*what is a bung?*

The "bung" is a machined, threaded piece of steel that the O2 sensor threads into. To install it in the headers, drill or torch a hole into the collector on the right side header and weld it into place.

*What is the real relativity of the airpump anyway?*

The air pump provides air into the exhaust stream at the cat, thus showing a leaner mixture for the tailpipe sniffer on emmisions checks. Since it is downstream of the O2 sensor, the computer doesnt see the "leaned" exhaust mixture, so it doesnt get a false reading if you remove it. The advantage to removing it (provided you are in an area where they wouldnt hassle you about it on an E check) is to remove parasitic drag from the motor. Any HP that is not being used to turn an accessory (ie air pump) is HP that can be helped to move the truck down the road! Same thing goes for the true dual setup, computer doesnt care. It looks for the mixture ratio at the O2 sensor, doesnt matter whether its from 1cyl or all 8. All 8 obviously will provide a more accurate indication to the computer as to rich/lean, but by sampling 4cyls (IE 1 header) it provides a fairly accurate signal. As for the shape of the motor, I mean not using excess oil, fouling plugs, etc.

*long-tube headers, high flow cat, and cat back exhaust?*

Duals all the way!!! What we have used is the Hedman Headers from Summit (roughly $100 or so) which are long tube, and no cat, true duals. The main problem with the long tube w/cat is getting the left bank over to the Y for the cat. If you are in an emissions check area, 1990 was the last year that you could legally modify the exhaust by running dual cats. An Exhaust shop can not remove the cat for you, but if you can get the whole thing pulled and the headers installed, you can usually find a shop to install the new pipes from the collectors back with a pair of cats, provided you supply the cats. My personal feelings on it, is if you can pull them and get away with it, do so. Keep the motor in tune, and you will still emit less pollutants than a neglected stock system will.


*O2 sensors on both sides of of a true dual system and splice into the sending unit lead so that it reads from both sensors at once?*

The problems with this is the signal voltage and resistance would be off, as the system is only designed to run one O2 sensor, even the length and resistance of the wires is accounted for on an O2 sensor. Which brings another thought. If you go with the headers, you will probably need to replace the O2 sensor with one with a longer harness. (They are available at most auto parts stores) so it will reach to the collector.

 

BTW, looked at the pic under your name.... do you ride?

1979 FXE, 98" Stroker, Dynoed 100Hp
1984 FLHP 80" Stocker

 

Couldn't he just go ahead and plug in an eliminator in place of the O2 sensor. Maybe they don't make them for the type of O2 sensor these have (I'd think that a 302 O2 sensor would be the same F150-to-Cougar). Plug that in so that it returns a good reading all the time, and you can put out all the emissions you want.

So there is only one O2 sensor behind the cat's?

 

there is only one O2 in the system and it's before the cats (in the y-pipe) I have longtube headers into true duals, k&n, disconnected air pump, and have no troubles with my truck whatsoever, and yes, that was before I put the chip in. If you do a sensor test, it'll come back with a code saying the air pump isn't working, but it's never turned on the check engine light. I just rebuilt my engine and put a cam in it, but don't have it back in my truck yet so I don't know how the speed density will handle that but i'll find out in about 2 weeks (have to pay my motor off before the school will let me reinstall it) It's a comp cam #35-349-8 which comp says shouldn't affect the computer.

 

So the truck doesn't even give an (Earmuffs) whether you have cats or not.

The state does though lol.

 

Right direction, wrong reasoning. The air helps the catalytic converter to work better, and that is what reduces the emissions at the tail pipe, not dilution.

No. O2 sensor eliminators is for OBD-II where there is a sensor after the cat. The computer needs the O2 sensor to run correctly. I don't believe all that was said about the length of the wires being factored in by any means. The computer gets a voltage from the O2 sensor between 0 and 1 volt; 0 being lean and 1 being rich. You won't be able to combine two into one because you will get an incorrect voltage reading.

That should only happen if you unplug the tad and tab solonoids. It won't affect how the computer runs the engine though, and it won't turn on the CEL.

Even a neglegted system will be cleaner than a system without cats. A properly tuned motor with cats will emit far less than a system without cats. Any good aftermarket cat will take virtually no power away from the engine, so why not run them? You'd be doing your part for cleaner air. It's also illegal to run without cats, no matter if they check or not; it's a federal law.

