Over the past few days I've had a long hard weekend of being head down, ar$e up inside the engine bay trying to make this new air intake fit.
In retrospect there are many, many easier ways of doing this but I was determined to give it a go come what may, and the results confirmed by the butt dyno are very impressive.
So to start, I assembled the parts I thought I needed:
Cayman 987.2 TB (75mm)
987.2 Plenum:
note the separate intake tracts
note the dual AOS breathers
Plus a 987 airbox which had been modified already to remove the baffle:
987 dual hose AOS:
Assorted silicone couplers, reducers and 3inch MAF housings
These reducers on the left are to connect the new (much) larger plenum to the inlet manifolds
I also needed this bit. This is a rubber coupler from the TB to the MAF housing
Right, as you can see, the plenum has a vacuum flap in it which is designed to open and shut at different RPM's on the 987 cars. I thought long and hard about running a slave vacuum hose from the resonance flap actuator to this but as the res flap opens at different RPMs I thought I could end up losing power rather than gaining it. I actually wanted to use the 987 plenum for the dual intake paths as I liked the idea, rather than going with the usual 996 plenum which is a much easier (and less destructive) way of doing it. So, the flap had to go!
Actuator removed:
Flap gone!
First step in doing this mod is to open the engine bay and remove the original TB and plenum. The original TB is 68mm mated to an equally narrow plenum. On the other side there is a 75mm intake path which goes to a postage stamp air filter. This is one of the areas porsche used to choke the boxster to prevent it competing with the 996.
The TB, plenum and main intake pipe is easily removed with a few jubilee clips and some allen bolts.
And this is what is removed (note yet another resonance chamber to keep the noise down!):
This is where things start to be a little more tricky. The 986 airbox is held in place by 3 bolts, 2 on the top and one underneath the car. To remove it you also need to undo the inlet manifold on the left side and move it out of the way.
This is the bolt you need to remove (car in the air on the lift):
Eventually after lots of cursing and grazed arms you end up with this:
Next comes trying to fit the much larger airbox:
As you can see you can't fit the new airbox in without removing the inlet manifold because even with it loose and moved over as in this pic, it simply will not fit. In order to remove the inlet you need to get to a few hoses and clips which are difficult to reach. Best way is to approach the engine through the firewall in the cabin:
After another few hours of carefully removing the inlet, squeezing the airbox in (bending the tabs on the engine bay up and out of the way) and replacing the manifold, it ends up looking like this:
There is a big problem mating the MAF to this due to the shape of the bulk head on the 986 compared to the 987. This gets in the way (image borrowed off t'internet)
At this point I got distracted and ended up going on a 180 mile blat with my friend around the countryside, up to Hartside Cafe in the pennies and back!
Adrenaline pumping after a very high speed drive out, I decided to continue with the project. I test fitted the new plenum and TB only to find that the cable to the new TB wasn't long enough! Some emergency surgery was needed to *ahem* extend it:
So, after much more wrangling, modifying the engine bay lip to accommodate the new TB, and generally getting very angry, I managed to connect the MAF pipe to the TB rubber boot and the new airbox:
With everything bolted down and the intake in place I was so relieved. I think I was about 9 hours in now (not including the drive out), so was so pleased to get it all done! I was on a deadline because the car was due at Revolution in Brighouse for an exhaust bypass mod the morning after.
So... I fire her up.... Huge loud pops, bangs, coughing noises up the inlet manifold, flashing CEL and a smell of fuel! :x
Turns out that when I had put the fuel rail back in place, the injector for cylinder 6 had missed the hole in the manifold and was spraying fuel all over the top of the engine rather than into the cylinder!
Ok, deep breaths, just unbolt the fuel rail again and re-seat the injector. No biggie.... Until one of the bolts holding the fuel rail in place decided to just spin rather than coming out
c:
The offending bolt, in a typically very easily accessible place:
By this time I wasn't thinking straight and gave my friend a call (who is also my indy). He sent me this pic of the manifold and injector rail. He said the captive nut was obviously spinning and I needed to chip away the plastic around it to get a spanner onto it:
So, I removed the passenger seat, knelt down, and poking through the firewall with a small chisel I broke the little bits of plastic off to reveal the nut!
After putting a spanner on it, removing the rail, checking everything and re-fitting properly the installation was finally complete! She fired up first time and settled to a steady idle of 710 rpm. I doused all the connections with brake cleaner without a hint of change in the idle and knew I was good to put the lid on.
Unfortunately, the engine lid no longer fits because the long plenum and then TB are fouling the margin where the lid sits. Its almost like they modified the engine bay on the 987 - who'd have thought!?
Anyway, in for a penny, in for a pound:
Peekaboo!
Whilst I was in there putting the passenger seat back in I thought I'd swap the naff speakers which were in the junk compartment with some much better JBL ones:
So, was it worth it?
Absolutely yes. The car revs much more freely. You can hear the new intake shifting much more air. The flat spot at 5500 rpm has gone and where the surge of torque seemed to die off from here it now keep pulling harder. The intake howl is now almost primal in nature and gives you goosebumps!
I did something similar with my previous 986 but removed the airbox and replaced it with a cone filter. I used a 996 TB and plenum which was so simple to fit it was untrue in comparison (plus needed no alterations to the engine bay or lid). The power difference with that one was noticeable too, but not as much as this. The 987 airbox is a true cold air intake, shielded from the engine, sucking air in through the passenger side vent next to the back wheel and with a filter which must be 10 times the surface area of the 986 one.
The power increase is tangible too. On the exit of a roundabout where I normally road test my mods, before the install I could plant the throttle in 2nd and the rear would squat down and push you forwards. I tried this post-install and the rear end broke free and I needed to add in some counter-steering to prevent me spinning! Now that was unexpected!
So in a nutshell - is it worth it? Yes but its very hard going. If you want 70-80% of the benefit for 40-50% of the effort, use a 996 plenum and TB, and use a cone filter instead.
:thumb: