Hello first off PLEASE DO NOT REPLY if you do not have any reliable or validated information. This is for imperical data only. NO opinions or anacdotal experiences. This is a page for proof and numbers. Create your own page if you dont agree with the above. I will delete any info that is not relevant or truly helpful.

I want to create a page where all the correct and relevant information is gathered with regards to the Bosch MP9 Fuel injection system as it came from the factory. No funny frankenstein conversions. The only conversions I want to discuss is converting imported engines such as Japanese imported 2E, ADY and AGG engines from the Digifant or Siemens System to Bosch MP9.

I have purchased an imported a 2.0 8v AGG engine (Japan Import) which I want to install into my VW T3 Syncro. The engine comes without a ECU so I needed to check how one can use the AGG engine in SA without needing to import parts. This is what I have found out so far and I will be adding to the list as group members post info. For my application I will also require a new wiring loom as my engine did not come with any wiring.

There are some key questions I have:

1. What components are needed for a Bosch MP9 System to work as intended?
2. How is the MP9 System Different from other fuel injection systems found in other regions? For example the Golf Mk3 2.0 GTI came with either a Bosch Digifant or Siemens Simos system which is used in the rest of the world. Why did VW SA develop the MP9? Is it really better or just different?

What is the MP9 System?

The Bosch MP9 (Motronic MP9) is an engine management system introduced in the mid-1990s, only used in South African Volkswagen models like the Citi Golf, Polo 6N, and Golf Mk3. It integrates fuel injection and ignition control, relying on a MAP sensor instead of a MAF sensor to simplify the system.

The components:

1. ECU - (Aka Computer Box)

ECU Part Numbers:

2.0 Engines - 0 261 204 026 (1 HS 906 258)
1.8 Engines - 0 261 204 156 (6K0 906 258 B)
1.6 Engines - 0 261 204 157 (6KS 906 258B)
1.4 Engines - 0 261 204 959 (1 7S 906 258 C)

**Please let me know if there are any other part numbers, but post pictures of the ECU please**

Note: ECU's are often flashed to be able to be used on different engines. A 1.4 ECU can be flashed to a 2.0 fuel and ignition Map. But I am very careful when it comes to ECU's that have been tampered with. You have no idea what the guys felt like uploading or changing and if they have been correctly flashed with OEM maps. Use your common sense and buy from people with a good reputation and who are known in the community. Buy from people you trust. Personally I chose to buy good x2 and original 2.0 ECUs from a reputable buyer that have not been flashed, only the immobilizer has been removed. They cost more but I am sure it will be worth it.

Immobilizer: The immobilizer in the context of the Bosch MP9 engine management system is an anti-theft feature designed to prevent the engine from starting unless a correctly coded key is present. It is a part of Volkswagen's vehicle security system. They can be switched off on the ECU by someone who knows what they are doing. Boxes where the immobilizer is turned off are commonly sold as "Open Box" whereas with immobilizer they are sold as "Closed Box"

2. Distributor

Requires a distributor with a 4-gap rotor plate, providing the ECU with timing signals.

MAP Sensor (Manifold Absolute Pressure)

Function: Measures intake manifold pressure to assist in determining the optimal air-fuel mixture for combustion.
Part Number : 0 261 230 011 (I am not sure if this is the correct number)

3. Idle Control

Function:

1. Idle Speed Regulation: The integrated system adjusts the throttle position to maintain a stable engine idle speed under varying conditions, such as changes in engine load or temperature.

2. Cold Start Enhancement: During engine warm-up, it increases the idle speed to ensure smooth operation until the engine reaches optimal operating temperature.

3. Load Compensation: It compensates for additional loads from accessories like air conditioning or power steering by adjusting the throttle position to maintain consistent idle speed.

Part Number: Unknown. Info appreciated.

4. Throttle Position Sensor (TPS)

Function:

1. Throttle Position Monitoring: The TPS continuously measures the position of the throttle plate, providing real-time data to the Engine Control Unit (ECU) about how far the throttle is open.

