Warm up

[1999Porsche911]

As long as your secondary air pump is working properly, the difference in the amount of time it takes to go closed loop with your engine at idle versus driving away is immeasurable. The system will go closed loop in approximately the same amount of time, therefore, eliminating any addition time spent running rich. Therefore, the "running rich" argument is untrue. Open or closed loop is not dependent on engine temperature but on exhaust temperature.

Oh really, so what determines exhaust temp. Based on your comment all you have to do is wait for exhaust temps temps to rise. Hate to tell U, exhaust temps will run cooler when rich. You are partially correct, but the coolant temperature sensor controls almost exclusively the amount of fuel enrichment during times of cold running. More rich lower exhaust temps. O2 sensor does not come up to temp, open loop mode. Drive the car under laod, coolant temp comes up faster, sarts running more lean, exhaust temps come up quicker, O2 sensor goes into sending based on temp, and it now is in closed loop mode.

The air injection system pumps air into the exhaust system, bypassing the engine entirely. Your O2 esnors are also electrically heated. Educate yourself on the system and you'll learn how it works. Better yet, hook up your scanner and measure the time it takes the car to go closed loop, both ways.

I agree the pump bypasses the entire combustion process, so now tell me if the entire combusted mixture is not lean how the exhaust temps go up! Air pump simply dilutes the rich exhaust gasses with more air diluting the hydro carbons in an already burned fuel mixture. Combustion already took place. BTW since the coolant temp has not come up the ECU will not have enough input based on the table to actually make the car run at the proper 14.7 ratio, until the temp has come up. True closed loop mode is when the ECU can make very minor adjustments to the mixture. Otherwords a fully warmed engine, based on the coolant temp, O2 input, air temp, air flow etc. will it be in true closed lop mode where minor adjustments can be made. No one is debating if the O2 sensor is heated or not! But when in true closed loop mode the O2 sensor will have more fuel ratio input then when the engine is cold.

The secondary air pump is strictly an emission device to ward off the rich fuel pollutants. when the engine is cold!

As far as a scan tool your tool measures exhaust temps and exahust emissions? I bet the tool you are talking about only shows the O2 sensor coming up to temps and sending input to the ECU!

So no education needed!

I guess you have no interest in learning. The fact is, whether the engine temperature is at 50F or 200F, once in closed loop, you have a balanced air/fuel ratio. There really is no more to it than that. The is no "almost" closed loop" or "true" closed loop. You have either an open or closed loop, period. The O2 sensors do not look at the engine temperature, air temperature, timing or anything else but the level of oxygen passing by it. All they are interested in doing is telling the computer to either add or pull fuel if the mixture is not balanced. There is no comlex calculation made by the sensors, just a simple chemical reaction that either raises or lowers the sensor's voltage. If you cannot accept that as fact, there is no reason for me to give you a chemistry lessen on what happens when air is introduced to a mixture of CO and HC.

[pomocanthus]

Ummmm ... I'm learning a lot but what's with all the hostility?!?! We're all civilized Porsche owners here. Let's leave the hostility for the road and those Corvette owners :lol:

[1999Porsche911]

Ummmm ... I'm learning a lot but what's with all the hostility?!?! We're all civilized Porsche owners here. Let's leave the hostility for the road and those Corvette owners :lol:

If telling someone they are wrong and trying to educate them on the subject is being hostile, then I will continue to be so when necessary. You'll never find me practicing political correctness. :D

[Loren]

I highly suggest anyone interested in how OBD II functions on the Carrera pick up a copy of the 996 OBD II Manual (DME 5.2.2) -- (Sunset Imports has them on sale for $55). There are complete descriptions of function, theory, troubleshooting and Porsche terms (such warm-up cycle, drive cycle, trip, readiness code, etc.). A very valuable reference tool.

[geoff]

I highly suggest anyone interested in how OBD II functions on the Carrera pick up a copy of the 996 OBD II Manual (DME 5.2.2) -- (Sunset Imports has them on sale for $55). There are complete descriptions of function, theory, troubleshooting and Porsche terms (such warm-up cycle, drive cycle, trip, readiness code, etc.). A very valuable reference tool.

Loren - how much difference is there between the 996 OBD2 (DME 5.2.2) and the later DME 7.2 on an '01 Boxster? Similar enough to still be of value, or significant changes / advances?

[1schoir]

I highly suggest anyone interested in how OBD II functions on the Carrera pick up a copy of the 996 OBD II Manual (DME 5.2.2) -- (Sunset Imports has them on sale for $55). There are complete descriptions of function, theory, troubleshooting and Porsche terms (such warm-up cycle, drive cycle, trip, readiness code, etc.). A very valuable reference tool.

Loren - how much difference is there between the 996 OBD2 (DME 5.2.2) and the later DME 7.2 on an '01 Boxster? Similar enough to still be of value, or significant changes / advances?

On the same topic, how much difference between the 996 OBDII (DME 5.2.2) and the 986 Boxster OBDII (DME 5.2.2)?

Regards, Maurice.

[Loren]

I highly suggest anyone interested in how OBD II functions on the Carrera pick up a copy of the 996 OBD II Manual (DME 5.2.2) -- (Sunset Imports has them on sale for $55). There are complete descriptions of function, theory, troubleshooting and Porsche terms (such warm-up cycle, drive cycle, trip, readiness code, etc.). A very valuable reference tool.

Loren - how much difference is there between the 996 OBD2 (DME 5.2.2) and the later DME 7.2 on an '01 Boxster? Similar enough to still be of value, or significant changes / advances?

The basics are there and DME 7.2 has a few more codes.

The problem I have with the later DME manuals is that they don't explain the theory/function. Just codes and troubleshooting.

[fastboydave]

I highly suggest anyone interested in how OBD II functions on the Carrera pick up a copy of the 996 OBD II Manual (DME 5.2.2) -- (Sunset Imports has them on sale for $55). There are complete descriptions of function, theory, troubleshooting and Porsche terms (such warm-up cycle, drive cycle, trip, readiness code, etc.). A very valuable reference tool.

Loren........... superb!! That has made me smile! :D

[KevinMac]

I highly suggest anyone interested in how OBD II functions on the Carrera pick up a copy of the 996 OBD II Manual (DME 5.2.2) -- (Sunset Imports has them on sale for $55). There are complete descriptions of function, theory, troubleshooting and Porsche terms (such warm-up cycle, drive cycle, trip, readiness code, etc.). A very valuable reference tool.

Loren........... superb!! That has made me smile! :D

[KevinMac]

I highly suggest anyone interested in how OBD II functions on the Carrera pick up a copy of the 996 OBD II Manual (DME 5.2.2) -- (Sunset Imports has them on sale for $55). There are complete descriptions of function, theory, troubleshooting and Porsche terms (such warm-up cycle, drive cycle, trip, readiness code, etc.). A very valuable reference tool.

Loren........... superb!! That has made me smile! :D

Good because some who think thy have all the answers better read it.

The ECU in OBII has a cold paramater that is embeded within the table. This paramter can be changed under tuner conditions. The cold paramater preset by the factory is usuaully in the 60 degC to 80deg C. Once this temp is reached it goes to an off state which basically means that sensor input controls mixture. Until it reaches the preset value, the vehicle will

run at another mixture value other than the 14.7:1

This is basic OBDII. So anyone that says that once the O2 sensors reach their preheated temp the mixture goes to 14.7:1 does not understand the paramaters embeded in the ECU. Basic paramter setup by the manufacture and can be changed!