Superchargers? Okay.
The JR SC was designed to be simple to install. The blower used (an Eaton M45) was small and sized to feed a 1.6 at 6 psi. At this level, it was actually pretty close to the edge of the efficiency envelope. As the engines got bigger and the heads got better, the poor blower had a harder and harder time moving enough air. Intake temps went through the roof and it got to the point where an 8 psi pulley really didn't make any difference. The Roots blower isn't terribly efficient at the best of times - on a 6 psi 1.6, the intake temperature is often above the boiling point of water! To make things worse, it's mounted on the exhaust side of the engine. I think the Honda ones are on a custom intake manifold, no?
True story - we had a car delivered to FM that was going to have the JR SC removed and one of our turbo systems installed. That's a surprisingly common thing. One of our employees took the car out for a short run. When she got back, we asked her if the owner had removed the SC before he shipped the car to us. She couldn't tell - we had to go pop the hood. Yup, it was still there...
You can upgrade a JR SC with air/water intercoolers, water injection, internal modifications and smaller pulleys. But by the time you've extracted everything you can, you're still way behind. Keep reading for proof.
Our own SC uses a 1.2l Whipple twin screw. Not only is this blower inherently more efficient than a Roots, but it's sized to provide huge amounts of power if needed - over 300 rwhp. It's mounted on a custom intake manifold with an air/air intercooler for low intake temps that are only just above ambient. Our setup is still in the final stages of development, but we've got some beginning dyno runs. There's a whole lot more power left to unlock.
Proof?
Dyno chart 1.
The red lines are a 1.8l Miata with a JR SC. It's got all the bells, whistles and magic boxes on it. We're unsure as to whether it was running 6 or 8 psi - nobody remembers.
The green lines are the same car on the fourth run. The fluid for the air/water intercooler has heat-soaked.
The blue is one of our prototype cars. It's the same model year of car with no other mods other than our SC setup and a similar exhaust to the other car. There's certainly more power to be found in tuning (it was running much too rich) and we have to figure why it's falling off at the top end, but I think you get the idea. With the air/air, there is no heatsoak. The price of the system is about the same as the investment in the JR SC at this point.
Dyno chart 2.
There's that same JR SC on the blue lines.
The red lines? Same car with an FM II turbo bolted on along with a turbo exhaust. No headwork, no internal changes, just bolt it up and go. Again, the price of the system is similar to the JR SC we took off.
More info on the FM bercharger can be found
on our website
Keith
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