# Mandrel or crush bends



## Slow 96R (Jul 18, 2002)

OK I plan to do a 2.5 inch random cat to a 3 inch back pipe. My ? is how detrimental is it to go mandrel vs crush. The shop guy I spoke to said his cruch bends have hardly any wrinkels at all because of the size. What do you think? Anybody have experience with either? Also is there a big lost going 2.5 inch cat vs a 3 inch? Joel


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## Boosterwitch (Apr 15, 2002)

Mandrel bends are much much better.

What size is your downpipe? What size turbo? How much boost do you plan on running?


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## Slow 96R (Jul 18, 2002)

Boosterwitch said:


> *Mandrel bends are much much better.
> 
> What size is your downpipe? What size turbo? How much boost do you plan on running? *


I have a 2.5 inch downpipe to open cat right now. I know I cannot pass emissions here in MD. so I have to get a cat. I'm running the stock T28. I would like to run 20 psi. I have my profec B set @ 15-16 right now as my high until I get my walbro 255 fuel pump. I'm looking to achieve 300 whp.


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## Sr20 B12 (May 1, 2002)

Slow 96R said:


> *I have a 2.5 inch downpipe to open cat right now. I know I cannot pass emissions here in MD. so I have to get a cat. I'm running the stock T28. *


I don't know what the emission requirements in MD are but my friend failed the NY emission with his GTi-R det & 3" with a cat. As a matter of fact the only thing he pass was the gas cap check and safety requirement.



> * I would like to run 20 psi. I have my profec B set @ 15-16 right now as my high until I get my walbro 255 fuel pump. I'm looking to achieve 300 whp.*


20psi on the T28 is really over stressing it and isn't going to give you any real hp gain (turbo is on max). My uncle ran his T28 at 15psi daily with 18 - 20psi @ the track. It was good for awhile and got him a 12.3, but that turbo did not last long. When he took it off to put on a S15 unit, he saw that the compressor side was cracked so deep, he could see though it! The high boost caused it to get too hot and crack.

I wouldn't go any more than 18psi at the track with 100 octane fuel and about 12psi daily. 

-Mario


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## Slow 96R (Jul 18, 2002)

20psi on the T28 is really over stressing it and isn't going to give you any real hp gain (turbo is on max). My uncle ran his T28 at 15psi daily with 18 - 20psi @ the track. It was good for awhile and got him a 12.3, but that turbo did not last long. When he took it off to put on a S15 unit, he saw that the compressor side was cracked so deep, he could see though it! The high boost caused it to get too hot and crack.

I wouldn't go any more than 18psi at the track with 100 octane fuel and about 12psi daily. 

-Mario [/B][/QUOTE]

I actually run stock boost daily. There's no where on the street to run anymore than that. I'll stay @ 18. Thanks for the heads up


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