mchan68 Posted July 9, 2009 Share Posted July 9, 2009 With all this discussion on IAT #2's purpose, the only time I've ever remembered it being of any significance, was back when 06E17 was released. Shortly after, there were numerous owner complaints of driveability issues relating to bogging. What was found, was the EGR valve cycling quite erratically, including one vehicle that had come back for three visits before I could fix (back when I was "green" to fixing diesels, which I could still argue that I AM still "green"). Sure enough, cleaning off IAT #2 fixed the issue permanently. I vaguely recall a drastic increase the IAT #2 response to EGR valve being commanded open, as I was monitoring the PIDs. Just my Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted July 9, 2009 Share Posted July 9, 2009 Let's not forget some of the other conditions that can influence IAT2.... restricted airflow across the CAC is the first one that comes to mind. We have seen cooling stacks about plugged right off - and the first drivability complaint we generally hear of is engine overheat... If IAT2 was consistantly higher than some predetermined level, would we expect to see an excess EGR flow code? High boost levels would also deliver higher than normal IAT2... stationary PTO operation or a V-Mac compressor - used to be an operator would open the hood on his truck when running an engine driven air compressor but that practice appears to have gone by the wayside. A stuck open EGR valve.... one wouldn't expect to see a stuck open valve along with a failed valve position sensor at the same time...... but, in the grand scheme of things, how many times are we seeing systems with multiple concerns delivering a drivability camplaint.... LOTS. I can see IAT2 being (in current configuration and because each reflash needs to, as far as I see it, pass EPA scrutiny for specific criteria) used in computations for fuel, boost and EGR decisions, but only in the sense that high charge air temp will deliver high combustion chamber temps. Navistar engines (those designated as VT365) and "Ford" engines (those designated 6.0PSD) are worlds apart in so many respects.... 90some HP being something that sticks out like a wedding prick. There be a chance that comparing the two operating systems might be akin to comparing road kill to fresh veggies... I DON'T KNOW.... and the few times I have asked, I have usually gotten a reply that was almost, nearly in the ballpark of the answer I wanted/expected.... So... what can we be sure of when we discuss IAT and IAT2? IAT before we take our intake air and "process" it. If the truck has a stock air filter, IAT will be close to ambient.... If the truck has a cold air intake, expect something much higher.... closer to underhood temps. IAT2 is what we get AFTER we process (or perhaps MISprocess) our intake air. Far too many variables begin to creep into the picture - have they been accounted for? Do they need accounting for? But, somewhere along the line, we come to the realization that a gooped off IAT2 is the sign of quite another concern.... perhaps, instead of analysing the effects of a gooped IAT2.... we should get IAT2 to stop getting gooped???? Sadly, I'm not sure we can achieve that goal..... Quote Link to comment Share on other sites More sharing options...
Damon Posted July 9, 2009 Share Posted July 9, 2009 Originally Posted By: Damon I have no opinion, because I haven't tested it. It wouldn't be hard to do, and I assure you I will do so. I'll see how EGR operates when IAT2 matches IAT as an ambient temp sensor under identical driving conditions. I'm not following you here. Are you stating you are going to watch EGR command when IAT and IAT2 are the same temp? They almost never are, except at cold startup when the EGR won't be functioning because cold engines don't produce NOx (which is what an EGR is there to reduce). During driving conditions, IAT and IAT2 will never match. Or, are you stating you will modify the IAT2 signal via an external sensor or signal generator, to match the IAT's signal? Correct. Simply plug another IAT2 sensor into the harness, but leave it out of the intake. That'll be an easy way to make another ambient temp sensor and it'll be fun to see how EGR behaves as a result. Originally Posted By: Bruce Amacker I've always felt the PCM was watching IAT2 to confirm EGR flow, as well as using it as a general input for fuel strategy, timing, idle speed, glow plug, and VGT, among other things.. Exactly my understanding as well. Quote Link to comment Share on other sites More sharing options...
Damon Posted July 9, 2009 Share Posted July 9, 2009 Originally Posted By: Damon I can't say that based on this alone it stands to reason that IAT2 isn't partly responsible for fault detection though. It would be great to hear more on this from an engineer that actually has the answer. It seems the more I go looking for answers the more questions I have. I had one additional thought for us to chew on. I have yet to see an IAT2 sensor that didn't have carbon packed around the thermistor and I question the impact of that carbon on the sensor's ability to react to temperature changes quickly or it's accuracy for that matter. Precisely my point. I can't say I've seen a skewed or failed IAT2, but we've all seen heavily insulated (and therefore lazy)ones. THAT just *MAY* cause a bit more EGR than we'd have otherwise. Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted July 9, 2009 Share Posted July 9, 2009 Quote: we should get IAT2 to stop getting gooped????Sadly, I'm not sure we can achieve that goal..... Sure we can. Ford will simply design a cute little shield for us to install around the sensor. Quote Link to comment Share on other sites More sharing options...
