Acceleration Enrichment and Over-Run Fuel Cut

Back !

The next things to take care of under fuel tuning is Acceleration Enrichment and Over-Run Fuel Cut, stay tuned... :)


Acceleration Enrichment - AE:

What is AE and why do we need it - and what is EAE... ?
AE is a function that takes care of fuel when you go from TPS 0% to TPS >0%.
Why is it needed ?
When the throttle is unpressed (TPS=0%~)  and you press the throttle (TPS>0%~) you open the throttle body and let air in the manifold, the engine goes something like, "mmm OK, air is good but what about fuel.... mixxturree tooo leeeaaannnnn I CAN NOT RUN ! HELP !

Same happens when you start moving, shifting gears or just rev it.

What we want to do is, let MS know how much fuel to add (Pulsewidth added ms) when rapid change in TPS is sensed.

Picture:

You can just try the settings in the pic.

Lets go over a few options:
- Accel Enrichment MAPdot<-->TPSdot Blend(%)
You choose if you want AE to work with MAP or TPS as guideline.
If your TPS is good and not too noisy - choose 100% TPS

- Accel TPSdot Threshold (%/s): 
TPSdot = TPS + "dot" part is "derivative over time", speed of change.
The threshold is the point you want AE to kick in.

You can start with the second way I used to tune AE. (Scroll down a little)

You want to log the situations where your TPSdot makes you lean & impact drive-ability.
Static rev, gear shifting etc'.

In the log you will see what TPSdot level makes you lean.
These are the points you want to fix and let AE make them less lean - more rich.

You can see in my log:
TPS (green) going from 0% to 90% fast - around 200 %/sec TPSdot,
TPSdot - white
AFR (red) going lean 20:1- the spike

Pulsewidth Added ms (yellow) - because of the lean AFR you can understand that "added ms" is too low.

Tune the AE until it is not too lean or too rich, numbers aside, drive-ability is your first priority.

Even if the numbers are not perfect (never will be) and car's running smooth - stop right there !

EAE is Enhanced Acceleration Enrichment, it goes dipper into fuel AE management and is targeting low speed throttle movements with high resolution AE.

Haven't touched it yet, AE works good for me, but maybe some day....

Updated way to tune AE:

1. Zero out all AE "Added ms".

2. Set four TPSdot points. (slow tip, medium, faster and fastest)

3. Set a good TS dashboard to work with...

4. Start with idle rev, try to test the first TPSdot you set until you see the AFR not spiking (no 20:1, more like 14-16:1, no less)

5. move to the next TPSdot and repeat 4.

Set AFR as a "Line graph" under "Gauge style".

Helped me alot !

Turn off Over-Run Fuel Cut, when tuning AE !

Over-Run Fuel Cut

After I got AE tuned so good with Over-Run turned off, I need to look deeper into it before i turn it on again...

Wanna get better mileage ? good. Turn it on then,

Over-Run Fuel Cut: will shut off the fuel to the engine. tune it right and forget about it.

You can try my settings:

More to come...

Fuel Tuning and Settings

On the menu today:

• WUE - Warm Up Enrichment
• AFR Table 
• Incorporating AFR in to VE table
• VE Table
• EGO - Exhaust Gas Oxygen
• AE - Acceleration Enrichment 
• Over-Run Fuel Cut

WUE - Warm Up Enrichment

Warm up enrichment, is there to help a cold engine run smooth up to operating temperature.

Normally when warm (85C-90C) the enrichment will be 0, meaning 100% of VE table.

Registered TS (TunerStudio) can auto tune WUE, works great.

If you tune it yourself you want to increase VE % just above the point where the engine is straggling when warming up, try to keep it around 14.7 or a little richer.

Before we start tuning the fuel, I want to explain my strategy.

1. Setup AFR table

2. Enable a cool feature that will make VE tuning very simple.

3. Tune VE table to reach the AFR targets we set in AFR table.

AFR Table:

Is the table that holds your "wish list", where you just put in what AFR you would like to see in each area of the engine operation range (idle, cruise, boost, deceleration etc')

Guidelines:

For idle I found that an AFR of 13.5 is great for me. (Probably because of batch fuel injection, I believe when I will upgrade to sequential injection idle AFR will be 14.7:1)

Cruise 15-16
Deceleration 15-16

Boost 11.5-12

This is my AFR table, it's aggressively lean.

Cool feature:

What we just did is telling the MS to use the value from the AFR table when calculating fuel to squirt.

Meaning, after finishing the first VE tune to match the AFR table we will not need to touch the VE table again (no need to tune the VE any more...)

Any change we want to make to our fuel map we will make through the AFR table.

Example:

Your cruise AFR is 16 and it is too lean(misfire), all you have to do in order to change it, is just to change the AFR cells you want in the AFR table.

Because the AFR target value is incorporated in the fuel calculation, the VE outcome (squirt) will change accordingly.  

Got it ? good.

VE Table:

This is how you look at a VE/AFR table:

This table is for naturally aspirated engine - idle, cruise and deceleration are the same for forced induction.

The 95-100 kpa range you can set up leaner and 100-200 kpa you scale from 13 to 11.5.

In the picture you can see that cruise cells are 1100-2000 rpm and 45-75kpa, could be your car cruises in a different rpm/kpa range - log it, check it, and AFR it accordingly. 

After you got your AFR table right you can auto tune or manual tune till the VE table reach the  AFR target table.

Now we have a nice AFR table, tuned VE table and an easy way to tune without tuning ;)

Next we need to look at EGO - Exhaust Gas Oxygen.

