GTgears

Hello,
I've got a little bit of an odd ball question. I found a good deal on an '07 base model with a blown motor. I'm considering picking it up and wondered if a crate DFI engine will bolt up to the gearbox. I'm not so worried about the electronics and the ECU. That's pretty straight forward. I'm just trying to figure out if I need to replace the gearbox at the same time or if I can just use the one that's already in the car.

TIA for your answers.

Wanderer

I'd love to see this happen as I am interested in doing something like this in the future with my 08 Cayman S. Would you use a 3.8 or the 3.4 DFI?

Macster

Assuming no one has solved this and I don't believe anyone has, the electronics/ECU worries me. Alot.

The DFI is of course direct fuel injection and my info is that many times more than one injection pulse is used.

No way the old Ecu would know about that. With the old Ecu delivering one shot it would be a miracle if the DFI delivered its advertised HP and it might not run at all or worse run then suffer some kind of failure.

Plus you have to worry about the high pressure fuel system. Plus are the sensors on the new DFI engine compatible with the old engine's sensors and the info they supply.

I'm sure to there are new sensors that the old Ecu most likely doesn't know about, maybe has no Ecu inputs/outputs to read/control these sensors. Like the Ecu controlled high pressure engine oil pump.

For the engine/transmission issue one way is to get both the original engine and the the new DFI out side by side and test fit the desired transmission to the orignal engine and note very carefully the transmission hard point locations. Then move the transmission to the DFI engine and again note the locations of the transmission hard mounting points.

Then compare the locations and see how closely they match/line up. Where they differ (sure assuming they differ) and how much determines what kind of effort you're looking at.

As always even if these hard points line up there will be other mechanical issues.

Unless you have superior car modification skills, or know some who does and can afford to write him almost certain blank check, your best bet is to replace the engine with something as identical to it as possible.

Were I in the market for a Cayman S I'd look for one with a blown engine and for sale cheap and have a new engine fitted. This is the cheapest/best solution long term and the one most likely to deliver to me a car that has no Frankenstein engine transplant issues.

Sincerely,

Macster.

GTgears

I was one of the first guys in the country wiring JDM WRX engines into old GC chassis Imprezas. The first one took me 100 hours. By the third one, the wiring took me less than 25. I've also installed an EZ30R H6 engine in twin turbo configuration into a WRX and wired it to run with a Vipec. I know my way around a chassis harness and an ECU and don't really worry too much about that stuff. You could say it was part of one of my previous careers.

My initial consideration in this instance is strictly mechanical. And while your suggestion of getting the two side by side is practical, I haven't decided yet if I am going to buy the car. I would consider it ready, fire, aim to buy the car and then assume I can do this engine swap. If the DFI engine won't bolt up to the gearbox, it doesn't mean that I won't buy the car for a project and look at other engines (like a 996 engine for example). But I'd like to explore if a DFI engine is even an option.

Macster

Ok then with your background the electronics/Ecu may not be a problem.

The job then becomes more a mechanical task. Like putting a square peg in a round hole type of thing.

A 996 engine is nearly a drop in and a path many have taken, though not so many with the Cayman. They're a bit young yet to get this treatment. But I'm sure you're aware of a goodly number of Boxster owners have gone this route.

Sincerely,

Macster.

jmazz

GT, I've had this same question in the back of my mind for a while. I have a base Cayman and have visions of someday going to a 3.8. The funny thing is I was thinking you might be the guy with the answer. I'm also curious how the 5spd would hold up to the power.

I'm assuming 3.8 pre-DFI and 3.8 DFI have the same bolt pattern, I could be wrong there. Then, I know the Cayman 6 speed bolts to the old 3.8. And I know the 2.7 can optionally come with the 6 speed, so in an A=B=C=D sort of way that makes me think the 5spd should work on a DFI. Of course, I'm not willing to make that bet without some proof either, so please let us know if you find out for sure.

Any thoughts on the strength of the 5 speed? For a budget swap, keeping it makes sense. But it also makes sense to put an LSD into it while it is out. But throwing that kind of money at a tranny that may explode due to the power is not worth it.

Macster

As long as one doesn't play John Force with the car at every stop light the 5-speed is pretty robust.

My second hand info is the 5-speed holds up pretty good. There have been many early Boxsters fitted with 3.2, 3.4, 3.6 engines (and one fitted with a Turbo engine) and most of them stick with the 5-speed.

Were I to do an engine swap replacing my 02 Boxster's 2.7l engine with something bigger, I'd probably just stick with the stock 5-speed and worry about a beefier transmissione when (if) the 5-speed gave up the ghost.

(However, the stock 5-speed has over 240K miles on it and while the transmission feels fine and behaves fine I might be tempted to "while I'm there" to at least look into having the transmission freshened up a bit or even replaced with a younger 5-speed or even a younger 6-speed.)

