cmego

What are your thoughts on 7vs9 port motors and where and when would you use them?

Roelof

There are so many topics about differences between engines and the amount of ports is also discussed a lot.

The amount of ports is not making the engine. If a 9-port should be faster then the 7-port Picco and OS (based) engines would never be sold. In an 2-stroke engine the timings and the shape of the exhaust is making the performance. All onroad models have a 3 port exhaust port, to go as wide as possible. But with the intake ports if you can set the timings you can even a 3-port enginge perform the same as a 9-port.

In the case of a Novarossi they have 3, 5, 7 and 9 port onroad engines and in a simple fact the lower the amount of ports the lower the timings and so the lower the performance. Even in the 9-port range Novarossi has several models. Take a standard 35plus21 and a 7 port Tuned Maxima OS based engine, the Maxima is much faster.

Also about charateristics like driveabillity, bottom power etc, is all determed by timings and other internal dimensions, there is no way you can give certain characteristics to the amount of ports.

Pedro Jesus

Roelof
A doubt of mine if I have two engines a 7ports and 9ports.
Will I use the example of Novarossi, Mito 9 is faster than a Mito 7?
Two doors will make so much difference in progress on the track?
The engines having the same intake and exhaust timimgs.

Thank you

Roelof

If both are exacly the same timed and have the same wide exhaust port (the wideness is also a kind of timing) then I would expect an reasonable equal perfomance. You are talking about intake and exhaust timings, also crank timings, and crank bore?
The only other differences with Novarossi could also be made by the used materials. I know Novarossi has many piston materials to choose from and due the small expansion differences and friction factors that can have an effect on the overall performance.

Pedro Jesus

If both are exacly the same timed and have the same wide exhaust port (the wideness is also a kind of timing) then I would expect an reasonable equal perfomance. You are talking about intake and exhaust timings, also crank timings, and crank bore?

Yes Roelof the only difference being even only ports 9 against 7.
The progress of the engine will be very similar or even equal to the little I already understand.
Because of the price difference that still is some of a 9 port for a 7 port.

Thank you

Roelof

Currently Novarossi is selling several 35 plus models for arround 200~250 euro, I have thee 2016 model and a JP 35V2 and all have the same timings. On its way is also a blackhead Flash which is sold for less than 200 euro and I think it has also the same timings but soon I know.
I stretch them all up to what I like and they all run fine.

A fellow driver is using ISON21 models and does give them the same timings and indeed we run equal and even my previous 5 port engines with a multi exhaust port are running as fast with the same timings. Only the piston does not have a long life with those performances.


And still with Novarossi I would expect that out of the box the 7 port must be slower but again it can also be different in the chosen materials like piston alloy, maybe a different crankshaft (2 or 3 weights) and visual tuning like a larger scoop in the crankshaft and teardrops on the sleeve. Small things that can make a small difference in quality and performance.

Pedro Jesus

Thanks Roelof
Now I understand the differences
It is always with pleasure that I read your comments.