Volumetric Efficiency
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Volumetric Efficiency
We can all agree that VE is King in power production, at least I think we can all agree to that statement ?. Here is a question to all. With all parts optimal, will a big bore/short stroke engine have a higher 'VE # than a smaller bore/longer stroke engine of the same C.I. ?? Mark H.
Re: Volumetric Efficiency
You can make more power with a lower Ve engine by rpm-ing it more than a higher VE engine.
As for bore vs stroke unless you define an rpm you cant actually answer which will make more VE
As for bore vs stroke unless you define an rpm you cant actually answer which will make more VE
Re: Volumetric Efficiency
All I'm going to say is this!!
"Poked and stroked", as well as being, "gassed", are all fine, BUT I'd rather be, "blown"!!
pdq67
"Poked and stroked", as well as being, "gassed", are all fine, BUT I'd rather be, "blown"!!
pdq67
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Re: Volumetric Efficiency
Volumetric Efficiency is a measure of actual trapped air mass divided by theoretical air mass. It cannot be determined by CFM unless the air density is accurately known.swampbuggy wrote: ↑Thu Sep 06, 2018 7:07 am We can all agree that VE is King in power production, at least I think we can all agree to that statement ?. Here is a question to all. With all parts optimal, will a big bore/short stroke engine have a higher 'VE # than a smaller bore/longer stroke engine of the same C.I. ?? Mark H.
It will determine the torque that can be produced at any given rpm.
Once the air mass has been accurately determined, and the heat energy of the fuel determined, and the combustion efficiency determined, then we can calculated engine torque.
A large bore, short stroke engine should make more torque (for a given displacement) since larger valves can be fitted. In addition, a short stroke engine can be run at higher rpms to produce even more power.
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Re: Volumetric Efficiency
I don't think that a formula can be used to determine actual Volumetric Efficiency - there are just too many variables involved. Basically, VE is defined as how much air, above atmospheric pressure can be crammed into a cylinder. Maximum VE is obtained through efficient design of intake and exhaust tracts as well as camshaft events, and several other factors. 103% to 105% VE is considered very good in a high performance/race engine application however these figures are based on estimates of air movement in a running engine.
Bill
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Re: Volumetric Efficiency
This. That's why when someone displays a dyno sheet, and I immediately say the dyno is happy, it's cut and dried. That's why the internet marketers block those 2 columns now. They finally figured that out. So, now I point that out, which makes it look worse, because they are knowingly hiding it.
Re: Volumetric Efficiency
Is there a simple way to spot incorrect numbers or an equation you use, like for example if someone is claiming more lb/ft per cube than it should be it throws up a red flag?Frankshaft wrote: ↑Thu Sep 06, 2018 12:31 pmThis. That's why when someone displays a dyno sheet, and I immediately say the dyno is happy, it's cut and dried. That's why the internet marketers block those 2 columns now. They finally figured that out. So, now I point that out, which makes it look worse, because they are knowingly hiding it.
Maybe use this dyno sheet as example or if you have one you can show?
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Re: Volumetric Efficiency
Fuel flow in lb per hr / BSCF = Uncorrected HP
Corrected HP / Uncorrected HP = Dyno Correction Factor
If dyno room weather is known, A/F ratio and exact ci then SCFM and VE can also be calculated.
In this example I have SCMF and calculated A/F ratio.
Stan
Bore = 4.60
Stroke = 4.375
Rod Length = 7.0
Cubic Inches = 581.6658
;
Dyno BP = 29.90
Dyno VP = 0.78
Dyno Temp = 97.0
;
; Data for Acceleration / Top speed calculator
; The following parameters must stay in this order
; RPM Torque Fuel BSFC A/F SCFM BSAC
; lb/hr Ratio
Acceleration = 4300 758.6 240.8 .417 0.000 730
Acceleration = 4400 756.4 245.2 .416 0.000 713
Acceleration = 4500 746.2 255.6 .430 0.000 684
Acceleration = 4600 751.0 255.7 .419 0.000 734
Acceleration = 4700 752.8 253.0 .405 0.000 780
Acceleration = 4800 743.6 263.5 .418 0.000 813
Acceleration = 4900 743.8 273.8 .425 0.000 838
Acceleration = 5000 740.4 270.8 .414 0.000 880
Acceleration = 5100 741.2 277.9 .416 0.000 906
Acceleration = 5200 734.7 272.5 .404 0.000 895
Acceleration = 5300 736.0 282.9 .411 0.000 876
Acceleration = 5400 732.6 294.0 .422 0.000 862
Acceleration = 5500 762.5 300.7 .426 0.000 899
Acceleration = 5600 726.4 309.0 .431 0.000 922
Acceleration = 5700 714.2 319.4 .446 0.000 968
Acceleration = 5800 712.0 323.7 .446 0.000 986
Acceleration = 5900 701.9 335.8 .461 0.000 973
Acceleration = 6000 693.4 338.0 .502 0.000 987
Acceleration = 6100 682.9 342.0 .468 0.000 1003
Acceleration = 6200 682.7 342.0 .461 0.000 1019
Acceleration = 6300 671.5 335.8 .453 0.000 1046
Acceleration = 6400 659.7 341.3 .462 0.000 1066
Acceleration = 6500 652.8 339.6 .458 0.000 1061
Acceleration = 6600 644.4 321.4 .433 0.000 1081
Acceleration = 6700 624.4 344.1 .472 0.000 1091
Acceleration = 6800 611.2 344.0 .475 0.000 1092
Corrected HP / Uncorrected HP = Dyno Correction Factor
If dyno room weather is known, A/F ratio and exact ci then SCFM and VE can also be calculated.
