Volumetric efficiency

[SactoShadow]

So I've been reading up on engine tuning, and I'm trying to apply the theories I've read about into MPTune.
The books are telling me the first place to start with is volumetric efficiency. For speed density systems such as ours it is expressed as a function of MAP vs RPM. I'm having trouble finding this table. My Shadow has had cylinder head work, including larger valves, so I want to adjust for this change within the tune. I also have a custom cam I would like to add later on down the line, and would like to be able to tune for it.
I keep seeing people referencing the pumping efficiency by RPM (fuel>modifiers>PumpingEfficiency FromRpm) . My initial thought was that this table reflected fuel injector pumping efficiency, since it was in the fuel table. Starting to think I was wrong...
Can you guys help me get this all sorted out? I think once I can tune for the flow of air through the engine, fuel and timing seem pretty straight forward.

[ShelGame]

The older cals have the pumping efficiency table. It basically scales the injector PW based on RPM. Its not truly a Volumetric efficiency table. That definition doesn't work for turbo engines. Its really a mass efficiency table.

[5DIGITS]

The information below is being will hopefully provide a high-level overview and some common mistakes.

To answer your question:
The injector PW table (idle, part throttle, or WOT) is multiplied by the efficiency table such that the injector pulsewidth compensates for air flow changes, throughout the operating range of the engine.
In other words, the pumping efficiency table is properly adjusted when a constant PW from the injector table (idle, P/T, or WOT) will yield a consistent A/F ratio, as the engine goes from low RPM to high RPM, at a selected load.


Additional:
FUEL:
The pumping efficiency table does not directly translate to the injector being used - (i.e. putting in +40% injectors does mean 40% can simply be subtracted from the table and considered done)
Only as an example: This approach would have the low RPM portion of the table near or at zero percent, with an excessively large injector; therefore the injector table for idle, P/T, and WOT ALL need to correctly adjusted.

SPARK:
Spend as little time between -4 and +4 degrees of spark advance as possible.
Although retarded timing helps a turbo spool, spark advance values between -4 and +4 degrees hammer the piston and the forces are directly translated to the rod bearing.
Its not wise nor recommended.

TEMPERATURE COMPENSATION:
These can typically be left alone and should always be at zero (0) adjustment within the normal operating temp of the engine.
Why? Adjustments to these tables while the adaptive fuel control is active supports unstable controller learning.

BOOST CONTROL:
The duty cycle adjustment table should only be used to correlate the solenoid duty cycle with the actuator, the turbo being used, and to insure the adaptive adjustment is within the adjustable range.
It should not be used to raise or lower a boost goal target.
To give an engine a chance at long life, use the engine temp based boost goal table.
There are many calibrations out there with one boost max value in the table for all engine temperatures - no high boost on a cold engine.


For every calibrator, there is a resulting calibration which translates to 'there are multiple ways to accomplish a result but not all of them are correct'.
Minor adjustments made one at a time is certainly very time consuming but it provides the needed feedback to insure things are headed in the right direction.

Thanks and enjoy.

[SactoShadow]

So then I guess my question is, does mptune even have anything that models the flow of air through to the combustion chamber?
The mass of air entering the combustion chamber will change based on port work to the head and changes to the camshaft, holding temp and MAP constant. Wouldn't the ECU need to know how much air enters given these modifications?

[SactoShadow]

The information below is being will hopefully provide a high-level overview and some common mistakes.

To answer your question:
The injector PW table (idle, part throttle, or WOT) is multiplied by the efficiency table such that the injector pulsewidth compensates for air flow changes, throughout the operating range of the engine.
In other words, the pumping efficiency table is properly adjusted when a constant PW from the injector table (idle, P/T, or WOT) will yield a consistent A/F ratio, as the engine goes from low RPM to high RPM, at a selected load.


Additional:
FUEL:
The pumping efficiency table does not directly translate to the injector being used - (i.e. putting in +40% injectors does mean 40% can simply be subtracted from the table and considered done)
Only as an example: This approach would have the low RPM portion of the table near or at zero percent, with an excessively large injector; therefore the injector table for idle, P/T, and WOT ALL need to correctly adjusted.

SPARK:
Spend as little time between -4 and +4 degrees of spark advance as possible.
Although retarded timing helps a turbo spool, spark advance values between -4 and +4 degrees hammer the piston and the forces are directly translated to the rod bearing.
Its not wise nor recommended.

TEMPERATURE COMPENSATION:
These can typically be left alone and should always be at zero (0) adjustment within the normal operating temp of the engine.
Why? Adjustments to these tables while the adaptive fuel control is active supports unstable controller learning.

BOOST CONTROL:
The duty cycle adjustment table should only be used to correlate the solenoid duty cycle with the actuator, the turbo being used, and to insure the adaptive adjustment is within the adjustable range.
It should not be used to raise or lower a boost goal target.
To give an engine a chance at long life, use the engine temp based boost goal table.
There are many calibrations out there with one boost max value in the table for all engine temperatures - no high boost on a cold engine.


For every calibrator, there is a resulting calibration which translates to 'there are multiple ways to accomplish a result but not all of them are correct'.
Minor adjustments made one at a time is certainly very time consuming but it provides the needed feedback to insure things are headed in the right direction.

Thanks and enjoy.

Thanks for the extra info!
The boost one is one I may have gotten tricked by.

[5DIGITS]

So then I guess my question is, does mptune even have anything that models the flow of air through to the combustion chamber?

Modeling the flow profile, swirl, tumble, port wetting, re-wet after decel, etc... - No.
A course/global compensation table that coincides with the air-flow characteristic of the engine - that's the pumping eff table.

