Semi-automatic?

Hey folks,

After getting a quick ride in Cam's car while in Texas (thanks again!), I continue to be intrigued by the SL-C. In further research, I'd really like to explore the idea of doing a semi-automatic gearbox. I know there are a number of aftermarket bolt-on units for various transmissions, so you could to LS376 + Ricardo + Geartronics for example, but that feels like a lot of "moving parts" (figuratively) due to multiple vendors.

However, in seeing Fran's suggestion of a Cayman/Boxster drivetrain and being a bit of German car purist (I grew up there), I thought why not just take a PDK Cayman/Boxster S drivetrain or even an Audi R8 system and move the whole thing over vs. taking parts from 3 or more different vendors. I couldn't find anyone in the forum postings as having done either of those systems, so I have a few specific questions:
1) Has anyone done or is in the process of either the full Porsche or Audi drivetrain? (Or you thought about it and gave up - that would be excellent info too)
2) Am I crazy to want to do a semi-automatic? Mainly, I'm interested in the challenge.
3) If I'm not totally crazy, what are some potential pitfalls? I know the R8 is an AWD system. Does that pose any issues mechanically or with the software?
4) Are there combos of other components you'd suggest? LS376 + G50 + a G50-specific bolt-on system maybe?

Thanks,

Tim

I did think about the V8 porsche in the cayenne, the S has 400hp, mated to a flipped porsche transaxle with paddle shift. I sobered up and did a SBC and a G50.

Note: the first choice has a lot of electronics the second has none.

Hey Howard,

Interesting idea on the V8 Cayenne engine. Pretty decent availability of those it seems, though there's no PDK for the Cayenne yet from what I can tell, so what semi-automatic transaxle were you thinking? The ZF 7DT-45 (a.k.a. PDK) from the non-Turbo Carreras and Caymans?

Related and slightly dumb question: how does flipping the transmission work? Is it literally mounting it upside down since it would now be behind the engine, not in front of it, not any alteration of the internals? Is that what Porsche does with the ZF to fit in both Cayman and Carrera?

Thanks,

Tim

You could always go sequential with the griffin transaxle. That's what I plan to do in my car. Already talked to them and have just about everything set in stone.

Tim.......... Porsche GB's that are sourced from 911's are as you say in front of the engine and need to either have the ring gear reversed or have the GB flipped. The G50XX series work well upside down with very minor modifications (discuss with your Porsche GB guru) but I am not certain how the newer types would work in this fashion such as the new Carrera 911 types. I also am not sure where to source the adapter plate if it's needed to mate a new 6 speed Carrera box to a V8 Cayenne.

The faster easier way would be to run a flat 6 Cayman S power train but I think SLC's would be better suited to more that it's 320HP. Closer to 500 is my preference like the Cayenne S @ 400HP.

Adding 200 odd hp to a modern Porsche 6 would be thousands of dollars at a minimum. Much closer to $15K or more than $5K I would guess.

In the end it came down to cost per HP. My 350 Chevy @ about 500hp cost me less than 5K to build myself with a free 4 bolt block. Hard to beat. That's about a buck a HP. The Porsche would be north of 5 or 6 times that and then you have to get the electronics working, make a lot of custom stuff, and tune it.

Why not give California Motor Sports a call and ask about a new semi auto Porsche to mate to a LS Chevy. Let us know what you find out.


http://www.californiamotorsports.net/

step 1 - stick 1000hp LS in it

step 2 - stick a Ricardo behind it

step 3 - done :idea:

Too much hassle to try to make it work imho

haha if it were that easy then Alex would be done with it....

Howard, check your decimal places....

What I mean is ADDITIONAL cost to ADD 200hp to a Cayman S motor

$10K turbo kit for cayman s 450HP

http://www.tpcracing.com/products/TPCRacing-987-Cayman-S-Turbo-Kit/

Throw another $5K onto the cost of a good G50 and I think you might be close.

Tim, a tiptronic from a 964 porsche would bolt right onto a SBF/SBC with the same adapter plate as for a G50. Not sure if the tiptronic would work OK upside down however! You could see if the ring gear might flip so that you could leave the thing in the normal orientation. The 2WD tiptronic from a 964 is relatively basic in terms of additional sensors and inputs needed to make it run right.

If money is no object you could use a f-car 430 engine and gear box.....already in the right orientation (no need to flip).

Just a couple ideas.

ebaker said:

You could always go sequential with the griffin transaxle. That's what I plan to do in my car. Already talked to them and have just about everything set in stone.

Click to expand...

Wonder if Griffin would do a group buy...I'd be in for that with my build coming up shortly :thumbsup:

Sorry Ken ...no group buy

The box will be available once we are happy with everything about it and not before...group buys with a new product create unnecessary pressure on the suppliers...
The pricing on the Griffin is already good and the aim is to keep it that way...across the board.

I'm in for the griffin no matter what. Just talking to the owner/founder of the griffin gearbox has won be over. The stamp of approval from Fran and the gang is a huge bonus.

Hi Tim,
I've been looking in to this as well. So far the hurdle seems to be finding an sequential transaxle that can handle your power levels that uses helical cut gears and non-dog synchros. There arent any I can afford. Example, the G50-G96 boxes were produced in sequential straight cut dog engaged by Ricardo, Hollinger, and Quaife. I've seen them used for ~$10K. Someone like CMS *should* have helical gear sets and synchro style engagement retro-fits to these boxes. Figure another +$10K minumum if it can be done. Someone should call CMS or Guard Transmission or whoever and see if they can do this.

Personally, I'll wait for Griffin. His recent email to me stated that even if I bought an H pattern box, once the sequential was running he'd be able to retrofit my box. Richmond gears sets are CHEAP compared to Porsche.

Once you get that sorted, this company

Shiftec | Paddle Shift | Professional Shift Kit
Shiftec |Clutch Control Unit | Paddle shiift | Close Loop System

has both paddles and clutch control (i.e., clutch pedal removal) that are CAN closed loop control. I'm not saying they are the best or the cheapest, but, its being done regularly.

Its definitely on my "can I pull this off it would be epic if yes" list.

as an aside, I got a quote from X*tr*ac for the transverse sequential box thats supposedly off the shelf. just the box zero controls is over $100K.

Cheers,
MeLoN

Doesn't the 01 car have paddle shift? Which gearbox is in that car?

mpg said:

Doesn't the 01 car have paddle shift? Which gearbox is in that car?

Click to expand...

Paddle shift isn't difficult. Clutch controlled (no pedal) is. There are kits to convert the G50 to paddle shift. You still have to push in the clutch.

Hit send too fast. Also straight cut sequential dog engaged Porsche gearboxes aren't rare and are perfectly adapted to paddle clutch controlled shifting. Nightmare to run on the street.

A sequential helical gear transaxle with synchros (street friendly) is unicorn rare or expensive.