maf and throttle body diameter

[The Radium King]

got a question:

on the 986S, the maf is 3" diameter, but the throttle body is 2-2/3" (68mm).

on the 996, the maf is 3-1/2" diameter, but the throttle body is 3" (76mm).

one would think that they would be the same size for max airflow; why have a smaller throttle body?

[The Radium King]

hey king, thanks a good question. i would think that the reducing diameters (airpox to maf to throttle body to intake runners) would serve to accelerate the air, so there must be some benefit to having faster moving air vs the work required to accelerate it; perhaps to do with intake tuning and low rpm power development?

[Johnny Danger]

King,

Any updates on the project ?

[The Radium King]

good point trk, you're a smart guy. to research further, i went to the ipd plenum page where a variety of dyno charts have been posted. if you go to the cayman page, they post dynos for an unmodified car, a car with an ipd plenum, and a car with an ipd plenum and larger throttle body. it's interesting to note the following:

- the larger throttle body does not make a difference over the plenum-only install until over 4900 rpm; presumably when the resonance tube and cams have switched over.
- both the plenum and the plenum with larger throttle body underperform stock up to 3500 rpm, by up to 10 hp less. i attribute this to the plenum. after that the ipd products do look to increase hp by 10 to 15 hp, and the overall area under the curve looks bigger with ipd.

conclusion? the larger throttle body doesn't have any ill effects, but the plenum causes a low rpm reduction in hp. in a cayman.

if you look at the ipd boxster products, they only offer a plenum with larger thottle body (74 mm thottle body, equal to the boxster maf diameter) and their dynos show hp improvement throughout the rpm range.

so, if there are no ill effects with a larger throttle body, why did porsche use throttle bodies smaller than their maf diamters?

[jaykay]

Interesting I was thinking of somehow mating the 74 TB to the stock intake "tee". Not sure this is feasible as I am guessing the tee has thin walls.....or replace the tee with a 997 tee with silicone reducer boots feeding the left and right plenums

So you are telling me I need a plenum!?!

Sounds like the 68 TB is there to provide a de-tune factor.

[The Radium King]

i was thinking 'de-tune' factor also, but why do it to the 996 (thier flagship at the time)?

anyway, the purpose of this thread was the same as you - some thought on getting a larger throttle body on my car. findings are as follows:

- there is benefit to doing this
- porsche makes two 3"-ish throttle bodies that match the 3" boxster maf diameter; a 74 mm (996, 987, cayman) and a 76 mm (996 gt3, cayenne)
- the 76 mm won't work; different plenum connection, more expensive.
- the 74 mm would work, but i am uncertain if the plenums would match exactly. even if they did, i am uncertain if you are not just moving the restriction further downstream as a result.
- so, you can use 996 plenum and two reducer boots (but would have to re-route the aos) or cayman (edit to add that i think the cayman plenum has a resonance flap that the 986 does not, as well as two aos connections instead of one); there should be lots of take-offs from guys who have put ipd units on their cars.
- note that you would also have to change the piping from maf housing to throttle body as it is currently sized for the smaller throttle body; you would need a 3" pipe/flex duct of some sort.

the next step in my thinking was having a go at the plenum. there is something inherently wrong in paying $900 for the ipd product; i was thinking of the following:

- get a cayman throttle body and plenum.
- saw the 'T' off the plenum, leaving only the flange and aos connection.
- get a silicone guy to fabricate a 'Y' with appropriate diameters.
- hose clamp it to your two intake runners and modified plenum.

[jaykay]

Hmm for the 996 the mass airflow sensor section diameter is probably common for cost savings ; parts interchangeability etc. I did not know that these sections were shared. The reduction in diameter here would bump up the velocity with minimal losses.....so very little hurt for major parts sharing cost savings......just a guess.

When you get to the throttle body 68mm with a butterfly valve stuck in there is a de tune vs. a 74mm. as long intake velocity does not fall off below optimal....just a guess

I looked into rapid proto typing an intake piece I am making....low volume costs
are huge...The IPD price is a bit easier to swallow after that but....

I have all this rolling around in my head too. Let me know how you make out!

[Johnny Danger]

I've been following this topic for a couple of years now; especially articles pertaining to the IPD plenum. Interestingly, most of the "tuners" that I spoke with initially (particularly the German ones) viewed this upgrade as a waste of time and money . Curiously, however, over time most them either began selling the IPD product, or developed a similar plenum of their own . Unfortunately, there doesn't seem to be enough supporting data regarding an M96 application to justify spending $1000 . I've heard a lot of "seat of the pants" and "butt dyno" endorsements. But no real evidence . It's up to you TRK to create a test bed ! If it's proof-positive, then a lot of us will buy one from you .

