How To Tune an Evo

Old Oct 21, 2007, 09:25 AM
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How To Tune an Evo

Disclaimer: I have used the method outlined below successfully to tune my car. I am an amateur and not a professional. If you use this method then you accept full responsibility for whatever damage you do to your car. If you are concerned about voided warranty and damage to your car, you are better off leaving your car without any modifications to the ECU.

I am writing this essay because I often see a lot of request from Evo owners on how to begin tuning, what equipment is needed for accurate tuning, what approach should I take to tuning, etc….

Aside from the equipment and approach, the two most important elements to have are PASSION and TIME. If you want to learn how to tune an Evo simply to make money out of tuning, then IMO you will suck at it. Passion should come first and making money out of tuning is a distant second. If you do not enjoy tuning, then do not do it. You will end up very frustrated and maybe mess up your Evo.

The second important element to learning how to tune is TIME. You must read a lot and test a lot. The most important place to visit and read is the Ecuflash forum on Evom. This is the hub for Ecuflash tuning. I spend hours reading posts from knowledgeable people like MalibuJack, mrfred, razolab, tephra, jcsbanks, touring bubble, etc…. Some of the stuff that I read is highly technical to me. I get confused, so I read and re-read and read again. Sometimes I read threads three to four times before the concepts sink in. I get very frustrated at times since I do not have a technical background. Don’t be afraid to ask questions. The folks on that forum are very helpful. If you are polite and have done your reading prior to asking your question, then they will help you. Other places to visit include aktivematrix (MalibuJack’s website) and NorCal Evo.

When you first start reading you will be confused. The learning curve is steep and the task seems daunting. There is simply too much to read. Some of the posts are top notch and some are pure crap. You will have to figure out which posts to believe in. Use the above mentioned posters’ names as your guide. But do NOT give up, persevere. You CAN do it. It is NOT hard to tune your own Evo. It is not black magic or rocket science. Some pro-tuners want you to think it is, so you will not do it on your own. I was in your shoes once. I thought that tuning was some voodoo/rocket science affair. I too trusted a pro-tuner, only to discover that the pro-tuner I trusted had serious shortcomings. So I took a vow to learn how to do this and never to go to a pro-tuner again.

If you have PASSION and TIME, then the next step is to get the best possible equipment that you can afford. So what will you need?

1. Laptop: You must have a laptop. Modern tuning is all about computers. W/O a laptop, it is very hard to tune accurately with consistent repetitive results. There are many cheap used laptops on ebay. Make sure that you get one that is powerful enough for your tuning needs. I also recommend that you get a small laptop with a small screen. Mine is bulky and has a 14.xx inch screen. I am now in the market for a very small 7 inch mobile computer.

2. Logging hardware: You will need a logging/flashing hardware cable. The one that all of us currently use is the Tactrix Cable ( You can either get a universal cable or an Evo specific cable. The former will work on Evo and non-Evo vehicles, the latter will only work on Evos. I have one of each. One stays in my Evo and the other stays in my tuning kit.

3. Wideband O2 meter (WBO2): Do not attempt to tune your Evo if you do not have a WBO2 meter. Do not use the narrowband O2 sensor on the Evo to tune the car. The NBO2 was not intended for tuning purposes. It is used for emissions and it is only accurate under stoichometeric conditions and even then it is barely accurate. Tuning with a NBO2 was used back in the DSM days when WBO2 were very expensive and no one could afford them. Today, you can get a WBO2 meter for as little as $180. I use Innovate products. I have an LM-1/LM-A2 with two XD-1 gauges. One gauge reads AFR and the other gauge reads boost. The cost was $750. It was worth every penny. I have had zero problems with this kit.

4. Logging Software: The most widely used logging software is Evoscan ( It uses the tactrix cable to log data from your ECU port. It also allows you to integrate data from your WBO2 with the data from your ECU port. It costs $25. It is a one time fee that entitles you to later updates of the software. It is very user friendly and easy to set-up. If you want free software, then try Mitsulogger from the aktivematrix web site.

5. Tuning Software: The tuning software is known as Ecuflash. It is for free and you can download it from Be aware that some recent versions of the software have bugs in them and might not work on your lap top. I am still using version 1.29a because I do not want to deal with the possible bugs in later versions.

So now that you have all the equipment and tools, what do you do next?

First, you must install the WBO2 properly on your Evo. DO NOT install the WBO2 sensor behind the Catalytic Converter. That will give you erroneous AFR readings. The best position to place the sensor is in the down pipe 2 inches before the flange in the three o’clock position on the passenger side. Do not place the sensor in any position below three o’clock. You do not want condensation to form on the sensor and destroy the sensor.

Second, you have to go out and log data from your Evo. You must log, log, and log some more. Since I live in an urban area, flat freeway on ramp work great for me. Log in 3rd gear. Do WOT runs from 2500 rpm all the way to 7500 rpm. Only log the essential data with Evoscan. Logging all the data from your ECU will slow your logger down. The essentials include: AFR, timing, 2 byte load or loadcalc, TPS, RPM, Knock, boost (if possible), coolant temp, IAT, injector pulse width, and injector duty cycle. You must study and understand what the data means.

