Wavering AFRs with VF37 install

[thejean]

Hey everybody. I put a twin scroll setup on my car and before the turbo swap I had the TD04 on the car with the O2 in the header. When I put the TS setup on, I moved the O2 to the DP, right after the turbo. Since the turbo swap, I have noticed that if I'm at less than 10% TPS and decelerating or cruising and around 2000-2500 rpms, my AFRs start to osscilate wildly until I either get on the gas a bit more or off it completely. Has anyone else ever experienced this? Is there a time delay that the ecu is expecting between the O2 feedback and the adjustment? Perhaps moving the O2 to the DP has screwed this up? Any help would be appreciated. Cheers, JC

[Mr Grey]

Do you have any logs of this and is this a wideband we're talking about.

[thejean]

Yeah, it's a LM-1 wideband and I have tried 2 different front O2 sensors and it still does the same thing. It never did this until I installed the twin scroll setup with the front O2 after the turbo. I may just try relocating the O2 but I hate the thought of not capturing all 4 cylinders with the AFR reading.

I am going to look into scaling the heater range on the O2 sensor and see if that can do something beneficial.

[thejean]

Here is a log:

[jaxscuby]

it seems that the location of the o2 sensor
is giving you some trouble. see if you can relocate to
the turbo end of the up-pipe. but about 4 inches below
flange.

[west_minist]

Can you perform a third gear log?

[thejean]

Can you perform a third gear log?

I can but it doesn't do it under load. Under load everything is fine. It only does this when I decelerate under medium throttle to light throttle. If I completely lift off the gas, the injectors shut off and the AFR goes to 20.9% O2. It's a very odd thing. If it ends up bugging me too much, I'll just relocate the O2 sensor. Weird thing is, nobody else seems to have had this issue with a VF37 install. I thought maybe it might have also had something to do with being catless (not enough back pressure under light throttle). Who knows. I know I'm stumped, that's for sure.

[west_minist]

When you lift, it is normal to see that.

What you may have to do is to add a little more throttle enrichment for that range.

let me take another look at the logs.

[west_minist]

Can you post the rom you are using?

I just did a replay and saw what you are talking about at very low throttle.

I think the problem is that the v37 is pushing a little more air than your stock turbo, causing the setup to be a little more leaner at that particular throttle % for your rom.

[thejean]

Can you post the rom you are using?

I just did a replay and saw what you are talking about at very low throttle.

I think the problem is that the v37 is pushing a little more air that your stock turbo, causing the setup to be a little more leaner at that particular throttle % for your rom.

That would make a ton of sense. I use the A4SGD10C rom (I think that's the right numbers/letters). What map/table would I have to change to richen it up a little?

[west_minist]

What you can try doing is to add a little more throttle enrichment around the 4 mark.

I am curious to why the your air fuel correction did not balance the AFR as it should. I wonder if your O2 sensor has little more heat damage.

Can you perform a log for over 20secs, with just throttle around 1-10%?

Concentrate on the 4% throttle.

Please log all air/fuel parameters.

Do you have an LC1?

Get one and hook it up and log it as an external sensor.

[thejean]

I have an LM-1 so I can log AFR for sure.

What I might do is see if someone can swap sensors with me for a week and see if damage to the sensor heater is the problem.

[west_minist]

Sometimes when the guys remove it, some apply too much heat, that can damage it.

[thejean]

Well, my front O2 started throwing codes (P1131) so I'd say it was either shot all along or on it's way out. I'll replace it and see whether I still get this AFR wavering. JC

[west_minist]

Fantastic.