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Old 08-20-2003, 08:37 PM   #1
Jon [in CT]
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Default Vishnu ECUTEK - SCC's Point of View

Project WRX: Part VI
Engine management without wires

By Josh Jacquot
Photography: Josh Jacquot

With Project WRX cranking out 240 hp at the wheels, while wearing a highly adjustable DMS suspension, huge brakes, sticky tires and 17-inch wheels, we feel like we're approaching the end of a good run with an old friend.

However, being the neurotic car-modifying freaks we are, we can almost always find reasons to fix what's not broken. That's what we're doing this month. The last time we dealt with ECU changes on Project WRX, we installed the Xede piggyback computer from Vishnu Tuning to control engine parameters vital to the hardware mods we made. This month, we may have found an even more elegant solution.

Vishnu now has an alternative for those who are less interested in tuning the car themselves. This alternative, known as ECUTEK, is actually a piece of software which allows Vishnu to "reflash" the stock WRX ECU using a laptop computer through the OBD-II diagnostic port. ECUTEK software allows control over every detail of Subaru's highly advanced engine management. The elegance of the system is multifaceted for the consumer.

ECUTEK is a smart solution for those who want big power as much because of what it doesn't do as what it does. Small nuances of engine calibration such as cold start, load compensation, hot restart and other difficult-to-tune or condition-dependent problems are virtually eliminated since Subaru has already done the job right from the factory. Vishnu tunes only the maps required for more power as determined by the many different upgrades customer's cars might have. In other words, every reflash is essentially a custom tune specific to that car's mods and the fuel used. Since Project WRX is fitted with Vishnu Stage 2 mods, tuning began from the Stage 2 baseline map for California's 91-octane pump gas. However, Vishnu has on file a sample pool of maps from cars with varying levels of modification and different octane (including 93- and 94-octane East Coast fuel), which streamlines the tuning process and allows ECUTEK software a huge range of application from mild, near-stock cars to 400-hp monsters. Project WRX is somewhere in between.

The tuning process begins with four or five dyno pulls on Vishnu's Dyno Dynamics chassis dyno to get the engine up to temperature and witness the adaptability of the stock ECU based on the car's mods. Once the range of adaptability has been verified, changes begin in the knock correction table to bring the engine as close to the knock threshold as possible. The base ignition map is fairly conservative, as Subaru's engine management is very adaptive and will advance ignition timing on its own. Therefore, most tuning changes are made to cells in the knock correction table. Power is maximized by manipulating the cells that tell the ECU how far it is allowed to advance ignition timing without reaching the knock threshold. This means the knock correction values are sometimes as high as 11 degrees advanced beyond base map values. According to Shiv Pathak, the owner of Vishnu Tuning, Subaru engines must operate as close to the knock threshold as possible to make maximum power. Therefore, allowing the ECU to determine the ignition timing is the best way to tune the engine. This results in a smooth power curve with immediate adaptability to heak soak, sustained thermal load or octane fluctuations.

Subaru's stock boost control is also highly advanced, relying on many sensor inputs to determine safe, yet effective, levels of boost. Unlike many aftermarket boost controls which are MAP based, Subaru's stock management determines boost based on engine speed, vehicle speed (which affects intercooler efficiency), altitude and temperature. MAP-based controllers can overspeed undersized turbos at high elevation, shortening their life. Multi-parameter based boost control is simply safer.

There are other benefits, as well. Subaru's stock ECU has several safety nets built in. Unlike many stand-alone systems that are only reactive, the stock Subaru ECU constantly observes average knock correction and can apply a global retard by switching fuel maps if average knock correction value reaches a preset limit (see the fuel tables screen capture ). In other words, if the ECU sees crappy gas, it will switch to a crappy gas map automatically. This adds an additional margin of safety for highly stressed engines against bad fuel or other problems.

