'71 Super Beetle Autocross Build

For road racing, autocrossing, or just taking that curve in style. Oh yea, and stopping!
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ONEBADBUG
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Re: '71 Super Beetle Autocross Build

Post by ONEBADBUG » Sat Dec 02, 2017 6:16 pm

Did you mean "Toe Out" in the rear, Frank?

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ChadH
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Re: '71 Super Beetle Autocross Build

Post by ChadH » Sat Dec 02, 2017 10:31 pm

FJCamper wrote:
Sat Dec 02, 2017 12:04 pm
You may know this already, but to really make a VW chassis a slalom car, don't use any front axle beam shims, get a ridiculously light flywheel, toe in the rear suspension to create tail-out swing just by leaning in your seat, and get a good solid seat and a harness. If you can breath normally with the harness bucked, it's not tight enough.
It's a Super, with struts, so no I won't use beam shims. ;) I'll have many (maybe too many) ways to adjust the front end, camber plates, easy/cheap spring swaps, some adjustability in caster, etc. I do have a 12lb flywheel to start. I have a new set of Sparko Sprints to install and will use 5-points when I get back to work on the chassis.
FJCamper wrote:
Sat Dec 02, 2017 12:04 pm
Have a working handbrake. No rear disk necessary. You should do about a third of your steering with the handbrake.

Once you can handbrake your car into a parallel parking spot against a curb you know you're good.
I disagree here. Maybe our courses have more flow that what you ran, but grabbing the e-brake would be a sure way to kill speed and cause havoc. It's all about smooth line and maintianing momentum. The courses are typically set up like a mini road course, with wide second gear corners and tons of room to pick a good (or bad) line. It's pretty rare that we have a tight 180-degree pivot cone, or have to grind down into first pivot the rear end and dig out of an exceptionally slow corner. It's also helpfull that I design about half of our local courses, and do set up on every one :)

I don't record my stuff, but here's one of our faster guys on one of our courses as an example.

https://www.youtube.com/watch?v=-s9A0BkUrhI
FJCamper wrote:
Sat Dec 02, 2017 12:04 pm
Cheat and get a 4.86 drag-race ring and pinion. Launch only in second gear after that for your own safety.

Get a short-shifter, a four-puck feramic clutch disk, and new shift-linkage bushings. Once you can make the transaxle scream louder than the engine on a downshift, you are formidable.
On our courses, the start is usually set up with a tight corner immediately off the start. This is to minimize advantages a big HP car would have from a dig, and help even out times between various classes. A little squirt off the line is somethimes helpfull in getting the rear to scoot around that first corner, but a drag race style clutch-dump will do nothing except create smoke, broken parts, and squarshed cones.

Half the reason for doing this car is so I can abuse the clutch without the cost and downtime of fixing a clutch on a modern car. I'm going to run a cush-loc to start (since I already have it) but once I get the car running, I anticipate the need to swap out things like the clutch, once I get the car reasonably sorted.

I have a hairbrained plan to relocate the shifter close to the steering wheel, and make the shifting action as tight as possible. We'll see if it works the way I'd like.

In the interest of cost and actually completing this project someday, I'll just be running the stock '71 tranaxle (4.12 I believe) until I inevitably break it. After that, I'll look into trying to optimise the transmission. I'm hoping I can get by long enough to scrape togeather the $$ for an LSD.

H2OSB
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Re: '71 Super Beetle Autocross Build

Post by H2OSB » Sun Dec 03, 2017 10:24 am

Hear hear!! Autocrossing in a nutshell. And, quite honestly, the super Beetle chassis is very good at it. They start out a bit under powered, but that's easily remedied.

johnL (aka H2OSB)
www.superbeetlesonly.com

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FJCamper
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Re: '71 Super Beetle Autocross Build

Post by FJCamper » Mon Dec 04, 2017 11:25 am

Hi OneBadBug,

Toe-IN. That makes the loaded outside rear tire steer the rear inwards, and is the quick way to snap oversteer unless you're good enough to catch it. Which is the point. We set up road racing cars just the opposite, with zero or even a slight amount of toe-out, to stop rear-end steering.

