Algebra based desktop Dyno

[Chriszz11]

Hi, I'm in the process of writing my own desktop Dyno software just for the sake of challenging myself and to learn as much about the math behind engines. I'm having a bit of a hard time though finding a way to calculate the approximate volumetric efficiency losses in the intake system. I know how to find how much air it would need to make an engine run at 100% VE, but to find roughly how much air it will actually draw in is the challenge. It would need to be effected by valve size, valve lift, cam duration, intake runner length, intake runner csa, plenum volume, tb size, intake tube diameter and length, and likely a few things I'm forgetting. Any help would be great. Thank you!

 

[CWB1]

Pull out the thermodynamics texts, you’re trying to determine mass flow downstream of various restrictions/pressure drops given varying atmospheric and vacuum conditions.

 

[gruntguru]

To be accurate the flow must be considered as compressible and transient. 1D engine modelling software does what you are trying to do.

je suis charlie

 

[RodRico]

Are you trying to write something like the $48 ($6 used) model and manual shown at

http://www.amazon.com/DeskTop-Dynos-Computers-software-Performance/dp/1884089232

from Motion Software (

http://www.motionsoftware.com/Dynomation6.htm)?

I've never used their software, but it looks pretty useful. I'd start with the $6 used manual and software then read the full version's manual to verify quality before committing to large $500 package. I found this some time ago when I was looking for engine simulation software. Unfortunately, this one and every affordable one I've seen assumes use of a crankshaft. Of course if you're just trying to learn, doing it all yourself is best. I had to take that path, and it's been a lot of work just to get what are nothing more than approximations given the fact my engine isn't traditional and therefore has a lot of unknowns that blow common assumptions apart.