ZUKIWORLD Online | Suzuki 4x4 Editorial and Forum
ZUKIWORLD Discussion Forum => Suzuki 4x4 Forum => Topic started by: Wilnailu on December 18, 2011, 11:15:43 PM
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Can anybody tell me factually if removing the cat will decrease ex. Back pressure causing the ECM to go to full rich mode. Thanks Chris
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What vehicle? FI or carb?
If the cat is blocked it would. Could be a bad O2 sensor.
Use a pressure gauge in front of the cat and see if the reading is higher than 5-6 psi. You could do that right off the O2 sensor bung.
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Yes, in most cases the removal of the cat decreases the backpressure more than enough to cause the EGR system to think there is a failure and the ECU goes into limp mode.
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The EGR will work regardless of the back pressure of exhaust system since they are tapped into the exhaust manifold or the head. It functions via vacuum or a solenoid via the ECM. Some measure flow, some don't.
A plugged EGR passage can get plugged and it may not set a code but can make you fail smog.
Yes it may run better with no CAT and no EGR but finding the real problem is important.
What vehicle??
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If doing a custom 1.75 exhaust with calmini headers and a magnaflow trichamber exhaust... Provided you bunged the 02 sensor on an efi 1.6...in my mind it should work perfect... Right?
Sniff test doesn't matter to me, mpg does. On short trips your cat doesn't do anything but kill mpg/power.
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Sorry it is a 93 sidekick ca. Vehicle. I removed the cat because everything inside was in a million pieces rattling like crazy.But ever since it is getting only about 20 mpg instead of around 26 mpg.I've tried diff. Ignition timing,the jetway for the timing belt is good.
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Just removing the Cat can make the car run wrong, hence the bad mileage. The motor is tuned for the back pressure AND correct reading of the 02 sensor.
Have you pulled any codes yet?? You could just throw a cheap cat on it.
If you remove the Cat in a Ca vehicle there is a $5000 for each item removed if caught, and they do roadside checks sometimes. Beware.
In Yuba DOT is stopping Diesel Pickups and looking for the car and other items removed. They tow and tag the vehicle not allowing it to be driven until repairs are made.
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The state only wants something of value,not something that is going to cost them to get rid of.I think I'm pretty safe on that part. Thanks for the info.
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I am SOOOOO.... Glad I DON"T LIVE IN CALIFORNIA !!!!!!
I am starting to believe the Old Joke.....
"The World is NOT LEVEL !!!! It's on a Slant, and ALL the Fruits & Nuts rolled to California!!"
Not that we don't have our share of Crazies in Wisconsin....Gov. Scott Walker/Dallmer/Ed Gean.. All fed/feed on humans !!
Yes I am for clean air/water/land......
But we all can't BUILD a plastic bubble to protect us ALL from the practical world.
We have Nuke Power, Battery Cars......But NOWHERE to get rid of the Radioactive Waste & Spent Batteries !!!
Carbon Based Particulates are heavier than air, & will settle out of the atmosphere, it is just that the west coast
of California has a Mountain Range to the East that "Concentrates" the Air there.
Neither leave good choices.
My 2 bits......CAPT
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The Suzuki engines do not run well without the cat or EGR system functioning when running the stock ECU, for it too function correctly an entirely new engine management system will be required, but dont expect to pass any emissions test, LOL
I swapped over to a heavy metal spun cat on my Sidekick, in NY if the vehicle has 80K miles or is older than 8 years the stock exhaust system does not have to be installed, but a functioning cat and exhaust is required and must pass a sniffer/dyno test as well as have a functioning OBDI or OBDII system(unless the car didnt have any(real old)).
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We only need a smog check every two years and there are several counties where they are not required unless transferring ownership.
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Sorry it is a 93 sidekick ca. Vehicle. I removed the cat because everything inside was in a million pieces rattling like crazy.But ever since it is getting only about 20 mpg instead of around 26 mpg.I've tried diff. Ignition timing,the jetway for the timing belt is good.
Is the Check Engine Light on?
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Sorry it is a 93 sidekick ca. Vehicle. I removed the cat because everything inside was in a million pieces rattling like crazy.But ever since it is getting only about 20 mpg instead of around 26 mpg.I've tried diff. Ignition timing,the jetway for the timing belt is good.
Is the Check Engine Light on?
no the CEL is not on
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If the CEL comes on at key on and then goes out again then the ECU doesn't know that the cat is not there and the fuelling won't be affected.
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Just got back from Oregon,going through the syskhous and flatland averaged 26.1 mpg,very happy
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If the CEL comes on at key on and then goes out again then the ECU doesn't know that the cat is not there and the fuelling won't be affected.
OBDI ECU's have no way to determine the cats condition, this was addressed with OBDII when they added the secondary o2 sensor. The secondary heated o2 sensors purpose is to read the temp of the exhaust gases AFTER the cat, the ECU then compares that reading to the primary sensor reading to verify a temp drop indicating the cat is operating and catalizing unburned fuel and byproducts.
A simple work around for those driving strictly offroad and wish to remove the cat while not getting a CEL, is to remove the secondary sensor from direct contact with the exhaust stream. This is accomplished by creating a standoff, go to any autoparts store like Auto-Zone and look for a set of sparkplug defoulers(blister pack with 2 defoulers), take one of the defoulers and drill out the restricted end so that the o2 sensor will fit without touching the sides on the defouler, thread the second unmolested defouler on and then install in the secondaries bung.
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The problem is nothing to do with the condition of the cat but whether enough back pressure remains for the EGR to still function, the ECU looks for a change in intake manifold pressure when the EGR opens. The ECU will default to back up settings if it thinks that the EGR is faulty, that is what the earlier poster was alluding to. If the CEL is not on then the ECU won't be altering the fuelling.
On an OBD2 ECU the second O2 sensor checks for a change in the oxygen level not the temperature, the sensors are heated with a PTC element that regulates its own temperature.
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But the sensors determine the o2 levels by changing resistance within the sensor material due to temperature(reaction to o2 in exhaust), I have used this mod succesfully many, many times on OBDII vehicles. By standing it off but not removing it entirely from the exhaust flow it tricks the secondary sensor into outputting a voltage that is within the range expected by the ECU with a working cat. In fact, there are even companies that are making them all fancy dancy specially machined, but charge a heck of a lot more than the defoulers and they both do the same job.
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But the sensors determine the o2 levels by changing resistance within the sensor material due to temperature(reaction to o2 in exhaust).
No they don't, they use a Nernst cell which is an electrochemical cell which generates a voltage due to the absorption of oxygen atoms, the resistance doesn't change. Spacing the second sensor is supposed to move the sensor out of the exhaust stream and shield it from the exhaust gasses.
None of which is relevant because no one was talking about the ECU detecting the removal of the cat ??? ??? only the possible non-functioning of the EGR.
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But the sensors determine the o2 levels by changing resistance within the sensor material due to temperature(reaction to o2 in exhaust).
No they don't, they use a Nernst cell which is an electrochemical cell which generates a voltage due to the absorption of oxygen atoms, the resistance doesn't change. Spacing the second sensor is supposed to move the sensor out of the exhaust stream and shield it from the exhaust gasses.
None of which is relevant because no one was talking about the ECU detecting the removal of the cat ??? ??? only the possible non-functioning of the EGR.
You are correct, I dont know why I had that in my noggin,,,messing with those darn snomobiles too much probably, LOL...
And if the rest of the exhaust is stock the removal of the cat shouldnt cause an issue with the EGR