Dyno vs Flowbench - Comparing Results

[larrycavan]

Somewhere out here on the .net may be a forum where people are trying to compare dynos......then again....I doubt it.....seems to me it's accepted that comparing dyno results is about as meaningful as comparing flowbench types....

Pitot - Orifice.....which is better? Oh...forgot all about LFE....best not do that and offend anyone in that crowd...

Take a given pro headporter / tuner and whatever type of bench he's using, take it away and substitute it with another type....Do you think his work will suffer as a result? Do you think the quality of his craftsmanship will diminish?

Take his ported head and flow it on 5 different flowbenches....then bolt the thing on the engine it was developed for....then take it and dyno it on 5 differenet dynos.....tune for best results on each dyno...[that would be interesting]

Lastly, take the vehicle to the strip and lay down some runs.... The results yield XXX MPH with Y.YYY E.T... and the owner of the vehicle is satisfied with the achievement...

Which flowbench....dyno...is responsible for the end result?

THE POINT -

A guy that ports heads for a living can use any flowbench and perform quality work....the numbers are what they are...calculated potentials may well vary from real world results BUT I have a feeling that no matter which flowbench or which dyno the guy is accustomed to...swap that equipment with something else and the guy will adapt to the equipment and ultimately yield the same level of work...


Larry C

[Mousehouse1]

Larry I have found that every flow bench is different. There are to many variables to consider. What size fixture was used, was there a radius used, was there a pipe used? To many things can change between benches to get the same exact numbers.

I have used one of my heads and had it flowed on 4 different benches. They were originally flowed on Chads, then a super flow 110, then a super flow 600 and then mine. Each of the super flow benches used a 4.030 size fixture. Both of their numbers were off around 35-40cfm. My bench and Chad's were within 10-15cfm.

Like you were saying if a head porter does a good job and flows your head on his bench and then you take to another guy and have it flowed it might not flow the same. Most if not all of the aftermarket head companies inflate their figures.

[gofaster]

Larry, your final statement pretty much sums up one of my basic beliefs. As long as the bench repeats reliably, a porter can duplicate his efforts and maintain quality in his products.

The bench keeps me honest. A port that I do on Monday morning usually tests better and needs less touch up work than one I do Friday night (or worse yet, pre-dawn Saturday and it has to be running TODAY).

After playing with other people's benches with greater depression than what I'm using now, I can see that it helps the r&d along as problems and gains seem to show themselves more clearly at the higher depression.

My only experience with Dyno's has been with little DynoJet units. They were disappointing. Once a bike was tuned on the DJ, I'd have to go down the road and re-tune. I do not currently own a dyno, but there is a big hill outside of town that serves me well for tuning when weather permits.

In time, I would like to look into dyno's in greater depth. Maybe that will be a good project for next winter. First the new flowbench project!

[Thomas Vaught]

The SF110 has never matched the SF600 benches in numbers as the SF110 max cfm is 185 or so cfm vs a SF600 being much higher. The designs are totally different too which I would suspect would alter the numbers provided.

A Laminar bench much be correctly precisely for all of the ambient conditions including if a heater comes on in the winter in a garage.

Pitot tube and Orifice benches tend to be more consistant but I will say I have never seen two SF-600 benches with the same calibration even though the orifice diameters were close.

My opinion, the bench is a TOOL, period.

As was mentioned by Larry, the operator/ porter who takes the info and uses it to his benefit will see the most gains. I have also observed that a porter who works on several different makes of heads etc will be able to make any head flow well vs a guy who only works on one type of head, as at some point, his "ideas" on how to "fix the head" tend to dry up. JMO

Tom V.

[larrycavan]

[Mousehouse1]

[color=#000000]Here is a little information about using different cylinder head fixtures. Thought it was interesting. I wonder how accurate it is?

Stock 351N Ford Head

Intake Intake

4.030 bore 4.155 bore
.100 69 70
.200 136 137
.300 185 185
.400 213 215
.500 232 233
.600 244 245

Ported

[Jesse Lackman]

Recent real world dyno vs flow bench numbers.

