Intake plenum and 911 throttle body

[eddy]

Originally Posted by Ben006

The slant was to make fitment easier, the OD of the plenum is bigger than the OEM.

You should not need new boots, The clamp should fit just after the chamfer:


The boots won't go as far on the side manifolds as before, but sealing is still good. The grooves are more for locating.

Best way to get it easily on it to first put both boots as far in as possible on the plenum, slide the plenum in between the manifolds, then slide the boots back in their final position.

Don't tighten the outer clamps before you get the new intake tube in, it won't be as flexible as the original one!

Now that I've said that... You're probably right, using this method, the chamfer doesn't need to be that wide! I can probably make it narrower, that will give more surface to seal.

I've put the chamfer when I was using a different method to put the plenum in: Both boots on the sides, slide the plenum in, then slide the boots over the plenum.

Thank you for you're feed back, continue to share your thoughts! This is exactly what I need to know!

Ben

Thanks for this! I am probably going to install the plenum tomorrow. These instructions will help.

[eddy]

hey Ben, any particular liquid gasket you think will work best for tb/plenum mating? i think you sent that to me in pm but i might've gotten rid of it.

[Ben006]

Any RTV sealant should do

I've used blue one.

You really don't have to put much, a 1mm thick bead will seal more than enough!

Put the silicon along the small groove (it's a guideline, and prevent too much silicon from being crushed out), the bolt the TB to the plenum and clean the silicon that will have been pushed out (you can open the throttle plate by hand /!\ but unplug the TB first! /!\)

[eddy]

merci beaucoup!

[eddy]

ok, I got started on this today. some quick notes:

I removed the factory plenum using the reverse of Ben's install notes above. came right out.

I observed that the AOS hole in the Ben Plenum (Benum? Blenum?) was significantly smaller than factory. The photo isn't perfect-- the inside diameter of Ben's is nearly the same as the inside diameter of stock, but then it pinches into a tiny hole. I decided to open it up a bit because I wanted to keep it as close to factory as possible.

https://goo.gl/photos/Da1CYW83ZDKmMG8J8

https://goo.gl/photos/idyMc4ePW76Yb6Mt5

https://goo.gl/photos/MpXdu4YKevBP6PUq5

https://goo.gl/photos/N8Tthfft5pYTWAkw8
After sanding it smooth and cleaning it up I test fit it. A little side to side adjusting and it lined up well. I'm confident that the bands are tightened down on enough plastic and nothing is going anywhere.

https://goo.gl/photos/WEZxo1DtjyHpPiBCA

Going to pull it out because I have to do the 987 airbox and it might be good to have it out of the way. Also going to do the AOS while I am in here. Will make a little progress in the next two days but it'll be next week before it all comes together.

sorry about the links; having trouble posting pics.

[heymanwatchthis]

Eddy,

I would be interested in hearing your impressions on the 987 airbox install. I have done a lot of reading and understand how to mount the MAF, however am curious about what it takes to get the 987 airbox in and connected.

Thanks and good luck.

Gary

[eddy]

Sure thing, Gary. I will probably do a separate thread about the whole install in addition to offering feedback in this one about the plenum itself.

[jb92563]

This is a great development by Ben with everyone's input suggestions.
More heads on a design can be better than one and the results will likely prove that out.

I am trying to get up to speed on this and figure out how to get the most out of this on my 01 S.
Also be great to summarize where we are with this design and testing results/impressions.

Q1) What is the primary objective of this part?

From what I have read the goal is to improve the aerodynamic flow of air into the engine, over the stock part, which should result in a greater Volume of air available for combustion, smoother airflow, quicker throttle response etc.

Q2) Has anyone calculated the current volume of air over an rpm range of the stock part as a baseline and compared it to the New design?

I think you could probably use the MAF readings on a Durametric to easily read those values.
Retaking those MAF/rpm readings with the new plenum will immediately tell whether an improvement has occurred with the new design.
This would be super easy to accomplish.

