 50 yards... until I got he Hurricane spooled up.

I explained to the delighted owner that he would have to tach the engine up to get the car to move in any reasonable fashion. I didn't charge him anything and thanked him for the drive. I also told him that if he wanted to sell it, I wanted to buy it.

He left with a roar and a shit eating grin on his face.


The thing about that car was that it only weighed 1200 LBS, about what the motorcycle weighed. So the engine was fine with pulling that load. If you tried that in a 914, you would be adding another 900 lbs of weight, and you would have to rev it even more to get it to move decently.

In all truth, a motorcycle engine is fine in a very, very light car, but by the time you get safety and confort stuff on the car, you are just outside the envelope for that type of engine.

Even in the SCCA DSR/P2 class, where the chassis weigh somewhere between 1000-1250 lbs, the engines are already overtasked. Our car comes in around 1100 lbs, which I would change if I could. Granted, it's being raced, but the lifespan of the motor is somewhere around 40 hours. It's a rocket when it's on track, but it's doing something it wasn't ever intended to do. Add another 900 lbs, and you're really putting the engine/trans into a situation where it's operating at 110% all the time.

Hey! I drove one of those in 1967. 10,500 redline if I recall (maybe it was 12,500). Friend of mine had this and a '55 300SL Gullwing. He'd lost his license and needed drivers to get the cars to a car show on the high school football field. I had to drive the gullwing to the show but drove the Honda home. Two entirely different driving experiences.

The best engine I could see being used in a 914, small displacement, high revving applications is a Honda F20C with TB and aftermarket cam/tuning. I believe they are
good for roughly 260 in that trim with 9000 usable revs. Would it compete with an LS well built LS track car - no way. But it would be different - at least one member here installed one. I've never seen him at the track though...

T

http://www.tomsgarage.com/files/lo12_035.JPG

This is the 900lb. Hayabusa powered Lotus 23-like project I built about 12 years ago. Not practical, but sounded so good!

I realize this is an older post and I'm not trying to advance the discussion one way or the other, but this just put a smile on my face....granted this is a 1000 lb car, but it's probably got 425lbs worth of "dude" in it.... post inspired by a 914 Hayabusa conversion for sale right now on the Orange County Craigslist.

https://www.youtube.com/watch?v=wIWGo2d8Xr8

...hope this link works.

The mod your looking for is a rotary or wankel engine not a motorcycle




An since this is the weight topic
Is a 912 lighter at 2127lbs
Then a 914 at 2180 ???

Because i would think rear engine swap
Is way easier them mid swap

But a porsche is traditionally a car with torque the primary focus .not all out speed not high rev

The tranny made for a bike can't handle the weight of the car. It's physics. Everyone gets enamored by 200 hp.

Put a Hyabusa or equivalent engine on each rear wheel. Thoughts, not wise, but there was a Lotus 7 clone that did this.

https://orangecounty.craigslist.org/cto/d/w...6841373806.html
1976 Porsche 914 with a 2006 Suzuki Hayabusa 1300 motor swap...
does not have reverse!!!! Has 37k on the motor ..full custom build to much to list registered and ready to go..

Willing to trade for a 2005 or newer 22ft toy hauler

Somebody go and test drive it and report back ...

It seems I'm on the opposite page than almost everyone here. I've always believed a M/C engine in a 914 would be great. I've built SCCA formula cars with Hayabusa, Yamaha R1, and Gen 5 Kawasaki ZX-10R. The comments about lacking torque and poor gearing are nonsense. You can easily change either (or both) sprockets to get the RPMs where you want them. So take away 350 lbs from an engine and 100 or so lbs for the transaxle / clutch. My R1 was 142 lbs complete and Kawi at 150 or so lbs. Quaife limited slip chain drive differentials have been out there for a long time, and no probs bolting up CV's or tripods. We thrash these engines like crazy. As long as you have good oil flow and the oil temps aren't too high, they run and run. An oil/water heat exchanger does wonders. I almost did this on my last 914 with leftover parts I had laying around, but I went a completely opposite direction with a 993 engine. I still debate doing the M/C engine thing, even with my present project.

How does changing a sprocket change at what rpm the engine makes peak power/torque?

It's been a while since i was into (dirt) bikes but i'm pretty sure changing sprockets only changes how fast (or not) you get to peak rpm.

You'd still have to drive around town at 10000 rpm to get a 914 with you in it to move ...

I have a bike powered car and it would be terrible in a 914 - for several reasons.

T

You could drive around town at 5-6000 RPM but would need about 8500 RPM to accelerate at a reasonable rate. As you said (Sir Andy), sprocket changes don't affect the torque characteristics - only the RPMs at wheel revolution rate. A 14 front 50 rear sprocket is where I'd start. And 13" or 14" wheels would help too. I rode sport bikes for years, and you just get used to the RPMs.

Well, it does run...914
https://www.facebook.com/tim.silvey.9/video...eater&ifg=1