What can you tell me about the 74mm TB?

[stilov]

I am working on my 996 turbo.

I realize the 986 and 996t share the same throttle body, 68mm
part number 986 605 115 01

Then I saw a 74mm throttle body from a 2.7 boxster, but all my part references show the same number for all 986 boxsters.

So does the 74mm come on the 987?

If so, are they interchangeable?

Thanks!

[The Radium King]

my understanding is that 996, 997, and cayman/3.4 987 boxster tbs are all interchangeable and 74mm ID. tt runs a smaller tb because the air is compressed and you don't want to uncompress it by increasing the pipe/tb diameter.

[stilov]

interesting... it seems if you buy an IPD plenum they say you need to use the 74mm TB, but I'm wondering if the 74mm TB is a direct bolt on.

My 996 is running 1.55 bar on bigger turbos, so I'm not worried about de-compressing.

[Lapister]

Welcome, it's a popular mod discussed quite frequently here for rather cheap. About 20 or so hp by adding the 74mm TB+ 997 Distribution-T and 987 Air intake box. I'm about to embark on that mod myself.

[JFP in PA]

Originally Posted by Lapister

Welcome, it's a popular mod discussed quite frequently here for rather cheap. About 20 or so hp by adding the 74mm TB+ 997 Distribution-T and 987 Air intake box. I'm about to embark on that mod myself.

Is there dyno data available to support that?

[edc]

Originally Posted by JFP in PA

Is there dyno data available to support that?

I have dyno'd my last S before and after the 74mm throttle body, 996 plenum and larger MAF to tb intake. It gave a little over 5bhp.

[JFP in PA]

Originally Posted by edc

I have dyno'd my last S before and after the 74mm throttle body, 996 plenum and larger MAF to tb intake. It gave a little over 5bhp.

That is more inline with what I would expect.

[Topless]

Originally Posted by JFP in PA

That is more inline with what I would expect.

This is what I would expect as well. I don't see the stock intake, TB, and plenum as a significant restriction with stock displacement. Unless you add 3.4L the result will just be a narrowing of the torque curve. Maybe a few Dyno ponies above 6k rpm but overall slower lap times on a race track. Less than ideal results.

[stilov]

I realize that. I'm not working on a 986 so I'm trying to understand if the 74mm TV will work with my oem plenum.


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[stilov]

Seems that I have found my answer. The 74mm TB which is a 997 part number does not work on the 996 turbo oem plenum.

Sort of sad since the cost of the 986 part number is almost triple that of the 997.

As JFP said... Even in the highly modded 996t world I haven't seen convincing enough data to drop that much money into buying the nearly 1000 plenum to make it work on my car.

I make 700 to wheels with the small 68mm TB. I just figured if it was cheaper to get the 74mm is give it a shot since I have to replace the TB anyway.

Last question, in the 986 community, do you guys find TB failure common?





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[Gilles]

Originally Posted by stilov

I make 700 to wheels with the small 68mm TB.

Could you elaborate a bit more, Please..?

[itsnotanova]

Originally Posted by stilov

Last question, in the 986 community, do you guys find TB failure common?

I don't know much about 996T's, but you're the second person in a week contacting me about buying a 68tb to put on their 996T. The other guy made it sound like it's common to the 68TB in the 996T. Maybe the heat gets to them?

[stilov]

Originally Posted by itsnotanova

I don't know much about 996T's, but you're the second person in a week contacting me about buying a 68tb to put on their 996T. The other guy made it sound like it's common to the 68TB in the 996T. Maybe the heat gets to them?

Ha, I was the one that told the other guy about you!

I'm not sure the 996 guys suffer failures often, but they do. I'm not 100% positive that's my problem but its very similar to what happened last time.

The 996 turbo part number is the same as the 986 part number.

They are all the same. Sadly on the 996 turbo, the plenum is very different from any of the NA motors, so it's not as simple as buying the 997 plenum for 50 bucks!

Gotta buy the stupid IPD for 900. Even at big hp levels the plenum/TB combo is "said" to make 20 to 30 whp. And THAT is for guys pushing 700 to 900 hp.

I have a hard time thinking it would be anywhere near that for the NA folks, but like I said I don't know.

[KRAM36]

Originally Posted by stilov

Ha, I was the one that told the other guy about you!

I'm not sure the 996 guys suffer failures often, but they do. I'm not 100% positive that's my problem but its very similar to what happened last time.

The 996 turbo part number is the same as the 986 part number.

They are all the same. Sadly on the 996 turbo, the plenum is very different from any of the NA motors, so it's not as simple as buying the 997 plenum for 50 bucks!

Gotta buy the stupid IPD for 900. Even at big hp levels the plenum/TB combo is "said" to make 20 to 30 whp. And THAT is for guys pushing 700 to 900 hp.

I have a hard time thinking it would be anywhere near that for the NA folks, but like I said I don't know.

I don't know much about the turbo plenums, but what about this one?

07 08 09 Porsche 911 997 Turbo Air Intake Distributor Tube 99711021570 | eBay

Pretty sure that's for a 74mm tb isn't it?

[stilov]

Originally Posted by KRAM36

I don't know much about the turbo plenums, but what about this one?

07 08 09 Porsche 911 997 Turbo Air Intake Distributor Tube 99711021570 | eBay

Pretty sure that's for a 74mm tb isn't it?

Thanks, but here is the issue. This is the IPD 996t plenum I couldn't find the oem pic...but this is what the vacuum stuff needs to resemble.

[stilov]

On my 996 turbo not a boxster.


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[KRAM36]

I don't have a previous dyno number to compare my added hp from the mod Lapister listed, but it's way more then 5 hp. EDC didn't list the mod Lapister listed, it's 20 HP on my car at the least.

[edc]

If you add in exhaust system, remap then the total increase was 20-25bhp but the throttle body and plenum alone was just over 5bhp. All with before and after on dyno. The butt dyno always felt stronger to me too but the reality is it's not as much as you feel.

[KRAM36]

Originally Posted by edc

If you add in exhaust system, remap then the total increase was 20-25bhp but the throttle body and plenum alone was just over 5bhp. All with before and after on dyno. The butt dyno always felt stronger to me too but the reality is it's not as much as you feel.

He didn't just list a TB and plenum change he also listed the 987 air box. You changed to a larger MAF housing, even with a tune I believe that's a mistake. It's way more then 5 hp.

[edc]

Originally Posted by KRAM36

He didn't just list a TB and plenum change he also listed the 987 air box. You changed to a larger MAF housing, even with a tune I believe that's a mistake. It's way more then 5 hp.

I think you keep confusing my cars and listing things which I haven't done! I have had 2 Boxsters both modded, but both different. One is a 550 with the standard 987 airbox and the other an early S.

I did the most work and dyno runs with the S. Mods as in my sig and posted previously ie no MAF change or 987 airbox and it totalled 20-25bhp.

As I mentioned, the TB with intake in isolation gave about 5bhp.