Intake plenum and 911 throttle body

[madmodz]

Eddy,
What are you doing for a air intake?

[eddy]

I picked up a 987 airbox. I'll be plumbing the 986 3" MAF onto it and using 3" piping to the TB. I don't want to have to sort out a re-tune to accommodate the larger MAF.

[madmodz]

As you guys know, Ben has a few of us beta testing the unit for fit, performance, strength etc.

I would suggest changing the end of the plenum from concave to straight like the 986 oem and adding the groove for the boot to fit on.





I thought my unit was not wide enough due to me having issues with the boot not providing a good seal. I measured it against the oem. The issue is the edge of the plenum. It slopes downward. My clamps right at where the unit starts sloping down. I can't get a good seal. I have the other side of the boot on the groove of the intake manifold. For me to get it to seal, I have to move the boot off the intake manifold groove and closer to the plenum.

Since I have to order the silicone, a solution would be to replace the boots with two of these which would give the seal I need plus look cool

[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

[dijinn]

Originally Posted by Ben006

Nope, the 83mm doesn't bolt for now.

I don't think it would be suited for the boxster' small engines.

I can do one for the GT3 TB if someone wants to try it!

The last one is on his way to the other side of the ocean

Ben

I'll give the GT3 TB a shot if you're up for it Ben!

- J.

[madmodz]

Originally Posted by dijinn

I'll give the GT3 TB a shot if you're up for it Ben!

- J.

I 2nd the 83mm. I know its big, but I think it has serious potential especially with a tune.

One thing I must add, I siliconed the tb to the plenum before the install thinking it would be easier. Don't do that. The added weight of the tb makes it hard to maneuver the plenum when installing the boots. Both the intake and the plenum got plenty of clamping areas so I might go with the silicone boot instead of the oem.

[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.

[Ben006]

Originally Posted by madmodz

I 2nd the 83mm. I know its big, but I think it has serious potential especially with a tune.

One thing I must add, I siliconed the tb to the plenum before the install thinking it would be easier. Don't do that. The added weight of the tb makes it hard to maneuver the plenum when installing the boots. Both the intake and the plenum got plenty of clamping areas so I might go with the silicone boot instead of the oem.

If you already have them, or if they are really cheap, why not

The GT3 on the 3.2L at least, I don't think the 2.7L has much more to offer :/

Well, I know what I'm going to do during the hurricane!

[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!