can someone measure the large diameter and length of an R1 carb trumpet for me please? I'm going to have a go at making some

I can measure them later if it helps...

What's brought this on then?

I'm working on a system to retain the standard trumpets using an airbox and fresh air intake from a secondary bonnet sealed airbox at the rear centre of the engine bay. Hopefully without the need for a large bulge; just a NACA scoop for the air feed...

Curious as to what made you go from standard MNR fare to an airbox?

Chris.

The first thing that made me think about it was noise. I wouldn't object to doing another track day but some tracks would object to my car.

I started reading up about airboxes and I learned that you can improve low end pull with a tuned air box without losing top end power, if you're careful. My engine is very flat below 5000 and then suddenly pulls when you cross the line. A tuned air box can lower the revs at which you go to warp speed by 1000 - 1500 RPM. I want that. And I like making things. And I just happen to have a K&N filter just doing nothing.

If I go to an airbox then I'll have room for trumpets, which are supposed to help smooth high RPM airflow and add a couple of BHP. Not a lot but who can say no?

Edit: and I'll get to play with vacuum forming which looks very cool

[Edited on 25-9-2006 by smart51]

You could always try what I did.
Just rolled the standard rubber trumpet over on itself. If you work it enough it holds its shape fine, and gives you loads of room.

Steve
Rescued attachment trumpets.JPG

I don't have any standard trumpets, which is why I'll make some.

http://www.locostbuilders.co.uk/viewthread.php?tid=39230

I remember that thread. It doesn't seem like 7 months ago.

The airbox I'm designing will fit under the bonnet. Most of the volume of the box will be over the gearbox. The port area will be about 50% larger than the R1 box and over 3 times the area of the throttle body so it will flow more air than the engine can take. It will be resonant a little slower than where my engine bogs down so increasing the useful rev range but it will be worse in the 2500 - 3000 RPM range (which I only use at 10 - 20 MPH).

Once above the resonant area, the airbox doesn't restrict the airflow, not as much as the throttle body, but it does help contain the noise.

With an air box, there will be room for trumpets. Can someone measure the length and bell diameter for me please?