Join Our Ford Truck Forum Today

Document your Ford truck project here and inspire others! Login/Register to view the site with fewer ads.

New Catalytic converter improves running?

Ton van der Sluijs

official Lucas dealer
Hi everybody.
Today I've installed a new Cat... The CO2 values were not good according to thee yearly test.
The old one was burned empty. A big 3inch pipe was welded between cat and muffler.
There was allways a stutter on LPG in the lower rev range.
Now, with a new cat, an stainless steel 60mm pipe, the stutter is gone, she runs like hell and as smooth as silk...
Is it possible that with the empty cat the engines adjustment did miss a certain backpressure in the exhaustsystem? I'm asking this, because in between the yearly mandatory checkups I would like to replace the cat for a tube...I'm real Dutch; saving a cat is saving moneysmilieFordlogo smilieFordlogo smilieFordlogo


best regards Ton
 

73F100Shortbed

That's how we roll!
5,937
320
NJ
Your cat should last a long time as long as everything else is in good working order.
 

Ton van der Sluijs

official Lucas dealer
goodmorning Sean and Joey.

At first , thanks for your reply. Yes, I did swapped the O2 sensor as well. i've heard that on LPG a cat will last shorter due to the hotter gasses, but on the other hand, I'm driving like an old fart, nearly never above 3200revs and not faster than 60mph, so, how hot is hot? The cat from the Grand cherokee is for an 100hp, according to the sticker on the cat, but te original Ford's one, was smaller than the new one. I don't have an idea what a genuine one (two i one) cost; the one fitted now is a universal one and did cost me 183 Dollars.

an other fact was, I,ve removed the smogpump last year , and I left the tube which leaded to the exhaust after the cat and did cut the hose and left the one way valve on it's place. what did happened was, that the valve was sucked open and a roar was heard under the hood. I've allways thought that it came from the K&N airfilter, but now the tube is gone also, thetruck is as silent as before!
A Smogpump gives false CO2 readings here. I've understood, that in the USA an other way of checking the exhaust gasses is done.

best regards Ton
 

Truckin4life

Texas Chapter Leader
If you have the muffler in, then im sure that will create enough back pressure...

Was the cat gutted out or was a pipe put in its place???

Also, did you replace the o2 sensor while you were there?
 

Ton van der Sluijs

official Lucas dealer
Hi Don; thanks for replying; I appreciate that.

Yes, indeed I replaced the O2 sensor...four months ago. The cat was totally empty!!
Is it in America mandatory to show your car/truck to a garage for a general check up and on what manner do they measure the O2 and Lambavalues?
when they check it here, they put a tube in the muffler and the machine "sniffs" .. when the O2 is to high, the mixture is to rich; when there is to much unburned oxygen, the exhaustsystem leaks. that's why a smog is a useless thing.
For a good gastransport, an exhaustsystem should be as hot as possible and a smog produces water in the muffler. I coould see at my truck, that there's done not much dismantling work, but the studs from the exhaustheaders were very worn, what tells me that it was an "exhaust eater".
when I did refurbished my cilinderheads, I saw that the smogsys blew (above 2000rpm) exxentric on the valves straight in the opposite of the gasstream!! How much horsepowers would you like to loose!!

best regards Ton
 

Truckin4life

Texas Chapter Leader
In some places, the sniffer is used, and if you catalytic converter is hollowed out or is missing then you will fail the test. In all places the removal of that cat is illegal. But nobody really cares, depending on where you are though. They will do a visual inspection to see if your cats are there. Now if they are hollow or have no internals, they will never know. Actually a hollowed out cat is worse than a piece of pipe replacing that cat. A hollow cat creates alot of turbulence and can create a suprising amount of back pressure..

If the smog pump is disconnected are the lines running to the back of the heads plugged or are the holes in the back of the heads plugged?
 

Ton van der Sluijs

official Lucas dealer
Goodmorning Don.
I'm sitting on the edge of my seat, so to speak, when I read your comments!

I didn't reckoned that possibility that an empty cat could give such troubles, but indeed, an empty space give turbulence. I did welded a Y-section which blows into a single port cat from a 2500 Grand Cherokee. I've seen that such a car has less HP than mine, but I'm driving like "an old fart". I do not like fast accelerations and I try to keep the E4OD operating. (OD on above 50mph).
What also has given turbulence, is that the exit from the old cat was 54mm and the previous owner had welded a 76mm tube between cat and muffler and the inlet from the muffler is also 54mm!
the whole Smogpump is removed and the heads are plugged. The thermactor solenoids are still in use (to fool the computer) but also plugged. Same as the EGR; blinded but still working.

I've machined a new bracket and made a shaft with ballbearings to replace the smogpump. By the way, I was just on time; the smog's bearing were off!



best regards Ton
 

O'Rattlecan

Redneck Prognosticator
26,687
797
Belton, MO
Don is right about the turbulence created in a hollow catalytic converter. To get around this problem, some folks run a pipe through the hollow cat and weld the cat in place to visually pass inspection. This, however, is illegal in these States United.

Ryan
 

blacksnapon

Moderator
Staff member
I for one am unsure how your emissions system performs because of the LPG. The way you describe, it burns hotter, thus more oxygen content. That may be why your smog pump isn't needed (extra oxygen from the pump).
 

Ton van der Sluijs

official Lucas dealer
Hi blacksnapon;
You ask me how the emission work on LPG? In short? NOT! For 90% of all the cars and trucks on LPG is the APKtest (translated at best as "universial periodical checkup) (mandatory once a year) The vapouriser (or in my case injection, computeroperated) has to be choked in such a manner, that your car refuses to accelerate!! what most of the apkchecking stations are doing is, choking the lpg, doing the test, then giving the govermentsinspector a mail, that the car is okay. sometimes they get a reply directly that an inspector would like to check if the APKmaster has done his job right. After that , or when there is no second check, the garage put the lpgsystem back on a normal value.
My Ford is okay for them, when the CO2 is lower than 1,05%... the truck runs at best at 2%!

best regards to you; it's time to hit the sack here Ton
 

Truckin4life

Texas Chapter Leader
The size of the catalytic converter is not really based on how you drive, but more of how much flow the engine needs... You MIGHT see some improvement from a different cat.

But i believe your original statement was wanting to remove the cat so it wont get burned up before your next inspection. I don't see an issue in removing it, if the muffler is still present it should create enough back pressure. Your truck MAY run better with out the cat, and a straight piece of pipe run instead (this could be because the cat is a choking point for the engine) not likely but its possible...
 

Truckin4life

Texas Chapter Leader
As did mine, and with the smog system pulled anyway, i dont see a cat really helping at all. If you wanna pull it i think its safe, just re-install to pass the sniffer test.... Put some rubber covers over the threads or keep them covered in grease to keep the threads clean, so its not a constant battle to take the cat off or put it back on.
 

Ton van der Sluijs

official Lucas dealer
Goodmorning Ryan and Don,
I've not passed the test yet, because I'm waiting for new rubber pivot bushings from the arms of the front axle. (they are ordered in the USA and seems to arrive here today at the store. When I've passed the test I'm gonna weld a removable tube to replace the cat, no doubt about it. I shall bear your advice to put the cat plugged off in store in mind.

Ryan, my engine is a 351W EFI on LPG injection. This is the only way to have an EFI on LPG.

Yeah, that smog removed... what a pleasure, what a space. I'm gonna remove the carboncannister as well; it's not mandatory here (probably the garage doesn't know even what it is!

best regards Ton
 

Ford Truck Articles

Top