How to Tune an Evo TB Alternate

From EvoEcu
Revision as of 02:32, 4 May 2010 by EdwardMarshall (talk | contribs) (→‎What you need to modify)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to navigation Jump to search

Original Thread by Touring Bubble:  [forum now closed - original posting date04-30-2007]

Google Cache Version: Here

Note: Sections are broken up by original post-style

TB's guide to tuning with ECUFlash

From start to finish. Smilie thumbsup.gif


The goal of this guide is simple: To provide you with the knowledge and techniques needed to tune your Evo using ECUFlash. I'm going to go through the entire process of tuning the ECU, and hopefully give you the knowledge to make your fast car go faster.


I researched, tested, and compared tons of data before making adjustments to my car for the same reason that you should ... so you don't blow up your $30,000+ investment. You can trust that the data provided in this guide will be pretty darn accurate, but you should understand the risk you assume by modifying the values in your ECU. If you break anything because of this guide, it is not my fault... though I will feel kinda bad.

With that said, let's get started ...

First things first

Since you obviously want to know more about tuning your car, you should go ahead and read through this brief tutorial on EvoM written by EFIxMR. It quickly touches on some of the subjects that will be covered here.

If you read that article and are still awake, then you will probably be able to follow the rest of the tutorial here. I might get pretty technical at times, but if you have any questions, just post them here and I'll do what I can to get them answered.

What you'll need

Before you get started, you'll need a few basics. Some of these necessities are going to lighten your pocket a little, but you drive an Evo ... you can afford it, right?

Tuning Software

EcuFlash- Yes, let's assume you need the tuning software to tune your ECU. This software is a free download.

Logging Software

EvoScan- This application is available for download for $25 and is the software I'll be using to log in this tutorial. For your hard earned$25, you'll get the logging software and free updates. EvoScan is simple and easy to use. It also works with most of the wideband O2sensors you'll find.

MitsuLogger- Mitsulogger is a free logging software developed (mostly) by MalibuJack, who you might know from EvoM. He knows his stuff, and his logger reflects that. It's powerful and constantly being updated. If you have questions about this logger, I probably can't help you ...but, I'm sure MJ would be happy to help you out. You can find him on his own site, The Aktive Matrix, or on EvoM in the ECUFlash tuning forum.

LogWorks- LogWorks is a super powerful logging application developed by Innovate Motorsports and is packaged with many of their products. I have this software, but I honestly haven't used it much. I hear that it's a smart, fast logger that can do anything you want and more after you learn how to use it. Lots of tuners love this software and wouldn't trade it for the world.

(As of 8/15/08, LogWorks 3 does not include the OpenPort plugin needed to support the OpenPort cable used for logging an Evo. You must install a version of LogWorks 2 that includes this plugin.)

Of course, these aren't the only choices for logging data from your ECU. Find a logger you like and learn your way around it. You can use the information here with any logger you end up with.

And now, the hardware ...

OBDII Interface Cable

Logging Cable -This is the interface that connects your computer to your car. This cable is used when data is being sent to or being pulled from the ECU.

Boost Gauge

You need to monitor the boost carefully when tuning your car. A boost gauge is the absolute minimum you need. A better solution is to log boost with an added MAP sensor which will be discussed a little later.That said, I'm currently tuning using only the stock boost gauge that Mitsubishi left in the car for me.

Boost gauges are everywhere and range for super cheap to insanely expensive. Pick one and install it. If you want my opinion, I've had VDO and Stewart Warner gauges and never had trouble with either.

Wideband (5v) O2 Sensor and Interface

I'll give a little explanation here. You have 2 O2 (oxygen) sensors on your car from the factory. One is in the turbo outlet pipe, and the other is just past the catalytic converter. The first one tells the ECU information about the fuel mixture, and the second is used in comparison to the first to determine if the converter is doing its job.

Both of these stock sensors are what we call "narrow band" sensors. This means that they send signals from 0.00v to 1.00v. This technically isn't a problem and narrow band O2 sensors can be used to monitor air/fuel mixtures when tuning, but the stock sensors are calibrated in such a way that they only give accurate feedback at stoich (1 Lambda (λ), or 14.7:1 AFR for gasoline). This is because the ECU only uses data from these sensors in "closed loop" mode.

