Exhaust system upgrade

Goodwin exhaust installation review impressions MX-5 Miata NC

I decided to change full exhaust system to Brian Goodwin's:

• Roadstersport header

• Roadstersport midpipe

• Roadstersport Q muffler

• Front and rear O2 sensors extension cables

Boxes arrived after 12,000 km travel and are about to be installed:

Shipping wise - header is the smallest box and muffler is the biggest.

The packaging is really good - great job Brian !!!

Old parts are out:

New parts unpacked:

Comparison of Goodwin header and stock header with heat shield plates removed:

Stock muffler and midpipe were removed pretty easily.

Stock header romoval took about 1.5 hours.

It's not easy to remove bolts that connect the header to engine.

To get the header out is also a challenge.

The mechanic slowly but shurely removed header's heat shield plates.

Then one of the cabin heater's pipes was disconnected to clear the room (only few drops of coolant were spilled - so don't be afraid to do it) and the header came up pretty easily.

As for the installation - the mechanic installed hearder and muffler first.

Then he did midpipe.

It took less than 1 hour in total.

O2 cable extention for the front sensor was a bit short - so we unclipped the black connector (that the cable goes into) from the engine and it gave enough length.

For the rear O2 sensor the extension cable was way too long (definitely better than too short). So we could route the cable as far away from the exhaust piping as possible.

Small issue - metal rod which is welded to the middle of the midpipe and goes into rubber "holder" (the part that holds midpipe suspended in the air) was a bit too long and touched PPF.

My mechanic just cut about 1 cm from it to make it shorter:

Total removal and install took about 5 hours.

Now to the emissions test:

Carbon particles (HC) increased significantly and CO has trippled.

So removal of one catalytic convertor shows pretty clear.

Good news for me that it's still compatible with local regulations. Your local regulations might be different.

An update - another member from our local Roadster club installed exactly the same setup at the same workshop and measured his emissions with exactly the same equipment.

Following are his results:

As you can see his readings are significantly different - some better some worse.

This is not a big surprise - as we saw countless number of times that emission readings are not consistent - even with the same car in 30 minutes period.

Any problems?

Sorry to say - YES.

Two times i got Check Engine lite (CEL).

Scangauge showed P0031 and P0130.

Those are "front HO2S circuit" related.

Basically speaking it shows a problem with reading front lambda/O2 sensor.

I start to think that problems are just inevitable whenever we do aftermarket improvements :-(

Brian was very supportive over the email - big thumbs up for him.

Putting the car on the lift we found the problem pretty quickly - front O2 sensor's connector just started to melt:

It's just too close to the exhaust piping - and with this setup there is no heat shielding over the piping - so now cables and connectors are exposed much more to the excessive heat.

We couldn't find a way to mount connector in a way that ensures sufficient heat protection - so we wrapped the connector in a special military and space grade material which stands heat of almost 2,000 degrees Celsius (this material is a heritage from my turbo Croc Machine #1 - lucky me).

I hope that now this is solved.

So how does it feel?

In one word - fantastic.

Final result is engine breath so easily and from 3,000 rpm there is very good torque.

Exhaust sound is very good and it's really loud only in about 2,500-3,000 rpm range.

Would do i do it again?

In a heartbeat !!!!

It's not cheap but well worth it.

Update on oxygen sensor problem:

No matter what i did a Check Engine Light (CEL) kept coming on.

I tried removing melted plastic connector and some other stuff - but eventually i came to conclusion that O2 sensor is dead.

You can drive like this no problem and i even passed local MOT emissions test like this - but with front oxygent sensor dead the engine is running constantly in "Open Loop" which is a bad thing - too much fuel poored all the time damaging in a long run ignition plugs, catalytic converter, engine oil, etc.

Unfortunatelly Brian Goodwin didn't want to help me to get a new sensor or to work on a longer extension cable - he just sent me to Mazda dealers to get a new sensor (MSRP ~430$ ouch!!!) and to talk with Racing Beat about a new cable.

Frankly speaking i expected a better after sales support.

Fortunately Bill from www.miataroadster.com could help me to get the sonsor much cheaper and to work with Racing Beat on a longer cable.

Since new sensor and cable arrived and were installed - no problems.

The last update:

Prior to selling the car i removed the whole exhaust system and Mazdaspeed's CAI and drove like this for a few days - car became much lazier and chocked above 5,000 rpm.

It felt gutsier at around 3,000 rpm which might be more suitable for city driving - but for spirited driving it feels really boring.

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