Max Exhaust Port Width
04-28-2004, 06:42 PM
#14
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Join Date: Oct 2002
Location: Memphis, Japan
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Ive come to the conclusion that North American tuners dont do adequate work with the exhaust ports compared to the intakes on average. Its nothing like the work done in Oz or Japan. It also seems the solution to everything here is a bigger turbo or more boost, not making the most of what you already have.
Very well said........I totally agree.
Going really big on exhast can really change your low-mid range. I think thats why many people here in the US dont port big and then just add more boost for the big hp numbers. Its all a compromise no matter what you do.
I don't think it hurts the midrange at all. My ports looked similar to the one Ted is showing here and that is using a TDO6H-20G #17 exhaust side. You can see the Dyno in this post.
Exhaust Ports
My midrange was excellent. The Shops here in Japan definatley use larger exhaust ports than people in America.......you would be suprised how big they go. They do however warn about going to wide.
04-28-2004, 06:52 PM
#15
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Location: Savannah, Ga
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Exhaust porting is very very sensative. I did the exact same exhaust port on 2 engines, except it was located slightly lower in one of the engines. The midrange and low end on the one with the lower exhaust port was much stronger, with no apparent loss in the top end. I was amazed at just how much of a difference it made in drivability.
04-28-2004, 07:31 PM
#16
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Originally Posted by mazdaspeed7' date='Apr 28 2004, 03:52 PM
Exhaust porting is very very sensative. I did the exact same exhaust port on 2 engines, except it was located slightly lower in one of the engines. The midrange and low end on the one with the lower exhaust port was much stronger, with no apparent loss in the top end. I was amazed at just how much of a difference it made in drivability.
04-28-2004, 08:17 PM
#17
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Thread Starter
Join Date: Jun 2003
Posts: 406
Thats an awesome looking port,.. I just measured with a caliper and a 2.25 inch wide exhaust port leaves almost exactly 1/2 inch on each side, so it looks like the i heard bout right...Anyone with a degree wheel know how many degrees per milimeter up or down it is?
04-28-2004, 09:32 PM
#18
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Originally Posted by j9fd3s' date='Apr 28 2004, 08:31 PM
thats just from less overlap, some is good but you can have too much (iHmo)
Now, take old school pushrod V8's. They need a lot of overlap to make power at higher rpms. But they lose a lot of low end from the overlap, and drivability as well.
I pretty much only port down. I take the top edge up to the top of the stock bevel, and then bevel that. I get enough extra overlap from the early open SP. Then I just port down and out.
04-29-2004, 02:00 PM
#19
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Originally Posted by mazdaspeed7' date='Apr 28 2004, 12:23 PM
I like your definition of mild 
It widens significantly, but I don't drop the port too much - maybe 1/4" or so.
These are the Stage II exhaust ports - dropped almost 3/4".
Comparison to stock port
-Ted