Engine Mopar 360 dyno mule Magnum heads 2.02/1.625 SS valves. The only change was porting.

Unported intake flow;

0.200 123.6
0.300 187.3
0.350 208.5
0.400 224.5
0.450 235.1
0.500 231.1
0.550 231.1




Ported intake flow;

.200 132
.300 193
.350 218
.400 239
.450 257
.500 260
.550 252




I didn't have time to really tune the ported combo and as you can see the intake port wasn't happy. The flow testing was done an a SF110 about 40 miles away which doesn't make it easy to really optimize the ports. This engine is going back on the dyno in the next few months for extensive testing of a few different Magnum replacement heads. The short block will be left alone. It is pretty easy to swap heads on the dyno.

I've hooked up with "automotivebreath" and this groovy testing will happen at the same time;

[larrycavan]

Jesse

I'd like to run that through pipe max and see what it crunches.

Do you have:

Bore
Stroke
Rod Center to Center length
Cam data @ .050 & Lobe Center and LSA
Valve Sizes
CR

Larry C

[larrycavan]

Actually there's a 360 already in Pipe Max. I adjusted the Ve to get the CFM of your heads lined up....have no idea if the cam data is anywhere near correct...

371.694 Cubic Inches @ 6900 RPM with 101.0 % Volumetric Efficiency PerCent
Required Intake Flow between 237.7 CFM and 251.0 CFM at 28 Inches
Required Exhaust Flow between 187.2 CFM and 202.3 CFM at 28 Inches

600 RPM/Sec Dyno Test Low Normal Best
Peak HorsePower 507.8 517.2 526.7
Peak Torque Lbs-Ft 428.5 436.5 444.4

HorsePower per CID 1.366 1.392 1.417
Torque per Cubic Inch 1.153 1.174 1.196

BMEP in psi 173.9 177.1 180.3
Carb CFM at 1.5 in Hg. 750 834 918

Target EGT= 1404 degrees F during 4 second 600 RPM/Sec Dyno accel. test
Octane (R+M)/2 Method = 90.8 to 92.9 Octane required range
Air Standard Efficiency = 59.457 % for 9.460:1 Compression Ratio

Peak HorsePower calculated from Cylinder Head Flow CFM only
600 RPM/Sec Dyno Test Lowest Average Best Potential
Head Flow Peak HP = 346.7 541.6 606.5

----- Engine Design Specifications -----

Engine Size CID = 371.694 Intake Valve Net Area = 2.667
CID per Cylinder = 46.462 Intake Valve Dia. Area = 2.776
Rod/Stroke Ratio = 1.710 Intake Valve Stem Area = 0.109
Bore/Stroke Ratio = 1.135 Exhaust Valve Net Area = 1.901
Int Valve/Bore Ratio = 0.462 Exhaust Valve Dia. Area = 2.011
Exh Valve/Bore Ratio = 0.394 Exhaust Valve Stem Area = 0.109
Exh/Int Valve Ratio = 0.851 Exh/Int Valve Area Ratio = 0.724

Intake Valve L/D Ratio= .386 Exhaust Valve L/D Ratio= .438
CFM/Sq.Inch = 85.6 to 90.4 CFM/Sq.Inch =93.1 to 100.6

Curtain Area -to- Valve Area Convergence Intake Valve Lift = .470
Curtain Area -to- Valve Area Convergence Exhaust Valve Lift = .400

Intake Valve Margin CC's Exhaust Valve Margin CC's
1.00 CC = 0.0220 1.00 CC = 0.0304
0.50 CC = 0.0110 0.50 CC = 0.0152
0.25 CC = 0.0055 0.25 CC = 0.0076
0.10 CC = 0.0022 0.10 CC = 0.0030

------- Piston Motion Data -------
Average Piston Speed (FPM)= 4117.00 in Feet Per Minute
Maximum Piston Speed (FPM)= 6739.25 occurs at 74.852 Degrees ATDC
Piston Depth at 74.852 degree ATDC= 1.5711 inches Cylinder Volume= 334.1 CC
Maximum TDC Rod Tension GForce= 3128.19 G's
Maximum BDC Rod Compression GForce= 1712.94 G's


