Dyno VE

[1972ho]

What exactly does VE mean when dynoing an engine I once had my v-6 engine on the dyno and it had 120-130 percent VE.I know it has something to do with the amount of air going into the engine are how the engine is using the air.And is this something that can be used to improve the torque and hp.Thanks

[mag2555]

Could you post the build details if you would on that V6 that attained 130% VE?

[1972ho]

This is a engine that I bought back in nineties from a Busch team DR racing and I dynoed it as soon as I got it and that’s where the numbers were. I have been using it as a drag racing engine and just kind of wanted to know how I could improve on it.

[Rick360]

Dyno VE is calculated by the dyno from an air turbine measuring airflow into the engine. If the engine is held at a steady rpm and the air turbine is accurate then the dyno calculated VE% will only be inaccurate by the amount of air that goes out the exhaust during overlap ... ie-not trapped.

During a sweep test on the dyno the air turbine has lag that will make its reading incorrect. Many engine builders I've seen don't normally use the air turbine when dynoing.

120% is exceptionally high for real VE but 130% is unbelievable.

Rick

[Stan Weiss]

If other items are measure then VE and SCFM can be calculated. One way to double check that an air turbine is calibrated correctly is to measure and also calculate A/F ratio. If they are not the same something is off.

Can you post a copy of the dyno sheet?

Stan

[1972ho]

Yep give me a few.

[maxracesoftware]

What exactly does VE mean when dynoing an engine I once had my v-6 engine on the dyno and it had 120-130 percent VE.I know it has something to do with the amount of air going into the engine are how the engine is using the air.And is this something that can be used to improve the torque and hp.Thanks

typically 8% VE to 10+%VE goes out the Exhaust Port during the Overlap Period
and the Air Turbine does also "Lag" like Rick360 Posted .

here's a quick Simulation of your Info so far
i can get more exact if i knew for sure your actual Compression Ratio + Cylinder Head Flow Numbers + Cam Specs
so i guessed
looks like a 1050 CFM Carb or a Carb that can Flow about 950 CFM to equal 0.7" InHg Plenum Vacuum ??
and the real Air/Fuel Ratio looks about = 13.468535 : 1
looks like VP C14 or C12 ?
and your Dyno Sheets are using the older WinDyn version TQ and HP correction equations
but PipeMax is using the newer WinDyn equations..so there's a small difference

Intake System= 122.36000 VE% as about 8+VE% is going out the Exhaust Port during the Overlap Period

[1972ho]

Let see if I remember the intake port flow was 370,the camshaft was 264@.050 int 272@.050 exh 108 lobe .428 int love .419 exh. with 1.6,1.6 rr,installed 98 center line ,the compression was 14.1,the carburetor was a Holley 850.And are you saying I could use a bigger carburetor.This is my new current roller Ca spec and compression is now at 15.1

[rebelrouser]

130% does seem off the wall. Our dyno at school has a regular air turbine type hat that goes on the carb. I messed with it for about a year and the numbers just did not make sense. Had a guy from the dyno company come for a service call for another issue, and when I mentioned the air turbine he said he could put a correction number in the software. I had sent it back a couple times and they just told me it was OK. We have a super flow bench, so I rolled it over by the dyno and put the hat on the bench. fired up the flow bench and read the numbers both on the bench and the dyno screen. He adjusted the numbers on the dyno software until they matched the CFM on the flow bench. It's worked great ever since, and the numbers are believable now.

