Replacing Bosch jetronic with MegaSquirt EFI - Page 5 - Mercedes-Benz Forum

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post #41 of 124 (permalink) Old 07-16-2007, 05:17 PM
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Guys,

I seldom hit this part of the forum but glad I did today. I have been trying to dig into MS for the past month as I start some work on a M119 motor in one of the E500s that I want to work around the stock ECU/ASR/etc. Is there anywhere that you guys have posted up a review of your specific projects [car, engine, mods, plans, expectations, etc]? Benzworld does not have a Performance Sandbox per se to play in. Are all the conversations going on here and on the thread linked at the start of this thread?

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post #42 of 124 (permalink) Old 07-16-2007, 08:59 PM
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Intake manifold questions....

oughtsix:

Since I don't know what your system looks like, let me describe a few unusual features of the Lotus intake manifold to see if similar techniques were used on your Benz...

The engine is a 2.2 liter 4 cylinder, with four CIS injectors placed as you would expect in each runner of the intake manifold. But there are also two additional "air rails" molded into the intake manifold that provide small amounts of air to each port under various conditions...

One air rail is used with a cold-start injector to provide a few seconds of extra fuel at the moment of starting. The air for this rail runs through an "air bypass valve" with a bimetal spring. When the engine is fully warmed up, this air supply shuts off. A different "Thermal Time Switch" controls the cold-start injector time from 0.1second up to about 5 seconds when starting in very cold weather.

The other air rail appears to be a constant "leak" around the air metering box which they say improves low speed operation by adding air in the vicinity of the injector under very low airflow rates from the throttle body.

It all sounds like tweaking and patching a system that just doesn't work right inthe first place.

Does the Benz K-Jetronic have any of these Band-aids? Did you weld-up these extra holes in the intake ports? Did you have any trouble re-machine the existing holes from the CIS injectors to take stock electronic injectors? This is the only part of the conversion that I think I might have some difficulty with.

... Jeff
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post #43 of 124 (permalink) Old 07-17-2007, 10:23 AM
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Quote:
Originally Posted by mcbear
I just found the Megasquirt thread on Benzworld [although it seems I live on BW]. I have a small restoration shop here in Kentucky and one of the projects that we are working on is a 1993 500E. We are looking for performance gains, clean workarounds for the ASR defeat [although we can do that] cooling assistance and ECU options as we move to a 6Sp manual tranny for the car.

I know the ECU technology on the 500E is from 1984 or so and there has to be some performance/economy gains available if looked at correctly. My problem is I am just not familiar enough with programmable ECU work and changing the EFI to address that from the get go.

Reading your posts I understand you have a headstart. Any enlightenment would be appreciated on the M119 motor.

Thanks
mcbear,

I want you to know that I am not an automotive tuning professional I am a systems programmer with an interest in cars. I own a 1980 450slc which I have become pretty familiar with over the years but I have no other Mercedes experience. Other Mercedes of this era have very similar engineering and fuel systems. I have no familiarity with a 1993 500e and do not know what type of fuel injection system it uses. If it uses a K-Jetronic (CIS) or D-Jetronic fuel injection system I might be able to talk to you about it with some level of knowledge. Do you know if your fuel system is a CIS type system?

From what little knowledge I have of computerized fuel injection systems they work on a very simple concept. A computer opens a fuel injector to allow fuel to flow through then closes the injector after a set amount of time (It pulses the injector). Most computerized fuel injection systems build on this basic concept by predicting how much fuel the engine will require based on a series of measurement. On megasquirt these measurements are RPM, MAP (manifold absolute pressure or simply vacuum), The temperature of the incoming air IAT, The temperature of the coolant CLT and the position of the throttle TPS.

With Megasquirt the two major variables from the list above it uses to calculate the amount of fuel required by the engine are RPM and MAP (The speed of the engine and the load on the engine measured by vacuum). The other variables are used fine tune the required fuel value derived from these variables. The power of the MegaSquirt computer is its ability to compute a complex equation with these variables in real time.

Another major feature of Megasquirt is its ability to use feedback from the engine to further refine the required fuel calculation. Most Megasquirt users pair their Megasquirt with some sort of wideband O2 sensor. An O2 sensor sits in the exhaust stream and will tell you if you are running rich / lean / or right at stoic (14.7:1) by analizing the burnt / unburnt exhaust gasses. A wideband O2 sensor has the additional capability to tell you what the actual air to fuel ratio (AFR) is which means it will tell you how rich or how lean your mixture is and let Megasquirt know how much of a change it needs to make to the calculated value.

Megasquirt II also has the ability to let you set ignition timing based on the same variables listed above. This allows you to run a much more aggressive timing curve than you could with centripetal advance or vacuum advance resulting in more power.

You might already be familiar with all of this in which case I am sorry if I am patronizing you.

