Screw Overdrive ??

What's the highest O/D that anyone has tried with a C or D, and what sort of max compressor shaft RPM did that turn out to be? How much RPM can a blueprinted C or D tolerate before mechanical or efficiency issues rear their ugly heads? Just curious. 228% seems to be a popular ratio talked about as a higher level for OD, but have people tried pushing past this? How'd that go?....... Thanks.

 

PSI posts their max RPM on a screw to be 26,400 RPM. Multiply the RPM by the overdrive and that will tell you if you are within their limits.

 

so 26400rpm
at 10500 x 2.50= 26250 anybody tried that

 

In this case my upper is a 37 tooth (could even be bigger if I wanted) and the fuel pump does not drive off the cam centerline so no lower constraints in terms of pulley diameter. I've heard that a C or D can be spun up to 30K without mechanical issue, but I don't know what the VE and adiabatic issues are like at higher speeds. What's TAD running for ratio these days? Outlaw PM at 228%, shifting at say 10,500, would imply peak shaft speeds of around 24,000 for the compressor.

 

They are better than the PSI? Will have the DMPE absorber too.

 

So I'm curious now......

What is the theoretical max HP potential of a "C" on a typical alcohol screw V8 with no rules in the way?

Maybe a better related question would be, what's the most HP a person has ever made to date with a screw compressed methanol v8?

If an offline answer would be prefered, please drop me a line at whome@look.ca

Thanks.

 

IMO there is a reason that SFI has a max overdrive. Just abide by it and everything will be fine, as it is for EVERYONES safety.

Tom

 

I saw Will's comment about 2.28 ratio earlier and to be honest I'm not familiar with the origin of that SFI spec or whether it actually even exists. I'll have to go digging further on that.

If you think of it though, a bald spec of 2.28 does not really control the compressor shaft RPM. What if an engine spun 11K, 12K, etc...?

My pondering is how much "might" a person be able to make with a "C" safely, knowing that for SFI cert these things have to live for literally minutes at 30K RPM?

What I do not know is what the VE and adiabitic efficiency is like at these upper RPM's, assuming of course that the inlet is not throttled in any way.

So, back to my question, who's gone off into the netherlands of RPM's with a screw and how'd that go?

Thanks.

 

We made 72# @ 150% on a sand drag car a few years back. 10,200rpm. It was using a C rotor "gizmo" blower as Drazy called it.

 

I must ask where you found that the test is for minutes at 30,000 RPM? I am just curious that is all.

Here is what I found about the subject of SFI and Screw Superchargers.

http://www.sfifoundation.com/wp-content/pdfs/specs/Spec_34.1_012902.pdf

Thanks,

Tom

 

Hey thanks for that Tom, I'll read it in more detail tonight. The 30K thing came up during a conversation with Roger Olander a few years back. That's all that I know about it.