Outer Limits 4x4 Board

I want a Donaldson TopSpin for the snorkel before I go bush at the end of next week. There are two models in the range which will fit the top of the snorkel, one rated 90-200 cfm, the other 200-450 cfm.

A few quick calcs suggested a 3 litre engine at 3000 rpm is (nominally) pumping around 160cfm (in reality, less - how much less?) So, given that I'll generally be at lower revs than that when dust is most likely to be a problem, I believe the small unit is the one that I want. Unless I'm missing something?

I googled for some help, and mainly found comments that they don't work properly above 80km/h. I'm guessing that's more likely to be caused by a small pre-filter on a large engine?

Anybody have experiences to share?

Cant comment too much on your CFM, but we checked out their effectiveness at speed where people say that they become ineffective.... and they were most effective at extracting dust.

I have one installed will let you know which one when i get home.

I have the H002437 on my freshly rebuilt 2.8L Turbo Diesel (3L motor).
I put it on when i got the motor rebuilt; have tryed it with a normal snorkel head to compare fuel use, power and dust accumulation on the filter.
The fuel use didn't really change nor did the power but holy crap the amount of particles that it keeps out is awesome. I went to fraser for a week and the inside of the filter housing you would expect to see some sand/salt particles (on the outside of the normal filter) NOPE!! non there and it was using a paper normal filter so it is not as if it was a K&N letting stuff through. I wasn't being too careful either that trip included some salt water crossings going around the rocky points instead of through the cuttings
They don't look the best but for looking after your engine they are tops IMHO