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Engines runs very lean at high load and rpm Motec M130

Understanding AFR

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Hi! Today I tuned an engine for the first time! However I had a problem.

At high load and RPM my engine was running very lean at around 1,4 lambda. This is obviously very bad. On the rest of the range the engine worked perfectly. This leads me to believe it was a fueling issue. However, the injectors are properly calibrated, of the correct size and the duty cycle remained well below 100%. I increased the regulated fuel pressure twice with no change in the whole range. To me this indicates everything works as designed. As far as I can tell the fuel pump is of enough flow. There were no pressure drops during the runs.

In order compensate for the lean fueling I increased the volumetric efficiency in the lean parts however it was not enough. Even with that the lambda got up to 1.4.

Was there an engine speed limit active? If the ignition or fuel is cut, you would naturally expect a super lean lambda value as uncombusted air is passed through the engine.

Be sure not to tune the efficiency value when the engine is not in the normal operating conditions.

We can provide more help if you will post a logged data file showing the problem.

No engine speed limits were active. Ill get some logs uploaded here by monday.

Uh, thing that IMMEDIATELY comes to mind is the lambda is wrong- I doubt the engine would even run at that https://ftyracing.com/tech/lambda-afr-table/ - and there's an issue with either the sender, the type selected in the ECU, or both. Different lambda types may have different characteristics, and if the wrong one is selected, or the wiring is wrong?

However, two main reasons it could be correct, and there actually is a high excess oxygen being detected -

that could be caused by an exhaust leak, or other factor, that is allowing air to be drawn ino the exhaust. Many people have the false impression that the exhaust is always under pressure, and it's impossible for air to be drawn in - this is false as there are several ways the pressure can be lower inside the pipe, such as venturi effect and/or pressure pulses/fluctuations. Poorly sealed slip joints are another common issue.

there is an ignition misfire, or incomplete combustion, that results in un-used oxygen for the sensor to pick up. The first is quite simple to understand, but an excessively RICH misfire may also be occuring - it is certainly possible for an excessively rich mixture to compromise efficient combustion, and you've probably heard of a "rich misfire"?

I'd start with pulling the spark plugs and having a good look at them - they can tell you a LOT about what's happening in the engine, and there are many excellent, illustrated guides to reading them, on-line - cut the engine at the higher load/rpm point so the reading is at that point.

While I was at it, I'd check the coil(s) values, the HT leads' resistances, and the wiring. The spark plug heat range, and the spark plug gap - you don't say if it's N/A or forced induction, but might be worth bringing them down to around 25 thou', maybe 20 for a higher boost/OEM coil engine, to see if that makes a difference.

After that, I'd carefully go over the exhaust and look for any indications of leakage - usually, but not always, can be seen as sooty discolouration - and if possible I'd replace the lambda, using a lambda-friendly anti-seize grease. And check that corresponds to the type selected in the ECU. Oh, some ECU's have limited types they support natively, so some need to use an external 'converter' to an input they can read.

Oh, was forgetting - is the voltage to the ECU steady - if it increases with rpm, that won't help.

Forgot, for future reference, you should NEVER run an engine under load and high rpm with a lambda over 1.0, or so, unless you KNOW why it's at that value, and you WANT it there! - certainly not over 1.1, or so, as that is risking rapid engine damage, even on a N/A engine.

With the M130, it's going to either be the Bosch LSU 4.9 or the NTK UEGO sensor in use, as long as the M1 has been set to use the correct LTC Type then that should not be an issue.

Look at the Fuel and Ignition Cut Counts, if these are incrementing, then in All Calibrate search for Cut, and see what cut is active by scrolling through the data in the Time Graph (pause the data first if you are online with the ECU). If there is a Cut active, work out why it is activating and either fix the issue that is triggering it, or change it so that that the trigger window is where it should be.

Have a look at 7: Monitor : 4 Complete Fuel Calculations and see if there is a reduction in the calculated Fuel Cylinder 1 Primary Output Volume number, This is the final value for the fuel calculations. I delete the Notes out of the bottom of the Complete Fuel Calculations worksheet and replace it with a Time Graph so that you can scroll through the run to see what the trends are, you can also add the Fuel Calculation channels into the graph for a visual representation. Also look at the other channels present on the page and make sure that there is not a implausible number in the any of the channels.

