Air filter and Jet-kit

[1ride2for-god]

I was wondering what air filter and Jet-Kit combo would give my Rancher 350 the most power boost. And are airbox vents worth while, I was thinking about tose too. Thank, God bless ya.

[firefighterjosh]

If you want more power you would need to get a pipe, air filter and jet kit. If you only do one or the other I don't think you will notice anything.

[krt400ex]

u won't notice anything with jus a filter and jet kit because the motor is already pumping just as much air as it can with the stock pipe. u will need to put at least a slip-on on with the jet kit. u will only make u motor run worse without a pipe

[GPracer2500]

Originally posted by krt400ex
u won't notice anything with jus a filter and jet kit because the motor is already pumping just as much air as it can with the stock pipe. u will need to put at least a slip-on on with the jet kit. u will only make u motor run worse without a pipe

Not true. A better filter and jetting to match the filter and the environment will help. How noticable the difference will be largely depends on how sensitive the rider is to smallish changes in torque. It might also run cooler with better throttle response. Stock jetting is often not all that good.

Getting air into and getting air out of the engine are two seperate functions. That's an oversimplified statement but for the purposes of this discussion it will suffice. When the cylinder is sucking air the exhaust valves are (basically) closed for that period. So, you can help a motor get more air into the cylinder even if you do nothing to help it get air out of the cylinder.

Exhaust mods will certainly make the most of intake mods, but it's not an all or nothing situation. Run worse with an air filter and jetting but no exhaust mods??? :ermm: Nonsense.

[krt400ex]

Originally posted by GPracer2500
Not true. A better filter and jetting to match the filter and the environment will help. How noticable the difference will be largely depends on how sensitive the rider is to smallish changes in torque. It might also run cooler with better throttle response. Stock jetting is often not all that good.

Getting air into and getting air out of the engine are two seperate functions. That's an oversimplified statement but for the purposes of this discussion it will suffice. When the cylinder is sucking air the exhaust valves are (basically) closed for that period. So, you can help a motor get more air into the cylinder even if you do nothing to help it get air out of the cylinder.

Exhaust mods will certainly make the most of intake mods, but it's not an all or nothing situation. Run worse with an air filter and jetting but no exhaust mods??? :ermm: Nonsense.

most of the time it will run worse because when u buy a filter and jet kit most people go to big on the jets. u really can only go up 1-2 sizes to see a positive change without hurting the perf. of the engine

[GPracer2500]

Originally posted by krt400ex
most of the time it will run worse because when u buy a filter and jet kit most people go to big on the jets. u really can only go up 1-2 sizes to see a positive change without hurting the perf. of the engine

Then it will run worse because it's jetted wrong not because it has an aftermarket air filter and a stock pipe. Incorrect jetting will make an engine run worse no matter what.

It's like saying: Don't rejet your bike because you'll probably do it wrong. :ermm:

[krt400ex]

that's true. but how much more power can u really get if ur pipe can't put out hardly any more air anyway. that's like trying to pump 1000 gallons of water per minute through a hose nozzle that can only handle 100 gallons a minute. it's just a waste

[GPracer2500]

Originally posted by krt400ex
that's true. but how much more power can u really get if ur pipe can't put out hardly any more air anyway. that's like trying to pump 1000 gallons of water per minute through a hose nozzle that can only handle 100 gallons a minute. it's just a waste

I stand by what I've already said.

[krt400ex]

Originally posted by GPracer2500
I stand by what I've already said.

i'm not calling u out on what u said, i'm looking for understanding. if u'd like to explain that would be greatly appreciated

[firefighterjosh]

I am going to make this simple.

If you put a jet kit and Filter you will notice very little power power diffrence.

If you put a pipe airfilter and jet kit you will notice a good amount of power diffrence.

[GPracer2500]

A stock exhaust WILL flow more air than the amount that flows when the engine is completely stock. If you run into a point where a stock exhaust system absolutely refuses to move more gas volume then that's going to happen in the upper RPM ranges. But at lower rpm it will be more than happy to move additonal gas.

Look at it this way: at 3000 rpm the exhaust is only moving 1/2 the gas volume that it's moving at 6000rpm. It's not like the exhaust is always at it's limit. So, at 3000rpm if you let more air into the engine then the exhaust has the capacity to move it. Only in the upper RPM range are you likely to run into a situation where the stock exhaust flat-out refuses to move more gas.

That's a part of the reason why just doing intake mods (with proper jetting) are likely to produce more lower RPM torque than with no mods. It's not until way up in the RPM range that the stock exhaust holds things back so much that intake mods aren't likely to help anymore.

If you add an aftermarket exhaust then you'll add exhaust flow across the board and that will make a significant difference. But like I've talked about in other threads, you don't want too much exhaust gas moving capacity because then you start hurting other features of the exhaust (namely the scavenging affect created by exhaust gas velocity).

Here's a graph of a completely stock 400EX that illustrates this. The only change is the removal of the airbox lid. No jetting changes where made. A jetting change would likely have prevented the dip in power at 45mph and the "spikeyness" of the curve in the upper RPM ranges--it was lean. Removing the airbox lid is similar (although maybe not quite as extreme) to changing to an aftermarket filter--easier cylinder filling. The point here is to notice the change in power at lower/mid RPM--the exhaust didn't have too much problem handling the extra air in that range. Add exhaust mods and you'll get all those lower rpm gains from the intake (plus more just from the exhaust) AND you'll get the flow needed for higher RPM gains.

http://www.geocities.com/gtthunder.geo/400stk2.jpg

[note: The above analysis is me speaking generally. Different exhausts, filters, airboxes, engines, etc. will do different things and may have their own quirks, but the concept is sound.]

