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The Port Debate...

The Port Debate...

Old 12-20-2007, 04:30 PM
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Here's a question for all the engine guru's to discuss as i'm interested in what your responses are....

How many transfer ports do you believe is optimal and why?

There are a lot of engines out there these days, each with different port arrangments and i'm wondering if it's really nessessary to have a 5,6,7+ port sleeve when engines like the OS Speed or V-spec (i'm sure there's more) are doing so well with just 3

Are engine manufacturers making things more complicated than they need to be?
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Old 12-20-2007, 04:54 PM
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I was wondering the same thing because it seems like companies are trying to make us think the more ports the faster, but O.S. V-Spec is a good example of this being false.
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Old 12-20-2007, 06:01 PM
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isnt more ports faster why then are companys like os making 3 port motors confused
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Old 12-20-2007, 08:16 PM
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Originally Posted by johnkemp View Post
isnt more ports faster why then are companys like os making 3 port motors confused
I guess it depends on your school of thought.... most of my 2 stroke experience is based around motorbikes, where, to my knowledge, the only reason the ports have bridges between them is to hold the rings in the piston, otherwise the ports would be bigger and fewer.... Hence why i wonder if 5-7 ports is really needed in an engine with no rings?
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Old 12-20-2007, 09:56 PM
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well i know on-road typically has more ports (7-9) than off-road. on-road is more targeted for speed. I never seen any on-road engines less than 7 ports.
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Old 12-20-2007, 09:57 PM
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Less ports = more bottom end power, more ports = power in the upper RPM range.

If you got a fast high speed track more ports, if you have a technical track with many infield turns, less ports is better, unless you clutch the crap out of it.
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Old 12-21-2007, 11:40 AM
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Originally Posted by GenReaper View Post
Less ports = more bottom end power, more ports = power in the upper RPM range.

If you got a fast high speed track more ports, if you have a technical track with many infield turns, less ports is better, unless you clutch the crap out of it.
+1
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Old 12-21-2007, 10:21 PM
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Our 8 port 421b has more bottom end than our 21-5 with 5 ports.

Rex
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Old 12-22-2007, 03:26 PM
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Lets not forget about the 3 port OS Speed. It has a very fast top end and great bottom.
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Old 12-22-2007, 06:01 PM
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ports are just to change engine charecteristics. say you have an engine with loads of top end, you change the ports to allow some ofthat top end into the middle and bottom end.
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Old 12-22-2007, 06:10 PM
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Originally Posted by GenReaper View Post
Less ports = more bottom end power, more ports = power in the upper RPM range.

If you got a fast high speed track more ports, if you have a technical track with many infield turns, less ports is better, unless you clutch the crap out of it.
SO NOT TRUE !! There is more to ports than led to believe , and yes the
421Bs' are utterly insaine on the bottom to the point they are very hard to drive when the track is slick. Modified they are simply stellar but not as good on fuel as say an OS.
So the port debate rolls on.
Now as for Novarossi , it's all in the crankcase and cranks that really determine what you will have for bottom . The larger bearing engines seem to have really nice bottom end ,and the older- smaller bearinged versions are much more violent . So take it for what it's worth and run crazy with it
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Old 12-22-2007, 08:48 PM
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Whats a 421b?

Im guessing its a motor with a longer stroke than engines of the same capacity.
It was a general comment.
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Old 12-23-2007, 06:03 AM
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THe 421B is a Novarossi engine that was out a year or so back , they are 8 port engines ,now it's called an 821.
http://www.novarossiusa.com/product_...products_id=57
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Old 12-23-2007, 04:18 PM
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Thankz for the info
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Old 12-23-2007, 04:38 PM
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My understanding on ports are that the top 3 ports are the ones responsible for the timing charachteristics of the engine in conjunction with exhaust and inlet timing .

The lower ports are traditionally used as relief ports. When on the down stroke the fuel can flow out of the side of the sleeve as opposed to the bottom of the crank case , this can help with top end but is not manditory to achieve it

If you use efra approved 3 port .12 engines as an example they are all 3 port engines yet have different top end and bottom end ... All their differences are created by port timing changes. And .12 engines normally rev out higher than .21 's etc .. I do realise this is because its a smaller engine cc but they have no problem getting up there in terms of RPM ..

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