intake and exhaust
04-07-13, 10:43 PM
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intake and exhaust
Hi guys..names Jeremiah... I'm new on here and i got a couple questions. I just bought my first Lexus got out of the Honda world and so im new to this. I just bought a Lexus sc400. Love my new well new to me car. But i have a couple issues first of all I had some true duel exhaust pipes installed but i wanted to delete my cats. I got told i couldn't because the o2 sensors were attached behind them....I don't know why I cant so is there anything i can do to still delete them? if so what can I do? Second i tried adding a cold air intake but after about 10 mph my car kept wanting to die ...i left all the sensors on just took the air box off and added a sensor adapter plate and a mushroom head filter...Guess my question is if i can add a cold air if so what all do i need to do to get it to work right....?
Last edited by juice1983; 04-07-13 at 11:22 PM.
04-08-13, 12:05 PM
#2
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Replacing the air box with a cone filter (or any other type of open filter) is NOT going to help anything. The factory intake system is a cold air intake. A cone filter will make it a warm air intake, which will decrease power, probably significantly (you may gain a slight bit in gas mileage, but it will almost certainly be negligible, while the power loss will be more severe). The fault you have encountered is likely due to how the aftermarket filter is disrupting airflow through the MAF sensor (assuming you have not damaged anything with the modifications, or left something unplugged/loose). Put the stock air-box back on. if you want more power, look into a "BFI" (search).
A "true" dual exhaust is also not generally a wise idea. In almost all cases, this will result in a loss of power--there is a reason virtually all factory systems combine at some point, even though it typically adds cost and complexity to the system. Do some searching on the internet regarding x-pipes and h-pipes for more information.
There are some gains from modifying the exhaust, but a "true dual" exhaust is not the best idea. Please be aware that simply slapping larger diameter pipes on there will typically result in a loss of torque. Do some searching on the forum to see what others have done, and what the outcomes have been.
You can remove the catalytic converters, but I believe the gain is typically minimal, and it will result in failing an emissions inspection, if you have those (note: I'm not sure what the gain is with the 1UZ, but on most cars, it's not worth breaking the law--even if your state does not have emissions requirements for your vehicle, tampering with (removing or disabling) emissions devices is a federal offense). Typically there are only post-cat O2 sensors on OBD2 vehicles ('96 and newer). I do not know about SC400s for sure, but typically OBD1 vehicles only have O2 sensors before the cats, as those are the only ones used for mixture control (the post-cat O2 sensors on OBD2 cars are only there to test the cats: to turn on the check engine light if they are not performing correctly).
There are some worthwhile modifications for these cars, but slapping on an aftermarket filter and big muffler, like many people do with Hondas, is not the best route: do some reading on the forums to plan modifications that will actually be worthwhile.
A "true" dual exhaust is also not generally a wise idea. In almost all cases, this will result in a loss of power--there is a reason virtually all factory systems combine at some point, even though it typically adds cost and complexity to the system. Do some searching on the internet regarding x-pipes and h-pipes for more information.
There are some gains from modifying the exhaust, but a "true dual" exhaust is not the best idea. Please be aware that simply slapping larger diameter pipes on there will typically result in a loss of torque. Do some searching on the forum to see what others have done, and what the outcomes have been.
You can remove the catalytic converters, but I believe the gain is typically minimal, and it will result in failing an emissions inspection, if you have those (note: I'm not sure what the gain is with the 1UZ, but on most cars, it's not worth breaking the law--even if your state does not have emissions requirements for your vehicle, tampering with (removing or disabling) emissions devices is a federal offense). Typically there are only post-cat O2 sensors on OBD2 vehicles ('96 and newer). I do not know about SC400s for sure, but typically OBD1 vehicles only have O2 sensors before the cats, as those are the only ones used for mixture control (the post-cat O2 sensors on OBD2 cars are only there to test the cats: to turn on the check engine light if they are not performing correctly).
There are some worthwhile modifications for these cars, but slapping on an aftermarket filter and big muffler, like many people do with Hondas, is not the best route: do some reading on the forums to plan modifications that will actually be worthwhile.
04-08-13, 12:31 PM
#3
Replacing the air box with a cone filter (or any other type of open filter) is NOT going to help anything. The factory intake system is a cold air intake. A cone filter will make it a warm air intake, which will decrease power, probably significantly (you may gain a slight bit in gas mileage, but it will almost certainly be negligible, while the power loss will be more severe). The fault you have encountered is likely due to how the aftermarket filter is disrupting airflow through the MAF sensor (assuming you have not damaged anything with the modifications, or left something unplugged/loose). Put the stock air-box back on. if you want more power, look into a "BFI" (search).
A "true" dual exhaust is also not generally a wise idea. In almost all cases, this will result in a loss of power--there is a reason virtually all factory systems combine at some point, even though it typically adds cost and complexity to the system. Do some searching on the internet regarding x-pipes and h-pipes for more information.
There are some gains from modifying the exhaust, but a "true dual" exhaust is not the best idea. Please be aware that simply slapping larger diameter pipes on there will typically result in a loss of torque. Do some searching on the forum to see what others have done, and what the outcomes have been.
You can remove the catalytic converters, but I believe the gain is typically minimal, and it will result in failing an emissions inspection, if you have those (note: I'm not sure what the gain is with the 1UZ, but on most cars, it's not worth breaking the law--even if your state does not have emissions requirements for your vehicle, tampering with (removing or disabling) emissions devices is a federal offense). Typically there are only post-cat O2 sensors on OBD2 vehicles ('96 and newer). I do not know about SC400s for sure, but typically OBD1 vehicles only have O2 sensors before the cats, as those are the only ones used for mixture control (the post-cat O2 sensors on OBD2 cars are only there to test the cats: to turn on the check engine light if they are not performing correctly).
