Air Filters: Is a pre-filter a good idea or not?

[AZRedhawk44]

I have a 2013 Triumph Tiger 800XC motorcycle.  It is a major pain in the rear to get to the air filter.  Six pieces of plastic, remove the tank and hold it with one hand as I clumsily disconnect several electrical connectors and fuel lines with dusty and increasingly brittle obscure mechanical plugs, then the air filter box is exposed.  Haven't broken one of these things yet, but it's a matter of time as they're approaching 10 years old.

This bike is meant to be ridden off pavement, but a shortcoming of it is how difficult it is to inspect or clean/replace the air filter.

Evidently there is an aftermarket modification for the bike that I've only just learned about.  UNI makes a "pre-filter."  It replaces the under-seat air intake snorkel before the air hits the under-tank air filter, with a dirt-bike style oiled foam filter.

https://cjdesignsllc.com/product/uni-triumph-tiger-800xc-2011-14/

The intent of the mod is to extend the service interval of the under-tank air filter, by making this under-seat "pre-filter" do the lion's share of the work.  And by being under-seat, it is far easier to access, remove, clean, and replace than the under-tank filter.

However, I question whether this would function as an air restriction and end up robbing the bike of air intake, causing it to run rich or air starved.  What does the braintrust here think?

I've been stewing on replacing this Triumph for awhile, and even have a down payment on an Aprilia Tuareg 660 as a potential replacement, waiting on one to come in at the dealer for a test ride.  Two factors that drive me to look at the Aprilia as a replacement are ease of air filter access, and the Aprilia has cruise control.  If I can resolve the air filter access problem on the Tiger, and add an aftermarket throttle lock like the Kaoko or Atlas, I can potentially stave off buying a new bike for awhile longer.  Then again, the Aprilia is about 75 pounds lighter than my Tiger and also has a lower center of gravity due to its fuel tank design, which has a lot of attraction for how much I ride on uneven terrain.

https://twistedthrottle.com/shop/ergonomics/throttle-locks/kaoko-throttle-lock-cruise-control-triumph-tiger-800-tiger-800xc-11-with-oem-flat-cylindrical-end-weight-with-barkbusters-handguards/

https://www.atlasthrottlelock.com/products/triumph-motorcycles-atlas-throttle-lock?variant=undefined

[RoadKingLarry]

I'd think a proper pre-filter on a off-road machine would probably be a decent idea, I would think it would at least extend your needed service interval by at least 30%. Maybe longer if after the first go around with the pre-filter showed an acceptable reduction in dirt getting to the primary filter.
 
I'm not even sure where the air filter is on my RT yet.
 

[bedlamite]

For filters on my Baja bug (dual Weber IDF) I have cotton K&N clones 4 1/2x7x6" oval, with Uni foam wraps over them, and outerwears over that. It's probably the worst possible configuration having one carb next to each rear tire, but It's amazing how much dirt they have kept out of my engine, I don't think I'd go off road with a single layer filter again.

[Jim147]

Looks like it would work. It doesn't say anything about wash and oil when dirty so if you get it let us know.

[Hawkmoon]

The intent of the mod is to extend the service interval of the under-tank air filter, by making this under-seat "pre-filter" do the lion's share of the work.  And by being under-seat, it is far easier to access, remove, clean, and replace than the under-tank filter.

However, I question whether this would function as an air restriction and end up robbing the bike of air intake, causing it to run rich or air starved.  What does the braintrust here think?

Is the engine fuel injected and computer-controlled? If so, it can't run rich -- the ECU will reduce the injector pulse time to compensate.

[AZRedhawk44]

Is the engine fuel injected and computer-controlled? If so, it can't run rich -- the ECU will reduce the injector pulse time to compensate.

You know, I'd think so too, except for this:

https://www.youtube.com/watch?v=ZRNfyz1Cgvg

It seems that while automotive fuel injection actually does a little math and sensing, motorcycle fuel injection is more of a hackjob and an X/Y plot fuel map.  Do something out of range and it'll throw fits.

I've seen one report of the Aprilia Tuareg I'm interested in, where the rider took it to the Dead Sea area in the Middle East, about 1000 feet below sea level.  It ran rough and threw a check engine light.  Evidently Aprilia didn't bother to give the map sufficient range to support such high barometric pressure from being below sea level.

[tokugawa]

Is there a dyno nearby? A pre and post run would tell you what the additional filter is doing to the fuel air mix.

[Brad Johnson]

It seems that while automotive fuel injection actually does a little math and sensing, motorcycle fuel injection is more of a hackjob and an X/Y plot fuel map.  Do something out of range and it'll throw fits.

This.

From what I can tell, most MC injection systems are MAP, not MAF. They run fixed fueling tables which key off manifold pressure and throttle position. Throw in a coolant temp sensor if water-cooled. MAP systems are notoriously intolerant of changes in air and exhaust flow.

Brad