[maxracesoftware]

Let see if I remember the intake port flow was 370,the camshaft was 264@.050 int 272@.050 exh 108 lobe .428 int love .419 exh. with 1.6,1.6 rr,installed 98 center line ,the compression was 14.1,the carburetor was a Holley 850.And are you saying I could use a bigger carburetor.This is my new current roller Ca spec and compression is now at 15.1

your Holley 850 CFM Carb looks plenty large enough for 7500 RPM and 504.4 HP
and might be flowing 870 CFM ?

your new Cam Specs are better for your Engine than the old Cam

the Peak Torque is pretty low for the amount of Peak HP
so that shows Header Specs and/or Induction Lengths + CSA are not the best for 7500 RPM

still showing about = Intake System= 122.44000 VE% and 13.474442 : 1 Air/Fuel Ratio

15:1 Compression Ratio will help out

what about a Vacuum Pump too ? , along with Q16 Race Gas ??

[1972ho]

The engine in the car has already ran two tenths quicker and 3 to 4 mph than the old set up in 5000 ft DA.and the sixty ft has went from 1.40 to 1.33 so it’s making more hp and torque than the dyno set up.Thanks

[mk e]

130% does seem off the wall.

I know for certain there are pushrod engines in the 138-140 range and ohc engines that hit 145....not to say a pushrod engine couldn't but i have no direct knowledge of that.

The numbers are a bit a function of how you define VE....there are several VERY long and angry threads on this topic. Normally its easiest to measure the amount of air that is pumped, so total inlet flow you measure with an MAF or similar. Trapped volume is more important but WAY harder to measure so this is generally an estimate.

The numbers I mentioned are total flow based VE, Larry's -8% to get to trapped VE is probably as good an estimate as you're going to get.....which makes the highest trapped VE pushrod engines right around 130.

[Stan Weiss]

Along with the VE%, the A/F ratio and BSAC numbers look high to me. Do you happen to remember if the dyno had sensors to measure A/F ratio? Note a change in these number does not effect the HP, torque, or BSFC numbers.

Stan

In this example all I did was reduce the A/F ratio by one point

Code: Select all

Engine Size =  270.0665 ci

Dyno Barometric Pressure = 28.88 - Dyno Vapor Pressure = 0.51 - Dyno Air Temperature = 84.0

                                 Fuel           UnCorr  UnCorr UnCorr Correct   A/F
  RPM   Horse  Torque   BMEP    lb/hr     BSFC      HP  Torque   BMEP  Factor  Ratio    SCFM    VE%
 5500   395.8   378.0  211.1   173.60    .4800   361.7   345.4  192.8  1.0945  12.30   466.2  119.7
 5600   399.1   374.3  209.0   178.40    .4900   364.1   341.5  190.7  1.0962  12.20   475.2  119.8
 5700   408.2   376.1  210.0   174.40    .4700   371.1   341.9  190.9  1.1000  12.50   476.0  117.9
 5800   412.8   373.8  208.7   177.20    .4700   377.0   341.4  190.6  1.0949  12.50   483.6  117.7
 5900   422.6   376.2  210.1   172.00    .4400   390.9   348.0  194.3  1.0811  13.00   488.2  116.8
 6000   427.0   373.8  208.7   166.10    .4200   395.5   346.2  193.3  1.0798  13.80   500.5  117.8
 6100   440.4   379.2  211.7   173.40    .4300   403.3   347.2  193.9  1.0922  13.60   514.9  119.2
 6200   437.7   370.8  207.0   170.20    .4200   405.2   343.3  191.7  1.0802  13.90   516.5  117.6
 6300   449.7   374.9  209.3   169.40    .4100   413.2   344.4  192.3  1.0884  14.50   536.3  120.2
 6400   453.2   371.9  207.7   174.90    .4200   416.4   341.7  190.8  1.0883  14.20   542.3  119.6
 6500   452.4   365.5  204.1   181.40    .4400   412.3   333.1  186.0  1.0972  14.00   554.5  120.4
 6600   460.6   366.5  204.6   185.40    .4400   421.4   335.3  187.2  1.0930  14.00   566.7  121.2

[mag2555]

At 7K rpm when you divide the fuel used by the BSFC number you get 460 uncorrected HP , so the corrected 500 hp is plus like 8% greater.
Is that not getting to be a bit of a stretch for a correction factor?