I import a single track audio guitar (recorded on my handheld recorder) into Sonar Platinum and cut it down to just 4 bars of 4 beats in an attempt to set the project tempo and add other midi / drum tracks. I 'apply trimming' and I 'bounce to clip' to make sure there is no hidden data beyond the visible waveform - just 16 beats.
 
After selecting the clip (which begins at beat 1 on the timeline), I have gone to the audio snap palette and turned it on. When I look at the tempo options - it suggests a variety of tempos - with 51 and 102 given 4 dots (assumedly the best matches). However, none of the suggested tempos match the actual tempo. When I use "set project from clip" - it chooses something close to 51. However, from having painstakingly worked out the tempo manually by incremental adjustment - the actual tempo is 87.44 - which is not one of the options suggested or even close. The closest offered tempos are 81 and 93!! What am I doing wrong? 
 
I would be really keen for someone else to try it out with my audio clip which can be downloaded from Dropbox here ...
https://www.dropbox.com/s/stk4loigxzrk34f/Test%204%20bar%20%2816%20beats%29.wav?dl=0 
 
 

Further confusion - when I open the file in loop construction mode - it shows correctly as 16 beats at 87.441 beats per minute - but not in audio snap!

Audiosnap detects 86BPM here, and Set Project from Clip at Clip resolution yields a tempo of 85.82. Setting with a resolution of Beats gave tempos from 83.66 to 92.87. Manually setting just beat 4:04 with Set Measure/Beat At Now gave me 85.72

Thanks Brundlefy for taking the time to check that out for me and for your detailed response - much appreciated!
 
I managed to get very similar results when I imported the file into a new project but interestingly, still slightly different than yours (eg 87.06 from clip compared to your 85.82). I would have expected identical results on different machines with the same material.
 
I went back to my original project and time slipped the other accompanying tracks I have to the 0 marker as per Craig Anderton's tip of the week, then trimmed and bounced all clips, making sure my acoustic guitar part was still the longest of the tracks. The result I get in the original project is 57!! Admittedly, it now gives one of the options as 87, but I was still only using the same audio clip offered here to set the tempo, and not including the other tracks in that calculation. So I'm still a little baffled as to what affects the outcome, which seems to vary considerably.

The difference between your result in the new project and mine is probably due to changes in transient detection algorithm between X3e - no big deal. Right offhand I can't think why the result your original project would be so far off. Are you working from the same trimmed and bounced clip, starting at time zero with no previously existing tempo changes in the project? If the base clip tempo is still mis-detected, anything is possible.
 
I just checked the clip in X3. The average clip tempo was detected correctly at 87 BPM, and I got the same 87.06 on setting the project to clip at Clip resolution in a 44.1kHz project. Initially, I brought it in at my usual default for new projects of 48kHz, and got 86.98. The re-sampling altered the transient detection slightly.

Thanks for checking again Brundlefly - I've been away all day.
 
The only difference from the clip I posted is that my original clip was longer - it was 4 times the length of the one posted, but simply 4 repetitions of that same rhythm pattern at the same tempo. It started at zero on the timeline and all the accompanying clips were trimmed and bounced. I don't know whether the presence of other clips in the project could affect things. I would assume in this case they shouldn't, as they were not any longer than the original track and all played in time with it - and I was setting the tempo in relationship to that specific guitar track.
 
I guess I'll chalk this up to an oddity and try out some other recordings and see what results I get. I have heaps of similar base idea tracks recorded on my handheld that I want to transfer into Sonar projects and get the project tempo matched.

If you want to upload any longer clips or multitrack projects, I can take a look and give some more specific guidance.
 
I generally prefer using Set Measure/Beat At Now to set project tempos. It's much more predictable, flexible and controllable, letting you set tempo changes only where you really need them, and doesn't typically take that much longer given that you avoid the kinds of issues you've run into here. Also, Set Project from Clip has had a bug for a while when setting to Beat resolution that the tempo changes aren't inserted right on beats, which can make for a very messy tempo map.