Third, download the rom image from your ECU using the tactrix cable and Ecuflash. Save the image to your lap top. Make sure the you write the immobilizer code in your rom on a piece of paper and save it. Understand what the tables in the rom mean. Do not touch them or modify them until you understand what they mean.

Fourth, now that you have read a whole ton and logged your Evo, you can proceed to modify the tables in your rom. The most important advice I could give you is to work INCREMENTALLY. Make small changes to the tables. For example, in the high octane fuel table lean out the map by making changes of no more than 0.3-0.4 target AFR. Do not go too aggressive in your changes. Another important piece of advice is to make the changes SMOOTH between cells. Recently, I saw a map that had the target AFR jump from 10.9, to 9.4 in two adjacent cells in the fuel map. This same map had a timing jump from 9* to 13* from 6500 to 7000 rpm. . The lack of smoothness in the map transition will more than likely trigger knock. A 4* jump from one load cell to the next will more than likely trigger knock on 91 octane gas.

So which part of the rom do I start tweaking first?

A. Timing

Generally, speaking Evos with a stock rom tend to have a lot of timing advance. Timing advance refers to the degrees that the spark plug is fired prior to the piston reaching Top Dead Center (BTDC). The higher the timing number in the load cell that the car hits during WOT operation, the further ahead of TDC that the spark plug is fired. This is known as advanced timing. The lower the timing number in the load cell during WOT, the closer to TDC that the spark plug is fired. In the timing map image below, I indicated the load cells that a tuned TBE Evo will hit during WOT operation in 3rd or 4th gear. If you look at load cells 220-260 @ 3500 rpm you will see 3, 3 and 2. These numbers tell us that the spark plug will fire between 3-2* BTDC. As the rpm increases so does the timing advance. Why? Well the engine has faster speeds and the spark plug must be fired earlier or else there would not be enough time to complete the burn of the air/fuel mixture. So in load cell 220/240 @ 7000 rpm the map indicates 10-9* BTDC. These cells are usually the cells that a tuned Evo 9 will hit during WOT operation in a 3rd or 4th gear log.

The Evo was designed by Mitsubishi to run on 93 octane gas, but in CA we not only have 91 octane gas, but our 91 octane gas is of very poor quality. Almost all of the stock rom evos that I have logged had 6-7 counts of knock in the 5500+ rpm region. My stock evo 9 had 6 counts of knock beginning @ 5000 rpm and continued with 4 counts of knock all the way to redline. This is a bone stock Evo 9.

So my first approach when tuning is to eliminate the knock. This means that you must retard the timing numbers (read fire the spark closer to TDC) in the high octane ignition map(s) especially in the higher rpms. An Evo 8 has one high octane ignition map while an Evo 9 has 3 high octane ignition maps. So why does the 9 have three? It is theorized that because of the mivec map on the Evo 9, Mitsubish introduced 3 maps. It is believed that the Evo 9 ECU interpolates between the three maps. Unfortunately, most tuners do not know how the interpolation works. It is believed that the Evo 9 ECU uses map #2 80-90% of the time and on occasion uses maps number 1 and number 3. Since our state of knowledge about interpolation is limited, most tuned maps that I have seen make the three high octane ignition maps the same. This gives you a consistent and repetitive timing curve. If you only tweak map number 2, then you might get inconsistent timing. I have seen WOT logs with timing increasing and then decreasing even w/o knock, rather than gradually increasing as the rpms increase. The usual culprit is that the DIY tuner forgot to make all three timing maps the same.

Here is the timing map that I use on a lot of Evo 9s. Of course, every Evo is different and you will have to tweak this map to fit your need. Keep in mind that this map is set-up with 21-22 psi peak boost (3500-3700 rpm) and the boost holding @ 20.5 psi in the midrange and then tapering to 19 psi by redline. The AFR for this timing is 12-13 during spool-up, 11.6-11.7 during peak and gradually tapering to 11 by redline. It goes without saying, that if you run less boost, and a richer AFR then you can run more timing.

I suggest that you save this map and compare it to the stock map on your rom to see where the changes were made. Generally speaking, I have found that Evo 9s like no more than 2-3* of timing advance @ peak boost/torque (3500-3700 rpm) and no more than 10-11* by redline provided you are running the boost that I mentioned above.

My approach to timing is to follow the MTBT method, i.e., Minimum Timing for Best Torque. Simply stated, the method declares that a tuner should advance timing until advancing the timing no longer yields gain in power/torque or, lacking a dyno, until knock is encountered. On the last Evo 9 that I tuned, 1* beyond 10* at the top end and the car started registering 2-3 counts of knock. So I backed the timing from 11* to 10* and stopped tweaking the timing map.

