What AFPR Set Pressure for 19lb Injectors?

[nando]

Motronic goes to open loop at wot so you can run an o2 and it will tune ratios other than 14:7 at wot. It wont at part throttle because motronic runs closed loop at all other times except cold start.

Lomg term fuel trims still affect WOT.

Short term fuel trims are used in closed loop only.

[mpowerful]

Yes to some degree, but the age old question is how much do long term fuel trims effect the map? I still have not seen a consensus answer on that.

[nando]

enough to be significant. typically fuel trims max out at 25% in each direction.

I don't remember what the Bosch documentation says about Motronic 1.x but it's probably 25%.

[mpowerful]

If that is the case then why do all the tunes bother changing the fuel tables at all? Thats not a smartass remark im genuinely interested in why tuning the fuel tables or scaling the injectors makes a difference when there is plenty enough correction to overcome bigger injectors? For start fuel? To center the maps for more adjustability?

[nando]

because under initial startup it can be so far off that the engine never runs right. who would want to sell a chip with their name on it that ran like shit for the first 100 miles?

also it's not a good idea to take up most or all of the adaptation value because you don't leave enough for actual engine variation and wear.

finally the stock fuel maps are made to run much leaner than what makes the best power. just look at all the tricks the SpecE30 guys have to do to keep their motors from running lean.

[mpowerful]

Yeah ive seen. Ive evaluated a lot of tunes to and now am pushing my own. Even some performance tunes ive seen are pretty damn lean. Anyway. Cest la vie.

[digger]

it may not adapt to suitable AFR for performance. you can do a custom chip and disconnect the O2 sensor and it runs fine

[squidmaster]

^ Or the correct chip and leave the o2 plugged in. From my experience fuel trim doesn't go further than 20%. So 14.5# stock tune would only reach 17#, which is why many people don't retune for the m50 injectors, but why well-running 19# need a tune.

[jlevie]

In my experience, learned adaption does affect WOT operation. Simply changing the fuel map data with a stock DME doesn't seem to affect that. You'd have to change the basic programing of the DME. To avoid that problem (and other issues) in my Spec E30 I have the DME power on a relay that turns off when the ignition is switched off. The car sees little time in closed loop mode, so learned adaption is not a problem since the DME is reset for every start.

[digger]

^ Or the correct chip and leave the o2 plugged in. From my experience fuel trim doesn't go further than 20%. So 14.5# stock tune would only reach 17#, which is why many people don't retune for the m50 injectors, but why well-running 19# need a tune.

the adaptions do affect WOT but its not in real control by the user. you would assume that the % you need to back of the injector PW at part throttle would be the same at WOT. I look at it the long term corrections are on average correct but averaging a whole bunch of data and using it at WOT is not the best solution all the time.

you dont need an O2 sensor unless you are worried about emmisions and catalytic converter functionality. running at 14.7:1 is rarely best for power or economy, slightly rich and lean respectively is better more often than not.

[squidmaster]

Which is why I'm saying that you need the correct tune for the injectors. The value that's given from the ecu to control fueling is just a control for the pump. Higher value, higher voltage, higher flow.

[digger]

Which is why I'm saying that you need the correct tune for the injectors. The value that's given from the ecu to control fueling is just a control for the pump. Higher value, higher voltage, higher flow.

lol not sure about that you might want to do some more reading.....for a given rail pressure (which is relative to manifold pressure) the fuel flow is dependant how long the injectors are open for

[nando]

the adaptions do affect WOT but its not in real control by the user. you would assume that the % you need to back of the injector PW at part throttle would be the same at WOT. I look at it the long term corrections are on average correct but averaging a whole bunch of data and using it at WOT is not the best solution all the time.

you dont need an O2 sensor unless you are worried about emmisions and catalytic converter functionality. running at 14.7:1 is rarely best for power or economy, slightly rich and lean respectively is better more often than not.

yeah, I don't agree. every car these days uses an O2 sensor as an important feedback loop. It's the only way the DME has any clue if it's giving the right amount of fuel to the engine. the O2 sensor that really only affects emissions is the post-cat sensor.

also, if your base fuel map is close to what it should be to begin with, you shouldn't need much of a fuel trim anyway, just enough to keep things on target as the engine ages. even the part throttle fuel map isn't necessarily just straight 1.0 lambda..

about % corrections. I ran 19# injectors on a stock chip for years without issue, but everything was working correctly. if the DME isn't properly metering air and getting accurate O2 feedback in the first place, then you could be so far out on your fuel adaptations to begin with that there's nothing left for the injector size change.