Rear Toe-in is like a gunslinger's hair trigger. Excellent for a pro, dangerous for everybody else in front of or behind the gun.

Chad, The SB front caster factory spec is two degrees negative. You need a caster-camber plate to adjust to zero caster. The car will then be easy to steer and have little to no forward self-tracking ability. You have to drive that baby. The first thing you'll notice is how much we depend on caster. At zero caster, you'll discover you have a car you can toss around at will but at no time can you count on the steering wheel recentering.

I see what you mean about your slalom courses being downsized road courses. I have myself seen this trend. In my opinion, a slalom course should be full of abrupt, tight moves. Think of a full speed race through city traffic. A slalom is not a scaled down road course. But, what has happened is modern suspensions and tires do not slide well, and the art of hand brake turns is being lost or is lost.

FJC

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raygreenwood
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Re: '71 Super Beetle Autocross Build

Post by raygreenwood » Wed Dec 06, 2017 12:51 am

FJCamper wrote:
Mon Dec 04, 2017 11:25 am
Hi OneBadBug,

Toe-IN. That makes the loaded outside rear tire steer the rear inwards, and is the quick way to snap oversteer unless you're good enough to catch it. Which is the point. We set up road racing cars just the opposite, with zero or even a slight amount of toe-out, to stop rear-end steering.

Rear Toe-in is like a gunslinger's hair trigger. Excellent for a pro, dangerous for everybody else in front of or behind the gun.

Chad, The SB front caster factory spec is two degrees negative. You need a caster-camber plate to adjust to zero caster. The car will then be easy to steer and have little to no forward self-tracking ability. You have to drive that baby. The first thing you'll notice is how much we depend on caster. At zero caster, you'll discover you have a car you can toss around at will but at no time can you count on the steering wheel recentering.

I see what you mean about your slalom courses being downsized road courses. I have myself seen this trend. In my opinion, a slalom course should be full of abrupt, tight moves. Think of a full speed race through city traffic. A slalom is not a scaled down road course. But, what has happened is modern suspensions and tires do not slide well, and the art of hand brake turns is being lost or is lost.

FJC
Extremely well said about castor. On the early McPherson strut suspensions.....411, 412 and super beetle...which are 3 point triangulated on the type 4 because they have a diagonal arm (radius arm) and a little less so on the super because they have no radius arm and utilize the front sway bar for this function and for strengthening for the control arm......castor is SUPER critical for these cars.

They can already have bump and wind steering issues on normal street cars....when they are short of castor. The spec for supers range from 2° to 3.2° on the street. The type 4 was hideously short from the factory at 1.45°. They all need right at 3° to prevent bunpsteer and tramlining...and to self center.....but the farther you get from 1.5° into + territory....the stiff, less responsive and more self controlled they get.

It makes total sense...having driven both 411 and super with effectively "0°" static castor......that it would be great for a track car....but you cannot take your hand off the wheel for a second....and you will need a serious lateral steering damper. Ray

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ChadH
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Re: '71 Super Beetle Autocross Build

Post by ChadH » Mon Dec 18, 2017 12:11 pm

I finally have all my old parts operating-room clean, and new parts in-hand to start building. I'm taking a week between Christmas and New-Years off of work, and plan on using much of the time for trial assembly, measuring, troubleshooting etc.

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I did find one more issue though. Two intake valve guides in my heads were loose. I've got a hookup to a machinist that sounds like he knows is VW stuff, so hopefully they're repairable. I'm not sure if these were the cause of some of my previous valvetrain issues, or the result. These are Scat Mini-D's, and the guide boss has been completely removed, which I assume is also a big factor. I had recommendations to get CB Los Panchito's, so if these heads are dead, I'll need to suck it up and scrape together some more money. :cry:

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Piledriver
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Re: '71 Super Beetle Autocross Build

Post by Piledriver » Mon Dec 18, 2017 9:37 pm

Even making custom oversize OD guides is a normal-ish thing, unless the heads are cracked up//overheated should be no issues.
I, for one, regularly embrace our new robot overlords, as I am the guy fixing the robots...

