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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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I have been tentavely watching this thread for several reasons,
  1. I too have an S4rs
  2. I have a full termi system with ECU ( bought it with )
  3. when I bought it, it came with the original airbox an had idleing issues ( which have now being recitfied ), it also had a Aftermarket reusable oiled airfilter.
I have gone out and bought myself a second hand airbox cover to modify. Unlike you guys I do ride my bike, weekly 1000kms (to and from work).
I also ride in the rain.

The airbox mod will complete my Stage one upgrade.

I too was thinking of opening up two triangular openings on either side of the air box intake at the same height of the intake with the addititon of a series of slots staying at the air intake height to reduce water intake. However reading some theories here, I see that it can be a bit of a water catcher.

Alternatively, the idea of having a series of holes down the side of the airbox cover, I am not 100% convinced, that this is the best method as the air needs to be drawn into the airbox by a negative pressure which would need to be greater than the outside pressure, I personlly like the ram force fed system which is what I am trying to generate.

Obviously tuning to this after the mod.
 

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Let us know how you go with making a ram air set-up.
I've left the S4 airbox alone as I was using it as my daily transport (500ks a week) but I've got a different job and now doing arvo shift so I can afford to drive the ute and keep the ks down on the S4.
It already has metal termis and a 996R ecu and a reusable panel filter
I thought about the foggarty style rams but have never seen pics to know if they can be made functionable or are just expensive decorations.
 

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I have two S4RS, a 2008 Tricolore, and a pearl white/red stripe 2007.

The Tricolore has 50mm Arrow race pipes, SC Project Muffler: OVAL R60 / CARBON FIBRE / D07-07C, no cat, and opened up airbox. On a Procycle dyno it showed 132 hp, and ran much better throughout the rev range than before. On the freeway, sitting on 110 to 138 kph it gets 18.3 kpl. This tune was done with a reflashed ECU and Tune-ECU. I'm fairly certain this is a better result than a generic tune. It is certainly much better to ride than just the DP ECU.

The 2007 has a 45mm exhaust of unknown provenance and SC Project GP M2 muffler, no cat, and the air cleaner lid has a couple of extra circular holes on each side, but not as big as the open airbox on the Tricolore. It has a Tuneboy reflash and a Procycle dyno tune done by the same operator that tuned the Tricolore. It showed 120.71 hp on the dyno. It too does 18.3 kpl on the freeway. The readout for that one shows before and after figures.

To me, this just shows how different "same" engines can be. I asked the dyno guy why the difference and he put it down to the airbox not being as open. Maybe.



 

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Interesting. Someone did a good job on the Tricolore for sure. Keeping the AFR in that sweet spot around 12.5 to 13 is a major factor. And they kept it tight. Too bad we can't see those numbers for the 07. Judging by the torque curve before and after, I wonder how it's sitting as far as cam timing.
 

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i have been caught in the rain too many times to count
never had any issues
my top box is cut so that i kept the sides and removed only the flat top.
dremel ate through it in minutes
 
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