Just wondering if anyone has though of putting an exhaust iris on/in the exhaust just after the turbo? I would think that it might allow for better spoolup without sacrificing topend, because:

1.) Closed iris = more backpressure, which should help spoolup
2.) Open iris = minimal backpressure (exhaust size dependant) = better flow

For reference, check out the exhaust iris on the F14 engines (near bottom of the page): http://www.aircraftresourcecenter.co...at/walk169.htm

l8r)

 

Put Down the Crack and Step Away From the keyboard.....

 

Why?

l8r)

 

Wouldn't be worth it..The only thing you will gain out of something like that is faster spoolup, and I think you would want it before the turbo to get higher velocity to spin the turbo initially, like porsche's variable geometry turbocharger system.. So yeah, put the crack pipe down

 

The complexity, and lack of reliability would greatly outweigh and perfoamance gains........
It would be easier to do a sequential twin turbo.......

 

that is called variable turbine nozzle technology... it's already been discovered and no one uses it.

 

Ah well, looks like I'm about 20 years too late and more than a few dollars short ... again. [exhales]

l8r)

 

well seriously... it's a damn good idea... just no one uses it :\

hence we're stuck with what we have

 

Actually you do hear about those on diesels.

 

yeah

 

 

How in the hell does increased "back pressure" (which means less of a pressure differential accross the exhaust turbine) help it to spool faster?!? That goes against physics. More differential in pressure accross the turbine causes the turbine to spin faster. Thus, having a completely open exhaust end with no exhaust tubing would spool fastest I would think. (but louder than hell)

The irises on the F14 help to focus a jet of hot gas into a smaller diameter, thus the jet exhaust is at higher velocity and gives more thrust....but this has nothing to do with our gases venting into the downpipe....unless you're planning on using your exhaust as thrust to move the car forward. Good luck with that.

 

Exactly. It's for more thrust by keeping exhaust gas velocity high in a jet since the exhaust gas velocity is what propells the jet.

In a turbocharged application, you'd want an iris before the turbo ... IE: variable nozzle turbine (VNT/VGT) ... which has already been done. Good stuff, but fairly different principle.

Ater a turbocharger, you want as little backpressure as possible. (Though that doesn't necessarily speak for downpipe diameter.)

 

Very impressive.....Not only do you teach others here about the mechanics of turbines but you do so without insulting them. Kudos to you...

Chris

 

Exactly. Unfortunately there are not many people on these boards that can do that.

As to the haterz ... I fart in your general direction... j/k

l8r)