calibration problems

[powellmachine]

I got a set of cal plates from mr. bruce, put,em on my bench, here is what I found, 50cfm plate is low by 8.4 cfm the 300 plate reads high by 43 cfm, I put them on top of my head adapter (4.150" bore) 50 plate read 57 no change @ 300, but the kicker is my bench is stingy with a head?? I have flow #'s for sevral heads and compared to most published #'s im pretty close, I fully relize this is not the rite way to go about it but something is a mis with the cal plates, (not that thay are wrong) but with my pitot tube its doing something funny to the air???? talked with bruce a couple times ( very helpful!!) but we could come to no sensible conclusion to solve the problem with the cal plates. there may not be a problem @ all but I would like to no for sure, as I am building a pts bench and will sell this one and I want it to be accurate, it is super repetable, day to day week to week, I get the same #'s within 1-2 cfm ...its a jkm 600 purchased new around 98-99,

any ideas??

[jfholm]

Do you have any pictures and specs of you bench you can post? Need to see bends, tubing size, how much tubing length before and after the pitot itself.

John

[Brucepts]

John, It's a JKM flowbench pretty much straight runs of pipe up and down.

We've run through a bunch of ideas, moved the pitot probe location, used the plates on and off the head adapter.

I think our next step that we discussed is to have Daniel send a head to me and flow it on my bench and see what numbers I get and then go from there.

[jfholm]

John, It's a JKM flowbench pretty much straight runs of pipe up and down.

We've run through a bunch of ideas, moved the pitot probe location, used the plates on and off the head adapter.

I think our next step that we discussed is to have Daniel send a head to me and flow it on my bench and see what numbers I get and then go from there.

Probably the best idea, Bruce. Good luck. I hate chasing gremlins

[Monte442]

Just wondering if there are any updates on this, I am going through the same thing with my JKM 600, not sure what to do.

[powellmachine]

what I have found is my bench is good with a head (what I mean is my #S are close to what other are getting and its dead nuts repeatable), it must be straighting out the air, I notice when I have a bad port design and the air is turbulent it does the same thing and the test pressure is very jumpy, kinda a good feature, u no u have a turbulent port right away, one thing I can say is if my bench shows improvements the clock at the end of the track and the gage on the dyno are in agreement , I think at some point im going to put a flow straightner in the pipe between the pitots (waffle cone) I think this may help,