2. Fuel Injection and Ignition Timing: Based on the throttle position data, the ECU adjusts fuel injection quantities and ignition timing to optimize engine performance, fuel efficiency, and emissions.

3. Acceleration and Deceleration Response: The TPS enables the ECU to detect rapid changes in throttle position, allowing for immediate adjustments to the air-fuel mixture during acceleration or deceleration.


5. Fuel Injectors:

Part number: Unknown. Info appreciated

6. Intake Manifold

There seem to be differences in the intake manifold when it comes to the engines available in the rest of the world. The reason for that might be because the Bosch MP9 ECU works off of a MAP (Manifold Absolute Pressure) instead of a MAF (Mass Air Flow) as well as a TPS (Throttle Position Sensor). I am not sure if the intake ports match up exactly with imported engines. Some people say it is not an exact match, if you have evidence in terms of pictures please post them below comparing the manifolds directly.

Please let me know if you have any part numbers for the manifolds. Maybe there are also different manifolds for 1.4, 1.6, 1.8 and 2.0 engines, each with a different diameter port. The only way it to compare part numbers and measure the diameter.

There are more parts like the knock sensor, temp sensors, crank position sensors, oxygen (o2) sensors and some more which should be stardard across all of the engines regardless of the region.


Differences between the Bosch Digifant, Bosch MP9 and Siemens Simon fuel injetion Systems.

The Bosch MP9, Siemens Simos, and Volkswagen Digifant systems represent three distinct approaches to engine management in various Volkswagen models over different eras. Each system reflects technological advancements, market needs, and regulatory requirements that shaped their design and deployment.

The Bosch MP9 system, introduced in the mid-1990s, was primarily used in South African models like the Citi Golf, Polo 6N, and Golf Mk3. It was designed for simplicity, reliability, and adaptability to local conditions, such as variable fuel quality. The MP9 utilizes a Manifold Absolute Pressure (MAP) sensor instead of a Mass Air Flow (MAF) sensor. The system integrates key components, such as a throttle body with an idle control valve and a throttle position sensor. The MP9 also includes a knock sensor, enabling adjustments to ignition timing for better engine protection and performance.

In contrast, the Siemens Simos system, introduced in the mid-1990s and used predominantly in Europe, represents a more advanced approach. It integrates both MAP for precise air intake measurement and employs sequential multi-point fuel injection for enhanced efficiency and performance. The Simos system features adaptive learning capabilities, allowing it to optimize engine parameters based on driving conditions. This system was commonly found in models like the Golf Mk3 with 1.6L and 2.0L engines (ADY and AGG) and was tailored to meet stricter European emissions standards while delivering improved drivability and responsiveness.

The Volkswagen Digifant system, an earlier iteration introduced in the late 1980s, marked a transition from mechanical to digital fuel injection. Widely used in models such as the Golf Mk2 and early Mk3, as well as the Jetta and Passat, it combines basic digital fuel injection with ignition control. The Digifant system typically relies on a MAF sensor for air measurement and uses an external idle stabilization valve (ISV) for idle control. While effective for its time, it lacks the advanced features of MP9 and Simos, making it less efficient and adaptable to modern demands.

Is the MP9 System Better?

Well.. Thats not for me to say. I do not have enough experience with these engine management systems. I do suspect that the Bosch MP9 system is a sort of compromise. Something in between Digifant and Siemens Simos. I believe that VW SA had to create a reliable solution tailored for the South African emerging markets, balancing cost, simplicity, and performance. Any input here will be appreciated.

Here are some additional part numbers for those interested:

Siemens Simos ECU 2.0 8v (Such as AGG engine) : 037 906 025 R (5WP4 256)
Digitant ECU 2.0 8v (2E engine) : 037 906 022 ED ( 0 261 200 328)

I will update this main text based on answers posted below. I will only include and use information from trusted sources and none of the "a friend of a friend said that the MP9 makes 50% more power nonsense"

I have found this well documented forum of someone converting an imported AGG engine to MP9: viewtopic.php?t=221269

Key Takeaways:

If you have a 1.4 MP9 donor you can swap over most of the parts and be fine. Questionable is: Intake Manifold and Injectors.

