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Old 11-10-2009, 02:14 PM   #41
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I do like the IM....
Thanks. It turned out pretty well. It's all Ross Machine Racing stuff, plus composite horns inside to fix the bonehead short runners I put on the first time. The IM helps a lot to mitigate the peaky nature that centrifugal blowers (without any inlet restrictor) tend to produce.
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Old 11-10-2009, 02:55 PM   #42
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Mine was fairly cheap:

Rotrex $1500 (craigslist)
TDR IC $1100
Intake manifold parts $350
Tubing & Hoses $150
Ebay BOV $32

Total $3132

This ignores the built motor, etc. since you'd have to do those things for any high power setup.
5 deg F above ambient is amazing. And completely impossible except at low boost and only one pull. If you had a 100% efficient compressor (no such thing) and a 90% efficient intercooler (not likely), you could have at most 5.5 psi of boost and still run only 5F above ambient. That calculation applies to sustained power, not one squirt.
Try 20+ minute track sessions. Datalogs show a max of 88degrees on track, max temp of the day was 85. 10.5psi with a GT28RS making ~230whp on a stock 1.6l. Just for reference. Hottest I saw all day was sitting in grid... once moving... temps just go to their happy place.

I'm assuming you have something beyond stock header? That counts in a way, only because we are comparing to turbo systems which use custom manifolds. May as well compare apples to oranges as close as we can.

Over 3k... with a used 'heart' of your system costing 1.5k. When a turbo can do the same power, with earlier torque (in typical setups) and be replaced if any failure for at least half that price. Over 1k on an IC... you are insane Sorry, not saying that in a mean way... but over 1k on an IC is just nuts . No qualm with the ebay bov, lubed up they work fine by me. Not sure I see the reason for the Intake Manifold parts in that list, header I could... IM though? We really should include custom work, since the Rotrex mounting was not a production piece (at least I read it that way?).... so a custom exhaust manifold would be a legit expense on the turbo side.

The High end cost of the system just doesn't make sense. Sorry. Of course its just my opinion... I just prefer to make less of a parasitic system. I prefer symbiotic relationships.

Last edited by Splitime; 11-10-2009 at 03:08 PM.
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Old 11-10-2009, 03:23 PM   #43
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Try 20+ minute track sessions. Datalogs show a max of 88degrees on track, max temp of the day was 85. 10.5psi with a GT28RS making ~230whp on a stock 1.6l. Just for reference. Hottest I saw all day was sitting in grid... once moving... temps just go to their happy place.

I'm assuming you have something beyond stock header? That counts in a way, only because we are comparing to turbo systems which use custom manifolds. May as well compare apples to oranges as close as we can.

Over 3k... with a used 'heart' of your system costing 1.5k. When a turbo can do the same power, with earlier torque (in typical setups) and be replaced if any failure for at least half that price. Over 1k on an IC... you are insane Sorry, not saying that in a mean way... but over 1k on an IC is just nuts . No qualm with the ebay bov, lubed up they work fine by me. Not sure I see the reason for the Intake Manifold parts in that list, header I could... IM though? We really should include custom work, since the Rotrex mounting was not a production piece (at least I read it that way?).... so a custom exhaust manifold would be a legit expense on the turbo side.

The High end cost of the system just doesn't make sense. Sorry. Of course its just my opinion... I just prefer to make less of a parasitic system. I prefer symbiotic relationships.
I won't dispute your measured temps, but the physics (the same ones used to design the components that your system uses) say no way.

The Rotrex was brand new, and I was lucky to find it that cheap. They are $2200 new.

The IM was on there because it was a big part of the power, and people chasing power frequently do put on aftermarket IMs but usually not that cheaply.

The header is a Racing Beat, $400. I forgot that part.

If I was going for cheap (I wasn't really but it worked out that way), I'd change to an Ebay intercooler and knock another $600 off the cost. The TDR stuff was really nice, though - all the parts fit and didn't look ugly. I figured I had my hands full with building my own intake manifold, plumbing and SC brackets.
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Old 11-10-2009, 03:29 PM   #44
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Despite what your physics are telling you... my datalogs disagree with you. I have the open cage quicker responding GM sensor. Properly calibrated. I also see nice quick heatsoak while sitting... the highest temps the car ever sees are sitting. Oh and I didn't do any physics work designing my system... we just built it. Its all DIY.

Trust me... the cooling works.... the trick is oversized IC and proper ducting....

