Decel fuel delivery, stoich @ 0% tps? WTF!
Nov 23, 2006, 10:46 AM
#17
eficker,
I know exactly what you are talking about.
I think it may be something to do with either the 9's or even later, like 2005 8's. People have complained on these cars that when you let off the gas, the throttle seems to hang a bit, like fuel is still being delivered...I wonder if this is somehow related to what your are experiencing.
At 0% throttle, in gear, you should get coasting fuel cut, which means that the injectors shut off completely and your wideband would read it's leanest value. Why your car doesn't do this until 3000RPM on decel in gear, I don't know. Perhaps it is a IX thing, but if your wideband is reading stoich then the fuel is getting burned. You wouldn't get a stoich reading if the fuel was just getting dumped out of the exhaust.
That is interesting though. Can you do a log for us: Go up to like 6000RPM and then just let off the gas. Log IPW....that will tell us where exactly your ECU is shutting off the injectors and whether they are not getting shut off above 3000 RPM.
Eric
I know exactly what you are talking about.
I think it may be something to do with either the 9's or even later, like 2005 8's. People have complained on these cars that when you let off the gas, the throttle seems to hang a bit, like fuel is still being delivered...I wonder if this is somehow related to what your are experiencing.
At 0% throttle, in gear, you should get coasting fuel cut, which means that the injectors shut off completely and your wideband would read it's leanest value. Why your car doesn't do this until 3000RPM on decel in gear, I don't know. Perhaps it is a IX thing, but if your wideband is reading stoich then the fuel is getting burned. You wouldn't get a stoich reading if the fuel was just getting dumped out of the exhaust.
That is interesting though. Can you do a log for us: Go up to like 6000RPM and then just let off the gas. Log IPW....that will tell us where exactly your ECU is shutting off the injectors and whether they are not getting shut off above 3000 RPM.
Eric
Nov 23, 2006, 10:50 AM
#19
Evolving Member
iTrader: (3)
Join Date: Mar 2005
Location: Grand Rapids, MI
Posts: 222
Likes: 0
Received 0 Likes
on
0 Posts
Jumping in a little late here, but I wonder if this could be occurring as a result of the "cruise control" engine decel problem that others have described. Here's a thread about it...
https://www.evolutionm.net/forums/sh...ad.php?t=74085
It's been a while since I've read up on this problem, but I have experienced it on my IX. It seems like the RPMs fall really slowly above ~3500 RPM, but then below that the engine sound changes and revs fall much faster.
https://www.evolutionm.net/forums/sh...ad.php?t=74085
It's been a while since I've read up on this problem, but I have experienced it on my IX. It seems like the RPMs fall really slowly above ~3500 RPM, but then below that the engine sound changes and revs fall much faster.
Nov 23, 2006, 10:53 AM
#20
Originally Posted by evo_08
i have an innovete lc1 and at decel it says like 20.6
Also, fyi, that 20.6 or so that you are seeing with your LC-1 is % Oxygen. The LC-1 swiches from AFR to % O2 when no fuel is being burned.
Eric
Nov 23, 2006, 10:57 AM
#21
Evolved Member
iTrader: (1)
Join Date: Jun 2003
Location: bush LA
Posts: 976
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by l2r99gst
He isn't asking what people's widebands read at decel. He is just saying that he isn't getting coasting fuel cut where he thought he would.
Also, fyi, that 20.6 or so that you are seeing with your LC-1 is % Oxygen. The LC-1 swiches from AFR to % O2 when no fuel is being burned.
Eric
Also, fyi, that 20.6 or so that you are seeing with your LC-1 is % Oxygen. The LC-1 swiches from AFR to % O2 when no fuel is being burned.
Eric
Nov 23, 2006, 11:22 AM
#22
Evolving Member
Join Date: Aug 2002
Location: FT.LAUDERDALE FL
Posts: 283
Likes: 0
Received 0 Likes
on
0 Posts
Not trying to sound off threadish but evo manufacturers always make improvement to the next evo , I personally like this improvement because when im crusing at 110mph and I lift my foot off the trottle i don't want the car to nose dive (engine rebound stress) unless im on the breaks.
