Mazdaspeed 3 Exhaust Manifold Break Down

Today we want to break down the OEM exhaust manifold for the Mazdaspeed platform so that you can better understand how and why the CorkSport Manifold makes power.  

If you haven’t heard, CorkSport has been developing a performance cast exhaust manifold for the Mazdaspeed platform.  We’ve tested and validated samples on Mazdaspeeds ranging from 350whp to 684whp. We’ve done dyno testing on the OEM exhaust manifold vs the CS manifold, as well as on the XS Power V3 manifold vs the CS manifold with the man, Will Dawson of Purple Drank Tuning, setting the calibrations. Both tests showed good gains from just the CorkSport Exhaust Manifold alone.   However, we can get into those details later.  

Mazda Exhaust Manifold Design

Mazdaspeed Exhaust Manifold Flange
OEM Exhaust Manifold Flange

This is the OEM (original equipment manufacturer) exhaust manifold found on the 2007-2013 Mazdaspeed 3 and 2006-2007 Mazdaspeed 6.  Manufactured from cast iron and very compact in design, the OEM design leaves A LOT on the table in the performance department.   

In the image, we’ve labeled each cylinder since that will be important for later discussion.  

OEM Manifold Exhaust Flow

So now let’s talk flow.  Fluids (or exhaust gases in this situation), will always take the path of least resistance.  When the flow path is not clearly defined for the exhaust gas, such as a merge between different cylinders, turbulence is created which reduces the efficiency of the exhaust manifold. 

A prime example of turbulence is shown in the image above with the orange arrows at the merge for cylinder 1 and cylinder 2.  Cylinder 2 comes to a “T” and therefore could flow left or right.  This creates turbulence which causes a loss in potential power.  

Next is the yellow arrow.  This is identifying the inner diameter of the runners in the OEM exhaust manifold.  To our surprise, the inner diameter of the OEM exhaust manifold is actually pretty decent at ~1.48 inches.  This diameter partially defines the power a manifold can support efficiently. Bigger is better in this situation, but small changes here will make big differences in the final performance. 

Surprisingly, there are “performance” exhaust manifolds on the market for the Mazdaspeed platform that have smaller inner diameter runners… 

Mazdaspeed Exhaust Manifold Gasket
OEM Exhaust Manifold Gasket

We also wanted to point out an unusual but important aspect of the Mazdaspeed exhaust manifold and gasket.  Have you ever noticed the seemingly useless extend flange off of cylinder 4? This extended flange acts as part of the passage for the exhaust gas recirculation port.  

You can more clearly see this port path in the gasket.  

OEM  Exhaust Manifold
OEM Exhaust Manifold

Designing For Efficiency

In this image, we want to direct your attention to a very unique and troubling design feature of the OEM exhaust manifold.  There is a right way and wrong way to pair cylinders on an exhaust manifold for a 4 cylinder engine… and this is the wrong way. 

Referencing our cylinder callouts in the first image above; you can see that the OEM design pair cylinder 1 & 2 together and cylinder 3 & 4 together.  This design physically works, but it is not ideal from a performance standpoint. In a divided manifold you should pair cylinders 1 & 4 together and cylinders 2 & 3 together for optimal cylinder exhaust gas scavenging. To learn more about exhaust scavenging you can check out a blog on that here, or watch the video below!

Exhaust Gas Scavenging. See the difference between the CS and OEM Manifolds.

Before we wrap here we do have one good thing to say about the OEM exhaust manifold.  It does sound really good and gives the Mazdaspeed platform a unique exhaust note, but don’t worry you don’t lose your unique rumble with the CorkSport design.   

Thanks for checking in with CorkSport Mazda Performance.  Stay tuned for more info about the CorkSport Performance Exhaust Manifold.  

-Barett @ CS

Exhaust Scavenging

In this blog, we are going to SHOW a demonstration of exhaust gas scavenging.  Instead of a lengthy blog full of text, we’ve opted to create a video that demonstrates the effects of exhaust gas scavenging for both good and bad designs.  