In this example I have SCMF and calculated A/F ratio.
Stan
Bore = 4.60
Stroke = 4.375
Rod Length = 7.0
Cubic Inches = 581.6658
;
Dyno BP = 29.90
Dyno VP = 0.78
Dyno Temp = 97.0
;
; Data for Acceleration / Top speed calculator
; The following parameters must stay in this order
; RPM Torque Fuel BSFC A/F SCFM BSAC
; lb/hr Ratio
Acceleration = 4300 758.6 240.8 .417 0.000 730
Acceleration = 4400 756.4 245.2 .416 0.000 713
Acceleration = 4500 746.2 255.6 .430 0.000 684
Acceleration = 4600 751.0 255.7 .419 0.000 734
Acceleration = 4700 752.8 253.0 .405 0.000 780
Acceleration = 4800 743.6 263.5 .418 0.000 813
Acceleration = 4900 743.8 273.8 .425 0.000 838
Acceleration = 5000 740.4 270.8 .414 0.000 880
Acceleration = 5100 741.2 277.9 .416 0.000 906
Acceleration = 5200 734.7 272.5 .404 0.000 895
Acceleration = 5300 736.0 282.9 .411 0.000 876
Acceleration = 5400 732.6 294.0 .422 0.000 862
Acceleration = 5500 762.5 300.7 .426 0.000 899
Acceleration = 5600 726.4 309.0 .431 0.000 922
Acceleration = 5700 714.2 319.4 .446 0.000 968
Acceleration = 5800 712.0 323.7 .446 0.000 986
Acceleration = 5900 701.9 335.8 .461 0.000 973
Acceleration = 6000 693.4 338.0 .502 0.000 987
Acceleration = 6100 682.9 342.0 .468 0.000 1003
Acceleration = 6200 682.7 342.0 .461 0.000 1019
Acceleration = 6300 671.5 335.8 .453 0.000 1046
Acceleration = 6400 659.7 341.3 .462 0.000 1066
Acceleration = 6500 652.8 339.6 .458 0.000 1061
Acceleration = 6600 644.4 321.4 .433 0.000 1081
Acceleration = 6700 624.4 344.1 .472 0.000 1091
Acceleration = 6800 611.2 344.0 .475 0.000 1092
Code: Select all
Engine Size = 581.6658 ci
Dyno Barometric Pressure = 29.9 - Dyno Vapor Pressure = 0.78 - Dyno Air Temperature = 97.0
Fuel UnCorr UnCorr UnCorr Correct A/F
RPM Horse Torque BMEP lb/hr BSFC HP Torque BMEP Factor Ratio SCFM VE%
4300 621.1 758.6 196.7 240.80 .4170 577.5 705.3 182.9 1.0756 13.88 730.0 111.0
4400 633.7 756.4 196.1 245.20 .4160 589.4 703.6 182.4 1.0751 13.32 713.0 106.0
4500 639.4 746.2 193.5 255.60 .4300 594.4 693.8 179.9 1.0756 12.26 684.0 99.4
4600 657.8 751.0 194.7 255.70 .4190 610.3 696.8 180.6 1.0778 13.15 734.0 104.3
4700 673.7 752.8 195.2 253.00 .4050 624.7 698.1 181.0 1.0784 14.12 780.0 108.5
4800 679.6 743.6 192.8 263.50 .4180 630.4 689.7 178.8 1.0781 14.13 813.0 110.8
4900 693.9 743.8 192.8 273.80 .4250 644.2 690.5 179.0 1.0772 14.02 838.0 111.8
5000 704.9 740.4 192.0 270.80 .4140 654.1 687.1 178.1 1.0776 14.88 880.0 115.1
5100 719.7 741.2 192.2 277.90 .4160 668.0 687.9 178.4 1.0774 14.93 906.0 116.2
5200 727.4 734.7 190.5 272.50 .4040 674.5 681.3 176.6 1.0785 15.04 895.0 112.5
5300 742.7 736.0 190.8 282.90 .4110 688.3 682.1 176.8 1.0790 14.18 876.0 108.1
5400 753.2 732.6 189.9 294.00 .4220 696.7 677.6 175.7 1.0812 13.43 862.0 104.4
5500 798.5 762.5 197.7 300.70 .4260 705.9 674.0 174.7 1.1312 13.69 899.0 106.9
5600 774.5 726.4 188.3 309.00 .4310 716.9 672.4 174.3 1.0803 13.67 922.0 107.7
5700 775.1 714.2 185.2 319.40 .4460 716.1 659.9 171.1 1.0824 13.88 968.0 111.0
5800 786.3 712.0 184.6 323.70 .4460 725.8 657.2 170.4 1.0834 13.95 986.0 111.2
5900 788.5 701.9 182.0 335.80 .4610 728.4 648.4 168.1 1.0825 13.27 973.0 107.8
6000 792.2 693.4 179.8 338.00 .5020 673.3 589.4 152.8 1.1765 13.37 987.0 107.6
6100 793.2 682.9 177.0 342.00 .4680 730.8 629.2 163.1 1.0854 13.43 1003.0 107.5
6200 805.9 682.7 177.0 342.00 .4610 741.9 628.4 162.9 1.0864 13.65 1019.0 107.5
6300 805.5 671.5 174.1 335.80 .4530 741.3 618.0 160.2 1.0866 14.27 1046.0 108.6
6400 803.9 659.7 171.0 341.30 .4620 738.7 606.2 157.2 1.0882 14.30 1066.0 108.9
6500 807.9 652.8 169.2 339.60 .4580 741.5 599.1 155.3 1.0896 14.31 1061.0 106.7
