Ok, I got an idea here, I've seen it done before, but not sure how.

As we all know, centrifrgal (sp?) superchargers gain boost as RPM's rise. So if you have an 8 psi system, you only see 8 psi at the very top of the RPM band.

And then I am thinking, turbo system's make max boost much lower in the RPM range.

And if I am correct, boost on a S/C setup is limited to the size of the pulley and amount of RPM's the engine can rev to. And the boost of a turbo system is limited by a wastegate which basically only lets a certain amount of boost into the engine.

So why not throw on a super small pulley so the S/C would make 8 psi really quickly, and then limit it to 8 psi with a wastegate?

Obviously custom software would be necessary.

This would give the engine a power curve similar to roots type blowers seen on S/C Jags, Mercedes, lightenings, etc. They make some really good low down torque.

Let me know what you guys think and if this makes any sense to you.

a good thought, however you forgot one point. Centrifugal SC's have a redline meaning you'd have to take that into account.

Also the heat generated by the SC to produce a huge amount of boost at redline will something you have to contend with. Since you will be bleeding boost of above 8 PSI...on the higher RPM you will have high amounts of heat and only 8PSI....

Its like getting 14 PSI of heat for only 8 PSI....

Two very good points which I have considered.

As far as the "redline" or boost limit on a supercharger, obviously you wouldnt want to use a pulley that would exceed that limit.

The vortech site isnt working for me, so if someone could find out the limit for the V2 units, but I think it is somewhere in the 20 psi range. So obviously you wouldnt want to exceed that. But I think that even running a 15 psi pulley, you would get to your target boost (say 8) much faster.

And then the heat issue. I assume this is bad in two ways, first being it heats up the intake charge ALOT and second, it is bad for the supercharger itself (probabily reducing its lifespan).

For the intake charge, there are a few options.

1. Front mount intercooler or for those that dont like custom frabrication, an RMS aftercooler.

2. Water injection. Dont know much about this, except that it somewhat cools the intake charge.

3. Propane or Nitrous injection. Propane comes out of the nozzle at -60 or so degrees, easily taking care of the heat. Nitrous also has the same effect.

If I had my way, I would do a front mount spearco w/ nitrous or propane injection.

Also, a way to cool down the supercharger itself would be to run an oil cooler. Since the vortech units run on the engine's oil (instead of its own oil), you could mount an oil cooler right before the supercharger to cool the oil down before it goes thru it.

The optimum solution would be to run a clutch type of unit on the supercharger pulley to slip it when it gets to your desired boost level, but I have never heard of anything like that (have any of you guys?).

Another nice thing with this setup would be the option to run a boost controller in your car so you could boost low on the street for lower wear on the engine and then when racing, you could run a high boost map.

Anyone else's input would be great.

You can't use a "wastegate" per se, as a wastegate bleeds off exhaust gases from the turbine side of the turbo, which then limits boost created by the compressor side by limiting the speed of the compressor wheel.

To do this with a SC where there is no turbine, you have to either find a way to limit the speed of the compressor once it reaches your desired boost level (and this would not mean constant speed, as pressure would be constant, but flow would still be increasing), or to "bleed" off boost. To bleed, you would have to use a bypass valve. You would obviously not want or be able to bleed off to atmosphere unless you switched to a MAP based fuel injection system.

As others suggested, the main issue with this is that you would need to really overdrive the crap out of the compressor to make a difference at the very low end due to the nature of a centrifugal's operation, and that you would then be wasting a HUGE amount of power to drive the compressor and creating a huge amount of unwanted heat to do it.

The idea is good, but there has to be a better way...

Steve

You're trying to make a square wheel round...

Vortech style compressors build boost exponentially, the engine consumes Air linearly. They can theoretically be "corrected" (variable gearing) to function linearly, but again square wheel round...

The ideal solution is a screw-type supercharger that builds boost linearly.

You already have the attention of the right guy, why not pre-order a kit from stimpee?:D

just remember, to have 8 psi at 6000 rpms, you will have 2.8 psi at 3000 rpms which is the square root of 8 at half the rpms. To have 8 psi at 3000 rpms will require 64 psi at 6000 rpms. You will need a very large vortech blower. It will take too much HP and too much heat to come out with 64 psi.

