Right. I know there are some clever people here… I am trying to get rid of propwash. (Because I am not that good yet to fly away from it.) This is where the quad is flying in dirty air. It’s own wash. It will wobble. You DJI guys may see it on a fast descent.
The way I see it, you have to reduce the latency in the flight controller, so the pids (motor controllers, in easy terms) can keep up with what is happening.
I have fallen out with the betaflight developers, and male pride denies me from asking the question. 
So, I have upped my gyro rate to 32khz from 8, pid loop is 10.something khz from 2. Put a notch gyro filter in with the aid of the blackbox to knock out some motor noise. Running BF357.
My question is… if I reduce the latency by upping the gyro / pid turnaround, and keep the filters to a minimum, will I reduce the propwash?
This has actually helped all my problems. Thank you that man from… Bolton!
Ooooh, !,ya know what?, if there was an answer to this galactic question?.
The Man From Bolton knows it ! 
.
I knew you would have the answer Jeff !
My understanding, (and personal experience), of prop-wash is…
If you try to descend too fast you end up in ‘disturbed air’, this means the props cannot ‘grip’ - this can result in wobbles at best and loss of control and rapid decent at worst - (certainly more rapid than you were hoping for)
This is why DJI quads descend @ 3m/s totally avoiding prop-wash, as opposed the ascent speed of 5m/s.
You cannae change the laws of physics Captain! - Star Trek Reference - (Sorry!)
Only way to avoid prop wash is to descend at an angle. 
(move forward and descend at the same time - full size AC have the same problem)
Invert, and the problem ceases to exist.
Just trying to get the flight controller to react quicker. Higher gyro speed means more noise, so more filtering. Which introduces latency.
Invert? Do you mean roll out of it?
I’d love to see a video of a Spark / Mavic / Phantom / Inspire inverted 
a) I’d be more surprised to see a Spark/Mavic/Phantom/Inspire categorised as a “Racing Quad, … etc.”
b) When you are in the Southampton area, happy to demonstrate a Phantom 2 “inverted”, albeit very briefly because it will be descending REALLY fast! But without any propwash issues.
@Njoro @anon34183503 and your mate dave and anyone else, Is it at all possible, on our next meet, that I could fly your inspire inverted?
Also, can we have a meet again? Itching to fly a whole day.
Can be catagorised fpv ish with the right gear. lol!
Just joking
It’s impossible to completely stop propwash. Best thing to do is fly out of it. (It’s a race drone you shouldn’t be hovering anyway) upping the gyro and pid loops doesn’t really help as your motors can only spool up or down so fast (and that’s not as fast as the pid loop or gyro).
I would have a look at bardwells 3.5.7 tuning guide and go from there. That and learn to analyse your black box logs.
Personally I have all the filters off and my pid and gyros at 4K and this works for me.
Would also be worth posting this to the bashers group as there are some very smart people there who can help you
I like that! 
I do need to fly out of it. Its just my flips / rolls land on a hover. Cheers man
If anyone can invert a DJI quad - it’s you
I’ve done plenty of flips and loops with my old P2 in full manual. Just need height before you start and getting it completed before impact!