This nice little mechanism will help us keep our AFR right even at different CLT and IAT.

Works great !

Important pointers:

Controller Auth: is the max VE % you allow the MS to change.

Next: AE - Acceleration Enrichment and Over-Run Fuel Cut

Basic idle settings

In order to start tuning we need to stabilize the idle, this is just basic settings in order to get us going.

Overview:

Engine off:
1. Idle ignition
2. Idle fuel/AFR
3. Idle control setup
Engine on:
4. Idle valve test
Engine off:
5. Idle Cranking Duty
6. Idle Warmup Duty

Let's go...

Engine off:

Open your "Ignition Table 1 (Spark Advance)", your normal idle should be around 30kpa (no ac, no lights, no stereo etc...)

Set the idle cells at 14-16 - Read Rev1.1

Open your "Fuel VE Table 1" and set your idle cells with the same number (57 is good for me, your number maybe different to begin with)

Idle control basic settings:

Open "Startup/Idle" ---> "Idle Control"

Set it up like in the picture below:

Engine on:

"Batch Injection" cars will need to run idle a little rich even <14:1.
"Sequential Injection" can run 14.7:1.

Now start your engine and let it fully warm up, now check your AFR gauge, try to get the AFR that is right for your injection method and your engine.
If you are too lean use higher number in the fuel idle cells.
If you are too rich use lower number in the fuel idle cells.

When the idle is right (AFR) the engine will tell you, listen to it.

Now we need to test the idle valve range (gives air to the engine when throttle is closed)

Open "CAN bus/Testmodes" ---> "Output Test mode - Idle Valve"

Start the test at 0% and increase the % until rpm start raising - write the % you have found down.

Continue increasing the % until rpm will not raise any more - write the % you have found down.

Stop the test.

Engine off  !

In my car I found:

0% valve = 26

100% valve = 65

So my valve 0-100% range is 26-65, 26 is closed and 65 is fully open,

Now you can set up your "Idle Cranking Duty/Steps", how high you want the rpm in the first few seconds after engine started.
Usually you would want high when cold low when warn, but both of them should set the rpm around 1500rpm.

Every time you start your engine after you set up this curve, pay attention to the rpm, and adjust the curve to your liking.

Now we'll  setup the "Idle Warmup Duty/Steps" table.
Open "Startup/Idle" --->  "Idle Warmup Duty/Steps"

Here we set up how much valve (air,rpm) we want to add at a specific CLT temp, when cold we need more valve when hot we need less valve.

Every time you start your engine after you set up this curve, pay attention to the rpm, and adjust the curve to your liking.

Not too difficult, after we will finish tuning all the basics and the car will be running ok for some time we will take a shoot at Close Loop Idle (automated idle mechanism) .

Base timing

Base timing tune:

Base timing tune is needed in order for the ignition map to have/use real ignition degree values.
In order for your degree timing numbers to represent a real world outcome.

 10 degree in ignition map = 10 degree in real world.

In order to align that, we need to use a timing light gun

Tooluxe Xenon Automotive Timing Light - Cheap and works
That's what I got.

Now get your timing right !

"Ignition Settings" ---> "Ignition Options / Wheel Decoder" ---> "Fixed Advanced" ---> "Fixed timing"

"Ignition Settings" ---> "Trigger Wizard"

You must know/find your crank pulley marks for TDC and 10 BTDC

Get the marks aligned like in the picture above.

Check the timing at higher rpm upto 6-7K, if the marks move then align them at higher rpm - it is more important then lower rpm alignment.

After you finish, remember to change "Fixed timing" back to "Use table"

"Ignition Settings" ---> "Ignition Options / Wheel Decoder" ---> "Fixed Advanced" ---> "Use table"

Sensors and out puts calibration

Let's start with the basic check list:

1. Install the MS(Meagsquirt) in the car.
2. Install TS(TunerStudio) on a laptop and check connectivity to the MS.
3. Start a new project and set it up.
4. Configure "Required Fuel"
5. Verify all the sensors communicate with TS.
6. Load base maps for your car/engine.
7. Car starts ? good ! turn it off, does not start ? check 1-4.
8. Base timing light gun test.

Tuning order:

Required Fuel:

Setting up "Required Fuel" right will make an injectors change easy and simple.
If you do not set it up you will have to tune again...

Nothing much here, just type in your engine displacement, number of cylinders, injector flow and stoich  AFR for your engine (gasoline is 14.7:1)

Set it up right on your first steps will make injectors change (to smaller/bigger) EASY.

Do it !

Engine off:
First thing to do is calibrate your sensors.

Calibrate TPS - Throttle position
Calibrate Thermistor Tables --> IAT - Intake air temperature (GM open element IAT sensor)

Calibrate Thermistor Tables --> CLT - Coolant temprature (Original Mazda CLT sensor)

Calibrate AFR Table - Air fuel ratio sensor - Wideband - If connected to MS.

Are we good ? ok.

Next we need to setup our "Programmable on/off outputs", in my case I had only the radiator fan behavior to setup.

Check "Enable" to make the settings operational

Set "Power On Value" to "Off" - default behavior of the fan is off.

Set "Active value" to "On" - when triggered we want the fan to start.

Set "Output Channel" to "coolant" 

Set ">" - meaning only when the coolant is > (higher then...)

Set "Threshold" to the temp you would like the fan to start at (90C-95C I think is normal)

Set "Hysteresis" to how much coolant temp should drop below threshold before fan off.

Hey !

This is my new blog, it will be about my Mazda MX5 Miata and the Megasquirt I installed.

Tuning stuff that I learned through my feet.

Let's start and see what happen :)