Ok, I have a Blitz supercharger, with a typoon cold air intake, and 4-2-1 OBX headers, koyo radiator, perrin hoses, and a Greddy SPII axle back.

I'm thinking about getting a cut off valve that when i remove the cap i can redirect the flow, but putting the cap back on then can run normal.

http://www.lmperformance.com/2899/20.html

My question is how benifical is a cut off exhaust for this set up. One place I want to mount is befor the cat, or the second is after the cat. I know before the cat will produce more power. The only thing i'm worried about is the CEL. Some times the sensor tells the computer to go rich or lean and i don't know if this is one of them. I don't know how the sensors react to the computer. if it is just a light then it is ok i'll reset it.



I'm just looking for comments and ideas for this. please let me know
[/url]http://www.lmperformance.com/2899/20.html

DO IT!

you will lose some tq but it mite help out the top end and let the motor get that forced air out of there. Oh I have a question for you. You have the supercharger on a 06 xa right? How was the install? does everything work like the low med high switch? I am thinking about getting the blitz my self, just want some feed back from others with the same car as me. Oh and as for the cel coming on if its before the cat. Yes it prob will on every car that I know of with a second o2 sencer after the cat all that sencer does it make sure that cat is work....

watching...personally i'd go after the cat, just in case. and i'm not sure how this works but if you cut off before the cat wouldn't you lose torque?

btw...where'd you get the obx header? far as i know that's the only 4-2-1 header available.

just install it after the cat... btw they sell electric ones that way you don't have to crawl under your car every time you want to take it off, put it on...

they also have them that use a cable like our hood release.
here in Cali they are not street legal, even to install. just don't get caught with it here. had 2 of them on my ol'GTO, real nice for upper end and real load.

Do the cutout before the cat ( since the cat is very restrictive), it defeats most of the purpose for a cutout if it is after the cat. Also go with Duck Dodgers advice and get an Electric cutout, open and close at the push of a button. You will lose torque, but the high end will make up for it.

you will lose some tq but it mite help out the top end and let the motor get that forced air out of there. Oh I have a question for you. You have the supercharger on a 06 xa right? How was the install? does everything work like the low med high switch? I am thinking about getting the blitz my self, just want some feed back from others with the same car as me. Oh and as for the cel coming on if its before the cat. Yes it prob will on every car that I know of with a second o2 sencer after the cat all that sencer does it make sure that cat is work....


The supercharger itself wasn't that hard to put in except for the manifold bolts, it is a tight sqeeze. The switch is awsome, i have power when i want it and how i want it. I still get, on average, 34 mpg.

watching...personally i'd go after the cat, just in case. and i'm not sure how this works but if you cut off before the cat wouldn't you lose torque?

btw...where'd you get the obx header? far as i know that's the only 4-2-1 header available.

I got the obx 4-2-1 header off of ebay, but monster motorworks also makes a 4-2-1 header. it's expensive. The obx is about $150 and i have not had any problems with it, i also heat wrapped it and put silicon paint on it. makes a big difference.

Do the cutout before the cat ( since the cat is very restrictive), it defeats most of the purpose for a cutout if it is after the cat. Also go with Duck Dodgers advice and get an Electric cutout, open and close at the push of a button. You will lose torque, but the high end will make up for it.

if i put it before the cat how will the sensor before the cat take it, will it tune my engine bad, mess up my air fuel ratio, etc.

okay, what do you think of this idea.

What if i put 2 of them, one before the cat, (but i move the sensor closer to the engine so maybe it won't effect the sensor, and one after the cat.)
The purpose behind that , depends on the situation. before the cat for total performance for on track racing, and after the cat for a little performance on the street(if i don't get caught)

As for the lose in low end torque, with the supercharger it already has alot of it expecially with the 4-2-1 header. So maybe it will make up with the high end power that i need.

It seems when drag racing, i have a whole lot of torque but when i get down half way of the track i just don't have very much.

