front cat delete, will it burn the rear cat?
 

okay so people who has went with the headers mod. as in obx, mvp, etc for the mkiv supra. or just know much more about cats and exhuast systems.

if you delete the front cat, aka front three way catalytic converter [right side in the image provided] will it burn the rear three way catalytic converter [left in the same image provided]?
http://i304.photobucket.com/albums/n...e/41986568.gif



in other words, im replacing the parts: 1,2,3,4, and 5, for my headers. i will be keeping number 6. so if that happens, will i burn out the rear cat on the 6 pipe?
http://i304.photobucket.com/albums/n...ce/8904163.gif

idea of the cat deletion.
http://i304.photobucket.com/albums/n...sidebyside.jpg
sourced from supraforums* but the manifold on the left is for a sc300

now i also heard that little flex coil [right next to the arrow of number 5] on the OEM exhuast manifold also acts as a pre cat? is that true?
TIA

That's how my cars has been for over 10k miles and who knows for how long before that... no problems with the rear cat. I did replace it not too long ago though because bigger piping.
I even took my car to go get smoged that way and it passed. No issues at all... all my carbon levels were in range and didn't do anything to "help" it pass the system.

so while you had just the aftermarket headers and stock "6" pipe, you didnt burn the rear cat, and still passed smog? how did you pass visual?

No burning of the cat... I honestly took it in and just played dumb. Did you know these are after market? I was like I don't think so I just got the car not too long ago.

wow haha i should try that. :p see what happens. but hmm okay, seems like im just gonna gonna pull teh trigger on this one. and if i burn my cat, im gonna blame you bro! haha jk :thumbup: ill just get a replacement cat/pipe of 6 from aliga or someplace.

and what size piping did you replace it with? did you get a hi-flow cat? you still pass smog?

TLDriver, what kind of cat did you get?

Well I had the stock cat when I went to go get it smoged.
I think it was a flow master for an OBD1 for whatever reason my O2 sensor was in front of the cat.( My other cars have had the O2 sensor behind the cat) No problems yet.

that flex pipe on the header is for heat expansion it is not a pre cat or anything like that of any sort.

did you loose bottom end power my second cat is removed and i wana do a header, do you know if the ls 400 mass air sensor will fit the sc300 straight bolt on.

that is definitely not a proper sentence and a very weird way of asking a question.

i think your are asking/stating 3 different things. write it properly if you want an answer.

i think he meant [and im sure you know as well, but your helping him fix his english]:

did you loose bottom end power?
my second cat is removed and i wanna do a header...
do you know if the ls 400 mass air sensor will fit the sc300 straight bolt on?

...lol anyways im sure you asking tldriver, as hes the only on in this thread who has done this. but there are others who did so aswell. so i cant answer it untill i install mines.
and why would you want to use a 1UZ MAF? even if you were turbo below 400hp... i dont think you need to?

1 - With just headers, no. With a 3" exhaust - Yes. i noticed a bit less low end tq when i got my Superdragger + 3" HKS Mid Pipe. But mid/high end tq is improved.

2 - If you get headers you will lose the precat, and thus have NO cats at all.

3 - IIRC (i could be wrong) the LS4 MAF is not a direct bolt on (minor modifications + Tuning necessary) , but it is not needed until you get up there in HP, and even then a standalone that removes the MAF system is much better, IMO

mafs are not a bad thing and its actually not the best if the standalone uses map only. for a racing engine its fine but for a more streetable engine its best to have both and have the map work more of a air density compensation tool. this is very helpful for cars going through great temperature and/or elevation changes.

with a bigger exhasut you will always lose a bt of low end torque. if you are NA and making less then 100hp/liter you should stick with a 2.5" or 2.75". 2.75 inch piping does not actually excist but a close second is 70mm which is almost 2.75".

2.5" would be ideal though. there is no need for a 3" exhaust. an exhaust of that size does not give you anything but attention because its so goddamn loud.

I got the attention getter exhaust size :o)
I feels like it has 3 stages when picking up the low RPMS lag for days, the second 3-4.5k RPMs picks up strong, but when it passes 4.5k RPM it's just a different car. I haven't got it dyno'ed nor do I want to before going with some boost. This is with my 3" exhaust. Before the exhaust it felt stronger off the line and more of an even pull through out mid and high rpm's.

very good info on here! actually made me read up some more articles about exhuast piping and such.

but make sure you guys dont go too off topic that this thread will be locked.

i still havent been able to get my headers installed. its raining and no garage room :[