How can a 911 3.4 have so much more HP than a 3.2 Boxster S?

[heliguy]

I would love for Pedro to post Dyno results.

[Bigsmoothlee]

A smaller intake manifold, a smaller exhaust system, and the factory tuning limit the power in the 3.2.

I dont think the 996 intake manifold bolts onto the 3.2 head, I had to drill my 3.4 heads to accept a Boxster intake manifold ( I didnt want to lower my engine 1.5" )

Once my 3.4 swap was complete with a boxster intake manifold and exhaust system, I was very disappointed with the power. Replacing the entire exhaust system with a full NHP exhaust really unlocked some power...I was only expecting a 5-7hp increase, but it felt closer to 20. Im sure the 996 intake manifold will give another solid increase in power...

So I agree, the restrictions of the 3.2 are the complete intake and exhaust systems.

[BYprodriver]

Originally Posted by Bigsmoothlee

I dont think the 996 intake manifold bolts onto the 3.2 head, I had to drill my 3.4 heads to accept a Boxster intake manifold ( I didnt want to lower my engine 1.5" )

So I agree, the restrictions of the 3.2 are the complete intake and exhaust systems.

As JR posted the head castings are the same, & all bolt bosses are there. You just have to drill & tap the holes for the intake & exhaust parts you are using.




986 3.2 head has untapped bolt bosses to mount heat shields in 996s

[The Radium King]

this has got me thinking about a 996 3.4 intake manifold on the 3.2 with perhaps a cayman engine cover for the additional clearance required (or lower the engine) - I wonder if it has been done?

[JAAY]

Yes a 987 engine cover fits. I have one on my 3.4 conversion so I didn't have to lower the engine.

[The Radium King]

that would be the ultimate intake conversion then ...

987 air box - $250 used
987 engine cover - $100 used
996 3.4 intake manifold - $250 used
997 plenum - $50 new (you could use the 996 plenum, but one assumes the 997 part is an improvement)
996/997/987 throttle body - $100 used
987 maf housing - $100 jobber

$850.

get a softronic tune that let's you use a 987 maf housing - $700 on sale (or $50 labour at your local indy if a 996 3.4 x51 row pre-variocam+ tune will work).

finally, a $500 performance exhaust (topspeed or 987 S take-off) and a $200 underdrive pulley.

so, potentially 300 hp bolt-on (+50) for $1,600 to $2,250 - worth it?

[jaykay]

Originally Posted by The Radium King

that would be the ultimate intake conversion then ...

987 air box - $250 used
987 engine cover - $100 used
996 3.4 intake manifold - $250 used
997 plenum - $50 new (you could use the 996 plenum, but one assumes the 997 part is an improvement)
996/997/987 throttle body - $100 used
987 maf housing - $100 jobber

$850.

get a softronic tune that let's you use a 987 maf housing - $700 on sale (or $50 labour at your local indy if a 996 3.4 x51 row pre-variocam+ tune will work).

finally, a $500 performance exhaust (topspeed or 987 S take-off) and a $200 underdrive pulley.

so, potentially 300 hp bolt-on (+50) for $1,600 to $2,250 - worth it?

I tried to get softronic to give me a cayman MAF housing tune to no avail.

[Bigsmoothlee]

Originally Posted by JAAY

Yes a 987 engine cover fits. I have one on my 3.4 conversion so I didn't have to lower the engine.

Jaay, did you have trouble with the shifter cables being too short when you installed the 3.4 manifold without lowering the engine?

Which 987 engine cover did you use? Was it from a Cayman/Boxster S?

[golonaus]

Originally Posted by Bigsmoothlee

Jaay, did you have trouble with the shifter cables being too short when you installed the 3.4 manifold without lowering the engine?

Which 987 engine cover did you use? Was it from a Cayman/Boxster S?

dont know about Jaay,but In my install yes cables are too short
just a bit tho
Simple solution is to move shifter console about 1/2"
I drilled new mounting holes and shifter boot covered it
looks and works as it should
I'm curious how Jaay solved it too, tho
btw
I'm using cover from a cayman s

[golonaus]

Originally Posted by JAAY

Yes a 987 engine cover fits. I have one on my 3.4 conversion so I didn't have to lower the engine.

same here
987 cover got nice bump in the middle. you just need to trim off some of the carpet padding

[jaykay]

Originally Posted by JAAY

Yes a 987 engine cover fits. I have one on my 3.4 conversion so I didn't have to lower the engine.

