EvanB
EvanB MegaDork
7/15/19 8:11 a.m.

Fun question of the day that may or may not be related to any project I would ever think of doing. 

What would be needed to use an air cooled motorcycle engine in a car? Large oil cooler? Custom ducting with vents for air flow over the cylinders? Electric fans for air flow?

Is it just a terrible idea (for cooling reasons, not the other reasons it would be a terrible idea)?

JohnInKansas
JohnInKansas SuperDork
7/15/19 8:28 a.m.

Ducting for sure, fans if you were going to run it at low roadspeed for very long.

One of the challenges of bike engine in car is oil. Motorcycle oil sumps tend to be less baffled than car sumps since they can lean, which keeps the oil fairly level relative to the engine. If you mount a bike engine in a car, theres no lean, so the oil will tend to slosh over quite a bit more during sustained cornering. Dry sump seems to be a common fix for those who intend to drive them in anger.

GameboyRMH
GameboyRMH MegaDork
7/15/19 8:51 a.m.

^Good answer, the sump is the #1 issue if the car is used for anything but gentle cruising. It's not a terrible idea, after addressing the sump, some ducting and fans will do the job, and adding an oil cooler (if the bike didn't have one) sure couldn't hurt.

iceracer
iceracer UltimaDork
7/15/19 1:30 p.m.

In reply to JohnInKansas :

Curious, how does the oil stay level as the bike leans ?     Centrifugal force ?

aircooled
aircooled MegaDork
7/15/19 3:24 p.m.

Yes, if a bike is leaning it's a turnin' and if it be turning its generating centrifugal force.

The only oiling issue you should normally have on a bike is jumping, then it's zero g's, but not for long (unless you name is Evil) and no power.  Not actually sure how bikes deal with that on 4 strokes (probably just with capacity), for 2 strokes, a non-issue.

No Time
No Time Dork
7/15/19 6:48 p.m.

Snowmobiles use a fan and duct work to provide airflow to the engine (see photo), and additional ducting on the inside of the hood to let cold air in and warm air out.  

The hoods have some vents which help draw heat away from the exhaust, but not enough to cool the engine without the help of the fan. 

Appleseed
Appleseed MegaDork
7/15/19 9:53 p.m.

I can be done. The Tucker Torpedo used a flat 6 cylinder Franklin engine. Used for a Bell 47 helicopter. 

Knurled.
Knurled. MegaDork
7/16/19 5:49 a.m.
iceracer said:

In reply to JohnInKansas :

Curious, how does the oil stay level as the bike leans ?     Centrifugal force ?

The lack of it, actually, when viewed from the vehicle's frame of reference.  Unless you're a super cool dude hanging off the side of the bike in a corner, the cornering forces always resolve straight "down"  to the tire contact patches.  That's how two wheeled vehicles work at all.

(Technically they still resolve that way when the rider is going sidesaddle, but the rider is just shifting the CG to the inside - the effect is just the same as that of leaning the bike over a few degrees while riding in a straight line, so not really very significant)

Knurled.
Knurled. MegaDork
7/16/19 5:52 a.m.
aircooled said:The only oiling issue you should normally have on a bike is jumping, then it's zero g's, but not for long (unless you name is Evil) and no power.  Not actually sure how bikes deal with that on 4 strokes (probably just with capacity), for 2 strokes, a non-issue.

 

A guy I used to work with had a Ducati, and before the thing was six months old, he had to have the engine rebuilt several times.  Apparently the Ducati oiling layout does not tolerate riding with the front wheel airborne for long periods of time.  (Presumably they accelerate quickly enough that acceleration g's are too momentary to be an issue)

freetors
freetors Reader
7/16/19 7:15 a.m.
Appleseed said:

I can be done. The Tucker Torpedo used a flat 6 cylinder Franklin engine. Used for a Bell 47 helicopter. 

On the Tucker they actually "converted" it to water cooling somehow. Pictures of it look like they put different heads and cylinders on.

Appleseed
Appleseed MegaDork
7/17/19 1:14 a.m.

Here I thought it was air cooled the whole time.

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