How restrictive is the "stock" IS-F muffler?
02-11-15, 01:31 AM
#1
How restrictive is the "stock" IS-F muffler?
Hi everyone. I've been a formerly IS350 member here and now i finally upgraded to the F. I've been thinking about doing a full custom exhaust with no resonator and sec cat deletes. I plan to do a custom 2.5 inch x pipe to the stock isf mufflers. Is this a good idea? Any real whp gains to the stock mufflers? The reason i would like to keep the stock mufflers is i don't want any sort of droning. I love my mark levinson stereo. Any tips or advices would greatly be appreciated.
02-11-15, 06:59 AM
#2
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I would think its pretty restrictive as the borla and multiple other exhausts have been shown to add significant whp over stock, and most of them utilize mufflers. I don't know if the OEM muffler is more restrictive then one of theirs, its possible that it is, but by eliminating the secondary cats that alone should give you some power increase.
02-11-15, 08:06 AM
#3
This thread may answer your question:
https://www.clublexus.com/forums/is-...r-innards.html
My previous exhaust system utilized the stock mufflers modified with two inlets. It's all explained in the referenced thread along with picts of the stock mufflers cut open.
Lou
https://www.clublexus.com/forums/is-...r-innards.html
My previous exhaust system utilized the stock mufflers modified with two inlets. It's all explained in the referenced thread along with picts of the stock mufflers cut open.
Lou
02-12-15, 10:17 AM
#5
Every aftermarket exhaust I've seen is a straight pass through muffler. The gasses do not have to pass through a series of chambers like with the stock exhaust. This alone adds some restriction to the stock exhaust.
However, I would say most of the restriction of the overall system is removed by going with true dual piping and eliminating the secondary cats. The stock pipe going from 2->1 is a restriction, and then when the single pipe branches back out to 2, the pipe is pinched.
Just my guess, but I would say going true dual but using the stock mufflers would give you at least 70-80% the flow of an aftermarket catback.
On that note, I'd say look into the Borla catback. I was like you when searching for exhausts, in that I did not want drone. I've had many loud exhausts in my time and I was ready for something tame. The Borla for our cars is the perfect answer. Once broken in, it's only a slight notch louder than stock, but you still get all the benefits of the extra flow.
However, I would say most of the restriction of the overall system is removed by going with true dual piping and eliminating the secondary cats. The stock pipe going from 2->1 is a restriction, and then when the single pipe branches back out to 2, the pipe is pinched.
Just my guess, but I would say going true dual but using the stock mufflers would give you at least 70-80% the flow of an aftermarket catback.
On that note, I'd say look into the Borla catback. I was like you when searching for exhausts, in that I did not want drone. I've had many loud exhausts in my time and I was ready for something tame. The Borla for our cars is the perfect answer. Once broken in, it's only a slight notch louder than stock, but you still get all the benefits of the extra flow.
Last edited by fearnight; 02-12-15 at 10:27 AM.
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