NB: The method outlined above to setting the timing ONLY applies to 91-93 octane gasoline. If you are using E85 advancing the timing until knock is encountered will yield poor or catastrophic results. You can go past MBT on E85 and not encounter knock. You might end up damaging your engine.

You will note that in this map, I have also advanced the timing from 5* to 7* in the 0-40 load and 0-1000 rpm cells. Why? Well, according to those in the know this will help smooth the idle even on a stock Evo, but it is usually used on cammed Evos. The load cells from 0-100 and 1500 to 7500 rpm are for cruising. Generally, they are left alone.

B. Mivec Tuning (Evo 9 only)

The Evo 9 has variable cam timing on the intake cam. It varies the cam timing from a value of 0 to a value of 30 in the VVT table. You can input values beyond 30 in the table but nothing really happens. Those who specialize in ECU disassembly on the Evo have not figured out a way to log cam timing. I am pretty sure that in due time they will figure it out. When that happens we can figure out exactly what load cells we are hitting across the rpm range and create far better maps. In the meantime a lot of DIYers have experimented with cam timing and posted their maps and their findings (

All the maps tend to follow a similar pattern: cam timing advance is low in the lower rpm, but as the engine speed increases cam timing is advanced. Cam timing advance reaches its peak around 3500-4000 rpm and then cam timing is gradually brought back close to zero by 6500-7000 rpm.

Most DIY tuners start by using the Evo 9 JDM RS map. That map forms the basis of 90% of Mivec maps that are posted and used in the VVT table. Here is what the map looks like:

Most DIYers change the numbers in the “island” that has 24 in it to 28.8 and save the map and flash it into the ECU. Others change the entire 28.8 numbers to 30, save the map and flash it into their ECU. This is a really good map.

I tinkered with mivec and was able to come up with a map that I really liked. It is a fusion of two maps. The first map was posted in the Mivec Tuning thread on Evom and the second map was created by John Bradley who is the resident mivec guru on Evom. I took the top end (load cell 70 to 100) from one map and fused it with the bottom end from another map. I was very surprised by the increase in low end snappiness of my Evo. The car felt like an NA car. You can put it in high gear at low rpm and simply touch the accelerator and the car goes. I thought it was only in my mind, but when I tested it on other Evos, the impressions of the drivers were the same. Two caveats about this map: First, it will slightly increase your idle by about 100-200 rpm during normal driving. Second, after you hammer on the car for a while, your idle will go up to 1000 rpm. If you can tolerate this, then go ahead and use the map. If you cannot, then use the JDM 9 RS map.

C. Setting the Boost

The majority of Evo owners use an MBC to control boost. So this is what I will use in this write-up. The more recent use of ECU boost control is very well covered in this forum. one of the The most widely used MBCs is the Dejon Tool (DT). It is simple to use, cheap, and effective. Turn the knob counterclockwise and the boost decreases. Turn the knob clockwise and the boost increases. Be very careful though, the DT is very sensitive to even the smallest of adjustments. So make your adjustments about 1/8 of a turn whenever you are increasing the boost.

So I installed my MBC, how do I set my boost?

Please refrain from using the “eyeball-the-gauge” method to set your boost. Mechanical boost gauges are inaccurate to begin with. I had a Defi D boost gauge that I thought was very accurate. When I logged the boost, the Def D was 1-1.5 psi off. I have logged several Evos that have had their boost set using the “eyeball-the-gauge” method and the result of the log is different than from what the Evo owner told me the boost was set to.

Logging the boost requires installing a MAP sensor and calibrating it properly based on atmospheric conditions in your area. A MAP sensor is usually tapped into the little hose that connects from the intake manifold to the FPR. That is the way it reads pressure. The pressure pulses are translated in the sensor into 0-5 volts signals and sent to a data logger. The data logger takes the signals and based on the calibration data that you supplied translates the voltage into psi.

I use two methods to log boost. The first uses the GM 3 Bar MAP sensor. This sensor is widely available and very easy to set up and use. I bought mine with a pig tail harness for $75. I set it up using the calibration data that was provided by the manufacturer. The calibration data that I enter in my logger (Logworks logs the LM-1/LMA2) is as follows:


The second method to log boost is to use a JDMMAP sensor specifically designed for the Evo. In Japan, the Evo is equipped with a 3 bar MAP sensor that sits atop of the intake manifold. The USDM Evo gets a worthless 1 bar MAP sensor. An enterprising genius on Evom by the name of mrfred figured out how to use the JDMMAP sensor on the USDM Evo. The process involves swapping the sensors and modifying defined tables in the ECU to log the values from the JDMMAP sensor. The same principle that I outlined above applies to the JDMMAP sensor only now you can log the boost directly from the ECU provided you have properly modified your Evoscan xml file to log boost. The whole process is outlined here

So what does the boost look like on a stock Evo 9? A bone stock evo 9 should have the following boost profile:

First, the average boost number @ peak is close to the 20.3 psi. 20.3 psi is the spec sheet boost for the Evo 9. Environmental conditions will make the boost vary. I have noticed that logging on a day with high humidity will bring the boost down a bit. Second, the boost tapers like crazy on the Evo 9. By 6500 rpm the boost is below 16 psi. It is a pity that I do not have stock boost logs from my old Evo 8 to compare to my Evo 9.

