[Warning: M.net content] Turbos make more power but superchargers make more 'torque' - Page 5 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 02-23-2010, 03:24 PM   #81
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Here is my post on the matter in which I discuss throttle nonlinearity in NA motors. IMO it's an important concept to understand.

MX-5 Miata Forum - View Single Post - old TC vs SC debate...

Hey Sav, how do you think a 220 hp GT2554 setup would compare to a 220 hp s/c setup on the track?
Depends entirely on the track. I think a Rotrex might have a slight edge on a fast track, but the 2554R is going to produce a lot more torque lower down, which means that on a tighter track (i.e. autocross, Streets of Willow, etc) it probably will have a slight advantage.

Julian, what kind of experience does sjmarcy have? I thought he was a fanboi who might have a little experience, but after his "drifting is not performance driving" comment I have basically no respect for his commentary. To me, he sounds like a guy who has NEVER driven a big turbo car, or if he has driven it he hasn't done it fast. People who don't have the experience/skill/both to extract the potential from a 28R/30R sized turbo will obviously badmouth it and say it's slow, when in reality it's the nut behind the wheel that needs adjustment.
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Old 02-23-2010, 03:36 PM   #82
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seems like he has plenty of experience...back in 1980 before he retired and bought a lotus and plays with his accelerometer all day long.

the rotrex needs a transmission module to get full boot earlier.
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Old 02-23-2010, 03:53 PM   #83
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^ Something like a CVT trans. I wonder how much harder it is to design and build a variable planetary gear set.
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Old 02-23-2010, 04:12 PM   #84
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You know, I forgot to mention since people feel that Henessey vipers, Kon. Cars, Bugatti Veyrons, etc are great examples of turbo vs. supercharger debates...

How come nobody mentioned the massive dominance of Turbochargers for over a decade until their ban in Formula One? I mean, turbos running upwards of 40psi with water/toluene as gas? Are you kidding me? Anyway, they basically cleaned the floor with any other sort of competition at the time, and F1 cars had their highest power/speed levels around that time. Its sort of come down back to earth and started to rise, obviously, since then, but I'm sure it was a hell of a time to be an F1 driver.
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Old 02-23-2010, 04:17 PM   #85
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How come nobody mentioned the massive dominance of Turbochargers for over a decade until their ban in Formula One? I mean, turbos running upwards of 40psi with water/toluene as gas? Are you kidding me? Anyway, they basically cleaned the floor with any other sort of competition at the time, and F1 cars had their highest power/speed levels around that time. Its sort of come down back to earth and started to rise, obviously, since then, but I'm sure it was a hell of a time to be an F1 driver.
I'm not sure how relevant it is to the debate for a street car looking for some extra power, but it's an interesting question. Obviously turbocharging is massively popular in almost every series where it's allowed.

Other than drag racing, what other forms of racing allow/encourage supercharger use? I know there's got to be others, but I'm blanking.
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Old 02-23-2010, 04:21 PM   #86
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I'm not sure how relevant it is to the debate for a street car looking for some extra power, but it's an interesting question. Obviously turbocharging is massively popular in almost every series where it's allowed.

Other than drag racing, what other forms of racing allow/encourage supercharger use? I know there's got to be others, but I'm blanking.
No idea. And oh, yea you are totally spot on there, but this plane pretty much spiraled out of control into a firey comet of death after the first page. Somehow it hasn't come to earth yet and everyone is still running around screaming for their lives. Neet.
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Old 02-23-2010, 04:27 PM   #87
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Julian, what kind of experience does sjmarcy have? I thought he was a fanboi who might have a little experience, but after his "drifting is not performance driving" comment I have basically no respect for his commentary. To me, he sounds like a guy who has NEVER driven a big turbo car, or if he has driven it he hasn't done it fast. People who don't have the experience/skill/both to extract the potential from a 28R/30R sized turbo will obviously badmouth it and say it's slow, when in reality it's the nut behind the wheel that needs adjustment.
I don't know him personally, but when he started posting DL1 logs and the likes I looked him up online and saw his name linked to bunch of autocrosses - driving Miatas, Loti, Evo 8, etc. Often he was towards the top of the charts in his region. Just an impression from what I saw online from few searches, I might be wrong of course. At least he has quite some racing experience and most of the people posting at those m.net threads (both turbo and sc owners) have close to zero such experience and are more of a hyping what kit personally have as the best thing out there (turbo fanboys, FFS fanboys, etc. ...)
I've missed the "drifting" comments - maybe he's part of those "elitist" groups who hate drifters

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Old 02-23-2010, 04:30 PM   #88
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Depends entirely on the track. I think a Rotrex might have a slight edge on a fast track, but the 2554R is going to produce a lot more torque lower down, which means that on a tighter track (i.e. autocross, Streets of Willow, etc) it probably will have a slight advantage.
So would this be about accurate in comparison with the Rotrex (assuming optimized setups)?

