Extrude Hone Tubular Exhaust Manifold

casuprock · Jul 12, 2011

I'll be having a tubular exhaust manifold fabricated soon.

Has anybody extrude honed (abrasive flow machined) their tubular exhaust manifold? I'm curious to see what differences anybody has recorded on pressure drop versus runner length. It's clear that the process will decrease the boundary layer effects and improve the pressure drop by up to 20%, but surface roughness and turbulence calculations only go so far. Anybody got experience?

The rest of the engine flows freely- 2.3L, ported head, JMF intake mani, Q45.

RvlutionMtrsprt · Jul 12, 2011

I'd think if the manifold is made properly that extrude honing will be a waste of time and money. I'd be willing to bet that nobody here has ever extrude honed Shearer manifold or anything else of that caliber.

bmoha7321 · Jul 12, 2011

Plus you only have a certain thickness of sheetmetal to work with. Extrude honing would round edges and weaken it?

1gDSM4g63 · Jul 12, 2011

Why would anybody their tubular manifold? They ONLY hone cast iron manifold. They're high flowing manifold and honing tubular manifold is USELESS because it doesn't match the cylinder ports.

casuprock · Jul 12, 2011

Surface roughness of the tube pieces, how the gaps match up inside, and weld quality are all critical. The latter two are what you pay for in a high end manifold.

Just to see if there are any gains to be had. It might be interesting to see expensive manifold X versus honed expensive manifold X. Assuming the welding is perfect and the tubes are matched perfectly, tube surface finish is the main thing to improve- so a light abrasive hone might not be a total waste.

Ferrari people do it... maybe that implies you have to have money to burn to mess with these small gains.

1gDSM4g63 said:
Why would anybody their tubular manifold? They ONLY hone cast iron manifold. They're high flowing manifold and honing tubular manifold is USELESS because it doesn't match the cylinder ports.

It matches the cylinder ports if you have the flange machined to taper into the runners.

SHEARER_TSI · Jul 13, 2011

Ferrari people also pay $8000 for an axle back exhaust.

casuprock · Jul 13, 2011

SHEARER_TSI said:
Ferrari people also pay $8000 for an axle back exhaust.

Hah, but it's only fiat money (bad pun; Fiat made some Ferrari manifolds) :shhh:

Before considering the cost, I'd like to know if anyone has evaluated the change in pressure drop or onset of turbulence before/after? It is a relevant question.

99gst_racer · Jul 13, 2011

I've never heard of anyone doing this on a pipe manifold before. But I'd be willing to bet that there's an unmeasurable performance difference when testing before and after on a well-built manifold. Surface roughness isn't too much of a concern with schedule pipe. A good, experienced pipe fitter can fit joints with little to no overlap, and a good backpurged weld won't come through the joint seem at all. On the last sch-10 manifold that I built, I spent 12 hours just for fitting and tacking to make sure all joints matched up as best as I could possibly make them. I just don't see much room for improvement on a good quality manifold - at least not enough to justify the cost of the extrude hone process. I'm sure it could definitely improve a poorly constructed manifold though.

casuprock · Jul 13, 2011

99gst_racer said:
I've never heard of anyone doing this on a pipe manifold before. But I'd be willing to bet that there's an unmeasurable performance difference when testing before and after on a well-built manifold. Surface roughness isn't too much of a concern with schedule pipe. A good, experienced pipe fitter can fit joints with little to no overlap, and a good backpurged weld won't come through the joint seem at all. On the last sch-10 manifold that I built, I spent 12 hours just for fitting and tacking to make sure all joints matched up as best as I could possibly make them. I just don't see much room for improvement on a good quality manifold - at least not enough to justify the cost of the extrude hone process. I'm sure it could definitely improve a poorly constructed manifold though.

Thanks, this is the kind of info I wanted to know. :thumb:

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Extrude Hone Tubular Exhaust Manifold

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