He noted the MP9 Intake Ports from the 1.4 engine is considerably smaller than the intake ports that come with the imported 2.0 AGG engine.

I would like to dig a litte deeper into exactly what intake manifold is best. Many guys say any MP9 intake just bolts on, but just because the bolt pattern is the same does NOT mean the intake ports are optimised for a 2.0 Engine. If the MP9 ports are indeed smaller then it will cause a significant restriction in the engine. Misaligned ports between the Intake Manifold and Cylinder head might also lead to turbulent flow and more restriction.

If anyone out there would be willing to take a picture of their MP9 intake manifolds WITH PART NUMBER and post them here so we can compare that would be awesome. If someone has a stock factoty fitted MP9 Golf 3 2.0 8v and can send us a picture of the Intake Manifold part number that would be a great help.





After looking closely at pictures of the AGG/2E/ADY Cylinder head, you can see that the intake port is shaped in a way so that the fuel injector can spray directly at the valve, which helps combustion, keeps the valve cool and cleans carbon deposits. Clearly the MP9 Intake from South Africa is not the same.

Here are some pics of AGG/2E/ADY 2.0 8v Heads.

ECU Pin-Outs Diagram

I am still busy doing research on the MP9 System and how it works as I want to optimise it for my application in my T3 Syncro Expedition vehicle with an AGG engine which needs low end torque and good fuel economy above all else.

One problem with installing the MP9 System into my bus it that I will be running a completely different air filter and tubing as well as different exhaust.

That combined with aging components and aftermarket replacement means that the engines breathing characteritics will be changed signigicantly from how VW SA designed it to be.

The issue is the MP9 system, whilst simple and robust, is quite a "dumb" system known as a "Open Loop" System. Open-loop operation relies on predetermined fuel maps without sensor feedback, while closed-loop operation adjusts fuel delivery in real-time based on feedback from sensors.. In other words, the MP9ECU can't tune itself at all any relies only on the VE Map (Volumetric Efficiency) which has been uploaded to it. This map was developed by VW SA based on the engine parameters. Better ECUs use an O2 sensor (Lambda) to measure the ratio of air and unburnt fuel in the exhaust and then adjusts the fuel injections to keep it in the optimal range. VW SA decided to ommit the 02 sensor from the MP9 system (Most likely for cost saving)

This causes the MP9 to have significantly worse Volumetric Efficiency and leads to higher fuel consumption.

Here is an interesting writeup I found on this topic:

"The posting:

Bosch: SA MP 9.0 Motronic Fuel Injection System

Peter B. from Tiico called me in November of 1999 in a complete panic…he was bombarded with calls noting serious cold start issues, engines flooding and copious amounts of black smoke belching out the exhaust once they did start. My answer was: "sure, I bet they are…we have a bunch here…and they will continue to be like that w/o an 02 sensor. The 'open loop' system was not designed properly for what was needed in North America." Of course he wanted an easy magic fix such as replacing the fuel injection coolant temp sensor like all the North American Digifant injected models, but, that would not be the case…and so, it began.

In the previous post I spoke about the S. African "Volksie Bus" as being carbureted off of the production line. Because of this, they never injected the in-line Vanagon (T3) in SA until they went to the 5 cylinder Audi platform. Realizing that a carbureted conversion could not be sold in this country and even come close to passing smog... Peter B. and Remtec decided to use an injection system produced in South Africa based off of the "City Golf", or what we call the Rabbit, because the engines were almost identical and manufacturing would be simple based upon their current "City Golf" production numbers at the time. The City Golf was everywhere in SA and like the Fox in other countries, their on-board operating systems were produced as an inexpensive third world budget system. To make things worse… at least the Fox in North America was designed with an 02 sensor and fully mapped cold start capabilities… that was not the case with the City Golf or earlier Tiico's. They had neither.

