Project E46 M3: Part 11 – Castro Motorsports air box installed and dyno tested!


Here’s a close-up of the intake plenum connected to the throttle bodies.  As mentioned earlier, you can save yourself a world of hurt by leaving the silicone couplers on the throttle bodies themselves and slipping the intake manifold onto the couplings from there, rather than doing it with the silicone couplers on the manifold itself.
After having uninstalled and reinstalled the intake manifold numerous times before this dyno test, we were able to perform these back-to-back tests just moments apart.  With our Castro Motorsport intake on, not only did we gain back the torque lost from having no plenum at all, thanks to the integrated CM velocity stacks, the CM plenum also made 8 to 12.5 more whp up top from 7500-8200 RPM!  And keep in mind this is compared to a baseline with the EAS Stage 1 intake kit still installed, not against a real bone stock intake setup with the accordion intake tube.

We have to remember that when we tested the EAS Stage 1 intake kit versus our stock unit, it proved to be a good bang for the buck.  And most of this gains arguably came from the silicone elbow that replaced the stock accordion unit, as described in Part 1. 

The EAS intake was responsible for 3-5whp gains up top, so if we were to add those back, we’d see slightly larger gains up at this RPM level with this intake plenum over a completely bone stock intake tract, assuming all other components are left untouched.  No other modifications to our AEM EMS software were made.

Driving with the Castro Motorsport intake on does bring back a little bit of that conical “roar” that’s so missed on the E46 M3.  The best of both worlds would be an E36 M3 induction sound with actual E46 M3 performance.  But this intake maybe gets us to about 50% of the audible tune.

Given the fact we were left with moving onto at least cams or forced induction to get to the next level in performance, the Castro Motorsport air box was a welcomed addition to our modifications stable, giving the car a bit more performance with a more visceral experience, thanks to the new sound (check out the videos on Page 10!).  Plus, given the size of the box and mega K&N filter, it’s total eye candy when you pop the hood!  We’ll be looking to finish the airbox in black-wrinkle paint to match the factory cam cover soon.

And now let's switch gears and check out some of MKC’s recent guests!

Keeping in line with the “normal aspiration power” theme, while I was at MKC one day I noticed them tuning a nice NASA-sanctioned Dodge Viper road racer.  It put out one of the most impressive normally-aspirated dyno graphs I’ve seen to date.

With just under 600whp, what you may not notice right off the bat the fact that this engine has a porker of a torque curve.  It’s too bad the dyno didn’t have a tach readout or we’d plot this over RPM.  But by my loose calculations, assuming factory transmission and tire sizes, this horsepower graph equates to what starts at 440 lb-ft of torque and steadily rises to 500 lb-ft in the midrange, and stays in the mid 400s to the finish.  Yes, that’s 440 lb-ft at just 2500 RPM! 

How does that saying go again?  Oh yeah, “there’s no replacement for displacement,” and of course RPM.  I can't imagine how fun it would be to experience low-speed turn exits with all of that race-rubber grip, combined with the torque curve of this torque beast.


Upon first glance, this pretty blue E92 BMW 335i doesn't seem like anything out of the ordinary.  I mean, several 335i owners equip their cars with just aftermarket wheels anyway.  This car looks like it could have a software upgrade, and maybe a couple of other tidbits. 

What do we think?  320whp?  350whp?  How about a very respectable 400whp?  Hmm.  Wrong.  Find out on the next page.

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