Once tuned, Project WRX made 240 hp and 205 lb-ft of torque on the ECUTEK reflash--comparable to the 239 hp and 216 lb-ft it made running on the Xede piggyback. The reflash is also marginally less expensive at $750 vs. the Xede's $795. The primary difference between the two is tunability, although any results produced with the Xede can be duplicated through the ECUTEK software, if that's the goal. ECUTEK is essentially for enthusiasts who don't need the ability to do their own tuning. Xede offers most of the benefits of a full stand-alone system for those who do.

Delta Dash
Since we installed the ECUTEK on our car, Vishnu has begun selling a software bundle called Delta Dash, which allows reflash users limited access to boost, ignition and fuel and other maps. This software isn't designed for complete tuning, rather it's an enthusiast-friendly interface to select parameters. Delta Dash doesn't allow access to individual cells in each map. Instead, only global changes can be made to base fuel, ignition and boost maps.

More importantly, Delta Dash can be used in race or valet applications to change boost maps on the fly by pressing the throttle to its wide-open position and pushing the defroster button at the same time. This feature could also be activated as a safety margin by hot-climate users on 100-plus-degree days to alternate between low and high boost--especially those of us in California who must run on 91-octane fuel. Delta Dash uses the parallel port on a laptop computer for connection to the OBD-II port in the car. All changes are made in real time. It costs $325.

ILLUSTRATIONS



Boost parameters
The WRX's stock boost control is a function of engine speed, vehicle speed, altitude and temperature. This screen shows the tuner the desired boost (top table) and the wastegate duty cycle percentage (bottom table) as functions of load and engine speed. Boost control this advanced means there's less chance of overspeeding the WRX's stock turbo at high altitude and provides an extra margin of safety over MAP-based systems.



Complete parameter list
Here you can see all functions that ECUTEK tuners are able to manipulate. Tuning for maximum power realistically only involves a few parameters, but ECUTEK allows access to nearly every function of the WRX's stock ECU.



Low/high-detonation fuel maps
One of the best safety features of the WRX's stock engine management is its ability to switch to a different fuel map to account for bad fuel or other problems which could result in broken engine parts. During normal conditions, the WRX runs the "low-detonation" (top) fuel map. However, since it keeps tabs on average knock correction, it can switch to a more conservative "high-detonation" (bottom) fuel map. The switch-over point can be changed by the tuner. Since the stock management is constantly trying to advance the ignition to the knock threshold, it will eventually revert to the "low detonation" map.



Knock correction table
The magic of ECUTEK tuning happens in the knock correction table. In this table, cells are color coded as a function of knock activity in real time during a dyno pull. Blue equals more positive correction, lighter blue slightly less, then green, then pink, then red--at which point, there's virtually no positive correction beyond the base ignition map. This speeds the tuning process and ensures a wide safety margin in the final tune. The software also logs the maximum and minimum correction values. Values can also be viewed as a 3D graph over load and engine speed.



Tuning screen
Tuning with ECUTEK primarily takes place in one of three tables--the knock correction table (bottom), the fuel table (top) and the main ignition map (center).
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Old 08-20-2003, 10:13 PM   #2
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Three corrections to the layout and info above:

1. Serial port, not parallel port for DD (although I believe there is a parallel port option...)

2. The caption below the LoDet and HiDet maps references them incorrectly. You can see in the title bar of the windows that the HiDet map is on top, not bottom.

3. Xede is $795 with no tuning features, $895 with tuning.
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Old 08-20-2003, 10:19 PM   #3
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Oh, and thanks Jon. That was a lot of effort instead of providing a link to the article over at sportcompactcarweb.com (not sure why you bothered, but whatever!)
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Old 08-20-2003, 11:11 PM   #4
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for the DD

Serial port is used for the connection to the ODB-II, the parallel port is ALSO used as a hardware key.

a pc card option is avaible for those with no parallel port.. as emulation (like though docking or usb) will not work.


and yes.. very good read, thanks Jon


Edit.. i'd like to point out that the EcuTeK is NOT vishnu's. Shiv may provide feedback to Stephen of ecutek, but its not of Vishnu. Vishnu is only the most known tuner of the EcuTeK.. Tuan at GRD is probably 2nd. I trust my car with either tuner.