The way that the Complete Fuel Calculations page is laid out represents the process that the M1 follows to calculate the Fuel Volume required per injection pulse, so it starts in the Complete Engine Load Calculation sequence window, starting with Ambient Pressure and working down from there, then goes across to the Complete Fuel Volume Calculation sequence window, working from top to bottom again, then finishes with the Complete Fuel Film Calculation sequence. If any of the data in this calculation is incorrect, then all of the calculations following will be skewed by this.

Thanks for your answers. I checked and there is no exhaust leak. I wasn't able to check the spark plugs. I will at a later date. I'm including the logged data from the runs.

Attached Files

First up, Your Engine Efficiency table is not going to work in the way that it is currently setup, there should be a row for every 10kPa change with the type of engine that you are running. 25kPa steps are too coarse.

I do not trust the calibration of your MAP sensor, unless you are tuning at 800m ASL. close to see level, it should be reading around 100kPa with the engine not running, yours is showing 92.3kPa. As this is the primary load channel for the engine, if this is not correct, you will not get the fueling right. What looks like to be happening is that the MAP sensor is under reading the Inlet Manifold Pressure, and is thus under calculating the mass of air being inducted into the engine, so there is more air going into the engine that is being calculated, leading to the engine leaning out.

There may be more issues than this, but until this is rectified, there is no point in going further.

Are your injectors actually located after the throttle as configured, or before the throttle? Since your default Ambient Pressure is 94 kPa (but could be estimated lower by your Manifold Pressure Sensor when the engine is stopped). But the runs that show lean conditions have a Manifold Pressure near 75 kPa - so that could result in mis-calculating how much fuel will flow if the incorrect differential pressure is used.

Also, you are configured for E85 fuel mass properties -- are you actually using an 85% Ethanol fuel, or could it be different (since you don't have a fuel composition sensor). Fuel Injector Primary Flow Correction is there to deal with viscosity effects of E85 on injector flow rates. Were your injectors characterized with E85 or normal gasoline viscosities? If not, perhaps this needs a correction for your fuel.

I see the throttle aim is 100%, but only 75 kPa -- is this engine restricted?

Thanks for you answers. The runs were done in Madrid Spain we have an elevation of about 700 meters. The injectors are indeed after the throttle. I am using E85 and the injectors are designed to run that fuel. This engine is indeed heavily restricted.

As for the TMAP sensor, I am using the Bosch 0281002845.1.0 with the correct motec calibration.

I wonder if your issue is the that the "Engine Efficiency Mode" is set to "Airbox Air Density", which since you don't have an Airbox Pressure Sensor configured, uses Ambient Air Pressure, which is also a constant.

I suggest you change the Engine Efficiency Mode to Manifold Air Density.

Add more resolution to your Engine Efficiency load axis as suggested by Stephen, and then tune the Engine Efficiency table again.

Before getting too far into the Engine Effeciency table, make sure Engine Charge Cooling Gain is correct (see the help for this table for the procedure to calibrate it). Your values seems much too low for E85 in my experience.

It's good that you aren't giving the the Closed Loop Fueling much range to operate in while tuning, but when first running an engine, it's quite OK to allow it to add upto 25% fuel, avoiding those super lean cases under load. I suggest changing Fuel Closed Loop Control Trim Maximum to 25%, and Fuel Closed Loop Control Trim Minimum to -10% during initial tuning to avoid fouling plugs and the engine to running well enough to tune it.

I'm guessing this is a Formula Student car -- good luck!

The TMAP sensor is located on a plenum before the individual runners and after the throttle body.

The charge cooling gain was adjusted following the calibration procedure.

Thanks for the tips.

I have noticed a combined peak warning on the fuel output diagnostic. Might this cause a lack of fueling? Can someone explain what it might mean im struggling to fully understand what it means.

The plenum after the throttle is properly called the intake manifold. So you have it in the right place.

