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Discussion Starter #1
I would like to get some cooler air to my airbox. I'm not looking for a performance boost, just looking to lower the temperature of the air going into my engine. Cold air is more dense and thus will combust more efficiently and cleanly. There are multiple threads where people who know what they are talking about discuss CAI and ram air and how neither really affect performance, and I recognize this. From my reading it is clear that the best air intake solution for a largely unmodified street only bike is the stock airbox, so I'm just trying to maximize its efficiency.

The stock location that the airbox intake terminates is less than ideal, whether at a stop or moving. I measured the air temperature at the intakes and, even at 45mph, the air was 25°F (minimum) hotter than the ambient air once the engine had reached standard operating temperature.

... all that being said, does anyone have any plans/sources/pictures of an effective way to get cooler air to the airbox for a 98-99 CBR900RR? I'm willing to spend the money for a quality solution, and I'm also willing to fabricate one if need be. I'm not looking to jury-rig my bike, thus I am staying away (for the time being) from the "dryer hose method." I want to keep all my fairings on.

 

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I would like to get some cooler air to my airbox. I'm not looking for a performance boost, just looking to lower the temperature of the air going into my engine. Cold air is more dense and thus will combust more efficiently and cleanly. There are multiple threads where people who know what they are talking about discuss CAI and ram air and how neither really affect performance, and I recognize this. From my reading it is clear that the best air intake solution for a largely unmodified street only bike is the stock airbox, so I'm just trying to maximize its efficiency.

The stock location that the airbox intake terminates is less than ideal, whether at a stop or moving. I measured the air temperature at the intakes and, even at 45mph, the air was 25°F (minimum) hotter than the ambient air once the engine had reached standard operating temperature.

... all that being said, does anyone have any plans/sources/pictures of an effective way to get cooler air to the airbox for a 98-99 CBR900RR? I'm willing to spend the money for a quality solution, and I'm also willing to fabricate one if need be. I'm not looking to jury-rig my bike, thus I am staying away (for the time being) from the "dryer hose method." I want to keep all my fairings on.



You can insulate around the carbs, airbox and tank - but I think it'd be a wasted effort. 25F is nothing, you'd see that sort of difference just in riding between morning and afternoon most days and how much difference does that make to your engine performance? How much different is the air density over 25F anyway?
Cars are a whole different situation with the air intake tracts entirely contained within a very hot engine bay, bikes don't have that to deal with.
 

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Discussion Starter #3
You can insulate around the carbs, airbox and tank - but I think it'd be a wasted effort. 25F is nothing, you'd see that sort of difference just in riding between morning and afternoon most days and how much difference does that make to your engine performance? How much different is the air density over 25F anyway?
Cars are a whole different situation with the air intake tracts entirely contained within a very hot engine bay, bikes don't have that to deal with.
As a reminder, I said 25F *minimum* -- often the difference was 45F or more. Either way, the density of air changes about 10% at the average difference I recorded and given the fact that I'm already dealing with humidity in my area which further lowers the air density I would really like that extra little bit. It may be a trivial thing, but I am still interested if for nothing more than the fun of tinkering. Plus, I use my bike to commute and often when I am sitting in traffic the engine temp is in the 220 range and I am interested in seeing if a fresh air source would keep the temp down a few degrees. Like I said above, I'm not expecting unrealistic gains or an extra 10 horses, so soap boxes are not necessary. Has anybody used one of those air induction cowls that attach to the tank? I've seen a couple on street fighter style cbr900s and I wonder how effective they are. At close to $200, that's not exactly a "I'll just slap one on and try" kind of thing!
 

