Alright tech-junkies: Extrude Hone vs. Port and Polishing, which has more benefits?

[Alex (lil' is 300)]

Going to have the intake manifold modified in one way or another. I originally planned on comtacting VAST to have them port and polish, but have since learned tonight from talking to an AW member that there is an alternative called Extrude Hone.

I did my homework, researched and it seems like pretty cool technology. Essentially does the same as p&ping. But as long as we're on the subject, which has more benefits?

Here's a fact: Extrude Hone would cost almost two-three times as much as a Port and Polish would. So, is it worth it?

[golfrsi]

be very nominal at best if you just do the manifold and nothing else. especially on the already better flowing 01.5 unit. I've debated it as well (and actual just put my spare manifold on ebay cause I decided against it) but came to the conclusion that unless I went the whole 9 yards (gasket matching the manifold and the heads, the TB, etc..) it prob would not be worth the expense even with a potential gain.

[Mike2kS4]

I hand ported my manifold like Mike would do and I can't argue with the results.

EH does have it's advantages in tight passages... my turbine housings are EH'd.

[Blitzkrieg]

• http://pictureposter.audiworld.com/users/18896.phtml

[Hal_TT::CBP]

Honestly EH isn't worth the money on these and as far as port/polishing I'd just do the bell mouths and any angle/surface where air has to turn or hits a flat area in general. You want the surfaces smooth at transitions to keep directional velocity high. All that rough cast surface tends to slow things and create turbulence at high flow rates.

Mark at ASP did a scoop RS4 intake bottom on a car that was pretty unique, don't know how well it worked. I think I'd like to try a pent roof designed insert in the plenum ie 90deg tapered rooftop to help with directional changes. Would provide a flat surface area for assisting flow into the venturi/runners vs depending on vacuum cavitation to influence/direct airflow.

[whoizrob]

Most Extrude hone type processes involv forcing an abraisive paste through the mani thereby "sanding" the inside of the mani. You get a smoother finish, great but what about air flow "quality"?

Sometimes you want air to turbulent airflow to mix fuel and air, sometimes you want that boundary layer of air to "unstick" from the walls of the mani, sometimes you want it smoothed out for nice laminar flow. Sometimes air flow needs to be coaxed through certain constrictions and turns and the passageway can be shaped to improve that flow.

Will extrude hone provide a smoother mani interior? Yes. Will it give you that attention to detail in trouble areas of the mani and improove the flow you can get out of it? Yes. That's why it costs money for a good head job porting job. It's not just the labor of hand grinding somthing, it's the expertise you are paying for and the time on a flow bench. It takes a lot more than making holes big and smooth to improve air flow.

HTH,

Rob

[Imolavirus@BuehnEngineering]

doing the porting/polishing by hand allows you to focus your attention on certain areas that need to be reshaped or smoothed. EH is just making the surface smooth for a nice laminar flow. Optimum would be to have the manifold ported and then EH'ed for the "polishing" part.

This is why i vote for port/polish on turbine housings as well. There are certain areas that are horrible with the stock casting. With porting by hand you are able to reshape these areas how you'd like. Even a full EH won't reshape these areas, just smooth it out. EH will get into some areas that you are unable to get to by hand though so there is some benefit there.

[PhiS4]

[ModifiedA4]

i had my exhaust manifold EH'd. the nominal diameter of the passage ways doesnt change too much. and they dont gasket match or anything.

do any porting BEFORE you send them the manifold. do any gasket matching AFTER.

[Mark@AutoSpeed]