Author Topic: Will The Stock ECU Adapt to ITB's? (Read 15927 times)

16v of Fury · « **on:** July 21, 2007, 12:47:48 PM »

If you were to just mount a set of ITB's in place (say, a Dbilas kit) and try to fire it up, would the stock ECU adapt over time to the ITB's...?

Or do you REALLY have to go the extent of starting from scratch with Megasquirt... ?

bmwman91 · « **Reply #1 on:** July 21, 2007, 05:56:37 PM »

Nope, won't work. The only adapting it does is through the O2 sensor input, and that only has an effect on fueling via the Long Term Fuel Trim (which is basically a scaling factor that effects all fuel bins). The E36 one had knock sensors which can cause changes in the ignition timing, but the car will never tune itself for performance so to speak. Sorry to bring bad news, but custom software or a stand-alone is needed here.

16v of Fury · « **Reply #2 on:** July 21, 2007, 06:50:03 PM »

Where can I get a custom chip made for ITB's, any idea?

DutchM42 · « **Reply #3 on:** July 22, 2007, 07:08:49 AM »

Rolling-road only.

16v of Fury · « **Reply #4 on:** July 22, 2007, 10:15:34 AM »

Anyone know a good place in NY to do that?

dino245 · « **Reply #5 on:** July 23, 2007, 09:55:24 AM »

The stock ECU does not have the resolution or speed to calculate the required fuel for a set of ITB's. I am doing a set and switched to a Haltech for the added flexability and control to run ITB's. Dont waist your time, do it right or dont bother you will just get frustrated.

Boyracer · « **Reply #6 on:** July 23, 2007, 04:34:27 PM »

Quote from: dino245;30157

The stock ECU does not have the resolution or speed to calculate the required fuel for a set of ITB's. I am doing a set and switched to a Haltech for the added flexability and control to run ITB's. Dont waist your time, do it right or dont bother you will just get frustrated.

Can you elaborate about the resolution and speed issue? What is actually the issue?

I would think ITB's would be a problem if they are bike type ie. they let lots of air in with just small throttle opening. Then the change might be too sudden compared to number of bins available.

But M3's with ITB ran with a Motronic too. Maybe they had more bins etc. But what I have learned, ITB's should not be a problem with Motronic, provided that it is properly programmed (custom chip). But I'm happy to learn more about this

bmwman91 · « **Reply #7 on:** July 23, 2007, 05:02:32 PM »

The issue is not even so much about the number of bins and response time of the Motronic. The issue is more in the control algorithm. The "learning" that the Motronic does is pretty rudimentary. It does not modify its ignition timing maps (which is very much necessary when making major physical changes), and the fueling changes are ONLY applicable in 2 cases:
1) When in closed-loop running mode (when thrittle is less than ~85% I believe and/or under 4000RPM). This is known as the short-term fuel trim. It is the instantaneous fueling correction applied via O2 sensor feedback, and will only target an stoichiometric AFR since that is the ONLY thing our stock O2 sensor can do accurately.
2) It can apply a general scaling factor to fueling (a single constant scaling factor over the whole range of bins, not a one that varies with respect to anything other than the present fuel injection rate). This is known as long-term fuel trim. It comes from some basic "learning" based upon long-term trends in the O2 sensor input versus the initial bin settings. It takes at least a couple hours of driving to get set from my experience.

So, neither of these Motronic functions can account for something like an ITB setup. Even if the fuel could somehow be done properly by adaptation, the ignition timing would still be way off. Even in the E36 the ignition timing would not be right, regardless of the knock sensors. The knock sensors were more for protection against crappy gas being used on the relatively high compression M42. The Motronic there starts with base ignition timing values, and will only retard them when knock is sensed. It will not keep pushing them to extremes and use the sensors to tune for performance...the ignition will only get retarded by them.

So there! I guess that would be the full explanation. My recommendation is to go stand-alone. Megasquirt, or Motec or Haltech systems. The latter 2 are $$$ comparatively though. Either way, expect to spend a good year messing with it and a TON of $ tuning it. Also, shave your head first and spare yourself the pain of pulling all your hair out lol.

JK it is not THAT bad. Well, maybe it is.

MarkD · « **Reply #8 on:** July 23, 2007, 05:38:12 PM »

Quote from: dino245;30157

The stock ECU does not have the resolution or speed to calculate the required fuel for a set of ITB's. I am doing a set and switched to a Haltech for the added flexability and control to run ITB's. Dont waist your time, do it right or dont bother you will just get frustrated.

:confused: :rolleyes:

I don't see any reason that you can't use ITB's on this motor and tune the Motronic to run it. The s14's and s38's use a similar cpu and they run a Motronic. Build an airbox to feed the ITB's, put an AFM or MAF ahead of it.

If you were in Canada, I'd tune it for you.

16v of Fury · « **Reply #9 on:** July 23, 2007, 09:33:40 PM »

I'm talking about a set of the Dbilas ITB's --- they already have an airbox and are a "bolt-on" item.

Do you have an M42 there in Canada to play with, Mark... ?

bmwman91 · « **Reply #10 on:** July 23, 2007, 09:39:36 PM »

Quote from: MarkD;30188

:confused: :rolleyes:

I don't see any reason that you can't use ITB's on this motor and tune the Motronic to run it. The s14's and s38's use a similar cpu and they run a Motronic. Build an airbox to feed the ITB's, put an AFM or MAF ahead of it.