Let me know when I should post a picture for a big clue

Last edited by Splitime; 11-10-2009 at 03:44 PM.
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Old 11-10-2009, 03:57 PM   #45
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Datalogs show a max of 88degrees on track, max temp of the day was 85. 10.5psi with a GT28RS making ~230whp on a stock 1.6l.
That's some IC. You get exactly that temperature rise with an 80% efficient compressor and a 97% efficient IC.
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Old 11-10-2009, 03:59 PM   #46
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That's some IC. You get exactly that temperature rise with an 80% efficient compressor and a 97% efficient IC.
That it is. Super high quality ebay XSpower unit . Heh.
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Old 11-10-2009, 08:01 PM   #47
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Splitime,

Do you have a datalog in 3rd or 4th gear from say 3500rpm from steady state closed throttle (30~50 kpa) to say 5.5psi indicating how long it takes your system to generate that area under the curve after going to WOT?

I'm assuming a slope, perhaps even a steep one.
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Old 11-10-2009, 09:19 PM   #48
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I'll only have logs in 10.5 psi. Never saw need to run a smaller spring in the WG.

I'll have to look for the logs, been computer hoping.

IATs drop over the length of pulls though.

Here is the dyno with the damaged turbine wheel though. Also of note is that its just a fuel tune, I'm running someone elses base/safe timing map. Never saw the need to wring it out.


Here is a log I have online atm, its a full 1/4 mile run. If it was when I think it was, I believe it was mid to high 70s for that meet.
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Old 11-10-2009, 09:49 PM   #49
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Splitime,

I was looking for more of a roll on. Steady state cruising on near closed throttle to WOT at 3500 rpm in 3rd gear. Something to see how fast it makes boost with the turbo not already spooled.

BTW, where is your IAT located precisely?
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Old 11-10-2009, 10:00 PM   #50
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Originally Posted by emilio700 View Post
Splitime,

I was looking for more of a roll on. Steady state cruising on near closed throttle to WOT at 3500 rpm in 3rd gear. Something to see how fast it makes boost with the turbo not already spooled.

BTW, where is your IAT located precisely?
Right in the intake manifold. Welded bung sticking out the bottom.

I don't think I have any roll on logs. I'll see if I can find any though. I'm actually done for the season and car is up on jackstands for prep for next season already. So no fresh datalogs anytime soon. I bet Braineack could do some though, he won't have my IATs though. I can assume you are looking to see if the Large IC is affecting spool... thus data from my specific setup. If that is the case, also realize that my IC piping is about 2 feet total.
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Old 11-10-2009, 11:32 PM   #51
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To me, the giant fat torque plots from some larger turbo installs are dyno queen numbers. Chop the throttle mid corner for half a second, then pick up say 50% throttle and you may or may not instantly get 100% of the torque the system is capable of making at that RPM/TP. Too much like driving an automatic for my taste. Yes its capable of making torque but when? FWIW, I've driven maybe 50 turbo and S/C cars over the last 19 years of playing with Miatas, including two of my own. So there is some relevant experience.

The 2554R, I/C, standalone, 2.5" exhaust set up I ran for about a year was great, particularly for autocross. Perfectly sized for the 99 engine. Instant torque and linear throttle response but weak top end. Every larger turbo I've driven trades off that instant response for top end power. The only systems that matched the response, had less torque, including cold and hotside MP62's. The solution is an LSx!

Anyway yeah, centrifugal SC's lose the .jpg torque curve contest against turbos but win the (never-mentioned) boost response one. Like boost response is taboo on a turbo forum. Perish the thought.

The negative comments on the Rotrex based systems are funny, particularly from guys who never even seen one let alone driven one on the track. The OP, myself and TDH are just sharing our solutions and development. The stuff works, is fast, very simple to tune, reliable and most importantly, super fun to drive.

Drag racing/dyno pulls ≠ driving around corners at the limit of traction.
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Old 11-10-2009, 11:44 PM   #52
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Originally Posted by emilio700 View Post

Drag racing/dyno pulls ≠ driving around corners at the limit of traction.
You asked for data... I provided what I had.

The car is built and used on track. Visits to anything else are to fill boredom between events. Don't try and use that to "put" down the turbo setup.

I find the turbo quite easy to peddle during turns, that is the fun of a BB turbo... just that bit extra response it offers. Partial throttle boost works as i would want.

I know I've not driven as many Miatas as you... and I NEVER will... I don't drive other peoples cars... just the ones I build, it is never worth the risk of an unknown failure and having to replace a car. (if all those setups you drove were yours... I withdraw the somewhat annoyed format I posted that run on sentence up with, I'm not a fan of people driving other people's cars on track... thats a realm for paid drivers only imo)

Mainly I just don't ever see myself being sold on a parasitic system. It doesn't make sense, especially considering the cost (at least in my book). Using the mechanical energy the engine is already putting out... just does.
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Old 11-10-2009, 11:57 PM   #53
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One of the local shops here in Huntsville does modified BRP MP62 kits on S2000s and Miatas, and they flat haul ***. In kill mode, the shop manager's Miata makes ~240 wheel and more torque, and it makes that torque from idle to redline. I've autocrossed it some, and the thing is simply disgusting. It'll blow 225/60-14 Hoosiers off at will at essentially any reasonable autocross speed.

