B3 vs B4 track/canyon/auto-x/sleeper car

[Audi_From_Hell]

Looking at b3 and b4 80 quattro sedans. The car will see auto-x and canyons exclusively. Power to weight ratio will be of utmost performance. I will be swapping in a 07k and 01e no matter which car I choose. Probably run an efr6258, only looking for 400hp. The car will be fully gutted and caged with a semi tubed front end most likely, no creature comforts. I'm looking to get as close to 2500 -2600 lbs with driver if possible, sub 2850 lbs is a must. The exterior will be completely stock looking aside from wheels, brakes and being on coils. I will be doing all the work, including any fabrication needed.

My questions are:

Is it worth starting with a b4 instead of a b3? I like the shorter wheelbase and lower starting weight of the b3, but prefer the double wishbone rear suspension of the b4 which is much more planted at speed. Any fixes for the rear being so twitchy on a b3? Obviously locking down the subframe, tubular arms, and higher spring rates help.

Can the b4 be stripped down to be as light as a b3 that's been stripped? I would assume the b4 would still be a bit heavier but are we talking 100-200 lbs or 300-400 lbs? Obviously weight is a big deal, I'm going for as light as possible. I know the b4 isn't that much bigger but from the factory it was 400-500 lbs heavier, part of that from being more luxurious than the b3.

I've also contemplated a 4000cs quattro and b5 a4 for this project but I'm quite partial to the b3/b4 80 look. I'm also not interested in anything outside of audi and awd, just want to make what I love work.

Thanks in advance.

[Ruffiano]

I've owned many b3 and b4s. Here are my thoughts:


Go b4.
Pros of b4 over b3:
Better suspension
Wider fenders
Larger wheel wells
All b5 s4 parts can be used for 01e swap (rear diff, drive shaft, ect)
Seats fold down in the rear
Better bumper options
If you are going 07k, it also already as a front mounted radiator, should make that part easier.


It's a no brainer in my book

My b4:
1.8t swap had k04, going gt2871r, kw coilovers, porsche bbk, BOrla exhaust, ect

[Audi_From_Hell]

Beautiful car, very clean. It's nice to see these cars being taken care of.

A few things:

Rear seats don't matter, the entire interior will be gutted. Every single thing that can come out will.

Bumper options aren't of a concern to me, this is purely a function over form build. Wider fenders are nice but I can roll and massage the fenders some if needed, I'll be running very sticky tires anyway.

Radiator doesn't bother me, I plan on chopping out the entire service carrier and building a tubular one.


So what it's coming down to for me is the rear suspension and swap ability of parts from the B5 platform. I already have two full 01e drive trains and an 07k. I also have two apb 2.7ts but I prefer the weight savings of the 07k and it makes just as much power. Weight is my biggest priority but I'll sacrifice a bit to make up for it with a better rear suspension design. As long as I can get a b4 down to 2700lbs fully gutted and caged with driver I'd be happy. The idea is to keep the cost of this build down by using parts I already have on hand and fabricating everything myself. I already have most of the powertrain and driveline, just need a chassis to slap it into and work out the suspension. I have a few parts cars (b5 and c5) so I have plenty of parts to work with and I can weld so fabrication is no issue.

The b4 is looking more reasonable for the rear suspension, swap ability of parts from the B5 platform, and wider fenders to fill with more meat. The only thing that keeps pulling me back to the b3 is the low weight which is a big deal in auto-x.

[Ruffiano]

its not just wider fenders, its larger wheel wells. The b3 sedans have a smaller rear wheel well that makes fitting 'normal' size tires hard. If you have ever seen the "vomit comet" Jim had to do TONS of work out in the rear to make his car fit proper tires (he is running an 07k with 01e)

[Ruffiano]

oh and fold down rear seats actually is more about wehre the gas tank lives. the b3 has its gas tank mounted up high and it is where the rear seat is, the b4 has a low mounted fuel tank


Also you said you dont car about bumper, truth is, you should. it is a consideration to be made. European style bumpers weight a 10th of the US equivalent, and also allow for larger intercoolers to be installed.

[Audi_From_Hell]

The car will be competing under scca solo prepared category.

It will have a fuel cell so the tank is of no concern. It's coming out.

The entire service carrier will be made of aluminum so the bumper will literally only be a cover, no reinforcement at all and I will hack it up if necessary. I will also be tubing the front mounting rails and strut mounts. If you have seen James' s2 (terry bullwon on s2forums) I'm essentially going to be copying him minus the tubular subframe. Just imagine all the removable aluminum structure being welded in place and not chopping off the frame rails.

It does seem as if the b4 would make for an easier time getting everything in and rolling.

[totalrecall]

Beautiful car, Ruffiano. I love seeing how well others restore their vehicles. It is an inspiration for me, truly. I get impatient to get started, but seeing the hard work of others really keeps my eye on the prize.

[Mcstiff]

I don't think the B4 carries much of a weight penalty, I have not had mine on a scale but the builder claimed sub 3k with full interior (no AC & manual controls). At the time he had a CF hoof and lighter wheels, among other things (click the link in my sig), but I doubt these 2 things account for more than 100#.