close/open loop issue

[thecrash91]

Hey all!
Lately my car has been having trouble making the switch between open and closed loop. I always forget which one is which, because whenever I read the difference my head explodes for some reason.

So when I try and boost below 4k rpm my AFRs stay stoich (~14.7) until I hit 4krpm, then it goes down to 10 as it should with bad stock tune. I have no EMS, but the car doesnt hit boost cut till 5.5krpm, so I do have some usable range and I know that its nothing to do with not having EMS, because it has worked properly in the past. by properly I mean the second I hit .5psi at 2.5k rpm my AFRs went to 10.

I just changed my plugs (did notice a little more pep out of boost, but thats cuz they were in real bad condition) , i cleaned MAF (also unplugged while idling and the car idled like s***, so i know its not maf) also cleaned my front o2 with the MAF cleaner, and it got a lot of carbon off but nothing changed. I did have a code for running lean, i believe P0171 system too lean, which makes sense cuz its lean in boost.

Can anyone help me out or point me in some sort of direction? cuz im lost

 

[bryanoverlin]

What did you gap your spark plugs at?

 

[CHIQLES]

I by chance was recording my 02 this morning you can see the scatter chart only went to around 4000 its probable that the times before where your afr jumped high. to10 was due to rpm and engine load..

 

[thecrash91]

What did you gap your spark plugs at?

.3

and CHIQLES, it happens all the time no matter how much load

 

[thecrash91]

I say load doesnt matter because ive experienced it going uphill, downhill, level ground, full throttle and partial throttle. always get 14-16 afr from 2k-4krpm and once i hit 4k its like a new beast is unleashed and it jumps to 10AFR and I get a HUGE boost in speed.
If i floor it at low RPM and just let it climb from ~3k it feels sluggish until the AFRs go right at 4k, which doesnt make sense because usually the leaner you are the more power you have.

Its almost as if the car doesnt know what to do with the boost until higher RPM

 

[thecrash91]

anyone?

 

[f1yen]

I have had some similar experiences, the transition to open loop (not controlled by oxygen sensor) when getting into boost, regardless of rpm, I have much experience with.
I am currently trying to program a microcontroller to make sure the car behaves like this. I will have to report back when it is up and running....

I can force my car to go into open loop when just passing 0psi... or I can let it sit in closed loop untill 4k

The problem I have seen, IIRC is that the stock ECU pulls a lot of timing at 100% load. so even if it is bouncing around 14.7afr, It will have a bunch of timing pulled.

 

[thecrash91]

I have had some similar experiences, the transition to open loop (not controlled by oxygen sensor) when getting into boost, regardless of rpm, I have much experience with.
I am currently trying to program a microcontroller to make sure the car behaves like this. I will have to report back when it is up and running....

I can force my car to go into open loop when just passing 0psi... or I can let it sit in closed loop untill 4k

The problem I have seen, IIRC is that the stock ECU pulls a lot of timing at 100% load. so even if it is bouncing around 14.7afr, It will have a bunch of timing pulled.

could it just be a result of not having an engine management? because if i remember correctly the split second units (which i have used previously) send a signal to force the car to switch over?

 

[f1yen]

I have an SSFTC, but I refuse to use the overboost setting, it sends a 50% Duty cycle signal switching between .2 and .8 volts. My trims were still being increased when the overboost setting was tripped, So that is why I am looking for (or making) a better long term solution to forcing open loop.

 

[thecrash91]

so this is a common thing? theres no fix? there was one day where it was working perfectly, where the second i went into boost my AFRs went straight to 10 and the car felt amazing. thats why i say it almost feels like it doesnt know what to do with the boost till 4k. i feel like timing is being retarded so much until 4k. most times it feels like im not in boost till 4k no matter what psi. also psi is slow to build till then too but i figured it was cuz of the bigger turbo.

 

[thecrash91]

anyone..? i refuse to believe that this is normal for this car, as ive never had this issue with the smaller turbo. UPDATE: i reset my ecu about a week ago and since then ive driven over 250 miles and no CEL. so just the bad AFRs until 4k RPM. could it be caused by pending codes? maybe the car is in some sort of limp mode? possible?

 

[f1yen]

Its always been like that for me, I only had the gt28 when I bought it, no experience with the 25.... I feel like if I boost too low in an rpm say before 3k, ittle pull a bunch of timing, and wont give it back untill I change gears, or sometime I'll get on it at like 3200 rpm and ittle pick up nice and transition nice into open loop...

 

[Dr0]

sounds like the good ol stock tune to me... just lean out your fuel map little by little until you step into the 11-12 range on afrs in boost. all i did to mine was lean out the map just before boost and a little in boost. my car has been driving like a boss for about 5 months now, ive had a couple 10 afr in boost hiccups (hitting wall feeling) but it typically clears up after i shut it off and restart it.

the car pulling timing in boost pre open loop sounds plenty normal to me... either get a ems or deal with the stock tune and keep out of boost until about 3-4k and youll be a happy msp owner...

you can mod all you want to try and make this issue less prevelent but it will always be there to bug the s*** outa you lol

 

[CHIQLES]

+1

 

[thecrash91]

sounds like the good ol stock tune to me... just lean out your fuel map little by little until you step into the 11-12 range on afrs in boost. all i did to mine was lean out the map just before boost and a little in boost. my car has been driving like a boss for about 5 months now, ive had a couple 10 afr in boost hiccups (hitting wall feeling) but it typically clears up after i shut it off and restart it.

the car pulling timing in boost pre open loop sounds plenty normal to me... either get a ems or deal with the stock tune and keep out of boost until about 3-4k and youll be a happy msp owner...

you can mod all you want to try and make this issue less prevelent but it will always be there to bug the s*** outa you lol

its not the rich tune thats bothering me.. its the fact that my AFRs are lean as **** until 4k rpm, which causes timing retardation. i dont see how getting an EMS will help, as this has to do with open and closed loop, and has nothing to do with the tune itself. hell the bad rich tune runs better then when its stoich in boost. again, this all stopped for one day, and the car acted amazing, and the second i hit boost my afrs would go rich as hell, and i want the car to act like that again.. i have owned this car for 4 years and i can tell you that this isnt normal... until recently it always went rich the second i touched boost...