Damon Posted July 9, 2009 Share Posted July 9, 2009 I was always under the impression that the two sensors also gave the PCM a good indication how well the intercooler was doing/how hot the charge air temp was. Yep, it does that too. But oddly, you don't see these sensors on many aftercooled engines that don't also have EGR valves. So it stands to reason the primary function of this sensor is for emissions control feedback. Remember: We don't have anything in the exhaust system, this all needs to be inferred. Quote Link to comment Share on other sites More sharing options...
Damon Posted July 9, 2009 Share Posted July 9, 2009 Let's not forget some of the other conditions that can influence IAT2.... restricted airflow across the CAC is the first one that comes to mind. We have seen cooling stacks about plugged right off - and the first drivability complaint we generally hear of is engine overheat... If IAT2 was consistantly higher than some predetermined level, would we expect to see an excess EGR flow code? No, because it still has pintle position and EBP to look at... Originally Posted By: Jim Warman High boost levels would also deliver higher than normal IAT2... stationary PTO operation or a V-Mac compressor - used to be an operator would open the hood on his truck when running an engine driven air compressor but that practice appears to have gone by the wayside. Not higher than normal in this case either.... because the sensors are accurately reporting information that coincides with the actual conditions. I have a customer that runs a splitshaft PTO off a few 550 6.0's at WOT full load and not moving. That's not common these days, but still done. Where problems usually occur is when sensors report information incorrectly, or correct information too late for correction. Originally Posted By: Jim Warman I can see IAT2 being (in current configuration and because each reflash needs to, as far as I see it, pass EPA scrutiny for specific criteria) used in computations for fuel, boost and EGR decisions, but only in the sense that high charge air temp will deliver high combustion chamber temps. Navistar engines (those designated as VT365) and "Ford" engines (those designated 6.0PSD) are worlds apart in so many respects.... 90some HP being something that sticks out like a wedding prick. There be a chance that comparing the two operating systems might be akin to comparing road kill to fresh veggies... I DON'T KNOW.... and the few times I have asked, I have usually gotten a reply that was almost, nearly in the ballpark of the answer I wanted/expected.... No doubt. I was NOT trying to imply that the engines are identical in their operation, but it appears that IH and Ford are using the same technical information source when discussing the theory of operation of these engines. All the (Ford AND IH) theory of operation books I see that show a circuit function diagram of the IAT2, they always show it with the EGR in the schematic as well, like the picture I posted earlier does. There's a good reason for that. Originally Posted By: Jim Warman So... what can we be sure of when we discuss IAT and IAT2? IAT before we take our intake air and "process" it. If the truck has a stock air filter, IAT will be close to ambient.... If the truck has a cold air intake, expect something much higher.... closer to underhood temps. IAT2 is what we get AFTER we process (or perhaps MISprocess) our intake air. Far too many variables begin to creep into the picture - have they been accounted for? Do they need accounting for? Yes, they do. Boost, CAC effect, EGR, RPM, and coolant temp will all play a role in the deviation of IAT2 vs IAT. I'll agree that this sensor isn't a MAJOR input, but it is part of the sensor redundancy needed to validate some inputs when others might disagree. Originally Posted By: Jim Warman But, somewhere along the line, we come to the realization that a gooped off IAT2 is the sign of quite another concern.... perhaps, instead of analysing the effects of a gooped IAT2.... we should get IAT2 to stop getting gooped???? Honestly, I think it's a location thing. That should be an easy fix. The irony of this is that the goop on the IAT2 causes more goop on the IAT2, which is kinda what I was trying to get at when everybody giggled at the dealer that sold the IAT2 on a truck that clearly needs more work. While it won't fix the truck that started this thread, it would be an important part of the work needed to prevent the repeat occurrance, IMHO. Quote Link to comment Share on other sites More sharing options...
rlchv70 Posted July 9, 2009 Share Posted July 9, 2009 I'm not as familiar with the 6.0s as I am the 6.4s, so I could be wrong. But, I believe IAT2 or MAT only disables EGR at low or very high temperatures. Otherwise, it plays no other role in EGR control. Quote Link to comment Share on other sites More sharing options...
