idle isnt rich anymore, YES!
03-20-2005, 08:08 PM
#1
idle isnt rich anymore, YES! ok well my idle was pretty rich sometimes (about -10 or so) and well my eyes would hurt around my car lol i was checking out my rail pressue becasue of other problems and noticed at idle i was at 62 psi and would gradually drop to about 59 at 0 vacuum. well in my excel file i have that i found on here, has the pressure considered constant when its calculating the flow rate in g/sec. well that was at 58, so the car actually sees an extra 4 psi. so i put that in my excel file and now at idle the fuel trims are about -1 or -2, the car runs much smoother and responds much faster.
i assumed people have done this before, hell for all i know this might not be a good idea lol, but i figured i would post anyway since every time i asked about idle fuel trims being high noone seemed to help giving me info about how to get them down. let me know what you guys think, and if you have done this
i assumed people have done this before, hell for all i know this might not be a good idea lol, but i figured i would post anyway since every time i asked about idle fuel trims being high noone seemed to help giving me info about how to get them down. let me know what you guys think, and if you have done this
03-20-2005, 08:57 PM
#2
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I'm going to give this a shot on mine but first I need some sort or gauge that will work on the fuel rail! Does it need a special one or just something like a tire gauge?
03-20-2005, 09:38 PM
#5
What kind of fuel pump do you have?
I just installed my autometer gauge today, and it reads right on the money 58 psi, it does drop though under acceleration.
Wondering if my racetronix pump will raise that in the future when I install it.
Ryan
I just installed my autometer gauge today, and it reads right on the money 58 psi, it does drop though under acceleration.
Wondering if my racetronix pump will raise that in the future when I install it.
Ryan
03-20-2005, 09:38 PM
#6
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Wow... take soe time off and some peeps come up with some wild and crazy stuff!!! 
ok ok ok, I've also been plagued with negative trims at idle and TPS letoff conditions. So essentially what is being said here is that it is taken for granted that the fuel system is constantly running at 58 psi when in actuality could be running above or below that, therefore screwing up the flow rates a little bit? Neat...
Ok so how does the IFR table get referenced? at 0 VAC that's WOT right? So i just find out at what MAP I'm having trim trouble with and the correlate it to vaccuum pressure in the table, find what psi i'm really running, and adjust it slightly from there? Although my trim trouble seems to be more bounded by rpms than MAP.
Obviously idle sucks, but the NW corner and outline of my trim histogram always has negative trimming going on. But at 60kpa MAP, 2000 rpms, my trims are just fine, but 60kpa MAP, 900 rpms, my idle is like -10 and such. soooo what gives?
ok ok ok, I've also been plagued with negative trims at idle and TPS letoff conditions. So essentially what is being said here is that it is taken for granted that the fuel system is constantly running at 58 psi when in actuality could be running above or below that, therefore screwing up the flow rates a little bit? Neat...Ok so how does the IFR table get referenced? at 0 VAC that's WOT right? So i just find out at what MAP I'm having trim trouble with and the correlate it to vaccuum pressure in the table, find what psi i'm really running, and adjust it slightly from there? Although my trim trouble seems to be more bounded by rpms than MAP.
Obviously idle sucks, but the NW corner and outline of my trim histogram always has negative trimming going on. But at 60kpa MAP, 2000 rpms, my trims are just fine, but 60kpa MAP, 900 rpms, my idle is like -10 and such. soooo what gives?
