Air/Fuel Problems here
Registered User
Joined: Nov 2006
Posts: 1,284
Likes: 0
From: tampa florida
only way you can tell if fuel preesure drops is under wot under a load, i do that on the dyno! to dangerous hanging out the engine bay going down the road. I have also installed temp fuel pressure guage to monitor while driving.
Registered User
Joined: Oct 2004
Posts: 1,631
Likes: 0
From: Southern Maryland
Dam... Could be a failing fuel injector or injectors. From what you have most recently described, it's probably not your 02 sensor unless your tune is totally wack. Try checking to make sure the harness is plugged 100% into the ECU. It can cause wired problems like this sometimes. If a friend has another EMS you can borrow to see if that's the problem, you could try that.
Joined: May 2005
Posts: 4,331
Likes: 0
From: Tallahassee, FL
Plug that bad-boy into your laptop (assuming its AEM). See if your injectors are still firing. Fuel pressure does not tell you whether the pressure is being relieved (via injection) or is just sitting there, not spraying). Other than fuel, it would have to be timing, right (to affect AFR at a given RPM/load)? You can probably diagnose it yourself, provided its AEM software, and you have a computer/serial cable...
No CEL's? Its not uncommon to see readings of 16+ on unloaded decels. At idle, that is an issue, IMO.
I would not drive it, even like a 90 y/o man, if your AFR's are in the 17's+ at idle. You are asking for detonation. You MIGHT be able to get away with it if the AFR's are tolerable in the 3-4k range unloaded... You could drive with a heavy foot (to keep the high load fuel map settings) to keep the AFRs down. When you have to stop, idle it up to where ever is safe.... it probably would not even work, as you would only be giving it like 5% throttle to hover there, which is probably right smack in the middle of the problem area on the fuel map (assuming tuning is the issue, and not a failed injector).
But then again, I am no tuner...
John
No CEL's? Its not uncommon to see readings of 16+ on unloaded decels. At idle, that is an issue, IMO.
I would not drive it, even like a 90 y/o man, if your AFR's are in the 17's+ at idle. You are asking for detonation. You MIGHT be able to get away with it if the AFR's are tolerable in the 3-4k range unloaded... You could drive with a heavy foot (to keep the high load fuel map settings) to keep the AFRs down. When you have to stop, idle it up to where ever is safe.... it probably would not even work, as you would only be giving it like 5% throttle to hover there, which is probably right smack in the middle of the problem area on the fuel map (assuming tuning is the issue, and not a failed injector).
But then again, I am no tuner...
John
Registered User
Joined: Nov 2006
Posts: 1,284
Likes: 0
From: tampa florida
he is using a aem 1052, i have had several ignition/coil controls go bad in these, but that would be a extream rich unburnt fuel, i have heard injector drivers in the ems going bad, it has 2 more so you could repin plug and change map/tune setup. At this point i would have a tuner plug in and see what is going on, you have plenty of injector to be making 500+hp, how full is your fuel tank? I have had several cars have lean conditions and they were driving around with very little fuel in the tank, filled up with some good fuel and problem went away. I think you have a bad fuel pump!
Joined: May 2005
Posts: 4,331
Likes: 0
From: Tallahassee, FL
I wonder if he is running low on fuel too....
Have you had the gas gauge all the way down to Empty since you did the fuel pump install? If you used the Walbro fuel sock vs. the OEM one, the fuel level float would bind up (Walbro sock is differently shaped, and gets in the way)... Showing that you had about 1/4 tank of gas, even when empty.
John
Have you had the gas gauge all the way down to Empty since you did the fuel pump install? If you used the Walbro fuel sock vs. the OEM one, the fuel level float would bind up (Walbro sock is differently shaped, and gets in the way)... Showing that you had about 1/4 tank of gas, even when empty.
John
Registered User
Joined: Feb 2004
Posts: 591
Likes: 0
From: Lafayette, LA
Assume you have EMS, your tune was working fine before the temps got cold, and nothing has broken or changed in the meantime. You could try to adjust the intake air temp (IAT) correction table. Add more fuel at the appropriate low temp cell.
JWA4378, it may be that you are currently adding too much fuel trim in the low temp cell(s) in the IAT correction table. Again, assuming your tune worked fine in warmer weather and nothing else has changed.