The above boost chart is what the boost looked like on my Evo 9 after installing a TBE with a HFC. You will note that the boost climbed to an average of 20-21 psi at peak and the boost stayed above 16 psi by redline. Also of note is how the load has climbed from 200 to 220. Generally speaking, the more power the Evo makes the higher the load cells that it will hit.

This is what your boost should look like on 91 octane gas. Your target average boost should be between 21-22 psi for an Evo 9 and less than that for an Evo 8. You will note that the Evo is now hitting higher load cells and can hold higher boost to redline. Unfortunately, if you want your boost to be higher by redline, then your boost will climb higher by 3500+ rpm. On 91 octane, this can become dangerous.

What about the boost limit, aka, boost cut?

The picture above shows the boost limit table and the boost delay table on a stock Evo 9. What does it mean? If your Evo hits a load higher than 255 (approximately 22 psi) for 1 second, then the boost cut will kick in. The higher the rpm goes, the lower the limit. So at 7000 rpm if your EVO hits loads of more than 235 for 1 seocnd, then the boost cut will kick in. This is an excellent safety feature that Mitsubishi engineered into the ECU.

Last edited by nj1266; Sep 9, 2009 at 01:47 PM.
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Old Oct 21, 2007, 09:26 AM
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Continued from the first post....

Under no circumstances should you eliminate this safety feature on 91 octane pump gas. When it comes to boost limit, just set the limit slightly higher and please leave the boost delay alone. Setting the boost limit @ 300 or maxing it out to 319 simply removes the safety from your ECU in case of an overboost condition. Here is the way I set the boost limit on an Evo running on 91 octane gas:

The boost limit is increased by 10 load points from 3000 to 3500 rpm, 5 load points @ 4000 rpm, left stock between 4500 and 5500 rpm, increased by 5 load points between 6000-6500 rpm, and left stock at 7000 rpm. After 200+ WOT logs in 3rd and 4th gear I have yet to hit the boost limit.

So how did I come up with these load numbers? Is it guesswork? No, it is not. I came up with these numbers by logging the 2 byte load from the ECU. Here is what the log told me about the load (which is close to boost) is on my car:

Notice how the maximum load numbers of these 3rd and 4th gear logs is close to the set boost limit on my car. For example, the 263.8 In the log @ 3500 rpm is very close to the 265 @ 3500 rpm in the boost limit table. Now you can choose to increase them slightly, but I would not go over 270 load on 91 octane gas @ peak boost.

D. Tuning the Air Fuel Ratio (AFR)

AFR refers to how many parts of air are mixed with how many parts of fuel. So an 11:1 AFR means that 11 parts of air are being mixed with 1 part of fuel to create the air/fuel mixture. When your Evo is at idle or when your Evo is at cruising speeds your AFR is around 14.5-14.7:1. This is known as stoichometric or stoich for short. It has been found that the 14.7:1 mixture produces the least amount of emissions. And since cars spend 90% of their time at idle/cruise then that is the number that the manufacturers use to reduce the emissions on their car. It is worth noting that the 14.7:1 AFR does not produce the best gas mileage. The best gas mileage is produced are 15.2:1 AFR.

What AFR produces the best power for gasoline? Gasoline gives the best power when it burns at an AFR of 12.5:1. This is regardless of whether the car is normally aspirated, turbocharged, or supercharged. Some modern turbocharged engines with direct fuel injection can run that lean during WOT operation. The turbocharged Ecotec in the Solstice GXP is such an engine. That engine can boost up to 18 psi, yet it runs at 14:1 AFR at 3500 rpm and tapers down the AFR to 12.5:1 by redline.

So can I run my Evo at 12.5:1 AFR? NO you cannot and should not. The Evo’s engine is about 17 years old, it does not have direct fuel injection, and the combustion chamber is not designed to handle such a lean AFR. Furthermore, the car is running on 91 octane gas. Under high boost and lean conditions, 91 octane gasoline becomes very unstable and can self ignite causing knock and other assorted problems.

So why tune the AFR last? There are two main reasons. First, changing the mivec map has an impact on the AFR. If you tune the AFR before mivec and then you tune mivec, the AFR will change and you will have to do it again. My testing indicates that adding the JDM RS mivec map to an already tuned AFR will make the AFR leaner by about 0.25 points. Not a lot, but something to take into account when you tune.

Second, increasing the boost will also impact your AFR. Why? The higher the boost the higher the load cell that the car will hit in the fuel map. Mitsubishi designed the fuel map to become richer the higher the load cells. So when you up the boost you will hit those higher load cells and the car will run richer. If you tuned your AFR before your boost, then you will have to do it again after you increase the boost. Why do things twice?

