P heads and SMOG
- Thread starter DDSTANG94
- Start date
TrueBlue95GT
Member
Well the air pump part of the smog system has nothing to do with the heads as well as the EGR. The only thing that you can't continue to use would be the crossover tube on the back of the heads. If it's a big deal, get GT40's instead...
TrueBlue95GT
Member
Chern_889
New Member
why bother keeping the smog, if your going to be bypassing it anyways? if your worried about a visual inspection, just leave it in there until you get inspected, then pull it out. It cleans up the engine bay so much, and makes plug access so much better.
I wouldn't be bypassing it, just getting rid of the tubes that go to the head which from what i understand dont due much anyway, i still want the tube that goes on the h pipe, and it would be more hassle than its worth to take it off then put it on when needed
Chern_889
New Member
arent you running an offroad H-pipe? just remove the tube all together, its only to heat up the cats, which you dont have
Chern_889
New Member
plus i dont like the idea of sticking screws and bolts on vacuum lines to plug them, unless theres another way?
Chern_889
New Member
Thats what i did, works just fine, screw in a screw, and wrap some electrical tape around it
Thats what i did, works just fine, screw in a screw, and wrap some electrical tape around it
did u notice a difference in the car
TrueBlue95GT
Member
The smog pump is not there to heat up the cats...it injects oxygen into the exhaust to help catalyze the reaction of CO and O2 to make CO2...if you have the original H-pipe, keep the smog. If not, you can lose it.
JJ95GTID
Active Member
From my understanding the tube that goes to the back of the heads adds clean air to the exhaust to create a rich condition to "heat up" HO2 sensors or the pre-cats. By adding clean air to the exhaust it fools the HO2 sensors into thinking the engine is running lean and corrects that by adding fuel. It only does this on start up of the engine until the HO2 sensors come up to temp. That's why the exhaust sometimes smells rich on start up.
What I would do if I were you is remove the other AIR valve that diverts clean air to the crossover tube to the back of the heads. Leave the crossover tube and rubber hose that goes to it off and just run a single hose from the other AIR valve to the tube that goes under the car. That way if you need to put the catted H-pipe back on for emissions it will still function as a catalyst as stated above. Just be sure to get the engine up to temp before doing the smog test so that the cats are good and hot. They perform better that way.
Each one of those AIR valves has a vacuum line attached to it to activate it. Just plug the vacuum line from the AIR valve you take off.
What I would do if I were you is remove the other AIR valve that diverts clean air to the crossover tube to the back of the heads. Leave the crossover tube and rubber hose that goes to it off and just run a single hose from the other AIR valve to the tube that goes under the car. That way if you need to put the catted H-pipe back on for emissions it will still function as a catalyst as stated above. Just be sure to get the engine up to temp before doing the smog test so that the cats are good and hot. They perform better that way.
Each one of those AIR valves has a vacuum line attached to it to activate it. Just plug the vacuum line from the AIR valve you take off.
TrueBlue95GT
Member
Nope, it injects O2 to supply the needed component for converting the bad gasses into good gases. The two reactions that happen are:
CO + O2 --> CO2
HC + O2 --> H2O
So basically it reduces carbon monoxide and hydrocarbon emissions by converting them to carbon dioxide (what we exhale) and water.
Chern_889
New Member
He doesnt have to leave any of that stuff on the car, The GT40Ps have no provisions on the back of the head for any recirculation of anything, so it renders all of the Air pieces useless and just taking up space, you wont be able to make it properly function.
Not sure what you mean by difference. When i bought the car, the cats had been gutted already, and the tube to the H pipe was cut and pinched shut, causing the smog pump to make god awful noises. So while i was removing the smog pump, i removed all of the emissions ****, it was just wasted space.
At that particular time, i just capped the tube on the back of the heads and it worked great. At a later date, when i had the tranny out, i removed the tube, and used two bolts and plugged the holes.
That setup worked great for 2 years until the motor blew to smitherines, and that is when i switched to the GT40Ps, and yes, my current combo is running excellant, way better than stock.
JJ95GTID
Active Member
Thanks for clearing that up
Then, I wonder why the tube from the air pump connects to the x-pipe after the cats?
Seems like it would only be adding air to the exhaust after its been catalyzed.
Edit:
Ok, after some research I found that I am partially right about the crossover tube.
"Changing function
As emission control strategies grew more sophisticated and effective, the amount of unburned and partially-burned fuel in the exhaust stream shrank, and particularly when the catalytic converter was introduced, the function of secondary air injection shifted. Rather than being a primary emission control device, the secondary air injection system was adapted to support the efficient function of the catalytic converter. The original air injection point became known as the upstream injection point. When the engine is cold, air injected at this point cleans up the extra-rich exhaust and raises the temperature of the exhaust so as to bring the catalytic converter to operating temperature quickly. Once the engine is warm, air is injected to the downstream location — the catalytic converter itself — to assist with catalysis of unburned hydrocarbons and carbon monoxide."
Source:
Secondary air injection - Wikipedia, the free encyclopedia
It is used as a secondary system to quickly heat up the cats during cold startup.
Once the engine reaches a certain temp the primary system takes over and diverts air to the cats below.
So, what I said about just eliminating the crossover tube would allow the emission system to FUNCTION.
I suppose it would just take longer for the cats to come up to temp without it.
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