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

I just went to lunch with a fellow Porsche owner in my town and he has a sweet Red 1999 996 base model, not S. It has a 3.4L and I just looked it up and it has 296 HP. My 2000 Boxster S with 3.2L has ~250 HP

2000 Boxster - 2.7L - 217 HP
2000 Boxster S - 3.2L - 250 HP
1999 996 - 3.4L - 296 HP

How come a .5 liter increase from 2.7L to 3.2L gives only 33 more HP, but going from 3.2L Boxster to 3.4L 911 gives an additional 46 HP? That is 23 more HP per .1liter of displacement?

I have heard that Porsche intentionally limited the Boxster's power to preserve the flagship status of the 911, but I guess I never rode in a 911 until today (it had a lot of pep)

What all else does Porsche do differently in the 911 such that it has so much more power, and why can't we do that same stuff in the Boxster?

I guess this is not a new idea, but I just never really took a good luck at it until today. So I will just say: Dayum!

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Steve

Yep.......

Indeed, the Boxster is castrated with each model year.
Some more examples:
2013 911 3.4 has 350hp
2013 Boxster S 3.4 has 315 hp
2013 Cayman S 3.4 has 325 hp
2013 base Boxster 2.7 has 265 hp
2013 base Cayman 2.7 has 275 hp

From what I understand, the 3.4 engines are all the same internally and intake/exhaust/ECU tuning accounts for the differences. Ouch.
100 hp per litre is no problem (and the GT3 waaay exceeds this number) but we don't even come close.

Then do you want to tell me why a 2001 Boxster base is way more fun to drive than a 2001 911 even though the Box has way less power? That is my perception anyway.:) The steering? Handling? etc etc.

Because you (not "you" specifically) can't drive a 911 the same way as you do a Boxster for go fast fun. Plus, define "fun to drive". Properly driven, nothing lays the power down like a rear engine 911 from early apex to track out.

talking 3.4 996 vs 3.2 986, from what i understand, bottom end, heads and cams are identical, so differences are displacement, intake, exhaust and tuning. porsche limited the last three to depower the boxster. for relatively little money you can undo this. you could potentially put a 996 intake manifold on your car (heads are the same so should bolt right on) but it is taller (which typically means better mid-range torque) and doesn't fit in the engine bay - youd have to lower your engine like the engine swap guys do (or perhaps get a cayman engine cover which has more clearance)(and get 996 fuel rails to match). otherwise, there are diys to add the intake plenum from a 997, throttle body from a 996 and airbox from a cayman to your car. cant fit a 996 exhaust (points the wrong way) but a cayman exhaust will bolt right up (lots around as take-offs from guys upgrading) or topspeed make a good inexpensive solution. with tuning you gotta pay, but i hope to fit a cayman maf housing to my 3.2 this winter and push a row 996 tune to it and see what happens. if it works ill have an inexpensive tuning solution and remove the final restriction in the intake (the narrow 986 maf housing).

The two engines share the same head castings and camshafts as well as the crankcase, with only an altered bore size.

The 3.2S engine has the most potential for additional performance in stock form by far. Thats because it was seriously handicapped at the factory, BUT the factory did this in a way that didn't cost them much money.

330HP from a 3.2 base engine is our starting point these days, 350 is routine with the Gen 5 combinations. :-)

over 100 hp/L is fantastic. A quick tour through tuning company websites (fvd, softronic, etc.) shows 320 hp as a standard number for the pre-variocam+ 3.4L 996 engine with bolt-ons. that's 94 hp/L. that means a 300 hp 3.2 should be possible just with bolt-ons.

A cayman exhaust will bolt right up to a 986 boxster? Does it add any power or just change the exhaust tone? I would consider this if I could find a nice used one somewhere if it added a few hp

here's a thread;

http://986forum.com/forums/general-discussions/34205-cayman-s-exhaust-boxster.html

there's some misinformation in there, but berty and todd holyoak have the facts - it will fit, it is lighter, it requires that the whole system (headers, mid-pipes and manifold) be changed, it may require extending your post-cat o2 sensor wires, and go for a take-off from a 987/987c 's' model. it sounds better and should be good for a few hp (hey, 10 lbs = 1 hp, right?).

Good headers, high flow cats even a stock muffler and you will be doing great. Finish it up with a 987 airbox, I feel that there is a lot to be had by this mod. IPD plenum is a nice little perk too. Get a good tune and you'll be in 3.4 numbers.

Pedros Garage indicates that these changes will give you 31 more horse. Who knows? It will cost you $1400 to find out but may be worth it.

http://pedrosgarage.com/Site_2/TechnoPower2_Kit.html

I would love for Pedro to post Dyno results.

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.

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.

http://986forum.com/forums/uploads01...1384189194.jpg


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

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?

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

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 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

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 ...

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

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.

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?

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...

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 !

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?

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

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

I ran my cables under the intake manifolds.

Excellent, thanks.

Did you use a 987 S cover or a standard 987 cover? I see both have raised bumps, I wonder if they're different?

I didn't think it was possible to run the cables under the manifold until now... Thanks

I don't know what cover I used. I think there the same though.

make sure jaay hasn't deleted his AC ...

My a/c is still in. I have my top up mostly. It gets hot here.

You can! Get 6 (six) custom ultra-light pistons machined out of titanium (e.g. the flat piston style, F1 tech, same as in the GT3), and get a tuner to design/machine you a set of cams with tad rounder/longuer intake lobes. If you have the cash, you could also get your crank re-machined and ballanced for the flat 6. Custom mapping and all, big big roars

A small and modest $20,000~$30,000 mod (350~400bhp)!

Horses are not cheap these days mate. Hence the higher price on those upper Pcars models.

I beg to differ. The power was intentionally left out of the 3.2 for marketing reasons... My 3.4 986 humiliates non-gt3 996s at autoxs

what's that got to do with horsepower?????

The lack of power wasnt from a lack of funding, it was done intentionally to keep a gap between the 911 and the Boxster. Equal power ususally results in the 911 having its ass handed to it by a boxster

That 2.7 intake is killing the potential of that engine. The 2.7 intake is inadequate even for a 2.7 engine.

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