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As a reminder, I said 25F *minimum* -- often the difference was 45F or more. Either way, the density of air changes about 10% at the average difference I recorded and given the fact that I'm already dealing with humidity in my area which further lowers the air density I would really like that extra little bit. It may be a trivial thing, but I am still interested if for nothing more than the fun of tinkering. Plus, I use my bike to commute and often when I am sitting in traffic the engine temp is in the 220 range and I am interested in seeing if a fresh air source would keep the temp down a few degrees. Like I said above, I'm not expecting unrealistic gains or an extra 10 horses, so soap boxes are not necessary. Has anybody used one of those air induction cowls that attach to the tank? I've seen a couple on street fighter style cbr900s and I wonder how effective they are. At close to $200, that's not exactly a "I'll just slap one on and try" kind of thing!

If air density changes 10% over 30-odd degrees wouldn't that cause breathing problems between morning, midday and evening? It would certainly cause jetting problems. I don't think even ram air systems generate 10% increase in density?
The 220F region is normal in slow traffic in summer.
I don't think reducing intake air temp is going to have any measureable effect on the huge combustion temperatures - and that's what causes the coolant temps.
If you do mess with it I'd certainly be interested to see if you find any measureable difference in performance though.
 

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Hi
The idea occured to me many years ago. I looked at picking up a 'cooler' air supply from the nose area. I did use the 'hose' method but these were hidden under the fairing trim plastics. Looked neat and I was sure it would be of some benifit on the hotter days. Unfortunately.... Any turbulance on the airbox intakes seems to really unsettle carburation, mine started to bog and missfire at any speed above 80 - 90 MPH. There was obviously an element of 'ram air' going on so, if you are proceeding, take care to completey smooth any airflow.
 

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Hi
The idea occured to me many years ago. I looked at picking up a 'cooler' air supply from the nose area. I did use the 'hose' method but these were hidden under the fairing trim plastics. Looked neat and I was sure it would be of some benifit on the hotter days. Unfortunately.... Any turbulance on the airbox intakes seems to really unsettle carburation, mine started to bog and missfire at any speed above 80 - 90 MPH. There was obviously an element of 'ram air' going on so, if you are proceeding, take care to completey smooth any airflow.

John Robinson's "Motorcycle Tuning: Chassis" Chapter Seven has good information about getting smooth air flow in the intake system, particularly regarding position, shape and flow volume and pressure.
Amazon.com: Motorcyle Tuning: Chassis, 2nd Edition (9780750618403): John Robinson: Books

The series includes two other books about engine development, Four-Stroke and Two-Stroke.
 

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Discussion Starter #7
About the ram air thing... I'm definitely going to make sure that I don't grab air from the nose because of what I read about the stock airbox not being meant to handle that type of intake...

Blade, air density is a pretty basic concept and I'm sure you could find tables that detail air density changes over temperature ranges. The short answer to your breathing question is no. You know better than I do that there are tolerance levels either way for any engine setup but my point is that pulling cooler air rather than significantly hotter air if done correctly can't have anything but a positive effect.
 

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Blade, air density is a pretty basic concept and I'm sure you could find tables that detail air density changes over temperature ranges. The short answer to your breathing question is no. You know better than I do that there are tolerance levels either way for any engine setup but my point is that pulling cooler air rather than significantly hotter air if done correctly can't have anything but a positive effect.


I did look into it actually :)
From what I can gather, roughly 28C gives 10% change in air density - which is maybe something like 55F? As I said, roughly the change in ambient temps you'd see during a day, and I've rarely noticed a significant difference in engine performance within that range. When I have noticed a difference it would be more due to the moisture content of the air I think, rather than the temperature.
I think theoretically, that should push 10% more air into the engine and raise the dynamic compression ratio by one-tenth, which I doubt would be measureable on a dyno.
I agree, cooler air is better every time, although probably not if it reduces aerodynamics or causes fueling problems.
I didn't say you shouldn't try it, merely that I don't believe there's any measureable gain from doing so. I say go for it, and let us know how you get on. I do all sorts of experiments myself to try out my own ideas :)
 