03-20-2005, 10:03 PM
#7
my idle is great now, ill have to mess with the table more, if you have a pressure gauge put it on the line and have the computer with you, try and open the throttle to get a certain map and read the gauge at that pressure. seems like the pressure is just high at about 20-30 maybe 40 MAP which is 80, 70, and 60 respectively. yeah 0 on the IFR table is WOT which is atmospheric pressure since there is no vacuum. the map is absolute and zeroed at atmospheric press so you take the map off of atm. press....20 MAP is really -20 then add 100 and you get 80 kpa vacuum. you may have known this already but maybe itll help others
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03-20-2005, 10:09 PM
#8
i did an idle log of my car when she warmed up and the histogram showed about -1 or -2 on the fuel trims and thats from about -10 or so. the motor is SOOOOO much more smooth now at idle, im still fighting pump issues (i think i have a bad check valve) so my idle was screwy, tightened some things up and im gonna check tomorrow to see if it is now only limited to start up.
slow:
i put a racetronix kit in and my idle pressure is 62 psi, when i rev the car a little it drops to about 60 (im not sure on the exact numbers i just made a table up that is linear from 59.5 to 62 psi) and when i am sitting still and hold it wide open real fast the pressure only goes to about 59, not too bad. i was having problems before but i think that was due to a loose line to the sender. the clamp wasnt tight and i would imagine that would cause some issues, the fuel pressure was out of wack when it was loose and now the pressure is constant at idle.
could that little bit of a loose line cause idle problems and wieird numbers. the fuel pressure was going back and forth from 62-64 at idle and now it doesnt move from 62.
slow:
i put a racetronix kit in and my idle pressure is 62 psi, when i rev the car a little it drops to about 60 (im not sure on the exact numbers i just made a table up that is linear from 59.5 to 62 psi) and when i am sitting still and hold it wide open real fast the pressure only goes to about 59, not too bad. i was having problems before but i think that was due to a loose line to the sender. the clamp wasnt tight and i would imagine that would cause some issues, the fuel pressure was out of wack when it was loose and now the pressure is constant at idle.
could that little bit of a loose line cause idle problems and wieird numbers. the fuel pressure was going back and forth from 62-64 at idle and now it doesnt move from 62.
03-20-2005, 10:14 PM
#9
i have the excel file that makes it easy and if anyone can post it up on here or tell me how i can get it so everyone can d/l it then i will get it up. i didnt make it up, someone with some time on their hands did though. lol i checked it with the factory numbers and the IFR's were EXACTLY the same to the 5th decimal
03-20-2005, 10:19 PM
#10
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Originally Posted by WS6FirebirdTA00
my idle is great now, ill have to mess with the table more, if you have a pressure gauge put it on the line and have the computer with you, try and open the throttle to get a certain map and read the gauge at that pressure. seems like the pressure is just high at about 20-30 maybe 40 MAP which is 80, 70, and 60 respectively.
At 20-30-40 MAP I could be at idle, 1200 rpms, 1500 rpms, 2000 rpms
I'm not having trim problems after 1200 rpms really. it's all mainly below 1400 rpms. so if I change the flow rate at let's say 40kpa MAP then wouldn't that screw my other rpm ranges at 40kpa up?
03-20-2005, 10:37 PM
#11
ok well the rpm doesnt matter, i mean we have talked i knwo your not dumb but let me explain this like you are so that everyone else will understand too lol
the fuel injectors are rated at, well ill use my car for example. at 58 psi they flow 43.65 lb/hr. in this excel sheet i put that in as the current injector rating. the way our computers have it is that the rail keeps pressure at 58 psi at idle, part throttle or WOT when in reality the car will never see a constant pressure (well not in most applicatons) the way it works is as vacuum goes up the g/sec increase as you can see in the table. so if i have 60 psi in my rail and 20 vacuum, the change in pressure is 80 psi, so thats like putting the injectors on a flow machine and putting 80 psi to them and seeing how many g/sec they flow. so that means at 20 map, no matter what rpm that is how much pressure (80 psi) the injectors will actually see, this is not rpm dependent. at WOT there is no vacuum so there is no "sucking" of fuel from the injectors so the only pressure they see is the rail pressure of what you read at WOT. any vacuum has to be considered extra pressure because it sucks fuel out, its all about change in pressure not the number you are gettin on the gauge. let me post this up and think, i may have not made this as simple as i wanted
