Scott H

I'm thinking the guy with the BMW should just try to adapt this to his car: http://www.harborfreight.com/merchan...tor-94029.html

Willard Bridgham 3

Axial flow fans have odd pressure characteristics as do turbo compressors which you can see from pressure/flow graphs. Their characteristics rarely match and operation of these two fans in series will cause some very unusual pressure conditions at bare minimum.

I wouldn't use this on any car with another fan/compressor in series with it......more is not better.

odurandina

Parral ? i've driven through Parral many times on the way to Mazatlan

Willard Bridgham 3

Parral is where Pancho Villa was murdered, most think on the orders of Alvaro Obregon.

mark kibort

axial flow fans have actuallly very predictable and stable pressure characteristices. spent a lot of time in the flow labs with them. in series, they produced near double pressure. in fact, some early cabin pressure compressors were dual stage axial flow compressors. looked just like big "eRAM"s the only advantage a axial flow compressor provides is greater air flow, and less restrictive bypas if required. axial flow , high flow, low pressure. turbo compressors, or radial fans are great at pressure, but challenged for flow, thats why they need to spn so fast.

The eRAM dual stage fan, with the 2000watt dc brushless motor is quite an amazing device. something like 10lbs of thrust out of a 3.5" diameter openig.
we think we ca get 2psi out of this set up on a 3 liter engine.

Willard Bridgham 3

Check any axial flow fan characteristic flow vs head plot and note that the fan can operate at two flow rates at the same pressure....this is the definition of unstable operation.

mark kibort

I have a library of curves that would disagree with your statement.

In actuality, when you put fans in series,they always produce more presssure at any given flow rate, expecially static. at 0 pressure they would have the same flow rate though. (series vs single, same output fan)

the only unstable range is at stall, but even then, doubling up the fans in series with 0 flow they will produce two diffrent pressure values.

Getting back to this applicatoin, the difference in pressure that the two fans can make at a flow rate that the car's engine demands, is the net pressure gain. its much less than the static value of the fan at stall. we try to operate the fan or fans at half the free air flow rate (0 pressure, max flow) to get some percentage of the fans static pressure characteristics.

Willard Bridgham 3

Vaneaxial fan curve:



http://bioen.okstate.edu/home/jcarol.../FanCurves.pdf

Chris White

here is the proper (and tested) way to do it -
http://tekarazzi.com/2011/04/29/supe...blowers-video/

mark kibort

And your point?

U operate the fan in the zone where the impeller is best absorbing the motors hp

In the graph that is the "selection" zone.

In series the fans static and dynamic pressure doubles

mark kibort

And we got a pure 10 hp with one eRAM on a 911. 6 ftlbs of torque from top to bottom

The cool thing was u could yank it off the car mid run and watch the hp drop on the dyno

Willard Bridgham 3

My point is the same as my original point, ie, running a vaneaxial fan (can have two different volumes at the same pressure) and a turbocharger compressor (radial, backward inclined, airfoil) in series will cause some unusual pressure problems because their performance curves are so different.

Your fan may work on an N/A engine and I have no problem with that; on a turbo car I wouldn't use it because of the mismatch in fan operating characteristics.

mark kibort

Oh. i see your point now. No, actually the axial flow in series with the turbo is not an issue, is the turbo only sees it as a density change. since the change is small, there is no real conseqense to putting a 1psi or 2psi net change in front of the turbo. (as we have experiemented with many times)

the point i was making is that with the fllow pressure characteristics of an axial flow blower, you can use 2 of them in series to up the pressure by almost exactly double at most any flow rate. this is useful for the design, as it is supposed to be high bi-pass when the fans are not in use, contrary to a centrfugal design were because its positive displacement , in line, it always has to spin.

beebone

Wondering, this kinda scam. Better install the vacum in the intake

mark kibort

scam? install a vacuum..what???

No, not a scam. a very inexpensive and creative way to gain up to about 10 rear wheel hp , while putting the power lurking in the dead weight of your battery to work.