Below is an Evo 9 fuel map. I have interposed on it green dots (stock Evo), black dots (Evo with TBE), and red dots (Evo with TBE and boost set @ 22 psi and tapering to 19.xx by redline). You will note that a stock Evo hits lower load cells (200 to 180) than a TBE Evo (220 to 200) and a TBE Evo hits lower load cells than a TBE Evo with boost increase (260 to 230). You will also note that the numbers in the load cells decrease as the load cell increase, i.e., the car becomes richer. It is very important to note that the numbers in the load cells of the fuel map are NOT actual AFR numbers that you will log with a WBO2. Under no condition should you enter the AFR that you logged with your wideband into the fuel map. They are just numbers. The higher the number, the leaner the AFR, and the lower the number the richer the AFR.

So what does the AFR look like on a completely stock Evo? It looks horrible. The Evo runs very rich from the factory. It is tuned very poorly. The AFR falls below 11:1 at 3500 rpm and continues to get richer until it hits 9.5:1 by 7000 rpm. Despite the overly rich AFR, a stock Evo still knocks due to the overly aggressive timing.

Setting your AFR depends to a large extent on the boost and timing that your car is running. When running the boost and timing mentioned in this essay, I generally set the AFR at 12.5-12 during spool up, 11.7-11.5 during peak boost, and then slowly taper the AFR until it hits 11-10.9:1 by redline/cutoff.

So how do I go about editing the fuel map?

Well, first you have to log your AFR. Below is a chart with three back-to-back logs from my Evo 9 with a TBE and K&N drop-in. The map is stock with the exception of extending lean spool from stock (7000 rpm) to 7700 rpm. I will explain the lean spool trick later on in the essay. The boost is also untouched.

First, notice how the AFR became leaner by simply adding a TBE and a drop-in filter. At 3500 rpm, for example, the AFR became leaner by 0.77 points, exactly where we want it to be. Second, the actual AFR is very close to our target AFR right up to 5000 rpm. Beyond that the AFR goes rich again. This will require adjusting the fuel map.

The formula to adjusting the fuel map is very simple. Let us look at the 5500 rpm row and load cell 220 in the log chart above. The Actual AFR (AAFR) is 11.13:1. The fuel map AFR (MAFR) shows a 9.7 number in the 5500 rpm and 220 load cell. Let us assume that we want a desired AFR (DAFR) of 11.4:1 in that load cell. What should the new map AFR (NMAFR) be?


NMAFR=11.4 X 9.7 / 11.13 = 9.9353

So the number that you should enter in the fuel map in the 220 load cell @ 5500 rpm should be 9.9.

To make this easy on yourself, simply create a template in excel with the above formula and use it over and over again. This way you will not have to do any manual calculation. Just plug in the numbers and excel will take care of it. That is what I did and it works like a charm. This method takes the guessing out of AFR tuning and allows you create a very flat and consistent AFR. Below is a 4th gear log with the AFR indicated @ spool up, peak boost and 7000 rpm. It is nice and flat from 3800 rpm to redline. The data is not smoothed. Logworks and Evoscan do not smooth the data. Logworks allows you to smooth the data afterwards. I like the data raw.

E. Reading your knock sensor

An ideal combustion process behaves in the following manner:

1. The air fuel mixture is brought into the combustion chamber. Ideally this mixture should have around 12.5:1 AFR to extract maximum power from gasoline. Given that the Evo engine is about 17 years old, crappy CA gas, and high boost, this ideal is pretty hard to achieve w/o running water or methanol injection. As stated before most amateur tuners that I know run between 11.5-11:1 AFR on an Evo.

2. The intake and exhaust valves close and the spark plug fires. On an Evo 8 a spark plug fires at around 18-21* BTDC by 7000 rpm. On an Evo 9 there is less timing advance with the spark plug firing around 14-16* BTDC by 7000 rpm. Why less timing advance on the Evo 9 than the Evo 8? In part, it is because the Evo 9 is blessed with a better cooled and better flowing cylinder head than the Evo 8. The Evo 9 can run leaner AFRs. Leaner AFRs burn faster up to 12.5:1. Beyond that they burn slower. A faster burning mixture does not require as much timing advance as a slower burning one. I am not saying that the Evo 9 has a leaner AFR from the factory. Far from it. What I am saying that it has the potential to run leaner AFRs and consequently less timing advance.

3. After the spark is fired the burning of the mixture proceeds. It begins at the spark plug and progresses in an orderly fashion across the combustion chamber. It is as if you took a pebble and threw it in a pond and watched the ripples progress outward from where the pebble fell. The burn should be complete with no remaining air-fuel mixture by the end of the combustion process.

In reality combustion sometimes does not progress in an orderly and smooth fashion. Sometimes the air-fuel mixture spontaneously combusts after the spark plug is fired but before the flame front reaches the mixture. This is commonly known as detonation or more commonly knock. Why does that happen? Too much pressure and too much heat combined with the lack of enough octane in the mixture to resist self-combustion. Think of octane as the ability of gasoline to resist self-combustion under pressure and heat. The higher the octane the less likely the gasoline will self-combust under high boost and heat that the Evo is known to generate.

