GVA-SFO

I could understand that the air intake of the 986 M96 could be very a serious "limiter".
I can observe/understand that the “differences” between the M96 of a 986 v.s. the M96 of a 996 are most probably limited to :

1) the Air Intake
2) the Exhaust Headers
3) the ECU tuning tables

I would say that they are “after market” suppliers of exhaust headers (2) as well as ECU (reflash services) (3), but :

What is dam strange is that there are **NO** "after market" suppliers that have made products that would enhance performance by providing high flow air intake and runners.

Sure, some people have adapted (all but not an easy job) 996 intake manifold, but as the whole setup is reversed, you can end up with difficulties to build a clean mod. (Taking in account that beside less room is available above the engine, in the Boxster you also have the shift cables running on the top of everything, ..just below the “cover” !

I’m very surprised that companies (i.e.: like IPD) have invested in tooling to provide high quality Aluminum plenums (beside for the 986, also for plenty of other P-models !), ..but no ones went for a well done, performance intake manifold box, knowing that the Boxster OEM ones are one the most critical limiting devices of the M96 of the 986 !

I can even think that an Aluminum intake manifold, ..that could be even cooled down would be a real nice to have, and I think, many of “us” would be happy to purchase one !
Why no company offer such “device” ?

GVA-SFO

For the “fun”, about the “other limiter” (the exhaust header), here is how I tried in my side to work on this problem keeping on mind that I did not wanted to increase the noise :

a) design of an cat entry piece of metal that would max flow in all the cat entry surface from the 3 tuned tubes : (Plasma laser cut locally)



b) Using a “competition” cat less header, and cutting the 3 in 1 at the end of the 3 separate tubes (tuned in length) and solder these 3 tubes on the “inside” of the “3 holes” circular plate

c) Cutting the entry cone of the cat (performance model), to be ..at the diameter of the “circular plate”.



This makes the gas flow entering as freely as possible into the cat, ..and using the cone of the other side of the cat acting as the “3 in 1” jog, going into the OEM 3 bolts connection, ..at the exact same position. (..in case of having to go back to OEM part ..if the concept would not work !)
Here is how it looks from under. Not much room left, ..but it does fit.



I have not used a dyno, to measure the WHP (yet), but being a “standard” driver, I’m able to do laps in Laguna Seca in the 1.48 range quite “easily” (GranFa style ) ..with my standard 2001, 65k miles 3.2S OEM engine.

GVA-SFO

An interesting page to read, sure, off topic, as this is about 9A1, not M96 !
https://demanmotorsport.com/4-25l-gt4-engine-upgrade/
or, ..a love story, with a 4.25 "Pig" !