IS F (2008-2014) Discussion topics related to the IS F model

How bad is the oem Exhaust Manifold design?

Thread Tools
 
Search this Thread
 
Old 04-08-14, 07:17 AM
  #1  
mikellucci
Instructor
Thread Starter
iTrader: (56)
 
mikellucci's Avatar
 
Join Date: Nov 2005
Location: Ohio
Posts: 814
Received 28 Likes on 15 Posts
Default How bad is the oem Exhaust Manifold design?

Has anyone decatted or gutted the cats on the stock IS-F headers? I'm really curious as to how restrictive the cats are on the headers or if the runner design is just that bad. Something is a miss if Sikky and PPE can easily achieve a 30+ whp output.

Just wondering if anyone has looked into it further besides buying an aftermarket option?
I have both Sikky headers and a spare set of oem headers that I had jet-hoat coated in case I added a nitrous setup. Trying to decide if it makes more sense to just install the oem headers (and gut the cats) with the realization nitrous is in my future.
Old 04-08-14, 05:22 PM
  #2  
MisterSkiz
Racer
iTrader: (2)
 
MisterSkiz's Avatar
 
Join Date: Nov 2011
Location: IL
Posts: 1,599
Received 114 Likes on 73 Posts
Default

I was wondering this myself as well....wonder if anyone (Sikky, PPE) has put them up to a flow bench....
Old 04-08-14, 05:41 PM
  #3  
mikellucci
Instructor
Thread Starter
iTrader: (56)
 
mikellucci's Avatar
 
Join Date: Nov 2005
Location: Ohio
Posts: 814
Received 28 Likes on 15 Posts
Default

I was just reading up on past Nitrous threads and it got me thinking about the runners seeing that aftermarket headers pose issues on a high shot whereas the stocks seem OK. If the stock runners are decent enough to flow with NOS the cats have to be the real bottleneck perhaps?

I'm in a position right now where I can swap my stock manifolds in pretty easily or keep the Sikkys...not sure what I'm going to do.
Old 04-11-14, 06:27 PM
  #4  
H60Driver
Driver
 
H60Driver's Avatar
 
Join Date: Nov 2013
Location: TEXAS
Posts: 170
Likes: 0
Received 0 Likes on 0 Posts
Default

Bump for curious owner wanting to know the difference between sikkys and catless stock?
Old 04-11-14, 06:34 PM
  #5  
rmillsISF
Pit Crew
 
rmillsISF's Avatar
 
Join Date: Oct 2013
Location: Tennessee
Posts: 199
Likes: 0
Received 3 Likes on 3 Posts
Default

I can almost promise you the 30HP+ gain is 99% from removing cats. 2gr engine is the same way.
Old 04-11-14, 06:59 PM
  #6  
flowrider
Lexus Champion
iTrader: (9)
 
flowrider's Avatar
 
Join Date: Nov 2008
Location: Arizona
Posts: 10,598
Received 1,943 Likes on 1,369 Posts
Default

^^^^The attached graph says different. The JoeZ is a much improved exhaust vs. stock and does remove cats, but is worth 20 HP over stock.

Lou
Attached Thumbnails How bad is the oem Exhaust Manifold design?-typicalprogression_zps36e65999.jpg  
Old 04-11-14, 10:05 PM
  #7  
occxlr8ed
Driver School Candidate
 
occxlr8ed's Avatar
 
Join Date: Jan 2014
Location: SA
Posts: 16
Likes: 0
Received 0 Likes on 0 Posts
Default

^ uh where is the stock decatted headers on the graph??
Old 04-12-14, 02:27 AM
  #8  
MK4Sup_isF
Lexus Test Driver
iTrader: (10)
 
MK4Sup_isF's Avatar
 
Join Date: Oct 2008
Location: CA
Posts: 1,372
Likes: 0
Received 3 Likes on 3 Posts
Default

Originally Posted by lowrideraz
^^^^The attached graph says different. The JoeZ is a much improved exhaust vs. stock and does remove cats, but is worth 20 HP over stock.

