Celsior/LS400 Exhaust Idea

[INASNT]

Hey people just got an 1990 celsior/ls400 as my daily driver.

I want a nice V8 rumble without being 2 loud and drouning in the cabin while crusing and was thinking of replacing the 2 x stock cats with 2 x high flow ones, removing the 2 x middle mufflers and replacing the 2 x rear mufflers with 2 x straight through mufflers.

What will my celsior sound like if i do this, without putting in new pipework or an x-pipe?

Whats the diameter of the stock exhaust?

 

[JBrady]

Unless your stock cats are damaged it will not help much to replace them with "high flow" ones. If you have a third cat at the Y section that may be another issue as it may have been installed as an import requirement and its design and flow in question.

As far as the rear muffler replacement. Go ahead and drop the mufflers off the car completely and you will be surprised how quiet it still is on only those middle mufflers. As suggested in the another post here you may want to keep the stock rears and delete the middle ones.

 

[Kiwi.in.aus]

I run 3 " pipe from the last join at the rear all the way out with no rear mufflers at all and as Mr Brady said it is barely any louder , you can just hear it with the window down , just enough so that you can hear a rumble .

The strange thing is you can hear it coming from the bottom of our street from inside the house , not from the actual exhaust noise but more from like an air pulse disturbance , kinda like being 1 1/2 K's away from a drag meet , you can feel the pulse in the air .

 

[INASNT]

So the middle mufflers are the main noise absorbing ones hey?

What will it sound like then with the middle mufflers removed and some new tips on the stock rear mufflers?

The stock system is on 2 inch press bent right?

 

[INASNT]

What do you guys think just 2 of these rear mufflers would sound like with the rest of the system kept stock? I only want a small b8 rumble when giving it some

http://www.onautos.com.au/store/cart.php?target=product&action=view&product_id=16696&category_id=261

 

[UTA LS]

I've taken off the middle mufflers and just run the back ones. Its still pretty quiet, you can definately hear it when I get on it though.

 

[INASNT]

Did you just put a bit of 2 inch pipe between the 2 flanges when you removed the middle mufflers?

 

[jibby]

CHANGING YOUR ORIGINAL CATS OUT TO A NICE HIGH FLOWING CAT IN A 1991 IS400 I GAURANTEE WILL MAKE A VERY NOTICEABLE DIFFERENCE IN POWER GAINS!!!!!!! I changed my 1992 SC400 original catalytic converter to a Magnaflow high flowing 2 into 1 catalytic converter and noticed a big change in exhaust flow and performance. I kid you not it was almost as dramatic as when I changed my stock mufflers out to the straight thru mufflers, not quiet that dramatic but close...

JBrady, First off, I really hate to disagree with you but on this one I must. I always seem to be in some kind of heat with you on something and that is not my intention. Having said that and with all due respect how and why do you think that changing out the old stock clogged cat conv. on 1991 400 to a new highflow cat will not make a difference? I would bet my house that noticeable gains would be made on an older car like that.

I compared the two converters and tested right before and after my change out maybe 4 months ago and I really didn't expect to notice power gains like I did. This is the second time I heard you post that changing your cat to a high flow will not make a difference... However, I do think you may be right on with that statement if you are only referring to newer model cars... I believe this to be true on the newer cars maybe 1998 and up... Here is yet another pic of my current exhaust system to show some proof to my claim...


PS - This exhaust is very loud at full throttle, soft deep rumble at idle... I have the Megan N1 staight thru mufflers on... Straight thru's are very loud at high RPM's.

 

[INASNT]

jibby

Any change of recording your car at idle and then while your revving it?

How does it sound like cruising at 100km/h?

