afr swinging

[smartin436]

Hi all, I recently got my Lotus 7 replica running on ms2 v3, with an lc2 wb. The engine is a 4.6 dohc ford. I bought the registered version of tuner studio and have been very impressed with the ve Ana. Live feature. I do have one issue that has me puzzled. At idle I get a steady afr, but at any throttle position above idle my afr swings from about 12 to 20. It seems to occilate at a steady pace. I can see the pw swinging as well.
Anyone have any ideas what would cause this? My o2 sensor is about 4 inches behind the collector, is this too close?

[kjones6039]

Hmmmmmm...... An msq and log seem to be in order here!

Ken

[smartin436]

May be a couple days.........but I'll get one posted

[smartin436]

Current msq. I am also having some popping and backfire when changing gears under hard acceleration. Any help would be greatly appreciated.

[kjones6039]

A couple of things jump out at me from your msq. Unfortunately they probably don't have anything to do with your AFR swings. So, a data log is still in order, when you get a chance to post one.

Now, your msq..........

Under Ignition Settings, IIRC, Dwell Type should be set to Fixed Duty since you are using EDIS.

We can take a look at your AFR issue when you can post a log.

Ken

[smartin436]

Here is a short log file, it did the swing thing around record number1800ish. It was drizzling rain outside and this car is an open roadster.
I'll try to get a better one tommorow if the weather breaks

[PSIG]

I didn't look through your whole msq, but it's simply not tuned yet, and it's trying too hard to help you. Your ignition table is completely un-tuned, your VE table is only a partial, and based on odd AFR targets. You can have MLV help you tune the fuel, but two things should happen first.

1.) Setting the the ignition table into the ball park is first. Do some reading in the manual for tips on creating a better ignition curve, or get some assistance. Same for AFR table numbers. It's all based on tuning theory. You have to know what you are trying to achieve if you are going to tell the ECM what to do about it. What your fuel does is based on your ignition, and also the AFR targets when in closed-loop or auto-tuning.

2.) Your EGO correction settings are giving it too much authority, and with an ugly table it's over-reacting. Notice in your log how the ego corrections swing full scale as it tries to control but goes too far each way. I would suggest increasing EGO ignition step size to 30 or so, controller step size to perhaps 1%, and the controller authority to 5% max, for now. The reason your idle is stable is that the self-correction is set to only be active above 1000 rpm and 35 kPa, which is above your idle range. That part is good, and idle fuel should be adjusted manually to obtain the lowest MAP (greatest vacuum) at your best warm idle rpm, the AFR checked at that point, and that best AFR entered into the idle area on your AFR table. Only then should you let it try to control your idle fueling.

When you go for tuning drives, at first go easy, so it has time to see what's happening and make multiple corrections on the same VE bins. After driving around the same way for a while, you can manually smooth the table into areas you have not driven yet, based on the results of nearby areas you have been. Do some smooth but more aggressive driving to let it tweak those areas, and so on.

BTW, do a search for posts about tuning methods and how to determine best total timing, cruise timing, power and cruise AFRs and such. It's fine to use the auto-tuning features of the software, but it's only as effective as the numbers you enter and the goals you set for it. You are still the tuner, and it will try to do whatever you tell it to. It's just saving you some time getting to those goals - right or wrong. Good luck, and post results as you go.

David

[smartin436]

Thanks David, makes sense.......will do