Velocity Factor is an Auto Performance Company located in Boca Raton Florida
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Velocity Factor – MazdaSpeed3 Best Practices for Reliable and Safe Downpipe Upgrades

I wanted to make this post because we have been getting a lot of questions lately regarding performance downpipes for the MazdaSpeed 3, Mazda3, and Mazda3 MPS.

Whenever you install a mod that significantly increases airflow (such as a downpipe), it is important to also tune your engine for this increased airflow.  If you don’t, the ECU will still think that it has the stock downpipe and will inject fuel accordingly.  This means that there is not enough fuel being injected to match with the increased airflow that is actually going into your engine.  This causes a very lean condition, which can be very damaging to the engine because it increases the likelihood of detonation.  If the ping sensor picks up on the detonation, it will cause the ECU to lower your boost in order to avoid further damage.  You don’t want to flirt with overly lean conditions, this is how engines blow up.

Another thing to consider is specific to the Mazda3.  For some reason, the stock turbo on the Mazda3 does not like having a catless downpipe.  When there is a catless downpipe installed onto a Mazda3 or MazdaSpeed 3, the stock turbo tends to overheat and eventually experiences performance degradation and possibly complete failure.  This is something we have observed on many many MazdaSpeed 3 cars that have come into our shop over the years.  As a result, we HIGHLY discourage our customers from installing a catless downpipe onto their Mazda3 cars unless they are also putting in a different turbo as well.

OK, so that’s the bad news.  It’s not all doom and gloom though.  Depending on how long you have been driving around with the catless downpipe, your oil-change habits, your driving style, and your ambient heat levels; the stock turbo may still be in good working order.

The first thing is to take off the catless downpipe and replace the stock downpipe.  Then reset your ecu (disconnect your battery for a few minutes to an hour).  Then drive it around for a while.  This will allow the ECU to recalibrate itself back to the stock airflow levels.  If you notice your performance improving, that means the turbo itself is probably still fine.  If not, then you may need to rebuild or replace it.

Once you determine that your turbo is good (or replace it if it’s not), you can start adding power.  To safely build power, the first thing we recommend is to do a tune.  For the Mazda3, MazdaSpeed3, or Mazda3 MPS, we suggest the Cobb AccessPort.  This is really the best bang for the buck.  You can get around 9% increase in safe reliable daily-drivable power with just the stock car.  The AccessPort is nice also because it acts as a diagnostic device, gauge cluster, and will help you to continually optimize your car’s tune as you add more upgrades.  The Cobb AccessPort really is a wonderful tool and should be the first thing someone buys when they are looking to make power or increase efficiency.

If you want to add even more power, you can install a performance downpipe with a high-flow cat.  You will also want to upgrade the fuel pump since the stock fuel pump will not be able to keep up with the increased demand for fuel.  We recommend the Cobb high-flow-cat downpipe and cp-e high performance fuel pump.  Once those parts are installed, be sure to reflash your ECU fuel map with the Cobb AccessPort.

You can also look at some supporting mods such as upgraded intake, intercooler, turbo inlet pipe, and engine mounts.  These will all serve to give you increased performance or reliability.

Another thing to consider when driving a car tuned for performance is your fuel.  We suggest using 93-octane gasoline.  If you do not have 93-octane available in your area, then use whatever the best available grade of gasoline you have and adjust your tune accordingly.  Better fuel reduces detonation and keeps your engine cleaner longer.

If you would like some more help, please feel free to give us a call. We are always happy to provide free advice and support to our blog readers. Our number is 561-395-5700. We are open Monday-Friday 10:00-6:00EST, and Saturday 12:00-4:00EST.  If it is easier for you, we can also discuss your issue over email or through facebook at

Also, be sure to read our two-part article about stage-1 and stage-2 power upgrades for more details.

MazdaSpeed Stage-1 Power Upgrades

MazdaSpeed Stage-2 Power Upgrades

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