Closed loop means that the ECU references a signal from a sensor and compares it to a target value in the ROM, and can then make adjustments to values on-the-fly to reach that target. The stock ECU uses closed loop fueling at low load levels (idle, cruise) and the AFR target is 14.7:1, or 0.5v on the front O2 sensor. Stock boost control is also closed loop ... the ECU targets a specific load level for a given RPM and can adjust the duty cycle of the boost control solenoid for correction. More on that later.

There are crossover points defined (based on RPM, load and TPS voltage) that tell the ECU when to stop using closed loop fueling and switch to "open loop." Open loop occurs when the vehicle stops relying on sensors to give feedback and simply "trusts" the defined maps to be correct. In the case of AFR, the ECU used the data in the fuel maps and just kind of assumes that that mixture is correct based on the things it DOES know, such as the MAF reading.

So, in order to achieve the ideal fuel mixture, we need to know the specifics of the fuel mixture when in open loop mode, especially since open loop occurs during acceleration. We get this data by installing an extra O2 sensor that can interface with a gauge or computer. This is usually a "wideband" sensor that sends signals from 0.00v to 5.00v. The higher voltage range of the sensor and it's linear response allows for more accurate readings.

Here are some choices for a Wide Band Air Fuel Meter

Optional Hardware

Items listed here aren't required to properly tune your car, but a little extra info never hurt anyone.

MAP Sensor and Interface - Adding a MAP (Manifold Absolute Pressure)sensor will allow you to accurately record boost levels with your logs. This should give the same readings as your mechanical boost gauge, but logging the values allows you to compare your boost levels with the rest of your log and could possibly allow you to catch subtle pressure nuances that you might not spot on the gauge.

On the Evo, there is a nifty way to log boost with a part from Japan and some minor modification to your ECU. Read about that here. There are also many aftermarket kits that allow you to log boost.

EGT Gauge - I've personally never dealt with one of these doo-dads, but monitoring your EGT (Exhaust Gas Temperature) can keep you from making some big mistakes while tuning. If you want to go this route, you'll need to do a little research because I can't help much. If you get some info in it, post here and I'll add it. Beer.gif

So, you've got all of the necessities. Let's start tuning! Headbang2.gif

AAAHHHH! Lots of colors and numbers!

Alrighty, so you now have everything you need to get started. Let's get you familiarized with the software you'll be working with.


ECUFlash is the application that you will use to write to and from your ECU. It comes packaged with everything you need to get started, minus a ROM image from your car.

If you have your OBDII cable nearby, you can run out to your car and pull the image from it to use for this section. If you don't have a cable yet, just right-click and save this file and skip down past this part.

You know how to connect the OBDII cable to your car right? RIGHT? What do you mean you didn't read the article I sent you to above? Okay, fine! Here is is again.

So, you're plugged in a ready to go, right? Good. Open up ECUFlash. you'll be greeted with this screen ...


Now, take a second to get familiar with the buttons at the top of thescreen ...


Open ROM
This will open a saved ROM image for editing or flashing.
Save ROM As
This saves the edits you've made to the ROM.
Read From ECU
This connects to the car's ECU and opens the currentimage from the ECU in ECUFlash.
Write to ECU
This writes the selected ROM file in ECUFlash to the ECU.
Test Write to ECU
The goes through the same processes as the "Write to ECU" function, but no data is actually written to the ECU.
Compare to ECU
This reads the image from the ECU and compares it to the selected ROM image in ECUFlash. This process runs every time you write to the ECU, and only the modified ROM data is written to the ECU.

If you're connected to the ECU properly, the "Read from ECU" icon will be lit. Go ahead and click the "Read from ECU" icon. You'll get this prompt ...


Select the vehicle that you are connected to and click "Read" to begin transferring your current ROM image to your computer. When the process has finished, your screen should look similar to this ...


On the left side, you'll see "read image*" in the top box (BTW, that'*' means that the file has not been saved) and "ROM info" and "Parameters" in the lower box. This would also be a good time to save this ROM somewhere safe before you go poking around and changing stuff. Just click the "Save ROM As" button at the top and select a location.

(Those of you who used the ROM I linked to from above can tune back in now)

Before you start tuning, it's best that you know a little about the information contained in your ROM image, so I'll start there ...

