Beetle 1303 Turbo circuit racer build thread

[4agedub]

With all our other projects being finalized, the 1303 is next. Over the last couple of years we have progressed to the point where my current turbo circuit racer has just become too fast for the current setup. We are on the limit of the chassis and the roll cage surely was not built for the speeds we see with the turbo engine.

During the year I found a good solid 1303, these are real scarce in South Africa... you even battle to find ball joint cars here. VW only built link pin / swing axle cars locally.





The car does have some rust, but is intact in all the right places.

The plan is to use the engine and gearbox from my turbo circuit racer and move it to the 1303. The engine is 2176cc turbo t1 that makes around 180kw on the wheels and almost 400nm torque.

Over the last six months I have slowly started collecting some parts for the build.

Porsche 944 s2 rear trailing arms with brakes and complete front stub axles.




Uniball system that will enable us to run rear coil over shocks and eliminate the torsion bars. The rear shocks are from GAZ with 550lb springs to start off.


Front shocks (Koni Yellow), sway bars and ball joints from Kerscher performance



Camber plates from Silver project in Poland


Pedal box with master cylinders from OBP performance


There is plenty of custom parts in the making.... eg shock tower mounts that will brace the towers


Some progress on the body...



Dog box removed to make space for the turbo

[Steve Arndt]

This should be fun, tuned in. I just acquired a 1303, same color even.

[4agedub]

Strut brace components arrived from the laser cutters today

[aircooledtechguy]

Nice!! I look forward to watching this build progress. . .

[4agedub]

Strut brace assembly in progress. Tig welded with 304 stainless wire. The braces to the front suspension still needs to be added, but those I can only do once we have determined the exact position they need to go to.

[turbobaja]

Looking great! The best stuff is home-made, nice work!

[FJCamper]

Hi 4AgeDub!

Wow -- welcome to the almost-a-911 world. We have also just bought a set of the Polish camber/caster plates for our Blitzwagen.

I'm glad to see you have the 944-rear diagonals, and the brakes that go with them. I don't know if you'll need to fit a 944 master cylinder or not.

I believe you'll find the rear coilover suspension to be a demon tweak, in combination with the more adjustable front axle. The cornering limit of the Superbug is reached once the body rolls too much, on the loaded side, the wheels cannot get enough negative camber to even stay level. That's why we bought the Polish adjusters.

I'll be interested to learn if you guys end up using a rear sway bar or not. We tried both a light and a heavy rear bar and felt the factory induced understeer (fast and slow) was safer.

FJC

[4agedub]

FJC

I don't know if you'll need to fit a 944 master cylinder or not.

We're going over to a full pedal box from OBP. I did give them all the caliper dimensions on which they supplied master cylinders. At least now we can adjust the front / rear braking bias

I'll be interested to learn if you guys end up using a rear sway bar or not. We tried both a light and a heavy rear bar and felt the factory induced understeer (fast and slow) was safer.

Interesting you say that... our swing axle bug is simply the other way around. If you loosen the rear it under steers like crazy, the tighter the rear the better it turns in and stays stable throughout the fast sweeps.

[4agedub]

As for adding camber, we plan on making new bottom trailing arms that are about 5mm longer to start off and is adjustable with a heim joint on the inside. Caster will be adjusted on the top mounts

[FJCamper]

THE 1303 AT SPEED

This photo captures a near max-G fast corner for us. Notice how far the driver's head is tilted to try and keep his "sight horizon" level, a mistake in racing, as you should keep your head as erect as possible so as to be aware of yaw.

The left hand side of the car (our driver's side) is loaded with all the G-forces. The tires on the unloaded side are off the pavement. The shadow under the tires makes them appear to have contact.

But the point here is the this photo has caught our 1303 precisely at the instant in which any further body roll would begin to lift the inner tire contact patch, losing adhesion.

***

Once at speed, don't expect the four-joint rear end to feel or act like a swing axle, only better. The four-joint promotes understeer at all times, and if aligned correctly, less abrupt turn-in (contributing to a spin) than a swing axle.

The four-joint is easier to drive faster.

FJC

[4agedub]

Thanks FJC. I always thought the IRS suspension would have the same kind of feel as a old school 930. They were pretty prone to be snappy and over steer quickly.

This is a complete new venture for us. I have never even driven an IRS car on the road... So plenty learning coming up

[Piledriver]

A 930 has a lot going against it: ~500++Lb of motor (all accessories included) hanging out well aft of the rear axle.
(I have seen values well north of 600 Lbs mentioned but I can't see how, unless they have really beefy heat exchangers/exhaust)

From memory, a 5.7L chevy motor with alloy heads and intake is lighter, no worse than a wash all included.
A turbo T1 might as well be mid engined by comparison.

I'm still wondering if a 928 Weissach rear axle setup is worth modifying, or fabricating a work-alike.
Too long to fit in a std T1/t3 etc, but the basic design and even the trick bits up front could work.

Should work wonders preventing the dreaded bad habits of a rear engined car, it would be easy to add camber gain or set camber as needed if using adjustable rear top/bottom links vs the stock flexi lower bar setup.

[FJCamper]

Hi 4AgeDub,

Those 930's needed huge tires in the rear.

What you ought to feel as a first-timer to the "IRS" is the lower rear roll center. I'd been driving nothing but swing axle VW's up to 1972, bought a brand new '72 Ghia, and I almost felt as if I leaning backwards the rear roll center was so low.

Stock IRS cars are more stable than stock swing axles and not as easy to throw around.

The 1303 front strut geometry was designed to understeer, and it does. And for those of us accustomed to front axle beams, especially king pin beams, the 1303 front suspension is light and delicate. We managed to bank-shot ours into a wall at Daytona, full sideways, and the worse it would have done to a beam axle might have been a broken wheel and bent trailing arms on the impact side. The strut's steering rods and sway bar transferred so much force to the other side that we also lost the nonimpact side parts!

Lowering a 1303 is the best single thing you can do to it. Your plan to add a strut-top brace is an essential as well.

One final caution for this post. Good 1303 steering boxes are hard to find here Stateside. They may be unobtainable for you locally, but you can source Europe. It may be possible to graft in a 1974 rack and pinion!

FJC

[Piledriver]

...
One final caution for this post. Good 1303 steering boxes are hard to find here Stateside. They may be unobtainable for you locally, but you can source Europe. It may be possible to graft in a 1974 rack and pinion!

FJC

Hopefully it will get a rack.

Audis have been mentioned as a source of usable steering racks, search here and on superbeetlesonly

I recently welded some Mk1 Golf ball joint-holding ends on 1302 lower arms, while in the process stretching them a bit so camber adjustment range worked out well with 944 struts... and much to my delight I disovered I can now flip the whole arm, that moves the sway bar ~3/4" lower vs.centerline (~35-40mm lower than original) providing extra clearance for lowering vs the steering link. (I wish I could say I planned it)

Nice forged steel arms too vs the origami sheetmetal 1303 version.

[4agedub]

I have not really researched the rack options yet, the box that is in the car currently is in excellent condition.