EGR observation
#1
01-07-2008
#2
01-07-2008
Member
#3
01-07-2008
#4
01-07-2008
H2O in the exhaust can cause icing in the EGR system. I believe that many older calibrations (pre-OBDII) simply turned off the EGR before intake temps could fall to or below 32F. The OBDII cals allow the EGR system to continue to operate at below freezing ambients but will shut it down if a fault is detected.
The following is from the EGR section of Ford's OBDII Theory & Operation.
The noticeable reduction in fuel economy in winter is mostly due to greater cold enrichment, longer warmup duration, higher friction and, in some regions, oxygenated fuels. I don't think that you can attribute much to the EGR shutting down. Its contribution to fuel economy is very small from a consumer's perspective but can sometimes be meaningful for CAFE numbers.
The following is from the EGR section of Ford's OBDII Theory & Operation.
Note: EGR normally has large amounts of water vapor that are the result of the engine combustion process. During
cold ambient temperatures, under some circumstances, water vapor can freeze in the DPFE sensor, hoses, as
well as other components in the EGR system. In order to prevent MIL illumination for temporary freezing, the
following logic is used:
If an EGR system malfunction is detected above 32F, the EGR system and the EGR monitor is disabled for the
current driving cycle. A DTC is stored and the MIL is illuminated if the malfunction has been detected on two
consecutive driving cycles.
If an EGR system malfunction is detected below 32F, only the EGR system is disabled for the current driving
cycle. A DTC is not stored and the I/M readiness status for the EGR monitor will not change. The EGR monitor,
however, will continue to operate. If the EGR monitor determined that the malfunction is no longer present (i.e., the
ice melts), the EGR system will be enabled and normal system operation will be restored.
cold ambient temperatures, under some circumstances, water vapor can freeze in the DPFE sensor, hoses, as
well as other components in the EGR system. In order to prevent MIL illumination for temporary freezing, the
following logic is used:
If an EGR system malfunction is detected above 32F, the EGR system and the EGR monitor is disabled for the
current driving cycle. A DTC is stored and the MIL is illuminated if the malfunction has been detected on two
consecutive driving cycles.
If an EGR system malfunction is detected below 32F, only the EGR system is disabled for the current driving
cycle. A DTC is not stored and the I/M readiness status for the EGR monitor will not change. The EGR monitor,
however, will continue to operate. If the EGR monitor determined that the malfunction is no longer present (i.e., the
ice melts), the EGR system will be enabled and normal system operation will be restored.
#5
01-07-2008
#6
01-07-2008
Originally Posted by wydopnthrtl
Thanks for the input Bob.
I've been under the impression that a non working or disconnected EGR will decrease MPG. And that's what I've observed too. Maybe it's not the root cause though...
Rich
I've been under the impression that a non working or disconnected EGR will decrease MPG. And that's what I've observed too. Maybe it's not the root cause though...
Rich
#8
01-07-2008
#12
01-08-2008
5 or 6 so far.
IMO the only thing I am disappointed with is the refresh speed when looking at the 02s. I'll have to use the x-cal & data log to capture the specific info I'm needing. Otherwise it's nice to have this scanguage w/me 24/7 (I'm also ordering an extra cable so I can use it to look at other cars)
Rich
IMO the only thing I am disappointed with is the refresh speed when looking at the 02s. I'll have to use the x-cal & data log to capture the specific info I'm needing. Otherwise it's nice to have this scanguage w/me 24/7 (I'm also ordering an extra cable so I can use it to look at other cars)
Rich
#16
01-08-2008
Overpriced... oh I don't really think so. One thing it's "not" is a true diagnostic tool. That I'll give you. But having the ability to read data live as you drive down the road, read & clear DTCs, and have the ability to use it on other cars is worth the cost. To me anyway.
I sold my autotap so I could get one. So far I'm happy with it. Would not have done it w/o having the SCT x-cal as a backup though.
Rich
I sold my autotap so I could get one. So far I'm happy with it. Would not have done it w/o having the SCT x-cal as a backup though.
Rich
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