That first winter we ran straight in to it all in one week's time in November in Northern New England a day before the call came from Peter. The lot was full of as many no start Tiico's as ones we were getting ready to install. We had him send us an ECU pin out for the system. All similar VW Bosch operating systems that run Motronic, mono-Motronic etc., had their data wire going into the ECU on pin #38. So we added a 3 wire 02 sensor and ran a shielded Data wire into pin #38. Immediately, the system reacted as it would in closed loop! The vans started right up cold, the idle hunted a little but not much worse than any Golf/Jetta and they were not belching black smoke and they now ran decent at 25 degrees Fahrenheit. We observed at start-up cold the 02 sensor voltage remained constant at about .4 volts and then as the vehicle warmed up… even better it started to oscillate normally between .2 and .8 volts!!

The following week Peter asked me to join in on a conference call with him and one of Bosch SA's Engineers. The guy at Bosch told us we must be mistaken. He supposedly had personally written the operating program we were discussing and that it was not capable of doing what we were describing! We told him we verified the results on 4 different vehicles with our oxygen analyzer matching the scan tool values. The phone call ended fairly abruptly after faxing over the results.

The guy from Bosch called Peter about 5 weeks later and actually confessed that the system reacted exactly as we mentioned it would once they were able to simulate the cold factor in a freezer tank at their Johannesburg facility. These ECU's can be identified by the part #RSU 906 258 or RSU 906 258A. Here is a breakdown on them, just in case you happen to still have one of these (there are still plenty out there):

They were originally set up Open Loop and were not originally calibrated with an 02 sensor.
They were set up and designed by Bosch in SA using 96 Reef octane which Bosch translates into 91 to 93 octane here in North America
The system was simply not designed parameters wise to be able to pull knock back far enough to a safe range when using 87 octane especially at RPM ranges of 2500 or more. The Tiico in-line engines are interference in design. They are 10 to 1 compression ratio and have extremely high cylinder head pressures. We've built several long-blocks over the years for PeterB., because of this issue. Burnt pistons on these engines are almost always because of 87 octane being used for long periods and or a combination of this and incorrect ignition timing. We know there are those out there who are extremely lucky using 87 octane regularly and have not had a problem. Here is the reason: Either their timing or adaptation values are off enough(incorrectly set) by accident… to offset and or compensate for the burn characteristics of the fuel they are using. Most of those engines can make it anywhere from 70,000 to 100,000 miles…but not much more than that. One gentleman who posts on this forum regularly has grenaded 2 engines before because of this… but continues to do it even on his current long block which we built for him. We've made it very clear to him that zero warranty will be expressed. If you are out there…please stop telling others to do it so long as they are not pulling long steep hills!! Long hills or not…it is not o.k. The best results and longevity will be achieved by this product by running 91 at all times or if available 92 or 93.
Adding a 3-wire 02 sensor as mentioned will dramatically change the way these run especially in cold temperatures…they are almost not run able w/o the 02 added in temperatures of 25 degrees Fahrenheit or less.
Even though the ECU recognizes the signal and does make a difference in drivability and engine performance… the parameters are not even close to correct… and that is why the systems tend to be leaner than they should be under certain loads and RPM and Too Rich fuel mixture wise under others… and it is not always linear or constant.
This system was designed to re-use the Water Boxer injector Bosch part# 0 280 150 206 only.
This system is capable of clearing DTC's but most will return within a day or two. Although the system obviously recognizes the 02 sensor signal… due to incorrect parameters in the file formatting they will continue to throw fault codes showing incorrect 02 sensor signal or no 02 sensor signal and adaptation limits either exceeded or not met.
This system is not capable of learning on its own over time and cannot automatically adjust its' fuel mapping parameters at altitudes above sea level.
Ignition timing on these systems are to be set @ 10 degrees BTDC using proper basic setting procedure (it requires the use of a digital timing light and proper scan tool**)
Adaptation settings historically @ sea level has shown to be pretty reliable and constant between: 00128 and 00131
Adaptation for altitudes near 1500 ft and above can range between 00139 and near 00165 @ about 6000…**problem with this as mentioned previously… every time you go back and forth between seal level changes the adaptation and ignition timing need to be re-set.
We have had decent success flashing and upgrading these ECU's to the most current calibrations but not all of them are flashable and you do not know until inside the ecu.
If you have one of these systems and it stores the fault code or DTC: "Oxygen sensor control limit exceeded " and cannot be cleared due to a hard fault are basically fried or technically locked out from the oxygen sensor portion of the file formatting. Those who have run across this on their own know that The only solution is to upgrade to the newest 4-wire 02 sensor system .