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ChadH
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Re: '71 Super Beetle Autocross Build

Post by ChadH » Tue Dec 19, 2017 10:32 am

Piledriver wrote:
Mon Dec 18, 2017 9:37 pm
Even making custom oversize OD guides is a normal-ish thing, unless the heads are cracked up//overheated should be no issues.
That's good to hear. The machinist I talked with indicated the same thing. The heads otherwise appear in very good shape. I've still got to get them into his hands though, and it sounds like he might not have time to get to them until after the new year.

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ChadH
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Re: '71 Super Beetle Autocross Build

Post by ChadH » Tue Dec 26, 2017 11:19 am

I purchased a pretty nice scale so I can balance parts as much as possible myself. The scale registers down to 0.1g. Out of the box, the Mahle pistons and wristpins had a variance of 4.7g. Since I don't have real machine shop tools, I carefully used a Dremmel to to lighten the underside of the crowns, by taking as even amount of material as I could.

The results are pretty good I think. I'm inside of what the scale will register, and i get variances of 0.1g, just depending on how I set them on the plate. I'm confident I'm inside of 0.2g. I'll recheck and adjust, if needed, with the rings and wristpin buttons later.

Rods are within about 1.0g. Those are next. I'll try to rig something so I can weigh and adjust both the big and small ends. This may involve some creativity with Legos. ;)

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FJCamper
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Re: '71 Super Beetle Autocross Build

Post by FJCamper » Tue Dec 26, 2017 2:56 pm

Hi Chad,

We also balance pistons and rods in house. We have a big-end/little end balancing jig for the rods.

The digital scales that came with our kit also balance to one gram. If you consider the Porsche factory once allowed a five gram tolerance for balancing, getting it down to one gram is significant.

Then again, the high-dollar pro balancers can get it down to one tenth of a gram!

I believe balancing your own parts adds a great deal to your confidence in your work. It's part of our ritual here.

FJC

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ChadH
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Re: '71 Super Beetle Autocross Build

Post by ChadH » Tue Dec 26, 2017 7:29 pm

Well - i thought I'd be a smart guy and balance rod ends with this DIY rig (the string on the small end goes to the ceiling.) I couldn't get consistent and repeatable readings though. I abandoned that idea for fear of chasing meaningless numbers. The overall rods all were within 1g, so I just shaved a tiny bit off of the big end to zero everything out as much as possible.

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Jadewombat
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Re: '71 Super Beetle Autocross Build

Post by Jadewombat » Tue Dec 26, 2017 10:39 pm

Yeah, a long time ago I went down to BAP with my scale and measured different sets of P+C. I went through 2 or 3 until I found something I could work with. I know the guys behind the parts counter thought I was crazy, but the most you can compensate for shaving the inner stuff on the piston skirts is just under 5 grams.

If matching the heaviest rod to the lightest piston still yields a combination more than 5 grams out of all four, well, not much can be done about it. If you're within 1g. though everything should be smooth as silk.

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ChadH
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Re: '71 Super Beetle Autocross Build

Post by ChadH » Wed Dec 27, 2017 3:39 pm

Hoover Mods. I think a more accurate description should be the "Oh sh*t, If I sneeze, I'll ruin a $750 engine case" mod. :P

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H2OSB
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Re: '71 Super Beetle Autocross Build

Post by H2OSB » Wed Dec 27, 2017 5:17 pm

Lol

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petew
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Re: '71 Super Beetle Autocross Build

Post by petew » Wed Dec 27, 2017 7:42 pm

ChadH wrote:
Tue Dec 26, 2017 7:29 pm
Well - i thought I'd be a smart guy and balance rod ends with this DIY rig (the string on the small end goes to the ceiling.) I couldn't get consistent and repeatable readings though. I abandoned that idea for fear of chasing meaningless numbers. The overall rods all were within 1g, so I just shaved a tiny bit off of the big end to zero everything out as much as possible.

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Why do you have a tea strainer on the tool board? :lol:

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