SF 600 problem - Any help or advice would be appreciated

[larrycavan]

Good idea Tom...

Larry

[John F]

Well I drained all the old oil out of my manometers and replaced it with fresh gauge oil of the proper specific gravity, but to no avail. Unfortunately it made no difference whatsoever.

Mouse suggested there could be a leak in one of the lines. Any further suggestions how best to trouble shoot this? I've looked them all over, but don't see anything obvious. Specifically what lines, if leaking, would you suspect might cause the bench to read high like mine is?

Just to review the symptoms:

The cabinet does not leak. With the Superflow test orifice plate on and both holes sealed shut, the bench shows zero flow at test pressures as high as 47".

With both holes open on the Superflow test orifice plate, on intake flow range four, the % flow should be about 80% at 25" - mine is reaching 80% at only 13.5".

A cylinder head that flows 414 cfm on a friend's SF-600 bench is flowing over 500 cfm on my bench!

Any more suggestions?

Thanks,
John

[Mouse]

Is the test pressure manometer a U tube?

[larrycavan]

I recall someone else having a problem like this and it turned out to be the manometer switch causing it. If memory serves me correctly, the investigation revealed that dirt had been sucked into the switch and ultimately wore a groove into the carbon block inside. After replacing the switch, the bench read correctly.....have a look at that...

Larry C

[Scott]

How did you get from having 25% "leakage" to now having none, what changed?
Check out the connections and the condition of the pressure taps inside the bench.
Also, maybe have a look through the top at the orifice plate and make sure nothing has happened that could possibly have your orifice disc out of sync with the planet, rotate it through the ranges and look at it. You said this thing had a hard life, so you never know, the guy could have been porting cylinder heads on it.

You can make a simple manometer to use in place of each of your others to rule them out as a problem, it doesnt even need to be inclined, but I doubt that the manometers are the problem.

There are a couple of other eddie knobs on those, like for "intake above 150 cfm" or somthing(can't remember)
check to see what those are doing as well, you may need to take the back off this thing to get to the bottom of this.
I have a feeling she's not a Virgin.

****Before anything else please gently measure your test orifices and post the sizes so we ave all the facts. They are sharp edged ,I presume?

Scott

[larrycavan]

I found the post I was thinking about...it's a low reading situation rather than a high reading but still worth the investigation.



Scroll down to Bill Jones...

[John F]

I had the steel top deck plate off the bench in order to take a closer look at things. The rotating orifice disc looks to be in fine condition. I was surprised how easily the top lifted off, so I suspected it might not be sealed well. After cleaning things out well - including removal of valve locks, an old razor blade, and some coins - I then put the top back on with a good bead of silicone. After doing so, I'm getting zero cabinet leakage; however, the bench still reads high just as it did before.

I also removed the back cover to take a look at things. I didn't see any obvious problems. All the mechanical controls seem to work fine.

The test orifice plate has two sharp edged holes. One is 1.875" and the other is .312". With both holes open, Superflow says they should flow 238 cfm at 25" (tested using flow range four). My bench reads 328 cfm (tested on range five, as four was maxed out).

The test pressure manometers are the typical tall 48" Dwyer u-tubes. I have tried both vertical manometers with the same results.

[Mouse]

[gofaster]

I had a problem with my SF-110 a while back where the test pressure was not holdong steady, it kept falling off. It turned out to be caused by a loose electrical connection involving a bolt through a bulkhead attaching two connectors on opposite sides of the wall. It had worked loose, was getting very hot, and was burning a hole in the inside of the bench while I was flow testing a port. It caused enough of an internal leak that it had me chasing depression on my vertical manometer, and gave me fits until someone else told me something was burning.

Maybe you knocked something loose between transporting and cleaning the bench.

[larrycavan]

Those are the same hole sizes for the 110 test plate. At 10", SF claimes 152.3 CFM for that plate. Using their conversion formula to 25 it works out to 240.8 CFM.

Using your value of 328CFM that you're getting during a test, it should take roughly 48" of depression to achieve that value through both holes of the test plate. If everything is OK with your cabinet and flowdisk then that would indicate that your verticle manometer is reading lower than the actual test pressure inside the top plenum.

To verify that, you could fabricate a simple u tube manometer and T it in with your test pressure manometer to see if they match. Remember to double the u tube value like Mouse pointed out.

That plate is also sharp edge on the intake side and slightly radiused on the exhaust side which will change the CFM values for exhaust.

Have you flowed it on exhaust and does it read quite high on exhaust testing as well?

You might disconect the test pressure manometer probe and blow it out. Blow out the line and double check the switch. Check it at every connection point from the plenum right on through to the manometer.

The flowdisk holes haven't changed. The problem has got to be cabinet related or manometer related.

Seal the 1.875" hole with the provided rubber plug and set your bench to the lowest range. Flow the .312" hole and see what you get. It should be around 17CFM @ 25

Larry C

[Mouse]

If you have a syringe that you can attach to the test pressure port, you can place a vacuum on the test pressure u tube and see if it holds.

[John F]

I spoke with Bob Akers at Superflow this morning and he was very helpful. He was perfectly happy to talk to me about my problem even though I'm not the original owner of the bench. In fact, he went so far as to register me as the new owner of the bench, so my name will be associated with the serial number for future reference. I just wanted to be sure to let you all know that my first encounter with Superflow seems not to be typical - I just got the wrong end of the horse on the phone.

Turns out the problem seems to be with my gauge oil in the incline manometer. The company I dealt with when I bought it buys large quantities and then parcels it out in smaller bottles with no labels on them. What they were refering to as "blue" gauge oil was actually Dwyer violet oil with a specific gravity of 1.00. The proper blue oil should have a specific gravity of 1.91. I have a container of blue on the way to me from Superflow which should fix the problem.

Anyone have a way to determine if my flow numbers make sense knowing that the specific gravity of the oil in the incline was 1.00?

Thanks to all of you for your help,
John

[Mouse]

They seem to make perfect sense now.

[larrycavan]

Yes, with lighter than calibrated for oil in the inclined, it will read higher than it should. To actually run the numbers to see how close you are, the calibration CFM of range 5 needs to be known.

[John F]

Range five has a calibration cfm of 450.