Anyone know how much power these blowers require to run? My nsx made 440rwhp at 10 psi...so roughly 520 ish crank hp...plus whatever the bbsc needs to turn...makes me think I was actually pushing closer to 575 including whatever was needed to turn the bbsc...just a guess tho...
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Power to run sc?
- Thread starter peiserg
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I think we have about a 12% loss in the drive train so 440HP x 12% is 470 at the fly wheel.
not his question
- Joined
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It take between 50 and 60HP to run a SC.
I always assumed the calculation was crank hp x loss?
i.e. 500 crank x .88 = 440 rwhp. though i thought the loss was more like 14-15pct.
For instance, though it's been a while since i looked at a stock dyno... don't most nsxs dyno stock 240-245 rwhp? 290 x 0.85= 246 rwhp. so 15% drive train loss.
I got to thinking about this since i've been on the ford gt forums, they discussed it... and they seem to think the blower takes about 200 hp to run at full tilt!! The logic being used is that the twin turbo setups at 18 psi make 1000 rwhp and a large upgraded blower at the same psi makes only 750 rwhp.
gerry
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The drag the SC produces will vary at different loads as it is not a constant. I HIGHLY doubt the CTSC (or like) is using 200hp to turn the blower. I'd image on some of the higher boost setups with the blower, it would be roughly around 50hp +/- 20hp.
As far as comparing a turbo to an SC... A turbo will relieve the physical drag that the SC's have, but there are other variables to determine exactly what the parasitic loss is when trying to compare numbers between the two. Looking at IDC's (given they are the same) in reference to RPM/load/boost between the two (turbo/SC), you could probably get a better idea of the loss instead of comparing max boost vs whp.
As far as comparing a turbo to an SC... A turbo will relieve the physical drag that the SC's have, but there are other variables to determine exactly what the parasitic loss is when trying to compare numbers between the two. Looking at IDC's (given they are the same) in reference to RPM/load/boost between the two (turbo/SC), you could probably get a better idea of the loss instead of comparing max boost vs whp.
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well i wouldn't expect the ctsc or bbsc to require that much power since they don't make that much power. The FGT is making 750 rwhp vs nsx at 380ish. Not even the same city, much less the same ballpark.
Here's a compressor map for a similar sized blower to the CTSC:
http://www.opcon.se/www/files/lysholm/pdf/performance charts/diagram_lys1600ax.pdf
I believe a CTSC would be about a 1.5 pressure ratio, and would be flowing around 20 m^3 /min, requiring about 25kw or about 35hp.
I would guess that centrifugal superchargers would be similar.
Here's my question of the day, why don't people use a lighter flywheels when using screw type superchargers? Based on some calculations (admittedly some guessing on the weight and diameter of the SC internals), it seems like there could be as much as 1/4 of the energy stored in the flywheel stored in the supercharger internals. Just a crazy thought, probably not worth losing any sleep over, so perhaps I'll just go take a nap now to prove it.
:wink:
http://www.opcon.se/www/files/lysholm/pdf/performance charts/diagram_lys1600ax.pdf
I believe a CTSC would be about a 1.5 pressure ratio, and would be flowing around 20 m^3 /min, requiring about 25kw or about 35hp.
I would guess that centrifugal superchargers would be similar.
Here's my question of the day, why don't people use a lighter flywheels when using screw type superchargers? Based on some calculations (admittedly some guessing on the weight and diameter of the SC internals), it seems like there could be as much as 1/4 of the energy stored in the flywheel stored in the supercharger internals. Just a crazy thought, probably not worth losing any sleep over, so perhaps I'll just go take a nap now to prove it.
:wink:
Define "way less"; and how do you figure that?
positive displacement blowers(roots) require more energy than centrifigal blowers as evidenced in the increased charge temps. Check intake temps on a paxton at 6 PSI and compare to CTSC at 6 PSI. Paxton should be around 140 F and CTSC around 190F. The actual parasitic loss will depend on size and cfm output of the individual blower. If you want to know exactly how much parasitic loss your particular blower has, go to the dyno, do a run with blower hooked up , but blow off valve open( no actual boost), then a run with blower belt off. The difference will be the parasitic loss.
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I was under the impression that both were screw-type blowers. I fully understand how they work.
Twin screw ("screw-type") blowers are not the same classification as a roots even though they are both PD and look similar on the outside. Internally, they operate very differnet, aside from internals spinning.
http://www.kennebell.net/techinfo/general-info/twinscrew-vs-roots-fromcatalog.pdf
http://www.kennebell.net/techinfo/general-info/twinscrew-vs-roots-fromcatalog.pdf
OK, they both require more energy to run than centrifugal. they create more heat, therefore are less efficient. People use them anyway because the characteristic power under the curve can be more beneficial depending on the type of driving.
