So, this may be a dumb thought, but has anyone ever tried it before?

At first thought it kind of makes sense to be able to spin the blower faster at lower rpms through a smaller pulley, and to then let off some of the excess boost in the upper RPM's.

For example: the max impleller rpm for a p1sc or d1sc is 62-65K rpm, does anyone know what the optimum efficiency point is, if one exists?

 

Many, many people try this then realize that you have to use energy to compress the air. Once you have compressed the air it is hotter and the blower is using engine power to do it. So just create heat and use just as much horsepower to run the supercharger.

If you want to do this then get a turbo.

Gary

 

I made a thread about this topic few months ago. We agreed that using some sort of a valve to release the extra boost would be bad because it takes power to make power with a SC and will also generate more heat. At the end the best idea was to use some sort of electric cutout before the blower and try to bleed the air before the blower hence u get lower boost peak and u always can close the cutout to get full boost when u have race gas avaliable, LS1 Edit to change the ign and fuel maps. I think im going to try it soon, Im going with a 12psi pulley and then bleed air before the blower until i get a 8psi. I will just have to find some sort of a switch that can be adjusted so when i close the cutout it will give me 8psi exactly. Until now i didnt find one, so if anyone found such a thing please tell me. Good luck.

 

If i want the max power I would run the max rpm at my shift rpm. So to get a 62K rpm i would try to hit 63K rpm around my shift point. So if my shift point is 6700 rpm then u will need at least a 7inch crank pulley, 3.05 SC pulley(Not a really good size on a Procharger and will give u slippage), 4.10 step up ratio (P or D-1SC). Or it could be easier with a F-1 since it has a 5.0 step up ratio, but 70K RPM max impeller speed. So u will need 7 inch crank pulley, 3.25 SC pulley and 6700 rpm to max the F-1. Good luck.

 

I am not talking about making max power here... I was getting at a way to build more boost at the lower RPM's. I have been thinking about this a lot but clearly blowers are not really set up to run like this.

In industry, centrifugal pumps are generally run at or near their optimum speed all of the time and are not used for variable speed applications. I have a hunch that these prochargers are a lot more effecient when they are spun faster.. but who knows.

Restricting the intake is an interesting idea, but wouldn't that restrict the blower on the low end causing even more power loss to the engine? It's not like boost would just be lmited at a certain psi cut-off point, without effecting low end also... ??

 

I was thinking about that too, but i guess the blower will have enough air to give u the desired boost u want at lower impeller speed(This happens under 5KRPM or so), but it will have problems getting higher boost levels if it doesnt have the extra air to pull which most likely happens in the high impeller speeds. I'm not sure if its right or wrong, but for some reason i dont know how to explain it lol. Im sure the guys can jump in and explain it better.

 

only way to do it is a throttle in front of the blower.

you can then pulley the blower for max rpm and control boost via the amount of air entering the blower.

it shouldn't hurt low end response as the blower doesn't need as much air at that time.

 

I wonder if an DBW throttle body would do the trick? Control it via PCM... that would be tight!! I'm just brainstorming here guys... I certainly don't have a clue.

 

Post a link for this Throttle Body... I would like to read more about it.

 

sorry. Drive by wire.... in general

 

Interesting thread.

If I could control this thru my pcm I would like that... any boost over 10 psi I would vent for strictly pump gas.

 

No really though,. couldn't this be a possibility? Throttle bodys are made to throttle air, why not throttle air into a supercharger and control it via PCM? Taking this a step furthur, I wonder if a MAF could be used before the throttle body to give it a signal when to throtle down? Thoughts....?

ProStockJohn, I just ordered one of those big griffin intercooler's like you and BlackBlown have! I'm pretty excited to be able to turn up the timing a couple of clicks!

 

I think the venting idea is much simpler than the rest. If the vent valve is open, then the SC wont be working as hard as it could be, as there is effectively an open hole after the SC.

I did find read a thread on another forum where a guy with a SC Cobra used an electronic boost controller to control a dump valve ( BOV ), to release boost pressure.

see here, post by eduncan911
http://www.modular4v.com/forums/Show...spx?PostID=637

 

That is awesome... exactly what my original thought was like. Those parts are Expensive though!!

Someone should try this so I know if it works or not.

 

if this is the same setup I think it is the guy concluded it was a big waste of time and money.

its simple physics people. SC's take power to make power, if you use 100hp to make 150 and bleed off 100 your down 50

not too mention the air will be much hotter and as such your more prone to detonate so you need to lower timing, increase fuel, etc....

with the number of years SC's have been around, if this worked it would be an option on every SC kit out there.

 

The ebc he used was expensive. There are other alternatives, that basically allow boost mapping, against rpm, or other inputs.
Apexi's AVC-R is one such controller, although Im sure there are plenty more. Possibly Turbosmarts E-boost, or Greddys Profec A.

I guess another good feature about such a setup, is that you could also increase the boost pressure very easily from the cockpit, with hi and lo settings.
Say low for road/wet use, and high for track use, or just because its more fun, or low because good fuel isnt available.

Expensive...possbily, but so would changing pulleys all the time to try and achieve similar results, but without the in-car control.

Its function would be no different to boost control on a turbo motor, although the plumbing arrangement may be silghtly different.

 

But if you are effectively making only 50bhp after the bleed, then the SC hasnt used the same amount of power to drive it.

Does a SC consume the same amount of power say at 5krpm, when creating boost, as on closed throttle creating no boost ?
A SC should only consume power when it is actually pumping against a restriction ( ie, the engine ). Remove part of this restriction, then the power consumed should be less. If you were totally to vent the SC to atmos, would it still consume 150bhp to drive it ??

Who is to say that something similar may not become an option ?

EBC's are an aftermarket thing even for turbo cars. Why dont all turbo kits use them ?? Because a simple bleed valve works in most cases, and costa a fraction of the price.
Some people just want more from their cars.

 

The HP it takes to drive a supercharger is simply the boost times the flow. There is no way around it.

If you want to regulate your supercharger put the throttle body in front of the blower.

 

Ok, heres a dumb question maybe.

When/If cruising at 3000rpm at part throttle, ie no boost in inlet. What happens the air pumped by the SC. Is the SC still consuming huge amounts of power at this time ?
Whats the difference really ?

 

What about rigging up a variable ratio pulley setup like used on golf carts?