There are some worthwhile modifications for these cars, but slapping on an aftermarket filter and big muffler, like many people do with Hondas, is not the best route: do some reading on the forums to plan modifications that will actually be worthwhile.
A "true" dual exhaust is also not generally a wise idea. In almost all cases, this will result in a loss of power--there is a reason virtually all factory systems combine at some point, even though it typically adds cost and complexity to the system. Do some searching on the internet regarding x-pipes and h-pipes for more information.
There are some gains from modifying the exhaust, but a "true dual" exhaust is not the best idea. Please be aware that simply slapping larger diameter pipes on there will typically result in a loss of torque. Do some searching on the forum to see what others have done, and what the outcomes have been.
You can remove the catalytic converters, but I believe the gain is typically minimal, and it will result in failing an emissions inspection, if you have those (note: I'm not sure what the gain is with the 1UZ, but on most cars, it's not worth breaking the law--even if your state does not have emissions requirements for your vehicle, tampering with (removing or disabling) emissions devices is a federal offense). Typically there are only post-cat O2 sensors on OBD2 vehicles ('96 and newer). I do not know about SC400s for sure, but typically OBD1 vehicles only have O2 sensors before the cats, as those are the only ones used for mixture control (the post-cat O2 sensors on OBD2 cars are only there to test the cats: to turn on the check engine light if they are not performing correctly).
There are some worthwhile modifications for these cars, but slapping on an aftermarket filter and big muffler, like many people do with Hondas, is not the best route: do some reading on the forums to plan modifications that will actually be worthwhile.
You can make your own BFI intake which has been dyno proven to be the best intake for the SC400. Better than all the pod filter and expensive crap. The mod for your intake is free! If you don't feel like fabbing up the BFI intake yourself just type in "BFI SC400", there's a seller who sells a pre-cut kit. I bought the ebay kit, it's expensive but everything fit like a glove.
Planet Soarer research on BFI intake
http://planetsoarer.com/BFI3/bfi3.htm
There's other pages with dyno numbers and the BFI comes out on top.
For exhaust, I wouldn't touch it unless you were planning on putting headers. The SC400 exhaust is very well designed from factory. The stock cats actually flow pretty well and are decently sized. Anything you do without careful considering you will probably lose power. Personally I'm not touching my exhaust until' I'm ready to drop the money on headers and the rest of the work involved.
Good choice on the SC
Read up on mods here before you start doing stuff to the car. Everything has pretty much been done before and you can learn from people's mistakes and successes.
04-08-13, 07:24 PM
#4
you can install o2 sensor defoulers with the o2 sensors that follow the location of the cats. The CEL triggers because the upstream (first) o2 sensors read a certain amount, and then the downstream (second/after-the-cat) o2 sensors have the same reading. Upstream o2's are raw exhaust fumes straight out of the head, the downstream o2's are positioned after the cat and are supposed to read/measure a different reading in the exhaust fumes, due to the cat converting the fumes.
o2 sensor defoulers 'extend' or 'space' the o2 sensors out, so that they may read/measure 'less' of the exhaust stream, therefore tricking them into thinking that the fumes had indeed passed through a catalytic converter.
o2 sensor defoulers can be used with upstream o2 sensors as well with the install of headers, to prevent a CEL from triggering from the upstream o2's.
As far as 'true dual' exhaust, that only sounds nice, not even the muscle car guys do that. X pipes do the trick for a V8 dual exhaust.
o2 sensor defoulers 'extend' or 'space' the o2 sensors out, so that they may read/measure 'less' of the exhaust stream, therefore tricking them into thinking that the fumes had indeed passed through a catalytic converter.
o2 sensor defoulers can be used with upstream o2 sensors as well with the install of headers, to prevent a CEL from triggering from the upstream o2's.
As far as 'true dual' exhaust, that only sounds nice, not even the muscle car guys do that. X pipes do the trick for a V8 dual exhaust.
04-12-13, 12:32 AM
#5
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you can install o2 sensor defoulers with the o2 sensors that follow the location of the cats. The CEL triggers because the upstream (first) o2 sensors read a certain amount, and then the downstream (second/after-the-cat) o2 sensors have the same reading. Upstream o2's are raw exhaust fumes straight out of the head, the downstream o2's are positioned after the cat and are supposed to read/measure a different reading in the exhaust fumes, due to the cat converting the fumes.
o2 sensor defoulers 'extend' or 'space' the o2 sensors out, so that they may read/measure 'less' of the exhaust stream, therefore tricking them into thinking that the fumes had indeed passed through a catalytic converter.
o2 sensor defoulers can be used with upstream o2 sensors as well with the install of headers, to prevent a CEL from triggering from the upstream o2's.
As far as 'true dual' exhaust, that only sounds nice, not even the muscle car guys do that. X pipes do the trick for a V8 dual exhaust.
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93 5spd Graphite Metallic
thanks man much appreciated ordered the o2 sensor spacer and magnaflow x pipe cant wait to install and hear the diffidence
o2 sensor defoulers 'extend' or 'space' the o2 sensors out, so that they may read/measure 'less' of the exhaust stream, therefore tricking them into thinking that the fumes had indeed passed through a catalytic converter.
o2 sensor defoulers can be used with upstream o2 sensors as well with the install of headers, to prevent a CEL from triggering from the upstream o2's.
As far as 'true dual' exhaust, that only sounds nice, not even the muscle car guys do that. X pipes do the trick for a V8 dual exhaust.
__________________
93 5spd Graphite Metallic
thanks man much appreciated ordered the o2 sensor spacer and magnaflow x pipe cant wait to install and hear the diffidence
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