You should also be able to calculate air velocities to determine what you would need to do to make the greatest improvements. The Y shape should be better than a T if the diameters/volumes are consistent. Any change will increase or decrease airflow speed which will result in less than optimum results.

Q3) With the new improved air volume numbers one could calculate the amount of fuel required to make use of the extra air available and perhaps using the O2 sensors readings determine if the existing mappings are able to supply enough fuel to use all the available airflow. Again more calculations or observations of the sensors?

Once this is determined then you might get an idea whether an ECM remapping would be beneficial.

Q4) What are the current diameters of the plenum. What TB's will fit?
From reading Im seeing 76mm 997 TB and 83mm GT3 TB with 73mm being stock size for the 2.7L engine?

Q5) If you are fitting a bigger TB like 83mm wouldn't you want to increase diameters upstream including the airbox. Can GT3 parts for the upstream components be used or would it be custom?

What comes in must also be able to exit even faster so opening up the exhaust flow might also be part of the optimum tune.
In the case of cars with 4 cats removing the secondary cat has opened up the exhaust flow rate to help in that regard and the car can still pass emissions.

It would be nice to list the combinations tried so far and what the results were so we all don't have to go through the learning curve, and can get optimum results right away based on the amount of work we are willing to do, ie Just the Plenum vs Plenum & TB vs Plenum, TB and exhaust etc.

Perhaps you can edit Thread #1 to include all the latest info and results.

Kudo's on undertaking and documenting a cool sort-of open source development of a 986 part.

Looking forward to seeing the results posted.

[Ben006]

Very nice eddy!

I made the hole smaller as to disturb the airflow in the plenum less. The AOS is what controls the airflow through that it, and the size of the hole is large enough to vent the crankcase

To fit the airbox you will have to remove the left side manifold so yes, you're going to remove it

JB:
-Q1: Yes the main goal is to decrease the charge loss, resulting in greater airflow and thus greater power. I haven't really noticed a change in response though.

-Q2: Yes Few pages back I talk about it.
I did a few test runs, and I've measured an average of 8% more airflow. Unfortunately, I could only compare maximum value, so I don't know exactly at what RPM it happened (probably near maximum power rpm).

I can't do a Y shape, it's patented, and I don't do that to get troubles

Q3: The stock ECU is able to make it run, no worries on that. But a remap would get the most out of it.

Q4: The stock TB for 2.7 and 3.2 engine is 68mm. The 911/987 TB is 74mm, and the GT3 is 83mm.
For now, I only make it for the 911 TB, because I believe it is the more suited for the application, and also cheaper and easier to find.
I will make one the BIG 83mm TB later, and also one for the 996 cars to fit the GT3 TB.

Q5: I talk about it a few pages back too. The plenum and TB should NOT be your only mod/first mod!
That is why I've ask the tester to have at least an exhaust.

My configuration right now is soft, I run eBay headers and midpipes, and the plenum...
I'm going to fit a k&n filter soon.

a 987 airbox will be a good addition, that's why eddy and mavis.d are doing it

I can't guarantee that the car will pass emissions unfortunately!

I'll try to do a summary of everything on the first post

I might have found an easier solution for the AOS to plenum connection, might even be cheaper than the current one!

Thanks guys for everything! Continue to give your opinions!

Ben.

[eddy]

As I was boring out the hole I thought that you probably made it the size you did for a reason When I make my thread for this whole install I will note that you sized it that way on purpose and what I did isn't necessary.

I would expect that this isn't going to change emissions at all, although I understand that you can't guarantee that!

JB-- good questions, all. I look forward to sharing my dyno numbers for this + 987 airbox as a reference point for intake mods here.

[jb92563]

In thinking about/visualizing the airflow, I had a thought and some more questions and ideas.

What is the orientation of the TB? does the throttle plate pivot about the vertical axis (like a door) or Horizontal like oven.

I'm 99% sure the plate must be oriented so that it pivots about the horizontal axis since the other option would be a serious problem for even distribution of airflow to the left and right intakes.