"you can mod all you want to try and make this issue less prevelent but it will always be there to bug the s*** outa you lol"
i dont really know why youre saying this, as i havent changed anything on my car in close to a year...

 

[thecrash91]

is there some sort of limp mode for our car that may be causing this?

 

[2088 MSP]

is there some sort of limp mode for our car that may be causing this?

no limp mode at all.

but anyway
i'm basing this on the mods u have in your signature: you're running way more boost, and way more flow(because of the bigger turbo) and you have bigger injectors. of course the stock tune is gonna be freaking out as soon as you touch boost. it says you have a ftc, are you using it?

Here is my understanding:
1. stock vehicle, stock conditions. ecu stays in closed loop (hovering around stoich) while out of boost --> then switches to open loop (goes insanely rich, according to the stock tune) as you transition into boost.

2. Now in your case: ecu stays in closed loop as before while out of boost (again hovering around stoich), --> then as soon as you try to punch it, maf sees way too much air flow (even though u might not be at 14 psi or whatever right away, because of the bigger turbo, the volumetric flow of air is still higher) and cuts fuel. (and i cant even imagine what kind of havoc the bigger injectors are causing on your short and long term fuel trims)

Here is what the solution should be in my opinion. (this is based on the fact that mine was doing the same thing, when i was mostly stock, just running way more boost and without any ems)

First just to double check what kind of bucking/jerking/stuttering are you experiencing? is it literally just like a light stutter? here is what mine was doing (old video, and its hard to see, but u can hear it was stuttering when trying to get in boost) : http://www.youtube.com/watch?v=S_LWLI1v5ys

The solution turned out to be (like someone mentioned before) properly gapped plugs(i'm actually running even smaller than stock gap now, just on the safe side), new coils and wires.

Or is the car bucking/jerking? (i think you mentioned, like hitting a wall) Then yes you do need an ems to intercept the maf signal and LIE to the ecu so it doesnt cut fuel.

 

[thecrash91]

no limp mode at all.

but anyway
i'm basing this on the mods u have in your signature: you're running way more boost, and way more flow(because of the bigger turbo) and you have bigger injectors. of course the stock tune is gonna be freaking out as soon as you touch boost. it says you have a ftc, are you using it?

Here is my understanding:
1. stock vehicle, stock conditions. ecu stays in closed loop (hovering around stoich) while out of boost --> then switches to open loop (goes insanely rich, according to the stock tune) as you transition into boost.

2. Now in your case: ecu stays in closed loop as before while out of boost (again hovering around stoich), --> then as soon as you try to punch it, maf sees way too much air flow (even though u might not be at 14 psi or whatever right away, because of the bigger turbo, the volumetric flow of air is still higher) and cuts fuel. (and i cant even imagine what kind of havoc the bigger injectors are causing on your short and long term fuel trims)

Here is what the solution should be in my opinion. (this is based on the fact that mine was doing the same thing, when i was mostly stock, just running way more boost and without any ems)

First just to double check what kind of bucking/jerking/stuttering are you experiencing? is it literally just like a light stutter? here is what mine was doing (old video, and its hard to see, but u can hear it was stuttering when trying to get in boost) : http://www.youtube.com/watch?v=S_LWLI1v5ys

The solution turned out to be (like someone mentioned before) properly gapped plugs(i'm actually running even smaller than stock gap now, just on the safe side), new coils and wires.

Or is the car bucking/jerking? (i think you mentioned, like hitting a wall) Then yes you do need an ems to intercept the maf signal and LIE to the ecu so it doesnt cut fuel.

you did NOT take the time to read what i wrote... the problem IS NOT BUCKING OR HESITATION OR ANYTHING LIKE THAT... the problem is that my AFRs stay stoich until 4k RPM, hence why the thread is called open/closed loop issue... becuase im having an issue switching between the two, nowhere did i ever say anything about hesitation.

my plugs are gapped at .3, as i stated earlier.. please read before you jump to conclusions and post such a long response that has nothing to do with my problem. i feel bad you just wasted your time.

and like I also previously said, there was one day where the car worked flawlessly. the second Id go into boost my AFRs would go to 10, and it was actually responding well to low RPM boost, and not pulling timing like a mofo. now it doesnt go rich until 4k rpm and anything under 4k rpm the timing is pulled like a mofo, no hesitation though... no CEL either... vacuum is always -22, plugs are brand spankin new. old ones were pretty bad though.

also want to make this clear, tuning is NOT my priority right now, so you guys may think its bad to be in 10 afr, but right now thats what i want, THEN i will start to tune once my car is acting normal again.

 

[2088 MSP]

... the problem is that my AFRs stay stoich until 4k RPM,

they're supposed to stay stoich, that why its called closed ******* loop!

and btw, i attempted to help an issue you weren't having (my mistake) and wrote such a long response is precisely because i read the whole thread, so if you cant accept somebodys' help, you need to chill the **** out.

 

[thecrash91]

they're supposed to stay stoich, that why its called closed ******* loop!

and btw, i attempted to help an issue you weren't having (my mistake) and wrote such a long response is precisely because i read the whole thread, so if you cant accept somebodys' help, you need to chill the **** out.

i was using caps to add emphasis not anger, sorry for confusion. thanks for the contribution though, i do appreciate it.