[updated:LAST EDITED ON 16-Jun-02 AT 10:15 PM (EST)]I just bought an `85 F350 with 460 engine. I want to remove the air pump system and have already pulled the pumps. I have not yet tackled the lines going into the exhaust manifolds. I suspect with the age and mileage on this motor they are essentially welded in at this point. What would be the best way to get the lines out and the threaded holes plugged? I guess I could cut the tubes near the manifold and then have them brazed shut. Any other thoughts?

Thanks.

Mark

 

I do not have the tubes to the exhaust manifold on my 86 F350 w/460, but I am considerring removing the airpump, but I am concerned that it will actually hurt performance not to mention not legal.


does anyone know if disconecting the pump does anything for performance?

 

It is a common practice for the unknowledgeable to disconnect emmisions control devices in search for better power. In reality there are NO horsepower gains by doing these things. The only exception being the air pumps. You can spend hours disconnecting, plugging, and hacking things up to accomplish this. And for all of these hours of work you will gain a whopping .5-1hp. You would make more horsepower by takin that time to make sure your engine is in perfect tune (most tune-ups can make up to 15hp). You could also spend that time creating a more efficient cold air intake that may make 5hp or more. I think you get the point, there are better ways to make horsepower than hacking up a finely tuned emmisions system. This is my educated opinion, apoligies in advance for anyones toes I may have stepped on.

 

I recently bought an '86 E350 based class B rv. I am putting on Hedman hedders that don't have the fittings for the air pump. What it required to make them work with the pump? What will the consequences be if I don't use the air pump. It is my understanding that the addition oxygen aids in burning any uncombuses fuel that remains in the exhaust so I don't see what if any effects it will have until I can hook it back up.

Thanks in advance.
Jim

 

Jim,

Some header manufacturers have headers that have the ports so that you can hook up the air pump tubes. It is my understanding that there is not any negative effects on the performance of the motor other then emission issues if the pumps are removed. In that mine were shot anyway I just took them off. If anyone has some experience at this I’m still looking for the best way to get those tubes out of the way.

I agree with the comments made by phantom429 in that in most cases the engines are designed for the properly functioning emission equipment. Simply removing the device will generally cause more problems then it cures. The air pumps, somewhat like a cat, deals only with the exhaust stream and thus does not have a direct impact on the performance of the engine.

Thanks

Mark

 

Thanks for confirming that. Is the position of the air injection critical to it's function? It would seem to be easier to locate them farther down on the exhaust that drilling and taping into the headers. Sorry I am working from theory since it is in the shop waiting for the hedders and I didn't pay too much attention to the stock location and number of injection points.

Jim

 

[updated:LAST EDITED ON 02-Jul-02 AT 10:03 PM (EST)]Hey Jim. There will be no problems with eliminating the air tubes from the manifold. If you follow the maze of air tubes you will see that there are either 1 or 2 tubes going to your cat (if equipped). Air is only pumped into the manifolds during closed loop operation when the PCM is no looking at the O2 sensor. The air is pumped into the manifolds during cold start enrichment to aid in the burning of un burnt fuels inside the manifold/downpipe. During this time the cat is too cold to work so it is pointless to pump air to them. That is why you have the diverter valve pump air to the heads.

When the engine is in closed loop the air is then directed into your cat, thus aiding in the catalytic action. If air were to be pumped in to the heads at this point the O2 sensors would see the air as a lean mixture and cause to engine to run rich.

Anyways sorry to ramble on but long story short, it is just fine to run headers without air tubes, as long as you have air going to the cat.

 

Great explanation,thanks! I don't have a cat though so it looks like the air pump may become an on board air compressor.

Jim

 

Good comments by all. I am still hoping to hear if anyone has any experience on the best way to get the tubes out of the exhaust manifold or the tubes plugged.

Thanks all,

Mark

 

no problem Jim. I don't want to come across as a **** polution hating tree hugging sap. I only want people to know what will happen when they take stuff like air pumps,EGR valves,PCV valves etc.. off their vehicles. Good luck with your air pump modification.

P.S. Air pumps make like 5p.s.i. so using it for anything other than blowing up an air matress would be beyond me.

 

Mark,

What worked for me was to start spraying the nuts with penetrant a day or two in advance. Then use a dremel tool with a cut-off disc to cut the tube about 1 to 1 1/2 inches above the nut. Another cut or two on top by the carb so the unit comes out in a couple peices. Then you can get on the nut with a deepwell 6 point socket to get them out. If it doesn't come then you have enough tube to crimp and bend to seal it. Special tubing plugs from the parts store to fit the holes where the nuts came out.
Lance

 

Might as well use the tubes to get some extra hp and have a better running engine instead of removing them.

If you don't have emissions testing and can do away with the pump, leave the exhaust manifold tubes in and use them as exits for a crankcase evacuation system.

Mr. Gasket makes one for about $40 (if you already have the exhaust tubes just buy the components since you won't need the weld-in bungs). It includes push-in valve cover breathers and valves. This gets rid of oil contaminated fuel mixtures from your PVC system (toss that) and allows the rings to seal better without the crankcase pressure produced by PVC systems.

 

PS, installing a crankcase evac system also covers the tree huggers as it's more efficient than a stock PVC system.

 

Hey Nick,

I'm confused on the O2 sensor closed loop stuff. I thought the term closed loop referred to the O2 reading feeding back to the ECM and correcting the pulse width to get the desired air-fuel ratio.

I thought the older pre-EFI trucks had exhaust or in-head manifold air injection, but the EFI trucks had air injection down stream of the O2 sensor.

John

 

Hi John. I have spent a few years in shcool studying fuel injection so there is a lot to learn, and I could ramble on forever. But I will keep it as short and simple as possible.

Almost all fuel injection systems have for the most part, two modes of operation; open loop, and closed loop.

Open loop operation is a non feedback type of fuel injection. During open loop operation, the injector pulse width is determined solely by a set fuel map in the pcm. This fuel map is used when the engine is cold, when one or more of the sensors becomes out of range or inoperative, or if the O2 sensor gets cold during idling. During open loop there is no fuel trim, and no O2 crosscounts. This is simply a mode that the PCM knows the engine will run on in order to warm up, or to limp into a repair shop.

Closed loop operation incorperates all of the sensors as inputs, including the 02 sensor. The 02 sensor is used to monitor the amount of oxygen in the exhuast stream. The pcm then adjusts or trims the injector pulse width to keep the A/F ratio at 14.7% in most cases. The PCM will also cause the fuel mixture to vary rich to lean about 20 times in a 10 second period in order to increase catalytic converter efficiency. Modern OBD2 systems will achieve full closed loop operation in under 30 seconds! Some of the older systems may take a few minutes. The early Caddy fuel injection was always in open loop as it had no 02 sensor.

So you can see if we injected air befor the 02 sensor during closed loop operation, we would have quite the problem. The 02 sensor would see this extra oxygen and send a lean signal to the pcm. The pcm will then increase the injector pulse width, causing the engine to run ritch. So instead we pump it to where it is more effectve, to the cat. You may also notice that on many cats it is pumped into the middle of it. This denotes a 3 way cat, that reduces 3 gases (CO,HC,and NOX).

Anyways enough rambling, I hope that I have cleared some things up, or at the very least put you to sleep.



Nick from the frozen north
1974 F-250 4X4
soon to be 429
dana 60 front and rear