Most of MegaSquirt functions are also handled by other aftermarket ECUs. So what makes MegaSquirt different? What MegaSquirt has going for it that the other after market ECU's don't is the shear number of genius level people working in collaberation to make MegaSquirt the best ECU available. There is NO other ECU out there that has the level of MotorHeads, Tuning specialists, Engine Builders, Electronic Engineers, Computer Engineers and Programmers working together (and frequently argueing) that MegaSquirt has. This open source expertise just can not be matched by any private ECU venture out there. One of my favorite MegaSquirt features is XTAU. When I first read about XTAU correction I was simply amazed. The XTAU correction formula calculates via a user supplied variable the amount of fuel that is left on the walls of the intake manifold and isn't available to power the engine for a particular stroke but will be available to power the engine on future strokes. I have never turned on the XTAU correction feature and I really can't imagine using it. But I was simply amazed to find out that it exists in MegaSquirt and several people took the time to turn it into a practical tuning parameter. This sort of fine tuning is way beyond my capability but it is nice to know too what level Megasquirt is capabile of going.

Personally I am very confident that my Mercedes is running at a level of tune much better than it was ever capible of from the factory. At the same time I have yet to install a working TPS (throttle position sensor) and tune the engine for optimal power during acceleration. Did I mention I have no formal automotive background? I am amazed at the level of performance I have been able to achieve with my very limited knowledge. I am sure one of the knowledgable tuners could find all sorts of power in my engine that I have no clue about but I am still very confident that my engine was never capable of running as well with the stock K-Jetronic system as it does currently with my MegaSquirt implementation.

I hope you don't mind me posting this on the public board to share with others? Do you have any specific questions about Megasquirt?

Last edited by oughtsix; 07-17-2007 at 11:32 AM.
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post #44 of 124 (permalink) Old 07-17-2007, 11:36 AM Thread Starter
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Quote:
Originally Posted by LotusJeff
....The engine is a 2.2 liter 4 cylinder, with four CIS injectors placed as you would expect in each runner of the intake manifold. But there are also two additional "air rails" molded into the intake manifold that provide small amounts of air to each port under various conditions...

One air rail is used with a cold-start injector to provide a few seconds of extra fuel at the moment of starting. The air for this rail runs through an "air bypass valve" with a bimetal spring. When the engine is fully warmed up, this air supply shuts off. A different "Thermal Time Switch" controls the cold-start injector time from 0.1second up to about 5 seconds when starting in very cold weather.

The other air rail appears to be a constant "leak" around the air metering box which they say improves low speed operation by adding air in the vicinity of the injector under very low airflow rates from the throttle body.

It all sounds like tweaking and patching a system that just doesn't work right inthe first place.

Does the Benz K-Jetronic have any of these Band-aids? Did you weld-up these extra holes in the intake ports? Did you have any trouble re-machine the existing holes from the CIS injectors to take stock electronic injectors? This is the only part of the conversion that I think I might have some difficulty with.

... Jeff
My 78 K Jetronic has exactly the "features" you've described. I did block off the holes and capped the two ports in the upper intake that they lead from.

The Bosch injectors I got from a 5.0 Mustang fit perfectly into the stock CIS injector holes in the head. ought six and I recommend reversing the order of the O-ring and spacer at the botom of the injector to make it seal better, though.
I also machined a groove into the middle of the injector barrell to accomodate an additional O-ring to make a tighter air seal but I suspect it isn't really necessary.
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post #45 of 124 (permalink) Old 07-17-2007, 01:36 PM
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Quote:
Originally Posted by oughtsix
mcbear,

I want you to know that I am not an automotive tuning professional I am a systems programmer with an interest in cars.

...

Do you know if your fuel system is a CIS type system?

...

Most of MegaSquirt functions are also handled by other aftermarket ECUs. So what makes MegaSquirt different? What MegaSquirt has going for it that the other after market ECU's don't is the shear number of genius level people working in collaberation to make MegaSquirt the best ECU available. There is NO other ECU out there that has the level of MotorHeads, Tuning specialists, Engine Builders, Electronic Engineers, Computer Engineers and Programmers working together (and frequently argueing) that MegaSquirt has. This open source expertise just can not be matched by any private ECU venture out there.

...
Thanks for the response.

I agree with your assessment of MS and the cadre of Engineers and bit pushers who seem to be giving this serious attention. I appreciate the open source concept. As a mostly retired systems architect I have a fair understanding from the 30K foot level but have not jumped in yet.

By the way, the 500E uses the Bosch LH system. I will dig up the specs on that over the next few days and start going through everything. While the car was state of the art in 1991, so were the PS/2 Model 80 and the brand new 386/20. I think things can be done to improve fuel management.

McBear,
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post #46 of 124 (permalink) Old 07-17-2007, 02:27 PM
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LH 2.2 ECU's
The Bosch LH-jetronic 2.2 ECU's are used on many Saab's and Volvo's from the mid 80's to the mid 90's. It's a MAF based fuel-injection system. It uses a "hotwire" air mass meter to measure the amount of air entering the engine. The system come in a few different configurations, the basic variant uses MAF, RPM, engine temp and WOT/idle-switch as inputs. The more advanced versions use O2-sensor input as well as IAC-motor output.