You might need to re-do the Charge Cooling Gain after changing the Engine Efficiency Mode. When doing that make sure the engine is fully warmed up, and you are in a loaded area of the table -- you want fair amount of fuel volume to see the effect -- if the value you determine is too low, then the result would be leaner than expected when the flow is higher -- exactly what you were initially describing.

Your injectors are identified as Peak & Hold. A peak and hold injector provides a higher current to open the injector, and then uses less current to hold it open. Normally the higher current is only held until the injector reaches that, then the hold current takes over.

The "Combined Peak Warning" says one of your injectors has reported a "Peak Warning" on it's Injector Cyl x Primary Output Diagnostic. "Peak Warning" in the help for that channel says "Peak Current was not reached before Peak Time elapsed". Your Peak Current is 3.0 Amps and the Peak Time is 4.0 ms. Perhaps you want to use an oscilloscope to see what current the injector actually draws when opening for > 4 ms (disconnect the fuel pump, and use the Test Output area of Initial Setup->Injectors tab, use 1000 rpm for the Test Engine Speed).

I notice you are using an injector calibration "Bosch 0 280 158 038 - 5 to 8 bar.1.0". That calibration says the injectors are "Peak and Hold", but the similar calibration "Bosch 0 280 158 038.1.0" indicates the injectors are of a "Saturated" type. I wonder if this is the cause of the Peak Warning, since that would not apply to a Saturated injector.

Can you use the Bosch 0 280 158 038 calibration, not the 5 to 8 bar calibration thanks.

I used the Bosch 0 280 158 038 calibration and I'm still getting very lean in the same range.

Attached Files

Seems like most have disregarded the reported lambda/AFR - either it's faulty, there's a signifant air leak post cylinder, and/or there is at least one cylinder which isn't firing. The engine wouldn't run if it was actually that lean.

You're going to need to check the lambda isn't faulty, is correctly calibrated in the software, and there is no air being drawn into the exhaust.

If all those are good, it may be dropping a cylinder, or two.

I can't remember what the engine you have is but, if it's a multi-cylinder, is it possible two leads/coils/injectors are out of sequence? If they're direcly opposite it may not be noticed as rough running? Small chance, but if it's the classic small block Chev', it had an early firing order of 18436572, but towards the end of its production it was swapped to 18736542, and this has caught some people out as the camshafts are different for the different firing order, and the irregular exhaust beat disguises the mis-fire.

If an in-line six, similar thing if, for example, 3&4 are swapped accidentally.

Hi thanks for your answer! The exhaust was checked for leaks and none were found. The engine is a two cylinder Yamaha CP2 and it runs quite smoothly. As stated in some previous answer the lambda has been checked and is properly setup.

Thank you, that helps rule those thoughts out.

There was someone a while back having issues with the same engine, can't recall what it was, but may be worth a search to see if it triggers any thoughts?

From what I can find about the CF5 engine, it is not an equally firing engine with a 270 degree cylinder spacing. Is it possible that there is some reversion occurring in the exhaust system that is causing the lambda reading to be acting to way that it is? How far from the exhaust tip is the sensor mounted?

The sensor is mounted 50 cm away from the exhaust tip.

Yes, Steven, it is a parallel twin with a "270" degree crankshaft. I had also thought of reversion, as damned if I can see how the engine is even running at a true lambda 1.4, and that's why I've been emphasising that side of it - whether the lambda is being reported correctly. But a half metre from the end should avoid that.

Alexander, when you've adjusted the fuelling, what affect did it have on the idle quality, rpm, and/or amount of throttle opening required?

Have you checked the sparkplugs to see if they indicate leaner, or richer, running? What sort of engine note does it have - lean tends to be a distictly sharper sound, like a crack, whereas rich tends to be a more muffled sound?

Sorry we aren't being much help, but I'd wager when you do find the issue it's going to be something of a "Doh" moment, like forgetting to save the changes, as happened to someone else a while back.

After changing the fueling the idle speed dropped with the same throttle opening. The spark plugs seem fine. I cant say for sure about the sound but it doesn't sound very sharp to me.

linked is the image of the spark plug of cylinder 1: https://imgur.com/a/sctPuim

inked is the image of the spark plug of cylinder 2: https://imgur.com/a/UuVXWt9

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