[squidmaster]

lol not sure about that you might want to do some more reading.....for a given rail pressure (which is relative to manifold pressure) the fuel flow is dependant how long the injectors are open for

Actually... there are many different ways that fueling is controlled through the ECU. AFM scaling, PWM for injector solenoid, injector latency, and dead time are all completely independent of each other. When 99% of people tune the motronic ECUs, the major (if not only) value that's being changed is the PWM to control injector open time. Since there's no way for a value on the chip to magically generate a pulse width, it needs to be converted. After-all, you can't feed the injector a range of voltages and still have the solenoid work properly. Instead, what ends up happening is that the injectors receive a converted pulse width modulation at a regulated voltage, and that is what controls the injectors' solenoids. Higher value, higher voltage, (longer pulse width,) higher flow.

about % corrections. I ran 19# injectors on a stock chip for years without issue, but everything was working correctly. if the DME isn't properly metering air and getting accurate O2 feedback in the first place, then you could be so far out on your fuel adaptations to begin with that there's nothing left for the injector size change.

I've seen you talk about this before, but I never noticed if you had given any readings or data to support that the car was performing within an ideal range. Because if I were to go out to my car right now (with 19#), load the original map into it, enable o2 feedback, and just wait, my idle AFR would go from about 16 to between 13 and 14. While the car may still idle at that AFR, it won't be very smooth and just ends up wasting gas. When I start to drive, my cruising AFRs change from 15.5-16 to 12.7-13.5 after a while of learning the trim. And while I may still be able to drive the car with that, again, a waste of fuel and it just won't run as well. Going into WOT you might start seeing numbers in the 10s or 11s or 12s; for an NA car that is hardly ideal. So that's why I would like to see what you have experienced with the injectors on a stock computer and stock chip. There has to be some reason why they apparently work great for you and a couple of other people, while everyone else finds them hurtful on stock tunes.

[mpowerful]

Which is why I'm saying that you need the correct tune for the injectors. The value that's given from the ecu to control fueling is just a control for the pump. Higher value, higher voltage, higher flow.

Despite all that stuff you just said in the previous post the fact of the matter is still that you are dead wrong about this. There is no such thing as pump pressure changing in motronic. Perhaps you have been working on some returnless systems?

I've seen you talk about this before, but I never noticed if you had given any readings or data to support that the car was performing within an ideal range. Because if I were to go out to my car right now (with 19#), load the original map into it, enable o2 feedback, and just wait, my idle AFR would go from about 16 to between 13 and 14. While the car may still idle at that AFR, it won't be very smooth and just ends up wasting gas. When I start to drive, my cruising AFRs change from 15.5-16 to 12.7-13.5 after a while of learning the trim. And while I may still be able to drive the car with that, again, a waste of fuel and it just won't run as well. Going into WOT you might start seeing numbers in the 10s or 11s or 12s; for an NA car that is hardly ideal. So that's why I would like to see what you have experienced with the injectors on a stock computer and stock chip. There has to be some reason why they apparently work great for you and a couple of other people, while everyone else finds them hurtful on stock tunes.

I ran 17lbers on a tune meant for stock injector sizes. I will agree that in the short term it is definitely rich, but over time the there was enough adaptation for it to be adequate. I have not tried this long enough with 19lbers to know but I would assume that if the dme corrects to 25% that it could work in the long term but the fuel trim over the long term would be adjusted to max. I know one thing, they are very rich on stock injector size tune in the short term.