The ROM Info section contains, well, info about the ROM you're looking at. If you expand that section by clicking the little [+] to the left, you should see info that reflects the vehicle it was pulled from ...


Most of the info here is self explanatory, but note the value of "Internal ID." This internal ID is often referred to as the "definition file." In the ROM pictured above, the definition is "88590015" and happens to be the most up-to-date Evo IX ROM. For info on the most up-to-date, supported ROMs, check the downloads page.

Now, below the ROM Info section is the good stuff ... the Parameters. These Parameters hold the data that controls the variables you will harness to fine tune the performance of your Evo. The categories within are pretty cut and dry. They include:

The fuel category includes the ever important fuel maps,as well as more advanced info such as the MAF and injector scaling tables.
The timing category hold your ignition and MIVEC maps.
Within the limits category you'll find the rev limit, stationary rev limit, and speed limit tables.
The turbo category holds a ton of important info. The tables here control the desired boost, wastegate duty, and overboost protection. This is probably the most confusing section of them all.
The most important data here is the immobilizer table. You'll need to set your user level to "Developer" to see this though. This category is also commonly used to store misc. tables you add to the ROM definition (we'll cover this later).
These isn't much here, but the tables within control your desired idle settings.

With that out of the way, we can start looking at maps. Yay!

There are 3 levels of maps in ECUFlash ...

A 1D map contains one address and a value for that address.
A 2D map contains a reference column of addresses and values for each address in a second column.
A 3D map cross references 2 address and assigns a value based on their relation.

Here are some examples of the different types of maps ...

1D: RevLimitMap.gif

2D: BoostErrorMap.gif

3D: FuelMap.gif

3D maps can also be viewed as 3D graphs, like this one ...


Reading the 1D and 2D maps is pretty straight forward, but the 3D map is a little more difficult. Basically, the ECU compares the 2 reference values on the X and Y axis then assigns the corresponding Z axis value. Take a look at the illustration below for more clarity ...


In the fuel map illustration above, the ECU is reading an engine load value of "180" and an RPM value of "5500." The cell where the 180 load column and 5500 RPM row intersect decides the fuel value, which is"10.1."

Now that you know how to read the maps, you need to know how to modify them. It is actually pretty straight forward and simple ...

"=" pops up a dialog box and allows you to directly input a value in to the selected cell(s).

"+" incrementally increases the selected value(s).

"-" incrementally decreases the selected value(s).

You can also copy and paste values to and from the maps using the standard Windows CTRL+C to copy and CTRL+V to paste. If you want to know more, check out the "Edit" menu in an open map window.

Okay, well that about sums it up for the basics of using ECU flash. Now it's time to find out what values we need to change and why ...

Pressure predicament

When I first started the tune for my car, I chose to begin with setting the boost. The reason for this was to hopefully reduce the amount of tuning needed later in the process.

By first setting the amount of air being shoved on to the cylinders, I could finish the first half of the AFR tuning without even touching the fuel maps. More importantly, the boost tables are directly related to the load values that the ECU uses as a basis reading values from most all of the tables that you will be editing while building your tune. By setting the boost first, you dial in the load values that you will be editing in the steps afterward.

Ways to tune boost pressure

There are basically two ways to set the boost levels on your Evo. You can install a boost controller, or modify the factory boost control system. Both have their pros and cons ...

Aftermarket BoostController

The main benefit of the boost controller option is ease of use. This option gives you direct, mechanical (or electronic) control of the boost level. Some options allow you to adjust the boost on-the-fly from the driver's seat, and that type of control is insanely convenient.

The downside of this option is mainly the amount of control you have over the boost levels. Some of the more expensive electronic controllers allow you to customize the boost curve based on RPM, but your basic manual controller does not.

ECU-Based Boost Control System

With this option, you have tons of control over the boost dynamics. You can dial out spikes and reduce taper. The method also retains the ECU's ability to reduce boost pressure in situations that might harm your engine. There is also a cost savings with this route as you can use the stock boost control solenoid.

With this method you retain the ECU's closed loop control of the turbo system which allows for some options you can't get from most manual/electronic boost controllers. Mrfred has really gotten dirty with this functionality in the ROM and has found different ways of controlling the boost level with the stock ECU. Read about those discoveries here and here (EvoM currently down).