 

I beg to differ with you on the air pump, altho it will help in the cat's reduction of emissions, the other reason IS to provide a source of air into the exhaust, thereby showing lower emissions at the tailpipe, as for the length of the wires, the computer looks at not just voltage, but also resistance, by changing the length of the wires the resistance changes on what the computer sees. Try splicing a set of wires into an O2 sensor and watch the check engine light just happily glow away. As for the tailpipe emissions on a system without a cat, my comment was in comparision with a motor with full emission controls that has not been properly maintained. The motor without cats WILL be cleaner (provided it is in proper tune and well maintaned) than the neglected emmisions compliant vehicle EVERY time. Also, my preferance is to run a true dual w/dual cats, that being the case, it is not always feasible, and 1990 and earlier are the only vehicles that were legally allowed to be modified that way

 

hey, Breeze, I ride. It's a hardtail with a modified 96 ci S&S - makes about 112 HP, 93 at the rear wheel (where it counts)

What's cooler is that my wife rides a custom built Softtail with a tricked-out polished 113 ci S&S that makes about 101 HP at the rear wheel - has a hydro-glide front-end, fat tires front and back, slammed to the ground, 14" apes, just old school cool, and she'll throw her leg over it and drive it anywhere.

 

The primary goal of air injection is to provide oxygen to oxidize various gasses in the exhaust. The smog pump doesn't pump air into the exhaust all the time either. The computer can dump the air straight back into the atmosphere at various times, if it was to dilute the exhaust, it would pump it in there all the time. The computer only sees the voltage coming from the O2 sensor. There is not enough resistance in the wires to make any difference what so ever. If you just short the wires to and from the computer, yes you will get an engine light. I still think even a neglected vehicle with a functioning emissions system will be cleaner than a vehicle without cats. I'm not saying you should run factory exhaust by any means. When I can afford a new engine, I'm planning on running true duals with a cat on each pipe. I realize that most things that we do on our trucks, exhaust, headers, etc. actually helps the engine run better and probably will lower emissions. It definitely doesn't hurt anything to run a cat. Isn't it still illegal for a shop to take off a factory single exhaust in favor of a dual?

 

The performance "high-flow" cat's don't suck much horespower? If they're not going to restrict it too much I might run cats...otherwise bye...

 

Grandaddys 66, definately way cool, you might check out THIS site kinda the same as here, but for harleys instead

EPNC, the point being made about the air pump is the parasitic drag it has on the system. Also remember there were EFI vehicles WITHOUT an airpump, as they didnt need the extra assist in providing air into the cat to help show a cleaner burn at the tailpipe. As for the neglected with cat vs. well-tuned without, I have watched both being sniffed at the pipe, and the neglected was the worst every time. The key to the legalities of the duals w/cats is it has to be a 90 or earlier. In 1990 you could still change the exhaust to duals PROVIDED you kept the emissions controls systems (ie install dual cats). Technically it is not allowed to be done today, BUT a vehicle that was modified before (**wink**) they changed the law is still allowed to run that way and can be legally repaired. Personally, I like the sound of a dual exhaust with dual cats and no mufflers. Very similar to the sound of a set of turbo mufflers

Saurian, see the tail end of my reply to EPNC, and no the cats dont suck power, the airpump does tho, as a parasitic drag on the motor. The main reason you see people bypassing them is that when they run duals, they cant find a good place to re-install a pair of cats

 

I definitely agree with that, it was just how it worked that I was talkin about. Thanks for clearing up the laws about duals...I didn't know all that. You can still make a truck run clean without the smog pump - I know someone that passes emissions just fine with a 351 in place of a 300 and running no smog pump. He does run cats and true duals as well. This guy also said the smog pump was pretty stiff to turn, and his best guess was that it took about 5 hp to run it.

 

OK, so on to brass tacks......(by the way, you guys are AWESOME!!! Thanks for posting on this thread - I LOVE this forum! It's like having 50 years of experience right there in the shop. Grandaddy would be proud, God rest his soul!!) Anyway...........

I have a 1989 F-150 ext cab 4X4 with a 5.8L engine. In the long run, I am going to build a 404 ci torque monster. Natch.
In the short go, I can install a K&N filter, install long tube headers with a bung for the O2 sensor on the right hand bank, run true duals with dual high flow cats and no mufflers, bypass the smog pump with a shorter serpentine belt (still need that part#) and put in a better ignition, better wires, and better plugs ALL without spooking the EEC-IV computer and just setting off a Christmas tree of CELs?

Me likes

 

Yep yep and yep. As for the belt #, I am going to the shop in about 15 min, I will get the number then.

 

Thank you, Breeze. That will be just swell.
How much power do you all think this simple mods will open up? Basically, a filter, exhaust, and ignition.
15-30HP? More, less? Just curious.