------- Current Camshaft Specs @ .050 -------

IntOpen= 37.00 IntClose= 63.00 ExhOpen= 71.50 ExhClose= 33.50
Intake Duration @ .050 = 280.00 Exhaust Duration @ .050 = 285.00
Intake CenterLine = 103.00 Exhaust CenterLine = 109.00
Compression Duration= 117.00 Power Duration = 108.50
OverLap Duration = 70.50 Lobe Center Angle (LCA)= 106.00
Camshaft Advanced = 3.00 degrees




-Recommended Camshaft Valve Lift- - Induction System Tuned Lengths -
Minimum Normal Maximum Best Length= 14.040 2nd= 11.051
Intake = 0.641 0.684 0.727 3rd Best= 8.966 4th Best= 7.543
Exhaust = 0.573 0.611 0.650 Plenum Runner Max Entry Area = 3.911
Max-effort Intake Lift = 0.816 Minimum Plenum Volume CC = 980.7
Max-effort Exhaust Lift = 0.776 Minimum Plenum Volume CID= 59.8

Minimum Intake Valve Lift to prevent Choke = .713 Lift @ 6900 RPM



------- Operating RPM Ranges of various Components -------

Camshaft Intake Lobe RPM = 7116 Exhaust Lobe RPM = 7155
Camshaft's Intake and Exhaust Lobes operating RPM range = 5126 to 7126
Note=> Lobe RPMs are valid only for conventional 2-Valve Pushrod Engines

Current (Intake Valve Curtain Area -VS- Time) Choke RPM = 6808 RPM

Intake Valve Area + Curtain Area operating RPM Range = 4932 to 6932 RPM

Intake Valve Diameter RPM Range = 4688 to 6688

Intake Flow CFM @28in RPM Range = 4812 to 6812


Best estimate RPM operating range from all Components = 4832 to 6832

Note=>The BEST Engine Combo will have all Component's RPM Ranges coinciding




--- Cross-Sectional Areas at various Intake Port Velocities (@ 28 in.) ---
133 FPS at Intake Valve Curtain Area at .726 Lift
205 FPS at Intake Valve OD Area and at Convergence Lift = .470
254 FPS 90% PerCent Rule Seat-Throat Velocity CSA= 2.248 sq.in. at 6900 RPM
350 FPS Velocity CSA= 1.628 sq.in. at 6900 RPM Port Sonic-Choke with HP Loss
330 FPS Velocity CSA= 1.729 sq.in. at 6900 RPM Smallest Useable Port CSA
311 FPS Velocity CSA= 1.834 sq.in. at 6900 RPM Recommended Smallest Port CSA
300 FPS Velocity CSA= 1.901 sq.in. at 6900 RPM Recommended Port CSA
285 FPS Velocity CSA= 2.001 sq.in. at 6900 RPM Recommended Short-Turn CSA
250 FPS Velocity CSA= 2.282 sq.in. at 6900 RPM Recommended Largest Port CSA
225 FPS Velocity CSA= 2.535 sq.in. at 6900 RPM Largest Intake Port Entry CSA
200 FPS Velocity CSA= 2.852 sq.in. at 6900 RPM Torque Loss + Reversion


--- Cross-Sectional Areas at various Exhaust Port Velocities (@ 28 in.) ---
133 FPS at Exhaust Valve Curtain Area at .700 Lift
232 FPS at Exhaust Valve OD Area and at Convergence Lift = .400
287 FPS 90% PerCent Rule Seat-Throat Velocity CSA= 1.629 sq.in. at 6900 RPM
435 FPS Velocity CSA= 1.074 sq.in. at 6900 RPM Sonic Choke at Throat Area
350 FPS Velocity CSA= 1.334 sq.in. at 6900 RPM Port Sonic-Choke with HP Loss
330 FPS Velocity CSA= 1.416 sq.in. at 6900 RPM Smallest Useable Port CSA
311 FPS Velocity CSA= 1.503 sq.in. at 6900 RPM Recommended Smallest Port CSA
300 FPS Velocity CSA= 1.558 sq.in. at 6900 RPM Recommended Port CSA
285 FPS Velocity CSA= 1.640 sq.in. at 6900 RPM Recommended Short-Turn CSA
250 FPS Velocity CSA= 1.870 sq.in. at 6900 RPM Recommended Largest Port CSA
225 FPS Velocity CSA= 2.077 sq.in. at 6900 RPM Largest Exhaust Port Exit CSA
200 FPS Velocity CSA= 2.337 sq.in. at 6900 RPM Torque Loss + Reversion