If you were in Canada, I'd tune it for you.

Tuning the Motronic is a black art that precious few people have managed to figure out. I sure as hell have not (though I suppose a year or 2 of decompiling & studying everything might help). I would venture to guess that having the Motronic chip tuned would run someone as much as a proper stand-alone. Doing it with the Motronic is sweet because you can forget about rewiring things and keep it all OEM-ish. The stand-alone is beneficial because you can tweak whatever you want yourself. Pick your poison, I suppose.

Off-Topic:
Mark, how did you go about finding the maps & checksums in there? I have EPROM dumps, but since all the program code is on there as well as the maps it is like finding a needle in a haystack (for someone like me who does not quite know what the data stacks look like in there). Care to give some general pointers about the way the maps are laid out? I HEAR that the first byte is the output variable, the next is the number of bins/columns per row, then the x-axis input variable, Y-Axis # of rows, Y-axis variable, and then the values. Something like the last data value is representative of the highest RPM (for instance) and each one before it is an offset that is subtracted? I understand the need for protecting your own hard work, so no hard feelings if you prefer to keep it under wraps. I hear that the competition in the chip tuning world is insanely fierce.

One other question for ya...I am guessing you have done more than just reverse engineer the map portions. Since you have mentioned MAF conversions, I would imagine you have rewritten the program code to disregard the IAT thermistor and just take in the MAF voltage and skip the conversion from volume flow to mass flow rate (mmmm, direct load input without additional math)? As much as I have done my share of microcontroller programming, wading through the like 32K of instructions must have been a nightmare! Kudos to you!

Boyracer · « **Reply #11 on:** July 24, 2007, 05:46:19 AM »

Quote from: bmwman91;30184

So there! I guess that would be the full explanation. My recommendation is to go stand-alone. Megasquirt, or Motec or Haltech systems. The latter 2 are $$$ comparatively though. Either way, expect to spend a good year messing with it and a TON of $ tuning it. Also, shave your head first and spare yourself the pain of pulling all your hair out lol.

Yeah, I was not expecting Motronic to fully learn to run with ITB's by itself but I could not to see any reason why it could not be programmed to work with them in M3 stylee

Anyways, long and short term trim explanations were new for me... I thought Motronic would trim fueling on bin basis. Thank you for the explanation! :eek:

My current plan is to take the car on rolling road where new custom chip is created. Price is around 70� / hour and provided that there is no need for performing engine adjustments it should be few hour job.

Plus side for custom chipping motronic is keeping the OEM feel I like, which I think might be even required to pass finnish inspections (you cannot change ECU or it is compared to engine swap). Also, no hassle with cabling.

Aftermarket ECU would allow tuning by miself after modifications... And Alpha-N would be easy to implement

bmwman91 · « **Reply #12 on:** July 24, 2007, 10:31:43 AM »

Quote from: Boyracer;30255

Yeah, I was not expecting Motronic to fully learn to run with ITB's by itself but I could not to see any reason why it could not be programmed to work with them in M3 stylee

Anyways, long and short term trim explanations were new for me... I thought Motronic would trim fueling on bin basis. Thank you for the explanation! :eek:

My current plan is to take the car on rolling road where new custom chip is created. Price is around 70� / hour and provided that there is no need for performing engine adjustments it should be few hour job.

Plus side for custom chipping motronic is keeping the OEM feel I like, which I think might be even required to pass finnish inspections (you cannot change ECU or it is compared to engine swap). Also, no hassle with cabling.

Aftermarket ECU would allow tuning by miself after modifications... And Alpha-N would be easy to implement

Glad the explanation helped. Now, this is based off of some first hand observations and a Bosch fuel injection handbook, so Mark should let me know if I am incorrect lol. :p

Hopefully the expert you are with can do it that quickly. Getting the ignition timing AND fueling set properly is no easy task. They are sorta inter-related. You might get the fueling set ideally with the ignition not quite ideal, then when you adjust the ignition more to where you want it, the fuel maps will no longer be ideal, adjust those, then need to adjust ignition again, and so on. From what I have experienced, it is an iterative process. An expert should be able to get it running smoothly in a couple hours, but getting the maximum power out of it will cost you a lot of money. I think the usual cost is said to be ~$1000US (~725�) in tuning for a fully-custom chip.

I completely agree with you about the benefits of keeping things as stock as possible (minus the ITB's of course!). The Motronic is a very robust platform, and if you can work with it then life will be much easier. You get to keep the fault diagnostics, the gauge control and all the stock sensors (or new ones if you want to change those bins as well).

nuvolarossa · « **Reply #13 on:** July 24, 2007, 04:16:25 PM »

bmwman91, do you have the original map of your 318is motronic? maybe I can have some info about locations for timing maps and fueling of oem motronic and can help this forum a bit...

bmwman91 · « **Reply #14 on:** July 24, 2007, 08:37:05 PM »

As it turns out, I DO. It is online even, in a .TXT file with the data in HEX format. I tried using a demo of WinOLS and it did not help me TOO mcuh, but I was also too busy at work to dedicate much time to it lol.

Anyway, here it is:
http://www.e30tuner.com/M42Bins/M42STHEX.TXT

Author Topic: Will The Stock ECU Adapt to ITB's? (Read 15927 times)

16v of Fury

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