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Dr Wheelspin Rh.D.
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Supposedly you want the rough surface on the intake side to keep some turbulation which is supposed to help keep fuel atomized.
 

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Bishop92T said:
Supposedly you want the rough surface on the intake side to keep some turbulation which is supposed to help keep fuel atomized.
BUT we have port injection. Polish it up to the injectors and smooth it afterwards. My personal opinion is that you should only POLISH the exhaust ports and mildly smooth them. dont port match exhaust ports with the exhaust manifold.
 
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The turbulation is to swirl the mix inside the cylinder to help fill the void. Ideally a really solid porter will induce a swirl through porting to create this vortex of air. Leaving the intake rough adds drag while accomplishing the same task less effectively.

Why would you say NOT to port match the exhaust side? You want as much exhaust velocity as possible to spool that turbo up quickly??
 

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Verrrry nice!
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Discussion Starter #8
thanks all for the input, the head i bought is ported intake and exhaust, i thought that sounded kinda corny not to do the intake, mine is smooth as a babys ass on the exhaust which prevents carbon buildup, its smoother b4 injectors like p5150 says, the guy did a great job in my opinion if any one is lookin for head work , i'll give his address/#
 

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Dr Wheelspin Rh.D.
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You want exhaust to come out of the engine as quickly as possible. There is no need for swirling/mixing on the exhaust side, just the quicker it's out the more gases that will hit the turbo.
 

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wastegate hose is pulled
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Not gasket matching the exhaust side is supposed to leave an anti reversion lip, since the pre-turbine exhaust is under more pressure than the intake this idea may have some merit.
 

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Why would you say NOT to port match the exhaust side? You want as much exhaust velocity as possible to spool that turbo up quickly?? [/B]


I didnt say it originally, the guy that does all the port work for Bullish Racing did.

Like volumes of gas at a similar temperature will have more pressure - which corresponds to higher velocity - in a smaller container. You simply get more flow by not opening up the exhaust ports on the head. Also take notice to the stock configuration. The size difference of the exh. ports/exh. mani compared to the intake ports/mani is noticible. I think toyota did that for a reason.
 

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ummmm...what I think you were getting at: the same gasses will tracel at a higher velocity in the smaller tube...not higher flow.

Ideally, for high power applications, you want the exhaust ported and polished to allow for more flow at the upper end, but you want to keep the step to a larger primary tube on the manifold. The % difference in size from the stock ports to tubes should suffice for the reversion dam even with larger ports. Now, that also means a custom manifold...For quick spool, just polish the ports, but know that you won't gain much at the top. The whole debate about making more power, or just moving the power around in the range thing applies here.


Bob
 

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25psi = 14" brakes :)
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I was reading a porting article, and the guy who ports some very powerful 2JZ motors noted that a step in size from the head to the exhaust manifold does the anti-reversion thing, and improves power.
I'm going 1mm oversize, so will match the manifold to the gasket, and keep the head port about 1 mm smaller, to retain the lip, but also increase the size of the port some for more flow.
The exhaust manifold porting and coatings should improve flow there too. (Same with the coatings in the exhaust port.)
Speaking of coatings, they have a very smooth one for the exhaust side, and a textured one for the intake side... :)
 

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hey guys I think what I said in my article has confused some, let me clarify. Reversion occurs when exhaust gases try to revert back into the intake port when the intake valve opens, this usually occurs during overlap-when both intake and exhaust valves are open at the same time, this (reversion) contaminates the intake charge. To combat this problem, we will not port match the INTAKE manifold to the gasket but leave it just a tad smaller.

As far as porting a 7m head, I just did one yesterday for Turbo magazine and can tell you the exhaust side needs more attention but do not be leary of a ported intake side unless it was really hogged out because this sometimes creates drivablity problems.
 

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Thanks for the clarification Dave - I must have not fully understood the explination you gave me. Im still waiting to see how the head that you ported for me is going to run with a bigger turbo.

To all that dont know about HeadGames, I can personally attest that Dave's work is top notch. Listen up.

Later - Cade Peterson
 
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