I believe the max PSI the vortech blower V2 can take is 25psi

Originally posted by Stylin
I believe the max PSI the vortech blower V2 can take is 25psi

Right. So that means that 25 psi at 6000 rpms will give you 5 psi
at 3000 rpms. That's why I mentioned a larger blower. Now if we can just some how fit a positive displacement supercharger it's a whole different ball game.

5psi at 3000rpms isnt shabby either.. ;)

but I wouldnt want to run the vortech at 25psi tho..

Originally posted by Stylin
5psi at 3000rpms isnt shabby either.. ;)

but I wouldnt want to run the vortech at 25psi tho..


Yeah, I hear yah! But it takes hp to make hp. It will be a waste of hp to get 25 psi and only use a max of say 10 psi.

Originally posted by m3boost


Right. So that means that 25 psi at 6000 rpms will give you 5 psi
at 3000 rpms. That's why I mentioned a larger blower. Now if we can just some how fit a positive displacement supercharger it's a whole different ball game.

Don't worry guys, "WE" are working on it!!!

Making good progress this week...

Steve

keep in mind that we are very close to the V2-SQ's redline already. The max boost pressure depends on how well the head in question flows and, relative to other large displacement domestics, our heads flow very well. We see less boost per rpm because we are flowing more air.

I doubt you could make a vortech on an M3 produce more than 15 psi at 7000rpm without oversteping the redline.

The only elegant solution - providing fairly flat, even, efficient boost - for our beloved mechanically-driven centrifugal compressors is a CVT in place of a constant step up. Hydraulic coupling attains a similar result and there have been many multi-geared blowers over the years. Study up on aviation systems, remember that anything tried on the ground has likely been hashed out in a multitude of variations in the sky - these devices were initially put forth as altitude compensation. For automotive use check out the 2-gear Paxtons used on Studebakers from about 4-5 decades ago. Hmm... that sure is a long time to engineer something better.

IMO nothing beats a Lyscholm-type screw blower if flat boost with good efficiency is the goal. - Beau

As far as the "redline" or boost limit on a supercharger, obviously you wouldnt want to use a pulley that would exceed that limit

Yea, but thats exactly the problem...At 11 psi, Im coming within about 4000 rpms of maxing out the blower...You wouldnt want to reduce the headroom much more than that.

Damn, that is getting up there. So whats the max PSI you can run on that Vortech in your car?

Anyways, thanks for the posts guys, I didn't think it would work, but now I know why.

Originally posted by paul e


Yea, but thats exactly the problem...At 11 psi, Im coming within about 4000 rpms of maxing out the blower...You wouldnt want to reduce the headroom much more than that.

Damn, that is getting up there. So whats the max PSI you can run on that Vortech in your car?

Well, its supposed to be capable of something like 20 to 25 psi. But, Im nearly maxed out in terms of permissable blower rpms at like 11.5 psi. Obviously on different engine configs, it can make alot more before reaching its own redline, but not on our cars.....I havent worked it out yet but my guess of what be max is around 14 psi on our cars tops.

I'd imagine that the max psi of the centifugal is more governed by the max FLOW. On a smaller engine, you may be able to make 20-25 psi. Also on a larger engine, you might max out at 10 psi.

The Vortech used in those kits is probably sized very well for the NORMAL boost levels. Since Paul is not NORMAL, he is getting close to pushing the limits of that particular compressor. Don't know that I have seen anyone with a low compression centrifugal setup at high boost yet. It would be a monster up top, but a horrible dog below 4k...

BTW Paul, :tongue

I am up at 1AM working on my "Project" and I am a bit punchy!!!

Steve

its a good idea.. but i dont think it would be that simple...

Since Paul is not NORMAL :b_blue:

I have not read all the replies so if I repeat stuff, oh well.

A compressor wheel has a top speed that it can be spun at. You dont want to exceed this. Something about the vanes going supersonic. Or something like that. And possible reversion.

You are confusing a wastegate with a blow off valve. A waste gate vents exhaust pressure to prevent a turbine from spinning any faster.

A blow of valve will vent the intake pressure to atmosphere. This is generally not good for a engine equiped with a HFM air sensor. It will cause the engine to run overly rich when it opens.

A bypass valve is the method for venting intake pressure on an HFM eequiped engine. It vents pressure back to the intake of the compressor reducing the flow rate through the air sensor.

The main function of the BOV and bypass are to help the turbo shaft maintain speed between shifts by reducing back pressure. A supercharger really does not need such things since the shaft is directly coupled to the engine speed.