hey guys, so just a quick question. im going to a exhaust shop over the weekend to get my mufflers on my is350 taken out, but i was just wondering if anyone had done any of the three deletes *muffler/cats/resonators* on a stock IS350 exhaust and what the noticed when they did it *HP gains worth mentioning, good or bad new sound from exhaust* you know just the basics, OR fi anyone knows which one out of the three would be best to do . ?
thanks!
maticcis

 

If you delete your muffler's it'll have the most noticeable sound difference.

 

Don't delete the cats. Just do the two secondary cats, resonator, and the mufflers. Before I had an Invidia Midpipe with an HKS Hi-Power exhaust. It was loud and deep but I wanted louder. I sold the Invidia and had the secondary cats and resonator deleted on the stock midpipe. It sounded much better and the cabin became quieter too for some reason. Recently, when I was burning my exhaust tips blue, I couldn't help but to start the car without the mufflers attached and it was so loud and crazy deep. Now I'm planning to sell my HKS mufflers and do quad tips. Don't delete the cats, it'll become high-pitched and no longer a deep tone. And don't leave the big resonator on without mufflers, it makes the exhaust sound "muffled".

 

thanks for the heads up! ide rather ahve quieter and faster then louder and not as fast. so do u think mufflers would ad ANY gains?


i know ur saying delete all three of thouse things, but i think im going to take this kinda slow, so if u had to do 1 of the 3 which one would u choose?

 

Doing any of the removals won't make a difference. I haven't dynoed my car or anything but I can feel no noticeable gains. I'd have to do mufflers+resonator first. I wouldn't do one at a time except for the secondary cats, you can leave those two. If you remove just the mufflers, the resonator makes the exhaust muffled and sounds like crap. If you remove the resonator but leave the mufflers alone, that would be pointless since the mufflers get rid of most noise anyhow.

 

"f you remove just the mufflers, the resonator makes the exhaust muffled and sounds like crap. If you remove the resonator but leave the mufflers alone, that would be pointless since the mufflers get rid of most noise anyhow."

Do you think it would be worth it to remove only the secondary cats?

 

No, because that wouldn't increase noise or power I think. When my muffler shop was removing stuff, they did the resonator first and I wasn't satisfied yet when they revved it. So I told them to go ahead and delete the two secondary cats for $60 and they revved it again and only made it the slightest bit louder. If you remove the secondary cats but leave the resonator and mufflers, it's not going to have any purpose.

 

I did a resonator delete (with my Tanabe axle back) and HATED it. Just ordered mid pipes to get rid of my factory mid section. Personally, I would try the cats first, and wish I had. With the resonator out, I got a terrible drone at around 2k rpm when driving at highway speeds. Just awful!

 

^ If you ordered the Invidia Midpipe, the drone is worse. I had the Invidia midpipe first but sold it. Then I cut off the secondary cats and resonator on the stock midpipe and the cabin noise was much less than having a midpipe. Not sure about what will happen with Tanabe or Megan midpipes.

 

Any decent axle-back exhaust, which simply improves the pipes and mufflers (deletes nothing) plus adds some sound (how much depends which you get) and is actually legal will add about 7 hp.

Removing the secondary cats (ie an illegal midpipe, which will fail emissions in CA by the way) adds about 1 hp.

I'm unaware of any gains at all from just the resonator.

Removing the primary cats is physically impossible unless you're getting headers (also illegal in CA) because they're part of the stock exhaust manifolds.... but the headers will give you 10-15 hp (likely more from being headers rather than stock manifolds than from the cat deletes.... modern cats aren't very restrictive at all)

 

The noise that I got with the resonator delete wasn't so much a drone, as it was a 40hz steady hum that you would expect from an old truck with a hole in the muffler. If the noise that I get in the cabin with the Invidia mid pipes has more of a higher pitch rasp, I can deal with it. Tracking says they will be here Monday, but not sure if I will have time to put them in. Probably not getting off work til around 7, and have to be back in early on Tuesday.