Turbo techie question...

[Darren S]

One thing Ive never been able to work out (in my small, fragile mind) is why turbo cars get a significant shot of power with relatively little boost pressure?

My Punto GT only registered 1.4bar on the dash, which was about as accurate as unaccurate things can get. In fact, the last turbo car I drove put a major smile on my face with a mere 1.2bar of pressure.

Can anyone explain, just purely out of curiosity, please?!

D.

 

[MATT BLACK]

depends on how big the impeller is and how fast it winds up. On the clio TT i originally had the K04 turbo running at 1.5 bar. Now ive fitted a VF34 subaru STi turbo which has a much bigger impeller and spins over a lot quicker - that only runs at 1.2 bar but has given me an extra 50 bhp

 

[Darren S]

Matt,

Its the pressure bit that I dont quite understand. If both turbos and superchargers are forms of forced induction against normally aspirated engines, how can they induce so much in terms of power gain with so little pressure?

Just standard atmospheric pressure is 1.0bar. How can increasing that by 20%, 40%, etc create such a surge of air & fuel mixture to make a turbo engine perform like it does?

Or does a 1.2bar reading from the engine actually mean an extra 1.2bar of pressure over standard atmospheric pressure. I.e - you get 1.0bar without the engine even being switched on, so when the turbo spools up, its adding 1.2bar (for example) to whats already there, making 2.2bar overall?



D.

 

[JAY172]

1.2 bar over atmospheric pressure. you will find a lot of pressure gauges zero on the gauge is actually atmospheric pressure 1000mbar

 

[Darren S]

Quote: Originally posted by JAY172 on 22 August 2005

1.2 bar over atmospheric pressure. you will find a lot of pressure gauges zero on the gauge is actually atmospheric pressure 1000mbar

Ah, now that makes more sense!

D.

 

[MATT BLACK]

lol - beat me to it.