Wierd ideas on porting and making power in 4strokes...

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m_mcgranahan · #1 Post by **m_mcgranahan** » Sun Aug 03, 2008 8:36 pm

Hi,

I am on vacation and just taking some time do surf the web and I found a site dealing with high velocity porting on Superbike heads. This guy decreases the port size 30% to get more hp!

I have a feeling that: this doesn't apply to our quads because the power gain seems comes in well above 11,000rpm, we have adjustable cam timing, so we can tweak the overlap time etc that play into all this, our quads ar EFI and some of this has to do with a carborated 4 stroke.

All that said, it is interesting. Thought I would post links and see what you all think of them.

God bless...

Mark

http://mototuneusa.com/the_8_phase_motor.htm

http://mototuneusa.com/think_fast_intake_porting.htm

http://mototuneusa.com/homework.htm

http://mototuneusa.com/the_2007_superbike.htm

http://mototuneusa.com/super_sonic_nozzle.htm

http://mototuneusa.com/success_stories.htm

T-Rex · #2 Post by **T-Rex** » Sun Aug 03, 2008 9:22 pm

High Velocity porting works well with engines that stay at a certain rpm range for long periods at a time. Mainly 7500 to 8500rpm and thats big motors. Torgue moves mass no question about that.
Now I run a YFZ 470 and using a HSR 45mm Carb and it LOVES it but I shift around 11500rpm. I have two other buddies using 48mm HSR carbs and having great results.
The amount of CC's and rpm shift point should be the factor of what size carb needing to be used....

desertbound · #3 Post by **desertbound** » Sun Aug 03, 2008 9:30 pm

My yfz head was epoxy ported. It was hogged way out and then reshaped with epoxy. The throttle response was amazing. I have a feeling these heads need to be more opened up though. I originally had a head that was mx ported and to tell you the truth, I liked it better. That was because like T-Rex said, I wasn't drag racing and constantly at high rpm. The epoxy porting was for top end/drag applications. Don't get me wrong. It was still a huge improvement, but the I like the nice clean up mx port jobs the best. Escecially since most of the factories do such a good job to begin with now.

m_mcgranahan · #4 Post by **m_mcgranahan** » Sun Aug 03, 2008 10:25 pm

Hi,

Yeah, interesting but it did seem to be more for superbike racing than mx for us, but it was a good thought provoker. After seeing Wistech's results with porting and taking out "2 lbs" of Aluminium from the little engine that could 432 project and getting over 56hp, I doubted this would apply to us, never hurts to read another perspective.

God bless...

Mark

m_mcgranahan · #5 Post by **m_mcgranahan** » Sun Aug 03, 2008 10:43 pm

HI

In looking at and thinking about the dale head, I think there may basic shaping issues with the design. That led me to wonder if people could post pics of other brand machine pre and post porting. (if you can list make, model, pre and post dyno results if you have them) I would especially love to see how the LTR 450 and 450R handle intake and exhaust but it would be good to see everyones motors.
Just a good idea to see how other manufacturers do things.

God bless...

Mark

haydug · #6 Post by **haydug** » Sun Aug 03, 2008 11:19 pm

I went with smaller intake valves in 2002, and with the port work, it ran awesome. That was before strokers and big bores, and that bike pulled almost every holeshot at the nationals that year in 250B and 25+ class against some very nice 250R's.

cannondale27 · #7 Post by **cannondale27** » Sun Aug 03, 2008 11:58 pm

Porting for velocity may work for exhaust but in this day of fuel injection things need to be rethunk on the intake side.Is a reason why Yamaha ditched the 5valve head on all thier performance 4strokes.Singles will be 4v next when they go with fuel injection.Atomization is not a issue anymore.You need velocity to pull fuel out of a carb decently.We dont.

m_mcgranahan · #8 Post by **m_mcgranahan** » Mon Aug 04, 2008 12:41 am

Hi,

Yeah, on the carb vs EFI, pretty much what I thought, but still interesting to talk about. I don't know about the high velocity on the exhaust, I thought the idea was to open up the exhaust for better flow and the reason for the high velocity is fuel air mix and the exhaust doesn't need that. Is there anyther reason to think about high velocity on the exhaust Steve?

God bless...

Mark

cannondale27 · #9 Post by **cannondale27** » Mon Aug 04, 2008 12:47 am

Sure seems to be.Look up D-Porting.But it might just be the small headpipe we have.Lots to learn on exhaust end yet for sure.Really potential on both ends.Sure isnt smaller that works though.

m_mcgranahan · #10 Post by **m_mcgranahan** » Mon Aug 04, 2008 1:03 am

QUOTE (cannondale27 @ Aug 4 2008, 12:47 AM) <{POST_SNAPBACK}>

Sure seems to be.Look up D-Porting.But it might just be the small headpipe we have.Lots to learn on exhaust end yet for sure.Really potential on both ends.Sure isnt smaller that works though.

Hey Steve,

Any word on the hugh throttle body project??? Really love to see some reports on that one!

How small is our head pipe compared to the jap 450's? I always thought we got away with it being smaller due to how short ours in due to being on the back of the motor and not having to sweep all the way around from the front to the rear. That being said, I bet on the high HP motors, I bet a bigger header could help.

God bless...

Mark