Centri vs Twin screw blowers
09-20-2010, 04:25 PM
#1
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Centri vs Twin screw blowers
So yesterday I read that a centri blower will outperform a twin screw blower at the track. I thought to myself how can that be when with a twin screw it is instant boost and doesn't take rpms to build boost like the centri does.
I'm not trying to start a big debate here but I'm just curious why people say centri blowers are better than twin screw blowers at the drag strip, if in fact they are. I don't want this to be about twin screws and centris on the street, just at the drag strip.
I'm not trying to start a big debate here but I'm just curious why people say centri blowers are better than twin screw blowers at the drag strip, if in fact they are. I don't want this to be about twin screws and centris on the street, just at the drag strip.
09-20-2010, 04:31 PM
#3
I can honestly see how they do better. Not as much problem with heat soak, far better intercooling system, lower iat's from what I've seen, less problem with traction due to not having instant torque, plus centri cars make more peak power from what I've seen. They don't make the torque ts cars do but they make a little bit more power. Does that make sense? Lol it made sense in my mind but idk if it does to you as to why a centri car is better than a ts car for the quarter mile.
09-20-2010, 04:35 PM
#4
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The only arguable reason a sufficiently cooled Twin Screw would fall behind a sufficiently cooled Centri in the quarter is because the centri takes less power to spin, thus "making more power" in the upper rpm range for said amount of boost. Since most of the time on the strip is spent in the upper rpm range, pound for pound of boost they can have the upper hand.
BTW, low end torque is not a "problem" if you have the suspension and tires to back it up.
BTW, low end torque is not a "problem" if you have the suspension and tires to back it up.
Last edited by tbirdscwd; 09-20-2010 at 05:13 PM.
09-20-2010, 04:43 PM
#5
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Are the centri blowers like turbos in respect to being in boost based on pulley size or the size of the blower? With a turbo the smaller the turbo is the sooner it is in full boost. Is that the same with a centri blower?
09-20-2010, 04:44 PM
#6
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I can honestly see how they do better. Not as much problem with heat soak, far better intercooling system, lower iat's from what I've seen, less problem with traction due to not having instant torque, plus centri cars make more peak power from what I've seen. They don't make the torque ts cars do but they make a little bit more power. Does that make sense? Lol it made sense in my mind but idk if it does to you as to why a centri car is better than a ts car for the quarter mile.
09-20-2010, 04:55 PM
#7
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They are both centrifugal compressors, but that is really where the similarity stops. A centri blower makes boost and power linearly as rpm in creases. The amount of boost made is a function of engine rpm (meaning as engine rpm rises, so does boost presure because it is driven by a belt which is ran by the engine's crankshaft). A turbo is driven by the expansion of exhaust gas pressure which spins the turbo instead of the engine spinning a pulley. At a certain rpm based on turbo size, impeller and size of the engine, the turbo will make full boost or full spool and will continue to make the same pressure til redline similar to the way a twin screw operates. As the rpm rises, a wastegate is used to either bleed off pressure or limit the speed of the turbo, either way it limits the amount of pressure the turbo can create on the intake side.
09-20-2010, 04:58 PM
#8
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The only arguable reason a sufficiently cooled Twin Screw would fall behind a sufficiently cooled Centri in the quarter is because takes less power to spin, thus "making more power" in the upper rpm range for said amount of boost. Since most of the time on the strip is spent in the upper rpm range, pound for pound of boost they can have the upper hand.
BTW, low end torque is not a "problem" if you have the suspension and tires to back it up.
BTW, low end torque is not a "problem" if you have the suspension and tires to back it up.
