In the last blog post we discussed the design of the new 27Won Mid-Pipe back exhaust for the Civic Hatch Back Sport, but we left you a cliff-hanger as far as power goes. 

Well I’m happy to share that we got the car on the rollers and have some data to discuss. 

A key dimension I did not discuss in the last blog is the diameter of the piping used for the 27Won Exhaust System. 

The OE exhaust system uses very small 50.5mm (2in) piping for the entire exhaust system. This is just not ideal for a performance exhaust system, especially one for a turbocharger equipped engine; in fact the OE 50.5mm exhaust is close to its maximum power capacity before substantial power loss will occur due to the flow restriction.  This will be shown clearly later with some dynographs.

With this knowledge, we opened up the exhaust piping to 63.5mm (2.5in) to help move the exhaust out of the engine more efficiently.

Going from 50.5mm to 63.5mm provided a 58% increase in cross-sectional area of the exhaust piping. 

This is a huge increase in potential flow and should be good to support 400-450 horsepower before showing significant flow restriction.

Let’s see what the dynographs have to say. 

First off, let’s lay out the testing conditions, as a good test should have minimal variables affecting the testing data.

All testing was performed on a DynoDynamics load-based 2WD dyno on the same day. Temperature through the day was very stable around 80-90F ambient. The load-based dyno allows us to set our start and stop speeds and the ramp rate in which the dyno allows the engine to rev up. This control allows us to create very repeatable data so we can focus on the change in wHP and wTQ. 

We performed back-to-back testing on two different tunes; the Hondata OE Equivalent and Hondata 9psi Professional Performance. 

We did this because we wanted to see if the increased power from the +9psi tune would provide a larger increase in power between the OE and 27Won exhaust systems. Also, there are no other performance parts on the vehicle being tested…but there will be soon ;)

Let’s look at the OE Equivalent dynograph first: 

With the OE Equivalent tune we see a small increase in wTQ from 2750rpm to 4000rpm and then a nearly consistent match of power and torque up to 6500rpm for a peak gain of 1wHP. 

This is not surprising as the OE exhaust is basically sufficient for this power level. Let’s look at the +9psi tune as it tells a different story. 

With the +9psi tune we see a much more defined improvement across the entire RPM range. 

The largest gains come through with increased torque in the meat of the RPM range; 3250rpm to 5000rpm. 

However, we do still see the significant drop off in power after 5250rpm, but there are still gains here with the 27Won exhaust system. My gut tells me the cause of this substantial power drop is not a factor of exhaust size, but of something far more important to the engine flow and performance…perhaps the turbocharger size…this will be a great discussion later, but back to the exhaust. 

Between the two different tunes, we see around a 24whp increase in power for the OE exhaust and 26whp increase in power with the 27Won exhaust with clear gains across the entire RPM range. 

This tells me that the OE exhaust is close to its maximum power potential, and as this platform grows in power an oversized exhaust system will become more and more important to hitting those power goals. 

As the icing on the cake, here is a video so you can see and hear this beauty yourself.

Thanks for tuning in, you can catch more info about what's going on at 27Won Performance in the next blog!

I dare YOU to Redefine The Aftermarket

-Barett @ 27Won Performance