Last edited by BOFslime; 08-20-2003 at 11:24 PM.
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Old 08-20-2003, 11:20 PM   #5
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Something that wasn't included above, which I found very informative when i leard of it, as there are MANY on this board that swear intakes are of no real gain, and usually hurt.

EcuTeK has the ability to adjust for intake size's. This means that you can actually see the right amount of air for a larger intake/cai etc... without such poor work arounds such as simply adding fuel. with the EcuTeK, intakes are beneficial

================================

Induction Kits and ECU Calibration

The Mass Air Flow or MAF sensor found on all turbo charged Imprezas is one of the most vital engine components for safe, smooth power production. Furthermore, one of the most common 'upgrades' fitted to these vehicles is a replacement induction system. This 'upgrade' often upsets the air flow metering and causes poor driveability and/or engine damage. This article details a method for successfully integrating an aftermarket induction kit onto the Impreza, retaining driveability, safety and increasing power.

Credit must be given to Lachute Subaru (one of our EcuTek partners) for the measurement data published in this article.

Induction Kit Aims

The goal of replacing the standard induction kit on an Impreza is to derestrict the passage of air from the ourside air to the turbo. If done correctly, the result is improved turbo spool up, faster throttle response and higher top end power. If done incorrectly, the result is often higher intake temperatures, lean running, poor driveability and in some circumstances engine damage.


Mass Air Flow Sensor Operation

A mass airflow sensor assembly consists of a sensor element mounted inside a tube of a known cross sectional surface area (CSA). The sensor works by measuring the heat lost from the sensor's heated wire or film to the air that passes it inside the tube. The greater the mass of air moving past the sensor in a given period, the greater the cooling effect. The sensor produces an output voltage that increases with increased air mass passing across the sensor. This voltage can be converted to a mass air flow rate.

In order to make sense of this voltage, the ECU is calibrated so that it can convert this voltage into an air flow rate. Below is the standard air flow sensor scaling map present in every Impreza.



Incorrect Operation after Induction Kit Installation

The cross sectional area (CSA) of the tube is extremely important to correct metering of air flow. For a given mass air flow rate, the proportion of the air that passes over the sensor element decreases as the size of tube increases. In real terms, if the sensor element is placed in a larger diameter housing, the sensor will produce a lower output voltage for the same mass of air passing down the tube. This voltage will then be converted by the ECU into an incorrectly low air flow rate, resulting in incorrect fuelling. In order to cure this problem, the ECU must be recalibrated to understand the new relationship between the air flow sensor output voltage and actual mass air flow rate.

ECU Calibration for a New Induction Kit

In order to correctly calibrate the ECU for the new induction kit, the relationship between air flow and output voltage of the air flow sensor must be measured. Initial thoughts would suggest using a flow bench to do this, though very few tuners will have access to a calibrated flow bench capable of flowing 300 grams per second of air.

In actual fact, all Subaru tuners do in fact have this flow bench in their workshops - the vehicle itself ! By plumbing the the two induction kits in series (the standard system and the new system), it is possible to draw the same mass of air through each induction kit. With a mass air flow sensor in each induction kit, it is possible to measure the sensor output from each kit. By taking the vehicle through a wide air flow range on the dyno, it is possible to measure the relative outputs of the two sensors when mounted in the two induction kits. A tool such as DelatDash External Sensor Logging may then be used to record the data for later analysis.

The result of recording this data is a graph showing the relative outputs of the two induction kits for a range of air flows.



But what does this data tell us ?
Well, taking the highest output voltage that was recorded in this test, the standard induction system outputs 4.5 Volts - looking at the ECU's air flow sensor scaling, the ECU will interpret this voltage as 255 grams per second of air flow. Now, for the same air flow (remember, the two kits are measuring the same air flows rates because they are plumbed in series), the aftermarket kit outputs 3.8 Volts - looking at the ECU's scaling map again, the ECU will interpret this as 150 grams per second of air flow. That is a 41% error !