Quoted fromBosch LH-Jetronic Secrets...
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post #47 of 124 (permalink) Old 07-17-2007, 03:38 PM
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HBAR!

Good to hear from you. Have you had a chance to work on your install lately? I always seem to be too busy working on other priorities or too broke to afford the parts I need. Ocassionally I am able to sneak out of the house and work on some of the details. (Top detail right now is getting the passenger side seat back in).

LotusJeff,

Your system sounds exactly like my K-Jetronic system as HBAR stated. Being an 1980 car my jetronic also had a Lambda feed back circuit which took readings from an O2 sensor and injected extra fuel when it felt like it wanted to. My opinion of the K-Jetronic system is simply that I have never had the problems with a Carb that I have had with K-Jetronic. To me it is an overly complex mechanical brain with too few technicians trained on how to keep it properly tuned.

One of the things that BlueFang and Hbar pointed out was they didn't have an O2 sensor stock and it is a lot easier to drive your car down to a muffler shop to have an O2 bung welded in for a couple of bucks than it is to trailer the car down after you have started your install.

Like Hbar stated it sounds like your system functions the same way ours does. Megasquirt has the capability of driving a few different types of idle Air Controllers (IACs). I opted in my current configuration to use the bi-metalic heat activated mechanical IAC the came stock with my K-Jetronic system which also allows me to use the stock idle adjustment screw. This has been working great as I am able to use the existing IAC plumbing without having to do any fabrication while I work on other (more fun) parts of the installation. I adjust high idle by wrapping different amounts of electrical tape around the intake of the IAC valve. I adjust the low idle by the stock idle adjustment screw.

My cold start injector feeds into the IAC air stream the same way your does. I simply removed the electrical connection and the fuel plumbing to the Cold Start injector and left it in place. It has been doing a superb job of plugging the hole it was meant to. My cold start injector has a screw fitting for the fuel line which isn't very common on injetors. Plumbing the fuel lines to the injectors is one of the puzzles you will need to figure out. I believe between the three of us on this board we all plumbed the fuel to the injectors in a different manner. The megasquirt site is full of different ideas on how to accomplish this. Using 4 injectors with screw on fittings or barbed fittings is one way to accomplish this. If your four injectors are all inline and the injectors protrude above the rest of the intake you may consider making a fuel rail.

I might reccomend getting started by buying some injectors cheap off of ebay or from the junk yard and seeing how they fit in your intake. I think I paid about $25 for a set of 8 Mustang injectors on ebay. I had to do a bit of machining on my injectors to make them fit into my intake but bluefang and hbar didn't. Our K-Jet injectors came with some white plastic insulators that slipped over the injectors that gave them a profile very simular to an electronic injector. The K-Jet injector retaining clips were also easily modified on our Mercedes to secure the electronic injectors.

I just found out that my web server in my garage is barfing. I will reset it tonight and post when it is back up.

Last edited by oughtsix; 07-17-2007 at 04:07 PM.
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post #48 of 124 (permalink) Old 07-17-2007, 03:52 PM
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Quote:
Originally Posted by mcbear
By the way, the 500E uses the Bosch LH system. I will dig up the specs on that over the next few days and start going through everything. While the car was state of the art in 1991, so were the PS/2 Model 80 and the brand new 386/20. I think things can be done to improve fuel management.
I can assure you that programming MegaSquirt is no more dificult than programming the BIOS in a PS/2 to recognize a MicroChannel card.

I haven't done any real programming for MegaSquirt. It is more a matter of configuring MegaSquirt for my engine. It is amazing the amount of real programming that has been done for MegaSquirt on a public domain basis. I feel incredibally fortunate to be able to wreak such rewards from other peoples work. I hope to be able to give back a little to the MegaSquirt community some day.
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post #49 of 124 (permalink) Old 07-17-2007, 05:05 PM
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Quote:
Originally Posted by oughtsix
I can assure you that programming MegaSquirt is no more dificult than programming the BIOS in a PS/2 to recognize a MicroChannel card.

I haven't done any real programming for MegaSquirt. It is more a matter of configuring MegaSquirt for my engine. It is amazing the amount of real programming that has been done for MegaSquirt on a public domain basis. I feel incredibally fortunate to be able to wreak such rewards from other peoples work. I hope to be able to give back a little to the MegaSquirt community some day.
Cool. Sounds like I just need to get started. I have a test motor that I can do some configuration's on to get started before smoking one of the monsters. I just need to build a frame to hold the motor/tranny [with configurable tranny mount for those who know the rest of the story].

And if you know anyone who needs any accessory MicroChannel boards, I have about 30 setting in the basement.

McBear,
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post #50 of 124 (permalink) Old 07-17-2007, 05:08 PM
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Originally Posted by mcbear
And if you know anyone who needs any accessory MicroChannel boards, I have about 30 setting in the basement.

Maybe you shouldn't tackle this project if you have 30 microchannel boards sitting around that you couldn't get working????? Hahaha!
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