WARNING: Following is my long-winded take on EMS tuning 101.
Anyone with more experience (or education) please tell me where I made any mistakes. I'm no tuner either, well at least not on cars. But I've tuned continuous-combustion equipment aplenty. Theory is the same. Power is proportional to fuel flow rate, which is proportional (by A/F ratio) to air flow rate. And air flow rate itself is proportional to displacement, MAP, and RPM; and inversely proportional to IAT.
A little math theory to explain the base map calculations. For a fixed displacement (2.0L or 2.2L or anything) positive displacement type pump (engine), double the RPM and you double the mass flow rate (ignored VE). The reason the base maps can easily be calculated is due to the linear relationships between pressure, temp, volume, and mass. This is called the Ideal Gas Law, and it applies to air. Anyone who took a thermodynamics class got this grilled into them. In a fixed volume, to double the pressure you must double the mass of fluid. For a fixed pressure, double the temp and you cut the mass of fluid in half. So that is where the pressure and temperature ratios used come from.
The main fuel lookup table (injector duty cycle) is dependent on MAP & RPM, but neither of these two sensors compensate for changes to air density. When it gets cold outside the air gets more dense, and vice-versa. The IAT sensor measures this temperature, and has fuel trim cells in it's correction table that allow you to compensate for the change in air density (and thus air mass). It effectively adds a 3rd dimension (IAT) to the fuel look-up table. But instead of trying to show a 3D table on a 2D screen, EMS has IAT as a separate table from MAP / RPM. Since it's a separate table (and no one can control ambient temp anyway) I guess most people rarely look at or tune the IAT correction table.
I believe the air/fuel trim values in the IAT table should be linear, since it is designed to correct for a linear property (change in air density with temperature). IAT correction numbers could be base-mapped once it has a good tune at any temp (but you must know that temp). Use a slope proportional to inverse of absolute temp ratio (IAT@good tune+460) / (IAT+460) plus/minus whatever offset is needed to get the line to pass thru the good tune point. I am assuming that (like main table) a higher number in IAT correction table = more fuel. If that's backwards, then invert the numbers in the temp ratio fraction above (switch top to bottom) and it will work. I'm also assuming that your IAT unit is deg F (-460 Rankine = absolute zero). For deg C use 273 instead of 460 (-273 Celcius = absolute zero).
Then fine tune at a cold air temp (by changing appropriate IAT correction cell) to get it just right. You should be able to fill in the remaining IAT correction cells to stay on the same line described by these two points (new fine tune point and original good tune point). Theoretically, that should give you a good tune at all IATs w/o having to fine tune at all those temps. It's hard to control IAT for tuning, unlike RPM & MAP (which can easily be controlled by throttle, gear & load).
This method is similar to how the fuel table is initially filled in when adding boost to an N/A car. Table can be base-mapped before any tuning by multiplying a known good tune's fuel cell value at full load [when @ WOT (max TPS), @ max RPM, and no boost (MAP=Patm)] by the max absolute boost pressure ratio expected (PSIG@maxboost+Patm)/(Patm). Patm =14.7psia at sea level. Then to compensate for required A/F change, multiply this number by ratio of (AF@WOT_NA) / (AFwanted@boost). This gives you fuel cell value at full boost and max RPM (same rpm that the good tune fuel point was taken at). Then fill in cells between full boost and atmospheric by linear interpolation. EMS even has a one-button wizard for this linear fill-in. Finally, get it fine tuned on dyno or street tune.
All this math is only to get a good start at the base map. You definitely need to tune and log A/F, RPM, etc. to ensure safe operation. Whether on a dyno or street tune. But if you get the base map close, it should take less time to do the actual tuning.
JWA4378, it may be that you are currently adding too much fuel trim in the low temp cell(s) in the IAT correction table. Again, assuming your tune worked fine in warmer weather and nothing else has changed.
WARNING: Following is my long-winded take on EMS tuning 101.
Anyone with more experience (or education) please tell me where I made any mistakes. I'm no tuner either, well at least not on cars. But I've tuned continuous-combustion equipment aplenty. Theory is the same. Power is proportional to fuel flow rate, which is proportional (by A/F ratio) to air flow rate. And air flow rate itself is proportional to displacement, MAP, and RPM; and inversely proportional to IAT.