[j.fro]

Last year I picked up a 996 TB and the intake T from a Porsche dismantler. I had the intake T modded by Pedro with the Techno-Torque. The original 986 rubber connector hoses in the intake are flexible enough that I was able to reuse them. It works. I haven't dyno'ed yet, but the car pulls harder through the midrange and top end. You know the surge a stock 986S gets around 5K? I'm getting that at about 4K now...
I really need to dyno this thing

[AndyA6]

Maybe of interest??

TechnoPower Kit

TechnoPower2 Kit

With dynos (for the 3.2)..... looks good to me!

[AndyA6]

I love this forum!!! Can't wait to do this myself!

[The Radium King]

ok, here's the quote from suncoast:

997-110-416-03 DISTRIBUTOR T 1 42.43
900-385-025-04 HEXAGON-HEAD 4 0.27 1.08
997-110-319-00 RUBBER SEALIN 1 5.49 5.49
N-011-524-27 WASHER 4 0.15 0.60
999-512-539-01 HOSE CLAMP 2 3.05 6.10

thats for the new plenum, four shorter throttle body bolts and washers, a gasket for between the throttle body and plenum, and two larger hose clamps for the larger plenum outlets. total $55.70 + $100 throttle body = $155.70 so far. all i need now is ductwork to the throttle body ($20 spectre flex duct from ebay until i figure out the geometry of my pending cold air intake) plenum outlet reducers (i'll wait for the parts to come so that i can confirm required diameters) and some tubing for the aos (only if i can't reuse oem; if not, i think i'll go with transparent so that i can monitor just what the aos is venting into my intake).

i still think i'll get in for under $200.

[jaykay]

For your cold intake...

You should check out what Sparker, on here, did for his intake. Essentially he sealed a tube with an inline filter to the side scoop; cold air coming right in. I am sure there are others, tunners, that have done it as well. It was also in carbon fiber, but it looked great.

Perhaps if you insulated it, it could be what you are looking for. IPD seems to make all kinds of insulation blankets. I am also thinking the air would be moving so fast (straighter shot to the the TB) that there would be less "heat exposure" time in the engine bay. There is the problem of water injestion to consider though.

Next you need a little bit of a side scoop on the left side to get some free ram air pressure in there!

Originally Posted by The Radium King

ok, here's the quote from suncoast:

997-110-416-03 DISTRIBUTOR T 1 42.43
900-385-025-04 HEXAGON-HEAD 4 0.27 1.08
997-110-319-00 RUBBER SEALIN 1 5.49 5.49
N-011-524-27 WASHER 4 0.15 0.60
999-512-539-01 HOSE CLAMP 2 3.05 6.10

thats for the new plenum, four shorter throttle body bolts and washers, a gasket for between the throttle body and plenum, and two larger hose clamps for the larger plenum outlets. total $55.70 + $100 throttle body = $155.70 so far. all i need now is ductwork to the throttle body ($20 spectre flex duct from ebay until i figure out the geometry of my pending cold air intake) plenum outlet reducers (i'll wait for the parts to come so that i can confirm required diameters) and some tubing for the aos (only if i can't reuse oem; if not, i think i'll go with transparent so that i can monitor just what the aos is venting into my intake).

i still think i'll get in for under $200.

[onaFLYer]

This is great stuff, I was this <> close to pulling the trigger on the IPD plenum. Now I have a whole new direction for a fraction of the price.

Thanks for sharing this guys.

[Johnny Danger]

TRK,

Build one - build one - build one !

[The Radium King]

well, it'll look exactly like this (the image at the bottom of the page):

TechnoPower2 Kit

the technotorque in those pictures is a 997 plenum and throttle body. it fits, but requires the adaptors as shown in the first image (the plenum to intake runner connections) and last (the aos connection). he is able to reuse the oem intake pipe by adding the blue coupler as shown in the third image.

so, pedro's been here already (smart guy) but is trying to make money off it by adding the splitter; i don't think the splitter adds anything to the equation.

[jacabean]

i am very interested to see how this turns out. someone may be able to sell this as a kit.

[jacabean]

Pedros setup is nice but the cost is as much as the IPD set up. i guess your best bet is to put the parts together yourself.

[Johnny Danger]

Originally Posted by The Radium King

well, it'll look exactly like this (the image at the bottom of the page):

TechnoPower2 Kit

the technotorque in those pictures is a 997 plenum and throttle body. it fits, but requires the adaptors as shown in the first image (the plenum to intake runner connections) and last (the aos connection). he is able to reuse the oem intake pipe by adding the blue coupler as shown in the third image.

so, pedro's been here already (smart guy) but is trying to make money off it by adding the splitter; i don't think the splitter adds anything to the equation.

This must be a recent development, because a few months back I contacted Pedro regarding a larger plenum and intake for my 3.2 . And, at that point he had only developed one for the 2.7. .

[The Radium King]

hot off the presses ...

What's right with this picture?...