Having TWO strange AFR problems. Random Lean while cruising, and 10.0 at WOT

[brandnew161]

Hows it going guys. Alright I'm having some strange problems relating to some AFR readings i'm getting. I waited to post until I did a Boost Leak Test, but no avail. So heres whats going on.

1st Problem) I will be cruising at city speeds, 30-45 mph, and all of a sudden I will feel a small jolt. So I glance at my AEM UEGO and notice that my AFR has spiked(leaned out). Now this happens quite often and only lasts a split second. The AFR usually spikes anywhere from 15-17 (ouch!). I noticed that this never happens at highway speeds 65mph+. Maybe egr related? I'm not sure


2nd Problem) I am using a MAFT and SAFCII to piggyback. I am boosting @15psi. No matter how I configure the settings on my SAFCII, my AFR at WOT is 10.0. At about 4400 RPM the AFR is ~12.5 and 5200RPM and up its 10.0. On the Hi setting on the SAFC it is currently set at -24%. I lowered the reading to -35% but it made no difference. I did this for the 4400, 4800, and 5200 RPM points. If I tweak the MAFT settings for "WOT" it just simply throws my tune out of wack and leans it all out. Do I play with the rough WOT settings on the MAFT and fine-tune with the SAFCII to find a safe median between the two devices?

I dont believe the two problems are related at all. I just wanted to post them together since they both relate to AFR issues. I did do a boost leak test. Had two leaks. One at the MBC (just ordered a replacement) and at the adjustment screw on my Aeromotive AFPR (fixed with teflon tape).

Thanks in advance

 

[joe sobo]

i am not sure of the exact components you are using right now, but if you run lean while you are not in boost, and are running rich under boost, then that is the way it is supposed to be. but you have to lean it out at wot, and you would be set.i have no clue how to tune

 

[brandnew161]

well i got the second problem fixed today after doing some massive tuning changed. Its all good now though, of course it'll have to be fine tuned over the next few days. Still not sure on the first prob tho..

 

[the_mork]

Try to get a log of your lean spike if you could. I think IPW, airflow, rpm, load, timing and AFR would be sufficient.

As for the problem you fixed, keep in mind that AFAIK the UEGO only displays as rich as 10:1 so you were probably quite a bit richer than that even.

 

[brandnew161]

Try to get a log of your lean spike if you could. I think IPW, airflow, rpm, load, timing and AFR would be sufficient.

As for the problem you fixed, keep in mind that AFAIK the UEGO only displays as rich as 10:1 so you were probably quite a bit richer than that even.

I'm shopping for a logger now. Been looking for a good one for quite some time but havent settled on one yet. I really do need one, itd be nice to really see whats going on

I did not know about the UEGO's reading. I remeber hearing something like that but i had completely forgot. Idk if you have used a maf/maft or have one now but get this. I have the maft dialed in for the correct cc injectors (680cc) and the wot, mid, and all that good stuff. Then since i "retuned" to "fix" the problem i was having i changed the high settings on the APEXi again and had to set them to -45% from 4000RPM to 52000RPM to get the UEGO to read roughly 13.2 AFR. Idk maybe i was sold 750cc injectors or something by accident 0 But something seems screwy. I really need a logger

 

[mike96]

at least your lean condition is a quick and self fixing one. i had a similar issue a while back, my car went lean and once it did it usually staid that way until i fixed something. a couple of times i thought it was parts gone bed so i would replace things (coils, wires, fuel injectors) and the problem would go away for a bit but the last two times it did that i turned out that i was having wiring issues. i had done a partial tuck on my wire harness and several solder joints didn't hold up the way i wanted them to. one was a fuel injector and the other was the coolant temp sending unit. i ended up pulling the wire harness and re-doing all the solder joints and putting it back in the car, worked really good for about 6 months until the car got totaled. might want to go over your wiring and check for any bad wires, doesn't hurt to look everything over and it doesn't cost you anything after all.

 

[brandnew161]

good call i'll check it, might as well. thats sucks that happened with your car. Its always the easy stuff in disguise yahno.

 

[the_mork]

At 4000+ rpm 13.2 is dangerously lean under load. Shoot for 11.2. 680s are really pushing the limits of piggyback systems so you might consider going to a flashable ecu or putting that eprom ecu to good use.

As far as not having a logger why are you even driving your car without one? Pick one up ASAP. If you were 97+ I would hands down recommend evoscan but I'm not sure of the status of compatibility of evoscan with 95 ecus. You might want to research that. Even with slow sampling evoscan would be the way to go if it will connect.

 

[brandnew161]

yea i was looking at evoscan i a believe i do need a newer model ecu. But if a get a ecu compatible for evoscan i'm SOL down the road if i want dsm link. i really dont want a pocket logger, i want something i can use with my laptop.

i'll try and richen it up to 11.2 thanks

 

[the_mork]

My basic suggestion on your AFR curve is to try and have it at 14.7:1 at cruise, closed loop will take car of this for you, then drop to 12.5:1 as soon as you hit the throttle up until about 5psi at which point you drop quickly to the low 11s. That may be hard to achieve with piggybacks but just don't go leaner than that.

Also IMO you should sell the MAFT and SAFC for enough to pay for a flashable ecu or a good chunk of dsmlink.

 

[Pirrofab]

Your not alone when it comes to the first issue of randomly going lean while driving around town. My car seems to do it best around 45-55mph and in 5th gear light throttle. It will just randomly lurch forward while driving and lean out and stay lean unless i blip the throttle a few times or downshift to 4th and ride it for a few seconds then go back to 5th.

I think that with the safc it may be affecting how the ecu determines egr operation by using diffeent fuel and timing tables giving the lean condition.

I haven't figured it out yet on my car as all I have to do is floor it for a second or downshift. It just gets annoying when you have a girl in the car and she starts asking what the hell did you do that for.

 

[brandnew161]

Your not alone when it comes to the first issue of randomly going lean while driving around town. My car seems to do it best around 45-55mph and in 5th gear light throttle. It will just randomly lurch forward while driving and lean out and stay lean unless i blip the throttle a few times or downshift to 4th and ride it for a few seconds then go back to 5th.

I think that with the safc it may be affecting how the ecu determines egr operation by using diffeent fuel and timing tables giving the lean condition.

I haven't figured it out yet on my car as all I have to do is floor it for a second or downshift. It just gets annoying when you have a girl in the car and she starts asking what the hell did you do that for.

hahaha wow true story i hear ya. I'm planning on removing my egr over the winter so if that fixes it i'll let you know

I bought the maft/maf/safcII all very cheap thats why i'm using it. I didnt have and arm and a leg to chop off for dsm link but this winter since i wont be driving the car i'll see about parting them out. I would like to get dsmlink no doubt about it.