CleanCL

he said magnaflow cats, which are car-sound, imo one of the best companies to produce hi-flow cats.

jibbby

Ok - The S & S Headers where they connect to the down pipe is 2 1/2"....Note: The SC400 S&S Headers will not just bolt on, be aware that you are going to need to shorten your down pipes...THe Headers will lower your Exhaust setup by I think 3"..These headers were designed originally for the GS400....Something I am just now finding out myself...

If you don't plan on turbo'ing or supercharging you should keep your rear exhaust section at 2.25" rather then 2.50" mandrell.... The 2.25" flows just a little bit smoother then 2.50" I kid you not... I currently am running a 2.50" rear section exhaust section with straight thru mufflers and wish I would have stuck with the 2.25" mandrell piping....

I learned this by arguing with the designer of the S&S Headers and many other exhaust experts...They say as the exhaust gases pass the X section the 2.25" is proven to be the best fitting size for exhaust flow and proven better then the 2.50, and 3" rear sections.... I have seen flow charts and am now conviced the 2.25" mandrell rear section for non AFI is the best.....Something to consider that is all I am saying...

ScottURnot

iTrader: (33)

Lets just say I paid too much.

ScottURnot

iTrader: (33)

They are Magnaflow, You really think they are more restrictive than stock?

ScottURnot

iTrader: (33)

Thanks for all the info. I am supercharging so I should be good (I have my supercharger setting in the shop) For what its worth my mufflers ar actually 2 1/4" the exhaust tubing is 2 1/2"

CleanCL

jibby - i think MOST would agree generally speaking that 2.25" is the better size. and if you think about it, DUAL 2.5" REALLY opens the exhaust up. i'm sure low end suffers. but i'm suprised the headers do no provide enough backpressure to allow for a 2.5" exhaust.

JspecSC3

iTrader: (4)

My goodness! You are ready for a blower!

jgscott

iTrader: (1)

The stock Cats are Metal substrate Cats. Metal substrate are the highest flowing Cats you can get. The Magnaflow/Carsound are Ceramic, not Metal substrate. The stock Metal Substrate Cats will out flow the Ceramic Cats. Also the stock Cats were placed off the Header to heat up fast. The faster and Hotter the Cats get, the more the inside expands, thus the more they flow.

CleanCL

that's some good info. but has anyone ran a flow test on the stock cats? i thought planet soarer did?

jgscott - are you on acurazine? i have an 01 cl-s and am building a stroker for it.

jibbby

I was suprised too....I always figured no exhaust is the best exhaust, also thought bigger pipes always flow better then smaller pipes....I was wrong...

Scotturnot - If your going to supercharge then bigger pipes are better, because you will be flowing alot more then an NA motor...Maybe even 3" pipes may be best.... First off I love the idea of Supercharging Lexus motors so don't get me wrong when I say this.... I just want to let you know I have heard many people are dumping their superchargers for turbo's on these motors ...Reason being either they can't get enough power out of them and or they experience belt slippage at high RPM's which is the worst......

If I were to supercharge your motor I would really try and get a dual belt drive crank pulley where you have a double crank pulley. One belt to drive the engine, timing etc like stock.. and a second belt to just run the supercharger independantly... You need to (harmonic) balance that new double crank pulley.. .. Just a suggestion that may be a huge benifit to your supercharger setup........

Lextreme.com is currently in the process of designing that double crank pulley.....

jibbby

OK to put this beast to rest..... I switched to a highflowing magnaflow 2 into 1 catalytic converter on my 1992 SC400 with 110,000 miles on it 8 months ago.. I took the stock blackened and clogged cat and put the new magnaflow cat next to it and blew compressed air threw both...The stock cat I felt nothing practically come out the back and the Magnaflow Cat passed air big time... In addition to the magnaflow cat flowing better it also replaces a restrictive stock Y pipe with it's own built in highflowing Y... (2 into !)...It helps in two areas and not just one....

I then road tested my SC400 before and after the Magnaflow cat was installed. I expected nothing from a highfowing cat. I didn't think I would feel any gains what so ever even after I did that compressed air test......Well let's just say I was pleasantly suprised and the change was very noticeable. I could defenitely feel a gain in horse power, no dought about it.... Also, keep in mind my 1992 SC400 car was dealer maintenained and always ran perfect.. No reason my stock Cat would be any worse off then any other older 100,000 mile Lex.....In conclusion I don't care what independant studies show or say but for a $130 bucks it's like changing out your rear mufflers almost, I kid you not.... Try it and tell me if I am wrong......

Keep in mind newer cars will not have that same effect, as the stock cats will be in much better shape on newer and low mileage SC's.......

I would also like to know how those tests were made: Were they made on a new or used stock catalytic converter? Against what type of highflowing cat did they measure it against....There are many factors to consider....

Believe what you want though.....

jgscott

iTrader: (1)

Yeah look up RandomTechnologies. For CATS Flow info.

Yeah I'm on the Cl Forum. (better know as the *****ing, Trash Talking Forum LOL ! )

jgscott

iTrader: (1)

Jibby, the Center cat is one that you do want to eliminate altogether. It's the 2 cats off of the Header that are the one I am talking about. Do some searching on " Metal substrate CAT" test, Metal CAT and Random Technoligies ". One thing that you are not considering is that the CATS have to be Heated to Exhaust tempature before they preform, the Metal Substrate inside expands. That is by design.

Also did'nt you change other things in your exhaust besides just your CATS. Not good comparison on drive test if other things were changed equal.

jibbby

Jgscott - I thought you guys were talking about the main center cat....Anyway, to answer your quesion - No, I only changed out the cat at that time of testing. No other exhaust mods were changed just the cat and nothing else........That is why I can speak so boldly about my own experience with the center cat...When I blew compressed air threw both the Cats to compare, the stock cat was still hot too the touch and freshly removed from my SC400... Power gains were made on my 1992 SC400 and I see no reason why the same would not happen to other older SC's, that is why I posted......

CleanCL

i've seen a ton of cats from Random fail. i wouldn't buy their stuff. not well made in my opinion.

i thought planetsoarer tested the stock cats (under the headers), car-sound, and catco. pretty much side by side. came to the conclusion the car-sound were better.

when i do my custom setup, i'm going to measure the s&s and have the cats run as close to them as possible. i'm going to try to tuck them vertical (like stock) rather than running underneath the car. my car has over 160,000 miles, so pretty much anything is better than the stock cats at this point.