M/Bike engine swapped cars

[MaxRothery]

What s the heaviest car you could swap a motobike engine into? ive seen caterhams and west fields and the occationall mini, weighing 500Kg and 700Kg repectfully, has anyone ever heard or done one on a car weighing 800Kg-1000Kg

[PhillipM]

As heavy as you like, it's just sorting the drivetrain that's the issue, nothing with the engine itself.

FWIW I've seen Yamaha and Kawa motors in 1200-1400 4wd cars.

[MaxRothery]

PhillipM said:

As heavy as you like, it's just sorting the drivetrain that's the issue, nothing with the engine itself.

FWIW I've seen Yamaha and Kawa motors in 1200-1400 4wd cars.

So basically, it's just the gearbox that's the weak point? Ok, thank you

[PaulKemp]

You will need the biggest or most powerful bike engine in a heavy car, bike engines are mostly about revs
You will also need a reverse box to add into the drive train or an electric reverse which will suffer more with a heavy car

[KiaDiseasel]

PaulKemp said:

You will need the biggest or most powerful bike engine in a heavy car,

Why?

[PhillipM]

MaxRothery said:

So basically, it's just the gearbox that's the weak point? Ok, thank you

So long as you design the drivetrain to tame the shock loadings from a heavier car the 'box will be fine.

[Tango13]

Read up on converting the engine to a dry sump set up.

When cornering a bike engine is leant over so the oil is forced into the sump, in a car the 'g' is lateral which can cause oil pick-up issues.

There was a thread in owners cars somewhere where the OP blew up two or three engines in his kit car due to oil starvation.

[spyder dryver]

There's tons of info regarding BECs (Bike Engined Cars) on the Locostbuilders Forum. Some engines benefit from uprated clutch springs. Dry sumping is advised on others. My Fireblade engined BEC has a baffled, big-winged sump.
The engine is mounted with "silentblock" rubber bushes.
Its only 929cc with 140bhp but it only weighs about 425 kilos!
If I was converting a "heavy" car I would go for the biggest, most powerful unit I could afford! 800-1000kgs? Should be OK.
And do your research regarding overall gearing. Bike engines have widely varying internal "primary" gear reduction ratios. It is a major factor in deciding on the required "final drive" (i.e. diff) ratio.
There's a useful spreadsheet based calculator on the Locost site where you can input your chosen engine along with tyre size, diff ratio, etc and it indicates your speed in each gear.

[227bhp]

KiaDiseasel said:

PaulKemp said:

You will need the biggest or most powerful bike engine in a heavy car,

Why?

Go on then i'll bite

You wouldn't put a car engine in a truck would you?
Honda make cars and motorbikes, they don't put the motorbike engines in cars or vice versa.

[ZX10R NIN]

The thing with bike engines is they don't produce torque in the same way a car engines do but they do spin up faster so you need to put them in light cars, unless you want to use a rocket engine then all the benefits of a light powerful engine are diminished.

[alspeed]

The 'biggest' current bike engines are still only producing around 200 bhp out of the box with limited torque, in a 1000kg car your going to get 200bhp/ tonne. So not exactly earth shattering performance.

The clutch and gearbox are tiny, designed to cope with the stresses of a 200kg bike, even in a 450 kg BEC you have to be sympathetic with down shifts or it quickly leads to trouble.

Personally think the plan is a non starter, anything over 500kg would be better with a car engine.

[chuntington101]

alspeed said:

The 'biggest' current bike engines are still only producing around 200 bhp out of the box with limited torque, in a 1000kg car your going to get 200bhp/ tonne. So not exactly earth shattering performance.

The clutch and gearbox are tiny, designed to cope with the stresses of a 200kg bike, even in a 450 kg BEC you have to be sympathetic with down shifts or it quickly leads to trouble.

Personally think the plan is a non starter, anything over 500kg would be better with a car engine.

Or 2 bike engines!

[George111]

Biggest problem with bike engines in cars isn't power or torque but gearing and a reverse gear. You need a 3:1 diff unless you want a low top speed and you need to add a reverse gear. On a Caterfield you can easily get out and push but try pushing a 1 ton+ car up a slope you mistakenly drove down forwards. The Quaife reverse box is only suitable for very light cars and even then isn't very reliable.

Clutches in bike engines are small and cope well enough with a 500-600 KG car but will just burn out on a heavier car, even a Hayabusa.

The oil in a bike engine in a car doesn't last very long - at 2000 miles I can hear mine needs changing because the top end gets very noisy, fresh oil restores normality. The oil is shared between the clutch, gearbox and engine so gets hammered.

I would stick to a car engine, will be cheaper, more reliable, probably offer more power and a better drive.

[PhillipM]

ZX10R NIN said:

The thing with bike engines is they don't produce torque in the same way a car engines do but they do spin up faster so you need to put them in light cars, unless you want to use a rocket engine then all the benefits of a light powerful engine are diminished.

That just boils down to the right gearing.

[227bhp]

I think the question should be "What engine for my car?"