How much of a difference does a 5 port make compared to a 3 port? Just curious about it.

Generally, more ports equates to a smoother power delivery with more emphasis on the higher end of the rpm range. That isn't true in every case though. Port timing has as much or even more to do with it than the number of ports. IMO, the quantity of ports has little to do with fuel economy. I can get 12.5 minutes in my buggy with a stock XZ-B which is a 3 port motor. We all know that the Werks B6 will do that too, and it's chocked full of ports. There are many means to an end. Some are more efficient than others. Some are very efficient but just different means.

you'll lose some top end. but alot of times you can go up a tooth or 2 to make up for some of the lost. depending on track sizes you run. if you dont have alot of huge straights then 3 port is all you need. rule of thumb is the lower number of ports more mileage, and more bottom. tracks i race at are medium to small. they are alot of guys running 3 ports. like os v-spec,speed, werks b2, orion crf abi. i run a precirotate pr21c which is a modified 3port and will run will about anything out there, unless like i said there is a huge straight it might run out of nuts

Alright thanks guys. It's been driving me nuts. I was checking out that Precirotate. I may just pick one of those up its a good price.

IMO the biggest advantage a 3-port has over a 5-port is fuel mileage. I know the Orion CRF 3-port makes as much power, maybe more, then the 5-port Discovery I run. Not exactly apples to apples, but pretty close enough.

The 3-port will make more bottom end from design, but they can be "tuned" (have timing changes) to give them a nice top end.

if you have any questions if you get the precirotate let me know i would be glad to help. motors are really awesome. i have the pr21c modified 3port and the pr21bs which is the modified 5port with balanced crank. love both of them

To make a long story short....

Engine timing has more to do with an engines characteristics but port count does play a big role in the engines overall capabilities....In general the higher the port count the better the engine can run higher sleeve timing without losing its bottom end and mileage...There are three very critical factors involved.. Sleeve coverage, overall port volume and overall port timing .The better the sleeve coverage we have the more efficiently the engine will scavenge, the smaller the overall port volume the higher the intake velocity of the mixture will be into the sleeve, the higher the sleeve timing the higher the HP and RPM the engine is capable of.... If we make the 3 port have good sleeve coverage the ports gets quite large..... If we try to give a 3 port higher sleeve timing and good sleeve coverage at the same the engines overall port volume will become too large and the engine will lose its bottom end due to poor intake velocity at the lower RPM's...........As having too much port volume kills the intake velocity of the mixture, which is really apparent on the bottom end, the engine will scream like a banshee on top end, but feel lazy and sluggish on the low end.............. Whereas with a 5 port we can get better sleeve coverage and higher timing without having too much port volume......And a 7 port can run even higher sleeve timing without losing port velocity, We can get excellent sleeve coverage with the 7 ports, and still run very high sleeve timing..... Which means we can make massive RPM and power from a 7 port and not lose any bottom end throttle response.........The only 1 advantage of a 3 port in general design is it can give us good overall port volume at low sleeve timing.....If we time a 7 port low the overall port volume becomes too low and the engine wont make any power as it will be choked off... But with a 3 port design we can run a wide open port, which can give more port volume at very low sleeve timings..... I am not a fan of 3 ports myself in general , i much prefer to work with 5 and 7 port engines as I can just do more with them.....

there is also the point about wearing the piston edge on the wide open sides of a 3 port sleeve...the pistons do rock on that plane and the piston crown will tip into the port to some degree or another.Which is why 3 ports in general will wear out faster then 7 ports will..A 5 and 7 port have have bridging between the ports to support the sides of the piston to prevent this from happening....if we keep the 3 port engines ports small this is not and issue, but smaller ports means less sleeve coverage which means less scavenging which reduces the engines efficiency .... So another reason I like 5 and 7 ports better...3 ports are very limited and only offer an advantage when running very low sleeve timing.! Low sleeve timing generally makes better response and torque at low RPM's but at a big sacrifice to horsepower and RPM...

Sleeve coverage is critical in the scavenging process of the engine, as the incoming mixture flushes out the spent mixture, and the more area of the combustion chamber we flush out the more efficiently the engine will run.... With a 7 port design we can flush out the sleeve from corner to corner, we cannot do that very efficiently with a 3 port unless we keep the sleeve timing very low........In all aspects related to higher performance a the higher the port count the higher the engines overall performance capacity will be, while still being efficient and having good throttle response ....

Looking into a more commercial way there is a simple formula. The more ports the higher the performance.

A 3 port engine from a factory who delivers racing engines up to 9 port will not run as fast as a 3 port engine from a factory who is only making 3 port racing engines.