Intake Intake Curtain Area 300 FPS Velocity Minimum Head
Valve Choke Square Inches Cross-Sect Area Flow @ 28 In
Lift RPM Intake Exhaust Intake Exhaust Int Exh
.050 469 0.295 0.251 0.129 0.106 16.2 13.2
.075 703 0.443 0.377 0.194 0.159 24.2 19.8
.100 938 0.591 0.503 0.258 0.212 32.3 26.5
.125 1172 0.738 0.628 0.323 0.265 40.4 33.1
.150 1407 0.886 0.754 0.388 0.318 48.5 39.7
.175 1641 1.034 0.880 0.452 0.371 56.5 46.3
.200 1875 1.181 1.005 0.517 0.423 64.6 52.9
.225 2110 1.329 1.131 0.581 0.476 72.7 59.5
.250 2344 1.477 1.257 0.646 0.529 80.8 66.2
.275 2579 1.624 1.382 0.711 0.582 88.8 72.8
.300 2813 1.772 1.508 0.775 0.635 96.9 79.4
.325 3048 1.920 1.634 0.840 0.688 105.0 86.0
.350 3282 2.067 1.759 0.904 0.741 113.1 92.6
.375 3516 2.215 1.885 0.969 0.794 121.1 99.2
.400 3751 2.362 2.011 1.034 0.847 129.2 105.9

Intake Intake Curtain Area 300 FPS Velocity Minimum Head
Valve Choke Square Inches Cross-Sect Area Flow @ 28 In
Lift RPM Intake Exhaust Intake Exhaust Int Exh
.425 3985 2.510 2.136 1.098 0.900 137.3 112.5
.450 4220 2.658 2.262 1.163 0.953 145.4 119.1
.475 4454 2.805 2.388 1.227 1.006 153.4 125.7
.500 4689 2.953 2.513 1.292 1.059 161.5 132.3
.525 4923 3.101 2.639 1.357 1.112 169.6 138.9
.550 5157 3.248 2.765 1.421 1.165 177.7 145.6
.575 5392 3.396 2.890 1.486 1.217 185.7 152.2
.600 5626 3.544 3.016 1.550 1.270 193.8 158.8
.625 5861 3.691 3.142 1.615 1.323 201.9 165.4
.650 6095 3.839 3.267 1.680 1.376 210.0 172.0
.675 6330 3.987 3.393 1.744 1.429 218.0 178.6
.700 6564 4.134 3.519 1.809 1.482 226.1 185.3
.725 6798 4.282 3.644 1.873 1.535 234.2 191.9
.750 7033 4.430 3.770 1.938 1.588 242.3 198.5
.775 7267 4.577 3.896 2.003 1.641 250.3 205.1
.800 7502 4.725 4.021 2.067 1.694 258.4 211.7

Intake Intake Curtain Area 300 FPS Velocity Minimum Head
Valve Choke Square Inches Cross-Sect Area Flow @ 28 In
Lift RPM Intake Exhaust Intake Exhaust Int Exh
.825 7736 4.873 4.147 2.132 1.747 266.5 218.3
.850 7970 5.020 4.273 2.196 1.800 274.6 225.0
.875 8205 5.168 4.398 2.261 1.853 282.6 231.6
.900 8439 5.316 4.524 2.326 1.906 290.7 238.2
.925 8674 5.463 4.650 2.390 1.958 298.8 244.8
.950 8908 5.611 4.775 2.455 2.011 306.9 251.4
.975 9143 5.759 4.901 2.519 2.064 314.9 258.0
1.000 9377 5.906 5.027 2.584 2.117 323.0 264.7
1.025 9611 6.054 5.152 2.649 2.170 331.1 271.3
1.050 9846 6.202 5.278 2.713 2.223 339.2 277.9
1.075 10080 6.349 5.404 2.778 2.276 347.2 284.5
1.100 10315 6.497 5.529 2.842 2.329 355.3 291.1
1.125 10549 6.644 5.655 2.907 2.382 363.4 297.7
1.150 10784 6.792 5.781 2.972 2.435 371.5 304.4
1.175 11018 6.940 5.906 3.036 2.488 379.5 311.0
1.200 11252 7.087 6.032 3.101 2.541 387.6 317.6


