211whp on 6.7psi
 

Cross posted from this thread on m.net.. CoralDoc's Kraftwerks C15-60 (baby Rotrex) DIY kit. 99 engine, MS PnP, TDR I/C, 420 RX8 injectors, 43.5psi (NA6) 93 pump gas

211whp on pump gas, 6.7psi running 28° timing. Not bad for a blower the size of a grapefruit.

That spark map looks like something from an N/A motor with the MAP scale inverted. That tuners can run that much timing, that lean on pump gas with these is a real paradigm shift. It matches what we have seen here. I'm starting to see more and more intercooled Rotrex tunes that have timing optimized for MBT at every MAP/RPM without being past detonation threshold.

On paper at least, the Rotrex should only be a tiny bit better in det resistance than a turbo flowing similar CFM & pressure differential. In practice however, we keep leaning them out, adding timing, making more power and they don't knock. Other S/C options aren't even in the same league. More CFM, less boost = Win.

I see this as due to two main factors:

- Exhaust back pressure. While a turbo and Rotrex compressor may have identical compressor maps, one is pushing against the exhaust back pressure created by the turbine where the other does not. The turbo blocking the exhaust flow raises the boost level relative to a Rotrex, which means greater heating of the air mass. The turbo then requires more fuel mass, less timing to control detonation. I think disrupted exhaust scavenging with turbos using stock n/a cams also contributes to lower charge efficiency and mixture burning.

- Compressor housing heat. The water cooled CHRA of a modern turbo does an excellent job of insulating the compressor from the 1200° heat just 2" away but you still have several hundred degree compressor housing temps. In contrast, Rotrex housings run 110~130° on a street car and transients not much past 160° even in race conditions.

Even after all this time, the marvelous efficiency is still fun to look at

Edited 12/27/2010
My rough calcs for BSFC (Brake Specific Fuel Consumption)
196whp @ 6000rpm torque peak +
26 drivetrain losses
222bhp

420cc @ 43.5psi (40 lbs/hr) 195500-4450 Denso RX8 injectors x 4 cylinders
65% DC at 6000RPM torque peak.
120 lbs/hr

104/222 = .47 BSFC roughly - Torque peak

137.6/237bhp roughly .58 BSFC - Power peak

I know my calcs are not dead on but even allowing for some fudge factor.. that's amazing.

That buttery smooth and linear torque curve is familiar. So easy to drive fast at the limit of traction.

Inline linked the images so we can see them clearer

http://forum.miata.net/vb/attachment...7&d=1293329663
http://forum.miata.net/vb/attachment...3&d=1293367919
http://forum.miata.net/vb/attachment...7&d=1293379388

35% for drivetrain loss seems steep. Has this number been backed up with hard data? I could use this info to easily make a clutch decision.

Back on topic: Are there any setups that are ready to push 300+ HP. If so, would this be a more reliable alternative to some of the proven track setups by members on this site?

35hp, not 35% and yes that numbers is widely accepted.

Not sure what you are asking for "setups ready to push 300whp". We don't offer a 300whp in a box if that's what you mean.There is at least one Miata I know of making a conservatively tuned 400+ whp on race gas with a big C38 series blower. The only complete Kraftwerks kit available now is a non-intercooled C30-74 kit making about 160whp for the NB. C15-60 based intercooled kits making around the same power for the NA are just around the corner.

For power levels above that, we offer DIY kits for the C15 and C30 series. It's up to you to plan, build and tune though. We just supply the blower, brackets and drive system. You supply all intake plumbing and fuel management.

what motor is this on?

Edited OP but you could have followed the link you lazy bum.

:) figured since you said it was a cross thread you started teh same post over there... my bad. Congrats!

This is what I was asking. I wanted to know if there was a rotrex style charger that could support more than that I have seen advertised.

I'll check it out on your site.

Edit: After looking at the diy kits; If you have an intercooler and engine management. What are the downsides to this? One diy kit supports 400Hp. What do the dyno plots look like for the large supercharger. (built engine of course)

That is a ton of timing (almost double what most of us run), but pretty impressive nonetheless.

DIY kits don't have dyno plots as they are just a blower and drive system. You have to plan and build the rest of the installation. We don't provide step by step instructions for that part. At the big end, assuming a BP series block with BP4W/BP6D head, unlimited budget and a C30-94 DIY based kit, maybe 470whp running E100 on a built 2.0L.

Being a belt driven centrifugal S/C, boost will generally rise linearly with RPM. So the shape of the plot here is fairly typical. In short, I can't give you a few sentence answer to the basic question you have. You'll have to do more research to begin planning your build.

Tech specs on the C30 series Rotrex

Fixed;)

I am betting it's the former vs. the latter. Going from my stock 8.8:1 '94 motor to the 9.5:1 BP4W motor, I was able to add in two degrees of timing straight across the torque peak despite the higher compression - exhaust flow is huge for timing. Hustler proved this again with the .86 A/R housings - huge timing numbers from unrestricting the exhaust and dropping the compression a little.

Compressor heat MIGHT effect the efficiency a bit, but I don't think it has anything to do with our ability to run timing. 110*F in the manifold is 110*F in the manifold no matter what puts the air there.

