Short of it. After doing some research of a few threads regarding the newer 997 and GT2 expansion tanks (I'll likely use the word intake interchangeably with expansion tank so don't get your panties in a wad) I wanted to give this a whirl and do a DIY on it.

I'm not sure what questions will be asked, feel free to post them up, I'll edit this first post for information rather than replying.

I"m starting out with the Engine out, on the ground, I'm not even going to try this project 'in the car'.

First picture is everything off. This was pretty simple, mostly just removing parts until I had full access to this.


This next photo is of both tanks:


Just the lower flange and 997 tank:



Here is it mocked up: Note the right EGR port is uncovered. **Edit for accuracy***
3/8" -18 npt pipe plug works. Just need to plug the hole with a paper towel, tap the hole as deep as you can. Vacuum the shavings out and run the vacuum as you pull the paper towel out. Blowing air through the other egr hole will also purge any thing that may fall through.

This is all the stock flange does. On the left side, I've not decided how to bolt up the EGR pipe. Right now, I'm likely to build an adapter plate to use two of the inboard head bolt holes to bolt it down and then simply bolt it together. Other options would be to weld this adapter to the 997 tank and machine it all flat again. Suggestions of those who have done it?
Has anyone simply deleted the EGR on these cars? I'd imagine tricking the computer is as simple as a resistor of the correct value.



And the test fitment:
Fuel rail lines up. I'll have to slot this rail or use the slotted one on my current engine when I bolt everything together (or fabricate a bracket) with my 60# injectors. But everything lines up, the only 'issue' I have so far is the EGR line and some mounting brackets for hardware. *Will edit which ones later*



Larger photos are here if you want to see more detail:
http://bedellracing.smugmug.com/Othe...84367213_sdMHg

 

Right side:

Starting out, I wanted to take as little as possible off. I had to loosen the oil tank, remove the vacuum pump and oil fill tube, but other than that it was pretty easy.


This is the only 'clearance' issue. I suspect a crescent wrench on the bracket and bend it toward the front of the engine will be enough after you trim the water hose about 1" shorter. **I'll edit once I accomplish this.



The valve will be a bit more difficult on this side. I'm not sure what I will do, although it will likely look considerably like the 997 stock piece (see below)



How do the ports match up? See for yourself. Had I actually bolted these in, they would have been perfect. Note, this is the 996 part. The biggest benefit would be to actually go into the head and reduce the sharp 'ramp' from where Porsche did the port matching themselves.




Lets dispel a myth. The ports are identical on the 997 GT2 at the head. I'm not sure what they look like once into the head. However, on my parts I could get the ports to match up identically except where the injector clearance is.




This is the stock 997 setup:

 

I'll use this one for the 'fixes' I have done. On the left side, I threaded the front hole.

Simple solution. No drilling. I packed a piece of wet paper towel into the hole. Tapped it, vacuumed the hole out. Continued to run the vacuum as I was pulling the paper towel out. Then, I blew air into the other egr hole to evacuate any bits that may have fallen through.

3/8" x 18npt tap.


Really quite simple.


All plugged. This plug is tapered, so no sealant is needed. However, it is a good idea to put some anti-seize on it. I did, but not in this photo.

 

Photos of the 997 GT2 (aluminum) and 997 TT splitter or 'plenum' Physical measurements are roughly 2.5" on the GT2 and 3.5" on the TT, throttle body inlet is the same. This is a 77mm hole. Uses the 75mm(ish) throttle body.

 

I had my motor apart when I did this mod.. I used the 997tt not the 997gt2 unit.... I tapped the "erg" holes and ran plugs in them in the exhaust ports as to stop the hot exhaust gas from running into the head and making things hotter! There was carbon build up in the head so the exhaust is going though those port and tubes, not good IMO! Those holes are not in the 997tt head nor cup heads. Remember the holy grail of turboing a motor is 1 to 1 (1psi boost to 1 psi in header pre turbine) so there is quite some pressure behind that little hole under boost.. I used the 997tt runners because it is plastic and fits the 996tt port exactly... At that time the men in the know assured me that the 997GT2 had smaller runners and that motor was using a different port geometry so I played it safe. Can you let us know if the runners match the stock 996tt head? Good luck on your build, Tim

 

Brad, Your wye pipe will need to be shortened up some Tim

 

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Here's mine, prior to installation. I got adapters done from billet for both ends of EGR piping and brackets for aux items, ie. secondary air pump and that turbo intake thingy. I also made a new "plenum" ( = that T-piece connecting TB to intakes ) so thet GT2's expansion manifold principle doesn't get disturbed.
Runners are slightly ported to match turbo's heads, I also ported exhaust manifolds too.

No, I haven't dynoed it yet. I haven't even driven the car yet, but the engine works without CEL's. There's a lot things to do with turbo engine to C2 chassis conversion, but I hope to get it on the road before first snow falls.

 

Pete pics aren't showing

 

OK, I have to upload them to 6speed too, linkie not workie...takes a while...

 

BTW Brad thanks for this as i have discussed this with a few people and there is plenty of misinformation out there

 

Pics in my original post.

 

Right, which is why I'll post up my findings regardless how they turn out.
My hunch is that the GT2 tanks will make for a better 'street' car and the 997TT would make for better high end/ultimate power car. Since I'm planning to stick with nothing larger than a GT28 turbo, I'd like to concentrate on getting power under the curve flatter.

The Irony is that this velocity/vs volume keeps being 'learned' by automotive manufacturers. My first lesson was about 20 years ago when building a 351c. To make a 4v head flow better, restriction plates are placed in the heads. Seeing this done, I went with the 2v heads instead of the 4v heads and picked up nearly a second in the 1/4 mile. With the latest generation of Porsche engines, it appears they are moving toward the higher velocity theory. (go figure?)

I do think I'll bring the adapter bit to market for the EGR/air injection system; although I doubt I'd sell enough to justify the initial batch. This appears to be the 'biggest' hurdle so far. *IF* anyone has a pair of 997TT expansion tanks, I'd like to set them side by side to the GT2 (or close up pictures?)


Tim: What is a wye pipe? I assume y-pipe? I'm planning on updating that anyhow. The plenum is smaller for the GT2, I have one, but will make my own also.
Good points on the EGR. If I tap in a freeze plug, I'm sure it will hold, but a 3/8" pipe plug or custom 14mm(?) threaded plug would be better. I'll do it this way.

Pete: I'll PM you an email. Thanks in advance for any help!

 

^ I'd buy an adapter! Great to see you doing this Brad (and Pete).

 

Ill get one from ya too!

Call up Alex @ MAXRPM in Bremerton, WA. He did the 997 swap on Jags car and knows a lot about what is needed and has some great tips. I plan on doing this mod next time my motor is dropped.