A little math theory to explain the base map calculations. For a fixed displacement (2.0L or 2.2L or anything) positive displacement type pump (engine), double the RPM and you double the mass flow rate (ignored VE). The reason the base maps can easily be calculated is due to the linear relationships between pressure, temp, volume, and mass. This is called the Ideal Gas Law, and it applies to air. Anyone who took a thermodynamics class got this grilled into them. In a fixed volume, to double the pressure you must double the mass of fluid. For a fixed pressure, double the temp and you cut the mass of fluid in half. So that is where the pressure and temperature ratios used come from.
The main fuel lookup table (injector duty cycle) is dependent on MAP & RPM, but neither of these two sensors compensate for changes to air density. When it gets cold outside the air gets more dense, and vice-versa. The IAT sensor measures this temperature, and has fuel trim cells in it's correction table that allow you to compensate for the change in air density (and thus air mass). It effectively adds a 3rd dimension (IAT) to the fuel look-up table. But instead of trying to show a 3D table on a 2D screen, EMS has IAT as a separate table from MAP / RPM. Since it's a separate table (and no one can control ambient temp anyway) I guess most people rarely look at or tune the IAT correction table.
I believe the air/fuel trim values in the IAT table should be linear, since it is designed to correct for a linear property (change in air density with temperature). IAT correction numbers could be base-mapped once it has a good tune at any temp (but you must know that temp). Use a slope proportional to inverse of absolute temp ratio (IAT@good tune+460) / (IAT+460) plus/minus whatever offset is needed to get the line to pass thru the good tune point. I am assuming that (like main table) a higher number in IAT correction table = more fuel. If that's backwards, then invert the numbers in the temp ratio fraction above (switch top to bottom) and it will work. I'm also assuming that your IAT unit is deg F (-460 Rankine = absolute zero). For deg C use 273 instead of 460 (-273 Celcius = absolute zero).
Then fine tune at a cold air temp (by changing appropriate IAT correction cell) to get it just right. You should be able to fill in the remaining IAT correction cells to stay on the same line described by these two points (new fine tune point and original good tune point). Theoretically, that should give you a good tune at all IATs w/o having to fine tune at all those temps. It's hard to control IAT for tuning, unlike RPM & MAP (which can easily be controlled by throttle, gear & load).
This method is similar to how the fuel table is initially filled in when adding boost to an N/A car. Table can be base-mapped before any tuning by multiplying a known good tune's fuel cell value at full load [when @ WOT (max TPS), @ max RPM, and no boost (MAP=Patm)] by the max absolute boost pressure ratio expected (PSIG@maxboost+Patm)/(Patm). Patm =14.7psia at sea level. Then to compensate for required A/F change, multiply this number by ratio of (AF@WOT_NA) / (AFwanted@boost). This gives you fuel cell value at full boost and max RPM (same rpm that the good tune fuel point was taken at). Then fill in cells between full boost and atmospheric by linear interpolation. EMS even has a one-button wizard for this linear fill-in. Finally, get it fine tuned on dyno or street tune.
All this math is only to get a good start at the base map. You definitely need to tune and log A/F, RPM, etc. to ensure safe operation. Whether on a dyno or street tune. But if you get the base map close, it should take less time to do the actual tuning.
Community Organizer
Joined: Jun 2007
Posts: 31,070
Likes: 566
[QUOTE=REVHIR,Nov 9 2008, 08:28 PM] Well. the car had been running very good lately until the other day. No smoke out of exhuast. Thankfully anymore after my turbo seal rebuild. I have been noticing my air/fuel ratio numbers at cruising speed have been getting wayyyy out of hand. In 5th gear and around 4k rpm the UEGO is reporting 16 even 17 with the car hesitating and like a burping effect. Once I step on the gas the UEGO shows green and around 12's while building boost. I checked all lines and pipes. Everythings is clear and dandy. The car Idles at 13 sometimes 14.5 all the way to 15. Does not go into red in idle. It is concerning how it only does it at cruising speeds that it drops to severe red area. 17's! almost off the charts. What do you guys think is going on here? Hopefully nothing expensive!