6600 809.8 644.4 167.1 321.40 .4330 742.3 590.7 153.1 1.0910 15.40 1081.0 107.1
6700 796.5 624.4 161.9 344.10 .4720 729.0 571.5 148.2 1.0926 14.52 1091.0 106.5
6800 791.3 611.2 158.5 344.00 .4750 724.2 559.3 145.0 1.0927 14.54 1092.0 105.0
AVG:
5550 745.2 710.7 184.2 300.87 .4381 684.9 653.7 169.5 13.98 919.4 108.4
MIN:
4300 621.1 611.2 158.5 240.80 .4040 577.5 559.3 145.0 12.26 684.0 99.4
MAX:
6800 809.8 762.5 197.7 344.10 .5020 742.3 705.3 182.9 15.40 1092.0 116.2
Average based on = 26 points
Stan Weiss/World Wide Enterprises
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http://www.magneticlynx.com/carfor/carfor.htm
David Vizard & Stan Weiss' IOP / Flow / Induction Optimization Software
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Offering Performance Software Since 1987
http://www.magneticlynx.com/carfor/carfor.htm
David Vizard & Stan Weiss' IOP / Flow / Induction Optimization Software
http://www.magneticlynx.com/DV
Re: Volumetric Efficiency
Without defining rpm that may or may not true. The bigger bore will be able to make more power but it may not make more peak VEDavid Redszus wrote: ↑Thu Sep 06, 2018 11:58 am
A large bore, short stroke engine should make more torque (for a given displacement) since larger valves can be fitted. In addition, a short stroke engine can be run at higher rpms to produce even more power.
Re: Volumetric Efficiency
VE is a misnomer DE (density efficiency) is what the engine is seeing .
I think...please correct and or comment on this thought.
I think...please correct and or comment on this thought.
A good test is worth a thousand opinions.
Smokey
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Re: Volumetric Efficiency
I would say that dyno is correct. Not happy. Uncorrected is 389 hp. With a realistic correction factor, it's right in the ballparkGARY C wrote: ↑Thu Sep 06, 2018 1:45 pmIs there a simple way to spot incorrect numbers or an equation you use, like for example if someone is claiming more lb/ft per cube than it should be it throws up a red flag?Frankshaft wrote: ↑Thu Sep 06, 2018 12:31 pmThis. That's why when someone displays a dyno sheet, and I immediately say the dyno is happy, it's cut and dried. That's why the internet marketers block those 2 columns now. They finally figured that out. So, now I point that out, which makes it look worse, because they are knowingly hiding it.
Maybe use this dyno sheet as example or if you have one you can show?
When you see a 383 with a 208 at .050 cam and unported heads, that uses about the same amount of fuel, BUT shows .32-.34 bsfc's, Ahhh, No. So uncorrected power would be 550 or so hp, but the "corrected" power is less? By 40+hp. Nice try. Or an engine showing .299 bsfc's and some crazy power numbers, it's obvious.
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Re: Volumetric Efficiency
Volumetric Efficiency (VE) is an engineering concept that had been used in automotive engine design for several decades. I am not familiar with Density Efficiency (DE), BUT air density is a function of water grains (humidity) and air temperature. Air density occurs naturally and cannot be efficiently changed by human intervention. I believe that we are probably talking about two totally different subjects here.
Bill
Perfect Circle Doctor of Motors certification
SAE Member (30 years)
ASE Master Certified Engine Machinist (+ two otherASE Master Certifications)
AERA Certified Professional Engine Machinist
Perfect Circle Doctor of Motors certification
SAE Member (30 years)
ASE Master Certified Engine Machinist (+ two otherASE Master Certifications)
AERA Certified Professional Engine Machinist