I'm surprised the tuner didn't catch the timing drop at high RPM - as soon as the MAP goes over 140 you can watch the timing tank in the datalog, down to probably ~25 degrees at ~7k and 148kpa. If Josh is tuned for MBT he's probably only giving up a horsepower or two, but if he's got it dialed it back from MBT for safety then he may be giving up more.

211 at 150kpa is huge power for the boost, though. Big flow at low pressure is something you just can't achieve without a BIG turbo.

Digging through some old notes and I think I have the estimated drivetrain loss value wrong. Should be 26hp. Not sure where I got 35hp from, sorry.

That would bump the BSFC at Torque peak to .54 and about .58 at power peak. Still good :)

Those are solid numbers. The interpolation on the top is really hurting 6000rpm+ output; if you've got the piston speed, use the spark angle. I don't understand the logic in running more spark at 4000rpm than 7000rpm...unless he's at MBT. I'd like to know where MBT is on this tune, and how far out that spark table is in terms of safety.

I found that in the cruise cells it pays off to run less spark angle after hearing some phantom-detonation with the Polish det-cans and I'm still getting 32-34mpg on cruise, 26mpg on 85-90mph with the 400lb trailer. I also so a large jump in torque by pulling spark and leaning out 3000-4500rpm cells, but I have a different animal of couse. Mustang Dyno = love

Agreed. I think all the difference is lack of exhaust back pressure. After thinking about it a bit, the difference in IAT due to compressor housing temp would be infinitesimal.

I wondered about the timing on top too. Maybe the tuner got nervous seeing 85% DC and dump timing for safety? Hopefully the Dr will chime in.

Thinking about it again, the exhaust backpressure has something to do with it, but I think it also might just be the simple fact that you guys are adding boost with RPM, and RPM is a detonation deterrent. Even on my 2554R I was able to find MBT at 11-12psi above 6000rpm. The same high boost/cylinder pressures that produce big torque at 4000rpm also make it more prone to detonation for obvious reasons.

Very nice numbers!

Emilio, I'm curious about the ideal CR with the rotrex. I remember reading somewhere that you were going to run 11:1 on the OGK.

I've got a 99 head w/ an 01 block and was wondering if I could see similar results on a c30-74. Or is the c15-60 recommended for stock internals?

He's probably going to run corn through it.

The more compression you throw at it, the more torque you make for a given boost level. No "ideal" CR, just whatever will work with the rest of your system.

Match blower size to hp goals. What power are you trying to make with the hybrid motor?

Planned for race gas. No corn nearby unfortunately.

Oh I see.

I'd like to see 230-250 rwhp. Running a MS3 and a DIY FMIC. Wondering if the motor will benefit from sequential fuel and ignition at those power lvls.

c30-74

Thanks for the in-depth analysis of my report. I keep learning from listening to all you guys.

At 6k RPM (torque peak), duty cycle is 65% and manifold pressure is 133kPa. DC doesn't hit 75% until 6670 RPM, 140kPa.

I didn't even know what MBT was until seeing comments in this thread, and the other on Miata.net, but we did tune for max power at various engine speeds. We spent most of our time tuning at full throttle, and I will be sure to hit more part-throttle cells during the next tuning session. Having never tuned a Rotrex supercharged car before, the tuner was a bit apprehensive about being so aggressive with spark. After some encouragement, he added spark until power started to level off, then we scaled it back by a couple of degrees. He left the 160kPa cells with less advance at high RPM as a safety factor. I suspect we could add some timing back in up there for a little more at the top end.

It's reassuring that others with Rotrex superchargers have been able to be this aggressive with spark without knock. We did not hear any knock at any time, and careful inspection of the spark plugs did not reveal anything of concern.

Hasn't stopped me. ;)

You need it though. Otherwise things in go pop that aren't supposed to.

I don't think I'll need it... 2.0L big valve fully ported, .430 lift, ceramic coated everything, internals safe to 8500, 949 header, 2.75" exhaust, square top, sequential ignition COPs, 12T crank trigger and a C30-74. It'll probably make 320whp on a strong cup of coffee. I think that's sufficient to accomplish the goals I have in the OGK.

Thats pretty impressive.

When is the KW3 setup coming out? I'm looking to make around 190 - 210 whp on a stock 99 engine. Any pricing ideas?

Not sure what base intercooled NB kit will be called but it should make about 185whp on pump gas right out of the box. That is the limit of the stock injectors/fuel pressure.

If you choose to remove the restrictor, add bigger injectors and a programmable ECU to control it, a stock 99 engine with header, high flow cat and exhaust would probably make around 260~280whp with the upcoming intercooled NB kit.

Sorry I didn't specify, I am in a racing series where there is a limitation on power. No problem on buying bigger injectors or a standalone. Also, don't want to make too much power because as referenced in another thread, i'd rather have a 2000hr motor than a 20hr motor :). What I'd like to avoid is buying additional parts I don't need like exhaust, etc..

Also, is there any way to change the power curve of a supercharged setup? I.e., get max power of 190whp at 4500rpm, and maintain that power level all the way to redline (therefore, the torque would be decreasing after 4500rpm) ?

