helloooo,
A Friend Of Mine Has A An Old Car That Doesn’t Have A Catalytic Converter . It Is Petrol And Automatic..
it Doesn’t Smoke But It Is Taking In More Fuel Than Usual..
He Said He Bought The Car Without The Converter & He’s Been Driving The Car Without The Converter In It With The Same Fuel Symptoms For A Very Long Time ..
He Complained To Me Recently That All The Local Mechanics Shop He’s Visited Are Saying It Is Because Of The Absence Of The Converter ..
He Wants To Know If Any Car Without The Converter Can consumes More Fuel..
he Wants To Know If The Catalytic Converter Is Responsible For That..??
He Is Asking For Your Opinion Too Guys..
Please follow the instructions. Always post details. Thank you.
It’s An Automatic Transmission, 1999 model , odometer offf..
The CAT itself does not affect the mpg, but the data from oxygen sensors could easily do that.
Hello Yaser,
One Quick Question, Does Old Cars Have These Oxygen Sensors..?
Where Is This Sensor Usually Located..?
Thanks
The cat does affect the mpg.
For example, the ECU deliberately spends extra amounts of fuel on heating the cat up to its working temperature after startup. Especially in winter time this becomes noticeable.
Catalytic converters actually make the cars consume a bit more fuel. You would have some kind of other problem as I have tons of customers in Tennessee that have no cats and they work perfectly fine
Hello Scott..
Can You Outline These Problems Just To Be Aware When I Encounter One..?
Thanks
If someone just throws away the catalytic converter, not taking time and effort to take specific measures in order to fool the ECU into thinking that the converter is still there and working fine, the car will definitely consume more fuel. Sometimes much more fuel than before, or than an equal car consumes which never had a cat and was factory-programmed to not have one. This has reasons, this is correct behavior (from the engineering standpoint), but this can be easily fixed.
Hi , How Can It Be Fixed ..?
There are different ways:
1) The imo best way is, you contact some guy who professionally does chip-tuning. He might be able to get hold of a no-catalytic-converter firmware revision for your ECU, which may or may not exist in the wide world, depending on whether or not the car has been sold on any markets on Earth without catalytic converters. If you are lucky, and such a revision does exist for your car, he will just flash your ECU with this no-cat revision, and voila. This way you will be getting the best fuel economy with virtually no downsides.
BUT if such a separate car-manufacturer-made firmware revision does not exist at all for your specific car, the chiptuner guy will probably suggest that he can just disable the rear O2 sensor(s) in your existing firmware, or modify your existing ECU firmware in some way in order to force your car into not generating any cat-absence-related codes. DO NOT agree to that suggestion: it is a waste of money: in the best-case scenario, the result will be sending your ECU forever into that very limp mode with higher fuel consumprion and lesser power which you are already "enjoying" due to the missing cat. While in the worst case scenario it will mess up your whole firmware, cause the interdependencies within this software are much more complex than chiptuners are willing to tell their customers, and the risk that he will make things worse is significant - Ive been there.
2) Your next option is to get an electronic O2 sensor defouler. They are specialized electronic chips with wires which have to be added into the electrical cirquit sequentially with your rear (located after the can where the cat used to be) O2 sensor, and they take the electrical signals emitted by this O2 sensor (which is complaining about the cat being non-existent) and convert them in real time into a signal which the ECU interprets as "the cat is existent and working just fine"-signal. This is what Ive done, and it works just fine: increased fuel consumption went away, the engine power returned, and error codes disappeared. This option returns your car ECU into normal driving mode, and the car drives not worse and not better, than it would be performing with a new cat installed.
P.S. Scotty was right when he wrote that a car with a cat (or which used to have a cat) always consumes more fuel than a car which never had one. This is by-design, and this solution does not and is not intended to remove this slight difference in fuel consumption.
3) Like 2), but you cut your rear O2 sensor off / disconnect it completely, and replace it with an electronic defowler which completely emulates the O2 sensor signal, not needing the O2 sensor for doing that. Benefits are like in option 2), plus easier connection/installation, but the downside is that those chips have no way of knowing all the details of what the car/ecu are doing in a specific moment, hence sometimes the ECU will be guessing that you are trying to fool it, and may still generate O2 sensor- and cat-related codes from time to time, sending the engine into the limp mode. These codes are easy to erase even with primitive bluetooth OBD2-scanners, and do not occur too often, so I know people who are driving years this way.
4) You screw your rear O2 sensor out, than screw in a mechanical defouler (which is basically a miniature catalytic converter), and then screw your O2 sensor into that defouler. Never tried this option, but theoretically it might work. Am not sure, how good / trustworthy those defowlers are in emulating the big cat´s behaviour - my guess would be, that sometimes, like with option 3), error messages might still appear in this case, but it is just a guess.
Hello,
Thanks So Much For This Vital Information.. I Will Pass This On To A Professional Mechanic And Will Also Outline The Outcome Here
Regards CrakkDj