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Airbox for zx9r C1
Cornishman - 22/1/12 at 07:41 PM

Hi all

Have just started getting together parts for a zx9 r conversion to replace the 1.3 xflow currently fitted in the hillclimb Locost.
The guy on here I bought the engine from (roadrunner) has been very helpfull and given lots of advice on installation etc (thanks brad).
He has been using the standard airbox slightly modified and it worked fine.
Because I am not using it on the road so no IVA to worry about I have been thinking about pros and cons of fitting a sausage type filter and maybe re jetting for some increased power?
Some research on the net has found several "biker" sites that seem to suggest that the standard airbox is hard to beat and that problems can result from removing it and fitting a performance filter, presumably "leaning out" at higher RPM's.
The original bike has a ram air system as far as I can see, which apparently does not generate much in the way of positive pressure but does supply a healthy supply of cold air dependant on forward speed.
On another thread I see that the car Andy Bates has pointed out (Fisher Fury Fireblade) has an airbox fitted and what appears to be an air intake duct fitted at the front of the car?

I'd be grateful for any opinions for and against the idea of replacing the airbox/rejetting or maybe fitting a cold air duct to the existing arrangement.

Thanks

Steve

roadrunner - 22/1/12 at 08:11 PM

Hi Steve.
You could always make your own air box with a cold air feed.
Brad.

40inches - 23/1/12 at 09:35 AM

I kept it as close to the bikes as I could, got a good chance that it will run OK from the off.


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ceebmoj - 23/1/12 at 12:27 PM

quote:
Originally posted by 40inches
I kept it as close to the bikes as I could, got a good chance that it will run OK from the off.

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Looks great is the duct from any where or did you make it up?

ChrisL - 23/1/12 at 12:43 PM

Fantastic piece of work there 40inches, do you do orders? ;-)

[Edited on 23/1/12 by ChrisL]

[Edited on 23/1/12 by ChrisL]

ChrisL - 23/1/12 at 12:51 PM

Actually just looking at your other pic's looks like it's a close call on getting negative pressure, sucking rather than blowing. Due to the chimney effect...

40inches - 23/1/12 at 03:21 PM

quote:
Originally posted by ceebmoj
quote:
Originally posted by 40inches
I kept it as close to the bikes as I could, got a good chance that it will run OK from the off.

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Looks great is the duct from any where or did you make it up?


My first attempt at GRP, I used the wrong sort of paint on the plug and the heat from the curing process bonded the whole
lot together I had to destroy the plug to separate them.

40inches - 23/1/12 at 03:45 PM

quote:
Originally posted by ChrisL
Actually just looking at your other pic's looks like it's a close call on getting negative pressure, sucking rather than blowing. Due to the chimney effect...


Did think about that, although I'm not that bothered about positive pressure, some tests on the net showed that the ram air has no effect until well over 100mph is reached. On the other hand I do not want negative pressure, hopefully the engine will pull in enough air to overcome any slight negative pressure.
Once on the road the old woolen streamer test may show any problems (hopefully).
Some discussion HERE

Bluemoon - 23/1/12 at 05:04 PM

quote:
Originally posted by 40inches
quote:
Originally posted by ChrisL
Actually just looking at your other pic's looks like it's a close call on getting negative pressure, sucking rather than blowing. Due to the chimney effect...


Did think about that, although I'm not that bothered about positive pressure, some tests on the net showed that the ram air has no effect until well over 100mph is reached. On the other hand I do not want negative pressure, hopefully the engine will pull in enough air to overcome any slight negative pressure.
Once on the road the old woolen streamer test may show any problems (hopefully).
Some discussion HERE


Might not look as nice as your ducts but it is possible to calculate airflow ect if you use an NACA duct sized for the engine : http://en.wikipedia.org/wiki/NACA_duct

ginger ninja - 23/1/12 at 05:53 PM

We have a ZX9 in a locost for track work too. It has a sponge Pipercross sausage through the hood. Dynojet kit fitted and with decent exhaust made 147 BHP on rolling road.
Not sure air starvation is an issue, on track it delivers power consistently throughout the rev range - starvation would manifest istelf during peak revs.

The main benefit to fitting an airbox is noise, quite a few circuits have stringent noise limits. Without an airbox, you may pass a static test, but are likely to fail trackside testing ( unless you ease off the gas when passing fixed sites). An airbox also protects the filter from direct rain, but may still draw some moisture into the box subject to the inlet arrangement.
Not sure about hill climbing - maybe noise isn't a problem, in which case I'd go with the sausage, the induction roar is intoxicating and it's less faffing to install and quick to remove during tinkering/allows better access.

Whichever route you decide, keep the original carb velocity stacks (inlet trumpets) and ensure there is sufficient clearance between them and the filter material ( info online gives ratio of diammeter to min. distance needed), generally a couple of inches.

happy fiddling !!

Cornishman - 24/1/12 at 07:50 PM

thanks to all for the advice