Joel's 2007 Mazdaspeed3 GT

Mods List:

My wife and I bought the car new in June 2007, as of July 2012 it has 110,000 miles on it. We originally bought it to take to car shows and use as a performance project car. For the past few years the car has been her daily driver. With the amount of driving she does at work, reliability and fuel economy became more important than performance. We didn't want to suck and trade it for an econo-box though, so we kept it.

The good news is, almost every performance mod we've made has improved fuel economy as a by-product of making more power through improved engine efficiency. I installed a Mazdaspeed Cold Air Intake kit ($300 from the dealer, made by AEM) when the car had about 20,000 miles on it. The CAI doesn't replace all the piping before the turbo, and the turbo inlet pipe is a mangled restrictive mess of molded plastic, so I fabricated a 2.5" mandrel bent aluminum inlet pipe with the proper connections for the boost control solenoid and the compressor bypass valve return tube. The factory intake is very restrictive so I expected large gains. Peak gains were around 35whp (see dyno charts below). I also cut out two of the resonators from the exhaust and replaced them with straight tubing to make the car a little louder (it's about the same volume as an aftermarket cat-back now). The factory exhaust is 2.5" mandrel bent stainless steel, so I didn't see a need to upgrade it on a ~300whp car. I also experimented with cleaning up some casting flaws in the top mounted intercooler, and found another few whp (about 5).

The factory 18" wheels and tires performed very nicely, but were heavy for their (lack of) width. On the poorly maintained roads in my area pinch flats were a real problem, too. After ruining 4 tires within 3 months I decided we would have to downsize the wheels to gain some durability. I also wanted to take advantage of more wear resistant tires not available in the factory tire size. I ordered a set of 16" Sport Edition F2 wheels from Tire Rack. They fit very nicely (they just barely clear the brakes) and are 4 pounds lighter than the stock 18" wheels, and the 205/60-16 Yokohama Avid Touring S318 tires are 5 pounds lighter than the stock 18" Potenza RE050A tires. Nine pounds per wheel is a substantial weight savings. The size change has also solved the problem with the pinch flatting, in the 3 years since we changed the wheels there has not been a single flat tire. We did sacrifice some performance with the 10mm reduction in section width, two inch diameter drop in wheel size and the move from performance tires to touring tires, but it's not as bad as it seems. You only notice it if you ask the car for more than 7/10ths.

If you frequent any of the online Mazda forums, you're probably wondering where my rant is about all the stuff that broke or what a POS this car is. Well, there's a reason you missed that part...
The car has been VERY reliable and has not left us sitting on the side of the road AT ALL.

Here's a list of things have worn out or failed. (This list doesn't include scheduled maintenance.)

  • When it was almost new one of the rear shocks started to leak, and was replaced free under warranty. Factory defect I suppose. Time to fix- 1 day at the dealer.
  • Once winter hit frigid temperatures caused the swaybar bushings to creak on large bumps, and required spraying with silicone lube every oil change to stop this (only during cold weather). This is a problem on most cars with hard suspension bushings. Time to fix - 5 minutes each oil change.
  • The motor mount bolt recall was performed (no problems before or after related to it). Time to fix - 1 day at the dealer.
  • At ~30,000 miles it had a code for an emissions system problem. An emissions system valve was recalled and was replaced free. Time to fix - 1 day at the dealer.
  • At ~70,000 miles The front brake pads and rotors were worn out and I replaced them with Wearever rotors and Hawk HPS brake pads. Time to fix- 1 hour (the front pad clips are difficult to figure out).
  • At ~70,000 miles a code for insufficient EGR flow was triggered. It went away after a few hours by itself (I checked the EGR pintle and it was not stuck, so I assume the tube is clogging up). I didn't clean the tube at this point. Time to attempt to fix- 0.5 hour.
  • At ~84,000 miles the same rear shock that was replaced at 10K miles is leaking again (no doubt thanks to the wonderful potholes here). This will be the first part I'll have to pay for out of my own pocket, which is impressive. I replaced both rear shocks (to be safe) with a pair of Mazda 5 van shocks (a tip from the forums, they have stiffer damping and cost less). Cost- $30 each ($60 total). Time to fix- 1.2 hours.
  • At ~90,000 miles I replaced the serpentine belt tensioner because it was making noise. The whole assembly was only $34 (very inexpensive for that part). Time to fix- 0.8 hour.
  • At ~100,000 miles I noticed the rubber part of the Mazdaspeed (AEM) air filter was starting to crack from dry-rotting. I removed it and installed the factory air filter system and contacted AEM about the warranty. They agreed to replace it, but I couldn't find the receipt for proof of purchase so I never sent it in.
  • At ~110,000 miles the car triggered a series of three codes that indicated a lean condition on bank 1, primary oxygen sensor signal stuck lean (B1S1), and a rich idle condition. The car would drive, but stalled frequently at idle. Research led me to check two things. First, those particular codes are known to be caused by a poorly designed aftermarket intake system. I found it comical that I had reinstalled the OEM intake only a few weeks earlier. I checked over my work to make sure I had not improperly installed it, but it was fine. Next was to check the signal on the primary oxygen sensor (which is an NTK wideband sensor from the factory). I checked the sensor using the MSD Dashhawk and it was showing erratic numbers. I ordered a replacement from RockAuto.com. The old sensor was very difficult to remove. I soaked it with a mixture of ATF and diesel fuel and it came out. The car ran well after the new sensor was installed. I should note that the normal life expectancy of an oxygen sensor is 100,000 miles, so the sensor was past due for replacement. Total cost for the NTK oxygen sensor- $110. Total time to diagnose/fix- 3 hours.
  • ~111,000 miles - Special note: I chose to reinstall the Mazdaspeed cold air intake system at this point because the dry-rotted filter base is not so bad yet that it posed a risk to the engine. I will replace it later and keep an eye on it at each oil change till then.

    I also did some other maintenance on the car, which included oil changes every 5K with 5W30 or 5W40 synthetic oil. As I mentioned above the air filter is a lifetime part, you just wash it when it gets dirty. This is a design feature of the Mazdaspeed Cold Air Intake kit (made by AEM) that comes with an AEM Dryflow air filter. Don't try to wash the stock flat panel filter, it's designed to be replaced when it gets dirty. Spark plug were changed every 50,000 with iridium tip plugs, and transmission fluid was changed at the same time as the plugs.

    The May 26th 2011 hail storm hit the car pretty hard, $6000 in damage, but the insurance covered it. New windshield, hood, and repainted roof. Since the car is so uncommon they have to use OEM parts to fix all of it fortunately. This was, of course, after they ordered all the wrong parts (for a normal Mazda 3) to make sure that they really won't fit (I TOLD them they wouldn't).

    Dyno Chart and Pictures

    3 runs shown are back to back with no changes. The differences are from the car gradually adjusting itself to the load of the dyno instead of the street, and from the engine warming up after the first run. This was done on our DC1800SZ dyno.

    Back when it was new and stock... I'll get some new pictures eventually.

    Pictures of the ported IC and coldpipe before and after.

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