Flyin' Miata : Dissecting the Mazdaspeed MX-5

A digression about testing the Mazdaspeeds. It's tough. On a stock car, we saw it lose 15 hp and 17 lb/ft over 8 minutes. There were absolutely no changes to the car. How? Heat buildup despite our huge fans. It was pulled in from outside with a chilled IC and cold engine bay. We have also seen differences in spoolup between different stock cars. As you can imagine, it's quite difficult to come up with representative dyno runs particularly when the cars are in a near-stock configuration. We do our best based on our growing library of dyno runs from which to compare, choosing runs that are typically the second or third after a modification as that allows temperatures to stabilise and the ECU to understand what's happening.

The previous testing that we did on one car has since shown to be full of errors. The car suffered from terrible spoolup for some reason and responded quite differently to modifications than other tests. We have some theories as to why but nothing solid. This is the downside to testing other cars, particularly under time pressures. Those tests are effectively useless despite our attempts to pull some meaningful information from them. We honestly cannot explain some of the behaviour. Due to their confusing nature the reports on this car have been taken down from our site. Conspiracy theorists will undoubtedly come up with their own explanations, but it's that simple.

What brought it to our attention was installing the intercooler, exhaust and downpipe on our own car. Since we now have thousands of miles of experience with the car in stock form, the increase was immediately obvious. Back on the dyno, our initial impressions were confirmed. The exhaust/downpipe combination along with the intercooler makes a much greater contribution than we had thought. How much more? See the dyno charts.

We have also installed a Hydra engine computer on our car. We are still in the process of tuning it although the intial installation is very promising in terms of driveability. On the dyno it is making the same horsepower as the stock ECU but at a massive 2.6 psi of boost near redline - the stock boost control solenoid isn't being controlled so it's running off the mechanical wastegate. Once we put some pressure in the intake manifold things should perk up considerably.

Other developments have been in the suspension arena. Our car has been fitted with truly massive rubber (well, massive for a Miata) in the anticipation of much horsepower. More details will be revealed in the future. For those who wonder why development has been so slow on these cars, it's because we've been shorthanded and simply haven't had time to examine our own Mazdaspeed until recently.

As always, all charts show the same car before/after unless otherwise specified.

Stock vs. FM exhaust/downpipe/intercooler
Blue line is modified, red line is stock. The car was fitted with our upgraded intercooler, downpipe and exhaust system. The boost was untouched. The car now makes as much torque at 3600 rpm as it used to at 4700 - and then keeps going. The boost rise is not as abrubt and the car is far more driveable on the street. Honestly, if the car had come like this from Mazda it's likely that we would be receiving far fewer phone calls.

Heatsoak
Two 40 hp fans. A 20,000+ cfm fan that sits 5 feet tall. A small fan aimed right in the nose. Even with all of these running at once, here's what back-to-back dyno pulls will do to a stock Mazdaspeed. The first and sixth runs were 8 minutes apart. The unusually high run 1 was due to an intercooler that was chilled to sub-freezing temperatures. On the street, it's likely that the intercooler will heatsoak after a single pull through the gears.

Same peak, different cars
Here's why it's a bad idea to simply look at the peak numbers on a dyno run. These two cars make almost identical peaks but they would be radically different to drive. The intent is not to compare what made these cars act this way, they're just an example.