All I'm looking for is a little bit of knowledge and understanding here. I see so often how bad it is to remove all 4 converters on the 97-03 f150 trucks because they will throw a CEL and run bad. Now what I would like to know is the front set of sensors to my understanding control the fuel/air mixture and all that and the rear sensors are for nothing more than to tell the truck that the converters are there and working. Why do so many people say the truck will run fine with just two converters and gotts 02 mod but it will damage the motor if you remove all 4?? If the front sensors are the ones that control all the fuel and air and everything? I don't understand how removing the pre cats and having zero cats makes a difference if you have the gotts 02 mod.

 

It throws your vehicle into limp mode. I have the gotts O2 mod with zero cats and zero issues and no cel.

 

How long have you had that setup? I've had the gotts and just pre cats since the summer of 2010 and I've not had a CEL and so far as I know I'm not in limp mode and don't have any motor damage.

 

From winter 2010 to winter 2011 i ran catless with gotts mod. Then since winter 2011 had my gryphon just shut off the rear O2 sensors. No problems here or cel. Maybe a little low end torque loss tho.

 

I have no cats on my truck. Have O2 extenders for the fronts and no rear O2's. Have the rears turned off in my tune.

 

You need to be custom tuned to run catless with no worries. It will run fine without cats once tuned.

 

I've had the rear cut off with the gotts mod for about 3 years, but to go 100% catless I'd need a custom tune and not the gotts mod?

 

Technically you can go full catless without a tune with gotts mod. I did for year.
But yes to have it run perfect you need a custom tune.

 

Will it run worse than it does now with just two? It seems fine now, idk if it honestly is or not.

 

Mine ran fine. I never ran just two cats so i couldn't tell ya how that was.

 

Idk I may should just leave it how it is then with the gotts mod and just pre cats. Idk nothing about tunes or programmers and really don't have any interest in learning them or getting one.

 

So you deleted the regular cats and left the pre cats? It was suppose to be the other way around..
You could always upgrade to maggy high flow cats that have the O2 sensors that go into them. Then you probably wouldn't need a tune or gotts mod.

 

Yes I deleted the rear two cats about 3 years ago and left the pre cats on, and did the gotts mod for the rear 02 sensors.

 

I've heard that The reason why is that when the automaker designs the engine, they factor in how the cats will affect the flow, and they set up the cam accordingly. The amount of overlap, the amount of lift, the exact duration, the amount of advance, etc. If you remove the cats entirely, the engine goes into what is known as over-scavenging under various conditions, but basically what people don't realize or understand is that "backpressure" as they understand it is actually a myth. Basically the velocity of the exhaust as it exits the cylinder creates a vacuum that pulls the spent exhaust out (the piston never pushes it out) which creates room for the fresh intake charge. There is a brief period where both the intake and exhaust valves are open at the same time known as overlap. If the low pressure in the exhaust is too low during this time it will pull the fresh fuel air mixture from the intake into the exhaust. This has several obvious side effects. Firstly, thats a waste of fuel. Secondly, since that mixture contains unused oxygen, the O2 sensors detect it as a lean mixture, and the computer will add more fuel to compensate.
Thirdly, since the fuel and air that was wasted is not used to produce power, your vehicle produces less output than it otherwise would, and in all likelihood you will use more throttle to compensate, further hurting your fuel economy. And that even though the first sensors don't have a clue if your cat less or down to two cats or have the rear 02 seonsors turned off that thats not the point. All they do is report oxygen concentration. So as I pointed out earlier, when you get unburned mixture in the exhaust, the O2 sensors pick up on the extra oxygen and the computer attempts to make tuning changes based on that. But even if your vehicle ran without oxygen sensors at all, it would still run better with the stock cats on it. This would be the case until changes to the cam timing to optimize the engines performance and efficiency without cats are made. So what I'm saying is your engine is designed to run correctly with cats. You will produce less low end power because you are pulling an unburned mixture past the engine and wasting it. It has to be burned to make power. And you are wasting fuel.

If the engine had no O2 sensors it would not be harmed, since it would just waste fuel. Since it does have sensors and they will read an incorrect mixture, your truck would run even richer than it should, and long term it would damage the engine.

Your thinking this is caused by complex electronics, it has to do with the cam. The engine was designed to run with cats, and if you run without them, the engine over-scavenges.

 

The engine wasn't designed to run cats, - It was tuned to.

No such thing as "pre cats" on these trucks. The trucks have 4 catalytic converters.

The ONLY reason why you would loose torque and horse power when increasing flow is because of the tune.