sorry for the dumb question but,
Can anyone explain me why this muffler has a bottle neck before the curve?
i tought bottle necks were bad for performance, and usually removed from b-pipes and so on...

 

I think it is because you can fit it on the stock midpipe.....

SMSP has always advised removal of all bottlenecks as these things do nothing but impede flow....

 

so, the only reason why the n1 muffler has a bottleneck is because it can FIT the oem b-pipe?? now that's odd, spoon makes a "race" muffler and installs a bottle neck on it..
so it can be compatible with the oem pipe... can this be the only reason?!?

 

it is compatible with both oem and aftermarket b-pipes which would remove bottlenecks

 

so should i, or should i not take out the bottle neck? - i already have a b-pipe with no bottlenecks.

anyone?!

 

You have an older version of it. the newer versions have eliminated this bottleneck.

 

Nice toes!

 

Lets clear up a misconception here
A Bottleneck in a B pipe would be a 2.25" B pipe with a say 5" section of 2" piping (Like the OEM B pipe) That is a Restriction...

A Bottleneck Is NOT when say a 63mm B pipe has a 60mm section that is less than 1/4" long Like where the B pipe connects to the Cat, In fact after talking to a friend of mine (The guy took Physics 1 and 2 at the same time in college) He says that small sections like I stated would actually increse the Exhaust gasses velocity Helping it along the way. It is NOT a restriction.

 

actually the bottleneck is 45mm stock size and opens up to 60mm... :/

so i bought an older version of the muffler?!

 

Got to respectfully disagree. Fluid Dynamics actually provides the explanations for fluid flow more so than Physics. Physics is more for forces/applied loads.

We can define "bottle necks" in 2 ways. One being tapered and the other abrupt. The bottle necks found in many of the cat back systems available are abrupt which are bad. These generate turbulence which isn't good for fluid flow. How many times have you read that someone thinks his new hi flow cat flows sooo much better since he hears the whooshing noise? While a hi flow cat does flow better than a stock cat it still encounters an abrupt bottle neck at the B pipe and this causes turbulence, thus the whooshing noise.

In exhaust systems if there is a change in diameter it should always be from smaller to larger. Since this isn't happening in most of these systems the next best bet is to have a smooth transition from larger to smaller at the connections. When we removed the Tanabe 2" OD x 2" long bottle neck on a Toda header, Carsound equipped ITR and it was replaced by a 2-1/2" ID (same as cat outlet) x 2-1/4" OD long taper adapter the owner saw a 4whp gain across the rpm band.

Headers have tapered bottle necks which are better described as a cone/funnel with a specific merge angle. They successfully take 2, 3, 4 or 5 tubes and gently merge them into 1 without adversely effecting back pressure and increasing the velocity through a tube which more than likely has a smaller area then the summation of the tube areas merging into it.

So the bottom line is get rid of any of these abrupt changes in the inner diameters at joints. I believe the only commercially available cat back system that doesn't have a mismatch at the Cat outlet is the Kakimoto which has an ID of 2.50". The stock ITR B pipe is 1.75" ID, the Tanabe is 1.88" ID and any 60mm system that is still 60mm at the B pipe flange has roughly a 2.25" ID. I don't consider my 2-12/" OD system as commercially available since it has about 12-13 welds to be made to put it together. But it has a 2-1/2" to 2-9/16" ID at the B pipe flange and I don't have any knowledge of how HyTech does their B pipe but I would be surprised if it didn't have an ID of 2-1/2" at the flange.

If anyone wants to host bottle neck and mismatch pictures just drop me an email. I have a few pictures.


[Modified by SMSP, 11:03 AM 3/6/2002]

 

Kakimoto R is 2.5" ID at the cat flange and the b-pipe is 67mm (2 5/8"). So it is smaller to larger!!

 

Here are some info might help you guys:

Stock ITR Muffler flow rate 112 L/SEC
Spoon N1 Muffler flow rate 139 L/SEC

Stock ITR B-pipe flow rate 115 L /SEC
TypeONE B-pipe flow rate 141 L/SEC


Please post other exhaust's flow rate to do this comparison.

 

thanx everyone!

 

At what conditions were these flow rates measured?

 

Flow bench. All info from the manufacture.

 

Nice muffler.

Where did i already saw that N1 ?!?!?!

Darkteg, tu não és um darksiderrrrrrr, porque se tu fosses um darksiderrrrrrrr já tinha metido isso mesmo com o estreitamento.
Um abraço,

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