They are both centrifugal compressors, but that is really where the similarity stops. A centri blower makes boost and power linearly as rpm in creases. The amount of boost made is a function of engine rpm (meaning as engine rpm rises, so does boost presure because it is driven by a belt which is ran by the engine's crankshaft). A turbo is driven by the expansion of exhaust gas pressure which spins the turbo instead of the engine spinning a pulley. At a certain rpm based on turbo size, impeller and size of the engine, the turbo will make full boost or full spool and will continue to make the same pressure til redline similar to the way a twin screw operates. As the rpm rises, a wastegate is used to either bleed off pressure or limit the speed of the turbo, either way it limits the amount of pressure the turbo can create on the intake side.
Last edited by amoosenamedhank; 09-20-2010 at 05:02 PM.
09-20-2010, 05:01 PM
#9
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like someone said. twin screws typically lose boost the higher in the RPM band you go. you get full boost at what, 2000RPM. but by redline you've actually lost some boost. centris work the exact other way. with a 6k rpm redline you shift and your at like 3k rpm, right where your power band is starting to hit. typically, your power band with stock heads and cams starts falling off and somewhere around 5200rpm on an NA 2v PI motor. so shifting in at 3k, and building more and more boost the closer you get to 6k rpm typically keeps your overall power higher than having a twin screw that loses boost while your losing horsepower at the same time also.
this is why longtubes > shorties. longtubes make almost zero extra power at 3k rpm. shorties make anywhere from 25-25 extra hp at 3k rpm. but when your at 6k rpm, longtubes have added 15-25, and shorties are maybe 1-5 (all over stock manifolds). NOW, your overall horsepower gained might be the same, but peak numbers and more importantly usable power band is better for drag racing with mods that continue to gain power the higher into the RPM band you go.
Last edited by MU71L4710N; 09-20-2010 at 05:07 PM.
09-20-2010, 05:08 PM
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ehhhh not really either. the smaller the pulley, the higher your boost. if your pulleyd for 10psi, you get like zero boost at 3k right when you start to boost. then the closer you get to 6k rpm, the higher your PSI climbs until you reach your max point. if you were pulleyed for 20psi, same story. zero when you start boosting, and the closer you get to redline the more your boost goes up. it works off ratios.
like someone said. twin screws typically lose boost also the higher in the RPM band you go. you get full boost at what, 2000RPM. but by redline you've actually lost some boost. centris work the exact other way. with a 6k rpm redline you shift and your at like 3k rpm, right where your power band is starting to hit. typically, your power band with stock heads and cams starts falling off and somewhere around 5200rpm on an NA motor. so shifting in at 3k, and building more and more boost the closer you get to 6k rpm typically keeps your overall power higher than having a twin screw that loses boost while your losing horsepower at the same time also.
this is why longtubes > shorties. longtubes make almost zero extra power at 3k rpm. shorties make anywhere from 25-25 extra hp at 3k rpm. but when your at 6k rpm, longtubes have added 15-25, and shorties maybe 1-2 (all over stock manifolds). NOW, your overall horsepower gained might be the same, but peak numbers and more importantly usable power band is better for drag racing with mods that continue to gain power the higher into the RPM band you go.
like someone said. twin screws typically lose boost also the higher in the RPM band you go. you get full boost at what, 2000RPM. but by redline you've actually lost some boost. centris work the exact other way. with a 6k rpm redline you shift and your at like 3k rpm, right where your power band is starting to hit. typically, your power band with stock heads and cams starts falling off and somewhere around 5200rpm on an NA motor. so shifting in at 3k, and building more and more boost the closer you get to 6k rpm typically keeps your overall power higher than having a twin screw that loses boost while your losing horsepower at the same time also.
this is why longtubes > shorties. longtubes make almost zero extra power at 3k rpm. shorties make anywhere from 25-25 extra hp at 3k rpm. but when your at 6k rpm, longtubes have added 15-25, and shorties maybe 1-2 (all over stock manifolds). NOW, your overall horsepower gained might be the same, but peak numbers and more importantly usable power band is better for drag racing with mods that continue to gain power the higher into the RPM band you go.
This is why the centri style cars tend to be faster at the track... As long as your blower is appropriately sized, the only think stopping you from making more and more boost, is your shift.