Do the cutout before the cat ( since the cat is very restrictive), it defeats most of the purpose for a cutout if it is after the cat. Also go with Duck Dodgers advice and get an Electric cutout, open and close at the push of a button. You will lose torque, but the high end will make up for it.

if i put it before the cat how will the sensor before the cat take it, will it tune my engine bad, mess up my air fuel ratio, etc.

That is a good point.. But the O2 sensor before the cat is in charge of fuel trims ( reading if your rich or lean.. The 2nd O2 reads if the cat is doing its job properly.. So the cut out would need to be before the cat and after the 1st ( primary) O2..

Do the cutout before the cat ( since the cat is very restrictive), it defeats most of the purpose for a cutout if it is after the cat. Also go with Duck Dodgers advice and get an Electric cutout, open and close at the push of a button. You will lose torque, but the high end will make up for it.

if i put it before the cat how will the sensor before the cat take it, will it tune my engine bad, mess up my air fuel ratio, etc.

That is a good point.. But the O2 sensor before the cat is in charge of fuel trims ( reading if your rich or lean.. The 2nd O2 reads if the cat is doing its job properly.. So the cut out would need to be before the cat and after the 1st ( primary) O2..

so what if i move the sensor so it is either on the beginning of the cut out "y" or towards the engine more. to you think it will read the same?

okay, what do you think of this idea.

What if i put 2 of them, one before the cat, (but i move the sensor closer to the engine so maybe it won't effect the sensor, and one after the cat.)
The purpose behind that , depends on the situation. before the cat for total performance for on track racing, and after the cat for a little performance on the street(if i don't get caught)

As for the lose in low end torque, with the supercharger it already has alot of it expecially with the 4-2-1 header. So maybe it will make up with the high end power that i need.

It seems when drag racing, i have a whole lot of torque but when i get down half way of the track i just don't have very much.

It should help your problem with no top there is no doubt in my mind it wont. May not do a huge improvement but anything helps right? as for the one after the cat and one before the cat. I personally would just do the one before the cat. as along as the o2 sencer is not right at the cut out then it should be fine if its right before where the cut out is welded up than you should be good. If you want to move it closer to the motor you can wont hurt anything.

thank you, i just about know what i'm going to do, put it before the cat and move the sensor more to the engine. i'll let everybody know how it comes out. if you have any comments or suggestions let me know please.

The O2 sensors work on the heat produced, moving it closer to the engine it will show a different reading ( read out of spec).

having a cut out after the first O2 and before the second O2 the ECU will read a fault ( read CEL) again it will out of slec possibly throwing you into limp mode.

and believe it or not, our cats flow pretty well.

good luck, let us know how it works for you.

pardon my spelling errors and such as im a little toasted. but cats are the most restrictive part of the exhaust, if your going to put the cut out after the cat you may as well not get one. there are ways to bypass the 2nd o2 idk if for the xb but ive done it on an 04 wrx, and as stated many times, get an electronic one. you will be suprized at how little to no exhaust noise increase there will be. the top end power will be substancially differant. my old civic had an open downpipe (equivilant to cutout before cat) and when i put a cat, and full exhaust (apexi n1) to sell the car, there was a substancially noticable power decrease, and increased spool time, though this was with a turbo not blower.

best of luck!

pardon my spelling errors and such as im a little toasted. but cats are the most restrictive part of the exhaust, if your going to put the cut out after the cat you may as well not get one. there are ways to bypass the 2nd o2 idk if for the xb but ive done it on an 04 wrx, and as stated many times, get an electronic one. you will be suprized at how little to no exhaust noise increase there will be. the top end power will be substancially differant. my old civic had an open downpipe (equivilant to cutout before cat) and when i put a cat, and full exhaust (apexi n1) to sell the car, there was a substancially noticable power decrease, and increased spool time, though this was with a turbo not blower.

best of luck!


for the xa, which way works to bypass the 2nd o2 sensor. I've heard of alot of ways but not one that somebody has tryied and worked. please let me know if you know of a way it will work on an xa. i had a 05 sti and i bypassed it using one way, but i also used that same way on an 04 sunfire and it didn't work. So some ways work on some cars and some don't, please let me know which way will work on an xa

http://www.o2sensorsimulator.com/