Formula=> Average_CSA = Port_Volume_CC / (Port_CenterLine_Length * 16.387)


Note=> Look at the <Intake Choke RPM> column , scroll down to where the
Choke RPM matches the closest you want Peak HP RPM to occur at ,
then that Valve Lift is the MINIMUM Lift required at that Peak HP RPM


Note=> To account for Valve Lash Loss and ValveTrain deflection Lift losses
it is highly recommended that you use the Maximum recommended
Camshaft Valve Lift values , ... also the Maximum-Effort Lift values
are the highest Lift values that should be attempted.


Note=> The Cylinder Head Flow CFM column is the LEAST CFM that is required
to attain that RPM .


Also look across the <Recommended Port Cross-Sectional Area> column ,
those Intake and Exhaust areas are what's required at that RPM of Peak HP

If the <Curtain Area/Time Choke RPM> is lower than your Peak HP RPM input
and if your Cam's Intake Valve Lift is adequate, then that indicates the
Engine is being choked by these possiblities=> 1) Intake Valve OD too small
2) Cylinder Bore diameter is too small, and is limiting Intake Valve size

You cannot achieve 125 % or greater Trapped Volumetric Efficiency % if the
<Curtain Area/Time Choke RPM> is lower than your Peak HP RPM input


Due to differences in FlowBenches and Dynos, the required Intake and Exhaust
Flow CFM @28in. may be 20-30 CFM lower and 20-80 HP lower than your Dyno or
your FlowBench . CFM Flow Lag Times will often cause the required Peak CFM
Flow to occur at different Crank Angle Degrees, than what PipeMax predicts.


Note=> HorsePower and Torque data are corrected to SAE J1349-STD
29.92 in.Hg. Barometer, 60.0 deg.F, 0.0 % Humidity, 0.0 Ft Sea-Level
and correlate to a Dyno test acceleration rate of 600 RPM per Second

PipeMax's HorsePower and Torque data accurately simulates a properly
calibrated Engine Dyno and FlowBench , .... if Data results seem too far
off compared to your Dyno Data, then the Inertia Factor,
Weather Correction Factor, Friction HP Factor, maybe set too high ,
also the Dyno Torque calibration itself maybe set too high
and/or the acceleration test rate is much lower than 600 RPM/SEC,
or a Steady-State test is being used .
Also, you may be setting the Trapped Ve % too high or too low .


<Engine Data> this section determines the calculated HP and Torque data

<Intake Data> this section determines cross-sect. areas , tuned lengths,
Camshaft Specs , and Lift requirements.

<Exhaust Data> this section determines Header Design Specs


PipeMax is primarily a Header Design Program with extra FREEBIE calculations
and lacks enough Inputs to make it a full-blown Engine Simulation Program .
Some of the Inputs will make little or no difference in predicted HP and TQ
but all of the Inputs are needed to predict the correct Intake and Exhaust
System Lengths, Diameters, and Areas.

[Jesse Lackman]

Larry, I'm still getting PipeMax figured out but here is what I came up with;

Well, that doesn't work, how do you copy and paste out of PipeMax?

I'm coming up with 481 for average hp.

4.028 x 3.58

2.02 / 1.625

6.123 C-C rod length

10.5 CR

245 @ .050 .587 lift at valve.

[Jesse Lackman]

It had a 700 cfm Holley DP - I didn't have time to test a bigger one.