Corten-Miller Rotrex kit (for NC Miata) preliminary results are out! - Miata Turbo Forum - Boost cars, acquire cats.

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Old 02-11-2014, 01:50 AM   #1
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Default Corten-Miller Rotrex kit (for NC Miata) preliminary results are out!

I've been waiting for a Rotrex kit for my '13 Miata Club for about 3-4 months now, and it seems results from at least one of the kits is out. I am looking for an FI solution which would be most reliable at the track, and Rotrex kits seem to be very promising since they don't harass the engine much at lower RPMs, and they do promise to provide very linear throttle response and minimal lag, if any, which are both crucial for track duty.


This is from their facebook page.

Both before and after cars seems to have full exhaust and CAI; at least that's what I assumed "breathing mods" meant. They used UK pump gas.

What do you guys think? At least, this graph does not start from an atmospheric RPM :P

Looking forward to seeing what KraftWerks kit makes in comparison to this one.
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Old 02-11-2014, 05:10 AM   #2
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And here is a little comparison of C-M and KraftWerks kits I made originally at Miata.net today. Admins, I am hoping that copying a post is allowed; apologies if it's not!

MX-5 Miata Forum - View Single Post - [Supercharging] KraftWerks Rotrex Supercharger / Sneak Peek

--------

I've been comparing KraftWerks and C-M kits, and there are a few issues that pop up in both kits:

KraftWerks:
(1) The oil reservoir seems to be higher than the supercharger. Rotrex now recommends that both the oil cooler and the canister should be below the supercharger's height to avoid possible oil leak from some of the seals:




(2)The air filter location for this kit has always been in question since we saw the first pics. The reasoning given to us is that the intercooler pipes are using the opening by the front of the car, leaving no space for the air filter. C-M's kit doesn't seem to have much longer piping, yet they were able to reserve the front opening for the air filter. Wouldn't this be a better solution? (Brian's car seen below).




Corten-Miller
(1)C-M seems to have placed the MAF right after the air filter, BEFORE the supercharger and the intercooler. I don't think what MAF reads in terms of amount of air, and more importantly the air temp will be exactly same as what enters the engine anymore, since the air charge will have to go through the supercharger and the intercooler first. Kraftwerks has kept the MAF location at right before intake manifold, which I think is the best location.


(2)C-M's intercooler looks substantially bigger to me. I am not sure if this is a good or bad thing, considering it comes before all other radiators (like A/C condenser, coolant radiator, etc.). I don't know full dimensions including thickness, so I might also be wrong.
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Old 02-11-2014, 09:42 AM   #3
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A MAF after the compressor will not read compressed air volumes correctly, but may read the temperature more accurately. The MAF before the compressor will have the opposite problem. Ideally, one should either separate the two or use a different measuring device (or algorithm) entirely.
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Old 02-11-2014, 10:13 AM   #4
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Switch to speed density and forget the maf altogether.
As for intake, yeah makes a bit more sense to route it into the bumper.

Not bad overall, I guess, for those that like the rotrex. What kinda pricing?
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Old 02-11-2014, 12:56 PM   #5
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Seems like with a battery/expansion tank relocation they would have room for the intake to go into the bumper and put the oil reservoir in a better place while keeping the intake routing over the top.

Maybe not, or maybe it makes the kit too expensive.
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Old 02-11-2014, 02:58 PM   #6
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Pricing is not yet announced, but historically such kits are priced around $4K with $600 initial pricing discount. That's what I would guess the pricing would be around.

The dyno graph above is said to be at the flywheel. I was very excited thinking it might be at the wheels, but well, I guess it's still not too bad. I wonder how the KraftWerk kit's numbers will turn out now...

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Old 02-11-2014, 05:36 PM   #7
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X25, you work for C-M or something?

What head unit is that? I'm guessing C30 series, probably a -94?
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Old 02-11-2014, 05:44 PM   #8
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Quote:
Originally Posted by EO2K View Post
X25, you work for C-M or something?

What head unit is that? I'm guessing C30 series, probably a -94?
I don't know what C-M uses, but KraftWerks uses C30-84. I don't work for any of these companies, but I want to have a seamless FI solution good for track duty, and these seem to fit the bill. I've suffered quite a bit with turbo kits in my former cars before switching to Corvettes, and I really don't want to go through that again
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Old 02-11-2014, 05:56 PM   #9
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Quote:
Originally Posted by sixshooter View Post
A MAF after the compressor will not read compressed air volumes correctly, but may read the temperature more accurately. The MAF before the compressor will have the opposite problem. Ideally, one should either separate the two or use a different measuring device (or algorithm) entirely.
Its not a AFM, its a MAF. Its measure the mass of the airflow, not the volume. So it works just fine on the high pressure side.
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Old 02-11-2014, 06:01 PM   #10
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Quote:
Originally Posted by Full_Tilt_Boogie View Post

Its not a AFM, its a MAF. Its measure the mass of the airflow, not the volume. So it works just fine on the high pressure side.
Good. I was worried.
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Old 02-11-2014, 06:02 PM   #11
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Quote:
Originally Posted by X25 View Post
... I want to have a seamless FI solution good for track duty, and these seem to fit the bill. I've suffered quite a bit with turbo kits in my former cars before switching to Corvettes, and I really don't want to go through that again
If you want reliability my only advice is this: DO NOT BE AN EARLY ADOPTER.

