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Bosch LH adaptation maps

1K views 16 replies 3 participants last post by  samosali 
#1 ·
Please forgive me if I have the terminology incorrect here.

The Bosch LH injection system has a adaptation maps, wherein the computers 'learn' from certain driving conditions what adjustments need to be made to the primary parameter map. These adaptations are stored in a separate map, and are applied when the car is driven. Apparently it takes weeks or months of driving to build these adaptations. I'm especially concerned because I live at a fairly high altitude, so the stock FI map is not correct for my environment.

I often store my car for a week or more at a parking bay. I have a switch on the negative battery terminal to help prevent theft.

From what I've garnered during my studies, this adaptation map is not stored in non-volatile RAM in the LH computers, hence is lost when there is no battery power.

Is there a way to keep power fed to the computers to retain this map, while still cutting off power to systems like the starter and the lights? I was thinking of a small battery pack that could be wired in parallel to the main power to the LH computers.
 
#3 ·
I've read somewhere (put I can find my reference) that it is not stored in NVRAM as it is with modern ECUs.

When these computers were built, NVRAM was pretty expensive, so it would not surprise me if it were not used. Of course the baseline map is stored in an EEPROM.

I believe the 92-93 models (like mine) use the LH 2.2 model, which means they have adaptive Lambda control, hence the need for memory to store the adaptation codes.

The only way to confirm this is to have a means to read the adaptation map, and see if it gets erased when the battery is disconnected. Or to crack open an LH computer and look at the components inside.

Cheers
 
#9 · (Edited)
Most of this information here applies to the late OBD2 systems. Do you know which portion is applicable to the early ones?

Specifically, I would like to see a confirmation that the fuel trims are indeed stored, and not erased, when the battery is disconnected for extended periods of time.
The reason I am asking -- since I don't start my car regularly, I since the battery seems to deplete rather quick, I've opted to install a cut-off switch.

Steve
 
#10 · (Edited)
there are three pdf files above. I believe where LH is mentioned, it is for OBDI. I am not a super expert, but I think LH means same as OBDI. Later cars were ME-SFI. Like i said i am really not familiar with details, I am a pure amateur, just know that my car is LH and later ones are different with one computer instead with three of them.

The philosophy is very similar for OBDI and OBDII cars so third document which is actually written for oBDII ones can be somehow understood in light of OBDI cars, too. I am pretty sure that adaptation values for OBDI car can go +-10% which is not true for OBDII cars where they can go +-20% or even more (i forgot exact value, but i think it is 25%).

the second document talks mainly about adaptation regime and i again think that it is valid for both obdi and obdii cars. If it is a slow process for obdii cars then it is even slower and less reliable for obdi ones. That is how i understand the main point of the article. If you ask me this so called computer control of cars is something which in practice is far away from ideal. and if we can say that obdii strategy is good, then this is not true for obdi which is very limited.

of course i cannot be sure if adaptation values are for ever or only when there is enough juice in the car. It seems it will be difficult to get a proper answer because cars are meant to be ready for drive, so very few people will know something about cars which are frequently without a battery installed.
 
#11 · (Edited)
Big difference between LH-SFI and ME-SFI systems. It is not just the OBD2 capabilities.
The former is just the fueling (sequential multi-port) + some DTC.
The latter (ME) controls both fueling AND ignition.

They share the same genes, of course, but ....

Until is completely sort out the car and pay for registration and insurance, I will have to live with using the cut-off switch.

Steve
 
#12 ·
yes i know there are big differences, I just simplified things and made two "baskets"; obdi and obdii. can you please tell me which cut-off switch exactly. I had battery drain recently and i think it was my ipod on aftermarket radio. I removed the ipod but still I would like to prevent such situations in the future if it wasn't it.
 
#14 ·
Guys,

This is the switch that I use on all my cars (and boats, and my RE system at home):

https://www.amazon.com/NOCO-ID220S-...qid=1480925505&sr=8-2&keywords=battery+cutoff

Installs without the hassle of making a bracket and running new cables.

Steve: I'm with you. I'd like to find a way to read out the adaptation maps and verify if they are held in memory when the battery is cut-off.

The only reference I have been able to find is that the LH 2.2 uses 'Keep Alive Memory'. Thats common to almost all ECU units for cars going back to the 90's.

Now, if you google KAM, all references say the way to clear it is to disconnect the battery!

Now, this is not the same as the DTC's. They obviously must be stored in non-volatile RAM. Servicing will almost alway require disconnecting the battery, but the codes must persist for diagnosis.

So, the question for me at present: find a way to keep the ECU's powered when the battery is disconnected. As all the power for the computers in the coffin are sourced by the DM, it would make sense to see if a small fused terminal could be connected on the other battery side of the switch and run directly to the connector for the DM in the coffin.

As to the OBDI/II differences for the LH 2.2, I've also found something else:

"Peter Linssen writes: Bosch / Volvo LH 2.2 cannot deal with injectors larger than 310cc. ... LH 2.4 however will adapt for injectors up to 370cc and offer good performance ."

Anyone know what size our injectors are?
 

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#15 ·
ohhhhhh ... lol ............ this kind of switch :).

I meant something more sophisticated, like when voltage drops below 12.2 V for instance ... then electronics cut off the battery. It is dangerous i think because if something goes wrong with such switch during the drive then consequences can be very bad. the above switches are safe of course.
 
#16 ·
Samosali,

That type of switch is an LVD (low voltage disconnect). They typically don't supply large amounts of current (5-20 amps).

It's quite often used in the boating world to feed bilge pumps. You wouldn't want your battery to die because of water pouring into your boat that the bilge pump is trying to remove! Actually, it's used there because many inverter/chargers are auto-sensing between 12 and 24v. If your bilge pump were to draw down the batteries enough, the inverter/charger does not know which management regime to initiate, so it just shuts down. What is desired is that the bilge pump is turned off for a bit (because of low battery voltage), then the inverter/charger can bring the batteries back up, and the bilge pump turns on. Hopefully in the interval the boat doesn't sink.

While consumer grade LVDs are really expensive, most good solar charge controllers come with them. So I use them on my boats to manage the bilge pumps. It's critical to me, because my boats are on opposite sides of the globe, and are often unattended for a month or more at a time.

Cheers
 
#17 ·
yes i know, the current which such sophisticated switches handle is relatively low. thus one must make such switch on his own. but it is better to avoid it due to safety reasons. if the boat dies it can be dangerous but in most cases not. if car dies due to malfunction of such switch it can be always very dangerous.
 
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