Turbo/supercharged Volumetric Efficiency
Turbo/supercharged Volumetric Efficiency
(OP)
What is the highest VE anyone has ever recorded/analyzed on a forced induction engine?
javier
Custom Turbo Applications
http://www.full-race.com





RE: Turbo/supercharged Volumetric Efficiency
P.S. Privat message to autor, I am making that spredsheet what I promist you for input data for my program... in the moment I am taking vacation 7 days in alps skying after that I will send you... wont be at ofice next days.
RE: Turbo/supercharged Volumetric Efficiency
the eq's i have found are:
VE=2*(mass flow rate_AIR+mass flow rate_FUEL)/(intake density*displacement volume*engine speed)
or
VE=1-(exhaust pressure/intake pressure-1)/(ideal gas specific heat ratio*(compression ratio -1))
i believe these eq's are for NA engines.....what about FI?
javier
Custom Turbo Applications
http://www.full-race.com
RE: Turbo/supercharged Volumetric Efficiency
RE: Turbo/supercharged Volumetric Efficiency
Theoretical mass flow is working volume multiplyed with averaged density in intake manifold (or infront of intake valve)
That is how formula for VE should be derived
RE: Turbo/supercharged Volumetric Efficiency
javier
Custom Turbo Applications
http://www.full-race.com
RE: Turbo/supercharged Volumetric Efficiency
well, I made literal translation from my (Serbian/Bosnian) languarge
RE: Turbo/supercharged Volumetric Efficiency
well this is I think corect equetion acording to Watson and Jonata... not sure about +mass flow rate_FUEL
RE: Turbo/supercharged Volumetric Efficiency
Rod
RE: Turbo/supercharged Volumetric Efficiency
javier
Custom Turbo Applications
http://www.full-race.com
RE: Turbo/supercharged Volumetric Efficiency
You can expect a modestly boosted supercharged V8 that has refinement as one of its priorities to reach over 130 %VE (with respect to ambient).
I've seen figures that show the NEW supercharged Mini cooper reaches close to 150% VE!
A turbo charged engine, with good charge cooling ,may be higher, with close to 180% possible, in extremely well optimised (for performance) cases. The reason a turbo charged often gets higher horse power per litre over a supercharged engine is the lack of the incredible parasitic loss you get with a supercharger such as a rootes blower.
RE: Turbo/supercharged Volumetric Efficiency
Marquis, i think you are getting a bit carried away - you don't refer VE at boost back to ambient it is then meaningless
On a turbo engine the exhaust back pressure will be at least 1.5 times the intake boost. the remaining gases at the end of the exhaust stroke will thus be at pressure, preventing the induction of air until the piston has travelled down somewhat- further more, tuned length exhausts make bugger all difference on a turbo car.
Playing with pressure waves on a boosted car also has only a mild effect when you are already shoving boost down its neck - whats the gain from reflected waves? probably about 0.5 psi compared to the 7-10 psi of boost pressure?
A supercharged car doesn't suffer the above of course
I think you should think about the VE formula a bit bore before claiming 150% VE!!!
RE: Turbo/supercharged Volumetric Efficiency
RE: Turbo/supercharged Volumetric Efficiency
This post illicited a few laughes here- no offense.
I'm not quite sure what engines are being refered to here, perhaps 1950's engines? Side valves?
Unconfirmed- I should definately say.
No disrespect intended, But I have an array of engines I've helped develop out in the field, not to mension competitor engines and seen the figures I quoted on dyno test bed- Nope- not some ageing old chasis dynojet but an actual calibrated Schenk dynos to EEC 1585 and DIN 700020. So all the figures I quoted were either seen by me or read in SAE papers, or tested at out Resserch labs in Dearborn- You see I don't guess, I don't quote unconfirmed data- I post as I see and have seen from my experience- else I say nothing.
"Marquis, i think you are getting a bit carried away - you don't refer VE at boost back to ambient it is then meaningless"
I don't think I'm getting carried away at all. It concerns me little what conventions you choose to use, my friend, however, any OEM and/or manufacturer of boosted engines quote with reference to the ambient conditions post intake zip tube. I'm not quite sure what reference you're using, but if you're refering to using pressure in the plenum as a datum- that would only indicate the efficiency of the manifolding/ports post the actual compressor- THIS is totally meaningless and useless to a manufacturer. If this is indeed what you're refering to, it COULD explain partially why you're figures are so low but they're still far too low.
