I use the van only for fun. The cabin is well isolated. I am not afraid of loud exhaust sound. If too loud I make it quieter. But I want to hear the engine rumbling. I don't want to spend on a full system with two tubes. I thought I remove the cat, and A. put here an empty tube B. put there a universal can with perforated inner tube or C. I mount a more free version of cat. I leave the 3rd O2 sensor which is behind the cat at its place, but do not know how the system will react. The gases will flow more free. Theoretically that should create some additional HP. But is the backpressure enough without cat? Can the ECM give more fuel to the mixture? Can the system handle such a change? Or the mixture will be too lean? Or the ECM will go mad? Will the van consume more or less? These are the questions.

Thank you for all idea in advance!

 

From experience removing the cat without changing the "Tune" will cause you issues, including legal, across the board.

If you want to increase mileage and HP and stay legal the best bang for the $$$ is to put on a muffler that has the sound you want.

From my experience MagnaFlow Cats flow great and keep you legal without breaking the bank. They are the 4th different set I have had on my Mustang, sound great and pass the sniff test with near Zero emissions.

 

The van runs a closed loop feedback system. The catalytic converter needs to be there or the computer will stop using the o2 sensor to measure the air/fuel ratio and start guessing. It will always eat more fuel, since the 'blind' Mass Air engine strategy runs rich to protect itself.

 

Where does the computer know if there is a cat or not? The last O2 unit measures values which are out of a certain area? And then the computer presumes there is no cat? On the other hand the statement you made makes me think: if the system thinks there is no cat, then it riches the mixture because the mixture would be too lean which could damage the components...that moves me to make the conclusion the system can't optimize the mixture if there is no cat, otherwise there would not be that logical step described above. So to remove the cat not a good idea with the basic computer. What do tuners do? When they put there a high flow head + big manifold and full exhaust system. Do they use all a custom computer?

 

Well, I just noticed we are talking a 5.8L van. The EEC-IV doesn't actually monitor the cats at all. Newer vans (1996 and above) actually have a downstream O2 sensor. EEC-IV vans do NOT have the downstream sensor.

I would not remove cats entirely, I would replace them with high flows. The reason is, non catted vehicles smell absolutely ****ing AWFUL when running.

 

Actually it does! 3 sensors are there. One is after the cat. I do not have any problem with the smell of exhaust. Don't have old car or bike? They are all smelling. Since the distance I make is minimal pollution is not a real topic. But ok, if not possible to gain then no sense to remove of course, then also no pollution or not that much...so a high flow cat can go trough. I check the market! Thank you!

 

what year is your van? everything 96-up requires the sensor to be giving a correct reading (cat working) or it'll be in open-loop mode and run rich as was described above.
i'm not aware of any OBD1 vehicles that used the sensor after the cat, but if you have one, you need it right.

 

I gutted the cat on my 1992 E150 with 5.0 no power increase, perhaps some loss of low end power, no gain in power at all.
I put a glass pack on it and it droaned so badly that I couldn't enjoy the interstate at all. I have two identical vans. One is completely stock and all emissions stuff works perfectly and is all there. The other is gutted, no smog pump guts, egr disconnected, and the origional one runs better and idles better than the gutted one. stock one 16 mpg, gutted 15 at best.
AE

 

the idea that removing the cat will improve your performance is really only true when the cat is plugged up, but a cat in good shape flows quite freely and is almost no restriction at all

 

Thank you guys! It seems to necessary to change the whole system and to add a new injection + ignition map, if I want to get out some sound and power and that costs more than the vans value, so i forget it rather...

 

If you want better sound change out the muffler to a performance unit. Go to the auto parts store and see what they have. That will give you the biggest bank for your buck sound wise.

As well hit up eBay for engine performance parts as I have got some cool bar-goons for my Mustang there.

 

I gutted my cats after one clogged and overheated. I was told I can eliminate both since it is a non monitored system. I have dual exhaust with dyna flow mufflers which once installed a couple years ago greatly reduced the back pressure.

I am concerned if I eliminate both cats, and run a straight exhaust pipe to mufflers, what if any impact will it have on fuel scheduling, leaner, richer, DTC codes, service engine warning light, or don't worry?
I live in Tennessee so emission testing is no concern in my county.

 

Gutting or removing the cat will not cause a problem with the EMC. You must keep the O2 sensor of course but that's all you need downstream of the engine. The increase in flow will not be that much as the 5.8L is most restricted by the cast iron exhaust manifolds and not the Cat. Adding headers is the best way to open up the exhaust as that is where the bottleneck in the exhaust system is on these engines.

 

I had a '95 with 5.8 with cats intact. First put on a glass pack muffler, not much louder than stock really. When the glass pack rusted away, replaced it with just a pipe. Full exhaust system, with cats but no muffler. Sounded nice outside the van. Ran it for a couple years like that, I began to tire just a little of the drone at freeway speed.
Mine had only one O2 and it did fail eventually, can't say it was due to the lack of a muffler though, the van had over 200,000 miles at that point.