Hi Matt...Will I benefit by opening the boost port to the same size/ shape of the base gasket appature? Also would I gain anything by radiusing the outer edge of the exhaust port to match the circular shape of the gasket/manifold?
Thanks in advance. _________________ Hmmmmm!
It's a bit more involved than just opening out the boost port though, you need to get the shape of the whole length of the port correct to get the most effective gain.
Take the exhaust port out to the shape of the gasket and you will bugger the barrel completely.
I would say that if you really want to have a go at the barrels yourself, then for the time being, stick to "optimising" them, i.e. square (even) all the ports up so there are no uneven edges, as per the guidelines in the tuning section.
I think I can pretty confidently say that neither Matt or anyone else is going to tell you how to get a lot of power out of the porting as it's cost him hundreds of hours and probably thousands of pounds in development time finding out for himself! It really is a "try it and see what happens" affair, although I couldn't stand by and blatently watch you scrap a set of barrels by screwing up the exhaust port exits! _________________ Andy.
NSR-WORLD.COM
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I will also say about the exhaust port that under no circumstances open out the port to match the pipe.
What happens is that you lose all exhaust gas velocity and everything will go out of synch.
There's optimum dimensions for the port and you have to think that Honda didn't get it wrong. They wanted power at Xrpm and they got it.
Take a look at an RS barrel (preferably NF4 or NF5) and check that out. You'll see that it's still an oval shape (albeit different dimensions to NSR) not round and not matched to the pipe.
Opening out the boost port to match the gasket does work, but because you're removing material it also lowers the primary comp. It helps slightly by making flow easier, but it doesn't increase flow as much as you'd think because it's still trying to squeeze through the same size aperture into the cylinder. The lower primary comp reduces pumping loss at high rpm so can potentially make more power.
If you're going into the tuning game then read lots of books on the subject and make sure you have all the tools for the job. Just cutting what you can see is a sure fire way to lose power. Also be prepared to scrap a few cylinders and heads in the process!
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