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Discussion Starter #1
I know this is an old model, so therefore this is old news. I just wanted to point out to those of you who have an S4RS that the air box lid design is extremely restrictive. The opening area into the air box is much smaller than the area of the injectors. I don't recommend running no lid at all , especially in wet or dusty conditions, because of the location of the air box in relation to the fuel tank. If you have not modified your air box lid, though, you need to . I opened up the front of mine on either side of the factory hole. This wouldn't be the best place if you ride in the rain. Holes down the sides might be a better alternative for a daily driver, but they need to be substantial to eliminate restriction from the lid. The air box volume itself is also too small, but there's no room for a properly sized one. An aftermarket low restriction filter is about all you can do to help, but you need to do both. Another reason to go aftermarket on the element is that the stock paper filter will not handle any moisture without becoming more restrictive.
 

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I know this is an old model, so therefore this is old news. I just wanted to point out to those of you who have an S4RS that the air box lid design is extremely restrictive. The opening area into the air box is much smaller than the area of the injectors. I don't recommend running no lid at all , especially in wet or dusty conditions, because of the location of the air box in relation to the fuel tank. If you have not modified your air box lid, though, you need to . I opened up the front of mine on either side of the factory hole. This wouldn't be the best place if you ride in the rain. Holes down the sides might be a better alternative for a daily driver, but they need to be substantial to eliminate restriction from the lid. The air box volume itself is also too small, but there's no room for a properly sized one. An aftermarket low restriction filter is about all you can do to help, but you need to do both. Another reason to go aftermarket on the element is that the stock paper filter will not handle any moisture without becoming more restrictive.
What was the difference after the mods you made? Was it measured on a dyno or SOTP?
Was it a series of small holes or one large?
 

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Discussion Starter #3
Actually not tried yet but Sotp tomorrow . I have no dyno access at the moment. The ratio of the stock air box intake opening area to the injector diameter area was so out of wack it was an obvious restriction. My bike has a shorty Termi and whatever was done to the engine management system to allow that to run well, with stock air box and filter element. Hopefully this change is within the systems ability to compensate for the extra air flow and doesn't cause a lean condition , but I won't be surprised at all if it's too lean to run well. I'm not changing the element for something less restrictive until I've ridden the bike . The other half of the equation is that the total air box volume is also too small and not much can be done, except conversion to pods. I'm not ready to go that far yet.
 

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Discussion Starter #4
Sorry, you asked about hole size ? I opened a large hole in the front on each side of the stock intake "funnel ". The holes aren't round but rather follow the contour of the top. Each is larger than the original intake area and will draw air from under the front of the fuel tank. In retrospect, after seeing the finished lid, it would have made more sense to put smaller holes down the side of the lid for rainy conditions. I don't ride this bike in the rain.
 

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Discussion Starter #5
Definitely more intake noise, but as loud as the short Termi is, that's no big deal. It feels faster, it sounds faster, does that count ?
 

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Discussion Starter #7
I bought a BMC replacement filter as my air box mods could allow more moisture to reach the stock paper element which usually leads to reduced flow. The new element barely fit, and I mean barely. The rubber seal around the edge is fatter, which may be a good thing, as some dirt was getting by the stock element seal. It has fewer but much deeper pleats than the stocker and appears similar to a K&N in construction , with cotton gauze media. Made in Italy, how could I go wrong ?
 

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If anyone needs an untouched oem filter top to cut up and experiment, lmk, I think I paid maybe $30. Oh, it is from a 916 S4, so not sure if identical to 996/998 needs.
 

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I use pod filters and like them a lot. Significant weight reduction. Nice sound (that counts big time in my book). No idea whether they add HP since I didn't do everything piece by piece - but I imagine that the pod, arrow exhaust, higher voltage coils, better ignition wires, bigger engine, and Rexxer remap all work together as a system better.
 

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I use pod filters and like them a lot. Significant weight reduction. Nice sound (that counts big time in my book). No idea whether they add HP since I didn't do everything piece by piece - but I imagine that the pod, arrow exhaust, higher voltage coils, better ignition wires, bigger engine, and Rexxer remap all work together as a system better.

Can you tell more about the Rexxer remap?

My stock S4RS seems to want to cough and stall sometimes when taking off. Like its too lean.
Would the remap cure that?
 

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It might fix that, but there could be any number of other reasons. If the bike is pretty much stock, then I doubt it needs to be remapped. What mods have you made?
 

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Discussion Starter #13
Mine also did that occasionally when I first bought it, but hasn't lately. Usually happened when not fully warmed up and I was attempting to be too delicate with the throttle, like when making a sharp right turn into traffic from a driveway. I cleaned my throttle body venturis and add some Seafoam to the fuel regularly . I think I changed my technique and give a little more throttle while slipping the clutch a bit more in those circumstances now.
 

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I have the Houston Superbikes Carbon fiber open air box lid. The DP/Termignoni kit is basically the stock a box with the the top cut off, whereas mine is actually a full carbon replacement that was designed to be open from the start. Coupled with a Pipercross filter, the induction sound is literally deafening at WOT in a tucked position. With a full face helmet, the induction resonance still hurts your ears.

Drilling holes in the stock air box is fine, but I have never had an issue use of riding in the rain without the airbox top. I wouldn’t wash it while it’s running lol, but otherwise no rain/water issues.
 
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