Sincerely,

Macster.

BGB Motorsports

If you want DFI power in an EFI car, you need the following:

1 EFI chassis
1 DFI chassis harness
1 DFI engine harness
1 DFI engine
1 DFI gearbox
And...while I'm pretty sure the fuel delivery system is the same EFI to DFI, once you get to the motor, the DFI car obviously runs the high pressure pump. So i'm not sure at which point you wouldn't be replacing the entire fuel tank low pressure delivery system. Maybe you wouldn't have to, as long as everything is the same from the tank to the engine harness.

If you want more power out of your Cayman, and you're 2006 to 2008, X51 engine swap or X51 with forced induction. If you want more power out of your Cayman and you're a DFI car, a 3.8 with some conversion work should pretty much stomp every other car into the dirt, given that it's capable of 460 hp and probably 320lb/ft. of torque at the crank with the bolt-on parts we make for our Grand-Am GS Cayman race cars.

That's my $.02.

Good luck.

John
BGB Motorsports

BGB Motorsports

P.S. That's reliable, nearly stock horsepower with bolt-on modifications of 450hp +++.

GTgears

The biggest problem with this kind of information is that Porsche makes it challenging to gather it in the first few years of production of a new product. Unless you go out and spend a ton of money on samples from dismantlers or new crate parts from Porsche, it's really hard to sort out all the different specs.

I'll make an example from our own history. Before I bought the company, Paul Guard got sent a sample differential from the 986 5spd gearbox from a customer so that he could make an LSD. So he makes the LSD, puts it on the shelf, and starts selling it. Well guess what? Porsche changed the sidecover and the bearing size on the 986 gearbox starting in 2000. He made a full production run of LSDs that will ONLY fit the 97-99 gearbox. Everytime someone wants a 5spd LSD for their 2000-04 gearbox we have to inform them that they'll need to source and purchase an early sidecover that gearbox to make it work. Since there were no service parts, and no PET diagrams available at the time, there just wasn't really any way to know that Porsche had made this change until the first LSD was sent out for a late gearbox and the installation ended up in the weeds. Not really the best situation to be in as a manufacturer.

With the 6spd gearbox, I have to confess that we just got plain lucky that our existing product fit and works in the DFI 6spd gearbox. When the Interseries cars were first being put together I was contacted and asked if they were the same. My response was that I didn't know but that I would be happy to either take a stock differential and measure it against ours, or send one off to see if it fits. Otherwise, 3 years ago, I would have gone out, found a sample gearbox from a wrecked car, and made a new 6spd LSD for the new gearbox. But because that wasn't required, I didn't know anything about this whole bolt pattern change thing until I started exploring this little side project.

Here's what I have been able to determine, in part based on assitance provided by John at BGB. All the 2005-2008 Cayman S gearboxes are the same. The '09+ 6spd for the Non-S model appears to be the same thing. The 2009+ DFI engined S gearbox is a different bolt pattern but I still don't know if there's any internal differences other than a revised mainshaft with slightly different 1st&2nd gear ratios. Otherwise, I suspect that once Porsche releases service parts for rebuilding the 6spd gearboxes, they will all be the same.

Lastly, I do want to share the motivation behind all of this since a couple people here are talking about the strength and durability of the 5spd gearbox. I have sourced a short ratio ring and pinion that fits into the 5spd from a cross compatible Getrag gearbox used in a different manufacturer's product line. I was interested in using this cheap car as a "proving ground" for what could be done with a 5spd car in one of the power to weight racing classes out there. While the intention was to drive this car on the street, I was also interested in taking it out to DE's and getting some times together that would help show folks that configured properly, a 5spd Cayman could be a competitive racecar. I'm trying to think forward to where these cars can go as the prices come down, and they become more cost effective to build into track toys.

Unfortunately, I missed the boat on this car and it sold while I was doing my homework. But it won't be the last cheap Cayman out there and this isn't the last you'll hear of short ratio ring and pinions for the 5spd. On Friday I purschased a factory reman'd 5spd gearbox and will be installing this new R/P set into it shortly along with one of our LSDs. I don't think it will take me very long to find someone interested in putting it into their car and serving as an example to others what you can do with a 5spd...

jmazz

That sounds like a great project and I am really happy to hear about it. The 5 speed hasn't seen much love. The information in this thread makes me want to find a pre-DFI 3.8 even more now. It sounds like if that ever happens for me I will be sending you my 5 speed for the same changes. Thanks for starting the topic.

jmazz

I thought of one more question on this topic. Clutches. What is interchangeable there? I thought I heard that the input shaft of a 5 speed is different than a 6 speed so you can't use an X51 clutch. Is that correct? Are flywheels interchangeable?