So I drove a Rotrex on Sunday at Buttonwillow...
 

..and I'm ashamed to say that it wasn't bad at all.

The setup:
'99 chassis, stripped/caged, ~2200lbs w/o driver, 6-speed, 3.909 Torsen
XIDA doubles, 15x9s, 225/45 NT-01s, Goodwin BBK
GTC-200 wing, custom endplates, front splitter

Rotrex blower
RC550s, Walbro 190lph, Adaptronic, E85, 230whp/212wtq@9.5psi (detuned from ~260 for stock longblock longevity)

This setup turned a 1:57.4, which is the 3rd fastest Miata at Buttonwillow, and the 2nd fastest car on NT-01s (Matt Andrews is 1st, my car is 3rd).

Throttle response was excellent, better than I am used to obviously. The car had a throttle body problem that made it a little sticky right as you cracked it open, but other than that it was really nice. No pre-application to spool a turbo like I do in my car - open the throttle and go.

Power delivery was, in a word, smooth. The best way to describe it is that it felt like the car had a straight 6 in it, very similar to my dad's E46 M3. No peaky rush, no thump of power, it was there right as you opened your foot and built smoothly to redline. I expected it to be a little peakier, a little more top-end oriented, and it didn't feel that way at all - just a nice strong pull from 5000rpm into the rev limiter. I was aware of the torque curve when I was driving it, so I consciously kept the revs as high as I could, but even then when the track required me to stay down a cog in order to avoid a shift in an awkward spot, I never felt like I was off the powerband.

To be honest, this is about as far as you can get from a turbo. There is NO rush of power, no drama, and it's almost hard to get excited about it, but there's something to be said about that. From a driveability standpoint, this is without a doubt more driveable than my car was, even with the T25, and it has the oomph, with 230whp from just 10psi. I got out thinking I had done a 59, and was very surprised to see the pair of mid 57s on the time sheet.

Anyway, thought I'd share my thoughts. It's a neat piece. Not neat enough to switch my track car over (I'm a fan of that big stupid rush of torque), but I could see owning a daily driver with one of these on it very easily.

so...after you finish sucking on your pacifier, add an EBC and then set it to make boost increase in a linear function to RPM.

Attachment 201649

Sav,

Do you ever feel like you've come to discuss Martin Luther King at a Klan rally?

How much better would this be for an all-out autocross car?

In my experience, pretty good. Instant throttle is easy to manage.

Although a big roots blower might be a little simpler to drive, as the "full torque everywhere, at any time" curve will eliminate any chance of being stuck between gears. On William's car (and my car) you usually have more torque than you can put down at 4K at autocross speeds, so the loud pedal is used to flatten the Rotrex' rising torque curve.

So your argument is that you can make a turbo mimic a Rotrex, and therefore the turbo is better even though it has worse throttle response... :hustler:

I'm not arguing that it's better or worse than a turbo - it's not. It's extremely different - the only comparison I can come up with is the 6-cylinder one. It feels like that.


I think it would be pretty good. I've autocrossed my 2871 and it's not fun - even the 2554 was a handfull. I could see it being pretty good for an autocross car - throttle response, instant torque on pedal application, no lump of power to deal with.

I've never had this "uncontrollable torque 'lump' terror" from a turbocharger which makes the car burst into flames and crash.

Why is this car so fast with no torque?!?!?! How??? Why????

My point is that for equal power, the Rotrex is easier to drive than a Turbo car is, just like a V6 is easier to drive than a turbo 4-cylinder. The turbo might make more torque down low, but the V6 makes the same power up top and is easier to drive. Different strokes for different folks.

I autocrossed my 2871R at ACS in August, and I would spend a lot of time bouncing off the rev limiter in 2nd gear. Someone asked me why I didn't just shift, and I had to explain that it would just spin the tires in 3rd too, and I was using the limiter in 2nd as a traction control device. :giggle:

I'd need to feel what the Throttle does, i really dunno what it's like. I just know I drive like that one the street DDing or in the rain, even autoxing, I only run full boost when I have a reason for it, car is much more manageable I agree.

Who is exiting the corner faster at "track-out"...the rotrex or the turbo car?

In for the answer to hustler's question...

Since you can throttle-rotate either car at track-out, they're the same. The Rotrex is just easier to control.

