I have adapted my orginal airbox of my gpz1000rx as per pic shows

http://s439.photobucket.com/albums/qq117/locosaki/?action=view&current=Airbox002.jpg


Now after reading quite a few posts on the subject I think now this could be restritive !!

I'm toying with the idea of making my own box to suit.The orginal airbox connects to the carbs via rubbers,these rubbers continue into the airbox and form trumpets,I assume I would be better keeping this and making my box around these trumpets ??

When I bought this car it had 4 individual filers on the carbs with no trumpets at all,What effect would running without trumpets have on the engine ??

[Edited on 29/1/09 by locosaki]

[Edited on 2/2/09 by locosaki]

I went through the same fun you are toying with. The trumpets make a considerable differnce to the airflow into the engine. When my engine ran without one on one of the inlets, you could hear the difference on that one cylinder.

When I made my airbox, I bought new trumpets, and built my airbox from there. I used the old airbox as a template for the spacing, then cut that, and designed the rest from there....

link doesn't work for me

The trumpets smooth the airflow at high air speeds. This means that more air flows in a high speeds. At high RPM, your engine would be starved of air without them. You would need to rejet your carbs with smaller mains to run properly. Overall result = less top end power.

Remember, you need at least 1.5 x the diameter of the carb's worth of clear space in front of the trumpet. If the wall of your airbox is in the way, it will restrict the air flow.

I found that the inlet to the air box needs to be 3x the area of one carb throat to avoid restriction.

You could fit shorter trumpets if you had some turned up for you. I did. The effect of this is to move the peak torque further up the RPM band, but probably not by much.

Thanks for the reply guys,

The carbs I'm running are 36mm so I can easily acheive 1.5x distance required,I actually have a lot of room to play with as my carbs are side draught,The airbox in the link has been adapted "crudely" but it was just to get the idea,I have used a 4" inlet on this but I assume the box is too small !! ( I have read a lot of the previous posts now)

If I jet the mains down and I'm losing power does it make sense to spend time on fabricating an airbox if it's slowing the car down !! Or am I missing something here !!

Don't neglect the noise implications of using a modified airbox or none at all, especially if you intend doing trackdays.
Despite the fact that it will stick up through the middle of the bonnet we are going to use the factory standard airbox on our Phoenix Fireblade.
Honda must have spent millions of Yen on getting the best compromise between power, noise, etc. so we put our faith in them. We are even leaving the ECU controlled flap inside.
If we were to build a lower slung example for ourselves we would use the standard trumpets and try to match the internal capacity of the original, together with matching the cross sectional area of the two inlet throats.
The standard airbox should also negate the need for mixture tweaking of the Power Commander or Dynojet variety.
Having said all this, Andy Bates does some very effective airboxes, obviously quiet enough to pass race regs.
Geoff and Eldon.

Thanks for the replys guys

Mike