Jmays2k

^^^^ Thank you for your honest reply, and as far as power our goals are pretty close Im not shooting for 500 either but I probably will be running e85 because I can get it down the street. I have been looking at everything I can do to help with the mid range because that is what im worried about the most.

SlowTeg

My post largely shares Junky's thought process, no offense intended. Is a rotrex really that much more efficient than a paxton? I've seen people claim that rotrex's are more efficient but the question is really if it's considerable. I'm curious where the extra midrange comes from specifically as I'm interested in a FI setup down the road for road racing. I guess the question is ultimately whether the difference is negligible between the SOS SC kit and a rotrex kit (it seems like it is), but I guess we'll see over time.

2K_S2000

Sorry for the newbie question but is this kit (or any others) emissions legal? Locally, there is no sniffer test but they will check OBDII for fault codes.

Appreciate your feedback.

Best regards!

vector01_hungry

the old KW kit doesn't produce any fault codes for a scanner to pick up. I've passed inspection at least twice with mine.

s2000442

It all depends on your ems. Kpro or flashpro will pass obd2. Aem, haltech etc will fail.

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s2000Junky

I haven’t seen any data comparisons on mid range performance from a c38 compared to a paxton 1200, there may not be, could just be theory. But if you were to base it on a comparison between the c30 Rotrex the old KW kit used and the old Paxton 1000 Comptech used, the difference in Mid range power typically was worth about 1 psi, and since the KW capped out sooner, it wasn’t a problem to offset the performance over the entire power curve with the 1000 at higher boost. We can only deduct from that what the c38 to 1200 might be.

But like anything, bigger blower = more parasitic loss and the added efficiency of either of our comparable blowers may not make up and exceed that loss in heighten power, at a low/mid rpm range you all are after. The c38 could be worse then the c30 in the mid and provide no benefit over the paxton 1200 given a particular boost level, or it could. Matching boost levels is important when making comparisons on the same motor.

But I think if your coming from a mid range monster like the SOS turbo kit Rainh8r just did, any marginal level of mid range the c38 might provide over the 1200 wont be appreciated or possibly even perceived. You have to look at the total package of what the centrifugal kit is providing, which is top end power efficiency, and that’s where you want your engine to be efficient, which ours are. If the rotrex cant deliver up top, I think it will disappoint. If all you are after is sub 400whp with real mid range power, I think a roots style SC is the answer.

I still want to know what the max CFM from the c38 is, to the Paxton 1200 for comparable top end potential.

RAIN H8R

The data can be found on the rotrex Web page under technical data. I cannot link it as it is a pdf.

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Jmays2k

For the c38-81 the CFM looks to be 1004.44? is that right? and 1150 for the novi 1200

SlowTeg

Oh for sure. I understand the power difference of the SOS turbo vs. SOS supercharger midrange is night and day, and ultimately a roots style blower is THE answer for any road race setup, but the big problem there is that no one makes a kit anymore. There should be a few local SC'd s2ks at the track next year and I'll have to go for a ride along. I hope the KW kit turns out to be a good performer, as the sound of the rotrex over the paxton is a selling point itself.

s2000Junky

That’s a significant difference. Id say about 50hp. The midrange efficiency of the rotrex would have to be pretty significant to even match, let alone offset anything the 1200 could provide at its peak efficiency. I'm thinking it’s the same song and dance between the c30 and old paxton blowers. If you’re not going to run the 1200 at full rpm then the c38 may show an advantage in mid range, how much remains to be seen.