Headers

[Hedge_imp]

So I am researching headers and cannot get any concrete explanation for the difference in Machine bent headers vs Hand bent headers, besides the obvious price. What makes one better than the other?

[the Ferret]

Hedge, I could be wrong, but I believe the smoother the bend the better the air flows. hand bent pipes use smoother radii to flow better. Whereas machine bent pipes use a more squared off bend, therefore less flow. At least that is what I have been told.

I could have that backwards according to this I found in google searching

Mandrel Bent Versus Crush Bent Piping

Another way to upgrade the exhaust piping from the catalytic converter back to the muffler is to have the exhaust piping mandrel (heat) bent instead of the conventional crush bending. As the name suggests, mandrel bends are achieved through the heating of the piping before bending whereas crush bent just literally mean that the piping is bent entirely by force. However, the main difference between mandrel bent and crush bent piping is the ease of flow. Mandrel piping keeps the pipe at a constant cross-sectional area throughout a bend which makes exhaust flow easier. On the other hand, crush bending deforms the pipe at the bend(s), which can restrict the exhaust flow. The disadvantage of mandrel bending is that it is relatively expensive, because of the costs involved in operating a mandrel bending heat machine.

I could find no reference on "hand bent" ..just Mandrel, crush and CNC

[Hedge_imp]

Hedge, I could be wrong, but I believe the smoother the bend the better the air flows. hand bent pipes use smoother radii to flow better. Whereas machine bent pipes use a more squared off bend, therefore less flow. At least that is what I have been told.

I could have that backwards according to this I found in google searching

Mandrel Bent Versus Crush Bent Piping

Another way to upgrade the exhaust piping from the catalytic converter back to the muffler is to have the exhaust piping mandrel (heat) bent instead of the conventional crush bending. As the name suggests, mandrel bends are achieved through the heating of the piping before bending whereas crush bent just literally mean that the piping is bent entirely by force. However, the main difference between mandrel bent and crush bent piping is the ease of flow. Mandrel piping keeps the pipe at a constant cross-sectional area throughout a bend which makes exhaust flow easier. On the other hand, crush bending deforms the pipe at the bend(s), which can restrict the exhaust flow. The disadvantage of mandrel bending is that it is relatively expensive, because of the costs involved in operating a mandrel bending heat machine.

I could find no reference on "hand bent" ..just Mandrel, crush and CNC

Funny - I fully read that before posting. I usually Google before I ask questions. Thanks for the reply. I will post the official word from Yoshimura as soon as they reply to my questions. I need to fully understand the difference between these pipes before I pull the trigger . . . Due Diligence!
[url=http://japan.webike.net/ps/yoshimura/#!search&p.ref=product-search&p.k=yoshimura&p.c=1001&p.m=311]http://japan.webike.net/ps/yoshimura/#!s...01&p.m=311

[the Ferret]

yea let us know.

The only thing I can think of is maybe mandrel bending means hand bending? and therefore it would have smoother bends, cost more and be better for performance.

At any rate looking forward to Mr. T's reply

[Hedge_imp]

yea let us know.

The only thing I can think of is maybe mandrel bending means hand bending? and therefore it would have smoother bends, cost more and be better for performance.

At any rate looking forward to Mr. T's reply

I emailed him yesterday morning - is he usually good about turnaround time on answers?

[Gumby 1100_imp]

https://www.youtube.com/watch?v=v8mMQbEkr8w

Here is a good video from Yoshimura on how they hand bend the pipe using heat. You will note a plug in the end of the pipe which is to retain the sand in the pipe that is used as a "mandrel".

As to "machine bent" pipe...this can be done with and without a mandrel, but generally, for the purposes of headers, a mandrel is not used on typical tube benders. The complex bends would make it difficult to remove the mandrel.

[Lord Popgun]

Hedge,

Mr. T is very good at returning emails. Just remember the time difference.

[Hedge_imp]

Word Gumby! Thanks

[the Ferret]

Super cool video Gumby. That was neat. Thanks for posting. Explains a lot actually.

[Motogeezer1949_imp]

Mandrel and crush bent can both be done by machine. They can be sand or water too. IMO the difference in price referred to comes from premium flanges, ceramic coated stainless steel rather than painted steel. The machine bent set I just installed on sons bike has perfectly radiused curves. Have not seen a hand bent set.