looking for leaks - something is goofy with my msd/fp1 bench

[bseibenick]

I know it has been a while since I have posted here but running a full race season plus a few other things have kept me from working on my bench as much as I would have liked. In any case, I am finally trying to finish up my bench. For those who do not remember, I have built an MSD style bench with most of the changes that have been suggested on the forum. I have mouse's FP1 with the 100" pressure sensor and the 3rd sensor for velocity. I had the bench running with 19cfm leakage at 10"wc on an intake leakage test. I tried sealing up some more seams with caulk and all of a sudden something goofy is happening. I have been getting almost 130cfm leakage at 10"wc. If I flip my FP1 to monameter mode, I see that my vertical and incline pressues are the same! I would think ideally that your incline should have 0" when running a leakage test for 0cfm leakage. I have been looking at this for so long that I could use a second opinion on what to look for.

Thanks,
Brian

[86rocco]

One possible thing that could account for that comes to mind immediately and that's a leak in the line going to the low pressure side of the differential pressure sensor on the FP1.

[larrycavan]

[bseibenick]

Larry and all, actually it ended up being a couple things. One was my good and managed to get super glue into one of the the hoses and blocked it. Once that was fixed I was down to 5cfm leakage. Did some more reading and moved my incline pickup tubes away from the orifice disk and all of a sudden 0cfm leakage!. I have a 300cfm@40" orifice disk from Bruce that is 1.85" diameter and I have the cd set to 0.62 in my FP1. With a calibration orifice of 118.8@28" the bench reads 118.9" I have tested leakage all the way up to 70" and still 0 leakage. Tonight I tried the bench on exhaust mode for the first time. I found that I had 0cfm leakage all the way up to 28" (I didn't want to take it too high yet). Using a cd of 0.62 with the exhaust and the same calibration plate of 118.8 I ended up with 119.5cfm. I still have to finish calibrating the exhaust but I think I am finally very close to having a functional bench. When I get some time I will take some pictures and share them with everyone.

Brian

[larrycavan]