volumetric efficiencies (VE)

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swedefish

swedefish

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Got this question:
Is there any way to estimate/calculate the volumetric efficiencies (VE) in the engine?
The engine is a 383+.040, MP cam 284/484, 915 heads with upgraded valves
(don´t got the numbers on them ), RPM intake.
Many thanks in advance.
Lenny
 
Not without knowing the horsepower output. The VE is basically a percentage. Say your engine is 500 cubes. To make the math easy, let's say its only puttin out 250 HP. That means VE is 50%. I know there are much more complex formulas you can figure with, but that's basically all you're talkin about here.
 
You need to know exactly how much air is going in, how much fuel is going in, and how much power is coming out. Meaning a trip to the engine dyno (chassis won't measure these accurately enough).
 
Thanks guys.
Had a look at the link scuba gave me, according to the link it can be calculated if you got the mass air flow rate. But this is kind of hard to accomplish without the modern electronics in the engine (Mass air meter and the intake temperature).
So, I guess that the only option is to estimate the VE.
Low performance engine 75-80%
High performance 80-85%
Allout race engines 90-100% or even more..
:read2: :dontknow:
 
Most street performance engines will come very close to 100% at peak torque. I know of race engines that getr closer to 115% but these are not low rpm engines.
 
moper said:
Most street performance engines will come very close to 100% at peak torque. I know of race engines that getr closer to 115% but these are not low rpm engines.
Click to expand...
Thanks moper
How does a "oldschool" cam grind affect the VE compared to a new more modern grind of an camshaft, with a faster ramp and wider LSA.
My guess would be that a modern grind would give a more effective VE?
 
IMO, it has little to do with it on it's own. VE is the actual empirical result of everything. Machine work quality, assembly, ring seal, chamber/piston interaction, valve job, ignition, port (meaning from the back of the intake valve to the carb or throttle body butterfly), exh system, carb design and calibration... The cam does affect all that but what it does is more about what rpm the VE peaks, and how long the peak is maintained rather than adding a ton to it. As all the parts and labor get better, the fast rate cams lose ground against just larger lobes that dont let the valve bounce. The fast rate stuff becomes almost moot when the lift is larger and the rpm potential is raised because regardless of what the lifter diameter is, you have to lift a valve fast to get it .700" and hold it open for 280° at .050.
 
moper said:
IMO, it has little to do with it on it's own. VE is the actual empirical result of everything. Machine work quality, assembly, ring seal, chamber/piston interaction, valve job, ignition, port (meaning from the back of the intake valve to the carb or throttle body butterfly), exh system, carb design and calibration... The cam does affect all that but what it does is more about what rpm the VE peaks, and how long the peak is maintained rather than adding a ton to it. As all the parts and labor get better, the fast rate cams lose ground against just larger lobes that dont let the valve bounce. The fast rate stuff becomes almost moot when the lift is larger and the rpm potential is raised because regardless of what the lifter diameter is, you have to lift a valve fast to get it .700" and hold it open for 280° at .050.
Click to expand...


Thanks moper :thumbup:
 
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