 

[jibby]

No I can't do that sound thing for you sorry pal - I can describe how it sounds in detail. I can drive it and be quiet around the city cruising at lower rpm's, you can even have mom in the car and she won't complain. Hit the gas hard and that all changes and I would say anything over 2500rpm starts getting loud. If hit the nos it roars. This is a good smoothe sound, I don't mind it. It doesn't shake houses or wake up the neighborhood when coming home very late at night and driving it normally.. I would say it is as loud as a stock 5.0 mustang except noisier at full throttle...Hope that description helps... This is also a picture of what the straight thru mufflers will look like...

 

[JBrady]

CHANGING YOUR ORIGINAL CATS OUT TO A NICE HIGH FLOWING CAT IN A 1991 IS400 I GAURANTEE WILL MAKE A VERY NOTICEABLE DIFFERENCE IN POWER GAINS!!!!!!! I changed my 1992 SC400 original catalytic converter to a Magnaflow high flowing 2 into 1 catalytic converter and noticed a big change in exhaust flow and performance. I kid you not it was almost as dramatic as when I changed my stock mufflers out to the straight thru mufflers, not quiet that dramatic but close...

JBrady, First off, I really hate to disagree with you but on this one I must. I always seem to be in some kind of heat with you on something and that is not my intention. Having said that and with all due respect how and why do you think that changing out the old stock clogged cat conv. on 1991 400 to a new highflow cat will not make a difference? I would bet my house that noticeable gains would be made on an older car like that.

I compared the two converters and tested right before and after my change out maybe 4 months ago and I really didn't expect to notice power gains like I did. This is the second time I heard you post that changing your cat to a high flow will not make a difference... However, I do think you may be right on with that statement if you are only referring to newer model cars... I believe this to be true on the newer cars maybe 1998 and up... Here is yet another pic of my current exhaust system to show some proof to my claim...

First off you did not read the original question. INASNT asked about sound levels and wondered if "high flow" cats would help that. You also may not realize that his is an Australian car and many imported cars had a third poor flowing catalyst installed (not factory). My answer addressed both of these.

Now, I also state that IF the stock cats (OEM) were not damaged there would be very little power gained in replacing them with "high flow" catalysts. Now, you have stated MANY times that yours was clogged/damaged. Obviously if you have a damaged cat you need to replace it and you will gain back the lost performance.

Something else I noticed in a previous picture of yours and again in this picture is that the dual pipes from the front cats and going into your Magnaflow cat seem to be the stock pipes. Your center pipe appears to be the stock size or possibly a single 2.5" pipe. Is this correct?

Also, it is unclear on whether or not you still have the 2 stock catalysts bolted to the exhaust manifolds. Do you have 3 cats or only the 1 Magnaflow?

 

[jibby]

John thanks for the reply, I thought you maybe ignoring me for minute there. First off my car has the stock exhaust setup still intact right up until the highflow center cat. I have the two little cats still installed at the down pipes and you are correct in all your assumptions about my exhaust, pipe sizes, etc.. and the stock center pipe. The headers and the two litte cats will be changed out very shortly..

Back on topic now my original stock cat was not damaged or clogged anymore then any other older SC as far as I could tell and my car had only 98,000 miles on it at that time. I closely looked at the old stock cat when it was removed and it was blackened on the insides. For kicks I tested and ran an air hose pointing thru the stock cat inlet and the flow was crap and barely came out the other end, but then I put the new magnaflow cat to the test and the air pushed right thru with the greatest of ease.. Then went the install...and after the cat change out I immediately noticed a big improvement and no other pipes were changed out at that time. That is my experience with the stock catylitic converter... Oh and also the noise levels did not change either with new cat, from what I could tell....That is what I base my claims on...

 

[INASNT]

So the stock system uses 2 little cats off the downpipes and then another in the centre?

The thing with the stock cats I have found on my previous cars is that after so many years the main use of them in filtering nasty exhaust gases has gone past the stage where they dont do their job anyway.