Lou
Joe Z is a cat back system because the exhaust pipes start behind the main cats. It removes secondary cats only, which are much less restrictive than the main cats
Old 04-12-14, 05:21 AM
  #9  
mikellucci
Instructor
Thread Starter
iTrader: (56)
 
mikellucci's Avatar
 
Join Date: Nov 2005
Location: Ohio
Posts: 814
Received 28 Likes on 15 Posts
Default

This all started discussing Exhaust MANIFOLDS and the Main/Primary cats removal. Not sure why we are talking secondary cats as the information is clearly out there.

I'm assuming no one really knows the answer to the original question and the gains are likely greater just going with a Sikky or PPE header. However, on a high nitrous shot aftermarket headers prove deficient vs the stock manifold runner design. A decatted stock manifold could prove to be a better choice for those of us running or considering a nitrous setup.
Old 04-12-14, 10:17 AM
  #10  
flowrider
Lexus Champion
iTrader: (9)
 
flowrider's Avatar
 
Join Date: Nov 2008
Location: Arizona
Posts: 10,598
Received 1,943 Likes on 1,369 Posts
Default

Sorry, I misunderstood. You're talking about removing the primary cats. If that were to happen, the stock manifolds would require major surgery since the primaries are part of the manifold. I'm not aware of anyone doing this.

Lou
Attached Thumbnails How bad is the oem Exhaust Manifold design?-factory-exhaust-manifolds-is-f-manifold-a.jpg  
Old 04-12-14, 10:33 AM
  #11  
MK4Sup_isF
Lexus Test Driver
iTrader: (10)
 
MK4Sup_isF's Avatar
 
Join Date: Oct 2008
Location: CA
Posts: 1,372
Likes: 0
Received 3 Likes on 3 Posts
Default

Originally Posted by lowrideraz
Sorry, I misunderstood. You're talking about removing the primary cats. If that were to happen, the stock manifolds would require major surgery since the primaries are part of the manifold. I'm not aware of anyone doing this.

Lou
Not really hard once you have the manifolds off the motor. You can just chip at the inside of the cats and clear up the inside. This has been done countless times on other cars
Old 04-12-14, 10:41 AM
  #12  
I8ABMR
Lexus Fanatic
 
I8ABMR's Avatar
 
Join Date: Sep 2007
Location: Waiting for next track day
Posts: 22,608
Received 102 Likes on 67 Posts
Default

Will the car pass a smog test with secondary cats out ?? Are these exhausts for "off road use" only . Many members have exhausts and we have cars that are now 5-6 years old. Im sure some had to go through smog
Old 04-12-14, 11:09 AM
  #13  
VtotheJ
Lexus Champion
iTrader: (2)
 
VtotheJ's Avatar
 
Join Date: Apr 2011
Location: NY
Posts: 2,546
Received 5 Likes on 5 Posts
Default

This is interesting. Many people like myself have removed secondary cats but not primary cats. Removing the primaries would definitely cause a CEL, not sure how you'd fix that...maybe the same way you do it with aftermarket?
Old 04-12-14, 11:46 AM
  #14  
mikellucci
Instructor
Thread Starter
iTrader: (56)
 
mikellucci's Avatar
 
Join Date: Nov 2005
Location: Ohio
Posts: 814
Received 28 Likes on 15 Posts
Default

Any o2 sim should correct the CEL just as if a pair of sikky or ppe catless headers were installed.

It's pretty easy to DECat any header catalytic converter even on the vehicle. I've seen it done many years ago with a pry bar and torch.

I have a set of oem headers that have been jethot coated:

Old 04-14-14, 05:44 PM
  #15  
etohprn247
Driver School Candidate
 
etohprn247's Avatar
 
Join Date: Apr 2011
Location: DFW,Tx
Posts: 44
Received 0 Likes on 0 Posts
Default

OMG you guys are Hardcore Ballers or your a train mechanic ....With CEL issues and having to drop half or part of engine to install/modify primary cats etc.( in our ISF specifically) and if issues arrive or reselling, yall just pay another $1k to reinstall headers back to stock? Mikelucci...did you remove catalytic converters just to jetcoat them, man that's a lot of work ;P


Quick Reply: How bad is the oem Exhaust Manifold design?



All times are GMT -7. The time now is 08:06 AM.