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Volks-Swap :: Other Conversions :: FR/R(M)R Polo? (long!)

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20:30:42 Tue
May 6 2008

1 posts

FR/R(M)R Polo? (long!)

Hi everyone.

Right now, I'm driving a Polo IIF that is nearing the end of its service live. Besides some minor body damage, I've had major engine trouble (malfunctioning ignition leading to a burned out cat converter), wavy steering (keeps pulling a bit to the right all the time and on a few occasions spontaneous heavy understeer in mid-corner for no apparent reason - no slipping tyres) and frame and suspension are getting a bit on the old side too ... and i'm about to finish school in a few weeks without any plans what is to come thereafter, so i'm thinking (commonly known as a bad thing) ...

Take the body off the frame (if it is body-on-frame, never really checked but hard to imagine it is not) and strip all the rotten crap. Fix the visible body damage, check for rust and maybe do something nice about the paint (disagreeable faded light blue). Get suspension, engine, transmission, driveshaft and rear axle from one or more donor cars. Rebuild and stiffen the frame, put in the new suspension and fit new engine mounts. Rework the underbody to make room for a transmission tunnel, the prop shaft and rear diff and put it all back together.

The perfect outcome of this would be an 86C FR with an NA engine around 80..120 kW (110..160 hp), 5 or 6 speed gearbox and rear LSD. Maybe double wishbones in the front. For the rear suspension I expect to depend very much on what rear axle I can find, but probably trailing arms. I want one with LSD, one with a clutch-type LSD would be nice, though any type would do. All-wheel disk brakes with adjustable bias/balance are a must.

Sounds fine so far ... to compensate i've managed to come up with these downsides:

- The transverse stock engine is shorter than I expect the average longitudinal engine I could come up with to be. Moving the firewall sounds like a major pain in the butt. I'd also have to move the front seats further to the rear then. (Effectively making it a 2+2 seater hatchback ... sounds stupid?) This actually has the advantage that the front wheels won't stick as much into the leg room anymore so i could actually position the pedals in front of the driver's seat. However i'd have to move the dashboard and steering wheel further to the rear too, which could become difficult. Also, it could put the front end of the engine quite close to the radiator. I'm wondering how close I can come without hindering airflow or risking interference between radiator and engine components as engine mounts are flexible to some degree by design. Another random though I had was using a V or flat engine like a V4 or boxer-4 or maybe a really compact V6. Mounted longitudinal these engines should be wider but shorter than an inline 4 oriented the same way - about the same format the stock engine has right now. On the other hand it would seriously limit the range of available engines/transmissions. I don't want a turbocharger, for one because i don't want to clobber the engine bay limited as it is even more, and because of a personal preference. I'd appreciate any input on this.

- As far as i can tell, this model isn't even theoretically designed to accept driven rear wheels so i don't expect to find any provisions for this built into the underbody or frame. This means some major underbody work is in order to make enough space for the new drivetrain. The stock tranny is located directly under the engine. I'd have to raise the floor so i can position the transmission and prop shaft while maintaining proper ground clearance. And if i remember correctly from when I replaced the fuel filter a while ago, the fuel tank is right where the prop shaft would go through. There is a compartment for a spare tyre between the rear wheels that could get in the way, but I could live without the spare (or put it someplace else) so this isn't really critical. However I would need to modify the fuel tank (and probably (re)design it too as 36 liters is small enough already and i don't want to sacrifice capacity for the shaft) and relocate the fuel lines.

Most of the above problems are connected with having to fit the new FR drivetrain in the limited space where the old one was located and into the confined space under the car which was never designed to accept one in the first place. So here's a new idea: The first part is identical to the procedure outlined above, as I'll still need to check and repair and most likely upgrade the frame and suspension. Then throw out the rear bench seats (making it a 2 seater). Weld in a rollbar and a firewall that connects to the body behind the front seats. Then there are two options for the drivetrain: Either get an FR drivetrain and shorten the drive shaft so the engine will go where the rear seats were, but this would need a really short engine and transmission to work as the rear wheels are right behind the rear seats. Or get the drivetrain from one of the many overpowered FF cars out there and just put it in the rear. Maybe tilt it forward a little to equalize weight distribution. Again, a V engine should provide good results considering its short nature compared to its power output. A theoretical third option would require me to get a hold of a purpose-build RMR drivetrain, but i don't think this is very likely considering that they are a rarity.

This would work around most of the problems connected with installing an FR drivetrain. And it would have a cool effect as one could look into the engine bay through the rear windows. :smile: However there are trouble spots again:

- I'd need to find a way to draw in loads of cold air for the radiator, engine bay ventilation and finally the engine itself. There are no suitable air vents on the rear part of the body. I could draw in air from under the car, but probably not enough unless when operating at high speeds. Routing the coolant lines all the way to the front for a front-mounted radiator sounds impractical, though I'd appreciate input here too. Or add custom air vents to the roof or maybe on the side. This would likely provide a sufficient ammount of air, but would allow rain and dirt to enter the engine bay more easily as well.

- I doubt that I can use much of the existing frame for this setup so some major frame redesign work here. I'd need to design fully custom linkages for all pedals and the shifter, probably retrofit a cable shifter. Also i'd really like to relocate the fuel tank somewhere as this setup would put it quite dangerously close to the engine and exhaust system, actually it may end up right where the oil pan needs to go. ... By the way, where do real midships have their tank usually?

And now the biggest problem that both plans have in common: How the ... do I get this monster street legal again?! Even though it would be cool enough for the track given a suitable engine, I'd need to tow it there and back every time.

Considering that I may have to do some major interior design work, I guess most of the panels in the cockpit won't fit anymore so I don't expect it to look very street worthy right away with open dashboard and console and open wiring.

In the end, it probably wouldn't come much cheaper than buying another used car and certainly not quicker. But it would surely be much more fun to do. And it would teach me a lot about car design. I haven't yet made my decision so I'd appreciate any input.


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