With the scenario of a partially closed throttle plate I am thinking that the airflow would benefit from an small induced spin to reduce the impact of stagnant air pockets that are not moving and would disrupt the smooth flow of air and cause turbulence. That means that the flow divider should also have a complementary twist to neatly divide the flow without blocking the imparted spin.

You could design some small short fins that stick out behind the TB to impart a gentle mild spin.

Of course that sort of minute detail might be hard to test because many iterations will be needed to determine the optimum fin angle/length and resulting improvements in performance.

But sometimes those kinds of innovations cause break-through's that along with a patent is what makes inventors stupidly rich.

We need a flow modeling App to try this out and speed the development.

[Ben006]

Without CFD or 10 different iteration each dyno tested, there is no way to make a real improvement.

The plenum has the shape of the stock one, with larger radiuses on the T. That is the only part that is 100% proven beneficial.

[eddy]

This has the potential to be a very cost-effective upgrade. Ben's put a lot of time in and I'm excited to see what the gains are as-is, and if he wants to incrementally improve from there I am all for it. This is a great example of someone in the community filling a void!

[heymanwatchthis]

I wonder how much impact this mod (plenum + 74mm TB) has using stock 986 airbox vs the 987 airbox?

[Gelbster]

Originally Posted by heymanwatchthis

I wonder how much impact this mod (plenum + 74mm TB) has using stock 986 airbox vs the 987 airbox?

This is a good question because clearly the 987 air box is a huge pain and will deter some potential customers.

[eddy]

Originally Posted by Gelbster

This is a good question because clearly the 987 air box is a huge pain and will deter some potential customers.

I agree. I thought about doing some testing with the 986 but ultimately decided that I wanted to just jump to the 987 box. I thought about other intakes but liked the fact that the 987 box is not open to the engine bay.

I'm sure it can be done more cleanly, but I had to bend the edge of the access area. I also elected to not cut the part of the body that buts up to where the box makes its turn, meaning that fitment isn't perfect. Just a bunch of little headaches that I'm fine with but wouldn't encourage others to dive into.

Progress update: box is in, plenum is in. Decided to get a silicone reducer to facilitate the MAF setup, so I've gotta wait till that comes in and then plumb the route to the TB.

[eddy]

Got the 987 box in. A little under 2 hours to get the 986 airbox out, probably 3 to get the 987 in-- fitting, then cutting, then re-fitting, then wishing that Porsche made bigger engine access panels, etc.

Cliff's notes:
trim as much as you can off the 987 box because it's a super tight fit.

I had to loosen the left manifold.

Lowering the engine saved a lot of aggravation.

---
figuring out how to mate the 986 MAF to the 987 box. Thinking that I am going to use a silicone pipe reducer where the 987 MAF clips to the box. Apart from the vacuum line i broke, that should be the last part i need to get this done.

[Ben006]

The problem with airboxes... is that, basically, the bigger the better! But also the more pain it is to fit...

I'm going to test a K&N panel filter tomorrow, and see if that makes a difference in the stock 986 airbox.

I believe the 987 airbox is a good mod to go along with the plenum, but not 100% necessary, I don't have one (but I have the headers and mid pipes).

I might give the 987 airbox a try if I'm not satisfied with the K&N. And maybe design something to make the modification of the box and the fitting easier!

I will contact a Porsche tuner soon that distribute GIAC tunes and have a dyno, see if we can work something out ! It won't be cheap though... We'll see, I'll keep you in touch!

Ben.

[Ben006]

Eddy!! We need pictures!!

I put the K&N in today too.
Just like the plenum, the first minutes felt weird, less sound, less power, but a very smooth power delivery.

When I got home (I installed it during lunch break...), it felt nicer, but still quieter than before!
We'll see how it does in a few days!

I took the time to inspect the plenum quickly, looks good after 6 months or so ? (I don't remember when I put it on ?).
I found a place where I can put a bit of reinforcement too. Don't worry testers, yours are totally fine! But if I can make it a bit better, I will

Ben

[eddy]

pics coming soon i promise!