Jaay does the cayman cover mess with the soft top? Were you able to adapt ithe insulation cover to fit over it ?

[golonaus]

Originally Posted by jaykay

Jaay does the cayman cover mess with the soft top? Were you able to adapt ithe insulation cover to fit over it ?

no problem there
5 min job to remove excess sponge/isolation

[BYprodriver]

Originally Posted by The Radium King

this has got me thinking about a 996 3.4 intake manifold on the 3.2 with perhaps a cayman engine cover for the additional clearance required (or lower the engine) - I wonder if it has been done?

I doubt any of this is worth the loss of low RPM torque especially for 3.2L or less.

My 3.6L does fine with the original intake & 997 plenum T

[The Radium King]

would there be a loss? the taller stacks on the 3.4 manifold should improve intake tuning at lower rpm? but I guess intake tuning for a 3.4, not a 3.2 ...

[steved0x]

This is a very interesting discussion and I just found the other big thread by TRK on using the bigger TB and Plenum. Very interesting stuff.

Steve

[Bigsmoothlee]

Originally Posted by BYprodriver

As JR posted the head castings are the same, & all bolt bosses are there. You just have to drill & tap the holes for the intake & exhaust parts you are using.




986 3.2 head has untapped bolt bosses to mount heat shields in 996s

Yes, I am aware of that. That's exactly what I did, but you make it seem ALOT simpler than it actually is. Being that both of my engines were out, I made a template for the 2.7 manifold and outlined the holes on the 3.4 head. I then removed the heads, and drilled the mounting bosses on a drill press since I wanted them 100% accurate and straight. I set up levels, used a lot of shims under the head, and then clamped it down to the machine to make sure the drill bit was exactly 90 deg to the hole I was tapping. Since it was a used engine, I didnt mind changing the valve seals and lapping the valves anyway.

I dont know if I'd have the nads to just take a home depot drill into my engine bay and try to drill the holes for the 996 manifold, but im sure it can be done.

[BYprodriver]

If you put 3.4 heads on a 2.7 you lost compression ratio & undoubtedly low rpm torque due to the bigger valves.

[Jake Raby]

Originally Posted by BYprodriver

If you put 3.4 heads on a 2.7 you lost compression ratio & undoubtedly low rpm torque due to the bigger valves.

Hmmn, what head gasket was used? With the difference in bore size at a whopping 10.5mm of bore size difference I'd expect issues. What cams were used with this?

I think he is stating that he had a 2.7 and did a 3.4 engine conversion...

[BYprodriver]

Originally Posted by Jake Raby

Hmmn, what head gasket was used? With the difference in bore size at a whopping 10.5mm of bore size difference I'd expect issues. What cams were used with this?

I think he is stating that he had a 2.7 and did a 3.4 engine conversion...

I bet you are right Jake, he did say he had 2 engines side by side in his post. Happy Veterans Day Jake & thank you for your service, both abroad & on Raby hill !

[Bigsmoothlee]

Originally Posted by Jake Raby

Hmmn, what head gasket was used? With the difference in bore size at a whopping 10.5mm of bore size difference I'd expect issues. What cams were used with this?

I think he is stating that he had a 2.7 and did a 3.4 engine conversion...

Yes, that is correct. I did a full 3.4l conversion, but drilled the mounting bosses in the 3.4 head to attach a 2.7 intake manifold to it. This allowed me to avoid lowering the drivetrain. I drive my car to work every day and the roads here in the Northern NJ/NYC area are atrocious, so lowering the engine 1.5" to accommodate the 3.4 manifold was a risky proposition. One raised manhole cover and bye bye engine!

I want to install the 3.4 manifold with a 987 raised engine cover, do all of them work or is it only the "S"model that has the raised portion for the intake manifold?