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Discussion Starter #9
I did look into it actually :)
From what I can gather, roughly 28C gives 10% change in air density - which is maybe something like 55F? As I said, roughly the change in ambient temps you'd see during a day, and I've rarely noticed a significant difference in engine performance within that range. When I have noticed a difference it would be more due to the moisture content of the air I think, rather than the temperature.
I think theoretically, that should push 10% more air into the engine and raise the dynamic compression ratio by one-tenth, which I doubt would be measureable on a dyno.
I agree, cooler air is better every time, although probably not if it reduces aerodynamics or causes fueling problems.
I didn't say you shouldn't try it, merely that I don't believe there's any measureable gain from doing so. I say go for it, and let us know how you get on. I do all sorts of experiments myself to try out my own ideas :)
where do you live that the ambient temperature changes 55F in a day??? thats like from 35F to 90F! Where I live, the temperature *MAY* vary by 15F-20F on a wild day... but generally by the time I'm riding, the temperature doesn't change THAT much...
 

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where do you live that the ambient temperature changes 55F in a day??? thats like from 35F to 90F! Where I live, the temperature *MAY* vary by 15F-20F on a wild day... but generally by the time I'm riding, the temperature doesn't change THAT much...


Western Australia :)
Yesterday the temp went from 8.8C to 24.8C, Friday was 12.1C to 22.9C. Last Saturday we had 3.1C to 18.2C - damn that was cold!
Summer has greater varience of course. January 2nd we had 18.7C up to 40.3C and January 26th was 11.3C to 30.8C.
I think there are places in the middle east that see more than 100F change in a day.
 

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Hi all
Whilst air temp must have 'some' effect on cylinder charging, have you considered this:-
(Bit of a ramble). I've just been working on a GPZ (ER) 500, sorted out a lethally siezed suspension unit, thought all was well and sent the lad on his way. He came back on Thursday. Engine started fine, ticked over etc. After a few minutes it started bogging and missing. Long story of checking carbs, filters, fuel supply, later, it turned out that the engine breather was pumping excessive blow by into the air box. (Rings siezed, maybe do a seperate thread as I need your opinion bladeracer).
I wonder by how much the mixture purity is affected by the recycled crankcase gas that emmisions laws legislate. Maybe routing the breathers to atmosphere would give a better return?
 

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If you want to go blue sky thinking.... What would be the benifits of fitting a small refrigeration unit and super cooling the petrol? They do this on GP racers (or rather, the fuel is refrigerated and put into the tank just before the race starts). A small efficient unit sufficient to cool the petrol feed line into the carbs was my thought........
 

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Discussion Starter #15
So many ideas!!! I spent less than $2500 on the bike so fitting a refrigeration unit or a nitrous system (while both are "cool" options, pun intended) is going to be more than I want to put into the bike! That is, unless you know of a cheap way to do either...

Blade - that is CRAZY! Australia is one place I haven't gotten to... I think next time my wife and I go on holiday we are going to try to get across the ocean that way. Anyways, I see where you are coming from now... but I live in Virginia, USA, so the temp changes aren't that extreme.

Jdugen - I routed mine to atmosphere and I just reconnect them correctly when it is time for a bi-yearly inspection.

Lambchops - I made it. 2 plastic nuts/bolts, 2 small stainless steel strips 2.5cm(w)x5cm(l) with holes drilled in either side, 2 small metal nuts/bolts. I drilled the metal nuts/bolts into the undertail with the metal strips attached. I mounted the license plate to the metal strips with the plastic nuts/bolts.

I'm still working on this... I found some exhaust flex pipe that looks nice and I'm thinking about heat wrapping it and routing it to the large spaces in the fairings (not right into the wind to avoid the ram air effect) and then putting some mesh there to make it look clean.
 

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I remember seing a website thar takes 900rr and has the cold air intake 'n a kit
It takes the radiator and lowers it one inch comes with all tje neseaary parts I belive it was usef on the N haden bikes I want to say irs AirTech.com hope that helps
 
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