Blower on demand

[Racer X]

Hey guys I'm putting a blower on a l31 5.7 and wanting to use an A/C clutch for an on demand system. Since it's a work truck it only needs the blower for hill climbing and low end work. At cruising speeds it will be turned off and the blower is bypassed to run it N/A. I'm using an M112 blower and don't want to stress the snout of it so I'm going with a jackshaft and second belt so I can make pulley changes/service easier. That Jackshaft will essentially duplicate the crank pulley and have the A/C clutch mounted to it. This will let me set the blower in the right place ie. further back, and get some much needed front clearance with the pressure in the center of the plenum.
What I need to know is what A/C clutch would handle the amount of torque produced by a dead stop blower. I have looked at the clutch for an S55 AMG circa 2004 and was going to try to mount it on the snout but they are prohibitively expensive and very hard to find a complete unit. A/C clutches are a dime a dozen and surely there is a big one that could handle it. Since it's on a jackshaft made from an A/C pump I just need to choose the right pump to make it from. Any suggestions would be greatly appreciated.
To answer the obvious questions The truck has a forged bottom end, Custom intake W/air to water pre charge intercooler, charge air intercooler, 0411 swap, and X24 CNP so control is not the issue. Just don't want to buy 10 different pumps to trial and error it out.

Thanks
Racer X

 

[Erik the Awful]

An A/C clutch isn't strong enough. Also, the blower on Mad Max's Falcon XB was faked.

That said, the Toyota Previa has a supercharger clutch that might work.
https://www.autoweek.com/car-life/d...ur-supercharger-mad-max-heres-correct-switch/

 

[Hipster]

LOL, I was thinking "Mad Max " when I read it the first time.


How you going to get air through a blower that's turned off?

I know some like Mecedes have systems that bypass the blower during light throttle/cruise but you're talking electronically controlled and gated blower housing/intake that have an air path around the blower mechanism coupled with direct port injection.

 

[454cid]

Why not just hook the blower up full time, like normal, and keep your foot out of it when you don't need it? I would think tuning would be a nightmare, on top of the complexity of the physical mechanics of the install.

 

[Madscientist]

Blowers have an internal bypass in them that open up under part throttle and allow air to bypass the rotors and free up parasitic drag when out of boost. They draw virtually no hp loss. You will get better mileage and less headaches tuning just hooking the belt up and leaving it. Not saying its a dumb idea. Just more problematic than you realize up front.

 

[Supercharged111]

An A/C clutch isn't strong enough. Also, the blower on Mad Max's Falcon XB was faked.

That said, the Toyota Previa has a supercharger clutch that might work.
https://www.autoweek.com/car-life/d...ur-supercharger-mad-max-heres-correct-switch/

The Previa used a 1.4L roots blower like their full size cars. I had a Corolla with a 1.2L blower that later got a 1.4 from a car. Their blower clutches work nicely, but it's tough to draw decent airflow through stationary rotors. On my 1.6L I used a Vortec mondo bypass valve that had a 2" inlet. Even with that, the car struggled with the blower off as with any sort of load the bpv would close. Full time blowers like the Whipples on both of my trucks have bypass valves and when empty they get NA fuel economy so my input is that you're overthinking this having been down that road. In addition, the Toyota blower pulleys are way too big to make any sort of boost on these motors.

 

[Racer X]

LOL, I was thinking "Mad Max " when I read it the first time.


How you going to get air through a blower that's turned off?

I know some like Mecedes have systems that bypass the blower during light throttle/cruise but you're talking electronically controlled and gated blower housing/intake that have an air path around the blower mechanism coupled with direct port injection.

My system uses a bypass that ports the NA to the charge air cooler like the mercedes system. The blower also has a bypass on it but it's too small to be useful for anything but full off throttle. So I added one on the other end of the manifold in the plenum above the charge air cooler. It is electronically controlled, the stock bypass on the m112 is vacuum controlled.

 

[Racer X]

Hey guys I know this system seems overly complicated and it is. But this design will allow me to keep temperatures down in any weather or traffic conditions and truly have power on demand. Superchargers if they are going to go forward are all going to be clutched and used for a certain set of conditions during loading/acceleration. I see using a supercharger for full time operation as a trade off for cubic inches. I have cubic inches and want some extra power when I need it, coupler be damned. Besides I have a new vertical mill and a tig welder so I'm having fun. Yes tuning this pig is going to be a *****. I'm hoping I can get the 0411 PCM to turn the blower on and control the main bypass properly. I'll cross that bridge when I get to it. I can always add an arduino controller to it and make it do whatever I want. Getting it to supply enough fuel? well that might be an issue but I think the 0411 can deal with boost.

 

[L31MaxExpress]

No sense to clutch it. I doubt blowers are getting a clutch anytime soon. They use less than 1/2 hp at cruising speed with the bypass open. A clutch is an unecessary, problem prone and expensive addition.

Even Nissans 2.5L Hybrid driveline for the Murano and Pathfinder used a clutch-less blower.

Best fuel economy option would be a turbo with a vacuum actuated part-throttle open waste gate that was sized large enough to prevent any additional exhaust backpressure from building until the intake manifold vacuum dropped off to practically zero.

 

[1989GMCSIERRA]

Why don’t you just adjust your driving style instead of fabricating such complicated system?
Is this for a replica of Mad Max Falcon Interceptor? AFAIK that was fake