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Checking Engine Volumetric Efficiency

Old Aug 10, 2025 | 02:26 AM
  #11  
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Les

I did this a while back but I can't find the data.so I will repeat this when I get back in town.

I was looking further at your data and whats interesting is that from 3580-4571 rpm the VE is 87-85 but at the moment of the shift its 79 so your method may be even more valid as well as safer.

George
 
Old Aug 10, 2025 | 09:13 AM
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Originally Posted by GeorgeLG
Les

I did this a while back but I can't find the data.so I will repeat this when I get back in town.

I was looking further at your data and whats interesting is that from 3580-4571 rpm the VE is 87-85 but at the moment of the shift its 79 so your method may be even more valid as well as safer.

George
I suppose that volumetric efficiency can be rpm dependent as well. Just trying to get a set of MAF readings at the same RPM with same vehicles/engines to know what is normal.
 
Old Aug 10, 2025 | 09:20 AM
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Les

Peak VE appears to coincide with peak torque , I assume because thats optimal valve timing and beyond that point efficiency drops towards redline which is why some vehicles feel like they choke out after peak torque.

George
 
Old Aug 10, 2025 | 11:31 AM
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Originally Posted by GeorgeLG
Les

Peak VE appears to coincide with peak torque , I assume because thats optimal valve timing and beyond that point efficiency drops towards redline which is why some vehicles feel like they choke out after peak torque.

George
I'm sure it can be due to a bunch of things, but I believe your statement is true for most.

On the other hand, look at race cars that have greater than 100% volumetric efficiency at redline RPM. I have trouble wrapping my head around all the stuff that contributes to that!

Here is an interesting discussion on relationship between torque peak and volumetric efficiency. https://www.eng-tips.com/threads/vol...output.195304/

Les
 

Last edited by LesMyer; Aug 10, 2025 at 11:46 AM.
Old Aug 10, 2025 | 11:51 AM
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Les

I'm sure that is due to forced air induction and valves that don't float at redline. Do those engines also use variable valve timing?

George
 
Old Aug 10, 2025 | 01:28 PM
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Originally Posted by GeorgeLG
Les

I'm sure that is due to forced air induction and valves that don't float at redline. Do those engines also use variable valve timing?

George
Surprisingly, normally aspirated and fixed valve timing isn't required. I like post #5 here https://stangnet.com/mustang-forums/...engine.715138/
 

Last edited by LesMyer; Aug 10, 2025 at 01:46 PM.
Old Aug 19, 2025 | 01:40 PM
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Here is some more data. Note that it's a cool, rainy day about 75 degrees. Air Density is 92.75% of the Standard Temperature/Pressure (STP) value. It was also right at 92% during the test on August 6 before. So I would expect similar results. And they are.

Also interesting is that Dash Command is not getting the same bandwidth out of my OBD2 adapter as Torque reports that it gives. Takes 0.3 seconds to update 5 pids during logging and they go in sequence so not all timestamps match up exactly and not all RPMS are exact. I think that RPM can go up a lot during 0.3 seconds on a 1-2 shift. Maybe I need to look at all the logging options I have available to me. I think Torque will hook up to my USB OB2 adapter I got for Scan XL Pro, and I know that particular adapter gives fantastic scan rates as it is hardwired. Seems like I must have tried in with Torque before, or how would I know that? Live and learn. I'm getting a bit of good information (for myself anyways) out of this exercise!




 

Last edited by LesMyer; Aug 19, 2025 at 02:04 PM.
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