Finally, any idea of dates? I'm not a diy'er so a plug and play setup like what flyin miata sells is very attractive (ecu already tuned). I need to know what route I'm going to go for in the 2011 season depending on when your product is released (and whether or not it will be plug and play).

Just duplicate CoralDoc's C15-60 setup. It won't be a complete kit though.
We'll have intercoolers for all years shortly.

You can probably get something like that with a bov made to open at the specific psi you want. In other words the oversized SC would make lots of boost and the bov would open up to vent the extra so it doesnt overboost over your target. Centrifugal scs, not twin screws...

You would need to run an external wastegate on your charge piping. Size the blower to run to it's max RPM at your redline. Don't use a restrictor. Use a larger Rotrex, and then set your boost target with the wastegate. Re-route it into your intake if you want.

The problem is that the needed dropping torque at RPM > 4500 means the boost needs to be dropping too. An intake restrictor tends to be closer to a power limiter.

EBC and drop the boost target to suit? This would be very attractive for a NASA TT car. Hit your WHP limit low and ride it to redline.

I suppose that's possible if the blowoff valve is chosen so that its flow is infinitely adjustable.

One could also use a DBW throttle butterfly in the compressor inlet to modulate flow and thus output power.

Hi Emilio, I have a couple questions for you. I have a full Borla exhaust with the stock exhaust header, an EMS Hydra, 440cc injectors, high volume fuel rail, MAP sensor and a home made cold air intake with basically no restrictions (K&N air filter, no maf). I also have the mazdaspeed motor and diff mounts, two wideband O2 sensors (one for the hydra one to a seperate a/f guage). Looking at the rotrex setup it looks like it would be easy to run intake piping from my cold air box to the Rotrex intake which I like.

My questions are these; I want a stock like torque curve ( close at least) and roughly double my stock 108rwhp, more is good. Which blower would you suggest, the 15-60 or the 30-74? Is 210hp the max for the 15-60? My engine is a stock '01 (other than what I've listed and an aluminum rad, m-tuned coolant reroute and an oil cooler/filter relocate). At what point do you need an intercooler with the rotrex and does the throttle reponse suffer with an a/a intercooler

Sorry, it's a long post.

Jim

jimj64,

C15-60 run at full speed w/o restrictor.

What boost level should I expect to see and is 210hp the upper limit? I'm curious about the limit of the C15-60 in terms of future power increases, although I'm not planning any, you never know. Thanks for the quick reply.

BTW, I do not expect anyone to say "210 is exactly what you'll get" I know there are a million and one variables and no exact answers.

Jim

Maybe 8psi. Honestly, I don't get too wrapped up in boost numbers. Sorta like tire pressures. Just a number and not a measure of power (or grip).

C15-60 will be topped out at 210-230whp. C30 will top out 280-320whp.

I have to agree, but it is a useful tool for comparison and guaging other things like intercooling. Kind of like dyno's, useful and meaningful tool if used and interpreted correctly, but not the be all end all of how useful the power your making is.

Do you have an idea of what rpm the 15-60 will start making "usable" boost at? The term usable is left to interpretation.

Jim

http://www.rotrex.com/Renderers/Show...Range_V4.0.pdf

http://www.rotrex.com/Renderers/Show...Range_V4.0.pdf

What about the c30-64?

No experience with it. Oscar never uses it. No real benefit over the C30-74.

I know I sub'd this thread for a reason!

Emilio: Assuming I'm running a stand-alone and bigger injectors, what else is required to go from the no-management C30-74 165whp kit you sell on your site, to something like 200-225whp? Just a pulley, restrictor & re-tune? At what point is an intercooler required with a rotrex?

I've seen the dyno sheet you have posted on your site for the 01 w/-74 base kit, any chance you have one that includes MAP data?

My car is a do-it-all machine right now (DD, AX, HPDE) and I'm wondering what the long term effects on the blower longevity would be from my 15 min one-way twice daily commute. I've read that these units are really picky about there internal oil temp. Any comments?

Thanks!

Your questions are too generalized for concise answers.
To simplify, figure out an I/C, ECU and take it to a dyno.

No other dynos.
The Rotrex is about as bombproof a blower as you'll find. They're picky about oil temp just like your engine is. IOW, run it it dry and it will blow up eventually.

Thanks Emilio for the response. My 2000 is running a BP5A cam, square-top and an 01 header on a factory ecu. Will the 'SuperCard' be able to hang with that? Wideband will be installed to keep an eye on things regardless. The plan was to go simple with the non-intercooled "165" to start, and move up in the future once I go MS2. Obviously a restrictor change will be in order, but no change in pulley? Damn the rotrex is cool, I spent WAY too much time reading about roots systems.

Also, thanks for answering sc q's for n00bs on a turbo forum. :bigtu: I'll probably give you a call next week to place an order.

Supercard = stock engine
 

I keep getting asked this same question so I'll try to make it clear as possible here:

The Supercard that comes with the Kraftwerks base kits only works with 100% stock engines (zero modifications). Modify anything and you need to research and ECU solution and bigger injectors.

Understood. Thanks again!