Why Boost is Bad

Technical discussions
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Stuart
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I'll change the title then :D

Post by Stuart »

So what is the difference? :poke:
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duncan
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Post by duncan »

read and absorb the above ^^ ;)

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Stuart
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Post by Stuart »

You didn't understand it either did you :)
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frayz
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Post by frayz »

Gerry H wrote:Never one to skimp on an explanation is Pat.

Why use only one word when seventeen will suffice :D
Ha ha ha ,

Pissed myself laughing when i read the Gerry :D

Ive already read all this lot on 22B lol.

Dont worry Dunc, im fishing for facts on a 2.5 build too :D
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duncan
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Post by duncan »

Yep - I understood it Stu :D

Summary: 1.5 bar on a small turbo does not mean the same as 1.5 bar on a big turbo as the big turbo will not have as much back pressure casuing the boost to rise. Too big a turbo and back pressure is not enough to spool the turbo -> hence barsteward. There is always a balance.

This was part of a long discussion and thought it would be useful to some people that like to know how things work and/or why things work.

Gerry - you're right 3's up doesnt read right :pmsl: but I know what you mean :)

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Bladerider
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Post by Bladerider »

Key item missing in your summary Dunc,

1.5bar boost on a GT2530 is not the same thing as 1.5bar boost on a T51SPL !!!!

:D :D :D
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Gerry H
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Post by Gerry H »

It'll either develop into a marathon or be ignored. Should be interesting either way.

In fairness to Pavlo, I don't think he's a big fan of the 321 and is another who says what he thinks, if somewhat abruptly sometimes :o .
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duncan
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Post by duncan »

Bladerider wrote:Key item missing in your summary Dunc,

1.5bar boost on a GT2530 is not the same thing as 1.5bar boost on a T51SPL !!!!

:D :D :D
Exactly :thumb:

That was precisely the question I wanted to find the answer to.

I was thinking of the inlet manifold as being a closed chamber where air pressure (boost) is measured. Therefore 1.5bar of anyone's money would be the same. Obviously this isnt the case due to the dynamic nature of the inlet and that boost is through the engine and takes into account wastgate size. The T51 (which I presume is a huge turbo) creating 1.5 bar would be flowing substantially more air if the engine could digest it.

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Post by PussyCat »

The reason it is different is due to the compressor/wheel sizes, not the turbine thoguh obviously you have to have the gases spinning the turbine side correctly ;)

In base terms a T25 will not move the same CFM of air as a T51, teh compressor is larger as is its AR. and inlet thus is can move more air easier that a turbo with a small restrictive compressor.

CFM is the measurement of air moved, again in short the larger the compressor & wheel the more air moves, it may take a T25 15psi to move (guess) 305cfm but the larger T51 can move this at say 6psi due to its compressor and wheel size and maybe 900cfm at 15psi


Hope that makes sense :)

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