Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - What bike engine should be used in a Mini-sized ecomodded car?

Air-Hybrid · 03-07-2011, 12:16 PM

Hi!
I'm asking a very open question here, obviously - but...
I have in mind a conversion for a 60s car (the Hillman Imp).
The kerb weight for the car is quoted at around 750kg (100 more than an Austin Mini, but a prettier car IMO) - plus is also rear engined/rwd which suits my driving style better

Several Imp owners have converted their cars to bike engined high-revved speed-machines (keeping the Imp's transaxle) - but I would like to get a vehicle that is designed primarily for efficiency whilst keeping the old-school looks intact (though this may hurt the aerodynamics).
Imp engine - 37.0 bhp @4800 rpm. Torque. 67.0Nm(49 lbft) @2600 rpm

Thinking:
BMW R850 Boxer engine - produces 57 lbft , 70 bhp
Oilhead/air cooling could cause problems, but Imp has rad in back, air drawn from under car (messy). Would keep Imp's diff/ section of transaxle casting (or equivalent).
Interested in how difficult it would be to 'de-tune' for lower BHP, remapped for good MPG.
I have a gut feeling that a low-slung torquey boxer engine has plenty of potential for good thermal efficiency, plus breathing is not hurt so bad.

Or for really ambitious build
R1200GS - with 85 lbft 100bhp
- converted cam lobes for Atkinson cycle with Mild hybrid e-motor/batteries combo.

Has anyone any experience using these motors for economy? Is it a good starting unit?
Note - being all Ally the Imp's engine/tranaxle comes in at around 70Kg as standard. I can's see the point in replacing it with anything heavier without a very good reason.

03-07-2011, 12:16 PM	#1 (permalink)
Air-Hybrid EcoModding Apprentice Join Date: Aug 2009 Location: London, UK Posts: 113 Thanks: 16 Thanked 3 Times in 3 Posts	What bike engine should be used in a Mini-sized ecomodded car? Hi! I'm asking a very open question here, obviously - but... I have in mind a conversion for a 60s car (the Hillman Imp). The kerb weight for the car is quoted at around 750kg (100 more than an Austin Mini, but a prettier car IMO) - plus is also rear engined/rwd which suits my driving style better Several Imp owners have converted their cars to bike engined high-revved speed-machines (keeping the Imp's transaxle) - but I would like to get a vehicle that is designed primarily for efficiency whilst keeping the old-school looks intact (though this may hurt the aerodynamics). Imp engine - 37.0 bhp @4800 rpm. Torque. 67.0Nm(49 lbft) @2600 rpm Thinking: BMW R850 Boxer engine - produces 57 lbft , 70 bhp Oilhead/air cooling could cause problems, but Imp has rad in back, air drawn from under car (messy). Would keep Imp's diff/ section of transaxle casting (or equivalent). Interested in how difficult it would be to 'de-tune' for lower BHP, remapped for good MPG. I have a gut feeling that a low-slung torquey boxer engine has plenty of potential for good thermal efficiency, plus breathing is not hurt so bad. Or for really ambitious build R1200GS - with 85 lbft 100bhp - converted cam lobes for Atkinson cycle with Mild hybrid e-motor/batteries combo. Has anyone any experience using these motors for economy? Is it a good starting unit? Note - being all Ally the Imp's engine/tranaxle comes in at around 70Kg as standard. I can's see the point in replacing it with anything heavier without a very good reason. Last edited by Air-Hybrid; 03-07-2011 at 12:33 PM..