[firefighterjosh]

Originally posted by GPracer2500
A stock exhaust WILL flow more air than the amount that flows when the engine is completely stock. If you run into a point where a stock exhaust system absolutely refuses to move more gas volume then that's going to happen in the upper RPM ranges. But at lower rpm it will be more than happy to move additonal gas.

Look at it this way: at 3000 rpm the exhaust is only moving 1/2 the gas volume that it's moving at 6000rpm. It's not like the exhaust is always at the limit of how much gas it can move. So, at 3000rpm if you let more air into the engine then the exhaust does have the capacity to move more gas. Only way up in the RPM range are you likely to run into a situation where the stock exhaust flat-out refuses to move more gas.

That's a part of the reason why just doing intake mods (with proper jetting) are likely to produce more lower RPM torque than with no mods. It's not until way up in the RPM range that the stock exhaust holds things back so much that intake mods aren't likely to help anymore.

If you add an aftermarket exhaust then you'll add exhaust flow across the board and that will make a significant difference. But like I've talked about in other threads, you don't want too much exhaust gas moving capacity because then you start hurting other features of the exhaust (namely the scavenging affect created by exhaust gas velocity).

Here's a graph of a completely stock 400EX that illustrates this. The only change is the removal of the airbox lid. No jetting changes where made. A jetting change would likely have prevented the dip in power at 45mph and the "spikeyness" of the curve in the upper RPM ranges--it was lean. Removing the airbox lid is similar (although maybe not quite as extreme) to changing to an aftermarket filter--easier cylinder filling. The point here is to notice the change in power at lower/mid RPM--the exhaust didn't have too much problem handling the extra air in that range. Add exhaust mods and you'll get all those lower rpm gains from the intake (plus more just from the exhaust) AND you'll get the flow needed for higher RPM gains.

http://www.geocities.com/gtthunder.geo/400stk2.jpg

[note: The above analysis is me speaking generally. Different exhausts, filters, airboxes, engines, etc. will do different things and may have their own quirks, but the concept is sound.]

You just said the samet hing I did except 3 pages long.

[GPracer2500]

Originally posted by firefighterjosh
You just said the samet hing I did except 3 pages long.

:confused: Hmmm. Not sure about that. I thought I was advocating the benefits of intake mods and jetting while you were saying don't bother. Anyway, my post was an EXPLINATION and I wrote it to support my earlier statements.

If what your saying is that my post was too long to be useful then that's a different matter. I do tend to go overboard sometimes in my attempts to be thorough.

[Moto250X_Rider]

i agree with GPracer on this one...i know that first hand...a motor is alot different than a hose......most stock settings are not on to the T anyway.... never hurts to put a new jet in when u run no airbox lid or vents with a good AM filter ....thats why u can buy power kits that come with a jet kit and a filter and AB vents .....what i'm getting at t better airflow will give u more power stock pipe or not

[firefighterjosh]

I am just saying, if you only do a jet kit and filter your not going to notice much. A pipe needs to be added to help breath the machine and notice any power diffrences.

[krt400ex]

Originally posted by GPracer2500
A stock exhaust WILL flow more air than the amount that flows when the engine is completely stock. If you run into a point where a stock exhaust system absolutely refuses to move more gas volume then that's going to happen in the upper RPM ranges. But at lower rpm it will be more than happy to move additonal gas.

Look at it this way: at 3000 rpm the exhaust is only moving 1/2 the gas volume that it's moving at 6000rpm. It's not like the exhaust is always at it's limit. So, at 3000rpm if you let more air into the engine then the exhaust has the capacity to move it. Only in the upper RPM range are you likely to run into a situation where the stock exhaust flat-out refuses to move more gas.

That's a part of the reason why just doing intake mods (with proper jetting) are likely to produce more lower RPM torque than with no mods. It's not until way up in the RPM range that the stock exhaust holds things back so much that intake mods aren't likely to help anymore.

If you add an aftermarket exhaust then you'll add exhaust flow across the board and that will make a significant difference. But like I've talked about in other threads, you don't want too much exhaust gas moving capacity because then you start hurting other features of the exhaust (namely the scavenging affect created by exhaust gas velocity).

Here's a graph of a completely stock 400EX that illustrates this. The only change is the removal of the airbox lid. No jetting changes where made. A jetting change would likely have prevented the dip in power at 45mph and the "spikeyness" of the curve in the upper RPM ranges--it was lean. Removing the airbox lid is similar (although maybe not quite as extreme) to changing to an aftermarket filter--easier cylinder filling. The point here is to notice the change in power at lower/mid RPM--the exhaust didn't have too much problem handling the extra air in that range. Add exhaust mods and you'll get all those lower rpm gains from the intake (plus more just from the exhaust) AND you'll get the flow needed for higher RPM gains.

http://www.geocities.com/gtthunder.geo/400stk2.jpg

[note: The above analysis is me speaking generally. Different exhausts, filters, airboxes, engines, etc. will do different things and may have their own quirks, but the concept is sound.]













thanks gpracer. i can see that u will get a slight improvement. thanks that helped.