In case you missed it, we have been working on improving the flimsy rubber tube that comes stock on the cold side of your 2018+ Mazda 6 2.5T. Check out the first part on the cold side boost tube here and the full OEM piping & intercooler breakdown here. Since our last installment, we have been busy testing a prototype CorkSport Boost Tube and would like to share some results with you all.
Starting off we tested and data logged both the OEM tube and CorkSport Performance Boost Tube on the dyno. We were not expecting to see too much of a difference to power with just the boost tube changing however, we did see tiny improvements here and there, most notably way up at the top of the RPM range.
Check out the graph below, OEM=red, CS=green. We tested on the same day in identical conditions and the car had a CorkSport Intake and
Cat Back Exhaust installed for both tests. PLEASE NOTE: the variations below 2800RPM are due to inconsistencies associated with dyno testing an automatic car.
After noticing these changes, we went to the data logs to see how the boost changed between the OEM tube and the CS Boost Tube. The graph below shows the engine RPM versus the manifold pressure in psi. Both lines have the same smoothing done to the raw data. As you can see, the CorkSport tube (green) holds about 0.5psi through the midrange (3500-5000RPM) and is almost 1psi more when above 5500RPM. This correlates well with what we saw while dyno testing.
The small increase in boost pressure is likely due to the CorkSport tube not expanding as much when under pressure. To confirm this, we capped off both ends and pressurized the each tube to 20psi. Note: do not try this at home as the caps can easily fly off and injure you.
After measuring multiple locations both before and during pressurization, we found that the OEM tube expands about 12% in internal cross-sectional area while the CorkSport Boost Tube expands 3x less at 4%. Keep in mind that this would be an even larger difference if the same test was performed with the tubes installed on the car due to the heat of the engine bay. Since silicone is more stable than rubber at high temperatures, the heat of the engine bay will not soften it nearly as much as the rubber OEM boost tube. A softer rubber tube would mean even more expansion when pressurized and even more inconsistent boost pressures.
This data may not show drastic changes but it does not tell the whole story. The larger diameter and thus larger volume of boosted air of the CS tube provides a little bit better response when low in the RPM range. While this may just be a placebo effect on our end, there’s not too much of a wait before you can try it yourselves! Stay tuned for more information. If you want a more serious upgrade though, keep your eyes out for information on the upcoming CorkSport FMIC kit and Piping Upgrade kit!
P.S. 2016+ Mazda CX-9 owners and future Mazda CX-5 2.5T owners, don’t worry we will be checking this for fitment along with other CS goodies!
-Daniel @ CorkSport