evovette

iTrader: (3)

I have been fighting my fuel trims for a bit and was wondering what would be a better idea. 1) rescale my injectors (stock) and adjusting latency or 2) going into my fuel maps and adjusting it there, or 3) a combination of both

AlwaysinBoost

iTrader: (17)

what are your trims at?

evovette

iTrader: (3)

+12% idle(low) and +10% cruise(mid) after 600 miles of driving. These are the LTFT values

AlwaysinBoost

iTrader: (17)

are you running an aftermarket MAF pipe?

elhalisf

iTrader: (171)

well now, we believe we have discovered the closed loop maps.
https://www.evolutionm.net/forums/sh...d.php?t=233744
i found them in my ecu

so you should adjust the high octane fuel map (for open loop, cold start up) and the closed loop fuel maps.

but there might be something else causing it to be rich with stock injectors. my friend is battling a problem where it is so lean during idle.

evovette

iTrader: (3)

im running an HKS RS intake but have my ECU+ set to 42 hz to try and combat its negative effects. I may swap in the stock intake and see what happens.

AlwaysinBoost

iTrader: (17)

is your breather hose coming from the valve cover hooked up to the intake?

MalibuJack

iTrader: (5)

That clearly means your car is running leaner than it was before.. Definitely swap the Stock Intake back on, and see if the trims even out a bit..


Most aftermarket intakes "lean out" the entire airflow curve, some are even more quirky about it and can even be unpredictable and inconsistent about how much at any one time..

HOWEVER, you also should check for vacuum leaks, or any source that unmetered air can bypass your MAF, since that will also result in the trims being like that too..

THe issue is probably something you can handle by checking over everything, therefore don't try to "tune around it" with injector scaling or anything reflash related until your 100% certain you don't have an alternative.

Every modification you make to your car that changes its volumetric efficiency will result in tthrowing your trims off slightly so keep that in mind.

Idling at 43hz would result in more fuel at idle (if your running open loop) therefore your trims would result in removing fuel.. THEREFORE if your running +13 or so adding fuel, that would likely mean your trims might be even more screwy at the stock idle frequency of about 32hz.. This is highly likely that its the Intake, but again, check for unmetered air since its also a pretty common thing.

evovette

iTrader: (3)

yes it is. Ibelieve that RS intake really f's with the MAF reading at idle. Im sure my 264/272 cam combo doesnt help either

MalibuJack

iTrader: (5)

Closed loop maps are not the solution for fixing trims.. Trims are the difference between the open loop maps, and the closed loop AFR Target (14.7).. The more the open loop map is off, the greater the fuel trim difference will be.

Altering the closed loop maps are generally not useful, their only of value if you need to get the closed loop fueling to run richer or leaner for a particular purpose.

If your car runs lean in closed loop, and you never touched those settings, it means that the open loop fuel map value, is so lean, that the fuel trims don't have the range to adjust it to 14.7 (closed loop AFR reference) And therefore you need to make adjustments to the open loop maps in the problem areas so the "Closed loop fuel targets" don't have to work as hard..

By doing this, you will also eliminate cold start problems where your AFR's may be very lean until the car gets into closed loop..

MalibuJack

iTrader: (5)

The easiest way to fix this is to force the car to run in open loop (disconnect the front O2 sensor) and drive the car and log the data, by doing that, your load calculations will be fairly accurate, and your AFR's will register what the open loop maps are doing, it should allow you to very easily pinpoint your problem areas, spend the time to get the open loop problem areas back to 14.7 (or whatever your target AFR might be if you altered the closed loop table), and you'll get fuel trims that are pretty spot on most of the time when you reconnect the O2 sensor.

evovette

iTrader: (3)

Ill try that Jack. Problem is that I have tried to lower the open loop values from 14.7 to 13.9 and they didnt seem to alter my trims at all. (1000rpm-3000rpm:loads 20-50) I will disconnect my 02 sensor and go for a ride and see where I am at. That should tell me the story better. Thanks to all that helped.

l2r99gst

iTrader: (2)

Jack,

I am curious as to where you obtained the above information? I haven't diassembled the Evo ROM any yet, but I think the trims work the same as in the DSM ECU. If so, the open loop maps have no bearing on the closed loop fueling at all.

Closed-loop is controlled entirely by O2 sensor feedback to maintain a stoich burn. For example, changing the open loop maps in the idle cells, like EvoVette mentioned, will have absolutely no effect on closed-loop idle. The only time it will have effect is when idle is in open-loop, like during warm up or other special circumstances where the ECU may default to open-loop.

The place that fuel trims will affect open-loop fueling is during the transitions from closed-loop to open-loop. For example, if you have very positive trims, then your transition to open-loop would have a lean spike (if you didn't tune it out), since this trim isn't applied anymore ,and vice versa.

I'm not saying that you are wrong...maybe I just don't understand what you are trying to explain.


Eric

MalibuJack

iTrader: (5)

Of course it doesnt have any affect on closed loop idle, those are the job of closed loop targets..

Open loop tables are the "base tune" fuel trims are the adjustment to reach the closed loop target.. The CLOSER your base tune (open loop map) is to your target, the less adjustment is needed to hit your closed loop target.. This applies to Any closed loop system..

This is the single reason why fuel trims go out of range, the base tune has changed enough so that the closed loop targets can no longer adjust then your trims end up +/- 25% and the ECU can no longer adjust automatically.. By adjusting the open loop maps, you set up a baseline that is roughly correct so the ECU doesnt have to constantly re-adjust trims every time the ECU is reset..

I'm trying to think of a good analogy, but I'm finding it difficult to think of one... Okay, here's an example.. Okay, think of the fuel control as a glass of water.. Closed loop fueling is the faucet filling it to 3/4... If the glass is always empty The faucet always has to fill the glass.. Your open loop fuel maps are kinda like filling the glass almost to 3/4, so the faucet only has to fill it a small amount.. The faucet is a bad example because you have an unlimited source of water.. But assume that this faucet can only add or remove 1/4 glass of water.. No more or no less.. If the glass is empty, no matter what you do, you'll never be able to fill it to 3/4.. Understand?

MalibuJack

iTrader: (5)

Oh, and this is the logical basis of every closed loop control system.. There are some that can learn from the ground up with no information, but it takes less time for the systems to learn if you give them a baseline..

Most automotive ECU's aren't capable of being completely closed loops, so they have base maps.. You always have some sort of baseline to work from because it takes less time for the car to re-learn if you give it a starting point thats close to where it needs to be.