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Old 12-23-2007, 04:30 PM   #16
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First my disclaimer, I am by no means an engine guru, modder, or experienced in engine construction.

What I have felt and seen in the past on dynos leads me to think that the ports more effect powerband then top end and bottom end. I agree with what massive said and timing affects performance more than porting. From my own experience I can tell that the feel of 3 port engines seem to spool up very fast and not have a great feel when your half way into the trigger. Where as higher port engines have a more linear feel and seem to be more responsive half way into the trigger.

I think that it is been proven that there is no perfect port / timing combo. RB is a very proven brand and there top of the line engines are in the higher port count. O.S. is at the other end of the spectrum with a 3port design.

I think in the future we may see growth in the 3port market by many mfgr's as a way to keep costs down and stay competitive in the market.
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Old 12-23-2007, 05:00 PM   #17
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There is alot of factors that determine how an engine will perform... traditionally a 3 port engine is better for bottom end and a 8 port is better for top end....... But crankcase volume/ engine stroke and rod length also play a big role in an engines output........... The V-Spec is a 3 port engine, which helps with bottom end, but also the V-Spec is a short stroke engine with a very long connecting rod, which allows it to operate at higher RPM's easier.... Which is why a V-Spec comes on early and is able to carry the power deeper into the RPM range...... OS was very clever designing the V-Spec, they used the low end characteristics of a 3 port combined with a very short stroke and long rod, almost a odd combination by standard theory, using a torque sleeve with high RPM engine geometry...in the end they created a world class engine.

The more ports an engine has, the more control the engine designer has over the intake charge..Which allows them to strengthen the engines Shrnerle effect over a broader RPM range . As well higher number of ports allows more overall port volume without the risk of the piston catching a port...
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Old 12-23-2007, 09:39 PM   #18
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I wouldn't say a V-spec rod is very long, I think it's only .015 inch longer than a Novarossi. It is the same length as the Trinity Drake I have (Picco)

Rex
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Old 12-23-2007, 10:48 PM   #19
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Quote:
Originally Posted by 22Racer View Post
I wouldn't say a V-spec rod is very long, I think it's only .015 inch longer than a Novarossi. It is the same length as the Trinity Drake I have (Picco)

Rex
rod stroke ratio( I should have been more clear).... the V-Spec has a 16.0 mm stroke..the Jammin has a 16.8 mm stroke..........
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Old 12-23-2007, 11:03 PM   #20
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the v specs also have a bigger bore and a short stroke . they were designed similar to the older top sbk line of engines from novarossi more cubic displacement = more air fuel mixture=great power . if i wasnt such a novarossi believer os would be my next engine of choice

and agreeing with maximo in porting beliefs more ports doesnt necessarily mean more top less low , just means you can create a more controllable and useable powerband effect to an engine , im not so stoked on the 367 design yet though . they run good but very odd to have 2 vertical transfer ports actually under the b type exhaust ports and a huge picco like compression relief port
later , monty
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Last edited by houston; 12-24-2007 at 10:05 AM.
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Old 12-24-2007, 05:50 AM   #21
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Massive, Maximo, and everyone else... I gotta hand it to you guys, this is the kind of discussion that i was hoping to achieve... I have my own thoughts on the subject but it's interesting to see what others think!
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