Ok, so this induction kit would destroy the engine if we plugged it on now. How can we fix it ?
Quite simple really. We change the scaling map in the ECU so that when it sees an air flow sensor output of 3.8 Volts that it is in fact 255 grams per second of air flow. After a number of measurements and smoothing the graph, the following new air flow sensor scaling map was produced.



This new calibration was then programmed into the ECU, providing dramatic improvements to this car.



For more information on this specific induction kit conversion, please contact Benoit at Lachute Subaru

Last edited by BOFslime; 08-20-2003 at 11:29 PM.
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Old 08-20-2003, 11:33 PM   #6
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Quote:
Originally posted by BOFslime
Something that wasn't included above, which I found very informative when i leard of it, ...
Well, no, it wasn't included, because it's at the very stationary site from which you quoted. Why doesn't everyone just go to www.ecutek.com?
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Old 08-20-2003, 11:35 PM   #7
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Quote:
Originally posted by Jon [in CT]
Well, no, it wasn't included, because it's at the very stationary site from which you quoted. Why doesn't everyone just go to www.ecutek.com?
not everyone pokes around to all the corners. I can remove it from your thread if you wish?
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Old 08-21-2003, 02:18 AM   #8
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EcuTeK has the ability to adjust for intake size's. This means that you can actually see the right amount of air for a larger intake/cai etc... without such poor work arounds such as simply adding fuel. with the EcuTeK, intakes are beneficial

Yes that is possible but will take a fair amount of time and work to do such a thing. it is not something you can just be done in a few hours time.

The best approach is to pick one intake that everyone can use, something actually worthwhile using. Say a 4 inch inlet or something to that affect and then tune that one.


Bill another EcuTeK tuner
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Old 08-21-2003, 10:49 AM   #9
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Quote:
Originally posted by skywalker
EcuTeK has the ability to adjust for intake size's. This means that you can actually see the right amount of air for a larger intake/cai etc... without such poor work arounds such as simply adding fuel. with the EcuTeK, intakes are beneficial

Yes that is possible but will take a fair amount of time and work to do such a thing. it is not something you can just be done in a few hours time.

The best approach is to pick one intake that everyone can use, something actually worthwhile using. Say a 4 inch inlet or something to that affect and then tune that one.


Bill another EcuTeK tuner
and how much to you charge for that time? It can certainly be done, but as a customer it's just a question of how much money do you want to spend today?

spoken by someone with over a 100 pulls on Vishnu's dyno
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Old 08-21-2003, 10:56 AM   #10
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All is good.. but what about the side bar in the article does anyone care to post that part?

Thanks,
Imprezd~
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Old 08-21-2003, 03:39 PM   #11
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Quote:
Originally posted by skywalker


Yes that is possible but will take a fair amount of time and work to do such a thing. it is not something you can just be done in a few hours time.

The best approach is to pick one intake that everyone can use, something actually worthwhile using. Say a 4 inch inlet or something to that affect and then tune that one.


Bill another EcuTeK tuner
Yes.. it does take time to calculate the airflow of a new intake. This is all in the tuners ability, and won't beable to be done for just anyone that walks in with some off the wall intake. atleast without some time to test with it. I would hope that tunners would take some time to cover the popular intakes.
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Old 08-22-2003, 06:28 PM   #12
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can't just ECUtek just calculate the amount of air that an intake's certain inner diameter can take in. That way the tuner can just select the ID from a drop down menu and load pre-calculated data and then just fine tune. Common sizes would be:

65mm
70mm
and
75mm
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Old 08-22-2003, 06:52 PM   #13
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Quote:
Originally posted by zacek
can't just ECUtek just calculate the amount of air that an intake's certain inner diameter can take in. That way the tuner can just select the ID from a drop down menu and load pre-calculated data and then just fine tune. Common sizes would be:

65mm
70mm
and
75mm
I think the problem isn't just the change in diameter but the uneven changes at different amounts of air flow caused by the design of the new intake. This is why their is the plot of the Ideal replacement and the 71mm induction pipe.
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