Removing the air pump
02-17-2004, 11:10 AM
#16
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I my be totaly mistaken but i was told that the air pump was used to dilute the emissions emitted by the engine upon initial start up. I believe there was a requirement that emissions needed to meet a certain level minutes after starting a cold engine. So by injecting fresh air into the exhaust it reduced the overall ppm of CO and other gases at cold idle. I believe you would call it a bandaid approach to meeting DOT requirements.
I don't know if this means anything but I removed the air pump and injectors from both the SC's i owned. I always passed emissions and when I sold both cars they both had excellent leak down and compression numbers. One car had 95k miles the other 45k. Then again these cars don't run as hot.
It may be possible that the turbos had a chamber cored into the head that allowed it to provide cooling. I do not recall seeing anything in the manuals showing that. I will try to check tonight and see if it breaks down the system enough to tell.
I don't see why the system should affect performance or lag
I don't know if this means anything but I removed the air pump and injectors from both the SC's i owned. I always passed emissions and when I sold both cars they both had excellent leak down and compression numbers. One car had 95k miles the other 45k. Then again these cars don't run as hot.
It may be possible that the turbos had a chamber cored into the head that allowed it to provide cooling. I do not recall seeing anything in the manuals showing that. I will try to check tonight and see if it breaks down the system enough to tell.
I don't see why the system should affect performance or lag
02-17-2004, 11:41 AM
#17
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PorschePHD sent me this:
"Well, the dealer is always a wealth of info
The head configuration was no different than years past and in fact the part numbers all the components were all the same If the system is on it actually causes the head to heat up, not cool down. The exhaust run hotter which in turn causes the head to be hotter and the valve guides to cook. The truth is almost all the turbos need guides regardless at some point. Nature of the beast. Some sooner than others. Guides that are bad do use more oil. They don't typically cause issues with the pistons, but they do foul plugs and smoke. eventually running issues come into play.
I would certainly remove the air pump if it was mine and emissions are not an issue.
Hope this helps.
Stephen"
I guess if the air pump does not turn off from the cylinder head injection it will have some ugly results.
"Well, the dealer is always a wealth of info
The head configuration was no different than years past and in fact the part numbers all the components were all the same If the system is on it actually causes the head to heat up, not cool down. The exhaust run hotter which in turn causes the head to be hotter and the valve guides to cook. The truth is almost all the turbos need guides regardless at some point. Nature of the beast. Some sooner than others. Guides that are bad do use more oil. They don't typically cause issues with the pistons, but they do foul plugs and smoke. eventually running issues come into play.
I would certainly remove the air pump if it was mine and emissions are not an issue.
Hope this helps.
Stephen"
I guess if the air pump does not turn off from the cylinder head injection it will have some ugly results.
02-17-2004, 09:40 PM
#18
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My air pump is frozen I discovered today when they pulled the engine. Apparently it only has a benefit when the engine is cold by pumping air into the exhaust allowing the catalytic converters to be more efficient . Once the engine is warm it serves no purpose. In Texas emmissions are checked with the engine at normal operating temperature so it doesn't matter if it is there or not.
Maverick
Maverick
02-18-2004, 03:20 AM
#19
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Originally posted by maverick
My air pump is frozen I discovered today when they pulled the engine. Apparently it only has a benefit when the engine is cold by pumping air into the exhaust allowing the catalytic converters to be more efficient . Once the engine is warm it serves no purpose. In Texas emmissions are checked with the engine at normal operating temperature so it doesn't matter if it is there or not.
Maverick
My air pump is frozen I discovered today when they pulled the engine. Apparently it only has a benefit when the engine is cold by pumping air into the exhaust allowing the catalytic converters to be more efficient . Once the engine is warm it serves no purpose. In Texas emmissions are checked with the engine at normal operating temperature so it doesn't matter if it is there or not.
Maverick
Also the info L8Apex got from Stephen at Imagine Auto, if you pump air into a fire it gets hotter.
02-18-2004, 04:39 AM
#20
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Thanks a lot for all the answers. The damn thing is off 
or may be just cut the belt to have the option to put it back to pass smog test (if the car fails in the 1st place)
or may be just cut the belt to have the option to put it back to pass smog test (if the car fails in the 1st place)
02-19-2004, 09:22 PM
#21
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Just received an interesting book today.
The 93 Porsche Service Information Technik book for turbo 3.6.
It breaks down how the Secondary Air Injection system works:
Secondary air injection after start of engine, Temp < 35C
It's purpose is to improve exhaust emission levels and to speed up heating the cats and O2 sensor to operating temp. fresh air is drawn in by the secondary air pump at engine temps of < 35C and is supplied to the air diverter valve. The acceleration enrichment relay supplies voltage to the solenoid shift valve after each engine start to allow the valve to open, thus feeding vacuum from the intake manifold to the air diverter valve, causing this valve to open and inject fresh air downstream of the exhaust valves.
Secondary Air Injection at Engine Temp > 35C
Engine started at temps > 35C or if 60 sec have elapsed after engine has been started at <35C, the voltage of the solenoid shift valve has dropped, air diverter valve has toggled and secondary air is now fed to air diverter valve. Since the solenoid shift valve is fed a ground pulse from the Turbo control unit, manifold vacuum is applied to the air diverter valve and secondary air is blown into the cat.
To protect the cat against excessive temps, the ground signal to solenoid shift valve II is interrupted at 4,000 rpm, causing the secondary air to be diverted across the air diverter valve into ambient air.
I hope you find this interesting.
The 93 Porsche Service Information Technik book for turbo 3.6.
It breaks down how the Secondary Air Injection system works:
Secondary air injection after start of engine, Temp < 35C
It's purpose is to improve exhaust emission levels and to speed up heating the cats and O2 sensor to operating temp. fresh air is drawn in by the secondary air pump at engine temps of < 35C and is supplied to the air diverter valve. The acceleration enrichment relay supplies voltage to the solenoid shift valve after each engine start to allow the valve to open, thus feeding vacuum from the intake manifold to the air diverter valve, causing this valve to open and inject fresh air downstream of the exhaust valves.
Secondary Air Injection at Engine Temp > 35C
Engine started at temps > 35C or if 60 sec have elapsed after engine has been started at <35C, the voltage of the solenoid shift valve has dropped, air diverter valve has toggled and secondary air is now fed to air diverter valve. Since the solenoid shift valve is fed a ground pulse from the Turbo control unit, manifold vacuum is applied to the air diverter valve and secondary air is blown into the cat.
To protect the cat against excessive temps, the ground signal to solenoid shift valve II is interrupted at 4,000 rpm, causing the secondary air to be diverted across the air diverter valve into ambient air.
I hope you find this interesting.
