Thread: Exhaust valves
View Single Post
Old 10-21-2015, 06:28 PM   #7 (permalink)
Master EcoModder
Join Date: Nov 2012
Location: San Diego, California
Posts: 944
Thanks: 235
Thanked 344 Times in 240 Posts
On-road data collection.

Originally Posted by aerohead View Post
The thing about the dyno though,is that you can get BSFC data as you go,which is of great importance,and a dyno's the only place to scientifically acquire the data directly that I'm aware of.
It is used daily in industry. Lay people see it as "unscientific and variable". Granted, the lab dyno does allow control of certain variables, however, in the case of exhaust back pressure versus load and fuel use, all one needs is a set of accurately mapped fuel injectors/pump for fuel flow and an in-cylinder pressure sensor to see power potential as well as an exhaust pressure sensor and position sensor on your exhaust backpressure valve.

A baseline run followed by a set exhaust valve run yields a pair of pressure traces that allow you to determine a gain or loss. No need to calculate BSFC as combustion pressure is all the feedback you need. A pair of runs takes 5 minutes or less. A well thought out set of runs can yield a reasonably extrapolated pressure map with which to program an engine map.

Again, there is no need to carry the burden of a dyno cell instrument set. In-cylinder pressure will tell you if the exhaust back pressure is beneficial or detrimental. I would probably add a stepper actuator to the exhaust back pressure valve to make "fanning" the back pressure during runs possible. This reduces the number of runs during your data gathering.

Last edited by RustyLugNut; 10-21-2015 at 06:30 PM.. Reason: Spelling
  Reply With Quote
The Following User Says Thank You to RustyLugNut For This Useful Post:
aerohead (11-28-2015)