Second Generation ECU's part #RSU 906 258B or C:

They are a primitive "closed loop" system using a 4-wire 02 sensor with the data wire going to pin #38
They were designed using the water boxer injector and a mild performance cam of 268 instead of a 264** Bosch never discussed this with Remtec or Peter B. ahead of time and as a result it took us here almost a year to figure out what was going on with this system and its peculiar glitches. The mild cam was not that big of a deal except at idle until the engines broke in… but the water boxer injector was! PeterB. asked them to use the A2 injector #037 906 031AK that fits Digifant Golf's and Jetta's in North America. They are more reasonably priced and have flow characteristics more consistent with the cylinder volume of an in-line engine. For whatever reason they didn't. They also forgot to check all the appropriate boxes while formatting to shut off erroneous codes such as "glow plug monitoring" etc., and as a result they throw more codes than the earlier systems!!
These ECU's learn on their own and do not need to be adjusted at altitude
Ignition timing on these is to be set @ 6 degrees BTDC using the proper basic setting procedure.
In summary if you have ECU #RSU 906 258 B or C make sure you are using waterboxer injectors…your system will run much better. And make sure the timing is set @ 6 BTDC. If you have this system and have already upgraded to the A2 fuel rail set-up…you'll need to update your ECU as well.


Current Third Generation ECU's part #RSU 906 258D:

it took them forever… but, third time is a charm!
I was so frustrated with the 258 B and C ECU's that I personally went over to Bosch SA to get it sorted on our own dime.
A head of time…We sent Bosch the 037 906 031AK injectors and pressure regulator along with the 2.1L Cat and 1.9L rear muffler and current 4-wire 02 sensor. We also made sure they were using the correct map senor that had parameters to operate below 15 degrees Fahrenheit and verified personally that they actually used all the correct components we sent them when they did their calibration.
The result is a closed loop fully calibrated ECU. They do not throw erroneous 02 codes or any others that are not warranted.
The ECU's self learn @ altitude and wipe the pants off of the earlier systems in regards to being more emissions friendly.
Ignition timing is to be set @ 6 BTDC using proper Basic setting procedures. I'm sure the forum's archives list proper timing procedures…but if anyone is confused about it…do not hesitate to contact us.
They are to be run on a minimum of 91 octane.
Sadly, only one production run of conversions was completed before Peter B. went out of business.


We kept our contact with Bosch SA and as a result we were able to bring in 40 new ECU's in '09. We also brought in about 100 new e-proms to start an exchange program to flash, sort and upgrade those with previous issues. Unfortunately, not all the ECU's react properly to the e-prom flash…mostly the RSU 906 258A's.

In summary, too little too late for the Tiico conversion in regards to ECU issues that should have never occurred in the first place if Peter B., Remtec and Bosch were on the same page. We can get more specific in regards to particulates per million documentation emissions wise on the new system and what Bosch shows for specific values on knock regulation parameters in regards to octane if anyone would feel more comfortable with that assurance.

Hopefully, this will help owners sort out any long standing issues they've been struggling with on their conversions. We appreciate everyone's support. We will continue to import any and all of the hard to find conversion items to keep a steady flow for everyone out there. "

There seems to be a REMOTE possibility that the MP9 ECU might be able to support a 02 sensor which should improve fuel economy. The previous text I sent mentioned that the ECUs for the Tiico conversion (It was a Inline 4 conversion kit for VW T3s provided from the Factory in South Africa) could read O2 sensors even though they were not originally designed for it.

The information is sparse. It would be very cool if someone with the proper tools could do a test and check. Anyways here is some materials about the MP9 ECU which also mentions a pin for the Lambda/02 sensor.

Link to the whole document. Has info on all the VW inline 4 pin outs fro Digifant, MP9 and Siemens Simos : https://acrobat.adobe.com/id/urn:aaid:s ... 3d516615a3