However this mod by mitsu may cause afr's to read different than in evo8s and 7s, I guess you will have to learn to read it a little differently.
GOOD IMPROVEMENT not a problem.
However this mod by mitsu may cause afr's to read different than in evo8s and 7s, I guess you will have to learn to read it a little differently.
GOOD IMPROVEMENT not a problem.
Nov 23, 2006, 01:27 PM
#23
Originally Posted by l2r99gst
eficker,
I know exactly what you are talking about.
I think it may be something to do with either the 9's or even later, like 2005 8's. People have complained on these cars that when you let off the gas, the throttle seems to hang a bit, like fuel is still being delivered...I wonder if this is somehow related to what your are experiencing.
At 0% throttle, in gear, you should get coasting fuel cut, which means that the injectors shut off completely and your wideband would read it's leanest value. Why your car doesn't do this until 3000RPM on decel in gear, I don't know. Perhaps it is a IX thing, but if your wideband is reading stoich then the fuel is getting burned. You wouldn't get a stoich reading if the fuel was just getting dumped out of the exhaust.
That is interesting though. Can you do a log for us: Go up to like 6000RPM and then just let off the gas. Log IPW....that will tell us where exactly your ECU is shutting off the injectors and whether they are not getting shut off above 3000 RPM.
Eric
I know exactly what you are talking about.
I think it may be something to do with either the 9's or even later, like 2005 8's. People have complained on these cars that when you let off the gas, the throttle seems to hang a bit, like fuel is still being delivered...I wonder if this is somehow related to what your are experiencing.
At 0% throttle, in gear, you should get coasting fuel cut, which means that the injectors shut off completely and your wideband would read it's leanest value. Why your car doesn't do this until 3000RPM on decel in gear, I don't know. Perhaps it is a IX thing, but if your wideband is reading stoich then the fuel is getting burned. You wouldn't get a stoich reading if the fuel was just getting dumped out of the exhaust.
That is interesting though. Can you do a log for us: Go up to like 6000RPM and then just let off the gas. Log IPW....that will tell us where exactly your ECU is shutting off the injectors and whether they are not getting shut off above 3000 RPM.
Eric
Originally Posted by KINGEVO7
Not trying to sound off threadish but evo manufacturers always make improvement to the next evo , I personally like this improvement because when im crusing at 110mph and I lift my foot off the trottle i don't want the car to nose dive (engine rebound stress) unless im on the breaks.
While road racing, i do not want my decel "cruise control" to fight my braking (at the limit mind you) and push me straight through a corner.
Personally i hate this programming "glitch" or whatever it is. When i let off the throttle, i want the motor to slow the car down, thats normal, not continue propelling me towards the car in front of me.
I will go do a log and find out if it is related to the throttle return spring, and see what else is going on. brb
Nov 23, 2006, 02:17 PM
#25
No wideband issues here, working perfectly, as is yours i would suspect.
I did some logging and attached it here. Looks like tps, even at off throttle is around 12%. Is that normal? Seems like it should be 0%, or at least close to it.
What are others reading?
Also, while this problem may be related to boost, the boost itself is not the cause.
It will do it when I get into any level of boost (even low levels) then let off the throttle. If i rev it up without any boost (staying in vacuum) it does not seem to happen.
I am on stock boost levels (~20psi).
I'm a little worried about the 12% tps reading when I am off the pedal, but also the fact that this does not happen when i rev it up in vacuum is weird as well.
Someone suggested that for the wb to read an afr, the fuel actually has to be burned, so if this is the case, then is the motor actually firing on decel?
Jack? Where you at? Any ideas?
I did some logging and attached it here. Looks like tps, even at off throttle is around 12%. Is that normal? Seems like it should be 0%, or at least close to it.
What are others reading?
Also, while this problem may be related to boost, the boost itself is not the cause.
