Huge Gains with Turner CSL Airbox + Epic Tune (Dynos Included)

[3002 tii]

Normally I'd just post a small update in the What did you buy thread but I thought this warranted its own thread. I pushed off the idea of converting to a CSL airbox for the longest time based on conflicting things I'd read over the years, e.g., poor drivability, very modest gains (low ROI mod), etc. But after consulting with tuners and listening to first hand experiences from racers in the paddock, I decided to pull the trigger on a TMS v2 airbox in matte black (note current price is bit higher than what I paid last month).

I won't go into the install as it's been covered in detail numerous times by others. But what I will focus on is the tuning. The gains with this box are real so long as you go with a quality tuner. In my case, I went with Randy at Epic Motorsports but I know Josh at Severn achieved similar gains on Michael9218 build after accounting for SAE vs STD. Ultimately, I can't see you going wrong with either tuner; the key is making sure you can schedule dyno or datalogging with said tuner.

Turner Matte Carbon finish

I don’t have a stock baseline so we’ll have to use my header tune from April 2024 as a relative starting point. It’s worth noting all runs were performed at the same Dynojet facility and ambient temps were pretty similar (spring 2024 vs fall 2025), so I consider these runs comparable. Lastly, all figures below are stated on a corrected basis (i.e. SAE 5).

Baseline - 298whp | 237lb-ft

• Epic Off-road (OTS)
• OEM Euro headers
• DKF section 1 w/ 100 cell hfc
• Stock intake + charcoal filter delete
• Est. delta of +23hp (based on research, a healthy stock Z4 M puts down ~275whp)

CSL Airbox - 318whp | 242lb-ft

With the following hardware changes & updated reflash…

• Epic Alpha-N (OTS)
• TMS CSL airbox
• TMS underdrive pulley
• Supersprint x-pipe
• TTV Racing flywheel
• Incremental delta of +20whp

It’s hard to discern how much of the 20whp gain is attributable to airbox only. My best guess is pulleys, flywheel and exhaust freed up 7-10whp, but not sure it matters. The gains from the CSL airbox + Alpha are certainly double digits. Reason I say that is because the Alpha-N map was a canned tune, initially uploaded just so I could drive the car and eventually make my way over to the dyno. But the intent was to always get a custom dyno tune. I can’t say for sure what tweaks were made but at minimum, the IAT was rescaled to help lean out the car. After about an hour of trying 3 different maps, the final result was 337whp | 256lb-ft, an incremental gain of 19whp.

Needless to say I’m quite satisfied with the overall results. Knowing our cars tend to come in lower than our M3 counterparts, I went in thinking 320whp was an optimistic number, so a net gain of 40whp (or ~60whp over stock) surpassed my expectations.

[3002 tii]

Note - above is the "final" dyno but there were at least 6 more runs not shown that correspond to 2 iterations of the tune that were updated on the fly.

And here's one with all 3 overlaid for easy comparison:

[Efthreeoh]

Not a flame, but you have too many variables in the equation due to the associated hardware/software changes to make a statement regarding huge HP gains due to the airbox. Good overall improvement though.

[3002 tii]

Originally Posted by Efthreeoh

Not a flame, but you have too many variables in the equation due to the associated hardware/software changes to make a statement regarding huge HP gains due to the airbox. Good overall improvement though.

Didn't take it as a flame, but I thought I addressed the other 'variables'. Even if I'm being generous, I doubt those contributed to more than +10whp. So unless we're focused on what's the 'threshold' for "huge", I think a pickup of 20 to 30whp from airbox & tune are pretty substantial, no?

Edit - updated title to reflect the tuning as significant contributor.

[Efthreeoh]

Originally Posted by 3002 tii

Didn't take it as a flame, but I thought I addressed the other 'variables'. Even if I'm being generous, I doubt those contributed to more than +10whp. So unless we're focused on what's the 'threshold' for "huge", I think a pickup of 20 to 30whp from airbox & tune are pretty substantial, no?

Edit - updated title to reflect the tuning as significant contributor.

Absolutely substantial. I bought my Z4 Coupe with the N52 for high-miles and low maintenance with longevity in mind. No real tuning the N52B30 3IM except maybe with MILVs, but I think they are no longer available.

[maupineda]

The X pipe will give ZERO. Pulleys and Flywheel would only reduce drivetrain losses, and will not make power. They help to have less drag but these dynos do not calculate drivetrain loss and thus would not alter the number by much.