EVO 1-3 Closed and open loop lambda issue.

[toyotec]

Hi everyone.
Recently an Evo 3 vehicle developed a problem where it would run at stoich during full load conditions up to and possibly greater than 4K ( I was not brave enough to load up the engine any faster!) A sudden tip in would result in a deviation of lambda to richer conditions momentarily but the lambda control would revert to 1. TPS was checked and find to be in good condition.
Using a definition supplied by Andy F for Evo3 Standard, and attempt was made to recalibrate the "closed loop TPS threshold" there is a curve with numbers starting with 76 and ending with 51. The X axis is blank. I am assuming this blank X axis should be rpm and the calibrated part should be throttle angle?However adjusting these numbers to their extremes i.e. setting to 51 or 112 makes no difference to setting closed loop control to open.
In the end I gave up. What do these numbers represent and had anyone used this table with success.

Kind thanks.

[GrayW]

If it was fuelling correctly and just suddenly changed to lambda 1 on WOT runs I would suspect fuel system issues, such as pump or FPR.

[toyotec]

If it was fuelling correctly and just suddenly changed to lambda 1 on WOT runs I would suspect fuel system issues, such as pump or FPR.

Fuel pressure is good and rises with boost.
I am sure this is a control issue rather than mechanical.

[GrayW]

So it just changed one day, or after you had done something to the car?

[toyotec]

So it just changed one day, or after you had done something to the car?

No it did not.
Months ago the vehicle was remapped to 423bhp@7400rpm and 350lbft@5500rpm (it does have supporting modifications). The calibration at the time of mapping seemed to be fine and full load conditions would result in the afr that was desired less than 12.5, in fact for component robustness it was run richer than LBT from 6500 rpm onwards. There was no audible knock heard with det cans after careful manipulation of the ignition tables.

Later on there was an issue with the engine which led to a rebuild. With the new engine back in vehicle, the calibration was checked on the dyno and it was discovered that on full load the from 2500 rpm onwards the engine was running at stoich. The boost was lowered to ~0.9 from 1.25bar ( profec B knobs turned all the way to the left) and the dyno was put into speed control, allowing, me to vary load. This is where I discovered there was a problem as in a the title.
I then experiemented with the curve for the closed loop threshold but did not detect any response.

So what does this threshold table do?

[AndyF]

Eddie,
There are a few bits wrong in some of the early xdf files.

If you right-click on the table name in tunerpro and then go to 'Edit item xdf info'

The address (hex) field should show as 0x7332. If it doesn't then change it so that it does.

You should then click on the columns tab and make sure that the 'number of columns' is set to 16. You can also manually add in the labels for every 500 rpm starting at 500 and finishing at 8000 whilst you're there if you want.

The table should run with 44% through from 500rpm to 3,500 then drop to 40% at 4000, 30% at 4,500 and 20% for the remainder through to 8000rpm.

You should then be able to modify that table to see the effect.

Hope that helps

Andy

[toyotec]

Eddie,
There are a few bits wrong in some of the early xdf files.

If you right-click on the table name in tunerpro and then go to 'Edit item xdf info'

The address (hex) field should show as 0x7332. If it doesn't then change it so that it does.

You should then click on the columns tab and make sure that the 'number of columns' is set to 16. You can also manually add in the labels for every 500 rpm starting at 500 and finishing at 8000 whilst you're there if you want.

The table should run with 44% through from 500rpm to 3,500 then drop to 40% at 4000, 30% at 4,500 and 20% for the remainder through to 8000rpm.

You should then be able to modify that table to see the effect.

Hope that helps

Andy

Andy to the rescue!
Thanks a lot for your explaination.
I will re-edit the definition and validate on the car later this week.

Regards.

[GrayW]

So after an engine rebuild you've gone from a 0.81 to 1 lambda without changes to the map?
Sounds more mechanical than mapping related, unless you've changed the spec/capacity of the engine by a drastic amount.

[AndyF]

I should add that I also agree with Graham that it points to more of a mechanical issue than an ECU/mapping problem.

Have you checked that the fuel pressure regulator is working correctly by fitting a gauge on the fuel rail and monitoring it when you come on boost?

Andy

[toyotec]

So after an engine rebuild you've gone from a 0.81 to 1 lambda without changes to the map?
Sounds more mechanical than mapping related, unless you've changed the spec/capacity of the engine by a drastic amount.

Initially I suspected the same and yes map tables cannot change themselves.
In fact I really do think the fuel mixture targets have not changed at all. If say the issue was fuel pressure related than I would not expect the fuel pressure to change with an increase in boost pressure. Plus the pump has been updated. Also just off idle condtions I would expect to have the full abilty to switch off closed loop control to run off the main fuel mixture tables. During my investigation to establish why the engine had an issue, I noticed this problem with the defination.
It should be noted that I was not there when the engine developed a problem and have to rely on other accounts to determine how to rectify. I was told about this and visited the garage concerned to have look at the engine and try to investigate what may have happened. IMO there were signs that the engine leaned out and started to PI leading to loss of power. Mechanically the engine is fine once again and I have returned to check the calibration ( as well the rest) when I noticed this problem in the XDF. Now I do not know if at 5000rpm and onwards @ WOT if the fuelling would switch to open loop and did not what to try. But at stioch during transients as the boost builds to 1.2 bar I would not be happy.


I should add that I also agree with Graham that it points to more of a mechanical issue than an ECU/mapping problem.

Have you checked that the fuel pressure regulator is working correctly by fitting a gauge on the fuel rail and monitoring it when you come on boost?

Andy

Yes. The vehicle is fitted with an adjustable FPR+guage referenced to manifold plenum. While I operated the vehicle on the rolls another assistant looked at the gauge as the boost increased to 0.9bar and sure enough the this delta was displayed on the gauge.

I plan to return to the vehicle on Thursday, test the revised defination and calibration and once happy look for any other issues on the engine that might have influcenced what happened as described to Graham.

I agree it does sound strange, even to me the way I describe this problem.

Regards

[AndyF]

Have you checked that the base fuel pressure is correct as well Eddie?

If should be 3 bar with the vacuum hose disconnected from the regulator.

Andy

[toyotec]

It was 2.7 bar pre pump change.
I set the fuel pressure at 3.0 bar with vac hose connected, so if anything the vehicle should run richer on the current WOT fuel settings.

[AndyF]

Again, this may sound basic but have you checked that the injectors are the same in the new engine?

Andy

[toyotec]

Again, this may sound basic but have you checked that the injectors are the same in the new engine?

Andy

The injectors are the same 800 cc units from the last build. The engine is the same, just rebuilt.