Superflow inclined scale conundrum - Things that make you go Hmmmmmmmm

[vanirv6]

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[84-1074663779]

It sounds to me like Superflow may consider a possible 6% error quite acceptable in the great scheme of things. That would not surprise me in the least.

I have believed for quite a long time that it is quite possible to build a home made flow bench that will out perform a deliberately compact mass produced commercial design, provided enough care and thought goes into it.

Just because something is very expensive does not always make it better.

[larrycavan]

Figures were posted for the SF300 and 600 in the forum along with the other criteria you mention regarding the fluid SG. The 600 factory calibration sheet in CFM for the 600 showed the following calibrated flow ranges.

35.5
71.5
151
299
451
604

Taking the calibration sheet figures as accurate for standard conditions, I would tend to lean on your calculated verticle pressure. The 600 advertises +- 1% for accuracy at full scale. That's 6.04cfm in itself.
Best Regards,
Larry

[vanirv6]

Tony,

I agree 100%. Interesting how hung up an industry can get based solely on what evolves as the "industry standard" in almost any technical arena. Unfortunately, many other tangent technoilogies follow the same trend when they base their functionality on those same standards (like engine simulation and flowbench software). I hate that.

Larry,

Actually, every SF-600 has it's own unique calibration card and there are different numbers for both intake and exhaust flow correction. The last SF-600 bench I worked on had the following calibration figures:

Intake Exhaust
36.3 40.2
71.8 78.3
148.5 158.0
293.9 319.7
440.1 481.5
591.5 645.8

Pretty sloppy bench IMHO. This whole deal really bends my clam digger for some reason.

Vanirv6

[larrycavan]

It depends on how you look things. To me, the fact that superflow includes the calibration sheets shows me they are very much trying to deliver a piece of equipment that will produce accurate measurments.

As for the variances between machines consider how much the cost may increase to have each one identical the next before it went out the door to the customer and the increase in cost for that level of accuracy, especially when it really doesn't matter because the machines are close enough for what their purpose is.

They also include a calibration plate and instruct that it be used to calibrate your bench at the start of each day and use the flow reading as your correction factor. To me, that's the real key to comparible measuring between flowbenches.

As far as I know, it wasn't until they began to manufacture the 600 that they included the actual flow range sheet with the machine. I consider that to be an act of good will honesty and a validation of the difficulties faced in trying to produce a meachine that measures air flow with 100% accuracy.

It's important to get past CFM numbers as the main focus when working with a flowbench. We build our own flowbench,take a given orifice size, run the calcs and determine it should flow XXXcfm of dry standard air at a chosen pressure drop. There's the ballpark to play in.

Once you have your base flow ranges, what truly matters most is the accuracy of your manometer calibrations. Being able to accurately measure increases or decreases in flow on your particular flowbench, in your particular shop and your particular location is what you are after. You make some changes and didn't see a positive result so you stop and think to yourself....I just cut this port bigger, decreased the velocity and gained nothing for the effort....or I put a 30 degree back cut on the intake valve and gained 9% in my 40cfm range at .050" lift.... Knowing you are reading an accurate 9% change is far more valuable to you than what that calcs out to be in CFM.

As long as you are certain that your inclined and vertical manometers are calibrated accurately, the actual CFM is only a general range of a calculated measurement. Accurate readings of percentage changes is what matters. It doesn't matter if it was 9% of 40cfm or 48cfm. You either got a 9% increase or you didn't and you have a machine that you are confident is reading accurately as far as percentages of flow are concerned.

Best Regards,
Larry

[vanirv6]

Larry,

I think you've missed my point. Granted, everything you say has certain merit. However, the one thing that is missing in your equation is tangent technologies like engine simulation software. I'm not talking about low-end bits like Desktop Dyno and the like. I'm talking about packages like Dynomation and WAVE that rely heavily on flow figures based on Superflow numbers. Unless you are willing to skew/adjust/manipulate your numbers to correlate with the Superflow numbers, you can't really rely on the outputs of these programs with the confidence that you would expect.

My intention was to point out what may be a "stacked tolerance" condition (perhaps intentional) that has an inherent _potential_ flaw. By ignoring it, that flaw is introduced into every subsequent operation that in any way depends on a "real" CFM number. Scientifically speaking, this is no way to conduct tests. You make mention of the accuracy of the Superflow bench. I ask: accurate compared to what standard?

I'd like to think that many here (not all) are motivated to try to achieve something more than what we are given as "standard". More capacity, more resolution, more repeatability, more accuracy..........more. Others are here to learn and understand more about what the art of flowbench construction is about, and that's great too. However, fundamentally, much of the critical discussion on this board has roots based in what Superflow does and what Superflow says and how our machines compare to Superflow. Some have abandoned the Superflow comparison long ago (Tony comes to mind) but almost anyone that has endeavored to build the MSD-style bench has encountered at least two common issues related to this design: 1) the orifices in the articles don't make sense and 2) the configuration of the inclined flow scale. Invariably, there are two solutions to question #1 that are commonly suggested and those are to build test orifices and have the flowed on a Superflow for comparison (and there is the problem) or base all of your orifice flows on purely calculated numbers of which there are now several iterations. All I'm saying is that evidently, neither option is particularly good depending on how you look at it. If you want to use the available software as it exists, you correlate to a Superflow bench no matter what inaccuracy may be or you base everything on calculated numbers (by picking your favorite equation) and live with numbers that are not directly comparable to any other machine and preclude their reliability with modern software (for example).

In the end, this is probably another strong reason to try to standardize this whole deal ourselves. As suggested elsewhere on this forum, the pitot tube bench guys can get together and establish their standards and the orifice plate bench guys can do the same. The only thing I'm saying is that we should be very careful to not assume the "standard of the industry" is worthy of the title. Perhaps the only thing worth considering in this context is the use of the same orifice diameters for each range and the inverse square law flow scale (0-100%) and that's it?