Modifying the stock boost control system is also a little tedious and time consuming. There are many tables that interact with each other to make it all work, and when you start tinkering with the hardware that these values control, they can begin to act a little strangely. Also,to modify your boost setting with this option, you must re-flash the ECU which requires some time and a computer.

This method works with the modified stock boost control solenoid or other aftermarket 3-port boost control solenoids.

Controlling boost with an aftermarket boost controller

This is by far the easiest and fastest method to set the boost on your Evo. You simply remove the stock boost control system and replace it with an easy-to-adjust valve. Sung has already written a great tutorial on installing a boost controller, so I'll just send you there in stead of wasting time reiterating it all.

Once you have your boost controller installed, be sure to adjust it all the way down to avoid initial overboosting. Make some runs, preferably in 4th gear, and monitor the boost levels. Turn the boost up in small increments until you reach your desired boost level. Read the logging section further down for more info.

A stock Evo IX can easily handle 22 psi after the needle settles. A spike of 24 or 25 psi can be expected in the peak torque area. The boost is likely to taper down toward redline, but it should still be an improvement over stock.

If you have chosen to install a manual boost controller, you've basically rendered the ECU's boost control features useless, but there are a few tables you might want to change anyway. The "Boost Limit" and "Boost Delay Timer" tables still function with a manual or electronic boost controller, so you'll need to adjust them as noted below.

Controlling boost with the ECU

Grab a seat, because things are about to get interesting ...

For starters, controlling boost using the factory boost control system isn't 100% dependent on settings in the ECU. This is due to Mitsu installing handy restrictor pills in the OE boost control solenoid (BCS) lines. There is one pill just before the BCS on the pressure side and one in the short line just before the turbo. Modifying either of these pills will change the boost characteristics. Wrcwannabe gives some great info about the 2 pills in this post if you want to learn more.

If you plan to use the stock BCS, read Evo Kid's write up on stock boost control. You will need to follow the steps listed in his tutorial to modify the stock boost control pill for any information I give you to be applicable. Go ahead and read through that thread and head back over here after you have an understanding of the mechanical side of modifying for ECU boost control.

If you are using an aftermarket 3-port BCS you will remove the stock lines and the stock restrictor pills during the install. They are not needed for a 3-port solenoid setup.

Boost control tables

Before we get too far in to this stuff, you might want to set your user level in ECUFlash to "Developer". To do this, select "Options" from the menu up top. You'll see a user level section on the left. Open that up and select "Developer" from the pull down menu.

WARNING! Changing the user level opens up many other tables that we may or may not be using in this tutorial. If you don't know what a table is, don't mess with it. Setting values in ECUFlash incorrectly could possibly cause irreversible damage to your Evo.

On the Evo, there are no less than six tables that control boost. These tables are (in order of appearance):

Boost Delay Timer

BoostDelayTimerMap.gif This map works with the "Boost Limit" map to protect the system from overboost. This map is a timer (in milliseconds) that comes in to play when your actual boost at a given RPM exceeds the value set in the "Boost Limit" table. If boost exceeds the limit for a time greater than the timer's value, the ECU will cut fuel to protect the engine.

Boost Control Load Offset

BoostOffsetMap.gif This table is an offset value that is added to the values set in the "Boost Desired Engine Load" table. The sum of the values in these two tables is your desired engine load for a given RPM. If using Mrfred's PSI-based boost control, this table is not used. You will add another table with scaling in PSI. The new table will function the same as this one.

Turbo Boost Error Correction

BoostErrorMap.gif This table is referenced when the desired engine load differs from the actual load value. The difference in load (actual -> desired) is in the left column, and the amount of correction is a variable value in the right column. The percentage of correction is applied to the wastegate duty cycle (WGDC) to raise/lower the actual load to align with desired load. Again, when using PSI-based boost control you will create another error correction table with PSI scaling.

BoostDesired Engine Load

BoostDesiredMap.gif The values in this table are added to the value set in the "Boost Control Load Offset" table to determine the desired load value for a given RPM. This table is as close as you will get to RPM based boost control. For PSI-based boost control, you will create another set of these tables with PSI scaling.

