Are fuel trims stored?

Will durametric be able to read them with engine off? It would be nice to check them after a drive. I had a brief check engine light a while back and now it's gone. Seems good otherwise. RKAT and FRA...

Yes fuel trim adjustments are cumulative and saved so that the engine is already "self tuned" for the next drive cycle... They are only lost after clearing certain fault codes or if the battery is disconnected..

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Thank you. Is it accurate to get them after turning the engine off, are they something that can be downloaded after a drive? many of the engine related variables need to be with engine running but I'm not sure about these. And it would be nice to know how long after an adjustment or change it takes to register the new adaptation. Do they represent the last 15 seconds, 15 minutes, or 15 days? it would be nice if you didn't have to disconnect your battery every time you wanted to see if there had been a change.

Yes you can get them with engine off....Yes it is accurate, yes you can download them.. Some adjust fast some adjust slow,....if you change fuel injectors " oxygen sensing" will adjust first, then the TRA will adjust the mixture near idle and the FRA will adjust under load... Lordy, sounds like you want to learn how the whole system works....I could write pages and pages on it, and books have been devoted to it, but here is a 20 min video from Tony that probably got what you want.....If there is something specific you want to know or problem that's not covered I can help.. You Tube

Cool. Yes that's nice. Especially the last 4 or 5 minutes. Thanks. This is interesting. He mentions that removing the oil cap will affect trims, of course, and it will show. it is a big air leak. Other things can happen to change trims also, maybe I reattach hoses or change injectors. so here is my question and not answered in his video but does that mean I need to clear my codes or do a battery disconnect to get accurate trims or how long until it will it be corrected? Not looking for an exact answer just kind of a rough estimate , 15 seconds, 15 minutes, 15 days??

If a big change is needed near idle is will happen within a few minutes >5 min...under load within > 15 min..... Small changes can happen up to 100 miles before the system is fully "adapted".....of course this dependant on if there is any varying leaks or varying fuel pressure ect..... If there is a " intermittent leak or intermittent fuel delivery" the system will constantly adjust to different values are NEVER fully adapt to a constant fuel trim value..

Yes, that's great. Knowing that kind of time frame means you can make a change or adjustment and then expect to see results, not immediately, but after a reasonably short drive. I assume that an error recorded such as mentioned in the video when removing the oil cap with engine running would no longer affect fuel trim numbers after 15 or 20 minutes. in addition , you don't need to have the durametric software running while you drive or even running at all to sample the near idle and upper RPM fuel trims. I will do it at my convenience when I get home or even the next day. In my case, my rkat values came back high, which suggested an air leak. I tightened the connections I could access and then ran a couple smoke tests with two different smokers through the throttle body which was propped open. I didn't identify a leak at that point and my Rkat values are improved, so I will check them some more.

Yea, since it is so common on the m96 to have air/vacuum leaks, and so many people have problems finding them, even with a smoke detector.. I had thought about designing a method to test using a little Freon injected into the sealed engine and use a Freon leak detector to find the leak...( freon detectors are so sensitive it will find even the smallest leak).. But honestly I have been so bussey building UAOS's I just don't have time... each UAOS kit requires a few hours of hand made parts, hoses, mods,assembly ect....

Air leaks would be more of an RKAT, looks like normal should be zero? Above zero, think air leak. Is it true then, that higher than normal FRA, which should be 1, would indicate the DME is trying to increase fuel because it thinks the engine is running lean? since FRA is at higher RPMs an air leak should be less of an influence and alternatively maybe there is fuel starvation causing it to be lean. is that correct? Does a Bentley manual have troubleshooting information for fuel trims? Does a Porsche Workshop manual?

Yes, air/vacuum leaks show up on RKAT/TRA values and fuel delivery issues show up on FRA values... Right FRA over 1 means the DME is adding fuel to compensate for lean condition... No, Porsche or Bentley don't have troubleshooting of fuel trims other than if a code is set, then there are " trouble shooting tree's " ......or to describe how the system functions....all the "real" troubleshooting is done in the human brain...

The engine must be running to retrieve the codes... I just do a screen shoot... I was fortunate to get a good deal on my car(996.2) because nobody could get it smog'd. (California) All the techs kept telling PO to drive it more. Had a vacuum leak. It was smoke tested 3 times... My preferred method is a can of carp cleaner at idle...

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All the testers I have used, PIWIS ,Durametric, Torque Pro, all will pull codes key on/ engine off ....as well as key on / engine run ....YMMV

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Yes, there are many values that are saved and available with engine off. Fuel trim, like here, long-term fuel trim values, are stored for engine management so they can be read engine off. Other values need to be measured in real time with engine running. Where can I find instructions on how to use the durametric for a 996? I don't need help with how to use it, I want to find out how to USE it. Most of the information on how to use it are really just how to plug it in. There are plenty of instructions on how to turn it on and lots of posts by various folks recommending check this or that.

Jake's video is it start. It has some good information. Takes a long time to go through . Where is a list of Target values, acceptable ranges, and how to measure, for instance, for fuel trims?

Been looking around for reference values. Maybe I'm just not looking in the right places . Occasionally there's mention in a thread. Hard to believe there's not a list somewhere for normal values. Anyway, here's something I found. My car is 2000 so we have FRA, no FRAU or FRAO. Looks like FRA values need to be greater than 0.7 or less than 1.3.

Hi all, I found a list with DME setpoints a while ago, can share via private message. (I initially attached to this msg, but I am not sure if it is ok to post it on a public forum) My TRA has been slightly above 4 now for a while (like 4.02), but it does not lead to a fault code and car is running fine with a smooth idle. I figured my scanner is doing something wrong there (a relatively cheap one), because TRA is in ms and 4 would be way too much. (RKAT is giving a percentage) Nonetheless, I ordered a smoke test device because it kept bugging me :-) Best Wintermute

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Is this what you�re looking for?

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Yes, thank you. Looks like pretty tight range. RKAT should be -.1 minimum if you are running rich and +.1 maximum If you are lean. Is that right? Is it real world?

Well, can a PIWIS or a Durametric clear codes without wiping out fuel trims? My car is particular about it's fuel trims and I like it when my car is happy because it makes me happy. If they get reset we all suffer until they are restored. The first few starts are testy even though the steady state trims don't seem to be that wonky. So, with that in mind if either of those can clear codes while preserving fuel trims me and my car would like to know.

There isn�t a code reader available that will retain fuel trims after erasing codes on our cars, due to the limitations of our ECUs.

That's too bad because it seems like they should be stored in separate memory locations. It's possible that the offending issues have resolved or are within acceptable limits yet the error codes persist and a CEL remains.