cars..why/how dynos can vary day-to-day, how cars do indeed adapt to one's driving style, etc etc. For the nekulturni, Jim Conforti is considered the top ECU-tuning/modding guru for BMWs..name spoken with reverence and all that

ODB-II Adaption. Jim Conforti's explains adaption. Here's Jim's explanation, reposted from the BMW UUC Digest:

How does one properly dyno an OBD-II upgrade?

Simply.. as an owner.. you CAN'T...

Let me explain why (again ..

It's called adaption.. simply put, the Siemens boxes in the BMW 6 cylinder cars adapt under a much wider range than the previous OBD-I.. and worst off YOU can't clear the adaption..

See, previous to OBD-II, adaptive information was stored in battery backed SRAM. Unplug the DME to swap chips and woosh all adaptive factors set to "nominal" (1 for mult. and 0 for add.) Then came Kalifornia, and KARB, and OBD-II.. and EEPROM for storage.. this means you can't just "erase" it anymore because the last thing the DME does during shutdown is write the SRAM locations to EEPROM.. and guess what the first thing it does is.

Yup... zero SRAM, run a galpat memory check, and reload the needed ram locations from EEPROM.

The only way to clear the adaptive locations is via diagnostic commands down the serial port (even desoldering the main FLASH memory program store doesn't do it, because there is a separate EEPROM elsewhere)

So if you can't clear it.. you can't do an apples to apples comparison.

... since you can't clear it you can't get a valid comparison.. want to try something..

Take your car.. OBD-II.. chipped or stock.. drive it one week like a MADMAN and dyno it.. then drive it for another week very meekly.. and dyno it.. compare the results.. and they WILL NOT be anywhere NEAR the same.. and we didn't change the car at ALL..

Why?? (Prof. Shark asks the class)

Exactly.. the car ADAPTED to different areas of the maps and either enrichened or enleaned the overall mixture.

Now.. in whatever state the car is in, you can be rather assured that ON AVERAGE the chipped car is making significantly more power than the stock car.

Adaption works like this.. at lower loads and rpms it watches the AVERAGE correction (realize we swing rich and lean of stoichiometric continuously, except for WOT)... and it adds or subtracts a bit of fuel until the low speed fuel mixture is swinging evenly around Lambda = 1.0 / AFR 14.7:1..

Now as the rev range increases.. we switch to a multiplicative correction which adjusts (if you will) the SLOPE of the fuel curve by multiplying the STORED values by a factor (based on 1.00)

Depending upon how good the manufacturer tuned the low end and lower midrange, the environmental conditions, the fuel you are using, and the flavor of soda I have in my fridge (*grin*) .. well really what AREAS of that lower speed area you are in most of the time during the drive cycles.. that determines WHAT those two magic numbers will be.

The kicker.. and bummer.. is that even though lambda control isn't active, and adaption isn't HAPPENING at high throttle angles, those two numbers ARE STILL USED IN THE CALCULATION regardless as an "overall correction" to fueling.

So.. let's say that at 20% throttle and 3000 rpms the manufacturer is a bit rich.. the system adapts lean.. if you drove at very light load/throttle for a while at 3000.. you might see your peak HP drop 10HP on the dyno.. once the car adapts

Conversely, let's say the manufacturer is a bit lean at 2000 and 50% and you spend your week in LA traffic jams always gassing it in 4th and not downshifting.. car goes rich.. now you dyno your car and BOOM magic horsepower have appeared (well.. not really)

Simply put.. while any chip manufacturer can tell you that 90+% of the time your chipped car will have more HP than the stock one, unless you have cleared the adaption BOTH times when you run the cars you can't quantify it at all.

Jim

 

So this means, my wife, who drives the car most of the time, and drives like a little old lady, is making my car slow?

 

Yeah, but that doesn't mean you can't change that

 

Excellent article, Galo. Jim's comments are borne out in a test recently conducted in one of the major trade rags on a WRX that was wrung out in Montana and Colorado and then brought back down to earth in LA rush hour traffic. With no changes made in the vehicle, The OBD-II adaption Jim refers to resulted in a 20 hp DECREASE in the WRX.

 

Interesting

 

Would this explain why somedays the car runs good and other days it runs like crap???

 

I think so. When i was testing for the 1-2 shift problem and flooring it a lot my gas pedal felt really really really, did i say really yet?, touchy. Felt hella mean when i barely touched the go pedal.

 

It would also shed some light on the varying MPG we've see lately. as the 3.5 can use more gas it has a bigger swing than the 3.0... Guys (or gals) that are on the gas more in every day driving will get a much lower MPG than others.

Also I guess if you want that best time you've been looking for at the track you need to dog the car for a few days before you go.

 

drive pretty sedately 95% of the time..shifting at less than 3.5k, very, very infrequent blasts to >6k rpms...definitely gotta start pushing my car harder a bit more regularly...

 

So, if I am reading this correctly, if someone puts an intake on their car and drives it harder because of the sound and has it dyno'd the gains could be because of the computer adapting to the driving and not necessarily the mod itself? My mechanic has been telling me I'm wasting my time/money modding because of how the computer works, hope he isn't right.

 

little of both'.
Very likely the mod itself is worth something plus the harder driving would be worth something else....combine those two and you might get a situation where 1 + 1 = >2.

 

That's part of why it's so hard to reverse-eng our ECU. Almost every item has its own address and answers accordingly when info is requested. This info is then used by nissan's algorithm to determine based on this input values what should I be doing. And, we are still just talking about the generic OBD-II parameters. The nissan specific parameters are guarded better than military secrets.

It seems like an adaptive system that shouldn't need any modification, if you whole-heartedly trusted nissan engineers. The thing that is even more interesting is the fact that nissan took extra steps in making sure the chip manufacturer/part # were removed from many of the chips in the ECU and even the remote
Even part # on a simple transistor, paranoia or ????

Still searching for SAE documents
SAE J2178-1,2,3,4
SAE J2190
SAE J1850


SHIFT_woosh

 

So this leads to the question...How much 'adaptation' do the engineers design for? It'd be nice, if they simply used an equation instead of set tables or algorithyms. So, can you safely run a turbo or supercharger without aftermarket controls? Where is the limit?

 

And now I have been driving my car very fast around town....