Max Wastegate Duty

MaxWGDCMap.gif This map, also referred to as "Baseline Wastegate Duty," determines the initial duty cycle values of the BCS. If the actual load/PSI is not equal to the desired values in the desired boost table, the error correction values kick in and make adjustments based on the values here.

Boost Limit

BoostLimitMap.gif This table determines the max load value considered to be safe and acceptable at a given RPM. If actual load exceeds a value in this table for a duration greater than the "Boost Delay Timer" value, the wastegate will open to reduce boost pressure.

What you need to modify

Note: Before continuing this tutorial, be sure you've saved your stock ROM in a safe place.

Okay. You've got you modified boost pill/3-port solenoid installed and you want to dial in your boost settings. Lets go down the list of initial changes you will need to make.

WARNING! Do not drive the car with the modified boost pill/3-port solenoid before flashing the ECU with your new boost settings!

Boost Delay Timer

This map can stay where it is,but you can increase it if you feel the need.

Boost Control Load Offset

Increase this value to "100." Increasing this value will add some headroom to your "Boost Desired Engine Load" (BDEL) maps and allow for easier fine tuning later.

Turbo Boost Error Correction

You'll want to set the top half of this map (negative Boost Error %) to "0" and change the values on the lower half (positive Boost Error %) to make a gentle ramp of correction with a maximum of about "-5%." See the image below ...


These settings will protect you from overboost but not skew your logged Wastegate Duty Cycle (WGDC) values while dialing in boost.

Boost Desired Engine Load

There are 3 of these maps, and sadly, I have no idea why. So, the easiest way to proceed is to modify all 3 of the maps. This will ensure that you have the desired boost settings in any sutuation.

Set the BDEL in all 3 maps to "140" with a taper down to "100" from 5500 RPM to 7000 RPM. This value added to the load offset value of "100" gives you a desired load of "240" through most of the rev band, which is equal to about 22 psi in most cases. We're tapering down the top end to reduce heat and the chance of knock.

Max Wastegate Duty

Again, there are 3 maps. The same thing stands ... I honestly don't know which is which. Edit all 3.

Reduce the values in the Max WGDC tables to about "30." A setting this low is likely to not offer any boost control at all and you will likely see only wastegate spring pressure. Don't worry, we'll be adjusting this map a bit.

Boost Limit

Raise the values in this table to "270." If you're a little worried about overboost you can taper these values toward redline for safety. Just don't drop the values below about desired load+ 15 or you're likely to hit the cut a few times while adjusting your boost. You can also adjust these values to more tolerable levels after you've dialed in your boost.

Min Temp for Full Boost Control

This table is incorrectly defined, so leave it alone. Stock value is "85."

Time to log

Well, we haven't spoken much about logging. When you log, it's best to log the full RPM range from about 2000 to 7000, much like a dyno pull. This should be done in at least 3rd gear, but 4th is preferred if you have a safe location. You log in higher gears for several reasons:

  • In higher gears boost levels are less erratic.
  • RPM's climb slower, allowing you to log more data.
  • The engine is under higher physical load (not directly related to logged load %) and more likely to knock, allowing for a safer tune.

When you first start logging, it's probably best to log anything and everything you can since you will not know exactly what information you're looking for. As you learn more, you'll narrow down and re-arrange the information logged to suit you're tuning needs. However,you should always log these values:

  • TPS
  • RPM
  • Load % (I suggest performing the 2-byte load mod for more accuracy)
  • AFR from a wideband O2
  • Boost (if possible)
  • Timing Advance
  • WGDC (Here's how)
  • and, most importantly, KNOCK COUNT

Any time you log a run you will need to monitor knock count. Knock is a record of what may be detonation or pre-ignition, which is very bad for your motor. Ideally, you always want to aim for 0 knock count over your entire log. Sometimes a random knock count of less than 3 is acceptable if it isn't consistent. Knock counts higher than 3 (actually, 1 on a IX) begin to pull timing for safety, so you definitely want to stay below that number.

There is something called "phantom knock" than can be caused by shock or vibration. Phantom knock can be diagnosed by logging an additional pull in a slightly different location or by increasing the octane of your fuel. If the knock occurs in additional logs in the same RPM/load area even with higher octane fuel, then it is real knock and you need to adjust your maps to compensate. Phantom knock is very rare on lightly modified vehicles and should not be assumed without proper validation.