Unfortunately in CA, we are stuck with very poor quality 91 octane gasoline, yet the Evo has a very old combustion chamber design and very high boost. That is a perfect recipe for detonation when you factor in the advanced timing that the car runs from the factory.

When a car knocks, it causes a very sharp pressure spike that is outside the normal shape of a pressure curve during normal combustion. The pressure spike creates a force in the combustion chamber. The structure of the engine pings/rings in reaction to the force generated from the pressure spike. That is where the knock sensor steps in.

The knock sensor is usually connected to the back of the engine block. It is nothing more than a microphone. It reads the noise in Hertz and transmits it to the Evo ECU. The Evo ECU filters that noise using 12 different tables in the rom and decides if the noise is knock. If it is, the ECU sends a signal to the sensors to pull the timing in order to save the engine from further detonation and possibly damage. The knock sensing system is reactive and not pro-active. The timing pull happens after knock is detected and pulls timing to prevent further damage. It does not prevent knock, it tries to limit it after it has happened.

The signal that the ECU spits out is commonly known as “knock sum.” The loggers that we use have the ability to log knock sum. Generally speaking the higher the knock sum the more timing will get pulled, the lower the knock sum the less timing will get pulled. More on that later.

So what sort of damage does knock cause?

If left unchecked, knock can break the spark plugs, the valves, and the rings around the pistons. Second, knock can be very abrasive to the crown of the piston. Pistons on an engine that is suffering from excessive knock will look like as if it has been sandblasted with small pits in the top of the piston. Finally, excessive knock will cause a premature failure of your rod bearings resulting in the very distinctive rod knock sound.

Having said the above about the dangers of knock do not be surprised to know that almost all cars knock. As long as the knock is occasional and moderate cars can run for thousands of miles with little to no problems. While detonation is not an optimum situation for engine operation, it does not guarantee engine failure.

So how should I deal with knock?

As I briefly mentioned earlier the Evo ECU spits out a parameter known a “Knock Sum.” That parameter is one of the most important to log when tuning your Evo. Evoscan tells us that this parameter can vary from 0 to 50 with 50 as the maximum knock count that the Evo ECU can register.

When tuning your Evo it is advisable to tune timing, fuel, and boost w/o triggering more than 1-2 occasional counts of knock, three at the most. We know for a fact that 3 knock counts pull 1* of timing. I have also logged occasions when 1 knock count pulls 1* of timing.

I tune for 1 to 2 occasional and sporadic counts of knock, three at most. Anything above that is unacceptable. Here is my take on knock:

1. All cars knock on occasion. I have logged an Evo that knocked the first log and then gave me three knock free WOT runs. Generally speaking, the first WOT log that you do tends to be knock prone. You have to do at least three back-to-back logs to make sure that knock is consistent. I do not worry about an occasional log that has knock it. If the knock is transient and does not repeat, I usually ignore it.

2. Knock is a problem when it is consistent and repetitive, i.e., it happens every log and at the same point in the rpm range. That is the kind of knock to worry about and work hard to eliminate.

So my Evo has more than 2 counts of knock and the knock is consistent and repetitive. What should I do to eliminate it?

IMO, the biggest cause of knock on an Evo is too much timing advance. Let us take a look at my stock Evo 9 with no tuning. My Evo 9 consistently and repetitively registered 5-6 counts of knock from 5000 rpm on. Below is a chart of a typical 3rd gear WOT run on my Evo 9.

Notice that the timing @ 5224 rpm was 10* and after 6 counts of knock the timing was pulled to 8* by 5500 rpm. 6 counts of knock pulled 2* of timing, in line with our assumption that 3 counts of knock pull 1* of timing.

So what is the ECU telling us to do to combat knock?

We know from MTBT (minimum timing best torque) theory that we should advance the timing until we either stop making power or we see the onset of knock. In this case we clearly see the onset of knock. So what we have to do is pull 2-3* of timing to combat the knock in that rpm range.

Here is the way the log looked after I pulled timing. The boost was almost unchanged and the AFR was slightly leaner in that rpm range. Pulling the timing from 10* to 7* @ 5200 rpm cured the knock in this instance.

Here is another example. The chart below is for an Evo 8 with the following modifications: TBE, O2 housing, 264 cams, Walbro fuel pump, 720 injectors, and Greddy EBC and a tune.

As you can see the car was knocking. The data labels show that it had: 3 counts of knock @ 5000 rpm that pulled 1* of timing, 5 counts of knock @ 5400 rpm that pulled 2* of timing, and 12 counts of knock @ 6250 rpm that pulled 4* of timing. These numbers are very closely in line with the fact that 3 counts of knock pull 1* of timing. By 7500 rpm the timing was @ 13* despite the fact that the timing in the rom map was much higher than that.

So what is the ECU telling us in this instance?