ok so in summary, the pressure the injector see is:
*** Vacuum reading + Rail pressure = Total pressure
the vacuum reading is in the table and is:
*** Atmospheric pressure - MAP reading = Vacuum reading
so as the MAP, the total change in pressure fluctuates, it is not a constant number, which from the factory, our computers think the rail pressure is constant. which is why at 20 kpa MAP the car runs rich, the computer thinks the pressure is lower than it actually is, but in reality the injectors are flowing a lot of fuel, making the car rich. no matter what rpm you are at the injector flow rate is constant. i would imagine the VE would need to be reworked after this too. this means the ve table is actually compensating for the injecotrs flowing more fuel then the computer thinks they are. once you get this all set up right you should be able to tune the ve a lot better. i havent done this yet, im gonna do it tomorrow night, along with the MAF being off of the car because im not gonna mess with that yet. there are too many factors that can throw off the maf and i dont want to start thinking about a calibration that would be correct. i only want one error in my system, the ve table, not 2 lol makes it easier. plus i figured out the maf changes dependent on temp and humidity and if you tune for a neutral day it shouldnt change too much, havent tested this yet but i will soon. from 30 to 60 deg my trims only change by about 1 or 2%. sorry lots of rambling ill stop now. any questions just post up
the fuel injectors are rated at, well ill use my car for example. at 58 psi they flow 43.65 lb/hr. in this excel sheet i put that in as the current injector rating. the way our computers have it is that the rail keeps pressure at 58 psi at idle, part throttle or WOT when in reality the car will never see a constant pressure (well not in most applicatons) the way it works is as vacuum goes up the g/sec increase as you can see in the table. so if i have 60 psi in my rail and 20 vacuum, the change in pressure is 80 psi, so thats like putting the injectors on a flow machine and putting 80 psi to them and seeing how many g/sec they flow. so that means at 20 map, no matter what rpm that is how much pressure (80 psi) the injectors will actually see, this is not rpm dependent. at WOT there is no vacuum so there is no "sucking" of fuel from the injectors so the only pressure they see is the rail pressure of what you read at WOT. any vacuum has to be considered extra pressure because it sucks fuel out, its all about change in pressure not the number you are gettin on the gauge. let me post this up and think, i may have not made this as simple as i wanted
ok so in summary, the pressure the injector see is:
*** Vacuum reading + Rail pressure = Total pressure
the vacuum reading is in the table and is:
*** Atmospheric pressure - MAP reading = Vacuum reading
so as the MAP, the total change in pressure fluctuates, it is not a constant number, which from the factory, our computers think the rail pressure is constant. which is why at 20 kpa MAP the car runs rich, the computer thinks the pressure is lower than it actually is, but in reality the injectors are flowing a lot of fuel, making the car rich. no matter what rpm you are at the injector flow rate is constant. i would imagine the VE would need to be reworked after this too. this means the ve table is actually compensating for the injecotrs flowing more fuel then the computer thinks they are. once you get this all set up right you should be able to tune the ve a lot better. i havent done this yet, im gonna do it tomorrow night, along with the MAF being off of the car because im not gonna mess with that yet. there are too many factors that can throw off the maf and i dont want to start thinking about a calibration that would be correct. i only want one error in my system, the ve table, not 2 lol makes it easier. plus i figured out the maf changes dependent on temp and humidity and if you tune for a neutral day it shouldnt change too much, havent tested this yet but i will soon. from 30 to 60 deg my trims only change by about 1 or 2%. sorry lots of rambling ill stop now. any questions just post up
Last edited by WS6FirebirdTA00; 03-20-2005 at 11:06 PM.
03-20-2005, 11:39 PM
#12
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Originally Posted by WS6FirebirdTA00
which is why at 20 kpa MAP the car runs rich, the computer thinks the pressure is lower than it actually is, but in reality the injectors are flowing a lot of fuel, making the car rich. no matter what rpm you are at the injector flow rate is constant. i would imagine the VE would need to be reworked after this too. this means the ve table is actually compensating for the injecotrs flowing more fuel then the computer thinks they are. once you get this all set up right you should be able to tune the ve a lot better.