That's a solid, un-biased review from a well setup turbo. Thanks.

that's my car Andrew drove. when Andrew got out of the car, I could tell he thought he got beat (this was Miata Challenge, and he had to be sub 2 minutes to clinch the title). Car was not setup yet (just threw on the hard top, coilover few days prior, were chasing down some ground issue all day, didn't have time to dial the suspension nor aero), it had turn in understeer, exit oversteer, and high speed understeer. When Andrew found out he did a couple of mid 1:57s, jaw dropped. He didn't think it was any faster than his own car. I think the word he used was "deceptively fast"

if I had more time to dial the suspension in, fixed the aero, replace 2 flat spotted NT01, more seat time (he did 1:57 by 4th lap in black group). I am sure Andrew would of done a 1:55s.

dyno plotwars
 

lol. So true :facepalm:

Forget that the cars are stinking fast, stone reliable, fun and easy to drive. That's not the issue at hand. The issue is that they are not turbo's and don't produce a dyno plot like Braineacks.

Jeezuz, how many times have I seen that particular dyno plot? Like it proves once and for all that, um, actually I'm not sure what it proves because it seems he doesn't actually compete with his car. It also seems he has never driven a Rotrex powered car.

One might conclude that his often stated opinion must therefore be based entirely on what he has read in this and other forums. Not, as it might be assumed, on any empirical first hand knowledge. My dyno plots kicks your dyno plots ass!

:jerkit:

I just melted down my 6ULs in protest. I kept the FM lugs though, lol.

Please recycle! :makeout:

We need a special forum for members running under X-time on Y-track. Oh wait, thats track HQ. lulz

When do the TR 15x9s come out?

^Oh noes... :facepalm:

It was a lame joke, I know.

i kinda want one
don't understand the whole CARB EO thing
but i know i have to pass emissions

Since no one else has said it... I guess I will. What's the fun in that? Haha

Heaven forbid someone on this forum should cop an elitist attitude ;)

I'm just still waiting on a dyno of an all out setup. I want to see what the ceiling for this thing is already. I hate waiting for stuff btw...

Ceiling on what specifically? I suppose if we put a C38-94 on a fully built stroker on E85 we could make about 500whp.

TrackDayHookey is making 300whp with a stock head, built bottom end 94 engine, Racing Beat header and 2.375 street exhaust on 100 race gas, with a homebuilt C30-94 based system. He's planning a built head 99 engine, bigger exhaust, cams and possibly E85. I suspect he'll be making about 350whp then.

The OGK will use a system similar to William's car (that Sav drove) only with a big cam, full-on 99 race engine. I suspect I'll see around 310whp on the same C30-74 blower that our 165whp base kits come with.

In for chinarotrex...any idea when those will come out?

JK


I seriously should not be reading this thread. I really like Sav's review...and the plot is good enough for me.

:bowrofl:

Emilio, there's a thread on m.net where the FFS zombies are declaring MP62 superiority because "their" kit makes 190 whp. So I ask you, what's mechanically involved in bringing the base kit up a tad, to get it to the ~200 whp level?

I bet it's the same as a turbo - cool the intake charge, address the fueling, and be careful. Instead of a boost controller, you adjust boost on the Rotrex using an intake restrictor.

"Address the fueling and be careful" may as well be greek for the FFS folks, though.

I am the most modest and soft spoken person on the internet. I also only speak the truth.

Interesting, so mechanically, you simply use a less restrictive restrictor.
Intercooling is a great thing, but with the outlet temps, would it really be necessary at the ~200 whp level? If the MP62 can get away without charge cooling, I would expect the Rotrex to also get away without it.
Fueling is another story. There are times when I want to bash those morons' heads together.

Remember, a throttle body located fuel injector will bring your intake charge temps down from 300° to 100°. :jerkit:

Compressor outlet temps are 1800*.

3:30
Dramatic affect of cooling.

I think TDH put it best - I asked him forever ago what was under the hood of his Miata and he replied: "It's the yo-yo guy's blower."

Either making the engine more efficient with typical N/A mods like a header, porting etc. or more CFM from the Rotrex. The base Kraftwerks Rotrex is already set on "kill" as we like to say, meaning it's spun right up to it's max RPM then the top half of the boost line is capped with an inlet reducer. So it's the linear rise with a plateau wherever we choose. That means making moar boost is just a matter of using a different shape inlet reducer.

From the KW1, just add an I/C and pull maybe .75 AFR fuel, from around 11.0:1 average to maybe 11.75:1. That might be worth 15whp and essentially what we'll do for the KW2. Buy it from us without the ECU, and you have better control over the power delivery. Being able to run more timing down low and pull it back as boost builds.

