Landrew

iTrader: (2)

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

Braineack

iTrader: (62)

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.

TurboTim

iTrader: (9)

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

webby459

iTrader: (8)

Brainey-*****, 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 or Joe could figure it out, if it's not been done on here before.

Will

webby459

iTrader: (8)

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?

TrackDayHookey

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

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.

cueball1

iTrader: (13)

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 **** 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?!?

webby459

iTrader: (8)

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?

Braineack

iTrader: (62)

webby459

iTrader: (8)

I also implement throttle based boost control-

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?

TrackDayHookey

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

flier129

iTrader: (7)

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

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.

hustler

iTrader: (6)

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

emilio700

iTrader: (3)

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.

hustler

iTrader: (6)

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.

TrackDayHookey

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.

flier129

iTrader: (7)

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 **** 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?

emilio700

iTrader: (3)

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.

ecko

iTrader: (1)

+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.

emilio700

iTrader: (3)

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