"On a turbo engine the exhaust back pressure will be at least 1.5 times the intake boost. the remaining gases at the end of the exhaust stroke will thus be at pressure, preventing the induction of air until the piston has travelled down somewhat- further more, tuned length exhausts make bugger all difference on a turbo car"
I think that is a generalisation at best. I've seen enough data - for example look at Heinz Heisler Advanced Engine Technology book, -figures 6.47 page 324 - it clearly shows boost pressure being higher the MEAN exaust backpressure. There will be exhaust pressure pulses that exceed mean boost pressure just as there are scavenging pressure troughs that are far lower.
The reason Turbo charged petrol engines don't have tuned lengths is because quite often the over ridding concern is getting the Turbo lag down and- these days emissions (catalyst light off).
There are big Detroit Diesel or Navi Star engines with tuned lengths on the exhaust side- not to mension steady state engines, where lag is less of an issue ( no throttle),
Somehow I wouldn't dismiss all of Detroit Diesel or Navi Stars work, based on your "bugger all difference comment".
Oh, and if it's formulas you really want:
I use
9.566 (a constant) x Air flow in Kg/hr x ((273.1 + ambient intake temp-celcius)/(Engine capacity in litres x Engine speed x (Barometric pressure /1000))
Perhaps it's forced induction lawn mowers you're refering to - in which case I may be wrong regarding my comments on the level of VE You assert- however, in the future please don't be so blatantly dismissive about what I have seen because it's beyond the realm of your experience. Thank you
RE: Turbo/supercharged Volumetric Efficiency
RE: Turbo/supercharged Volumetric Efficiency
On a mechanical supercharged engine the benifits of exhaust tuning becomes iffy because of the high inlet pressure and at overlap the 'tuning' effect of a neg pulse becomes somewhat redundant (to a point). On a turbosupercharged engine the 'tuning' effect pretty much stops at the turbine.
I won't argue with folks that claim benifit from 'tuning' exhaust systems on a turbo because that's their right. Believe what you will. I know what works for me. BTDT!
Racing was/is expensive and I chose to spend mine on better cumbustion effeciency or a couple inches more boost. I race a vintage mini now and it takes all I can do just to keep it together.
Rod
RE: Turbo/supercharged Volumetric Efficiency
Now i'm not saying this is neccesarily the case with Turbo charged engines, I don't know, I know Porsche Turbos run with some overlap I believe.
RE: Turbo/supercharged Volumetric Efficiency
You seem a little offended at my quest to keep things sane - I am sorry for your offence. You are correct the 80% VE I was referring to was from plenum - thus at pressure, and neglecting throttle plates. So yes, one could subtract another 1% off or so for these effects. My point was that you don't compare 180%VE when talking turbo cars to the 120% or so NA engines can make and make an assumption about technology when the NA technology is very advanced "oh yes of course 180% is possible" - this is akin to bending statistics to suit your purpose - quite clearly the original qestion was referring to the dynamics of the head and combustion process, which is not an air compressor question.
- I thought we had established in the previous responses that we all know NA engines can achieve+100% VE and I chose not to explore that further so was your point a cheap jibe???
i wouldn't assume that as detroit diesel once made tuned length exhaust runners that it actually helped - but I am not beating my chest saying that it doesn't either - just be realistic about the gains
RE: Turbo/supercharged Volumetric Efficiency
Put another way: Sure, referenced to atmosphere you may be tickled pink to see VE's of 130%, but when you reference to the plenum and get numbers of 65%, this could be a huge hint that the cam you were using before you added the turbo is completely wrong with it!!
NOTE: All these numbers are completely "ballpark", I didn't do the above "test" myself, but I could see where it would have benefit.
RE: Turbo/supercharged Volumetric Efficiency
Quick one here
"Put another way: Sure, referenced to atmosphere you may be tickled pink to see VE's of 130%, but when you reference to the plenum and get numbers of 65%, this could be a huge hint that the cam you were using before you added the turbo is completely wrong with it!!"
When developing boosted, OEMs don't use VE figures relative to ambient to be "tickled pink" or as some kind of ego trip relative to NA engine.
The reason for it's use is quite simple to anyone who develops engines for a living and it comes into it's own when doing zip tube/air box development work. If using figures relative to the plenum you will not be able to quantify any of the effects on performace arising from changes in losses upstream of the plenum such as in the intake spout, air box, zip tube etc etc. No development work will be able to be done on sizing the throttle.
Measuring VE relative to plenum would only allow you to evaluate changes to ports, cams, perhaps instake runners. Only a fraction of the picture to someone who needs to get more performance from a boosted engine