Make sure the company has the product tested and there are a buttload of them on the road before you buy. A "$500 discount" is not enough to get me to effectively "beta test" a $3.5k product for a company.

I'm no stranger to the Rotrex: https://www.miataturbo.net/random-su...th-fail-62346/
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Old 02-11-2014, 06:03 PM   #12
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Quote:
Originally Posted by X25 View Post
I've suffered quite a bit with turbo kits in my former cars before switching to Corvettes, and I really don't want to go through that again
If you can't figure out turbos then you deserve a supercharger.
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Old 02-11-2014, 07:50 PM   #13
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If you can't figure out turbos then you deserve a supercharger.
YES! I leave turbos to you
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Old 02-11-2014, 07:55 PM   #14
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Originally Posted by Full_Tilt_Boogie View Post
Its not a AFM, its a MAF. Its measure the mass of the airflow, not the volume. So it works just fine on the high pressure side.
Great, so this means KraftWerks' location is much better. I wonder why C-M would even choose to put the MAF location there. Perhaps they don't know any better? That would put serious doubt in my mind in terms of their credibility. EO2K, there goes your theory of me being a C-M salesman.

Quote:
Originally Posted by EO2K View Post
If you want reliability my only advice is this: DO NOT BE AN EARLY ADOPTER.

Make sure the company has the product tested and there are a buttload of them on the road before you buy. A "$500 discount" is not enough to get me to effectively "beta test" a $3.5k product for a company.

I'm no stranger to the Rotrex: https://www.miataturbo.net/random-su...th-fail-62346/
Good point. These companies very often don't even admit to their mistakes and the issues with their kits, and all in a sudden they come up with a new kit 2 years later with all the issues they've been undermining since the first kit, fixed. One mitigation is that these kits are very simple, especially compared to turbo kits. They don't tap into the car's own exhaust, oil, coolant system, and as long as you can keep the belt aligned and running fine with no slip, they will work predictably.

I have actually read your thread before. I'm not sure if it was fun for you to go through that all, but it was fun to read
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Old 02-11-2014, 10:41 PM   #15
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Quote:
Originally Posted by X25 View Post
Great, so this means KraftWerks' location is much better. I wonder why C-M would even choose to put the MAF location there. Perhaps they don't know any better? That would put serious doubt in my mind in terms of their credibility. EO2K, there goes your theory of me being a C-M salesman.
Theoretically, neither is really better than the other.
If the MAF has a IAT sensor then I would put it downstream so that it can use those readings, but it doesnt have to have an IAT sensor at all. Its measuring the mass airflow and because of gas laws you dont have to know IAT, pressure or volume if you know the mass airflow.

In practice, I think that a "blow through" MAF is better because you dont have to recirculate the bypass/BOV and because you can put the sensor closer to the throttle, decreasing its latency (if it even matters).

What is really important is that the MAF is on a good smooth piece of tubing where there is laminar airflow and that it is properly calibrated in the MAF table. If you have that, the car pretty much tunes itself.
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Old 02-11-2014, 11:05 PM   #16
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Quote:
Originally Posted by Full_Tilt_Boogie View Post
Theoretically, neither is really better than the other.
If the MAF has a IAT sensor then I would put it downstream so that it can use those readings, but it doesnt have to have an IAT sensor at all. Its measuring the mass airflow and because of gas laws you dont have to know IAT, pressure or volume if you know the mass airflow.

In practice, I think that a "blow through" MAF is better because you dont have to recirculate the bypass/BOV and because you can put the sensor closer to the throttle, decreasing its latency (if it even matters).

What is really important is that the MAF is on a good smooth piece of tubing where there is laminar airflow and that it is properly calibrated in the MAF table. If you have that, the car pretty much tunes itself.
I don't think we have a separate IAT sensor. Regardless, even for the air flow, keeping closest to the manifold makes most sense in my opinion. Sure, the total amount of air should be same assuming there's no leak in the system, but there would be an inherent lag in readings of the pulsations in the air flow. Even worse, the route of air might create pulsations by the end of IC piping, which would not be captured by the MAF right by the air filter.

Agreed on the importance of smooth piping before and after the MAF. Being right next to the air filter and the violent air flow (at high speeds) could also become a problem.

OK I'm probably blowing it out of proportion, but you get my idea
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Old 02-13-2014, 04:14 AM   #17
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I asked C-M about MAF location. Their response:

Quote:
Thank you for the enquiry. We do not yet have a release date or any pricing information but are working hard to bring it to market ASAP!

As far as MAF placement goes there are pros and cons of both a pull through and blow through arrangement. Our new MAP sensor, unlike the original has an IAT sensor built in so this can now be moved into the inlet manifold to read charge temp and leave the MAF sensor where it is.
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