Damon Posted July 9, 2009 Share Posted July 9, 2009 The 6.4 has an EGRT inlet and outlet sensor, so the function of IAT2 wouldn't be needed for any part of EGR control until something went wrong elsewhere. Quote Link to comment Share on other sites More sharing options...
rlchv70 Posted July 10, 2009 Share Posted July 10, 2009 My comment was only talking about the 6.0. I only included the 6.4 because I am not as familiar with the 6.0 as I am the 6.4. Quote Link to comment Share on other sites More sharing options...
Damon Posted July 10, 2009 Share Posted July 10, 2009 So then why would you believe that IAT2 would be used instead of IAT for disabling EGR in extreme temps on a 6.0? I mean if IAT2 was frigid cold, it couldn't possibly have any EGR to disable. if it was too hot, it probably couldn't disable it anyway. Quote Link to comment Share on other sites More sharing options...
slim Posted July 10, 2009 Share Posted July 10, 2009 From the 2005 OBD operation summary Note: Exhaust Gas Recirculation (EGR) Cooler Efficiency Monitor is not incorporated for 2005 Job#1. Planned for release as a 2005 running change. Exhaust Gas Recirculation (EGR) Cooler Efficiency Monitor: DTCs P2457 – Exhaust Gas Recirculation Cooler System Performance Monitor execution Continuous (8ms) Monitor Sequence None Sensors OK Intake Air temperature Sensor 2 (IAT2). Mass Air Flow Sensor (MAF) Barometric Pressure Sensor (BARO) Intake Air Temperature Sensor (IAT) Engine Oil Temperature Sensor (EOT) Manifold Air Pressure Sensor (MAP) Exhaust Pressure Sensor (EP) Exhaust Gas Recirculation Position Sensor (EGRP) Exhaust Gas Recirculation Valve Actuator Monitor (EGRAM) Electronic Variable Response Turbocharger Actuator (EVRT) Monitoring Duration Greater than 1 minute Typical Exhaust Gas Recirculation (EGR) Cooler Efficiency Monitor Entry Conditions: Exhaust Gas Recirculation (EGR) valve close position has been learned, engine off timer > 60 minutes, engine speed (N) 600-750 RPM, fueling desired (MFDES) 4-16 mg/stroke and Exhaust Gas Recirculation (EGR) valve position greater than 0.08. Typical Exhaust Gas Recirculation (EGR) Cooler Efficiency Monitor Thresholds: P2457 – Fault sets if IAT2 > 85 deg .C From that information I would conclude that the calibration only uses the IAT2 to sense EGR cooler efficiency as well as fuel and timing. This code might be used on California calibrations only. I have never seen this code set and it looks like the monitoring window is pretty small. Quote Link to comment Share on other sites More sharing options...
Damon Posted July 10, 2009 Share Posted July 10, 2009 I can't reach the same conclusion. The same operation summary says: Quote: The Delta Pressure Exhaust Gas Recirculation (EGR) System is a closed loop EGR Valve Position control system. It utilizes an exhaust manifold pressure sensor, an intake manifold pressure sensor and a speed density estimate of total mass flow and derives a desired EGR Valve position based on a desired EGR flow percentage Can this speed density estimate be accurate without knowing the temperature of this air? IAT alone can't do that. Quote: The EGR Monitor is a series of electrical tests and functional tests that monitor various aspects of EGR system operation. When normal EGR rates are being commanded and when the engine enters into either one of two specified operating ranges, a flow check is performed. The operating ranges are defined to insure an adequate amount of EGR is being requested to allow for an accurate estimate of the EGR flow percentage. At this point EGR flow is estimated based on the difference between the Mass Air Flow (MAF) sensor reading and the total mass flow calculated by the speed density calculation. The estimated EGR flow is then compared to the expected EGR flow to determine if there is insufficient or excessive flow. Even for a P0401 or P0402 monitor to run, the following sensors must be OK: Intake Air temperature Sensor 2 (IAT2). Mass Air Flow Sensor (MAF) Barometric Pressure Sensor (BARO) Intake Air Temperature Sensor (IAT) Engine Oil Temperature Sensor (EOT) Manifold Air Pressure Sensor (MAP) Exhaust Pressure Sensor (EP) Exhaust Gas Recirculation Position Sensor (EGRP) Exhaust Gas Recirculation Valve Actuator Monitor (EGRAM) Electronic Variable Response Turbocharger Actuator (EVRT) Quote Link to comment Share on other sites More sharing options...