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That's fine, but we weren't talking about a centrifugal
Ah, I see. Since all I've really seen done on the NSX's were PD blowers, I assumed this was one of them.
Just a question? If I take a supercharger off of an engine(any supercharger) and placed it on a supercharger dyno(like John Force does) and make that supercharger produce 10 psi and push 400 cfm how much hp does that take? A supercharger can use as much as 1/3 of the power that it produces(slight differences on its efficiency). That means that if your engine produces 300 hp NA and it produces 400 hp supercharged than 400-300=100hp. 1/3 of the 100 hp that the supercharger made was used to build the pressure.This means that the engine actually made 433 hp but used 33 hp to build the pressure. This is a very simple way of figuring out how much hp that a supercharger uses. This is why that at the same pressures(everything equal) a turbo will build approximately 33% more of the difference in power. So in this example the turbo will have built 433 hp. I am sure someone will correct me if this is incorrect. I have had two identically prepared cars,one supercharged, one turbocharged, both ran 8 psi. The turbo car was noticeably faster in all areas. NOW YOU KNOW THE REST OF THE STORY.............................................................
If the 8psi turbo were an exact matching curve of the SC, it will be faster, however, you can size the turbo (or SC) so that it will run out of steam and die up top as well (or make it large and peak boost is made at higher RPM).
There are a lot of variables to work with, but the turbo won't present a mechanical drag of course.
There are a lot of variables to work with, but the turbo won't present a mechanical drag of course.
The Roots type supercharger or Roots blower is a positive displacement lobe pump which operates by pumping fluids with a pair of meshing lobes not unlike a set of stretched gears. Fluid is trapped in pockets surrounding the lobes and carried from the intake side to the exhaust.
First gen 2-lobe roots:
My GTO Roots is the previous generation with 3 lobes:
the new 4 lobe roots that you find on the CTS-V and ZR-1 generates less heat (which is very close to the Twin Screw blowers in terms of less heat):
The twin-screw type supercharger or twin-screw blower is a positive displacement type device that operates by pulling air through a pair of meshing high-tolerance screws similar to a set of worm gears.
The rotary screw compressor has low leakage levels and low parasitic losses vs. roots-type. The supercharger is typically driven directly from the engine's crankshaft via a belt or gear drive. Unlike the Roots type supercharger, the twin-screw exhibits internal compression which is the ability of the device to compress air "within" the housing as it is moved through the device instead of relying upon resistance to flow downstream of the discharge to establish an increase of pressure.
High-precision CNC manufacturing techniques make the screw type supercharger a more expensive alternative to other forms of available forced induction.
A clear example of the technology applied by the twin-screw in companies like Ford, Koenigsegg, Mazda, Mercedes and Mercury Marine can also demonstrate the effectiveness of the twin screw. While some centrifugal superchargers are consistent and reliable, they typically don't produce full boost until near peak engine rpm, while positive displacement superchargers such as Roots type superchargers and twin-screw types offer more immediate boost.
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I would suspect that even though a centrifugal SC is more efficient than a screw type, they still require close to the same power to drive.
I would think that the discharge temp of a SC is not directly connected to it's efficiency.
Think about it, if a compressor was 100% efficient, and therefore all the energy input was converted to potential energy in the form of a higher pressure air with no heat added, it would still require energy input to be converted into the higher potential energy contained in the compressed air.
If you look at a compressor map of a screw type vs a centrifugal type, they are maybe 15%, 20% more efficient.
So, if you're looking at ~35hp for a CTSC, then what, 25+hp for a centrifugal SC??
- Craig
I would think that the discharge temp of a SC is not directly connected to it's efficiency.
Think about it, if a compressor was 100% efficient, and therefore all the energy input was converted to potential energy in the form of a higher pressure air with no heat added, it would still require energy input to be converted into the higher potential energy contained in the compressed air.
If you look at a compressor map of a screw type vs a centrifugal type, they are maybe 15%, 20% more efficient.
So, if you're looking at ~35hp for a CTSC, then what, 25+hp for a centrifugal SC??
- Craig
I think that you need to consider Boyle's law:
pV=k
The more you compress a gas the higher the temperature.
I think this is different to efficiency.
pV=k
The more you compress a gas the higher the temperature.
I think this is different to efficiency.
That is why I stated that at EQUAL PRESSURE the intake temps are higher for CTSC than the Paxton, there for it is using more energy to create the same pressure. This means that it is less efficient and requires more power to do the same work.
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