Flyin' Miata : M45 vs Voodoo II

Janel came to us with a 1990 fitted with a Jackson Racing M45 supercharger and a big boost kit. The car was quick, but despite a lot of fiddling it never reached a consistent idle and would still stall once in a while - usually when she was coming up to the line of an autocross, to her mortification. The exhaust note was edgy and a lot of vibration came through the car. On the dyno, each consecutive run saw a 5-8 hp drop due to heat problems. She did enjoy the sound of the supercharger, and when we proposed installing one of our Voodoo turbo systems she wasn't convinced.

So we went ahead with the work, knowing that we could always reinstall the supercharger if the turbo transplant wasn't a success. We chose the small 2554 turbo given the 1.6 engine and the relatively low-boost application. We left her naturally aspirated dual exhaust and Jackson Racing catalytic converter on the car along with an MSD boost retard.

When we were done, the car was transformed. It immediately settled into a solid 850 rpm idle and no amount of monkeying around with the accelerator or the A/C could upset it. On the road, the car felt much smoother and the raspy exhaust note had settled into a nice even purr. Best of all was the performance - the car gained nearly 25 hp and over 20 lb-ft of torque. Run after run, it put down consistent numbers without fading.

There was a loss of a bit of torque between 2500 and 3200 rpm, but the large gains everywhere else overwhelm this. Had the testing been done at sea level, it's possible the faster spoolup of the turbo would make up the difference.

We could have used a Voodoo I turbo to achieve the same improvement in driveability with a little less power gain, but Janel saw how the power dropped on the non-intercooled supercharger so she decided to go for the intercooler. She doesn't miss the supercharger whine one bit now that she's felt the new performance - better than a stock 2005 Mazdaspeed MX-5 turbo! When the header is taken into account, the supercharger and turbocharger systems were almost identical in price.

Dyno chart

The dyno chart is uncorrected, unlike our usual charts. This is because the car's performance is limited by the size of the stock injectors.