RacerBenz - My CL500 Track Day car build

Rear tower landing plates were extended rearward to allow for full contact of the cross bar. I extended the plate far enough to allow for another bar that'll live behind the cross bar as it's likely the rear suspension area will have a support bar that lands here, too. 

This pic also gives a good view of the bonding and riveting that holds all the aluminum panels together, as well as connects them to the steel areas of the chassis. I can't wait to get this thing back on the scales and see how we did re: weight reduction.

2 x LFX

For some reason that looks like some sort of DCT adapter to me? But you wouldnt need a flywheel for that, hm interesting!

In reply to SpeedAddict502 :

We have a winner! It is some sort of DCT adaptor. May as well disclose it now: The adaptor is LS-to-PDK, meaning the Option I drive train going in RacerBenz is a 981 Cayman S PDK behind an LS3. And yes, the PDK is here already - that's it in the pic, along with most of the adaptor kit. And apparently, you do need a flywheel, but the clutches are, of course, part of the trans; that's what you're looking at, right there at the front of the trans. What's missing in the adaptor pics is a stock LS ring gear. Throw one into the mix and the mechanical side is done. The factory Porsche transmission control unit (TCU) is replaced with a unit from HTG. They call them gearbox control units (GCU). I haven't yet ordered one but I essentially have no choice! It's just that I don't need it right away.

In any case, the GCU tuning is the complex part I mentioned earlier. There's some not quite simple programming involved to get the trans shifting "well". I've located a tuner who's well versed with the HTG unit so I figured, why not give it a go? Wish me luck. I mean a mid-engine, LS/PDK CL 500 endurance racer... what could possibly go wrong? 

Like this, but with a dry sumped LS3 attached and stuffed in the back seat! Can you tell I'm enjoying this build? Oh, I forgot. There's one more ridiculous element to this build that should start to take shape soon. I think you'll really get a kick out of it...

Enough of that, let's get back to the cage. Today was doing some additional demo of the extraneous brackets/sheet metal and general tidying up. I opted to squirt some primer on what's now unpainted metal, just to prevent any flash rust. Having a 5' x5' pool of water there in the plasma table does have an impact on raw steel. But IMHO, it's all starting to look pretty good.

Tomorrow, the cage gets dropped and final welding begins! 

Absolutely marvelous.

Here I've been thinking that an LS powered 80s or 90s AMG or 928 would be great. 

You're building a BAMF.

Why not UZ?

Love the build so far!

Haha nice!  I was thinking the PDK kit, I have been looking at doing a BMW DCT for a build, but the PDK has been considered for another one.

You are correct the tuning is the hardest part.  Will you be using a HTG ECU as well?  The more I researched I would go with a Syvecs ECU that talks with the stock PDK computer.  I think it would be easier to tune.  On the BMW DCT I was going to use a MaxxECU.

I will hopefully be starting a similar build soon but a wagon! :)

Cage welding began in earnest today. My good buddy Martin, who's been helping me with the cage build, is an unbelievable fabricator and welder. The quality of this build would be nowhere near as high without his participation, suggestions and skills. My TIG skills are OK so when Martin is available, I happily hand the torch to him! Here are some "action shots" from this morning's work. Dig his old school, non-auto darkening helmet. I've tried to convince him to upgrade and he won't hear it. Hey, it clearly works for him!

NSFW! A weld porn video, for your pleasure: Martin welding up the RacerBenz cage

And here's a partially completed joint. I mean, would you say no to having this guy weld YOUR cage? 

An interesting part of the build: Ahead of welding, angles were checked on the main hoop and A-pillar legs. Why? You've all heard of the distortion welding causes so it's a good idea to plan your welding order. This allows you to better control what moves more easily and what doesn't. Turns out the left A-pillar was tipped in a bit more than planned (like 1/2 a degree) and the right side wasn't tipped in enough, by about the same amount. It's not something anyone would likely have ever noticed but why not do all that can be done to make things as close to perfect as possible? (BTW, yes, the bases of all the legs are tacked to the rocker boxes.)

So... we braced the right side A-pillar against the chassis and wedged the not-yet-final-length dash bar in between the A-pillars, "encouraging" the left side out at the top. That side, upper area was welded. Then we removed the dash bar and went after the top area of the right side pillar. With no bracing, when the weld cools, the welding distortion (shrinkage) "should" pull the pillar in, improving the angle. 

