Are there any forseeable problems with turning closed loop OFF and using my catalytic converter? Emissions aren't of concern to me, but I still need to keep the cat so I can get the car inspected (I think I'll just use a stock chip when I go for my emissions test).

In addition, I have read of several advantages to leaving the car in open loop, but I don't see why it's better than just adjusting the stoich. AFR constant and enabling closed loop. What's the justification?

 

I know this isn't apparent as much with an IAT sensor, but I notice when it's colder outside ~50°F my BLM's are 135. When it gets hot (~80°F) the BLM's are around 122.

Which means the ECM is adjusting because of differences in weather conditions. Again, not so bad with an IAT, but some info to think aboot

 

So, you're saying that it'll compensate in closed loop? Are those readings after the car warmed up or while it's cold?

 

yeah...that's the idea. The ECM compensates while in closed loop.

Closed loop is "on" when the engine is fully warmed up because the O2 sensor will only work when it's hot (~600°F, correct me if I'm wrong).

Please tell me what the advantages are of leaving an engine is open loop. I wouldn't for a street driven car unless I had a WB O2. Maybe a track only beast running leaded gas.

 

I remember hearing Grumpy tell people to get a WB and set the car so it always stays in open loop. From my understanding, I think open loop runs completely from lookup tables rather than variable sensor data (i.e. O2). Theoretically, if the car is tuned perfectly, it should work better in open loop versus closed loop (?). Unless he just meant to TUNE in open loop. What do you think?

 

More to it then just that.

For off road use in none cat equipped cars, AFRs other then Stoich maybe more optimal for a given engine.

Yes, open loop is just that, ie no corrections based on feedback from the O2.

SOME cars will run noticeably better in open loop, then closed. Big cammed engines tend to oscilate at idle, some chips in stock form even have Open Loop Idle settings.

When your trying to tune in closed loop all you can tune for is Stoich (well basically). So you can wind up chasing your tail.

Some calibrations, apply the leaned BL to WOT if the correction is rich. So your WOT might vary some do to the BL and that can make tuning tougher.

There are several realms to tuning. On Road, Off Road, With Cat, Without Cat, all the replies in a formum like this must be kept seperate, taking a rely from one realm to another may or may NOT work.

And if your going to tune for Open Loop a WB makes the job a million times easier.

 

I appreciate the reply, Grumpy. I plan on building a WB to help with this. In my application (on- OR off-road, with cat), what would you recommend I do? I need to pass an emissions test, but that can be remedied by using a stock chip when I go in for inspection. What are the repercussions of running a non-stoichimetric AFR with a cat? And, you're saying that if I want to run an AFR other than stoich, I'd have to run in open loop (or have a tough time tuning)?