2zz roadster still running 10.8 afr

[Tedtiler]

Hi guys. Have a 2zz conversion track car running cone filter (correct 2zz maf pipe with vanes) and free flowing exhaust(no cat). It runs fine but silly rich. Driving easy afr readings are in the 12.5 range and at wot we are getting high tens. Killing the power. We've checked the wiring and changed all sensors,there are no exhaust leaks, no fault codes. It goes into lift ok and revs normally. Only strange thing is we wired the o2 sensor to the gearbox side precat side instead of the pulley side. However we are getting o2 readings from the ecu via the torque pro app.

Running super unleaded on a jap market celica ecu.

Any inspiration would be appreciated as I don't want to have to spend the kids Xmas money on a power fc to take control of what's happening.

Raymond , Belfast

[JoeCool]

Have you put a wideband on it/got it properly tested?

Mine has 2001 celica ECU and runs fine. I'm not sure I'd trust Torque on this, but I'll check my AFR tomorrow to double check. Just passed MOT today with utterly clean emissions.

You sure the MAF is wired correctly?

[ChrisGB]

Try a stock airbox? Cone filters could mess with the calibration, even with the vanes. I'd guess it'll be running open loop in lift, so O2 sensors probably not relevant.

[Tedtiler]

Yes it's got a tried and tested wideband on it. Checked with a different innovate LC-2 still high tens fuelling. We were considering air box , just seems odd slowing down the airflow to try and make it faster?!

[Tedtiler]

Thought maf wiring would throw a fault if wrong. Will double check it

[Alex Knight]

Where is your primary O2 sensor fitted? Manifold or collector?

Where are you taking the wideband reading from?

[Tedtiler]

O2 is just after the manifold/downpipe flange. Wideband readings well back in the exhaust . Its definitely rich, massive bangs on gearchanges and its bore washing (petrol in the oil) . Compression readings still excellent , haven't wrecked it but not good doing another track day like this

[Alex Knight]

For sure you need to check your primary O2 sensor wiring.

[Tedtiler]

Ok cheers, will do. Maybe wire it to the pulley side precat wiring and see if it helps.

I was under the impression that fuelling under wot is only controlled by the maf but I stand to be corected  s:?: :?: s:?:

[shnazzle]

Ok cheers, will do. Maybe wire it to the pulley side precat wiring and see if it helps.

I was under the impression that fuelling under wot is only controlled by the maf but I stand to be corected  s:?: :?: s:?:

It is in part. MAF is one of the inputs to determine where on the open loop map it should look to fuel/time. It just doesn't take into consideration o2 sensors.
A number of factors determine whether it's in open or closed loop.

But if you're seeing 10.8 on WOT, high rpm, high load, engine warmed up, etc etc... Then the only other factor in finding the fueling is the air flow. So, points to MAF.
There has to be a reason why the ECU is adding more fuel.

My question is; when the car is in open loop and running on tables, it surely still reads the MAF to determine whether the fueling tables need to be augmented based on more/less air. But, how does it know how much to put in? It's not listening to o2 or wideband. So does it just have a built in calculation that says
- Table cell row 13, column 15 will put in X fuel, assuming MAF reading is Y
- reading will be augmented by percentage of MAF reading difference

You say you're running a Jap ECU. Did you use an appropriate system to check for codes? The MAF will throw codes if it's well out of whack. But if I recall correctly, if it doesn't work at all, it doesn't throw a code (someone else will need to confirm).

In short; I'm thinking it's your intake or MAF. Or combination

[Slice]

That was my understanding too, that the O2 sensing loop is more of a final trim to the values that are determined via MAF, temperature, throttle angle and rpm.

I had a similar issue years ago on an Audi, which traced to the coolant sensor. Annoyingly, Audi were running 2 of them, one to the dash, and one to the ECU. So the dash said warm, the ECU thought cold and overfuelled it to suit. New cats for that one... However, I assume Toyota aren't so weird and have just the one?

[shnazzle]

That was my understanding too, that the O2 sensing loop is more of a final trim to the values that are determined via MAF, temperature, throttle angle and rpm.

Not quite.
Closed loop uses a combination of long term, short term tables and o2 sensors readings. All to adjust the base map.
Short term fueling is adjusted by the o2 readings. If, over a longer period of time, the short term behaves the same, it is written to long term.

It reads the table based on the inputs from maf, temp, rpm, etc etc.

So basically it all runs parallel, constantly reading the o2 values to validate the data is has pulled from short/long term fuel trims. ...which are of course overlaid the base map on the ECU.

Open loop should just use the base map, because in those situations it can't rely on o2 readings. They're not quick enough. That's why ECU has specific tables for "tip in" etc to take into consideration how much extra/less it needs to inject when you all of a sudden ram the accelerator or let go of it.
No engine would last if it listened to o2 sensor readings and waited for the calculations constantly.