Aaron Posted July 10, 2009 Author Share Posted July 10, 2009 Quote: we should get IAT2 to stop getting gooped???? Sadly, I'm not sure we can achieve that goal..... Sure we can. Ford will simply design a cute little shield for us to install around the sensor. Little plate that slips in front of it Quote Link to comment Share on other sites More sharing options...
sixturbosix Posted July 11, 2009 Share Posted July 11, 2009 Hell, somebody slip over to autotrend forums and ask Rex.He will clear up all the questions you have.You may want to call it an IATS or something so he will know what the hell your talking about. Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted July 12, 2009 Share Posted July 12, 2009 Adding EGR should reduce combustion chamber temps... after all, that is what the EGR is supposed to do (reducing NOx generation). As for some of the other stuff.... if we know IAT (ambient), ambient air density (BARO), MGP (boost), IAT2 (CAC efficiency), EBP (inferred or real) and MF_DES - I am reasonably sure that there will be an algorithm that will help us determine EGT. Wuile adding some monitoring (VGT position and EGT pre or post turbo not a big deal) might help0 with controlling errant actuators, the main result would be increased per unit pricing... Not much of a profit builder. But we are straying fat, far away from how IAT2 is actually used... and getting a straight answer twice in a row doesn't seem to happen. While the 6.0 was borne of a need for reduced exhaust opacity, the main thrust was for the reduction of NOx emissions. They could meet the opacity requirements through careful fuel management but for control of NOx, combustion chamber temps need to be controlled or monitored in some manner.... To this end, I would consider that IAT2 is used more for measuring CAC efficiency and using that figure to compute combustion chamber inferred temps. To reduce those temps MORE EGR would be commanded rather than less.... Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted July 12, 2009 Share Posted July 12, 2009 * Total Side Note * Remember that topic on that aftermarket EGR cooler? In my research I learned that there is a correlation between NOx and opacity... I'll go to the other topic when I get a chance, I e-mailed the people who are selling that EGR cooler. This might get good because it ties into this discussion. Quote Link to comment Share on other sites More sharing options...
Damon Posted July 12, 2009 Share Posted July 12, 2009 But we are straying fat, far away from how IAT2 is actually used... and getting a straight answer twice in a row doesn't seem to happen. To reduce those temps MORE EGR would be commanded rather than less.... I think we're in agreement here, but it's hard to glean from your words. The OBDII operation summary makes clear (to me) that the EGR system is monitored and operated in part by comparing MAP to the speed density calculation. That makes IAT2 a big player, since it's very important to speed density calculations. I agree that the necessary variables can be inferred from the sensors already present. The lack of direct reading makes these existing sensors really important. And I think that the gooped IAT2 will add EGR, which I think is what you were alluding to. Quote Link to comment Share on other sites More sharing options...
Damon Posted July 12, 2009 Share Posted July 12, 2009 * Total Side Note * Remember that topic on that aftermarket EGR cooler? In my research I learned that there is a correlation between NOx and opacity... Of course it does. J1667 makes that kinda obvious. Why else would we be using opacity to emissions test vehicles that weren't really certified to an opacity standard? Do you think that the aftermarket cooler somehow alters emissions levels? To me it looked like an 03 style cooler for the 04-newer style engines. It is fun to try to think about the results we might expect if we cooled EGR too much or too little, however.... Quote Link to comment Share on other sites More sharing options...
rlchv70 Posted July 13, 2009 Share Posted July 13, 2009 Adding EGR should reduce combustion chamber temps... after all, that is what the EGR is supposed to do (reducing NOx generation). As for some of the other stuff.... if we know IAT (ambient), ambient air density (BARO), MGP (boost), IAT2 (CAC efficiency), EBP (inferred or real) and MF_DES - I am reasonably sure that there will be an algorithm that will help us determine EGT. Wuile adding some monitoring (VGT position and EGT pre or post turbo not a big deal) might help0 with controlling errant actuators, the main result would be increased per unit pricing... Not much of a profit builder. But we are straying fat, far away from how IAT2 is actually used... and getting a straight answer twice in a row doesn't seem to happen. While the 6.0 was borne of a need for reduced exhaust opacity, the main thrust was for the reduction of NOx emissions. They could meet the opacity requirements through careful fuel management but for control of NOx, combustion chamber temps need to be controlled or monitored in some manner.... To this end, I would consider that IAT2 is used more for measuring CAC efficiency and using that figure to compute combustion chamber inferred temps. To reduce those temps MORE EGR would be commanded rather than less.... IAT2 can't measure CAC efficiency since it is after the EGR valve. The heat from EGR would screw that up. Calculating combustion temperatures would take a lot of computing power. Therefore, it just uses tables based on running conditions to adjust the operating parameters. Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted July 13, 2009 Share Posted July 13, 2009 It still seems to me that there are too many variables that can affect manifold temperatures at the point of the IAT2/MAT... therefore using IAT2/MAT would not be a good choice as direct feedback for EGR valve operation. Quote Link to comment Share on other sites More sharing options...
