L air box "lid" side panel - Why is it that ....


6 replies to this topic
  • Huffa 2

Posted June 16, 2007 - 07:00 AM

#1

........on the R the hot set up is to open up the panel/lid with kits, drilling holes and such but it is uncalled for on the L.

:thumbsup: Seems to me you could make the L breath even better that way then just removing the snorkel and possibly improve performance even more by raising the needle or going up on the main another size or so, since you have even more air flow now?

The way the panel bulges out it would get quite a healthy blast of air that way!

I can't recall seeing anyone do it on here, am I missing something ?

There is plenty of room to do it.

  • Phuzzy McPhuzzface

Posted June 16, 2007 - 09:09 PM

#2

........on the R the hot set up is to open up the panel/lid with kits, drilling holes and such but it is uncalled for on the L.

:thumbsup: Seems to me you could make the L breath even better that way then just removing the snorkel and possibly improve performance even more by raising the needle or going up on the main another size or so, since you have even more air flow now?

The way the panel bulges out it would get quite a healthy blast of air that way!

I can't recall seeing anyone do it on here, am I missing something ?

There is plenty of room to do it.


How big (measured in area) is your carb's throat?

How much open area do you have on the L's airbox now, if you removed the snorkel?

Once you have more area open on the airbox that you have area of carb throat, you won't gain any more airflow. You might gain more mud in the airbox, though. :thumbsup:

  • Jack Roberge

Posted June 17, 2007 - 10:01 AM

#3

I tried running my bike with the side panel off. It seemed as if there was a little more power. The problem was the intake noise was very loud. So loud it almost drowned out my exhaust noise. To much noise for the small HP gain IMO.

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  • Huffa 2

Posted June 17, 2007 - 10:06 AM

#4

I tried running my bike with the side panel off. It seemed as if there was a little more power. The problem was the intake noise was very loud. So loud it almost drowned out my exhaust noise. To much noise for the small HP gain IMO.


.......but you don't know if that made it run lean or not and you possibly could have much bigger gain by rejetting??

I can imagine how loud that made it though.

So from a stock point of view the XR R (not L) air box must be more restrictive then ?

  • FZ1426

Posted June 17, 2007 - 07:38 PM

#5

How big (measured in area) is your carb's throat?

How much open area do you have on the L's airbox now, if you removed the snorkel?

Once you have more area open on the airbox that you have area of carb throat, you won't gain any more airflow. You might gain more mud in the airbox, though. :thumbsup:


Not really. There's more to the effects of airbox/air filter shape, volume, and flow than just having a hole as big as the carb throat. I'm not going to profess to be a research scientist on the matter but I have done a lot of experimenting with it. There are a lot of niuances to power and throttle response to be gained through the airbox beyond simple "airflow", or even what a dyno can show.

I just opened up the side panel on my 600R based on the great results I had with my 650R (including the "batwing" vane). With proper jetting and pipe tuning it provided a crisper and more satisfying low end punch.

  • Phuzzy McPhuzzface

Posted June 18, 2007 - 06:56 AM

#6

Not really. There's more to the effects of airbox/air filter shape, volume, and flow than just having a hole as big as the carb throat. I'm not going to profess to be a research scientist on the matter but I have done a lot of experimenting with it. There are a lot of niuances to power and throttle response to be gained through the airbox beyond simple "airflow", or even what a dyno can show.

I just opened up the side panel on my 600R based on the great results I had with my 650R (including the "batwing" vane). With proper jetting and pipe tuning it provided a crisper and more satisfying low end punch.


Very true, and one of the biggest factors is resonance which is achieved by tuning the airbox cavity to match the intake pulses over the RPM range. In a nutshell, this pressurizes the air in the airbox for the ram-air effect---denser air enters the engine which yields a performance boost.

Since many people think along the lines of "more open is better---drill the bejeezus out of the airbox", this tuned effect get stripped away. Once you are drilling holes in your airbox in a "looks good to me" fashion, then more open area on the airbox vs the carb throat is a moot issue.

Intake restriction is mostly a bottleneck issue, and if you have 1.5 times the carb throat area already opened up on the airbox, 2x, 3x, 20x won't yield any performance gains, and will most likely reduce performance do to de-tuning the resonance of the system.

I'd like to see a scientific dyno experiment on this, and be able to determine where any gains are realized. Once you are past a certain point (simple re-jet, tip removal, and snorkle removal or Dave's mods) I bet any detectable gains are where you'd never run your bike anyway such as close to redline @ WOT. I bet that normal-range useability/driveability would also suffer to some degree as well. To me, that's a negative trade-off, especially on a low-rev, high torque engine.

  • XR650L_Dave

Posted June 18, 2007 - 07:43 AM

#7

The XRL may be a bit of a special case, as its extremely hard for air to get above the airbox.

I modified my seat slightly to get more air above the airbox, and it did help a little.

I think some moderate side-panel relieveing could help breathing a bit. No huge gains to be had, though.

Dave





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