We will be comparing the prototype CorkSport performance exhaust manifold, developed for the Mazdaspeed 3 and 6, to the OE exhaust manifold.  

Exhaust gas scavenging within a manifold is the process of one cylinder runner, pulling (aka scavenging), the exhaust gas from an adjacent cylinder in a continual cycle.  Now enough talk, to see an awesome example and an awful example of exhaust gas scavenging check out the video below. BONUS! Not only do you get to see what optimal scavenging looks like, but this is also the first sneak peek of the CorkSport Performance Exhaust Manifold…

Video Link: https://youtu.be/RtydboDbwpQ

We hope you found this as interesting as we did!  Stay tuned as we continue developing the CorkSport Performance Exhaust Manifold for the Mazdaspeed platform.

 

-Barett @ CS

Performance Turbo Exhaust Manifolds – Tubular or Cast?

If you have been in the car scene for a while, you have probably seen or heard of performance exhaust manifolds.  Like any other component on the engine that affects flow, performance exhaust manifolds can have a significant improvement to the engine’s peak performance and power under the curve amongst other aspects that the exhaust manifold can affect.  

You have also probably asked the question. “What type of exhaust manifold do I need?” In this blog, we at CorkSport would like to help you better understand the differences between cast and tubular so you can make the best decision for your Mazdaspeed.  

There are two main styles on performance exhaust manifolds; tubular and cast. Both have their pros and cons to consider as an end user (that’s you the enthusiast) and as the designer/manufacturer (that’s us at CorkSport).   

First, let’s look at tubular as it’s the most common in the performance industry.  Tubular is the most popular option because of it manufacturing flexibility.  Unlike casting, tubular does not require expensive molds to develop even a single prototype. Not needing expensive molds allow great flexibility in design and manufacturing, which lends the tubular manifold as an exceptional option for one-off builds.  

To fabricate a tubular exhaust manifold you need just the raw components: flanges, tubular sections, collector and fabrication supplies, and of course the expertise to fabricate the manifold.  Let me emphasize the necessity of fabrication skills here. To produce a reliable and performance proven tubular exhaust manifold takes the correct skills, tools, and patience…it’s honestly a work of art.  

With this work of art does come some compromises.  To create the necessary runner routing, many tubular sections will need to be welded together.  This increases the chance for weld impurities and slag which can later result in cracking and poor performance.  Any reputable fabricator should be able to avoid this, but it does come at a premium due to the many man hours that must go into each and every manifold.  

Next up is cast.  Manufacturing via casting provides a different set of opportunities and difficulties to overcome.  The process of casting alone has restrictions that must be considered; such as mold design and molten flow in the casting.  Assuming these issues are overcome casting can provide unique opportunities for the design to improve reliability, performance, and packaging.  

A well-designed cast exhaust manifold can have great reliability due to its one-piece design.  There are no welded joints that can crack or fail and casting typically has a higher threshold to heat before issues arise.  The wall thickness of the casting can also be defined for the application which can improve strength if the exhaust manifold is the only part supporting the weight of the turbocharger.  

Overall performance can also be affected due to the casting design flexibility with each runner.  Unlike tubular, a cast is not restricted to standard tubular elbows and straits. The runners can bend and change profile as desired to aid in performance and packaging.  

Speaking of packaging, casting can really change the game here.  Since each runner does not have to be accessible for welding, the entire design and each runner can be tightly packaged together to reduce the overall size of the exhaust manifold and better retain heat which aids with turbocharger response.  

Lastly, comes the cost to you the enthusiast.  Although the upfront cost of a cast manifold can be high, typically the unit cost and necessary man-hours are low which helps keep cost down for you.  

As a designer and manufacturer of performance parts for you Mazdaspeed, these are all things we have to consider providing you with the best parts possible.  We’ve explored both and are happy to stick with casting as we feel it provides the best balance reliability, cost, and performance. Keep a look out for future projects and updates!

Thanks for tuning in with CorkSport.

-Barett @ CS