Mandrel Bent vs Crush Bent

[Ricochet]

I know all the bigwig companies have mandrel bent exhaust sytems for smooth flow, but think about crush bent for a second. Picture a marching band or something, how they make those right/left turns all lined up straight. Well, the guys on the inside apex of the turn walk slower, while the outside ones walk faster, all keeping a straight line while exiting and going straight.

Now picture the airflow in an exhaust slowing down along the crinkles on the inside of a piping turn while the smooth side helps the outside gas keep up, and form a "straight line" on the exit, packing a full punch coming out the exhaust. I don't know, just a thought.

[crxlvr]

is this just for newbies? of was there a story associated with this.

[Ricochet]

no story, just sharing my thoughts. I know either way it's probably a difference of .0001 hp anyways... what u guys think?

[BLU CIVIC]

[Quoting The Matrix] He doesn't know [Quoting The Matrix]

[crxlvr]

as far as ive read mandrel bent piping always performs better than crush bent.

[Milliardo]

You might have something here. I'm reading up on the comparisons of headers for the D-series, found here: http://www.hadamotorsport.com/tech/review/dsemc/ Interesting in that one header design seems to feature a sort-of restriction. This is a stepped primary, found in the the Hedman Chikara 4-2-1 two-piece header. Note that the stepped primaries are not accidental restriction points, but are actually incorporated in the design. How are they restriction points? The pipe widens and then goes back to its original diameter, sort of like how the crinkles in crush bent pipes are. Strangely enough, this produces an improvement in velocity, as Ricochet noted. I'm not an engineer, so I really wouldn't know. Perhaps further tests might rethink the use of mandrel bent pipes and go back to a more older method of pipe bending.

[F23A4Racer750IL]

i dunno i would rather have the smoother flow vs the rougher even if there aint much of a hp difference. i think if the big time companies thought crush bent was better they would offer them.

[BullShifter]

Originally Posted by Ricochet

no story, just sharing my thoughts. I know either way it's probably a difference of .0001 hp anyways... what u guys think?

eleventeen HP's

The best exhaust is made from that ghetto flex pipe from parts stores

[Tofuboy]

Now picture the airflow in an exhaust slowing down along the crinkles on the inside of a piping turn while the smooth side helps the outside gas keep up, and form a "straight line" on the exit, packing a full punch coming out the exhaust.

Air does not quite move that way. When you are talking about how air is moving inside a piping, it's all about the degree of angle the pipe is made and the surface of the pipe inside where the air is "riding" on.

It is not the smoothest surface best when you are trying to make the air turn, it has to have a certain finish on the surface for the air to "grab" on the wall and turn on top of the degree of angle.

[Privatebigandrew]

the stepped headers are for improved velocity. After the exhaust exist the combustion chamber, it needs velocity too make it out the end of the pipes. Thus the step headers......they gradually get larger (usually three step) to get the exhaust out of the combustion chamber, then they get smaller to increase the velocity of the exhaust and allow it to exit the pipes. It has a lot to do with scavenging and the pulses of the exhaust (which i wont get into cuz thats another long story).

[Ricochet]

Wrong, exhausts get larger towards the muffler. Heat expands, and with larger diameter piping towards the end that makes it the only way to go.

[Privatebigandrew]

No i'm not wrong. What i described is the ideal header/exhaust design for scavanging and tuning the exhaust pulses. Pipes don't get larger towards the exit. Yes, as temperature increases so does pressure. But what you described makes no sence. The further the exhaust gets down the pipe, the cooler it gets, so there is no need for the pipe to get larger. It looses pressure as it gets down the pipe. Besides everthing i was talking about was involved in the primary and secondary section of the header, not the pipes.

[Privatebigandrew]

*i meant it looses temperature as it gets down the pipe, not pressure.

[jweller]

Originally Posted by Privatebigandrew

No i'm not wrong. What i described is the ideal header/exhaust design for scavanging and tuning the exhaust pulses. Pipes don't get larger towards the exit. Yes, as temperature increases so does pressure. But what you described makes no sence. The further the exhaust gets down the pipe, the cooler it gets, so there is no need for the pipe to get larger. It looses pressure as it gets down the pipe. Besides everthing i was talking about was involved in the primary and secondary section of the header, not the pipes.

this guy is right.

exhaust velocity is king. go take a look at any length of pipe with a crush bend and think about how it would flow. it's going to be turbulent as sh!t at the bends. turbulence kills velocity

the stepped headers also help prevent reversion.