Did it work? Take a look at this video and watch it happen! I started the video just after the welding stopped. Look real quick when the video first starts and you'll see the angle value starts at 89.4 degrees. Welding Movement

We checked again at the end of the day and it settled at 89.8 degrees. Nearly 1/2 a degree. The good news is it's now the same angle as the other side. The plan worked!

Rear shock tower cross bar has been redone to fit its new spot. With that checked off the list, I started playing with designs for the A-pillar cage-to-chassis gussets. If you've seen much of my 914 build, you know I tend to try out a number of different designs before landing on what I like. Version 1 here is 1" holes at the top, middle and bottom, with .75" in the other two. 

With most of the underside welding done, it was time to remove the rocker boxes and see if the cage would drop far enough to allow access to weld the tops of the joints. With a bit of persuading, it did! It worked out that the cage would drop enough once a main hoop leg or A-pillar leg was made to move outside the car. That was fun - not.

Once one side and the top side at the center of the main hoop was done, the cage was wrestled back into the car and the same process happened on the other side. Then it was get it all back inside, refit the rocker boxes and start all the final welding. All but a few areas were completed today. A few more hours of welding and the main cage will be finished. It's looking pretty nice!

With the rocker boxes out and the cage lowered, I couldn't resist adding some matching style points to the box. It took about 5 minutes to dimple the front panel.

Anyway, as the final cage welding was proceeding, I ran into an interesting issue: a part of RacerBenz's chassis aluminum starts just behind where the main hoop lands, right where the last couple inches of the top of the main hoop rocker box "should" be welded. The surprise came when all of a sudden, welding the rocker box to the chassis went all to crap! I have to say, it seemed an odd location for the material to change, but there you go. So, what to do?

I looked at and mocked up a couple options but in the end, opted for what you see here: gussets that tie the main hoop leg to that giant 1/8" steel cross member. This gusset is two pieces of 1/8" plate that weld to either side of the main hoop leg then tie back to the cross member about .6" apart. Then I plasma cut a little cap to tie them together at the top. I think this qualifies for a "Well, THAT'S not going anywhere!"

Also of note, while welding the rear rocker boxes on, there was some residual foam/insulation trapped inside a panel and it caught fire. Nothing serious, a quick blast with the air hose and it was out.

So - RacerBenz has injured me enough to warrant an ER visit and now, has also caught fire. I take this as a good sign: the car is getting these things out of its system NOW and will not do them ever again! 

Here's something you'll get used to hearing from me: Change of plans...

With the majority of the cage done, I wanted to focus on the suspension. 

Rough mock up shows the size and shape of the PDK trans don't really get along with the size and shape of the 'Vette frame rails / cradle. So... let's use the 'Vette parts to make a jig that replicates the needed pick up points for the A-arms, toe links and sway bar then make our own cradle. It should be lighter and, most importantly, allow for a design that has room where it's needed. Given what I learned getting the LS/Boxster set up into my 914 and moving it 1.5" forward from where it otherwise would have been, it's a no-brainer to copy the essence of that design: the engine mounts to a removable cross bar, the trans uses the stock Cayman mounts (one on each side, one at the rear) that mount to the chassis and the whole drive train goes in / out from underneath (not that there's any reasonable alternative).

Also planned is a mod to RacerBenz's chassis cross brace to enable the drive train to move forward as far as possible. Hey, it worked in the 914 and it should work here! If all goes as I hope, I'll have acceptable axle angles and shift all this weight ~ 4"-6" to the front. 

Awesome!

The 914 firewall was a work of art, I look forward to this one!

A quick trip back to the cage. With a bit of time to spare, I fitted the sill bars. Then it was giving a go to the planned interior color: Smoke Gray from our ol' friends at Rustoleum.

I'm sure it varies, but if you're reading this, you're at least sorta interested in this build so I'm curious: Do you folks care to see all these 'along the way' steps or do you prefer more progress between posts. Lord knows, I'm here to keep you happy! 

I'll read everything you write. Great build so far!

You could post about how you made your coffee while you were thinking about what to do next and I will read that with a smile. 

I hope your main hoop is far enough back, many place it just behind the door pillar.....  In that position it can  get in the way of elbow room and bending the bar wrecks rigidity.

That bar often needs to be farther back, remember the bar that goes behind the seat has to be straight and keeps the cage from collapsing in a side impact.

I'm a big fan of all the detail plus all the photos, and I appreciate the why as much as the how. Carry on!

Chris, as long as you have fab work into it, I'd watch you toast toast.

Once again if you have not seen it go see his work here:

http://www.914world.com/bbs2/index.php?showtopic=296900