2554 = more low end, less top end
2560 = about par
2860 = less low end, more top end

And comparing the Rotrex to a turbo is much closer to comparing apples/apples than comparing turbos to a PD supercharger... since as I said before it's basically a belt driven turbo.

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Old 02-23-2010, 04:31 PM   #89
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but none of us spin a turbo compressor like you spin a centrifugal blower.
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Old 02-23-2010, 06:24 PM   #90
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That sjmarcy is a retard, my posts are just to generally **** him off.
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Old 02-23-2010, 08:13 PM   #91
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That thread is the reason "beating a dead horse" and "don't feed the troll" are common internet jargon.
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Old 02-23-2010, 09:30 PM   #92
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but none of us spin a turbo compressor like you spin a centrifugal blower.
With a belt??

Seriously though, my understanding of the Rotrex is that it spins apx the same speeds as an exhaust driven turbine. Biggest difference is its output is directly tied to engine rpm where the exhaust driven unit isn't. Am I missing something else?
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Old 02-23-2010, 09:53 PM   #93
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it still makes boost with rpm rise like all SCers. you'd need to run it completely unrestricted and then close a restrictor with rpm increase so it would output boost like a turbo if I understand it's operation correctly
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Old 02-23-2010, 10:11 PM   #94
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Ive always been confused why they run it that way.
Ive seen other centrifugal supercharger setups that use a bypass system, so that you can use a ratio that builds boost much faster and then maintains it at that level, like a wastegate.
So instead of making 10psi at redline make 10psi from 4k-redline.
I recall asking emelio about this when he initially posted the kit on M.net but he didnt seem to understand what I meant.


After a quick search on the interwebz, I found this,
I give you exibit A:

The blue line is running the supercharger in its normal configuration, the red line is with a boost controlling bypass valve.
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Old 02-23-2010, 10:17 PM   #95
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Are you sure you don't have that backwards? Looks like the blue line makes more torque/hp and more boost overall.

I don't see a big bump in lower rpm torque like you'd expect or any difference in the boost level below about 4500rpm.
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Old 02-23-2010, 10:22 PM   #96
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Looking at the chart again I suspect that they put in the boost control valve but hadn't upped the ratio yet.
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Old 02-23-2010, 10:26 PM   #97
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Originally Posted by Full_Tilt_Boogie View Post
The blue line is running the supercharger in its normal configuration, the red line is with a boost controlling bypass valve.
So much like a wastegate, except it byasses intake air charge instead of exhaust gases. I guess there would not be a loss of efficiency since the compressor will simply spin at tht RPM it spins at as opposed to spining faster and faster. probably a lot cheaper and more reliable than a variable planetary gear set.
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Old 02-23-2010, 10:26 PM   #98
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exactly
it was a proof of concept not a real application

but I know there are kits sold like that because I used to know a guy with such a setup on his mustang GT, he would make like 10psi almost immediately and it would 'creep' to 12 at redline.

You could take a rotex kit and just add a normal wastegate onto the charge pipe to bleed off boost. Then just use the right pulley ratio to spin it as high as you safely can.
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Old 02-23-2010, 11:04 PM   #99
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Sounds like a pain in the butt to get turbo like results, but i think rotrex's are cool. You can't tell me this isn't cool.

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Old 02-23-2010, 11:19 PM   #100
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Originally Posted by Full_Tilt_Boogie View Post
exactly
it was a proof of concept not a real application

but I know there are kits sold like that because I used to know a guy with such a setup on his mustang GT, he would make like 10psi almost immediately and it would 'creep' to 12 at redline.

You could take a rotex kit and just add a normal wastegate onto the charge pipe to bleed off boost. Then just use the right pulley ratio to spin it as high as you safely can.
With the hilarity/insanity on that M.Net thread I have been pondering an FE3/Rotrex build quite a bit. I bet that even the TiAL 38MM I have would be big enough to do the job. I would just recirc it in right before the inlet to the Rotrex, or not at all. I think it would work incredibly well and would probably serve in a weird way the same purposes as both the wastegate and BOV serve on your average turbo setup. Kinda cool. For some real fun, maybe send that air to a duck call.


wwwwwwwwWHHHHHHHHHRRRRRRRRRRRRRRQUAAAAAAAAAAAAAAAA AA!

Sweet.
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