987 / 986 3.2 S upgrades

berty987 · Oct 24, 2010

I´ve been watching the other forums regarding upgrades to the boxster and cayman engines. The fitting of a Gt3 82mm throttle body in place of the standard 76mm item fitted to the cayman 2.7/3.4 seems to have good results. I did some research and found that the 76mm cayman TB is offered by FVD as an upgrade for the 3.2 boxster. Though the inlet manifold of the 3.2 boxster is smaller than the cayman 2.7/3.4 (and boxster from 2007 onwards) the valves in the head of the S model boxster 987 and 986 are the same size as the 3.4 carrera 996. This suggests to me that the heads can take more airflow , particularly with a different cam.

A little more digging turned up some info on the 996 X51 powerkit for the 3.4. A higher cam lift , gas flowed inlet and exhaust tract and pistons to accommodate the increased valve lift , seem to be the main differences. Does anyone know if the X51 996 head would fit a boxster , since the bore is the same ? Has anyone tried this on a boxster ?

Nick_USA · Oct 25, 2010

This may be of interest:

http://www.planet-9.com/reviews/cayman-performance-modifications/p283-porsche-x51-intake-installation-3-8s-intake28x51-29-on-3-4.html

I am running the GT3 intake in my MY08, which reminds me I still have the original intake in the garage and a 3.2S guinea pig sat on the drive [8D]

However whilst the addition of the intake may help a little, the engine would have to be remapped to get the true gain. Plus what is done on the intake side should be complemented on the exhaust side with a free flow system.

For all those wannabe amateur tuners it should be noted that modifications don't add to each other. So whilst a intake mod may add 10hp, a remap 10hp and new exhaust 10hp doesn't mean that together they will give you 30 extra hp.

The do compliment but do not add to each other.

berty987 · Oct 25, 2010

Hi Nick,
Yes I'm aware that the tuning isn't cumlative , but since the 987S already has performance manifolds , I'm working on the basis of the FVD web site , which claims 20 hp over the standard , with no need for a remap. If the increment is small enough , the standard fuel settings should be able to adapt , this is certainly the inference from FVD. The inlet and exhaust valves of the 3.2 boxster are the same size as the stock 3.4 996 so I'm assuming that there isnt much restriction in the head , only possibly the cam could be enhanced. On that subject, I also looked at the 996 X51 powerkit and it seems the +20 hp gain is achieved by using different cams with higher lift , ported inlet and outlets , different valve seat angles and bigger exahust manifolds. Since the 996 and 987 3.2 share the same bore size I'm wondering if x51 heads could be an upgrade (though the uprated pistons would also be required).

The idea of the throttle body mod is that its potentially very cheap and a DIY mod. Remaps are at best 500 pound options for a boxster and 1000 or 2000 for a full exhaust system.

The ECU cannot adjust the amount of air available beyond a fully opened throttle , and "performance" filters often only give marginal gain when new (the 987 filter is already very well optimised over the 986 version). If its possible to allow more air into the inlet by increasing the TB size , I reason that an ECU remap and de cat of the rear silencers should give better results.

I'm assuming that fitting a bigger throttle body will improve (increase) both power and torque without compromising emissions or capability to run on lower grade fuels / high altitudes , which is often the case with a remap.

If you can retain the inlet body T piece or upsize to the cayman unit , it should work as its designed , to improve low end torque by nature of the butterfly valve being closed at low RPM and open at higher values. Those that have removed the inlet body have complained of a loss of low end torque even with IPD plenums so I'd rather stick with the original design.

berty987 · Nov 4, 2010

I now have some data to suggest the 3.2 S 987 can be upgraded with the cayman 2.7 / 3.4 (boxster / cayman M97 engine) inlet distrubter (plenum) and 75mm throttle body. Its a straight swap , though does require the original inlet manifold hose sleeves to be used as packing . Gains are throughout the rev range in torque , above 3500 the power increases by a steady 10 hp , the torque by a similar figure. No ECU reflash is necessary and unlike the softronic / gt3 / IPD plenum upgrades there is no loss in low end torque. Simple DIY mod that gives genuine results.
Though this mod also applies to the smaller 2.7 M96.25 engine 987 the gains may not be as significant as the exhaust isnt a performance manifold version and the valves in hte heads are smaller on both inlet and exhaust. The 2.7 already shares the same throttle body and inlet plenum as the larger 3.2 suggesting that is already possibly oversized or at least matched.

The 986 3.2 uses the same throttle body as the 987 , but does not have the split inlet distributor tube and flap , therefore the cayman part doesnt fit. The suggested mod for the 986 is to fit the inlet plenum from the 996 3.4 with matched throttle body (75mm). On this install there is also some additional work required on the hose that links the throttle body and the MAF. This is required because the 996 plenum is a square T whereas the 986 uses and angled item due to differences in layout and position of air box/ filter. There are kits available form people such as FVD , softronic , and IPD that claim additional gains thanks to a custom inlet plenum.

My experience is that these custoim inlet plenums can give max HP gains higher than the cayman inlet mod on the 987 but at the expense of low end torque . The split inlet used plenum and changeover flap arrangement on the 987 models was specifically designed to improve low end torque. Since this isnt present on the earlier 986 , using an aftermarket plenum is not so much of an issue.