After installing an OBX header to my Borla Race (Sport) CAT back, I developed a drone between 2800-3100 rpm. Not bad during 30 min commutes, but during a long drive, it would wear on you. This past weekend, I slipped a set of these in:



Picked them up from Mini Mania. They really work. Took nothing but the drone out of the tone. No noticable performance hit either. Perfect for me!

 

Interesting tip(s).

Where do they fit?
Nice trick.
Your ears thank you.
By the way my Milltek header/cat back exhaust do also have a tiny drone at 2900-3000 rpm. The solution is to turn up the stereo or speed up!

 

From what I understand, you tack weld these in the tube before the tip. Looks like a restriction device that might hold back hp too I have the opposite need...more decibles

 

They do look like tips, huh? They are actually inserts that go into the tailpipe post exhaust cans, then give them a small tack weld to stay in place.


That was my interm fix as well, minihune. Turn up the stereo, and cruise at 4k/95mph! Course this was on the Autostrada (Italian Autobahn). No real speed limit! BTW, is it just me or does 95mph in a MINI feel like 50 in other cars?

 

It does, when you think you're doing the speed limit you look down and you're doing 20 over.

 

Yep, they are small venturies, and since they taper back out to orginal pipe diameter, I can't see where that would have an effect? The gas just gets a little speed-up through them. Like I said, no noticable loss here... no change in exhaust tone, just an absence of drone.

 

If the gas needs to get through a smaller oriffice, that's restriction...hence, back pressure.

 

Perhaps, but not necessarily so, MSFIToy. The nature of gas flow through a venturi does not necessarily equal "restriction" or backpressure. Gas accelerates through a venturi, then decelerates after is passes through. Energy is conserved. Sure, at some point, as you reduce the venturi, gas will start piling up behind it - then you get backpressure. These neck down by 1/2" in diameter, and they are only 3" long, and they are inserted at the very, very end of the exhaust system.

Not a tweak for you. If you're in the market for more decibles, pick any header you wish and install without a CAT, then bolt it to a Borla Sport/Race, Magnaflow, or one of the louder exhausts. I personally guarantee you will get all the decibles you can handle, and then some! While way to loud for me, the banshee-scream at 6000rpm - 7000rpm will give you goose bumps...

 

This type of insert has been used on Harley Davidson motorcycles for years and have proven to be quite effective on race bikes. The venturi actually speeds up the extraction of gasses from the down pipe by creating a siphon type of effect. As gasses pass through the venturi insert, they speed up and - theoretically - they pull trailing gasses by creating a negative pressure within the mufflers. I used to design and build two-stroke expansion chamber exhausts. In designing such an animal, one must not only be concerned with issues such as backpressure, but also with things such as pulse, shape, exit timing, and volume. A “tuned” exhaust is just that - an exhaust that is tuned like a musical instrument to take advantage of sound pulses within the chamber. Although this is not a big concern with four-stroke MINI engines since they don’t scavenge and rely on pulse packing, one would think that some restriction would be beneficial.

 

Interesting...would like some data on this one. If it works and actually improves performance, I'm in

 

Me too, data please

 

then you need this