Motronic adapt time?

[packratbimmer]

Checking to see what folks have read/encountered/experienced about the time it takes for the Motronic system to adapt after losing electrical power.

Is it a matter of run cycles, time running or???

I am thinking about setting up two ECUs for my 1989 M20 325i - one for 87 octane and fuel economy and one for 91 or 93 with higher performance in mind.

Lets just say I want to do some aggressive driving on the weekend. Would I need to switch out brains a few days in advance?

Thanks

[whitebulat22]

My battery on my 2.7i used to run down constantly before I found the trunk light staying on. It actually ran flawlessly immediately after starting on stock software even with M50 injectors too, and never hesitated any time it got reset. I tried to let it learn an M30 afm, failed, and tried to let it learn again with a M30 afm tune. It would get a bit less bad after 10 minutes but it never got anywhere near where it needed to be. So it should be close to bang on immediately or else it won't get there IMO.

I also did a dyno run with a normal 2.7i tune, then swapped out for the stock tune. The difference was 9 whp but the stock tune didn't give any issues and put out similar AFRs to the tuned computer, both were always near stoichiometric.

I personally just leave the 91/93 tune in at all times with the stock as purely backup, because the extra $2 or so every fill up isn't a big deal and you may even get a little mpg to help offset that if you're driving it the same way.

[DesertBMW]

Motronic 1.0 to 1.3 does not have any significant adaption stored in the memory.
The adaptation is only to enforce the target air/fuel ratio during part throttle driving, which varies based on conditions.

You can install switchable eeprom inside the ECU and with just a regular toggle switch you can switch between 87oct tune and 91oct. This is old news.

[packratbimmer]

Thanks guys! Just what I needed to know.

The whole issue just came up for me because Maine Sunoco stations just started getting 93 octane. Most stations only have 91.

I have always done minor tuning for 93 octane (mainly M10 cars) but have recently entertained the thought of running 87 in my 8.8:1 M20 since the difference in price between the two grades (87 and 93) is up to 50 cents and up here. Translates to 3 gallons or so extra per tank.

My car is completely stock except for M50 injectors and I'm just wanting to play around and see what kind of economy I can pull out of the car.

Not sure if the 8.8 and a 93 octane tune would pull the efficiency from that fuel (93) as opposed to a higher compression engine.

[jeffnhiscars]

You don't actually tune to octane rather you change octane to accommodate your tune and even that may not be necessary. All grades of gas have the same energy content. Octane just prevents pre ignition based on how you change your timing and of course compression since higher compression creates more heat (think diesel which is "compression ignition") which makes the fuel want to ignite before its time...hence you increase octane.


Our stock ETA has an SSSquid and runs on 87. My Cabrio also has an SSSquid and 19s and it runs fine on 89 and probably just as well on 87.

FYI a stock chip can adapt to 17s...19 is a stretch. If you engine is unmodified a) you don't need 50s and b) without a chip you are going to have afr issues

[packratbimmer]

Not talking about an engine build - talking about two distinct tunes for two different fuels on bone stock hardware. I have a lot of experience driving with Sunoco 93 and a Turner 93 chip.

BMW already built the 8.8:1 2.5 to run on 87 octane. So far I have had no detonation or preignition. The combustion chamber/piston design is correct from the factory.

I would like to tune "for the use of 87 octane"

Looking into the SSSquid economy chip and trying to reason it through.

[packratbimmer]

The reason I am using M50 injectors is because they are newer, more readily available and a better design.

I agree that 19# injectors are way to rich on a stock chip and suspect that the M50s are on the edge of being too rich.

Glad to hear about good experiences with SSSquid. I dig the way they custom tune to the variables we throw out there to them. Have not tried one yet - waiting to see what kind of MPG I'm getting with the 87 octane and the stock configuration.

[jeffnhiscars]

Unless I'm missing something here if your car is "..completely stock except for M50 injectors.." You are flushing money down the toilet by using anything other than 87

[packratbimmer]

I'm open minded, but..

Well, I clearly had a LOOOOOOT more power with 93 and my Turner 93 chip 12 years ago when I got it. I mean- my grandpa would have been talking about striped ass apes. LOL

Are you saying a car running 87 with a chip tuned for 87 will be as fast as a car running 93 with a chip tuned for 93?

[jeffnhiscars]

I'm not the most knowledgable person here on this subject BUT I'll say it anyway....you do not tune to an octane...you run the octane your tune demands. Ie..the more advanced your timing the higher the likelihood of knocking for which you want to increase your octane.

I ran 93 for years on a stock tune cause I thought I was supposed to. Switched to 87 and it made zero difference...except to my wallet.

Then chipped my b25 and was advised to use 93. 91 works fine and I suspect 87 wouldn't be an issue but I don't use it. Same as with wine...I prefer 90 points and over :)

Again, all pump gas has the same amount of energy. The only diffence is the anti-knock additive. If it doesn't knock you can drop down a grade and try that. If your car is stock run 87. If it's not stock follow your tuners advice.

[digger]

stick to 91 at most, 93 is a waste on a stock m20 chipped or not, one of the e30 racers around here said on the dyno 93 PON makes less power than 91 equivalent.

[packratbimmer]

Good to know - Sounds like 91 is the magic # for the performance tune on a stock 2.5 US M20. My turner chip came with a car so it might be a 91 for all I know. I always ran 93 out of habit after driving tweaked out high compression M10 cars for about 15 years before I converted the fleet over to M20.

SSSquid only charges $150 for the eco tune chip, so I'm just going to wing it and try the eco chip for 87 octane and see how it goes