Hence my suspicion that it's not o2 at all, but something causing the ECU to go to the wrong part of the table and do the wrong calculations (not all of it is static tables).

I had a similar issue years ago on an Audi, which traced to the coolant sensor. Annoyingly, Audi were running 2 of them, one to the dash, and one to the ECU. So the dash said warm, the ECU thought cold and overfuelled it to suit. New cats for that one... However, I assume Toyota aren't so weird and have just the one?

I believe it does have one. But it can indeed be faulty and cause similar issues. Someone on here actually had this not massively long ago. Absolute nightmare replacing it

[frogger]

When you say "correct 2zz maf pipe with vanes" ... what actual pipe are you using?

I have encountered many pipes claiming to be for a specific engine, that turn out to be b.s. and just a little bit out, enough to screw fuelling.

... I now only trust OEM piping, and cut out the section of that to use from stock airboxes.  The only reliable way to get the right MAF housing first time, every time.

[shnazzle]

Rogue uses a MAF adapter from Eliseparts I think. That or the stock 2zz maf pipe cut up. I'm the same as you; the MAF is very sensitive and has been calibrated in factory for the specific setup. Messing with it by a millimeter could change readings. Stick with the best.

[Tedtiler]

When you say "correct 2zz maf pipe with vanes" ... what actual pipe are you using?

I have encountered many pipes claiming to be for a specific engine, that turn out to be b.s. and just a little bit out, enough to screw fuelling.

... I now only trust OEM piping, and cut out the section of that to use from stock airboxes.  The only reliable way to get the right MAF housing first time, every time.

It's the oe 2zz pipe cut from the celica air box and the vanes left on. Should really work I thought. Has for others

[Tedtiler]

Ok cheers, will do. Maybe wire it to the pulley side precat wiring and see if it helps.

I was under the impression that fuelling under wot is only controlled by the maf but I stand to be corected  s:?: :?: s:?:

It is in part. MAF is one of the inputs to determine where on the open loop map it should look to fuel/time. It just doesn't take into consideration o2 sensors.
A number of factors determine whether it's in open or closed loop.

But if you're seeing 10.8 on WOT, high rpm, high load, engine warmed up, etc etc... Then the only other factor in finding the fueling is the air flow. So, points to MAF.
There has to be a reason why the ECU is adding more fuel.

My question is; when the car is in open loop and running on tables, it surely still reads the MAF to determine whether the fueling tables need to be augmented based on more/less air. But, how does it know how much to put in? It's not listening to o2 or wideband. So does it just have a built in calculation that says
- Table cell row 13, column 15 will put in X fuel, assuming MAF reading is Y
- reading will be augmented by percentage of MAF reading difference

You say you're running a Jap ECU. Did you use an appropriate system to check for codes? The MAF will throw codes if it's well out of whack. But if I recall correctly, if it doesn't work at all, it doesn't throw a code (someone else will need to confirm).

In short; I'm thinking it's your intake or MAF. Or combination

Ive tried a number of different maf sensors, they all give fairly similar results, not bad afr at idle,and light load. Bit more or full throttle and up into lift getting mid 11 to high ten afr.  So the maf is reading up and down, just wildly out.

I have the jobd protocol for the jap ecu. It also works on my st246 caldina. No codes for maf or any fuelling sensor. Even tried coolant temp sensor. Had a big aluminium radiator in it that had it running too cool so changed that back but no change.

[Tedtiler]

Only other thing non standard is the missing evap system. Empty plug left just.

[shnazzle]

Vacuum leak somewhere? Check all the connections for intake, pcv, intake mani even

That's my last guess

[Tedtiler]

Thanks for your replies. Will report back.

[ChrisGB]

Vacuum leaks usually result in running lean as unmetered air gets into the system. MAF calibration is sensitive to the surrounding pipework. Do we know what the stock setup would usually run at full throttle? I seem to remember from a tuning session years ago that the 1zz was running something near to 11:1 as standard. There where gains by leaning it out, 12.5:1 being optimal.

[Tedtiler]

Just to report back I've managed to get this situation resolved I hope but it took a lot of digging on the Internet and trying different setups. Eventually settled on a pipe 1.5mm wider than the stock  2zz maf tube and a longer pipe too to smooth out airflow.

Can't believe how picky it is on maf settings. Seems a lot of newer cars including the gt86 need maf readings rescaled after adding an induction kit.

There just wasn't enough room to try the complete 2zz air box, it's enormous but I reckon would also have slowed airflow down a tad. I doubt these engines came out of the factory running 11.0 afr - think of the missing horsepower there.

It's now at about 12.7 and pulling a lot nicer, was surprised there was little or no info about on 2zz induction setups- must be a heck of a lot of people out there running about 30 hp down and don't know it.

Hope this helps someone
Raymond