It will do it when I get into any level of boost (even low levels) then let off the throttle. If i rev it up without any boost (staying in vacuum) it does not seem to happen.
I am on stock boost levels (~20psi).
I'm a little worried about the 12% tps reading when I am off the pedal, but also the fact that this does not happen when i rev it up in vacuum is weird as well.
Someone suggested that for the wb to read an afr, the fuel actually has to be burned, so if this is the case, then is the motor actually firing on decel?
Jack? Where you at? Any ideas?
Last edited by eficker; Nov 23, 2006 at 02:21 PM.
Nov 23, 2006, 02:25 PM
#26
Originally Posted by eficker
I'm a little worried about the 12% tps reading when I am off the pedal, but also the fact that this does not happen when i rev it up in vacuum is weird as well.
Someone suggested that for the wb to read an afr, the fuel actually has to be burned, so if this is the case, then is the motor actually firing on decel?
Jack? Where you at? Any ideas?
Someone suggested that for the wb to read an afr, the fuel actually has to be burned, so if this is the case, then is the motor actually firing on decel?
Jack? Where you at? Any ideas?
Yes, the engine is still firing. The coils/spark plugs don't get shut off, just the injectors, or in your case, not the injectors.
It's definitely something in the IX's then. There has to be a table somewhere to adjust it.
Eric
Nov 23, 2006, 02:41 PM
#28
Looking at your log, towards the end where you go WOT to about 5700 RPM and then let off the gas, the injectors still fire for a second or so, giving you a few more rows of data with a postive IPW.
Then, the injectors do shut off ( 0 IPW) from 5250 to about 4300 RPM. Then at 4300 RPM they turn back on, until about 3800 RPM (although it looks like you shifted during decel to a lower gear). Then they stay shut off until they are supposed to come back on, just above idle (1000 RPM in your log).
So, the injectors definitely are firing through a certain RPM range even when you are in decel in gear.
Eric
Then, the injectors do shut off ( 0 IPW) from 5250 to about 4300 RPM. Then at 4300 RPM they turn back on, until about 3800 RPM (although it looks like you shifted during decel to a lower gear). Then they stay shut off until they are supposed to come back on, just above idle (1000 RPM in your log).
So, the injectors definitely are firing through a certain RPM range even when you are in decel in gear.
Eric
Last edited by l2r99gst; Nov 23, 2006 at 02:57 PM.
Nov 23, 2006, 06:46 PM
#29
Originally Posted by l2r99gst
Looking at your log, towards the end where you go WOT to about 5700 RPM and then let off the gas, the injectors still fire for a second or so, giving you a few more rows of data with a postive IPW.
Then, the injectors do shut off ( 0 IPW) from 5250 to about 4300 RPM. Then at 4300 RPM they turn back on, until about 3800 RPM (although it looks like you shifted during decel to a lower gear). Then they stay shut off until they are supposed to come back on, just above idle (1000 RPM in your log).
So, the injectors definitely are firing through a certain RPM range even when you are in decel in gear.
Eric
Then, the injectors do shut off ( 0 IPW) from 5250 to about 4300 RPM. Then at 4300 RPM they turn back on, until about 3800 RPM (although it looks like you shifted during decel to a lower gear). Then they stay shut off until they are supposed to come back on, just above idle (1000 RPM in your log).
So, the injectors definitely are firing through a certain RPM range even when you are in decel in gear.
Eric
Yeah, its totally weird. There has got to be some decel table that we dont have access to yet that will solve this issue. Just seems that if i'm off the throttle, no fuel should be delivered.
That log was just on some short runs on surface streets. When i'm on the freeway it can happen for quite a while as i decel from passing someone, etc.
Nov 23, 2006, 07:22 PM
#30
The IX's do this for emission purposes. By decelerating the engine slowly, the pollutants are decreased in the exhaust via of not richening the hell out of the mixture. It sucks. Very annoying. But I must say, I think the air pump Subaru added to the sti's for emissions is much worse.