Volumetric Efficiency

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mhuppertz

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Anyone have a way to guess volumetric efficiency of a 440 with 10.5:1?

I know the 426 Hemi I used to have would go over 100% VE, but I have no idea (or even a guess) as to the efficiency of an iron headed, mildly ported, big valve wedge heads.

Thoughts, experiences? I guess a dyno sheet would say?
 
Depends on your build.
Better flowing and matched carb to exhaust is gonna have a higher VE % than mismatched restrictive top end. Engine torque is heavily tied into VE %. Best guess around 100%
 
Iron head engine is going to have a tough time doing much better than 80's or maybe low 90's for VE. A good set of modern aluminum heads such as Trick Flow can reach 100% at torque peak but it will take some work and some careful tuning.
 
AndyF said:
Iron head engine is going to have a tough time doing much better than 80's or maybe low 90's for VE. A good set of modern aluminum heads such as Trick Flow can reach 100% at torque peak but it will take some work and some careful tuning.
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I used to play around with an engine analyzer program for my slant 6 and small block mope. I was kinda disappointed with the VE I would get with different typical builds. I don't recall the numbers, but 75% - 80% sounds familiar.
 
You want peak? Average? Area under the curve?

How about this: parked in the driveway, it is ZERO. You'll never get a more accurate answer than that! I win!!!!!!

You want to know at peak hp? Peak torque? Maybe at idle?

Any single value to such a question is worthless. Depends on cam duration, overlap, exhaust length, intake length operating temp and on and on.
 
mhuppertz said:
Anyone have a way to guess volumetric efficiency of a 440 with 10.5:1?

I know the 426 Hemi I used to have would go over 100% VE, but I have no idea (or even a guess) as to the efficiency of an iron headed, mildly ported, big valve wedge heads.

Thoughts, experiences? I guess a dyno sheet would say?
Click to expand...

Any guess would be just that. A guess.
 
No way to tell although I would agree with Andy's guestimates.
 
It is entirely dependent upon the engine build. I'm sitting here looking at some dyno sheets for a 451 stroker using ported 906 heads and sporting a whopping 9.7:1 compression. It is making 690.4 HP and has 88.2% VE @ 3,300 rpm, 100% VE @ 4,500 rpm, oh, and 114.5% VE @ 6,600 rpm.
 
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IQ52 said:
It is entirely dependent upon the engine build. I'm sitting here looking at some dyno sheets for a 451 stroker using ported 906 heads and sporting a whopping 9.7:1 compression. It is making 690.4 HP and has 88.2% VE @ 3,300 rpm, oh, and 114.5% VE @ 6,600 rpm.
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Something you might find interesting with VE. I found an old book at the big swap meet we have here every year. It's named something like "Timing valve events for maximum power" or "Valve events and timing for maximum power" or something. By the Isky brothers. Ed did it's of it if I recall. One of the first lines in the book says something along the lines of:

"You will never be able to achieve over 100% volumetric efficiency with a natural aspirated engine. No engine can pump more air than its cylinders can hold."

Something like that. I read that and had a good chuckle to myself. Book was printed in the early 60's. How much times have changed. Just goes to show you.
 
Lustle said:
Something you might find interesting with VE. I found an old book at the big swap meet we have here every year. It's named something like "Timing valve events for maximum power" or "Valve events and timing for maximum power" or something. By the Isky brothers. Ed did it's of it if I recall. One of the first lines in the book says something along the lines of:

"You will never be able to achieve over 100% volumetric efficiency with a natural aspirated engine. No engine can pump more air than its cylinders can hold."

Something like that. I read that and had a good chuckle to myself. Book was printed in the early 60's. How much times have changed. Just goes to show you.
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I always wondered about that , myself.
 
AndyF said:
Iron head engine is going to have a tough time doing much better than 80's or maybe low 90's for VE. A good set of modern aluminum heads such as Trick Flow can reach 100% at torque peak but it will take some work and some careful tuning.
Click to expand...
After checking other dyno sheets............Yep, sure is what we've seen. 440 with Trick Flow 240 heads, solid flat tappet street cam, Performer RPM intake. 91.7% VE @ 3,000 rpm, 101.3% VE peak, and peak torque @ 3,800 rpm. Then it just carried 98-100% VE to 5,900 rpm. Nice cylinder head.
 
@Lustle

That was probably true when the book was written! LOL The available intakes, heads and the way cams were ground were the inhibitors. That's my guess.
 
I often wondered how accurate the dyno calculated VE numbers were. This is my dyno sheet when my 500 stroker was still wearing its pocket ported 452 iron heads.
 

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VE as presented on the dyno does't mean anything as far as a means for comparison in the real world anyway. Might as well race them just like head flow figures and dyno horsepower...lol
 
moper said:
VE as presented on the dyno does't mean anything as far as a means for comparison in the real world anyway. Might as well race them just like head flow figures and dyno horsepower...lol
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That is certainly true for me. I'm not smart enough to use the information for any real purpose. I check the dyno sheet for the VE and go, "Well, will you look at that?" And that is far as I ever can take it.
 
VE is useful for comparing different engines but only if the engines are all tested on the same dyno or only if the numbers are trusted. It isn't that easy to get accurate airflow numbers so I don't really trust any VE numbers I see published. The air turbines that are used on most dyno engines don't seem to be all that accurate. One way to check is to look at the AF ratio generated by dividing the air flow by the fuel flow. On most dynos that number is significantly different than the AF ratio which the wide band is reading. So that tells you that something else is going on. Either the wide band is wrong, or the air flow meter is wrong, or the fuel flow meter is wrong. They can't all be correct if they don't provide the same number. Figuring out which is wrong can be a difficult task though..........
 
rumblefish360 said:
@Lustle

That was probably true when the book was written! LOL The available intakes, heads and the way cams were ground were the inhibitors. That's my guess.
Click to expand...

I think cam was definitely a big one. Split duration cams weren't really a thing back then (Apparently Ed still doesn't believe in them). And the lobes/ramp rates were wayyyy different than what we run now. Some of the cams that we don't think of twice running on the street would be considered "radical" or "race" cams back then.

The other big one is exhaust scavenging. Tuned port exhaust. And what not. The effect of exhaust on the ability to fill (or overfill) the cylinder is huge. Exhaust does way more work to draw air/fuel into a cylinder than the piston does. This is why Ed mentions the 100 percent VE. Because they hadn't quite figured out then that you could actually achieve a higher VE without some form of boost. That by increasing exhaust flow and using tuned exhaust to increase/pull the intake charge across the combustion chamber and therefore make the engine more efficient. They knew you could cram more air in with a supercharger. But didn't know you could cram more air in simply by tuning the exhaust properly. A lot of what they worked on was the intake side. Of course we now know the huge effect scavenging has. How it clears out all the burnt hydrocarbons. And ensures the cylinder is filled with a good fresh mix of air/fuel. And in the right ratios you can get 100 percent combustion. Which obviously is ideal. They obviously knew scavenging existed. But I don't think they knew it's importance on N/A engines then.
 
A strong VE number basically means the engine has both a well matched and "working" intact tract, and a cam that lets the exhaust blowdown event work to completely empty the cylinder. Intake charge leaving through the exhaust is as bad as exhaust gasses being left in the cylinder. The problem is like Andy said... the measuring systems are potential issues, and there is no correlation to performance of the engine in a chassis. So fun number to look at, good number to "nail", but not worth much aside from validation of other decisions.
 
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