Crush vs Mandrel

["Graydon D. Stuckey" <graydon@apollo.kettering.edu>]

On Mon, 18 May 1998, Ron Wood wrote:

> One thing to take into consideration is that most muffler shops can not
> do mandrel bending on the tubing. The typical muffler shop "crush 

Indeed.   I havenot yet seen a mandrel bender at a muffler shop.   They 
all use crush benders.

> bender" will greatly reduce the flow of the tubing, you would probably 
> have to go to at least 2 3/4'' tubing to get the same flow as a mandrel 
> bent 2 1/2" system. I would make sure that the Blaufernugen system is 

I don't think even that would do it since the ripples on the inside wall 
would screw up the flow big time.   And, Gross, I think the ripples are too 
large relative to the inside diameter to have any positive boundary layer 
effect.  The big problem I think, is that you are squeezing the gas flow 
down, and then letting it expand again.  By definition, its a throttling 
device, and adds inefficiency.

> mandrel. It is possible to fabricate a system using mandrel u-bends, but 
> it is time consuming (expensive), this is what we do for all the 3" 
> turbo systems. 

Ditto.   I do the same, but it is very time consuming, and the materials 
are expensive.  Results are very well worth it though!   Peace of mind is 
great too - 3" pipe all the way back from the turbo to the back bumper - 
you just _know_ it has to help!  You can feel it though - the engine revs 
more freely and it makes alot more power.

> We've had godd luck with the Magnaflow mufflers-well 
> built, low restriction & reasonable noise levels.

Hmm, I'll check 'em out if I get a chance.

Later,
Graydon D. Stuckey
lotsa 3" pipe in the garage beside the TIG machine :-)