James had us install the Jackson Racing supercharger kit on his BRZ last summer, and now he’s gone for more power and the upgrade to the C38 supercharger that Jackson just released. I had the unique opportunity to do a nice comparison between both units on the standard “low boost” pulley before upgrading the C38 blower to the “high boost” pulley.
This test was done on 92 octane fuel. Our dyno baselines a stock FT86 at 148-150whp (not the typical 170 you see elsewhere).
So after swapping over the C38 blower onto the car, dropping in the 900cc port injectors (you’re going to need an upgraded port injector for the high boost pulley), this is what we got. Solid lines are the C38 blower w/ the standard pulley, dashed lines are the C30 blower w/ the standard pulley.
The results were exactly as expected — the low end was basically a wash (slightly lower with the C38 blower — it made the same or a little less pressure ratio, aka “boost”), but the efficiency of the C38 compressor started to shine on the top end, and we had a decent power pick up on the top end over the C30 blower.
On goes the high boost pulley. Internet experts quiver in fear as we swap on this pulley. The world is going to come to a grinding halt with the uber boost levels this pulley makes and is apparently going to make it impossible to run the motor safely at such “extreme” boost levels. Imminent danger to manifold — obviously.
Well I’m going to have to let the experts down on this one… but this “high boost” pulley is perfectly safe to run on pump gas (91, 92 or 93 octane). We actually picked up a solid amount of power through basically the whole curve — as much as 25whp over the low boost pulley @ 7000 rpm — making just shy of 290whp. And yes, it’s perfectly safe to drive. You don’t “need” a built motor to run this power level — or E85 to make it “safe” (but we’ll get to that later..).
And to compare it to stock….. lots more power everywhere. So what do I think? I think our Internet Experts need to do less “blah blah” on their keyboards, and more work in the shop. And I think if you’re looking for a centrifugal setup, this is the way to go — the nice C38 blower with the high boost pulley. I would just skip the standard “low boost” pulley. There is nothing “scary” about this power level and it’s not particularly hard to tune it to be reliable in the hands of a competent tuner — our 290hp is 1.9x more power over a stock FT86, so on a higher reading dyno that baselines an FT86 in the ~170 area, you should be seeing 320hp, or so.
And the info graphic on the boost levels with the blowers. Blue graph is the C30 blower with the standard pulley. Orange is the C38 blower with the standard pulley. Grey is the C38 blower with the high boost pulley.
Now the awaited E85 update… or in this case, E65 as I only got 10 gallons of E85 into the tank, and it blended with the remaining ~3 gallons of 92 octane. The results are fantastic — the car makes 2.3 times more power than stock, and well over 200whp more than stock at rev limit. The graph to the right are the gains over 92 octane. Graph to the left are the gains over a stock FR-S/BRZ.
With the extra 20% ethanol a full E85 blend would bring, we’d probably pick up another 6-10hp on our dyno. On the more high in the clouds style dynos, this setup is “400hp” 😉