The mass of air entering the combustion chamber will change based on port work to the head and changes to the camshaft, holding temp and MAP constant.
Wouldn't the ECU need to know how much air enters given these modifications?

Yes.
This is the short-coming of a speed density system vs a MAF system and where the accuracy of the calibration becomes critical.

Thanks for the extra info!
The boost one is one I may have gotten tricked by.

Not a problem and many have and still do.

[Reaper1]

You can work the problem in reverse, if you have a properly tuned engine. If you know the injector size and you know how much those injectors flow at a given pressure (in a boosted engine's case this is the differential pressure between the fuel rail and the manifold pressure...it should stay constant unless you are using a rising rate regulator), then you can monitor the injector duty cycle and know how much fuel is being introduced into the engine at a given rpm. Based on the A/F ratio, you can then figure out how much air the engine is using.

This isn't perfect, but it should get you in the ballpark.

Another thing you could do is if you have a way to monitor the compressor wheel rpm, and you have access to a compressor map, you can then use the compressor map to figure out mass air flow based on the rpm and the compressor pressure ratio. This would be a more accurate way to do it, but getting that wheel rpm isn't exactly easy.

[zin]

I've often thought about installing a calibrated venturi or MAF meter from another application to quantify the air flow and possibly adjust the tune, though integrating it into the existing electronics is a bit beyond my capabilities.

My main goal was/is to provide a reasonably accurate air flow number that I can compare to the "ideal" line shown in HPTune, which, in theory would allow me to tweak the eff table to match my indicated air flow...

Sounds complicated I know, but it should simplify tuning, if it works the way I think it should...

Mike

[SactoShadow]

Ok, so I think I'm getting this.
To start with the tune, after scaling my injectors (I will be putting larger injectors in) and adjusting for the AFR I want at given RPMS. I then run the car, and data log. Based on the actual AFR I adjust the pumping efficieny to get the AFR to where I want it.

I believe I read somewhere that people will remove the wastegate to keep boost from building while doing this.
From there I will get into spark, but one step at a time =D Hoping the equipment arrives soon.

- - - Updated - - -

Thanks for all the help guys! I really appreciate it.

[ShelGame]

FWIW, MP Tune has a utility to show you where to move the PEFTBL to based on an AFR input data set...

The data has to be very 'clean' for it to work well. IE, you MUST be in open loop and no transients (constant throttle, MAP). If not, you won't get a good result with it.

[cordes]

yes, as little boost as possible. Drag the brakes to keep the car at a certain RPM while at WOT. Stay at that point for as close to one minute as you can and then take your readings. Do this every 500RPM through the range and you'll have a perfectly adjusted pftbl in no time.

[wowzer]

Re rob l post ......Might be helpful to explain what tables to adjust. For example, do the cals allow you to force open Loop, ie disable all the closed loop fuel trim adjustments. Is there a table to disable any decel fuel adjustments. If I recall you can require the data that is read in to have a minimum number of hits to be considered usable. Also could edit the logged data to get rid of superfluous data.

I would love to see a pic of the data loaded in and displayed on the peftbl. Also would like the actual data file to play with!

Sure wish we had a 3d table for VE that incorporated map.

[wowzer]

yes, as little boost as possible. Drag the brakes to keep the car at a certain RPM while at WOT. Stay at that point for as close to one minute as you can and then take your readings. Do this every 500RPM through the range and you'll have a perfectly adjusted pftbl in no time.

Could you just unhook the intake piping so it doesn't boost?

[zin]

Could you just unhook the intake piping so it doesn't boost?

You could, but wouldn't want to, not without also disconnecting the wastegate, as the turbo would over-speed trying to make boost, even though it never could...

I suppose one could partially plug the outlet hose to give some resistance to the compressor, and still have some of the back-pressure the turbo would normally see, but I'm not sure that would be worth the effort...

Mike

[cordes]

You could, but wouldn't want to, not without also disconnecting the wastegate, as the turbo would over-speed trying to make boost, even though it never could...

I suppose one could partially plug the outlet hose to give some resistance to the compressor, and still have some of the back-pressure the turbo would normally see, but I'm not sure that would be worth the effort...

Mike

I would hold off on disconnecting the charge tubing at all. I've had great results with it hooked up and I think you could still go a pretty long way to overspinning a turbo even with the WG flapping in the breeze if it has zero resistance on the compressor side.

[5DIGITS]

Could you just unhook the intake piping so it doesn't boost?

As 'Zin' already indicated, you could but it should be avoided.
The inlet plumbing, ducting, and it's effects on intake tract tuning should all be in place when this is done.

Brian, I agree but to define a starting point that will support further refinement I'd reduce the time at load and target 1000 - 5000RPM at 1000RPM increments.
This will minimize elevated engine temps due to time at load and provide values that will have the car driveable.
Once this is accomplished, a more refined approach (smaller RPM steps, extended time at load, a review of the injector PW tables, and elevated RPM's) can be pursued, to insure a stable tune.

What size injectors are planned for the car??

[ShelGame]

Sure wish we had a 3d table for VE that incorporated map.

The 3D cals do, for all intents and purposes...

V6 cals have 2 PEFTBLs - 1 for WOT and 1 for P/T...

[SactoShadow]

So I was toying around with mptune. I changed injectors in the program and rescaled. The pumping efficiency didnt change though. Shouldnt pumping efficiency scale down with larger injectors?

[ShelGame]

So I was toying around with mptune. I changed injectors in the program and rescaled. The pumping efficiency didnt change though. Shouldnt pumping efficiency scale down with larger injectors?

No. That was the point of 5DIGITS first post...

[SactoShadow]

No. That was the point of 5DIGITS first post...

AHA! I had to read his post several times again but I think I got it.