How a Centrifugal Supercharger works

[RyanJayG]

you are correct, turbo "lag" is just that, the time between no boost and when it starts to make boost. it has been said over and over again, newer turbos have been designed for gasoline engines and have VERY little lag if the correct turbo is chosen for a given application. older turbos like the T3 super 60 was designed for deisel engines, which have totally different characteristics.

also, just like you said, the turbo will build boost faster because it is not RPM dependant to produce boost, its load dependant. the centerfugal SC will undoubtably feel smoother transfer power smoother etc. but the turbo is capable of producing more low end boost still.

so here is the decision, do you want more power down low, or better smoothness with no "lag" but less low end power?

of course this comparison only works for centerfugal type SC's... a roots or twin screw are positive displacement SC's and produce boost practically at idle, be design

 

[Super Matty P]

yes, a turbo will build boost faster. a centrifugal sc will build boost based on engine rpms...the higher you spin it the more you make. This, in effect, gives you the feeling of having a much larger NA engine under the hood rather than a 4banger with a big thrust mid-range.

 

[Super Matty P]

you're also assuming that ALL centrifugal superchargers on ALL motors will produce no low end power Ryan.

In my situation you have a blower designed to feed a 5.0L V8 @ 6psi. I'm taking that exact same 6psi and stuffing it into a 2.0L 4cyl. There's going to be a good bit more response than you would like to give me credit for.

I guess you'd really have to see it in person to get an idea for how much air this blower moves even at low rpms. In the video's I posted it was set with a 6psi pulley and I never revved higher than 4500rpms....so less than 4psi of air was enough to blow all of our tools across Dave's shop floor and that's coming out of a 3" outlet.

 

[RyanJayG]

I still think the pulley required to make that low rpm boost will over boost you at higher rpms...

 

[Super Matty P]

dude...the pulley I've designed is made for OUR cars...not some generic engine. It's based on our crank pulley size and the desired blower rpms at each boost level.

For instance if the impellor spins 24,000rpms at 6psi on a 5.5" crank pulley we used a formula to determine the impellor psi for our crank speed.

 

[accuser]

nick... i've got the gain on my boost controller set all the way... i did that on purpose so i wouldn't have a hard time staying out of boost on regular driving... i can change that whenever i want... the joys of an electronic boost controller...

-pedro

What other mods do you have? Your boost tip in seems to be a little higher then it should be. I am more or less done with this thread. I will wait untill the unit is up and running right, if ever. Then I will be back to go over the results and dyno numbers. We then will see how far off I am in my thinking.

 

[MPNick]

nick... i've got the gain on my boost controller set all the way... i did that on purpose so i wouldn't have a hard time staying out of boost on regular driving... i can change that whenever i want... the joys of an electronic boost controller...

-pedro

What about exhaust system, or intercooler? Somewhere you are starting a little later then you should.

 

[MPNick]

dude...the pulley I've designed is made for OUR cars...not some generic engine. It's based on our crank pulley size and the desired blower rpms at each boost level.

For instance if the impellor spins 24,000rpms at 6psi on a 5.5" crank pulley we used a formula to determine the impellor psi for our crank speed.

On what engine? The rpms will change from engine to engine. 24,000 may be 6 psi on the Mazda but not on the Mustang.

 

[anarchistchiken]

Nick you know so much, do we have a 5.5" crank pulley?

 

[Super Matty P]

dude...the pulley I've designed is made for OUR cars...not some generic engine. It's based on our crank pulley size and the desired blower rpms at each boost level.

For instance if the impellor spins 24,000rpms at 6psi on a 5.5" crank pulley we used a formula to determine the impellor psi for our crank speed.

 

[RyanJayG]

I think Nick is referring to the ratio of the amount of air moved by the supercharger at a given RPM and the amount of air the two different engines can move themselves.

its the differences in packpressure.

since we know that the S/C will move X amount of air (CFM) at a 24,000 rpms, and you know at what rpm the mazda engine will produce 24,000rpms of the S/C (because you know the size of the crank pulley).

all he is saying is that the CFM required to make 6psi on a mazda 2.0L is not the same amount of CFM required to make 6psi on a 4.6L mustang.

oh, and this DOES matter because the centerfugal S/C is not a true air pump like a twin screw type is. it is RPM dependant to move CFM, not to make boost. a certain amout of CFM will make a certain psi on different engines

 

[RyanJayG]

one more thing, I'm not saying you haven't done these calculations, I'm just clarifying the point Nick was making. I understand people have beenn attacking your product, but it is their right to ask questions, and voice doubts, so try to remain calm

 

[accuser]

if i'm loosing anything... it's at the exhaust... i'm still running with the stock piping... holidays totally set me back... hehehe...

i'm going to have the exhaust custom made at my friend's minekey...

-pedro

What about exhaust system, or intercooler? Somewhere you are starting a little later then you should.

 

[Super Matty P]

I had to type in caps there so I was sure the point would get across. I'm not mad at all. I just don't like repeating myself on stuff i've gone over several times before. I've made a couple of in-depth write-ups discussing everything I'm doing and instead of asking me questions in there it's done in this manner.

I understand what you're saying Ryan, that by throwing Xcfm into a V8 to make 6psi by throwing the same Xcfm into a 4i I'd be getting much more psi. I agree that this is an issue. What I guess wasn't explained is that we've gotten with Powerdyne and I'm using the same formulas they use when designing pulleys based for specific engines. The pulley size I'm using for 6psi on the 2.0L protege is very close to the same one as their initial (un-finished/released) 1.6L honda kit.