Braineack

iTrader: (62)

define "real world value"

80% of us probably still don't use incorporate AFRTargets yet, but we aren't real.



that's the the cause of his issue.

this is like saying: 3 + 4 = 7 but that's not real world **** -- you need to start solving for 7 by adding 5 and 2 instead.

Ted75zcar

iTrader: (2)

Where did you tie the Kelvin sense (this is the feedback wire to the alternator)? This is the voltage the alternator regulates, and IIRC is on the injector power net in my NA.

Ted75zcar

iTrader: (2)

First of all, I hope your stat is wrong!

Real World Values - values that are actually representative of the term they represent in the fundamental fueling equation. In other words ... Volumetric efficiency. The ratio of the volume of air drawn into the cyl vs the ideal volume as calculated by the chamber dimensions.

Ted75zcar

iTrader: (2)

Dude this is control systems 101 type stuff. You need to get the proper plant with gain in order to normalize the transfer function.

Ted75zcar

iTrader: (2)

Triple baby!

So to help clarify a bit...

Any fuel related compensation that uses the arbitrary adder % is in the control loop and will have additional error if not using AFRTarget.

Any fuel relayed value that uses an adder with units (msec for instance) is outside the loop and not impacted.

Now to be honest, I have not looked under the hood and reviewed the MS firmware, but that is mainly due to the fact that it acts like it is coded the way I would design it thus far and I haven't seen the need.

Braineack

iTrader: (62)

yeah we use it as fuel map, not a ve table.


you wanna know the difference between it on and off?

PW = REQ_FUEL * VE * MAP * E + accel + Injector_open_time

vs.

PW = ([REQ_FUEL * VE * MAP] / [14.7 / AFR Target]) * E + accel + Injector_open_time

Ted75zcar

iTrader: (2)

Unfortunate, but it does explain a lot.

Ted75zcar

iTrader: (2)

Yep... See all the terms that get fooked? How can anybody unlock the powah?!!!

Braineack

iTrader: (62)

They simply tune in a different manner than you, unlock the same amount of power, and move on with life?


I will say that incorporate AFR is probably the better way to go. But both can/will achieve the same end result: In one way you're tuning your VE table directly to the AFR targets you want to hit, the other way you're tuning your VE table to stoich and applying the ARF targets into the fueling algorithm.

Ted75zcar

iTrader: (2)

Hmmm, well as someone who routinely works with much more complex control systems, I am going to have to disagree with you on this point.

Braineack

iTrader: (62)

common core math: the way you reached the answer much more important than answer itself.


all this aside: if something else is afoot preventing him from getting a good tune without AFR targets as part of the fueling algorithm, including them isn't going to solve the problem.

Ted75zcar

iTrader: (2)

While it is obvious based on the 80% stat that this discussion belongs elsewhere, I encourage you to consider the error term associated with each dependent term in the previously posted equations... Keep in mind we are talking about a product operation

Ted75zcar

iTrader: (2)

There is something else wrong for sure, several thing actually. For instance, in the regions where he targets AFR 14.7, the equations are equivalent. He is reporting a true VE there on ~80%

We all know how well the heads (even the BP4W) flow on these cars, and how the efficiency of the internal combustion engine varies with manifold pressure ...

He most likely has an error someplace that is corrupting the req-fuel number.

There are obviously HW things that could cause this as well.

The edge scalloping on his fuel map (uhg) ... Also tells us stuff.

One problem at a time though I think

Chiburbian

iTrader: (1)

Here are my maps. I did some manual adjustments to smooth them out in the low load areas. Also, not sure what to do at the extreme low rpm areas.

This is WITH incorporate AFR active




Could it have something to do with my lambda delay?

Ted75zcar

iTrader: (2)

Looks to me like you are delivering less fuel than the MS thinks. I am not as familiar with the VVT typical efficiencies, but I would be very surprised to hear that you get anywhere near the VE your map displays. Remeber to use the actual stoich of the fuel you use for the req fuel calculation. We only have E10 at the pumps here, so I used a stoich of 14.1. This is NOT the same number for the AFR table, which is based off of lambda and scaled for gasoline (14.7). You want to leave that with the typical AFR targets for E0, your wideband takes care of the scaling there automatically.

Have you performed any head work? Did you accurately calculate the actual injector flow at your measured fuel pressure?

Ted75zcar

iTrader: (2)

The left side scallop could be due to delay. What is your target idle? It is common practice to tightly window the target idle in both the RPM and load domains.

RichieVee

I had to register just to make this point.
The engine doesn't care what control strategy you use. If the amount of fuel being injected gives a certain AFR, that's all that matters.
The ONLY difference is the number you put in a box.

I'm a calibration engineer for an oem engine manufacture and I work with complex control systems.

The benefit of including the AFR table in the calibration is you can alter the afr as simply as changing the afr table.
But why would you calibrate to an afr you don't plan to run with?

Braineack

iTrader: (62)

8 likecats for this post.
:like cat:

Ted75zcar

iTrader: (2)

While I repect that you work in industry, I am going to have to disagree with this statement. I have been wrong before though!

When you draw a simplified block diagram of the control system, the error in VE propagates through to all of the corrections. Additionally, since it is nearly impossible to hold the other inputs in a static state, the autotuner will compound the errors associated with thise terms.

Ted75zcar

iTrader: (2)

This sir is exactly the point. How do we determine how much fuel to deliver?