The ECU is telling us not to set timing more than 13* by 7500 rpm. We can basically set the timing at 13* by 7500 rpm and work our way backwards. With this in mind, I set the timing at 2-3* at peak boost and slowly incremented it upwards until the car hit 13* by 7500 rpm. Here is the way the log looked after the timing was changed:

As you can see, the serious knock in the car is gone. What remains are 1-2 counts of knock here and there. You will note that 1 count of knock still pulls 1* of timing as can be seen @ 7000 rpm, but most of time it is the 3 counts of knock that you will have to worry about. On this Evo, any timing increase beyond 13* triggered knock. So I left the timing at 13* at the top end.

And here is the final example.

This one is very interesting because the tuner wanted to force this Evo 9 to run advanced timing and was willing to run the car extremely rich to do it. At peak boost the target AFR was set to 7.4 and the knock prone segment of the power band had a target AFR of 8.5. The AFR curve on this car was only a smidgen better than the AFR on a stock Evo 9. But no matter how rich he ran the car, this Evo still knocked because of the advanced timing. The timing profile was block tuned with 5* from 1500-3500 rpm, 6* from 4000-5000 rpm, 7* @ 5500 rpm, 8* @ 6000 rpm, 11 @ 6500 rpm, 14* @ 7000 rpm and 16* @ 7500 rpm. Take a look at the chart below:

Notice how the Evo’s ECU pulled 3* of timing when it registered 8 counts of knock. Even though the tuner ran the car at 10.3:1 in order to make it accept 11* of timing, the car still knocked and ended up with 8* of timing @ 6500 rpm. So why not run 8* of timing to begin with and run the car safer with a decent AFR? If the ECU is going to pull the timing anyway, then why insist on advancing the timing so much and run the car as rich as stock to boot?

Here is a log form the car after the timing was retarded and the AFR leaned to reasonable levels:

The AFR is 11.13:1 in the knock prone area and the timing was set at 8* which is exactly what the ECU told me that this Evo wanted. The car is running leaner, cleaner and safer. It is also putting just as much power as before.

The above three examples show you why reading the knock sensor when setting the timing is essential. By reading the knock sensor the tuner is able to give the Evo the timing that it wanted rather than the timing that he assumed it wanted.

F. Injector Scaling

The stock injectors on the Evo are rated at 560. Generally speaking, the stock injectors will give you adequate fuel flow with a TBE, an intake, and 19-20 lbs of boost by redline. Once you get cams, then it is advisable to get bigger injectors. If you get a bigger turbo, then definitely get bigger injectors.

If you install bigger injectors, then you will have to scale them properly and use the correct injector voltage latency, otherwise your car will idle poorly and stall on occasion.

So how do you go about scaling your new injectors?

Scaling injectors is a PITA. It involves a lot of trial an error. It is not enough to simply put numbers in the rom tables and simply declare the injectors scaled. You must test and make sure that the scaling is accurate.

Here are the steps I follow when scaling injectors

1. Open Ecuflash and open your rom. Under fuel locate the Injector Scaling table and the Injector Battery Voltage Latency table. On a stock Evo they look like this:

The table on the left refers to the injector value that the ECU is using when making its fuel supply calculations. The number in the table is always smaller than the actual size of the injectors on the engine. For example, the stock injector size is 560, but the number in the table is 513. As a general rule of thumb, enter a number in the table that is 15-20% less than the size of the injectors installed on your Evo.

Continued below.....

Last edited by nj1266; Sep 9, 2009 at 01:48 PM.
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Old Oct 21, 2007, 09:28 AM
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For example, let us say that you are using 680 size injectors. Then you enter in the injector scaling table a number between 578 and 544. Please note that this is only the starting point and not the end point of injector scaling. The final number will be determined through multiple sessions of logging and testing your fuel trims. More on this later.

The table to the right is the injector battery voltage latency table, aka, dead time table. The numbers in the right column are in milliseconds. The numbers refer to the amount of time that the injectors take to open completely and produce maximum flow. The numbers in the left column are in volts. As battery voltage decreases, the time between the injector receiving the signal to open and when it actually opens increases. Therefore, you must send the signal sooner to have the injector open at the appropriate time. The larger the injectors, the more time is needed for them to open. So you will have to increase the numbers in the millisecond column to compensate for larger injectors. The trick is to find the accurate numbers.

This is where the AEM EMS comes in handy. The EMS has an injector latency wizard that lists the latency for a lot of injectors. Here is the link to the excel table from the wizard.

Open the file and copy the numbers from it into the injector voltage latency table. For example, if your running 680 injectors, then your latency table would look like this:

Please note that the excel file does not include latency numbers for the 4.69 volts slot. What I did for this car is simply use the increment function in Ecuflash and increase the millisecond number once. That seems to do the trick. If anyone has a better way to determining the number to use in the millisecond column for the 4.69 volt slot, then please e-mail me.

So I have set the injector scaling on my 680 injectors as follows:

Am I done now? Hell no. Now comes the hard part.

