What bike engine should be used in a Mini-sized ecomodded car?

[Arragonis]

Question - are you looking for lightest weight or best FE ? Or are you just wanting a bike engined Imp (deep respect ) with some FE ?

The best FE would be the ForTwo diesel or the 1.2 Polo TDi. Good luck on the latter one. And If you do those then either go mid-engined or line yourself up with a load of work to get a suitable gearbox and gearing unless you can get the gearbox from the Smart to fit.

Reasonable FE would be a more modern car engine, say a K-Series maybe a 1.1i with FI to take advantage of EOC etc. But then you have to connect it to your transaxle but this has been done.

The Imp is of course a small cottage for Aero unless you work on it quite hard. There are a few Clans about which you could use for this type of conversion which have less frontal area but may need Aero work.

Hillman Imp (god, what did Chrysler think when they bought Rootes ?)


Slightly more sporty Imp Coupe


Clan Coupe (Imp oily bits)


Note the best car ever in the background...

[fjasper]

Maybe shaft drive isn't the be-all and end-all. One of these chain-drive differentials with integrated disc brake might make it practical to use (and swap between) any number of sprocket-drive motors.

[NHRABill]

Chain drive vs. a drive shaft now there is a world of difference, the drive shaft you are going to have more of a loss at the differential but it is durable and doesn't need adjusting with a chain drive be prepared to adjust the chain tension from time to time especially on a home built project and there is that unknown if the chain can handle your design and stress...

[fjasper]

Chains are very efficient (non o-ring ones), and very strong chains are available (similar differential to the one at the link was used on a racecar running 230hp through a chain), but adjustment could be an issue.

I wonder, in an automotive setting, if it would be practical to have the chain run inside a housing so it could be continuously lubricated and kept clean. Timing chains seem to last practically forever, for instance. They have nice continuous tensioners, too (oily chain slides on long curved spring-loaded poly blocks).

Interesting issue. Size/shape of the space available might be the determining factor.

And then there's belt drive...

[rkcarguy]

I'm going to say +1 on the Suzuki SV series V-twin engine. A couple of my friends in a social riding group get the best economy of the bunch riding SV-1000's, and they are very torquey...perfect for a small car imo.

[nimblemotors]

why don't you just use and modify the engine it came with?

Originally Posted by Air-Hybrid

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.

[roflwaffle]

For the Imp you should get a 1+L automotive engine that has the best choice of gearing. BSFC isn't going to vary a whole lot between engine families built within the last decade or so, but gearing can, and that's where you are going to make or break it in terms of mpg. A 750kg car should be able to get great mileage with low enough gearing.

Originally Posted by Frank Lee

I was going to mention the Gold Wing.. but my 1100 and I guess most all of them don't return very good fe, usually in the 30's and I don't think I've seen anyone claim any better than 40. In fact I'm deciding if my bike would run better and more economically if I ditch the 4-carb setup and put a single automotive carb on there...

Why not go w/ a used set of ITBs, a wide band O2 sensor, and something like megasquirt? It would be a bit pricey at ~$200+, but you could go as lean as you wanted to.

[Frank Lee]

Because it is a bit pricey! Don't forget adding an ECU, pressurized fuel system, etc. And I can go as lean as I want via cheap lil ol skool jets.

One reason fe is poor on my Wing is a suspected rich-running carb. They're kinda a bugger to remove and service, and parts are rape-me expensive. Remember, Honda hates their customers.

Besides the shaft drive being less efficient than chain or belt and gearing not as tall as it could be, I don't think there's a fundamental (architectural) reason for the 1100 to be so inefficient. The carburetion is poor on mine but the ignition and exhaust systems should be good for effient fe. I think it's probable that a cam profile more biased to lower rpm operations would help along with intake system resizing (smaller, longer tubes).

[roflwaffle]

The megasquirt ECU kit is very expensive at ~$140, but everything else isn't too bad. You should be able to get everything else used for about (fuel pump for ~$30, the TBI setup for ~$40, both used, and the wideband sensor for ~$60 new) $130, or less if you shop around. I dunno if it's economically worthwhile paying $200+ more to be able to tune for all the different engine speeds/loads, but it could be if you put enough mileage on the bike. Even if the difference is only 55mpg versus 45mpg w/ the auto carb, it would still pay itself off in ~20k miles.

It would probably be best to see what you could get w/ a cheap auto carb first, then maybe go for the TBI setup if your results aren't as good as you hoped for. Everyone hates their customers these days. I called after my door lock went out and Toyota was asking $800+ for it. Over $1000 for the door card.

[Air-Hybrid]

Originally Posted by Arragonis

Question - are you looking for lightest weight or best FE ? Or are you just wanting a bike engined Imp (deep respect ) with some FE ?

In answer:
As you you have implied, if ultimate FE was the only driver I wouldn't even be starting with an Imp
I would say, as the standard car can do 50+ mpg (UK) on run, -even with a progressive choke- I would have a hard time to get more than 20% better. It does suffer round town though, and this is where I think modern wizardry could play a part (ECU's, etc).

As is commonly known, (by those who care!) the Coventry Climax engine was pretty advanced at the time & it has been common to bolt-on injection & other improvements to the std block for quite some time. That said I do think, the money cost of 'modernising' is now greater than replacing with an modern equivalent. The trouble is that, even low-displacement car engines today are at least as heavy (+ have more grunt than is needed) than the original (A Toyota 1KR-FE 2007 onwards would be great but I can't afford one yet).

It's for these reasons that I have reckoned that a torqued Bike engine (of 750+ from the early 2000s) would be the best compromise. And I just like the concept of using Boxer and perhaps experimenting with it (ECU maps, cam-mods, etc) down the line.