The Rotrex runs cool enough to run 5psi non I/C without pulling timing. We find though that at about 7psi no I/C, you just have to add to much fuel to control knock in a stock Miata engine. It's just no longer efficient as you are dumping so much fuel in to douse things, even with the Rotrex. We could tune as aggressively as some of the MP62 kits, but we prefer a fail safe tune that will tolerate bad quality gas, dirty injectors, carbon fouled plugs that are hot spots etc. Wiliam has run as much as 9psi non-intercooled with stock timing during testing but that's a risky tune, similar to what you might see on some production MP62 kits with drastically reduced timing. I think we saw IAT's in the mid 200's when we did that. The base, KW1 kit on the NB runs between 170~190° post blower IAT's at full chat, back to back runs, fully heat soaked. One pull will see only like 145°. The crossover pipe sheds a surprising amount of heat and the manifold soaks some up so we see maybe 10-15° less at the plenum.

Unless you had a strong reason to do so, I personally wouldn't choose to build a non I/C kit for anything more than about 175whp. Adding an I/C is easy, its make more midrange torque and noticeably more top end without changing anything else at all.

FWIW, we have invited several owners of unmodified MP62 kits on stock engines to run their cars on our dyno, including a "190whp" kit. We will have stethoscopes and headphones.

The combination of factual data and satire in this thread is making my head spin.

On a serious note. I have like the possibiliy of the rotrex kit since you introduced it. My biggest gripe is the cost compared to other options. Make the price more competitive and I think you would see more widespread adoption.

Most of us want to go fast for cheap. I agree with neo: if/when the costs dip down on these bad boys you'll get a whole lot more customers

Yup. The Rotrex unit itself is expensive and the €:$ ain't helping.

FWIW, the NA8 KW1 base kits will incorporate a significant added value over what is currently available with the KW1 NB kits. Can't tell you anymore yet.

CARB = California Air Resources Board = Nothing to do with Georgia state emissions testing!

:drool:

I started the road to FI looking at superchargers and found the Rotrex. Once I saw the price per HP I started to wane a bit. I'm trying to keep a strict budget and so a used GT2554/60 kit is more in the works for me.

At the low 200whp range the Rotrex is going to be near 5K and thats way off my scale.
I doubt a used one is going to be hard to find right now also.

The current price is steep for a cheapie like me, not that it's anyones fault just like you said those blowers aren't cheap and currencies don't help. Perhaps as production and retail sales volume goes up they will start to drop in price.

Considering how easy to install and the right foot response, if there was a 200hp kit for $3K complete they'd sell like hot cakes.

Don't you have a deal where the 1st one sold in each Canadian province goes for 30% off?? There's only 13 of them so you would still have the shirt on your back once done with the great white north.

Thanks for the road report anyways it's nice to hear it from an experienced turbo guy on a turbo listing site giving it so much good press. It's certainly put me back to thinking about it but no matter how I do the math I think im still on the narrow dollar turbo path.

Perhaps our CDN dollar could jump 30 points next month............hmmm

Jesus Emilio, all I was suggesting is that his own personal turbo setup can be 'tuned' to provide the very same power output as the rotrex powered motor if he wanted to achieve the same effect. Those two consecutive plots above are of my motor, if you've seen that dyno plosted before, the text along with it probably said something like "you can achieve the same torque surve with a turbo setup...". I was not posting my dyno to say it was the best, and you will find many posts from me lately talking about how I have detuned my setup and removed parts to make it more enjoyable on the street... <---blasphemy


I even went as far as conceded that I have no experience in comparing the throttle response and that I agree the car is 'easier' to drive in that configuration.

But I can tell you all. firstgen kits will come with CF 15x9 6UL's (6ULC). How cool is that? Merry Christmas!

Brainey-balls, stop quibbling and don't speak in that tone to Emilio. I will come down there and we can throw down, nerd style.

Emilio, this is Will, you sent me a bunch of engine parts and a set of 9" nickel 6ULs within the last couple of weeks. We discussed my current/future setup of a built 1.8/00 head with my 2560R turbo for autocross use a few weeks ago.

I think what is being said about the throttle response of the Rotrex system has some serious merit for an autocross build. Even my car with the 1.6/2560R combo has enough inertial lag to make modulating with the throttle on a slalom or other transitional element a somewhat difficult prospect. My build for next year will help manage spool while still working with the 2560R, but the inertial lag is still a given within any turbocharged system, and will effect driveability especially in an autocross car.