You need to make sure that the numbers that you have entered are working properly. To do that you MUST log your fuel trims for an extended period of time. The trims to log are:

LTFT Low = Long Term Fuel Trim Low
LTFT Mid = Long Term Fuel Trim Mid.

Both of these trims fluctuate between +/- 12.5%. The LTFT Low is for idle and the LTFT Mid is for cruising. Your aim is to keep both trim to +/- 5% or less. If the fuel trims are too positive, then the ECU will add fuel and this will royally make your AFR too rich. If your fuel trims are too negative, then the ECU will remove fuel and this will make your AFR too lean.

How do I log my fuel trims?

Logging fuel trims takes a lot of time and you will waste a lot of gas to get your fuel trims as close to 0 as possible.

Let us start with the LTFT Mid. You must drive the car at a steady speed for at least 16 minutes. Why? The fuel trims cycle approximately every 4 minutes. You will need to have them cycle multiple times until they settle on a number in your log. 16 minutes will alow your trims to cycle 4 times. That will give them ample time to settle.

Let us take my example above. We had the scaling at 552 for the 680 injectors. And we cruised at a steady speed of 60 mph for 16 minutes. We found out that the trims went way negative and hit -10%. So we pulled over and incremented the injector scaling twice. The scaling went up from 552 to 572. We flashed the new numbers into the ECU. Then we went logging again for another 16 minutes.

We found out that the trims are still going negative but not as much as before. This time our trims hit -8%. We now know that we are on the right track. But we are nowhere near the +/-5% that we would like to hit. So we pulled over on the side of the freeway again. Incremented the injector scaling in the rom twice. This moved it from 572 to 597. We flashed the new scaling into the ECU and went for another 16 minute log.

The numbers in the log were very close to 0. The LTFT Mid registered around -3. We are almost there. So we pulled over on the side of the freeway and incremented the injector scaling one last time. The new scaling was 609. We flashed the scaling into the ECU and went for yet another 16 minute log. The logs showed a final fuel trim of -1.86. We have dialed the LTFT Mid to as close to zero as possible.

The next step was to log the LTFT Low. This is done by logging the car for 16 minutes at idle. We did that several times and found out that the LTFT Low stayed at the -1.66 level. This is a similar number to the one we achieved with the LTFT Mid trims.

We have finally dialed our fuel trims. Are we done done now? Not yet.

Now you MUST go back and adjust your AFR fuel map to fit the new injector scaling. You are basically going to have to re-tune your fuel map to fit the new injectors. Just follow the section about AFR adjustment in this write-up.

The whole process is very time and gas consuming and it can get very frustrating. But with time and patience, it can be done

To Be Continued....

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Old Oct 21, 2007, 09:35 AM
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Nice work nj1266. This will be a great resource for beginners to come and get a good idea of how to start.

Let's just hope they read it and take the advice
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Old Oct 21, 2007, 09:39 AM
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very informative, will be a great read for future noobs to tuning. Must have taken you a long time to write all this!
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Old Oct 21, 2007, 09:45 AM
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Very well done great to see people taking the time to share their knowledge and experience, and TBH I learned a lot myself, this has to be made a sticky, this is really top class information,

Last edited by BarryC; Oct 22, 2007 at 12:35 PM.
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Old Oct 21, 2007, 09:52 AM
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Nice job! Ill leave the tuning to the professionals, haha, looks wayyy to complicated.
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Old Oct 21, 2007, 10:28 AM
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nice! just what I was looking for
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Old Oct 21, 2007, 11:25 AM
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Excellent - thanks for sharing this!
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Old Oct 21, 2007, 11:41 AM
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Originally Posted by YtDiamond05 View Post
Nice job! Ill leave the tuning to the professionals, haha, looks wayyy to complicated.
Nah, it just takes patience and baby steps. The first step is to buy the gear he listed above. Once you can download your own ROM file from your ECU and "see" your current tune, you start to get hooked. THEN, you start logging with evoscan....and now you're pulled right in.

Don't try to "tune" from the beginning, simply learn to download your ROM from your ecu and learn to datalog a few pulls. Once you've learned all that will be asking how to do more.

P.S. Nice job nj1266!

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Old Oct 21, 2007, 11:54 AM
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yep, very informative for beginners.... maybe this will save some of us the emails we get asking this information. JB's mivec map FTW
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Old Oct 21, 2007, 12:01 PM
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This is by far the best how-to write up to date the only thing that i need to know is how the load, rpm traces through the fuel, timing map. Which load do i use load cal or the other load on evoscan?
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Old Oct 21, 2007, 12:04 PM
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you should be using 2 byte.... there is a thread on how to set it up
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Old Oct 21, 2007, 12:04 PM
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Excellent info nj, I am subscribed!!!
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Old Oct 21, 2007, 12:11 PM
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Great writeup NJ but you might check that RS Mivec MAP, according to JB in this post the one you have posted is another tuners Mivec MAP..
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