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Volumetric Efficiency
- Thread starter CZero
- Start date
GregLocock
Automotive
(volumetric flow rate/(capacity/2*rpm/60))*100%
Is that what you meant?
Cheers
Greg Locock
Is that what you meant?
Cheers
Greg Locock
- Thread starter
- #3
CZero, On dynos we find a reliable way to measure fuel flow being used by the engine, using fuel balances or perhaps coriolis fuel weighing measurement equipment.
Next you need an accurate method of measuring AFR.
It's a relatively easy task to work out what your VE is once you have determined the airflow into the engine ( AFR X Fuel flow)- I won't go into it here as I don't think that is what you were asking.
I wouldn't trust the Oxygen sensors - used in emissions exahust equipment for consistent enough AFR reading to give good VE. The reason being - that when the mixture is very rich- there isn't much oxygen in the exhaust anyway- thus leading to its inaccuracy.It is far better to use emissions analyser kit getting a reading of H and C in the exhaust and using the spindt method to determine the AFR.
A standard MAF sensor has alot of signal drift and usually can't decipher between forward and reverse flow ( can lead to signal aliusing errors)- but usually gives a good inidication of the SHAPE of VE curve.
If you need to find out the VE of a particular road car, you could try using a MAF sensor and calibrating it to a steady state flow rate using a flow bench and then using it to determine the airflow into the engine. Try and mount it at a place on the engine where there isn't alot of pulsing flow/tuning-such as next to or within a large volume. Injector pulse width could also be used, but both of these methods are likely to lead to alot of inaccuracies and errors.
Some manufacturers, such as Porsche advertise/display the WOT BSFC of their cars in their owners manuals, I've often used these figures ( after checking them for consistency) to work back to VE, using reasonable AFRs.
Next you need an accurate method of measuring AFR.
It's a relatively easy task to work out what your VE is once you have determined the airflow into the engine ( AFR X Fuel flow)- I won't go into it here as I don't think that is what you were asking.
I wouldn't trust the Oxygen sensors - used in emissions exahust equipment for consistent enough AFR reading to give good VE. The reason being - that when the mixture is very rich- there isn't much oxygen in the exhaust anyway- thus leading to its inaccuracy.It is far better to use emissions analyser kit getting a reading of H and C in the exhaust and using the spindt method to determine the AFR.
A standard MAF sensor has alot of signal drift and usually can't decipher between forward and reverse flow ( can lead to signal aliusing errors)- but usually gives a good inidication of the SHAPE of VE curve.
If you need to find out the VE of a particular road car, you could try using a MAF sensor and calibrating it to a steady state flow rate using a flow bench and then using it to determine the airflow into the engine. Try and mount it at a place on the engine where there isn't alot of pulsing flow/tuning-such as next to or within a large volume. Injector pulse width could also be used, but both of these methods are likely to lead to alot of inaccuracies and errors.
Some manufacturers, such as Porsche advertise/display the WOT BSFC of their cars in their owners manuals, I've often used these figures ( after checking them for consistency) to work back to VE, using reasonable AFRs.
- Thread starter
- #5
I need to understand it somemore.
Alright let me talk about my own application.
Its hondas new 2.4liter engine (K24a1) From a honda SUV to my 1994 honda civic (With special mount kit). The engine is being completely rebuilt (87mm bore x 99mm stroke) <-Stock.
This engine comes with a Map sensor. (Like most honda engines do.)
An Aftermarket ECU will be used as well as a UEGO sytem. I decided that I am going to turbocharge the 2.4liter, so I called Innovative Turbos, a very very good turbo comp.
As I'm filling out the application for selecting the proper turbocharger I come across : engines volumetric efficiency?
Ok guys I am very new to this V.E. please fully elaborate and ask many any thing about my setup....
Thanks
Alright let me talk about my own application.
Its hondas new 2.4liter engine (K24a1) From a honda SUV to my 1994 honda civic (With special mount kit). The engine is being completely rebuilt (87mm bore x 99mm stroke) <-Stock.
This engine comes with a Map sensor. (Like most honda engines do.)
An Aftermarket ECU will be used as well as a UEGO sytem. I decided that I am going to turbocharge the 2.4liter, so I called Innovative Turbos, a very very good turbo comp.
As I'm filling out the application for selecting the proper turbocharger I come across : engines volumetric efficiency?
Ok guys I am very new to this V.E. please fully elaborate and ask many any thing about my setup....
Thanks
Turbinator
Mechanical
Someone can correct me if I'm wrong, but I believe most non-racing DOHC engines have VE in the 100% range at peak torque, and around 90% at peak HP. If this is just for turbocharger selection, just say 90-100% and you should be fine. I don't think they will suggest a turbo that puts you within 10% of its max flow rate anyway.
- Thread starter
- #7
patprimmer
New member
My understanding of VE is quite simple, it is the ratio of the mass of air drawn into the cylinder on one induction stroke vs the mass of air equal to the volume of the displacement of the cylinder with the air at ambient density.
This might not be the "Official Definition", but it is what is meant by volumetric efficiency when you consider that supercharging dramatically increases VE.
Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
This might not be the "Official Definition", but it is what is meant by volumetric efficiency when you consider that supercharging dramatically increases VE.
Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
GregLocock
Automotive
Even in naturally aspirated engines VE can exceed 100%. F1 engines manage about 110%
This guy goes through the calculations in laborious detail (I haven't checked it)
Here's a study showing VEs of up to 100%
Cheers
Greg Locock
This guy goes through the calculations in laborious detail (I haven't checked it)
Here's a study showing VEs of up to 100%
Cheers
Greg Locock
You will have 100% volumetric efficiency if you, have the engine stopped and the intake valve is open, or if it has set long enough for the air to equalize.
And when it is running engineers try to accomplish that same total volume filling using intake and exhaust tuning and cam timing. Also like others have mentioned using a pump of some sort to help pack more air into the cylinder.
And when it is running engineers try to accomplish that same total volume filling using intake and exhaust tuning and cam timing. Also like others have mentioned using a pump of some sort to help pack more air into the cylinder.
SammyDaFish
Mechanical
Czero, if you are so in the dark as to what Volumetric Efficiency is, I suggest you do a little research before trying to tackle any kind of turbo setup on your engine. I'd like to suggest a few books:
Advanced Engine Technology - Heinz Heisler
Forced Induction Performance - A. Graham Bell
Maximum Boost - Corky Bell
The Corky Bell book is a very simple one and a good introduction to the concepts of how and engine works, specifically in a forced induction scenario. Don't take any of the formulas in the book to the bank though, they are often oversimplified to the point of being inaccurate. They often switch back and forth between measurements of volume (which as pat mentioned, is quite meaningless) and mass, They fail to differentiate he two, and convert one to the other without even making mention of STP. This is true in the Graham Bell book too, but to a much lesser extent.
Happy reading
Advanced Engine Technology - Heinz Heisler
Forced Induction Performance - A. Graham Bell
Maximum Boost - Corky Bell
The Corky Bell book is a very simple one and a good introduction to the concepts of how and engine works, specifically in a forced induction scenario. Don't take any of the formulas in the book to the bank though, they are often oversimplified to the point of being inaccurate. They often switch back and forth between measurements of volume (which as pat mentioned, is quite meaningless) and mass, They fail to differentiate he two, and convert one to the other without even making mention of STP. This is true in the Graham Bell book too, but to a much lesser extent.
Happy reading
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