I have no idea how going from ~225whp at around 14 psi with the old setup to probably around 280 whp is going to effect the balance of my car. I can tell you, however, that I used full boost pressure (14) at every late season autocross with very good results. This was with 225 NT-01s, open diff, great setup and corner weighting, and no rear bar. Spool qualities helped soften the torque delivery off slow speed corners (I didn't downshift often), I only had a problem managing tire spin on faster sweepers when I had target boost available. I am hoping that with the 275 A6s and the torsen (if I don't exceed it's capabilities), I will be able to manage rear grip even with more power.

If I had cash left over after my build, I would seriously consider the Rotrex. I think that managing torque delivery with the right pedal would be easier than relying on spool/lag to soften torque delivery.

Emilio, one last thing, would you care to divulge on here the "trick" ebc concept you suggested to me when we spoke about autocrossing a turbo car? I am not smart enough to implement it, but I'm sure :brain: or Joe could figure it out, if it's not been done on here before.

Will

Emilio, one last thing, and excuse my ignorance. You said the unit comes "set on kill" from the factory, and you use a restrictor to throttle it back. On a built engine, with efficient intercooling and good engine management, could the rotrex run uncapped? What would be the expected output?

Here's one:

[NA] DIY Rotrex Miata Challenge Build - MX-5 Miata Forum

Cliff notes: 303 whp/235wtq. On stock intake manifold and mild porting it did 280/220. Rods & pistons from Emilio.

With some more work (moderately worked over 99 head, new intake manifold designed for 99 head) I vote for Emilio's estimate of 350 whp:drool:

One of these days Emilio will have his super duper header available, which might open things up a bit more. Right now all that angry air has to go through a Racing Beat header and 2 3/8" exhaust.

I'm curious about how much throttle response and ease of driving are due more to tune than what kind of FI is used. Tune and boost control play a big part in how twitchy or smooth throttle response can be. While my car is a piss poor comparison to the extremes beind discussed here, it's set up with a nice fat torque curve and a very smooth throttle. It's perfect for a guy like me with limited skills. Very easy to drive.

There's no doubt the Rotrex is a good unit. The Vortech likely would be too. We don't need to get our panties in a bunch over them. Aren't they pretty much belt driven turbo's?!?

TDH-thanks. This may be subject to debate, but how much more than this 303-~350 range could even be close to usable in autocross, even on the 275 A6 and an OS Giken diff? I think this may be on the high end of the usable range, anyone else?

Also, TDH, do you have pics/specs of your intercooler setup? Last thing, what are your IATs at max boost?

http://threadbombing.com/data/media/2/orly_drive.gif

I also implement throttle based boost control-:brain:

Ninja bitch.

Implement into the Brain-built MS1 on my car? Is there a thread here that I can reference?

Edited to add: were you drunk when you wrote the original post?

I'm not an autoX guy, but yeah the power is more than you probably need to light the tires.

The intercooler is one from Track Dog Racing. Temps are about 40F above ambient under sustained load on the track. On dyno pulls it barely climbs at all, which can lead to optimistic fueling and timing settings in some cases ;)

subject change inc.

I never watched those FFS youtube videos and WTF? Thousands of dollars to go form 190 rwhp to 225 rwhp WTF WETF WWTETFTEFTEF BLAH BLAH. My $3000 dollar FMII setup (including the MSPnP) went from ~170rwhp to ~230rwhp for $150 dollar 550cc injectors, a turn of the the MBC, and a free self street tune :facepalm:

back on topic.

In for 94-97 rotrex kit for a decent price. I definately wouldn't mind running the kit for autox. A 280rwhp linear power curve miata with 275s could make a competitive ssm car.

I do not want to see what a Rotrex does on a low compression motor, no way.

TPS based boost control is no secret. Virtually all OEM turbos have some road speed or TPS parameter controlling the boost solenoid. To control it very precisely, you really need a full PID control but most DIY'ers do it with a PWM map. Basically running a boost solenoid like a fuel injector off a 2D map that is TPS x RPM = D/C (target boost value) or MAP x RPM = D/C. Dirt simple on a PWM map. Not so much with closed loop PID like the OEM's use. Still most guys I know that set up their own TPS based PWM boost control say "it's almost perfect, still messing with it."

