Flatbed24v

I know that the turbo shaft can reach speeds of 120,000rpm - 260,000rpm but how much torque does it take to get it up to that speed and how much does it take to keep it there? What is the breaking point of the shaft realitive to torque?

sheriffav8r

Both shafts are pinwheels spun or being spun by air. Torque is only relative as to the end of the blades. It is more akin to constantly pushing an arm around for a period of time as opposed to a single torque moment spinning the arm. That's where you get spool up times (think water pressure coming out of a hose and then putting your finger over the end to create more pressure but less volume). Add temperature, gas constants, and several other things into the mix and it gets sticky. The breaking point would be when the blade material fails in any way or when one side of the shaft stops spinning (and the other side tries to keep spinning). I believe torque values could be obtained in a general way by measuring the pressure coming out of the exhaust and applying it to the moment of the turbine blade tip. Unfortunately, there are air entrainment and turbulence principles that go well beyond my three brain cells attempting to solve. A competent fluid dynamicist would be the one to ask.

So my answer would be: 4.

Andy505

Flatbed24v

Thanks for the reply ^^^^ it's beyond my thinking !!! I just don't know what the air resistance is on the intake side(would this be boost pressure?) that the exhaust side has to over come( I figure that number would be a torque number since it's applied to a round moving object) to spin the shaft that spins the intake wheel.(would drive pressure be relivant to this?) I am just a avg. guy with an idea of a stand alone turbo system that I am trying to build and need help to figure some things out.

Andy505

There are superchargers that are basically the compression side of a turbo spun by an electric motor.

CamperAndy

That would be grossly inefficient for an application like our trucks.

Flatbed24v

Ya my idea is a little different, it will put the driver in complete control of the turbo. So is you want 40psi at idle you can have it, if you want 40psi threw the intire rpm range you can have it, if you want it to be progressive you can do that to

Andy505

I've only seen them in the local junk yard on an old BMW or Porsche...it was an inline 6 though.

DodgenIt

One of my buddys was telling me about a thing his friend was tryin to get goin kinda like that.
It was almost like a mix between a turbo and super charger.
He was designing a air tank system that would shoot air into the exhaust side through a second port other then the exhaust manifold, and the trigger being connected to a switch that he would trip, as soon as he started to get on it.

The result was instant boost, rather then waiting for the exhaust to spool the turbo for boost.
And the tigger didnt exactly need to be tripped when he started adding fuel, he was just nevious as to what it would do with no fuel added with the air.
So really, he should be able to build atleast some kinda lbs even at idle.

Havent heard how its goin lately, but pretty cleaver if you ask me.

2500superram

maybe if the system could add some fuel at the same time.lean=boom(bye bye motor)

sheriffav8r

I think the idea would work, IMO. You would have to find a good place to put your air bung so you get a straight shot at the turbine wheel. I also don't know what kind of psi the exhaust puts out. Spooling it early wouldn't really do much since I bet you couldn't get it to turn very fast unless you had a very large air supply.... You could also set up an air tank/compressor set at a certain pressure with a switch that would inject compressed air directly into the air horn. That would need to be a very large amount of air and would need to be added when the turbo was slightly spooled to prevent back powering the turbo compressor.

I did a little more math and would like to update my answer above: 7.

BigErksG2

Blower on demand...

http://www.youtube.com/watch?v=5xE3m5PHCIE

CamperAndy

Hitchhiker's guide to the galaxy, says 42.

sheriffav8r

I stand corrected. I was only off by a factor of 6....

Ronco95

It's not uncommon for drag racers to inject nitrous into the exhaust upstream of the turbo housing to make boost on the starting line with the engine "unloaded". They do leave the line hard too!