Just more to think about.

Vanirv6

[Thomas Vaught]

I would disagree that the Super Flow 600 was the first bench to publish actual flow calibration figures.

I have worked on a SF 300 and a SF 1200 that were created before
the SF 600 was ever designed. Both had flow calibration sheets.

I agree that it would be much better if the "orifice guys" came up with
a "Standard Hole" for a given range/ delta P and then everyone determined the variances between manufacturing techniques.

At some point you would have a pretty good "Flow Bench Forum
Standard" for a given orifice/ flow range.

The flow number posted does not surprise me for the one SF600
bench. I don't think SF or anyone ever thought that a SF 600 bench would be exactly 600 cfm.

The 13.5 ratio is the mathamatical increase required to go from
say 400 cfm to say 600 cfm.

The 13.87 number is more like the nember you get in a real world
comparison for the two flow numbers using the change from .826
to 1.91 fluid.

JMO

Tom V.

ps the 6 inch inclined scale is well compensated on the dwyer
manometer with the .826 fluid.

The numbers I posted were for ONE SF 600 unit. Not every unit.

[larrycavan]

[larrycavan]

[vanirv6]

Larry,

I sure hope I wasn't coming off in any way even approaching offensive! If so I very much apologize. That's the trouble with forums......no way to judge a response for "tone". I KNEW I shoulda used them "smileys" In truth, I love this forum and the opportunity for the exchange. Without a doubt, this is one of the most information-rich and useful of all of the forums I monitor and/or participate in. The exchange of ideas, info, technique and specs is absolutely outstanding. I appreciate your taking the time to jump into the discussion. Same goes for Tony and Tommy as well.

Now, I absolutely understand your needs and methods for using your bench and the information it provides. In the end, these machines are sophisticated comparators and that is exactly what you are looking for. Unfortunately (or fortunately, depending on how you look at it), I require something that produces data more in line with that produced by my camshaft testing equipment for the type of work I do. Much of it is not unlike you and many others on the board do, just a bit of a "twist" added in between with very intensive computer simulation development on the front end. Sometimes, that is where a concept remains as we can explore so much "theory" before ever investing in a single part (or at least very few) and a project that proves less than optimum for the intended use can be shelved early at comparatively little cost.

Now, back to the topic: the 13.5" number was evidently supplied by Superflow to Performance Trends for the asking. Interestingly enough there are other software packages that reflect this same figure so it seems possible that there is little reason to doubt this. However, I intend to dig into this a bit deeper to see what I find out.

In the end, I'm not necessarily hung up on CFM numbers. Only the fact that most software programs apply intensive and critical calculations based on accurate CFM figures based on Superflow's method of deriving them and it appears that the this method may skew the actual numbers. What bothers me about this is the cascade effect into other technologies and the dilemma that every independent bench builder must deal with as a result: correlate or not correlate. And not because it's the "right thing to do", but what "everybody else does".

All the best!

[larrycavan]

Vanirv6,

No offense taken at all. Any conversation that promotes thought and understanding is a worthwhile venture. I have a link for you to look at. Take notice as to how the flowbench readings and the cam profile are laid out in excel to compare which head would likely work best with a particular cam. This may be right up your alley and you may already be performing a similar or even more elaborate function. Aslo take notice as to their statement regarding flowbench comparisons.

Also consider that if the CFM results were a little lower or higher, it would not alter the conclusion of how the heads would perform. The comparison would still be valid because both heads would have posted different CFM numbers to the same degree of + or -.




Without knowing the specifics of your software I'm at a loss to discuss particulars but here are some things I think are important to keep in mind. I suspect you've already thought long over them but in the spirit of sharing concepts, here goes.

Predictions of how an engine will react through any calculated means are always theoritical. As such, it would seem to me that using either of the verticle pressure specs would provide reasonably accurate predictions. If the lower figure 13.5 is used, one could only hope that if the predictions worked out as expected with that figure and if the higher 13.8 figure was more real world accurate, then the gains realized may be greater than anticipated.

I can agree with the frustration of not being able to obtain an exact standard measurment when your calculations depend on it. But realize that it's truly unimportant even for what you are attempting to do. Whatever number you select is your baseline. Whatever you design can be tested and a correction factor applied between predicted and real world performance. It can then be used throughout the entire development process of all your other projects. Isn't that effectively what Superflow does by including not only a calibration sheet but also a calibration plate with each flowbench?

One thing does intrigue me however. I bought a Superflow 110 calibration plate. I wonder if I had half a dozen of them if they would all flow the same........On second though, I better not even go there......The give a +- 4% in their manual. I wonder if that's for air condition variances or manufacturing tollerences......or both.

It would be interesting to have a calibration plate that we could all ship to each other in turn, flow it on our own benches and see what we get for numbers.


Best Regards,
Larry

PS...Great discussion...keep 'em coming!

[vanirv6]

All,

I just had a detailed email exchange with the owner of Performance Trends regarding this subject and am very happy with what I have been told. In short, the newest verion of their Port Flow Analyzer software no longer takes into account the flow scale prtessure. Instead, they go by the full scale CFM and the reading on the 0-100% manometer and that's it!

As simple as this sounds, it is a huge step in the right direction where our DIY benches are concerned as it allows a freedom to establish and characterize YOUR bench in this software without being artificially force-fit into the SUperflow mold. Now, if only the rest of the software manufacturers would line-up with this thinking, l could go back to thinking about other flow-related thingys.

Just thought I'd share!

[Mouse]

[larrycavan]

[larrycavan]