That said, big power centrifugals are... a pain in the *** at best. My buddy's 97 Cobra makes 600+ through a C4 and a 9", and it was nigh un-drivable. It made so much power on the top end that you couldn't shift it fast enough with the 5 speed to stay out of the limiter, and every time you hit the limiter it would toss/ shred the belt (10 rib aftermarket setup, aftermarket tensioners, etc). For a medium power setup, I could see it being fun, but I can't ever see it being economical...
Don't believe that for a minute.
Show us some dyno plots.
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Old 11-11-2009, 12:18 AM   #54
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Chill dude..

Turbos are exhaust gas driven and will always have some measurable non-linearity between TP and torque response. I like linearity. That is a preference, not a "put down". You prefer low end torque and are OK with a little lag in some realms of the cars performance envelope.

The whole "torque fail" thing is sophomoric.

You provided torque response when already spooled = dyno queen/drag race.
I have been reading that crap for 30 years. I won't argue that point as there is no argument. Tip in from steady state closed throttle, non-loaded from your "area under the curve" in 3rd gear and lets see how many tenths of a second it take for the system to deliver the same torque @rpm as it did in the loaded dyno plot. I will guarantee you a beer the next time I see you, if it is exactly the same in both logs. That, my friend is the difference between your turbo system and Rotrex based system making the same peak power.

Does it matter to you? Clearly not but that's OK. There is nothing to defend, no one has claimed superiority by either system. Just one guy sharing his data and enthusiasm for his successful DIY build in a thread about the Rotrex systems.
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Old 11-15-2009, 06:34 PM   #55
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Emilio,

Curious now that you've had some time and experience with and around the Rotrex. How would you compare or contrast the Rotrex unit to the Vortech supercharger? The obvious is the Rotrex is fully self contained for oiling. Other than that?
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Old 11-15-2009, 08:46 PM   #56
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Emilio,

Curious now that you've had some time and experience with and around the Rotrex. How would you compare or contrast the Rotrex unit to the Vortech supercharger? The obvious is the Rotrex is fully self contained for oiling. Other than that?
I don't have any experience with the Vortech other than looking at their data. They have lower gearing with less step-up, so they run a big compressor at low speed (50K rpm) rather than a smaller compressor at higher speed (100K+ rpm) like the Rotrex. The maps look like they are more oriented toward high flow at low boost, not what a Miata wants (unless you have an LS1 in there).

Maybe a compressor guru can chime in with the trade-offs on big/slow vs. small/fast?
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Old 11-16-2009, 12:55 AM   #57
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Emilio,

Curious now that you've had some time and experience with and around the Rotrex. How would you compare or contrast the Rotrex unit to the Vortech supercharger? The obvious is the Rotrex is fully self contained for oiling. Other than that?
The Vortech, running at about a 2:1 drive ratio, needs a much larger compressor to move as much CFM as a turbo or Rotrex moving the same amount. More mass means more load, it runs much hotter and needs more cooling. Because the larger Vortech is not efficient at low compressor speeds, it tends to be even more top end focused in its output than the Rotrex.

For a given CFM output, the Rotrex is about half the size.

The Rotrex, due to the turbo like compressor speeds, uses a much more efficient compressor wheel design that the much slower spinning Vortech.

As far as I cam see, the Rotrex is more efficient in every way you can measure the performance a belt driven centrifugal supercharger.
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Old 11-16-2009, 02:37 PM   #58
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Originally Posted by Braineack View Post
Talk to Emilio.


here's my rotrex:






ps. not really


But here's the reason that for most intents and purposes superchargers are FTL:

That boost curve looks a lot like a turbo boost profile.
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Old 11-19-2009, 12:15 AM   #59
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so im new to boost, and still learning
i want about 190-210whp and ill be more than content
weekend driver
all of my friends with turbochargers constantly have issues/problems/tuning,etc...
the way the kraftwerks site advertises this thing it looks pretty simple (in it's Base kit form) but i need more hp

however exactly what do i need to make these numbers, as i see they don't have any high boost kit/upgrades for the miata, but apparently other people already have achieved said numbers with the rotrex.
sorry for the noob comment, but this is all so new to me.
hence ill do the buying and let someone else install, im not really car savvy
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Old 11-19-2009, 01:02 AM   #60
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however exactly what do i need to make these numbers, as i see they don't have any high boost kit/upgrades for the miata, but apparently other people already have achieved said numbers with the rotrex.
I'll try to answer your question in our main thread here
https://www.miataturbo.net/forum/t35489/
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