I have been toying around with this idea in my head for a bit, and now I'm starting to pull the trigger and put the pieces together. I won't make this a thread about water-methanol injection itself, nor get mired down in the pros and cons. IMHO, the water/meth pros far outweigh the cons. Yes, it's a bit of a hassle to get set up correctly. But those who run it successfully with the right kit and setup benefit greatly. Especially with a higher mileage turbocharged direct injection engine, I want to not only add power but increase longevity. The water/meth will aid in carbon buildup on the intake manifold. I'm also currently figuring out a good catch-can arrangement in addition. Anyway, back to the throttle body...

In reading, for example, Rennman's many upgrades he did on his slick 957 build, there's a discussion about the "E81 Powerkit" that was offered from the factory by Porsche for those certain years. Pretty sure they dropped that with the 958.1+, but since that 957 has basically the same engine as the 958.1, I wonder if there's any benefit to be had from some bits and pieces of that E81 kit. For example, the throttle body and the y-pipe (plenum).Retrofit/Conversion: Cayenne Turbo to Cayenne Turbo S - E81 PowerKit [PICS]- (I think it's been so many years that some of the pics/links are no longer accessible or available )

Throttle Body: in that thread, you can read about the factory Cayenne Turbo throttle body measuring "just over 78mm" (no photo available) whereas the throttle body from the E81 kit measures "just over 84mm". I plan to test some of this. I ordered a brand new Bosch OEM throttle body from Rockauto. I will measure it first, and then send it out for a porting service. I am going to request from the machine shop (or whoever) to specifically port it to 84mm, or as close as possible. The services performed on it will include the following and look something like this:

• Knife-edge of the front lip
• Port in a velocity stack
• Removal of casting marks
• Port and taper of factory steps before the butterfly
• Increase the diameter of the TB before and after the throttle blade
• 

Y-Pipe Plenum: I am trying to figure out a solution that doesn't bottleneck this whole package idea I have. The factory y-pipe plenum has got to go, I know that. However, does one need to drop $800 on the overpriced IPD Plenum? If so, which version do you get? If you read Rennman's thread linked above, there's mention of one version of the IPD plenum available for the Cayenne Turbo and a different one for the Cayenne Turbo S. I could be wrong, they could be wrong, who knows. It's been many years since these words were uttered (or typed on a keyboard in cyberspace lol). OR, one could purchase the Y-pipe of that E81 kit from that thread. I believe the part number is: 955.110.046.60. The only question is whether this part from Porsche is larger in diameter than the stock one. I would imagine so if it's part of the E81 "power kit" that includes the larger diameter throttle body (and intake manifold if I'm not mistaken). I guess there's no way to know unless side-by-side measurements are conducted. That's a goal here.

IPD: if there's a way I can avoid the crazy prices of the IPD metal plenum, I'd prefer that. Originally, I was considering it solely for the purpose of being able to drill and tap somewhere for an NPT nozzle for the water/meth injection plans. Even though metal vs plastic is more susceptible to heat soak. I just checked IPD's website actually and found there are different part numbers for their identical plenum offered for the 957 Turbo and the 958 Turbo... Curious. I wonder what the differences are. It's worth noting the product page for the 958 plenum shows dyno graphs from an 08 (so, 957) lol.
957 Cayenne Turbo 4.8L IPD Plenum ('07-'10) | Part #57276
958 Cayenne Turbo 4.8L IPD Plenum ('11-'18) | Part #58276

Throttle Body Spacer: Enter my new idea, half-concocted last night. After much thought, I realized it's going to be nearly impossible to find a good pre-throttle body placement for any water meth injection nozzle because of where the MAF sensor is located. With the MAF so close to the throttle body, it's great for tuning and for the ECU to get air measurements correctly. But you can't spray water meth on it lol. So... I started thinking about solutions to the TB.
Of course, why not a throttle body spacer! Not only a spacer, but one with an NPT nozzle already ready to go for water meth! Or at least one that could be likewise drilled and tapped!


.

Trouble is either finding an existing TB spacer out there somewhere that would be compatible with our throttle body and intake manifold, or frankly creating one. Luckily, I live near HanksvilleHotRods who make fun stuff for the Cayenne like test pipes, intakes, and all that jazz. I wonder if they'd be interested in anything like this since they are a metal fabrication shop.

So, I've been scouring the interwebs for throttle body spacer solutions. There are a ton of options out there, obviously, for all types of engines and platforms that people like to tune. Although none are specifically listed as compatible with the Cayenne Turbo V8, I don't think it's so complicated of a design that I couldn't figure something out. I don't know what the dimensions/sizes are of the backside of the throttle body and the front of the intake manifold. I mean, I don't know the lengths/widths of where the bolts/holes are and the distance between them. You can find spacers of all kinds of different diameters. If I am successful in the 84mm throttle body porting service, I'll look for an 84mm spacer obviously. I don't want any discrepancy or disruption of airflow between the TB and intake manifold. Especially don't want any leaks. Extra especially if the plan is to run water meth.

The trouble is unless I buy a bunch of random 84mm throttle body spacers and measure or test-fit them one by one, I'll never know if they'll work. I'm thinking the best-case scenario is I find one where the mounting bolts/holes match up perfectly with our configuration. Even if that spacer isn't 84mm, if it's less than that but has room to be opened up to 84mm, that would be great. I have been looking at other V8 throttle body spacers out there from the Coyote V8 (Ford) to the famous LS1 from GM... I don't WANT to buy 10 different spacers to find one that works, but I don't know of any other way. None of the spacers I see online tell you exactly all of the dimensions. But they wouldn't need to as 99% of people buying one only care that it's listed to specifically fit their vehicle. Those of us who live life on the weird side and like to do things our own way have to figure this out manually lol.

And to further complicate matters, I don't know how I feel about the spacers out there with fancy helical cuts or something to aid in the airflow. Not that I'm against the design (hell, look inside the IPD plenum for example, it's not smooth/flat)... I just don't know how well any of these spacers would take a drill/tap for an NPT nozzle for water meth...
.

Any help or input is greatly appreciated! Or you can live vicariously through me as I attempt this mod.

Almost forgot... In trying to think of everything and plan accordingly... Using a throttle body spacer obviously would ultimately kick out the whole throttle body and y-pipe plenum setup by however much, 1 inch or less. But that introduces a new problem in the fitment of the intake hoses. My workaround idea at this time would be to go with 30-degree silicone hoses maybe to account for the discrepancy. That may be too much of an angle/bend though. And I don't know of any degree bends offered less than 30?


.

Without mocking it all up, I won't exactly know what to do. But here's my rough-hand drawing interpretation of the end goal idea. This is clearly not to scale. And it's a childish skill-level drawing and I don't even think it came out on paper the way I envision it in my head lol. The point I'm trying to make is that everything will be pushed forward just a bit... and I need to rest assured that the intake hoses are securely fastened so there are no boost leaks...

 

Amazing project! Keep us updated

 

+1 agree. Subscribed.