A look at my trimming problems:
The area I have circled when I'm above let's say 30 mph and beyond 30 MAP my scanner will read -1s and 0s for my trims. If i go below either of those thresholds, i get -11s, -10s, -8s, and such, thus creating an outer rim of "richness" that by averages, blends into my main part throttle area. But the scanner reads real time a night and day change. When cruising on the highway, I'm within normal trim values, when coming to a stop or back to idle, my trims go waaaaaaaaay negative. And this is experiencing the same vaccuum pressures same rpms, just different loads.
This injector thing may have worked for you but will it work for me? And now that I'm all curious again, is anyone else having this same problem?
03-20-2005, 11:52 PM
#13
let me ponder on this a little bit lol
ok you make a good point about the ve table i never really thought of that, i guess it will almost be a trial and error thing and this may even put us right back to where we started at in the first place...
ok you make a good point about the ve table i never really thought of that, i guess it will almost be a trial and error thing and this may even put us right back to where we started at in the first place...
03-21-2005, 12:05 AM
#14
so when you tried to tune it in the VE what exactly happened? maybe that pressure change is too much for the ve to accuratley fix? im gonna give this a shot tomorrow and log and everything and ill let you guys know the results. just let me knw what happened when you tried to fix it in the ve table
so there would have to be some kind of relation of this all to load then,maybe
so there would have to be some kind of relation of this all to load then,maybe
03-21-2005, 12:10 AM
#15
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Originally Posted by WS6FirebirdTA00
so when you tried to tune it in the VE what exactly happened? maybe that pressure change is too much for the ve to accuratley fix? im gonna give this a shot tomorrow and log and everything and ill let you guys know the results. just let me knw what happened when you tried to fix it in the ve table
Where you see my negative trimming, I could lower the VE to hell if i needed to and if barely fixed my trimming problems. As a matter of fact, my driveability began to vastly deteriorate as well since currently my VE table is smooth as a baby's ***. The attempt to get those trims back inline wasn't effective enough to justify the loss of driveability.
Also, what happens when vaccuum pressure hits 85?
Last edited by txhorns281; 03-21-2005 at 12:26 AM.
03-21-2005, 07:33 PM
#17
well i went out tonight to log and everything and wow, all i can say is before it was all out of wach and the VE table looks a lot better now. if you guys wanna see it i can try and get a screen shot and show the difference, this fixed my unexplained ripples i had. now i still have to go back out and tune some more
quick question though, do i want to average the short term and long term fuel trims?? cause i had some that were -10 lt and -6 st i dont know if that should be -8 or -16. txhorns let me know about this. i would imagine its best to just use long term trims if the short temrs all went to 0.
quick question though, do i want to average the short term and long term fuel trims?? cause i had some that were -10 lt and -6 st i dont know if that should be -8 or -16. txhorns let me know about this. i would imagine its best to just use long term trims if the short temrs all went to 0.
03-21-2005, 07:58 PM
#18
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Originally Posted by WS6FirebirdTA00
well i went out tonight to log and everything and wow, all i can say is before it was all out of wach and the VE table looks a lot better now. if you guys wanna see it i can try and get a screen shot and show the difference, this fixed my unexplained ripples i had. now i still have to go back out and tune some more
quick question though, do i want to average the short term and long term fuel trims?? cause i had some that were -10 lt and -6 st i dont know if that should be -8 or -16. txhorns let me know about this. i would imagine its best to just use long term trims if the short temrs all went to 0.
quick question though, do i want to average the short term and long term fuel trims?? cause i had some that were -10 lt and -6 st i dont know if that should be -8 or -16. txhorns let me know about this. i would imagine its best to just use long term trims if the short temrs all went to 0.
And I'm going to not pursue your injector theory.
03-21-2005, 08:14 PM
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Originally Posted by WS6FirebirdTA00
why dont you wanna do it? any particular reason?