It's handy on a turbo set up that will exhibit PTFB (Part Throttle Full Boost). PTFB is kinda fun on a street car where you barely touch the throttle and go blasting through traffic. On the track and autocross course, it's damned annoying since you are trying to control tire slip angle with torque, and it has a mind of it's own. More of an issue on the track where you want to fine tune slip angle on long constant radius turns.

William's car uses a simple Bosch recirculated BOV right off the production kits. The nice thing there is that you can go from say 80% TPS to 50% TPS mid turn and it just reduces torque smoothly, instead of venting everything and going to idle torque. I think TDH uses a VTA BOV so his torque may tend to fluctuate a bit more with small changes in TPS. I haven't driven it since he put the Rotrex in so I can't say for sure.

We run the Rotrex's uncorked all the time. TDH's DIY system is an unrestricted C30-94. Regarding peak output of the various Rotrex blowers, I've posted some estimates here and on m.net. Assuming a stock 99 engine, A/A intercooled, RB header, 2.5" race exhaust, standalone ECU with NB crank trigger and 100 race gas, these are my total WAG's of what an unrestricted Kraftwerks Rotrex geared for max blower speed at 7500 rpm might make. Not what they will make, just my personal guess based on what I have seen on the dyno. The theoretical car above basically describes William's car except he runs E85.

C15-60 200~220whp
C30-74 285~310whp
C30-94 300~340whp
C38-81 360~420whp

Add a big valve, big cam, race ported head, stroker, 12 tooth crank trigger, quad EGT's, sequential fuel and ignition, E85, 949Racing Big Tube header, 70mm exhaust, custom intake manifold and 65~70mm throttle body: I'd guess you could add maybe 15-20% more power.

The Honda guys with K24's are making well over 500whp on race gas with the C38's.

C15 series technical data
C30 series technical data
C38 series technical data
FWIW, every race shop using these blowers is making way more whp than Rotrex's estimates. Cruise youtube or google for dyno's on everything from Farm Quads to Twin Rotrex F430's.

William's is a stock 9.5:1 bottom end, TDH's is 8.7:1 IIRC. Actually, any purpose built motor Kraftwerks puts together for a Rotrex and road course use has lots of compression. The OGK's will be 11.0:1.

With all the drama Savingaids and I have been through on the road to track reliability, it takes a special kind of moron to overlook this supercharger.

I'm sure he's on here somewhere, with a few friends ;)

As to Emilio's BOV discussion, I am running a ebay Greddy knockoff set up to recirculate. I played with springs and the adjuster and it seems to work okay. Completely dropping the throttle at redline drops the pre-IC boost from about 19 psi to 12 or so which drops quickly as the revs drop.

The BOV on a blower gets a real workout. As long as the revs are there, that 300 hp of flow keeps flowing. Pushing that through the 30-ish mm hole in the BOV makes some cool noises - not the single chirp of a turbo car, but a continuous turkey gobble sort of sound. The next time I dig into the plumbing I'm planning on a 50mm BOV to try and reduce the no flow pressure.

So your saying that with the c30-74 rotrex, my MS, 2.5" exhaust, a good flowing header, ported 99-00 head, 94 block OE pistons w/ crower I-beam rods, big enough injectors and 100 octane race gas that I could see ~300rwhp and be pretty damn reliable? Sign me the fuck up.

I didn't know hardly anything at about the Rotrex S/C until this thread. I usually saw the word supercharger and scrolled down to left the thread hah.

Whats the power expectancy with the said setup but on 93 pump gas? (street cars)

Any benefits to having a ITB type intake manifold with the Rotrex?

A few things:

• An efficient I/C, probably at least 10lbs worth.
• Crank triggered ignition. NB 2 tooth at minimum but I'd recommend at least 4 teeth.
• Cold air induction. Sticking the air filter next to the header will cost you too much power
• Some intake manifold modifications. The USDM 99-00 or 01-05 are both going to make 300whp difficult. The non-USDM 01-05 1.8 manifolds are better, or you can modify the USDM. TDH made his own from scratch and it's probably worth about 8% more power on his engine.

Don't bother with ITB's unless you're going with really big cams, sequential fuel and ignition.

+1

I like the idea of the easy install and reliability for a daily driver. As mentioned however, as a Miata owner (cheap cars) I want the best bang for my buck (pardon the cliche). $3,295 for 5psi with the slight possibility of 7psi just doesn't meat the criteria.

Possibility of 16psi actually. Just remove the restrictor. Same blower.