Knock is generally caused by factors you can control such as AFR, boost and timing advance. If you experience knock, look at the values in that RPM range and you're likely to see something out of wack. You AFR might be too lean or too rich, you might have too much timing advance or a dramatic jump in timing, or there may be a boost or load spike in the area. The more you tune, the easier it will be to find the issue and correct it.

Setting your final boost levels

To dial in your boost you'll have to log several runs. If you don't have a way to log boost levels, it might be a good idea to have a passenger watch your boost gauge and keep you informed in case something were to go awry. If none of these options are available to you, you'll just have to rely on your load levels which (for the most part) are parallel to your boost levels.

Remember, your ECU is aiming to hit 240% load but is currently being limited by the decreased WGDC. As you log, you'll notice that you're not hitting the load levels requested. After you log a run,increase the Max WGDC values in all 3 tables until you reach your desired load levels while constantly monitoring for knock.

If you experience knock, check your AFR and timing advance. You want an AFR below 11.3:1 or so. If your AFR is leaner (above 11.3:1), lower the AFR to correct for knock ... if AFR is between 10.5 and 11.3 and boost is conservative, lower timing advance. You will be fine tuning these values later.

After several runs you should have your WGDC dialed in to where it needs to be. When you are getting close to where you want to be, be sure to compare your WGDC logs to the Max WGDC table in ECUFlash. You may find that the numbers you are logging are slightly lower than what the maps define. This is caused by the error correction table making adjustments for overboost. Look through your log and locate the overboost area and adjust accordingly.

Your Max WGDC values should be lower in the 3000 RPM to 4500 RPM range and ramp upward after 6000 RPM to achieve a stable boost curve. Remember, we're looking for 22 psi tapering down slightly toward redline.

Once you have your boost almost exactly where you want it, add back a little error correction to the top half of the table. A correction of3% at -20 boost error should be fine. Taper down to 0 correction at -2.5 boost error. This will help flatten your load curve by keeping you within +/- 2.5% of your requested load. After adding back the correction for low load, you might see an overall increase of about 3 in your WGDC curve. It's nothing to worry about. It's because you're not at your desired load during spool up and the BCS is now trying to correct for it. It all balances out ... that's what this table is for.

Congratulations, you've set the boost levels on your Evo. You can work a little more on fine tuning these tables if you feel confident about it. One change I've made is to increase the BDEL values in the peak torque area to allow for slight overboost. This reduces the effects of the error correction table which can sometimes over-correct and cause a dip in your boost curve just after the boost peaks. You could also fine tune the boost limit values and the error correction to better suit your needs. Play around and have fun with it. Smilie thumbsup.gif

For richer or leaner

Woo Hoo! You've made your first logs, set your boost levels, and determined the load areas you'll be working with from now on. Good job. Now it's time move on to the fuel.

As (I hope) you know, internal combustion engines burn more than just gasoline. They burn a fuel mixture of gasoline and oxygen. The ratio of this mixture is very important to the performance of your Evo. The science behind this mixture in relation to horsepower is somewhat advanced, so I'll leave the explanation to the experts at Innovate Motorsports. Head over to their video page and watch the video named "LM-101 'Tuning Basics'" for a detailed look at why we tune for specific fuel ratios.

  • snore*

... Aaahhh! Oh, your done with the video. Cool. So, now you have a basic understanding of the stoichiometric ratio and why turbocharged engines run richer than naturally aspirated engines.

Okay, are you ready for the let down? As the video stated, we're aiming for an air to fuel ratio of 10% to 15% richer than stoich ... that would put our goal right around 12.6:1 (since we're tuning a boosted engine). Well, the thing is that number is completely unreasonable for a normal street car. Why? Because our fuel sucks. Plain and simple.

Here in the Southeast, we have 93 octane fuel, which I guess is better than those poor saps elsewhere in the country who have to deal with 91. But, even with our superior 93 octane fuel, that ideal 12.6:1 mix is overly optimistic. You see, the lower the octane rating of a fuel, the less stable it is under pressure and therefore more likely to burn in an unstable manner causing detonation or pre-ignition. As I explained earlier, this is bad.

So, we must lower the bar, accept defeat, and cry ourselves to sleep as we aim toward a more realistic mixture of around 11.0:1 to 11.5:1 while under boost.

