Mini project

Introduction

I've been thinking for a while about what my next project will be and have long wondered about a mini conversion, which was to be the project before the Westfield came along. I've always liked the look of the original Italian Job cars with skinny tyres and looking relatively standard. The later model sportspack cars look nice as well but don't have quite the same street-sleeper appeal.

The plan back then changed over time and alternated between a bike engined and a Honda VTEC conversion. In the case of the VTEC a number of people are doing conversions now including P and L and Watsons. For bike engine conversions Z cars are the only people to talk to and have some good pictures on their site.

Current thinking

One of the problems with a mini conversion is the engine bay is very small, and short in particular which is why most conversions either use a clubman nose which is slightly longer or they graft in an extra 6" into the nose. After talking to Steve Wiseman I've been convinced to look at the subaru engine, which as a flat four arrangement is incredibly short but is quite wide. There is no doubt that it would fit into an unmolested nose but the width means that some very wide arches would be required. I spent a while looking at adding some extra width to a mini shell but concluded that it was going to be an awful lot of work. To accomplish it I'd either need to add the width down the centerline of the car and look at getting custom made glasswork, or add the width down the shoulderline and A posts of the car. Neither of these solutions really looked viable so I started thinking again.

One of the issues with putting a high powered engine in a mini is that driving through the front wheels the handling is difficult to get right. Wouldn't it be a lot more fun to do a rear wheel drive car, some modifications would be needed to make a tunnel big enough for the prop but that's a relatively easy hurdle to cross. I already have some wishbones from the westfield so it may be possible to set them up in the mini.

After thinking all this through I happened to make a huge leap forward when I discovered how the subaru drivetrain is set up. It actually uses a transaxle for both FWD and 4WD applications, the 4WD box just has a co-axial shaft leaving it which goes to the center differential and then back into the transaxle to drive the front diff. Simply capping this shaft off gives you a perfect basis for a mid engined car.

The thinking now goes along the lines of a subaru engine located roughly where the rear seats would be and making use of the wesstfield wishbones in conjunction with a new set of ali uprights and coilovers. A platic fuel tank would be located in the engine bay, as would a generously sized radiator, the battery etc. The engine bay could also be flat floored for practicality. Obviously a new subframe would be helpful in reducing weight and the old subframe could be used to make up a welding jig for the new one. I'm not too keen to run intercooler pipework the full length of the car since that has implications for turbo lag so either I will have to mount it at the rear of the car or go for a chargecooler setup.

One of the nice things about this plan is that the car should appear standard from the outside, although rear arch extensions may be fitted. Luggage capacity will be retained in the underbonnet area and in the boot. A custom rollcage, a re-sited fuel cap and a boxed ali area where the rear seats would normally be should be the only clues to the car's true identity.

Having done some more research I've been able to make up a scale drawing:

The engine really does seem a remarkably good fit positionally. In practice the engine would be somewhat lower than pictured and should be mounted on a removeable subframe which will have the wishbones attached. This will make it easy to fit and allow it to bolt straight into the roll cage.

For the purposes of future refence material I've started collecting useful images and documents

I've been doing some thinking about possible layouts and a front engined approach just won't work if you want drive to the front wheels using the standard subaru box. I do need to collect some measurements though to conclusively proove the hypothesis though so if anyone has the following I'd be grateful:

Even without the measurements though a front engined installation doesn't look viable. And the Mid engine, RWD looks like the only choice
Engine locationDriven wheelsProsCons
FrontFWD Predictable and safe handling, keeps standard car layout Driveshafts will run at a horrible angle to get them from the transaxle to the hubs, or the nose will need extending significantly
FrontRWD good handling, conceptually nice Need to find a way to lock the center diff to RWD or else a way to mate up a conventional box. Substantial tunnel mods. Poor weight distribution.
Front4WD good handling, conceptually nice Substantial tunnel mods. Driveshafts will run at a horrible angle to get them from the transaxle to the hubs, or the nose will need extending significantly
MidFWD Erm Need to either run the engine back to front or to run a prop from one end of the car to the other. Handling and grip would be lousy. Engine takes up a lot of the rear of the car.
Mid4WD Erm Need to either run the engine back to front, using a prop and idler gear to get drive to the front, where a diff would have to run uptide down. Engine takes up a lot of the rear of the car.
MidRWD Good weight distribution, good handling, conceptually nice Need to make up a new frame for the front end and panel that in, need a new subframe and suspension setup in the rear. Engine takes up a lot of the rear of the car.

Engine dimensions


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Chris Good