I don't actually see anything in the rule that says you can't modify a fuel tank. Rule says OE tank in original location. Doesn't actually say OE tank for a blue 78 VW, just OE. Original location is behind axle under car, I don't think we have GPS co-ordinates for it however. I certainly don't know which VW has a steel tank or plastic tank..not on the tech sheet either. Whatever you do , be safe ! Look at the plan and really decide if it is something you would let your wife or kid ride in at 100 mph. I'll check with upstairs though on tanks...

I had a stock gas tank modified when i put 4wd drivetrain into a 2wd car.

took it to a gas tank rebuilder with some paint marker marks on it, and the guy had fun.

He welded it, sealed it up with all his fancy stuff, and pressure tested it! was as good as new...maybe better!

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Chris

Bringing this back from the dead as I completed the install. Everything worked out perfectly - although now with the wider suspension I'll have to do something to the fenders to stop them from rubbing - but nothing a cut off wheel can't fix.

Time for the pics:

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-Jason

plate those rear arms....going to run 9.4" out back or 10.1 out back with a 11" front?

this is a cool idear, how is weight and ground clearance?

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-Tom
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I'm trying to understand if I'm looking at things correctly. Is the rear front subframe in backwards relative to the front front subframe?

-Dave

yeah it is facing the opposite direction that the front one is

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-Tom
DemonRallyTeam | Fine Tuning | CTS Turbo & RP Turbos | RalleyTuned | JRM | Meister Autowerks
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Weight feels a little bit less than the stock beam - but not by much. Don't worry about plating the arms - It will be done. This is just so that the car can roll around.

Ground clearance is the same as the front - it is level with the front subframe. So no loss of clearance.

Probably going to run 11" rotors, keep them the same as the front. Calipers are going to be MK4 rear calipers for vented rotors. I just need to build an adapter for them now.

And yes it is turned around - by turning it around 2 of the mounts land perfectly on the existing frame rails. If I had it the other way I would have to build 4 mounts in the middle of no where and it would also limit the available trunk area which is where the fuel cell will now recess into the floor.

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-Jason



Edited 1 time(s). Last edit at 06/22/2009 10:18AM by mack73.

Good packaging argument for going backwards. I think there might be good geometry arguments too. Most front suspensions are designed to toe out slightly under compression, and by reversing it, you're making it toe-in. That's a better thing to have in the back...

-Dave

eyesoreracing Wrote:
-------------------------------------------------------
> Good packaging argument for going backwards. I
> think there might be good geometry arguments too.
> Most front suspensions are designed to toe out
> slightly under compression, and by reversing it,
> you're making it toe-in. That's a better thing to
> have in the back...
>
> -Dave


Also, by having the toe links in the front they are under tension and much less likely to bend when the wheel hits a big rock or something. I would have oriented the subframe that way just for that reason. For example, Subarus have the tie rods in tension and they hardly ever get bent. Evos have the tie rods in compression and they get bent all the time.
Also, don't be tempted to over strengthen the a-arms. You want them to be a "fuse". If you hit something hard enough something will bend and you want it to be the a-arm and not the crossmember. A-arm is much easier to replace. On the VW a-arms do not plate the top and bottom, plate the sides. That will stiffen it up but still allow it to give if it's hit really hard. It's how we do the Porsche 944 a-arms (which are the same as Rabbit a-arms.) I'll try to come up with some pics.

Excellent point about the tie rods in tension!

-Dave

I am interested to see how this turns out. It would be really neat to do a skidpad test to see if there is any improvement or deterioration in road holding from the swap.

Audi 4000's had a front subframe in the rear and ended up with significantly slower skidpad and slalom speeds compared to the VW Quantum which was identical except for the rear suspension which used semi-trailing do-dads.

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____________________________________________________________-

One. Class -- 2WD

www.quantumrallysport.com

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You sure that wasn't the difference between Quattro and FWD models?

HUGE weight difference in that case.

-Dave

eyesoreracing Wrote:
-------------------------------------------------------
> You sure that wasn't the difference between
> Quattro and FWD models?
>
> HUGE weight difference in that case.
>
> -Dave

Both were 4wd models--Audi 4000 Quattro vs VW Quantum Syncro Wagon

Same 4wd system, motor etc, and exactly the same in-front of the B-pillar.

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____________________________________________________________-

One. Class -- 2WD

www.quantumrallysport.com

http://www.facebook.com/home.php?#/pages/Quantum-Rally-Sport/281129179600?ref=nf

Josh Wimpey Wrote:
-------------------------------------------------------
> I am interested to see how this turns out. It
> would be really neat to do a skidpad test to see
> if there is any improvement or deterioration in
> road holding from the swap.
>
> Audi 4000's had a front subframe in the rear and
> ended up with significantly slower skidpad and
> slalom speeds compared to the VW Quantum which was
> identical except for the rear suspension which
> used semi-trailing do-dads.
>

Yeah so am I. A sway bar is being put in so it should help it out. No way I'd run IRS with no sway vs oem beam.

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-Jason

eyesoreracing Wrote:
-------------------------------------------------------
> Excellent point about the tie rods in tension!
>
> -Dave

Seems just a point of view, and the yield should be the same in straight compression,
or straight tension, as far as I know.
Maybe some Gen-you-whine mechanical Injur-near like Tim Taylor could elucidate a bit for use. I could see something in severe compression buckling when a side load would be put to it, but other than that can't see a difference.

And Dave are you smoking some spliff here?:

Quote

Good packaging argument for going backwards. I think there might be good geometry arguments too. Most front suspensions are designed to toe out slightly under compression, and by reversing it, you're making it toe-in. That's a better thing to have in the back...

First, 'splain why rubber bushed cars tow out slightly (a simple drawing of a box and two arms sticking out and force vector draw would answer this---force ^ arms with tires resist going that way, bush complies and arms boing rearward, and the say 2mm toe in becomes say 0,5mm in.)
Why does that same thing, rearward deflection this away V result when the same rubber in in back, and the car drives forward?

I would suggest if a person were doing this they would assure themselves that the bush compliance doesn't become toe out, unless of course they're into drifting and want snap oversteer at 20 mph.

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John Vanlandingham
Sleezattle, WA, USA

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