how much hp is really gained from taking air box lid and snorkel off?

[anabolicsman]

i bought my quad off somebody with snorkel and airbox lid off and i just recently took it to a place to get something worked on and they recomend that i put it back on and the said there really aint much of power increase is that true? i ride trails with dusty dirt

[Scro]

As long as the bike is jetted to supply more gas, then there should be quite a bit of difference...especially if you have exhaust. If it isn't jetted correctly, it will probably hurt the power because you will be running lean. You also have to keep an eye on the air filter, as it will get dirtier easier.

[gcart2]

do what i do. use foam filters. get 2. put one in your bike an d keep the other along with filter oil with u so when 1 gets dirty switch it around.

[GPracer2500]

I'd guess re-jetting would remove that dip at 45mph that pushes the the green line below the blue line between ~45-55mph.

http://www.geocities.com/gtthunder.geo/400stk2.jpg
[test courtesy of GT Thunder (http://www.gtthunder.com/)]

Thats awesome to see a graph on it. So it shows gains when under 45MPH just taking off the airbox lid and not even jetting it. It would be good for tight twisty trails but then when you open it up it suddenly bogs down. Jetting would most likely remove that dip at 45MPH and brong the power up above the stock line. Removing the snorkel can cause problems. With my brother 400ex on a rebuild his friends said its fine to just leave it off. Well it rammed so much air into the air box it choked out the engine. Open airbox lid is fine but I wouldnt remove the snorkel. Someone once said "think of removing your snorkel and having that much air rush past your filter, well is it easy to breathe sticking your head out of the window doing 60MPH in your car?" I'm not sure the same principals apply with a motor but I'm convinced after my brothers running like crap just by removing the snorkel.

[oleboy87]

i run the air box lid off but only b/c the way it was jetted when i got it.. its going to be rejetted soon to run the lid on it... its a pain in the a** when riding in trails... and i have a k&n filter soo its even worse... its all jsut comes down to how its jetted

[CarGuy7a]

i noticed quite a bit of difference when i put my EHS racing lid on. of course i had it jetted a bit rich so it ran perfect with the racing lid on. i did have to change the pilot jet though.

as far as the snorkel i did remove mine and my dad made me a snorkel plug out of plastic on a lathe.

i also added something to my K&N filter to keep it from packing up with dust. check out the thread titled K&N users please look. it's a good way to make use of your stock filter you have laying around doing nothing.

Originally posted by CarGuy7a
i noticed quite a bit of difference when i put my EHS racing lid on. of course i had it jetted a bit rich so it ran perfect with the racing lid on. i did have to change the pilot jet though.

as far as the snorkel i did remove mine and my dad made me a snorkel plug out of plastic on a lathe.

i also added something to my K&N filter to keep it from packing up with dust. check out the thread titled K&N users please look. it's a good way to make use of your stock filter you have laying around doing nothing.


aha finaly your the guy I was looking for that took the stock filter and cut the 1st layer out of it andslipped it over your K&N correct? I want to find that thread

[QuadManiac]

The dip in the curve is likely where the bike is running somewhat lean due to the additional airflow from removing the lid. Rejetting would push that line up. A pipe and rejetting will push it up even further.

My #1 400ex has a K&N, no lid, a CTR pipe and is properly rejetted. It runs all over my other 400ex which is stock except for a K&N filter, and the lid is still on. Both run perfectly throughout the entire range of gears, loads and RPM's.

RE: keeping dust off the filter - get an Outerwear filter cover.

[JOEX]

Originally posted by FoxHondaRider
Thats awesome to see a graph on it. So it shows gains when under 45MPH just taking off the airbox lid and not even jetting it. It would be good for tight twisty trails but then when you open it up it suddenly bogs down. Jetting would most likely remove that dip at 45MPH and brong the power up above the stock line. Removing the snorkel can cause problems. With my brother 400ex on a rebuild his friends said its fine to just leave it off. Well it rammed so much air into the air box it choked out the engine. Open airbox lid is fine but I wouldnt remove the snorkel. Someone once said "think of removing your snorkel and having that much air rush past your filter, well is it easy to breathe sticking your head out of the window doing 60MPH in your car?" I'm not sure the same principals apply with a motor but I'm convinced after my brothers running like crap just by removing the snorkel.
Not sure how accurate that is about removing the snorkel but most people block off the opening in the air box when they do remove it.

[Bill Fuller]

All that horsepower and all you had to do was remove the two things that protect your motor the most:rolleyes: 1 horsepower is not noticeable. You can get that gain by simply changing chains and sprockets with new ones. Not worth it IMO especially if you ride XC.

[GPracer2500]

Originally posted by Bill Fuller
All that horsepower and all you had to do was remove the two things that protect your motor the most:rolleyes: 1 horsepower is not noticeable. You can get that gain by simply changing chains and sprockets with new ones. Not worth it IMO especially if you ride XC.

Eh. I get your point and I appreciate the role of devil's advocate--but I think you're downplaying the benefit and exaggerating the risk. IMO, of course.

1) The airbox lid protects the engine the most? Come on. Depending on your riding conditions, it may or may not be important to have. Consider the TRX450R HRC kit includes running a mostly open airbox lid (04/05) or running no airbox lid at all (06+). Airboxes with full enclosures do provide extra protection for the air filter from debris, but the filter itself is what's actually providing the protection. If you're riding in deep water, that's a different matter.

And what's the second thing you mentioned? Are you talking about the snorkel? If the airbox lid is removed then removing the snorkel is mostly moot. Plugging the snorkel entry hole in the bottom front of the airbox might be the only consideration.


2) What do you mean "1 horsepower"? That dyno test shows as much as ~4hp gain over a pretty wide range. Most of us won't have a problem feeling that difference.

[CarGuy7a]

Originally posted by FoxHondaRider
aha finaly your the guy I was looking for that took the stock filter and cut the 1st layer out of it andslipped it over your K&N correct? I want to find that thread

yeah the thread is called
K&N users please look.

you may have to drop the K&N part for doing the search b/c i think it has a 4 letter word minimum thing.

also the filter oils i use are Klotz Fabric filter oil for the K&N and
Klotz Foam filter oil for the foam filter element.

[QuadManiac]

Originally posted by Bill Fuller
All that horsepower and all you had to do was remove the two things that protect your motor the most:rolleyes: 1 horsepower is not noticeable. You can get that gain by simply changing chains and sprockets with new ones. Not worth it IMO especially if you ride XC.

Yeah, I forget that all riding is not like mine - warm and dry. I don't need the cover and especially the snorkel, I always ride desert. An Outerwear, and I'm happy. If you ever get wet, I assume it's a lot smarter taking a very small power hit and leaving your protection in place.