B15 Sentra Forum banner

21 - 35 of 35 Posts

·
Casual Lurker
Joined
·
2,135 Posts
tbuh said:
Would someone give me a clear answer as to whether or not we should have lo-throttle settings set on our S-AFC's?
When talking about stock injectors


ZERO... there should be no correction factor what so ever you will end up in a losing battle with the ECU
 

·
Casual Lurker
Joined
·
2,135 Posts
AntonToo said:
How do you explain Specs running so rich stock?

those are open loop maps ... your LO setting whould be set to basicly run with your closed loop .. and hi to open loop .. stock the closed loop is a dance between MAF and the O2 being courted by your fuel trims ..
 

·
Casual Lurker
Joined
·
2,135 Posts
gurov said:
i don't have any corrections in the low map or below 3000 rpm right now.
the ecu does a good job at correcting for injector sizes, most of the time i'm running with -25% longterm fuel trim as reported by obd2
but you are also running lower Fuel pressure from what i remember in our previous conversation ..

You can run large injectors but only with in the scope of what the LT ft can handle +/- 30 ... plus you LTFT I believe affect your OPEN loop maps so pusle width woudl be adjusted and pulse width would not equal fuel flow from the larger injector to the smaller but you would have the AFC to take care of that at open loop .. ..


regradless .. you can do it .. there is just a limit to it ..
 

·
King of OT
Joined
·
5,210 Posts
When you're in closed loop your car is using both the MAF and o2 sensor to figure out how much fuel to use, and it's kept pretty close to optimum A/F. When in open loop you're only reading off of the MAF and to keep it safe, the car runs rich. According to Mike, the qg ran rich too in open loop.
 

·
Casual Lurker
Joined
·
2,135 Posts
pugnex said:
When you're in closed loop your car is using both the MAF and o2 sensor to figure out how much fuel to use, and it's kept pretty close to optimum A/F. When in open loop you're only reading off of the MAF and to keep it safe, the car runs rich. According to Mike, the qg ran rich too in open loop.

pretty much every car runs rich in open loop .. ;)
 

·
King of OT
Joined
·
5,210 Posts
JohnO said:
pretty much every car runs rich in open loop .. ;)
Well people kept saying that the qg ran lean all the time. I was just pointing out that Mike, after installing his wideband, found this to be untrue.
 

·
Casual Lurker
Joined
·
2,135 Posts
pugnex said:
Well people kept saying that the qg ran lean all the time. I was just pointing out that Mike, after installing his wideband, found this to be untrue.
hmm . i didn't know that was the common concencus of the QG ... either way i can pretty much say confidently that there is really no production car that runs lean on purpose at open loop ..

Now cars with wideband can run closer to stoich but they dont really ever run open loop ..
 

·
King of OT
Joined
·
5,210 Posts
Now...why is there even open loop? Wouldn't it make sense for the car to run stoich. at all times??? Why stop reading from the O2 sensor?
 

·
NOS Program 2.0
Joined
·
968 Posts
Discussion Starter #30
pugnex said:
Now...why is there even open loop? Wouldn't it make sense for the car to run stoich. at all times??? Why stop reading from the O2 sensor?
lambda - o2 reading only indicates rich or lean. for proper power output and safety 13.1 (or so) afr must be maintained.
 

·
NOS Program 2.0
Joined
·
968 Posts
Discussion Starter #31
JohnO said:
but you are also running lower Fuel pressure from what i remember in our previous conversation ..

You can run large injectors but only with in the scope of what the LT ft can handle +/- 30 ... plus you LTFT I believe affect your OPEN loop maps so pusle width woudl be adjusted and pulse width would not equal fuel flow from the larger injector to the smaller but you would have the AFC to take care of that at open loop .. ..


regradless .. you can do it .. there is just a limit to it ..
hmm, where is that +/- 30 coming from ?
it sure as hell feels like LTFT affects openloop maps, cause i'm running 13.2 with like -8 adjustment on the safc up from 3000 rpm.
 

·
Casual Lurker
Joined
·
2,135 Posts
gurov said:
hmm, where is that +/- 30 coming from ?
it sure as hell feels like LTFT affects openloop maps, cause i'm running 13.2 with like -8 adjustment on the safc up from 3000 rpm.

ECU limit ..the FT is there for condition driving and any system problems not for actually running larger injectors...

basicly at that point the ECU says enough and just runs open loop and throws a cel .. every car has limit set from the the manufactuere .. subbies are 25%+/- ... Regardless this info has been posted on here as the Spec's limit on FT I think Mike Kojima posted that .. i also think that Travis got the same info from Clark .. and i know that is what Sahra told me when i was making plans to boost because i asked tht specificly to see how much room i had to play with ....

also as far as LTFT affecting open loop .. im pretty sure it does but people have debated with me otherwise here so i won't call it a fact but my personal opinion until i can do some heavy testing or someone else can ..

now from what your are stating is seems to back our assumption on that with your injectors but still ;)
 

·
Registered
Joined
·
2,871 Posts
pugnex said:
Now...why is there even open loop? Wouldn't it make sense for the car to run stoich. at all times??? Why stop reading from the O2 sensor?
because
1) factory o2 sensors are not sensitive enough..they can't read accurately at certain regions of AF ratios
There are wideband o2 sensors that can do what you want..but they don't last as long as factory units.

Also you don't want to run at stoich all the time because the engine would overheat. The cooling system on cars is not adequate enough so use put in some extra fuel to cool down the system
 

·
Registered
Joined
·
1,424 Posts
Man this turned out to be a sweet thread. I learned a lot, and everytime I read read it I pick up on something else. STICKY?
 

·
NOS Program 2.0
Joined
·
968 Posts
Discussion Starter #35
JohnO said:
ECU limit ..the FT is there for condition driving and any system problems not for actually running larger injectors...

basicly at that point the ECU says enough and just runs open loop and throws a cel .. every car has limit set from the the manufactuere .. subbies are 25%+/- ... Regardless this info has been posted on here as the Spec's limit on FT I think Mike Kojima posted that .. i also think that Travis got the same info from Clark .. and i know that is what Sahra told me when i was making plans to boost because i asked tht specificly to see how much room i had to play with ....

also as far as LTFT affecting open loop .. im pretty sure it does but people have debated with me otherwise here so i won't call it a fact but my personal opinion until i can do some heavy testing or someone else can ..

now from what your are stating is seems to back our assumption on that with your injectors but still ;)

he said/she said, ugh. could you please find the thread/article with that +/- 30 number, i'm rather interested in how far i could push the stock ecu (for kicks mostly).
 
21 - 35 of 35 Posts
Top