 

[JBrady]

John thanks for the reply, I thought you maybe ignoring me for minute there. First off my car has the stock exhaust setup still intact right up until the highflow center cat. I have the two little cats still installed at the down pipes and you are correct in all your assumptions about my exhaust, pipe sizes, etc.. and the stock center pipe. The headers and the two litte cats will be changed out very shortly..

Back on topic now my original stock cat was not damaged or clogged anymore then any other older SC as far as I could tell and my car had only 98,000 miles on it at that time. I closely looked at the old stock cat when it was removed and it was blackened on the insides. For kicks I tested and ran an air hose pointing thru the stock cat inlet and the flow was crap and barely came out the other end, but then I put the new magnaflow cat to the test and the air pushed right thru with the greatest of ease.. Then went the install...and after the cat change out I immediately noticed a big improvement and no other pipes were changed out at that time. That is my experience with the stock catylitic converter... Oh and also the noise levels did not change either with new cat, from what I could tell....That is what I base my claims on...

A properly functioning cat will not be black. A properly functioning cat will flow well. Your observations indicate the cat you removed was bad and creating a huge restriction. It is no wonder you noticed a big improvement. If the cat was working properly the restriction would be very similar to the Magnaflow one and the gains would have been minimal.

BTW most cars did not have the 3rd catalyst. This was California and Canada. Australia has different laws and as I said some had 3rd cats installed that were lower performance than stock. The stock cats I generally refer to are the two attached to the manifolds.

 

[jibby]

Sounds good enough to me John. However, on a closing note I still must wonder why and how this stock cat converter of mine got fouled? My car was owned by an older doctor, and this car was dealer maintained perfectly from new. I purchased it with 92,000 original miles. As I said before I have bought, sold and drove over 50 or so of these used earlier model SC400's and LS400's and this perticular SC400 I have now ran the strongest and had the most power out of all the other ones I drove. For that reason alone I decided to keep this SC400 rather then re-sell it and make money.. Again, it ran stronger then all the others with the clogged or faulty blackened Cat...How can this be with the a clogged cat? This car also passed California State Emissions with the old cat on just for the record. My car was 100% stock when I bought it, no power alterations what so ever... Just don't understand it...and maybe never will. I still think to some degree that changing out the older stock cats to the new "highflowing" cats will have some benefit...

One last question - Any idea on what gains I should expect to see by installing your designed S&S headers and also the new down pipes without the two little cats on my current exhaust setup? Any guesses would be appreciated, because I may try to dyno before and after and then post results on this thead...Take a stab at it to see how close you come...

Inasnt- Sorry for taking over the thread and hopefully these discussions of ours have helped you in some way with your future exhaust decisions....

 

[INASNT]

Jibby

Discuss away mate no prob.

 

[ismo67]

My Lexus LS400 -91 got the Stainless Steel exhaust pipework today finished.

Changed:

- S&S Headers with Jethot coating (not stainless)
- Magnaflow High Flow big cats
- X-Pipe large
- Resonators 2pcs
- 2.5 pipe but last piping is 2.25" with Megan racing 2.5" Straght Trough Mufflers
- flexible parts 2pcs to avoid resonanse and keep headers not to crack.

Let see after few months how it really works.
It is a summer car and still winter... hrrr

 

[jibby]

Now that is an exhaust setup from engine to bumper, very nice.....Wow that is going to flow..... How does it feel after you did that? Headers, straight thru's that must shake the neighborhood, is it loud or what?

 

[INASNT]

Jibby

Did you notice the smell of rotten eggs from your stock cats when accelerating hard?
I am noticing that on mine at the moment.

I also had the same problem with a 3 inch high flow cat on my other car when i started pumping over 300kw@wheels worth of air through it also.

The rotten egg smell seems to be of the internals of the cat burning meaning the internals aint functioning properly.

 

[jibby]

Nothing like that with my stock cat and definetely nothing like that with the new MagnaFlow Cat.. I have never heard of that before.. Rotten eggs? That sounds like a stinky situation:yuck: