Limiting high rpm boost

[Procharmo]

I'm very happy with my Procharged set up. But I would like some opinions on a this potential modification.

Some petrol heads have with limited success installed waste gates and boost controllers post centrifugal compressor in an attempt to limit high rpm boost and increase low rpm boost. This results in a have your cake and eat it scenario, crazy boost off idle and you can still rev to the moon. If you use a roots or screw you'll get into heat issues.

The main con with the waste gate method is the supercharger is still working to compress air that's being dumped by the waste gate making the whole combo less efficient than the correctly sized centrifugal for the same maximum boost with no bleed off. (Parasitic losses.)

If a larger blower is used and restricted at the inlet then it will only work to compress the ingested air thus lowering total max rpm boost. Currently available restrictor plates are difficult to change over.

If we could introduce a variable electronic restrictor pre-compressor and control its attitude we could map the curve to give constant boost fromm 500 rpm to 7000 rpm if the blower were big enough.

I wish I had thought of this before.

1) SBC at 350 - 400 CI.

2) F3-A 117 Procharger head unit at 2800 cfm or 2100 hp with 5.5" inlet.

3) Electronic valve like the electronic QTP 4" cut out modified to 5.5" and geared to move fast enough.

https://static1.pt-content.com/images/noimg.gif (http://img15.imageshack.us/my.php?image=qtpcutout.jpg)


4) Controller calibrated and mapped to adjust the valve to show contant boost. And adjustable from the cockpit like the Turbo boys!!

Lastly to further refine this imaginary product we could build in a pre compressor methanol injector bracket.

https://static1.pt-content.com/images/noimg.gif (http://img7.imageshack.us/my.php?image=waterinjection.jpg)

Just an added feature to enable the blower to act bigger and cool down the charge as well. Originally used in WWII on German fighters just like superchargers and nitrous oxide. If injected in a mist from a correctly sized nozzle it will vaporise before exiting the supercharger and not puddle in the intercooler if present.

Any comments welcome.

[68Formula]

Wouldn't it be easier just to use a smaller charger?

[GetMore]

I'm not sure you will gain any efficiency by limiting intake volume versus releasing excess pressure.
I think adding restriction to the intake side will cause drag. I may be completely wrong though.
Some kind of blow off valve releases pressure, so the compressor isn't actually working had at that point, since it's not pushing the air. No doubt there is work being done, and it's still using power to spin the compressor, but I don't think it's as much as during full boost.
Most likely your idea is more efficient, but I wonder how much. I also wonder how much cheaper it'd be to use a properly sized supercharger.

Here's another idea: Install a reverse-operating centrifugal clutch mechanism. Something that lowers the ratio instead of increases it in relation to rpm. You could have it stay fully engaged up to a certain rpm, then start decreasing the ratio to limit boost as the rpm increases.

[Procharmo]

"Wouldn't it be easier just to use a smaller charger?"

The proper sized centrifugal supercharger will give for example 10 psi at 6000 rpm 5 psi at 3000 rpm and 1 psi at 2000 rpm. If you used my idea you could have 10 psi at 2K and 10 psi at 6K.

Jason, the reverse clutch mechanism may work but could be more expensive and prone to reliability issues. But if it could be realised it would be the next evolution in centrifugal blowers making all others obsolete. After all Procharger did increase their step up ratios from the 3.05:1 of the P600B to 4.10:1 D1SC and 6.24:1 F3 to dominate the market.

My idea takes into account that the blower compresses the air inside the scroll and the pressure is held in the tubing from the blower outlet to the intake valve. The pressure relief valve/waste gate method will still require work to compress air. The blower would be over sized for the motor so we may well be taking about an F3 capable of 4000 cfm. I think the (SBC) 450 - 500 hp engine will suffer trying to turn it without restricting its inlet.

The reason the losses of compressing blow off/surge valve air is not noticeable on our Procharged rides is we very rarely increase rpm to 4K or 5k whilst cruising (Valve open). When we do we don't need much power so if there is parasitic loss we wouldn't notice or care.

4K or 5K at full throttle we expect to be pinned back. But if the boost is being released then we are down on power for a given boost pressure. (ie less than the same boost pressure in a closed system).

Realistically this is something I could implement using a 4" electric cut out on my F1C 4" inlet using a 3.4" pulley. The smallest available from Procharger.