This 1995 M Edition Miata came into the shop after living a long life with a supercharger. While the original motor had been running the supercharger for a long time, it was not using the most ideal methods to use the supercharger. During its time, the vehicle had either used the stock engine management system with aftermarket modules to help modify certain signals, or run that same stock EMS with the ignition timing set very conservatively.
While those methods of controlling fueling and timing to run a supercharger or turbo charger can work, they're usually not as safe or reliable. They also end up leaving potential performance and driveability on the table.
After discussing options with the owner, it was decided that instead of rebuilding the existing motor or replacing it with the exact same type of motor, that the car would receive a newer engine design from a 2000 Miata. This motor is similar to the original motor design in many ways, making it fairly straight forward to install. However, improved head and intake manifold designs mean the newer engine gives better horsepower and torque numbers across the power band. It can also make more power at lower boost levels when compared to the same supercharger setup on the original motor due to better flow characteristics.
Here is a list of existing modifications already installed on the car to work with this project:
Tubular Exhaust Header (Cobalt/Jackson Racing)
Header Back Exhaust (Jackson Racing)
Light Weight Aluminum Flywheel (Fidanza)
Upgraded Clutch Kit (ACT)
Boost Gauge
Wideband 02 Sensor, Gauge, and Controller (AEM)
Now is the time to do any maintenance to the engine or transmission. Before the new motor goes in, it will receive new front and rear seals, a new timing belt and water pump, a new thermostat, a new pcv valve, new colder spark plugs, plus any other gaskets or seals that seem necessary on inspection.
Below is a picture gallery of the project with notes for most of the pictures. Click on the first picture and follow along with the left and right arrows.
While those methods of controlling fueling and timing to run a supercharger or turbo charger can work, they're usually not as safe or reliable. They also end up leaving potential performance and driveability on the table.
After discussing options with the owner, it was decided that instead of rebuilding the existing motor or replacing it with the exact same type of motor, that the car would receive a newer engine design from a 2000 Miata. This motor is similar to the original motor design in many ways, making it fairly straight forward to install. However, improved head and intake manifold designs mean the newer engine gives better horsepower and torque numbers across the power band. It can also make more power at lower boost levels when compared to the same supercharger setup on the original motor due to better flow characteristics.
Here is a list of existing modifications already installed on the car to work with this project:
Tubular Exhaust Header (Cobalt/Jackson Racing)
Header Back Exhaust (Jackson Racing)
Light Weight Aluminum Flywheel (Fidanza)
Upgraded Clutch Kit (ACT)
Boost Gauge
Wideband 02 Sensor, Gauge, and Controller (AEM)
Now is the time to do any maintenance to the engine or transmission. Before the new motor goes in, it will receive new front and rear seals, a new timing belt and water pump, a new thermostat, a new pcv valve, new colder spark plugs, plus any other gaskets or seals that seem necessary on inspection.
Below is a picture gallery of the project with notes for most of the pictures. Click on the first picture and follow along with the left and right arrows.
Back from the Dyno
So, what were the results? Starting at the beginning, a new '94-'95 Miata made roughly 100 horsepower at the rear wheels, and roughly the same torque. A '99-'00 Miata made roughly 110 horsepower at the rear wheels and roughly the same torque. The newer motor design means it also makes that extra power every where.
Neither of these motors were new, so some power loss should be expected. Still, swapping in a better motor should yield 10-15hp before any other modifications. Once the programmable computer and supercharger are added, power can really begin to increase. The initial dyno pull after some road tuning showed around 133 rear wheel horsepower and 108 rear wheel torque. Not too shabby.
After more tuning on the dyno mostly focused on spark timing, these were the final results.
Neither of these motors were new, so some power loss should be expected. Still, swapping in a better motor should yield 10-15hp before any other modifications. Once the programmable computer and supercharger are added, power can really begin to increase. The initial dyno pull after some road tuning showed around 133 rear wheel horsepower and 108 rear wheel torque. Not too shabby.
After more tuning on the dyno mostly focused on spark timing, these were the final results.
The end results show right at 150 rear wheel horsepower and 133 rear wheel torque. Almost an exact 50% bump in horsepower and a substantial torque bump in a nice flat curve. While we don't have the original power numbers for the supercharger on the old engine, without the programmable computer, it's safe to say the power is much better. The vehicle owner claims the difference in how much power, and how the power, is delivered is definitely very noticeable.
The combination of performance parts, better factory parts, and a computer to run it all yields an older Miata that is peppy enough to keep up with many modern cars in a chassis that engages the driver more and makes it easier to enjoy the power available.
The combination of performance parts, better factory parts, and a computer to run it all yields an older Miata that is peppy enough to keep up with many modern cars in a chassis that engages the driver more and makes it easier to enjoy the power available.
