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Old 03-28-2010, 08:59 AM   #1
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Default Engine Ports

What exactly do the ports on a nitro engine do? I see 8,5 3 which is best?
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Old 03-28-2010, 09:55 AM   #2
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depends what your looking for. and there is a 7 port also. the higher the port the faster it will be but it will also suck more gas. The high ports also have worse bottom end If your gonna use a truck get a 5 port it will have good top speed and better bottom end and for a buggy get a 7 port!
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Old 03-28-2010, 10:01 AM   #3
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i run an 808 and trying to decide on new engine.
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Old 03-28-2010, 10:03 AM   #4
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just go for a well used/tested engine... keep in mind the V-spec is a 3 port engine that gives tons of torque with great top end and good mileage.... so look around, read and go fro the best performance.. don't worry about port count for now
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Old 03-28-2010, 10:04 AM   #5
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first and foremost, IM NOWHERE NEAR AN EXPERT, but I have been researching the basic functions of 2 cycles lately quite often, doing a lot of reading trying to understand them more for faster trackside evaluations etc when I have problems. I hate bugging the fastguys to help me get my tune dialed so Im really working hard at learning...........Monty is always a big help too when I'm lost

Here's kinda what I have gathered.......Ports are the intake or exhaust ports. The porting lets the air, fuel, and exhaust flow through the engine, as the piston hits BDC......the sleeve's intake ports are uncovered. The piston's movement has pressurized the fuel/air mixture in the crankcase, so it adds to the crankcase volume and displaces the remaining exhaust gases out of the rear exhaust transfer port and into the header/tuned pipe. That's basically how porting works. Generally, the low port engines have more lowend, the more ports the more topend. There are many variables to take into consideration as far as choosing what engine, but IMO nothing is really any better than any other, it solely depends on your application.
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Old 03-28-2010, 11:22 AM   #6
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The rules for building an 2-stroke engine and making the performance is more about timingen than ports. Manufacturers give more powerfull engines more ports so we believe we need more ports to go fast. If they only sell 3 port engines configured from slow to fast you would understand better that it is possible to make a 3-port engine fast. A nice example are the .12ci 1/10 GP car engines which are limited to 3 ports by rules and do go fast.

One yes, more ports can create a better flow of the mixture and can help to get more power, more top RPM and a better fuel consumption out of an engine. But if you do setup 2 same timed engines from the same parts/materials, one with 3 ports and the other with 7 you will not know the difference and maybe you can feel a slight difference.
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Old 03-28-2010, 11:47 AM   #7
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A few more things to add.... More ports means better support of the piston, as there is more bridging in the sleeve....which also allows a broader coverage of the available intake area of the sleeve....As well with that, higher port timing can be achieved while still retaining full coverage of the sleeve without allowing overall port volume to get too high .....on a 3 port having high timing and full coverage would result in a very high overall port volume, which would result in an engine that is very hard on fuel, not to mention the risk of not having enough piston support....... multiple smaller ports also allows the designer to control the intake charge direction, timing and volume more accurately, which if done correctly can aid the loop scavenging of the engine..... In overall peak power the more port volume the better, however when powerband characteristics and fuel mileage are a concern using a higher number of smaller ports allows more control of the engines characteristics as opposed to a 3 port.....If done correctly a 7 port could be made into a torque monster, just like a 3 port can be made into a top end screamer, Its all in the designers goals for the engine.....
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Old 03-29-2010, 03:02 AM   #8
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True, a 3 port engine with a rear exhaust has the side ports directly in the line of the turningpoint of the piston.



Thats why normally 5 (or more) ports are better because there is a bridge exactly on that spot. Thats also why side exhaust engines just have a small exhaust port.

One of the perfoming winning things is making the exhaust wider. Looking at the .12 racing engines they have to do it with one exhaust but with "unlimited" .21 engines we do have 2 extra side exhaust ports making the total exhaust wider for more performance.
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