Engine braking calculation
Engine braking calculation
(OP)
Has anybody got a handle on the typical torque you'd get from engine braking? In particular I am very interested in the effect of throttle opening, ignition off.
Cheers
Greg Locock
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RE: Engine braking calculation
RE: Engine braking calculation
What ivymike alluded to with the diesels & the exhaust/compression braking effect - ie, open the exhaust valve at TDC after the compression stroke - would add significantly more torque, since all the compression work is lost. But, this requires an external mechanism (ala Jake Brake or similar).
RE: Engine braking calculation
This applies near red line. As the air velocity drops at lower rpms I imagine the differences converge quite rapidly.
Cheers
Greg Locock
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RE: Engine braking calculation
BTW, in my experience it is less than with a closed throttle, but I never tried part throttle conditions which could be greater.
RE: Engine braking calculation
If you lose ignition at speed, it will coast a lot further in gear with the throttle open compared to the throttle closed or engine braking in a lot more on a closed throttle compared to open throttle with no ignition.
Regards
Pat
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RE: Engine braking calculation
RE: Engine braking calculation
J1263 Road Load Measurement and Dynamometer Simulation using Coastdown Techniques.
You would need the neutral coastdown data to get the road load of the vehicle; then, instead of the full throttle acceleration, you could do your closed threttle deceleration measurements. QED.
"Schiefgehen will, was schiefgehen kann" - das Murphygesetz
RE: Engine braking calculation
RE: Engine braking calculation
It is very noticeable with a bench-test engine that the engine's starter motor has to work hard to turn the engine over with the throttle at idle. Adjust the throttle plate so that it is completely closed and the starter motor can turn the engine over much more easily.
RE: Engine braking calculation
RE: Engine braking calculation
"Schiefgehen will, was schiefgehen kann" - das Murphygesetz
RE: Engine braking calculation
RE: Engine braking calculation
I know that small engines' starters seem to labor more with the throttle open, but I took that "laboring" to be the sound of increasing and decreasing speed due to compression/expansion of the charge, and not necessarily indicative of average power consumption.
RE: Engine braking calculation
"Schiefgehen will, was schiefgehen kann" - das Murphygesetz
RE: Engine braking calculation
On a different matter - I assume that you are aware that "Ivymike" was the codename for the first hydrogen bomb test? Or just a coincidence?
RE: Engine braking calculation
I just thought this handle was "the bomb."