Bruce Amacker Posted July 13, 2009 Share Posted July 13, 2009 I agree there are a lot of things that are not constant with this sensor, but one thing is constant- when the EGR is commanded open, (no matter what the IAT2 reads) the IAT2 temp should rise. Good Luck! Quote Link to comment Share on other sites More sharing options...
Damon Posted July 14, 2009 Share Posted July 14, 2009 It still seems to me that there are too many variables that can affect manifold temperatures at the point of the IAT2/MAT... therefore using IAT2/MAT would not be a good choice as direct feedback for EGR valve operation. Name some variables that can't be cross-checked and validated by the other sensors. Quote Link to comment Share on other sites More sharing options...
Jeff_E Posted July 14, 2009 Share Posted July 14, 2009 Quote: Name some variables that can't be cross-checked and validated by the other sensors. Well, if your only asking about IAT2 variables- Carbon build up on the thermistor definately comes to mind as a variable, and there isn't another air temp sensor post turbo for the PCM to compare coherency values with. But to speak more broadly... If your ICP sensor shorts out there isn't another sensor to verify High oil pressure and provide feedback to the PCM to control the IPR. If your oil sender fails there is no redundant oil pressure sensor to validate lube oil pressure at the gauge. If your MAF sensor fails there is no way to accurately measure air volume. Surely the TP and MAP could be used as speed density inputs much like they are on older gas engines, but it may not be accurate enough to meet current emissions standards-which is just as much a part of our job as just making them run. If your ECT sensor fails there is no way for the PCM to reliably determine engine temp, it could look at EOT to get a general idea, but a restricted oil cooler could cause a very inaccurate reading and affect fuel control. If your CKP fails you will lose your RPM signal on a 6.0 even with a working CMP (had one of these this week) If your AP sensor fails there is no way for the PCM to determine driver demand. If the WIF sensor fails the driver won't know if there is actually water in the fuel. If the EGR internal position sensor fails, there is no way for the PCM to know egr position... Though it may at least be able to determine whether flow is occurring with the use of IAT2 If a wheel speed sensor fails the ECU has no way of knowing the speed of that wheel. If a TPMS sensor fails the ECU has no way of knowing the pressure of that tire. If the OCS system fails the RCM will be unable to make a firing decision for the passenger air bag in the event of a collision. If your PSP sensor, or ACCS fail, the PCM won't know to kick the idle up to compensate for the increased load. If the visctronic fan clutch internal rpm sensor fails, the PCM won't know fan speed. If a parking aid sensor fails, the system shuts off. If an optical sensor fails the automatic head lamps won't work. If the in vehicle air temp sensor fails, the EATC will be unable to maintain the commanded cabin temperature. If the sensor inside the electric vacuum pump fails, the pump won't know to shut off and eventually burn out rendering the ESOF hubs inop and the climate control stuck in defrost mode. If a door ajar switch fails, it will cause all kinds of problems for SJB strategies... To say nothing of how much the dome lamp and door ajar light will piss you off. I could go on, but this is enough to remind me why I love my 1976 F150 so much - It don't need no freaking IAT!!! Quote Link to comment Share on other sites More sharing options...
cbriggs Posted July 14, 2009 Share Posted July 14, 2009 I actually had an experience with a non responsive iat2 sensor causing a severe over active egr valve last week. Smoked (black) on tip in consistantly when warmed up, egr cmnd shot to 100% an every tip in. Pissed around for a few hours, and noticed if i took command of egr @ 0%, concern was gone. Also found that @ 100% egr command, egr vp @4.5v, driving under load, iat2 was only 10`c warmer than iat 1. Cleaned iat 2 sensor and concern was 100% fixed. This was on a 2006 with 85000 kms. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.