Some things to consider

The fuel map isn't as straight forward as it might seem. There are a couple of small nuances that you should know about ...

The values in the fuel map are not actual AFR values. They do represent AFR and look like AFR values, but they are not a reference to the actual mix. Just remember that raising the value takes away fuel and lowering the value adds fuel.

Mitsubishi decided to do some funny thing with the fuel map that leans the actual mix within a certain range in comparison the the mapped value. This is commonly referred to as "lean spool." You might notice that there is a significant value shift on the fuel map between 2000 RPM and 2500 RPM ... that's where the lean spool effect begins. This affects your tuning by throwing off the values even in the fuel map even more and causing shifts in AFR between gears. Lean spool can be disabled, and there is a tutorial on EvoM that will show you how.

Here is a comparison of 2 fuel maps. The top map still has lean spool enabled and the lower one has no lean spool.


Also, there are 2 fuel maps. One labeled "High Octane" and one "Low Octane." The high octane map is the first map referenced and will be the map used if you are experiencing no knock. The low octane map is referenced if the motor sustains knock over a period of time. Your logging software should show an octane value that you are able to log. This value will let you know if you are using the high or low octane map. The octane value will drop when you hit more than 6 counts of knock. When this value drops, the ECU begins interpolating between the high and low octane maps for fuel and timing. How much interpolation actually occurs is speculation, but just know that it happens. So, if you see this value drop, your log will not be accurate. Locate the source of the knock, repair it and try again.

Setting a nice fuel curve

So, now we know what we are aiming for and we can begin tuning. You can start your fuel tuning based on your final boost log. Here is what you want to do:

From 3500 RPM to about 6000 RPM you want to aim for an AFR of about 11.2:1. This is a safe value for pump gas. With higher octane fuel you can go leaner.

Here is a trick for you ... remember that magical 12.6:1 AFR I mentioned earlier? There is a way we can make use of that optimum burn.At low RPM, while the turbo is still trying to spool, it is much less likely to knock. This is because without boost, our engines are just low compression 4-bangers. I've found that running this 12.6 (or so)AFR during spool up will actually help the turbo spool faster than the basic ramp down to 11.2:1. I've successfully run an AFR in the mid 12s up to 13 psi on the stock turbo with 0 knock. This helped the turbo reach full boost about 250 RPM sooner.

At the high end of the revs, it's a good idea to gradually richen the mix since knock is often seen at higher RPM. An AFR of 10.9:1 is a safe value at 7000+ RPM. Ramp down to this value starting around 6000 RPM.

Remember, while tuning, always monitor for knock and make small, gradual changes. If you see knock while tuning your AFR, pull timing or reduce boost if there is a spike.

You're looking for something similar to this ...


See, the process is getting a little easier now, huh?

Excuse me, do you have the timing?

You're half way there ... let's move on to setting the timing. Now, the "timing" I'm talking about here it the adjustment of the moment when the spark plug fires to ignite the fuel.

There are 3 high octane timing maps, and 3 low octane timing maps on your Evo IX. These high and low octane maps work the same as the fuel maps ... if knock is encountered for an extended period of time, some interpolation will occur. You want to focus on the high octane maps right now.

If you compare the 3 high octane maps, you'll notice that they are not the same. Map #2 is a little more aggressive with more advance across most of the map. As mentioned earlier, it's speculated that the #2 map is the main map used during normal operating conditions. I've personally found that interpolation occurs across (mainly) the #2 and #3 maps even when no knock is present.

So, the tactic I've found most useful is setting all of the high octane maps with the same values. This produces dependable results and makes your life a lot simpler. Don't worry ... if something goes wrong, you'll still have the low octane maps to keep the car safe.

Let's talk theory

There is a theory that many tuners use as a guide for tuning timing. It's referred to as "Minimum Timing for Best Torque" (MTBT).

Looking at tuning from the most basic sense, timing advance makes power. This is what some tuners will set the timing unusually high and let the ECU's built in safety features correct for it ... more on that later. However, it is believed that there is a point where advancing the timing does not produce extra power ... it simple makes the engine more prone to knock. So, according to the MTBT theory, the best way to set timing advance is to advance it until you don't gain any more power. Tuning this way gives you more room to make power other ways, such as more boost, a leaner fuel mix or cam advance.

