MileHIFcar

Lou,

Do you know what is the cell count on the secondary cats?? They can't be as restrictive as the primaries are??

Anyhow I've had it with the drone with the Borla with the addition of the headers! I think I might be going back to the stock exhaust for my sanity

Just trying to figure out how much power I will lose going back to the stock exhaust? I'm assuming the majority of the gains with the exhaust system are losing/getting rid of the stock manifolds with the primary cats account for maybe 90% of the power gained?

So once again I would be FBO minus the stock exhaust (secondary cats/mufflers)..............

What do you guys think??? I really don't want to give up any power but the drone is beyond annoying and maybe I'm just getting older lol

MileHIFcar

Posted by Cayman: "If you install cats the exhaust tone will go down a bit. I'm actually surprised you find the header/Borla setup too much for you. It's the quietest setup i've come across with very tolerable "drone" levels.

EDIT: Forgot I had laid some sound deading material down awhile back. That could be why I'm good with the sound. I added this because the SIKKY/JOEZ combo was TOO much for me. I added this material and it was more tolerable and then with the change to Borla it was perfect.
https://www.clublexus.com/forums/is-f...ing-trunk.html "

Yea I was trying to save myself the $700 for two GESI cats.......and then that might not have solved the drone issue for me and then the cats would've already been welded onto the Borla?

What you said makes sense though the sound deading material probably is the difference I bet? Just like the Sikky/Joe-Z combo was too much for you, that's where I'm at with the PPE/Borla

Just trying to figure out how much I might lose going back to the stock exhaust but with PPE headers/Tune/Tuned intake/.......I'm guessing I shouldn't lose that much hopefully??

flowrider

iTrader: (9)

No I don't. That's a spec that Lexus wouldn't share. However, returning to stock, would not be a good move because the rear crush on the axel back portion is a big restriction IMHO.

Lou

FilwithanF

iTrader: (1)

Hey Gabe, hope you're well sir! I can't share any experience on the ISF, obviously, however, I do remember going from a Full Race 3" to a 2.5" exhaust on my 2008 Civic Si when I was full bolt on and cammed, and my tuner said I basically lost no power at the elevation we're at. You figure we lose between 16-20% (depending on the air density that day) at our elevation; so if gains with an exhaust on an ISF are 15-20hp (per RR Racing's website), you're looking at potentially losing 12-16hp, if not even less. Personally, I'd be ok with that and in fact, I think I will run the PPE headers with the stock exhaust when I buy the car lol. Just not worth the noise for that little amount of power for me. Or, per Lou's comment, I would try running the Borla axle back and keep the stock mid-pipe with the secondary cats in place.

caymandive

iTrader: (2)

I've ridden in an F with just the Borla axle back and the drone level was more than with the full exhaust system in place. Not sure how an axle back combined with headers would sound, but I'd assume not much different than with just the axle back. Without doing some back to back dyno sessions, I don't think anyone can give you a close estimate on power differences, but my bet is close to 20whp loss by changing back to stock exhaust. On the plus side with headers and tune you'd still be putting down good power. Why not try adding some sound proofing material to your trunk area and under the rear seat and see how that goes first since it's pretty cheap and easy enough to do.

SRTISF

iTrader: (1)

If you want more power and want your car to stay quite, N2O is the way to go

https://www.clublexus.com/forums/2ge...isf-or-v8.html

MileHIFcar

Yea guys I've been going back and forth on this issue for a couple weeks now deciding between putting on side branch resonators to cancel out the drone, or welding on just the stock mufflers to cancel out the drone???

The thing is I don't want to lose any power, but want to get rid of the drone! We have another discussion going on in this thread here about the side branch resonators/j-pipe/Helmholtz chambers:

https://www.clublexus.com/forums/is-...-system-2.html

John12ISF

Bumping this thread for more feedback... Are people keeping the stock cats/midpipes with aftermarket headers, or is the only choice to go with high-flow cats on these headers+stock exhaust setups?

For others also interested, here are a handful of random Youtube videos I found for sound comparison (not my car):

Lexus ISF Sikky Headers + Stock Mid-pipe Muffler Delete

2008 Lexus ISF PPE Headers only- stock exhaust. (Audio only)


Sikky ISF header on stock lexus ISF

Lexus IS-F Sikky Headers Stock Exhaust Cats Delete and Reasonator

Lexus IS-F dynorun stock exhaust