Volumetric Efficiency

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swampbuggy
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Volumetric Efficiency

Post by swampbuggy » 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.

digger
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Re: Volumetric Efficiency

Post by digger » Thu Sep 06, 2018 7:18 am

VE is akin to torque not power

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Cougar5.0
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Re: Volumetric Efficiency

Post by Cougar5.0 » Thu Sep 06, 2018 7:40 am

According to this article, VE is proportional to HP:

VE = horsepower x 4235 / CID x rpm

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Re: Volumetric Efficiency

Post by digger » Thu Sep 06, 2018 7:50 am

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

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Re: Volumetric Efficiency

Post by pdq67 » Thu Sep 06, 2018 9:12 am

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

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Re: Volumetric Efficiency

Post by randy331 » Thu Sep 06, 2018 11:52 am

swampbuggy wrote:
Thu Sep 06, 2018 7:07 am
We can all agree that VE is King in power production,
Fuel flow and BSFC is all there is to it.

Randy

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Re: Volumetric Efficiency

Post by David Redszus » Thu Sep 06, 2018 11:58 am

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.
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.

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

Post by engineguyBill » Thu Sep 06, 2018 12:21 pm

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.
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Re: Volumetric Efficiency

Post by Frankshaft » Thu Sep 06, 2018 12:31 pm

randy331 wrote:
Thu Sep 06, 2018 11:52 am
swampbuggy wrote:
Thu Sep 06, 2018 7:07 am
We can all agree that VE is King in power production,
Fuel flow and BSFC is all there is to it.

Randy
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.

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Re: Volumetric Efficiency

Post by GARY C » Thu Sep 06, 2018 1:45 pm

Frankshaft wrote:
Thu Sep 06, 2018 12:31 pm
randy331 wrote:
Thu Sep 06, 2018 11:52 am
swampbuggy wrote:
Thu Sep 06, 2018 7:07 am
We can all agree that VE is King in power production,
Fuel flow and BSFC is all there is to it.

Randy
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.
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?
Maybe use this dyno sheet as example or if you have one you can show?
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Re: Volumetric Efficiency

Post by Stan Weiss » Thu Sep 06, 2018 2:06 pm

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

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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We have a package of more than 3000 DFW or FLW Files

digger
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Re: Volumetric Efficiency

Post by digger » Thu Sep 06, 2018 5:08 pm

David 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.
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 VE

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Re: Volumetric Efficiency

Post by Firedome8 » Thu Sep 06, 2018 6:01 pm

VE is a misnomer DE (density efficiency) is what the engine is seeing .
I think...please correct and or comment on this thought.

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Re: Volumetric Efficiency

Post by Frankshaft » Thu Sep 06, 2018 6:16 pm

GARY C wrote:
Thu Sep 06, 2018 1:45 pm
Frankshaft wrote:
Thu Sep 06, 2018 12:31 pm
randy331 wrote:
Thu Sep 06, 2018 11:52 am


Fuel flow and BSFC is all there is to it.

Randy
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.
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?
Maybe use this dyno sheet as example or if you have one you can show?
I would say that dyno is correct. Not happy. Uncorrected is 389 hp. With a realistic correction factor, it's right in the ballpark​

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

Post by engineguyBill » Thu Sep 06, 2018 9:14 pm

Firedome8 wrote:
Thu Sep 06, 2018 6:01 pm
VE is a misnomer DE (density efficiency) is what the engine is seeing .
I think...please correct and or comment on this thought.
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

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