The MTBT theory is based on an absolute fact that an engine will produce the most power when peak cylinder pressure occurs at 15* past top dead center (TDC). This is the point in the ignition stroke where the rod has the most leverage to turn the crank. Now, you might think that 15* is an absolute timing advance number that we are aiming for, but it's not. We can control when the spark fires, but that doesn't mean at that exact moment the cylinder pressure is at it's greatest ... it's an involved process. We must consider the gap and temperature of the plug, the time it takes for the burning fuel to reach its maximum potential and the speed at which the engine is spinning.

To use this method of tuning, you'll need some way to measure the power output of the motor. The obvious and most effective way is on a dynamometer. But, dyno time is expensive and tuning takes time. Some of us don't really have much of either. There are other solutions though ... you can use some pretty complex equations and create your own road dyno. This will allow you to measure your cars performance based only on the values you can log from your ECU. You do need to know some vital info though .. such as vehicle weight, drag coefficient, gear ratios, frontal area of the vehicle, ambient temps, etc. Many self tuners use Data Log Lab for this analysis. EvoScan also has a power/torque calculation feature built in to the graph viewer, but I've found it do be only marginally useful.

Note: When using a road dyno your results will not be as accurate as an actual dynamometer. Since the calculations are based mainly on RPM gain over time, the actual road surface you choose can skew the numbers produced. It is highly recommended that you only compare data recorded on the same stretch of flat road if you want reliable results.

Time to make some actual changes

Timing can be advanced (+) or retarded (-) in regard to TDC (0). Advanced timing means that the spark fires before TDC and retarded means ignition occurs after TDC. I know it seems backward, but trust me.

We are aiming for peak pressure at the magical 15* ATDC. Now, lets look at the individual components that affect this peak pressure and when it occurs:


The speed the engine is spinning. This one is simple. The faster the engine is spinning, the earlier the spark has to fire for the burn to keep up.


The A:F mix affects the length of the fuel burn in the cylinder. A leaner mix will burn faster, and will therefore require less advance to hit the 15* mark. The opposite is true for a richer mix. The added fuel will take longer to burn and will require more advance.

Also, the fuel octane should be considered here as well. The octane level doesn't really affect the timing needed, but more so the timing range available while avoiding knock. 87 octane fuel will burn exactly like 93, but you are less likely to reach your desired ignition point on 87 before you encounter pre-ignition.


The spark is probably the most crucial component in this array of variables. The heat range and gap of the plug play a very important role in the process. A "colder" (lower heat range) plug will slow the burn of the fuel and reduce the chance of knock by keeping cylinder temps and the temperature of the plug tip itself lower. This is important for us because cylinder pressures are generally higher in forced induction engines ... this increased pressure combined with excess heat is usually the cause of knock.

Note: The basic rule is that you need to go 1 heat range colder after adding 100hp to the car and close the gap by .004 every 50 hp. This means increased boost, an open filter and exhaust on an average Evo could call for a colder plug.

The material of which the spark plug's electrode is made should also be considered. Our cars come equipped with iridium plugs. Iridium is used as an electrode material because it does not corrode or melt in the cylinder like plugs of the past. This property creates a reliable spark over an extended period of time. Some people choose to run copper plugs for their increased conductivity. This is an advantage and is likely to give a slight increase in power. However, copper electrodes wear extremely fast in our cars and need to be changed every 5000 miles or earlier.

Basically, if you have some power mods on your Evo you want to run a colder plug (Stock IX = ILFR7H ... NGK only makes a colder plug in it's racing series, which is R7437-8). The plug gap should be on the high end of factory spec for best performance. Gap for the IX should be between .020 and .024. This kind of sucks because replacement plugs come at .044 or .032, which will likely cause misfire issues. Maybe the dealer sells the ILFR7H @ a .22 gap, but I've only seen them at .044. Either way, here is a list of plugs that will work.

The Evo IX comes with a colder plug than the VIII so basic mods on the IX don't require a plug change. The standard, colder replacement plugs for the VIII are the BR7ES (1/2 step colder) and BPR8ES (1 step colder).

For more info on plugs, check here.

(still adding ...)

[Missing Sections]

VVT ... no, it's nottransmitted sexually.

So... what now?