Single cylinder intake manifold design

[Shris86]

Hi, I'm currently involved in designing intake manifold for single cylinder engine, but the problem right now I'm facing is I'm not getting any good books or any sites which deals with single cylinder .every books or papers I've referred deals with multi cylinder engines .please suggest some good sites...

[NickFavazzo]

Just out of curiosity, how does the fundamental engine theory change based on the number of cylinders?

[Shris86]

The theory will remain same but in multi cylinder engine we use plenum and runners attached to it and also we calculate the exact length of each runner. In single cylinder there is no point of designing plenum and we have to use single runner ,what about its length ? Is the length may be anything ?

[Warpspeed]

Originally posted by Shris86:In single cylinder there is no point of designing plenum
Perhaps not with an unrestricted engine.

But when you are forced to run an intake restrictor, a large plenum can partially even out the violent pulsing, and draw a higher averaged airflow through the restrictor.

[Shris86]

yeah ,but I'm not using any forced induction so I don't need plenum . But I bothered about the intake manifold length . How you calculate the intake length ? Is there any kind of calculations are there or we can use any length ?

[NickFavazzo]

So what does the plenum, diffuser and runner volume do the gas flow? How will the throttle effect downstream airflow? Why do so many of those teams with singles use that odd volume after the throttle but before the valve...surely they are doing something wrong then what is it? Or maybe they are doing something right...

You can use resonant pipe theory to tune for the runner length but how will the the rest of the intake system be modelled? Open pipe, closed pipe? Thats full throttle sorted, now what about partial throttle?

[Mbirt]

Originally posted by Shris86:
yeah ,but I'm not using any forced induction so I don't need plenum. According to my testing, this is true if you want to make 25hp at 10,000rpm on a 450cc single. The torque curve will be low and flat because each induction event will be choked. Check this out:https://sphotos-b.xx.fbcdn.net/hphotos-snc7/430061_484110534943537_880218388_n.jpg
Each piece of this induction system exists for a reason. Think about the order of throttle-restrictor-diffuser-plenum-runner. Then examine how this team got it wrong:
https://sphotos-a.xx.fbcdn.net/hphotos-snc6/177634_10151278029003658_518758133_o.jpg

[Mbirt]

Sorry about the image size above. Normal BB code for picture resizing apparently does not work here.

[Warpspeed]

Originally posted by Shris86:
yeah ,but I'm not using any forced induction so I don't need plenum .
You need to design your entire induction system around the intake restrictor.
It is there to deliberately reduce power, that is it's function.
The inlet restrictor is going to be the biggest choke point to flow, and the biggest problem you have to overcome, ESPECIALLY with a single cylinder.