Sure, I Have Many Reasons
BTW, I'm at 837 feet above sea level, so based on:
http://www.asesystems.com/vacuum-lifters/the-effect-of-atmospheric-pressure-on-vacuum-level/
The differences would be much greater (>13%) than what's been discussed here so far, assuming no other mitigating factors.
First, do you know of videos showing a 15 year old S514's suction measured at the canister and/or hose end? I'd like to see one.
1) When I do "blind" measurements like this, I can only report what's measured.
2) How many samples of the S514 have you thoroughly tested? I only have one sample. I can't comment on the variances of one sample.
3) Due to the effects of aging, one would expect different results than when new.
4) Do you test your machines warmed up or cold? I've seen up to a 5% difference so far depending on internal motor temperature.
5) Do you keep a formal log of your measurements like I do (obviously) or is that suction range of 85-90 from memory?
6) Did you see the rather large 30.8 CFM canister to hose loss? That's a bit excessive and may point to a leakier than normal hose. After all, it's been beat up for 15 years.
So considering the excessive CFM loss from the hose, I would say that's where some of the lower suction numbers come from. But despite that, it still has great airflow not only at the hose, but also at the power nozzle.
Bill