Air pump questions

[schambergerst]

I am new here. First off I want to say this has got to be one of the most helpful sites I have found on the web by far. And let me tell you I am on the interent alot. College will do that to you.

I have done a search on this already, and I have learned that many people have removed there air pumps without any bad affects(that they know of). And I understand that it won't through an engine light or any codes. I also understand what the pump is for, but my question is when does it pump air into the manifold and when does it pump it to the air filter? I know it pumps it to the manifold during warmup, but does it do it during any other situations? ANd if it does do it under other situations, it seems to me it would mess with the O2 readings. So does the computer have to make any changes accordingly when the air is channeled to the manifolds? I want to know because I am replacing the cracked headers and am debating to keep the air system or not. No emisions here. I have had no luck finding out what I want to know in the chilton book. Hopefully someone can help me here. thanks

 

[BIG*RED]

umm wow, its been a while since i looked at one, but i can't remember the smog pump aka air pump..pumping in to the air filter..it pumps air into the exhaust manifolds yes..if you have no smog laws, and are getting headers then just get rid of it..or keep it, makes no real diference..despite what some peole think, it doesn't "rob" any power from the engine..except maybe a very miniscule amount becasue of the extra belt/pully.. i have mine off my engine right now (becasue its ugly and doesn't go with all my shinny engine parts..mmmm shiney)...but i put it back on when its time to get a emission test..and i have nver noticed any real diference between having it on or taking it off

 

[Fierospeeder]

ill get very brief on how it works.

When the engine is cold, the air is pumped into the manifold.
When the engine is hot, the air is pumped into the catalytic converter.
And there are the few conditions when it gets turned off or redirected.

The only reason people remove the air pump is because they want to pollute the air quicker.

The only purpose of the system is to help the catalytic converter to reduce the harmful emissions out of the tailpipe

 

[BIG*RED]

yeah thanks..i didn't think it pumped into the air filter..good thing you posted up, iwas about to put on my shoes and grab my flashlight and go look under my hood..and its cold out there...now i can stay warm and toasty right in front of the computer....oh i didn't take mine off to pollute the air faster..i took it off becasue it wasn't shiney...lol..and that right there is a topic of discussion that i have heard many times, and may people are very firm in their belifes...some say taking off the smog pump and or cat pollutes the air quicker, and yet some say alot of the restored musclue cars, and hot rods, that don't run cats or air pumps actually run cleaner than the cars that do have them..i worked at a hot rod shop, and had to listen to everyside of this argument at least 5 times a week..

 

[Fierospeeder]

WTH u talking about. Cold in california?

Some applications, it will pump into the air filter, or have an "exhaust" if there is excessive backpressure, or a circumstance where the pump shouldn't be used.


The only way to prove it to someone. Is to hook up a 4 gas analyzer, even 2 will work. And have the pump on and off while testing.

I wouldn't run a cat on anything that is old, unless it has EFI or a feedback carb. "note, i stated electronic fuel injection, not fuel injection "

 

[BIG*RED]

thanks for the info, thats why i like this place..learn something evertime i come here..and yes it gets cold in california. especially up here in the sierra nevada mountains..granted im in the foothills, but it gets below freezing from time to time..last i checked it was 38 degrees outside my house..

 

[schambergerst]

When the pump doesn't divert the air to the manifolds it will divert it to the air filter in my case, I have seen others that diverts it to the cats though. Sorry I don't just take your guys word for it that it will run "ok" if I take the pump off. But something still doesn't make sense to me, if the pump under certain conditions pumps air into the manifolds upstream from the o2 sensor, then wouldn't this make the o2 sensor give a false lean reading, and then the computer would richin the air/fuel mixture? It just seems to me that the computer has got to do something about the sudden extra oxygen present in the exhaust? Maybe I am looking into this to much, or maybe it isn't that big of a deal, but I was just curious.

 

[dyeager535]

Yes, in some vehicles (some cars) the AIR was diverted to the manifolds (upstream of O2) and the "code" that runs the system does have an offset for the value the O2 sees under that condition. Thus in certain car apps, removing AIR will in certain conditions, change engine performance falsely.

In the code I looked at for the '747 ECM (what the TBI trucks used) I didn't see reference to that same O2 offset/divert to manifold as in the cars.

In a truck then, AIR isn't injected into the manifolds when the O2 is trying to regulate the mixture, which is how GM avoided any false lean condition.

Trucks don't divert to the catalytic converter as you found out.

 

[schambergerst]

That makes sense. That is exactly what I wanted to know. Thanks alot, dyeager535. How did you find all that out by the way? Are you actually looking at the computer "code" and deciphering it, because if you are that is pretty cool. That kind of explains why people that remove the air pumps on 350 TBI trucks don't run into any problems. Thanks again.

 

[Fierospeeder]

anyone can find the coding to ECM proms on the web. Now someone that actually can program in assembler is cool. And im not forgetting the C++ coders too.


My bad, on the air being diverted to the cat. But that is the typical application for "most" vehicles. Even, if it isn't being diverted to a cat, you can still run the vehicle without AIR.

The computer doesn't need to compensate for the air in the system. I wont get into detail, because i have no copyright rights in this forum.

 

[dyeager535]

That makes sense. That is exactly what I wanted to know. Thanks alot, dyeager535. How did you find all that out by the way? Are you actually looking at the computer "code" and deciphering it, because if you are that is pretty cool. That kind of explains why people that remove the air pumps on 350 TBI trucks don't run into any problems. Thanks again.

I found this out by not reinventing the wheel. I am in the process of getting my TPI to run "perfect" on my engine, and this is stuff you run across when reading posts at sites where the information is discussed and explained by people that are years and years ahead of most simply because they started doing this so long ago. In my case, it would be pointless to analyze the coding differences between the 86-87, 88, and 89 '165 masks, when they've already been analyzed, discussed to death, and explained in great detail. (as a for-instance. The '747 TBI ECM is the same way I'm sure)

If you dig into the arena more, you'll find that almost all of the information discovered so far is freely shared by those doing the work, and not too hard to find.

This is the whole basis of the DIY PROM editing "movement". Getting the knowledge to the masses so they can do their own modifications. There is a never-ending learning curve, but it's quite rewarding.

Here is one place where you can look/download the source code and hacks: moates.net