Absolutely frustrated with this Mercruiser engine

[PlayDate]

Tom,

This is what I am reacting to:

Tom, @ttmott

Assuming the Fox Marine gateway is accurate.....the ECM is reporting timing at 30.34 degrees, Injector On Time 6.35ms and a fuel flow rate at 7.37 gallons per hour (which is a calculated number).

Then when you consider that the Throttle is at 99.61% and Manifold/Barometric pressures are almost equal......something is stopping the fuel from flowing when the throttle is wide open and the spark has advanced. The OP reports that it smells lean not rich which is another clue that there isn't enough fuel being provided to match the air supply. (It would be helpful to see a picture of the current spark plugs.)

Now ask yourself: Given the data above......what circumstances exist for an ECM not to increase the Injector On Time?

The OP addressed:
-the exhaust issue
-fuel quality
-fuel pressure
-had the injectors tested and serviced

Revving in neutral to 4000 rpm only required 2.7ms of Injector On Time which is not a lot of fuel. So the question remains: "Why is the Injector On Time not increasing?"

 

[Stee6043]

This thread has been fascinating to follow.

The OP is coming up on 2 years messing with this? Time to cashflow this boat by converting it to an AirBNB, then buy a different boat for actual boating

 

[ttmott]

Tom,

This is what I am reacting to:

Tom, @ttmott

Assuming the Fox Marine gateway is accurate.....the ECM is reporting timing at 30.34 degrees, Injector On Time 6.35ms and a fuel flow rate at 7.37 gallons per hour (which is a calculated number).

Then when you consider that the Throttle is at 99.61% and Manifold/Barometric pressures are almost equal......something is stopping the fuel from flowing when the throttle is wide open and the spark has advanced. The OP reports that it smells lean not rich which is another clue that there isn't enough fuel being provided to match the air supply. (It would be helpful to see a picture of the current spark plugs.)

Now ask yourself: Given the data above......what circumstances exist for an ECM not to increase the Injector On Time?

The OP addressed:
-the exhaust issue
-fuel quality
-fuel pressure
-had the injectors tested and serviced

Yes you are right - 99% throttle, 2000 RPM, 30.51 in Hg, and 6.35ms duty cycle makes no sense.
Looking at the manifold pressure validates the throttle position and available air. The calculated fuel flow rate also aligns with the injector duty cycle; but, that doesn't mean a lot.
I would think the spark advance would be closer to 35 degrees BTDC but for this it's incidental.
I'm now in the camp with you that there is a firmware fault (the fuel map is corrupted) with the ECM. These data as shown are not a result of some mechanical issue. A TPS of 99% with MAP at atmospheric, and low RPM should output more like 80ms injector duty cycle.

 

[douglee25]

Is the correct prop on the boat??

 

[Ericinmich]

...A TPS of 99% with MAP at atmospheric, and low RPM should output more like 80ms injector duty cycle.

Why do you suggest that the PW should be 80ms? Remember these are not sequential FE systems (ie. one driver per cylinder firing once per engine cycle (once per 2 revs)). These are ECUs with two drivers that could run TBI or MPI systems, basically what went into the 1990 L98 vette or trucks of that vintage. The injectors fire twice per engine revolution, four times per engine cycle. There is no way that they would have an 80ms injection time. One revolution is about 30ms, so 60ms per engine cycle... 80ms just wouldn't work.

I still think it's running on one bank and to prove it I'd start pulling injectors or one back of power to injectors or pulling spark plugs to see if the engine changes. Or force it into safe mode (on bank ie. driver) would shut off... plus that would verify the readout from the tool.

 

[ttmott]

Why do you suggest that the PW should be 80ms? Remember these are not sequential FE systems (ie. one driver per cylinder firing once per engine cycle (once per 2 revs)). These are ECUs with two drivers that could run TBI or MPI systems, basically what went into the 1990 L98 vette or trucks of that vintage. The injectors fire twice per engine revolution, four times per engine cycle. There is no way that they would have an 80ms injection time. One revolution is about 30ms, so 60ms per engine cycle... 80ms just wouldn't work.

I still think it's running on one bank and to prove it I'd start pulling injectors or one back of power to injectors or pulling spark plugs to see if the engine changes. Or force it into safe mode (on bank ie. driver) would shut off... plus that would verify the readout from the tool.

80 percent duty cycle is typical for OEM port injection at full load. Regardless a bit over 6ms at full load isn't right by any stretch of imagination.
Even if the entire injector electrical harness was removed the ECM will still set a duty cycle - the data shows a problem with the ECM.
My projects are all sequential but flow rate is flow rate and the duty cycle / injector size / fuel pressure sets that flow rate. The ECM fuel map is what sets the duty cycle.

 

[PlayDate]

80% according to my handy dandy fuel injection calculator for that engine would be Injector On about 13-15ms or more than twice what I see on that run.

I think it is time to see if all the injectors are firing at 2000 rpm.

 

[Ericinmich]

80 percent duty cycle is typical for OEM port injection at full load. Regardless a bit over 6ms at full load isn't right by any stretch of imagination.
Even if the entire injector electrical harness was removed the ECM will still set a duty cycle - the data shows a problem with the ECM.
My projects are all sequential but flow rate is flow rate and the duty cycle / injector size / fuel pressure sets that flow rate. The ECM fuel map is what sets the duty cycle.

6ms on the MEFI1 and systems of that design is 6ms twice per engine rotation, 4x per engine cycle, which is 24ms for each cyl. That would be about right at that RPM, that's about 50% duty cycle. That works out about right.

By port injection systems, do you mean sequential fuel systems? This engine is a port injection system, but there only 2 injectors in the ECU and in this application they fire 4 injectors twice per engine revolution. This worked well on systems before we had cam sensors... the engine didn't need to know which side of the cycle it was on. If you mean port injection systems that fire sequentially, once per engine cycle, then yes, 6ms wouldn't like be correct, unless it was a boosted system (not in boost) with huge injectors but then idling would be a bitch with such high flow injectors.

On GM the 1st sequetial systems were the LT5 vette in '90 (which I also did the SW for) then moving on to the LT1, and across the bord in mid-90s. Racing wise, the '89 Chevy-Ilmor was also a sequential FE system, the 1st for those engines... stop by the Indy museum and see the ECU with my SW in it!

 

[Ericinmich]

80% according to my handy dandy fuel injection calculator for that engine would be Injector On about 13-15ms or more than twice what I see on that run.

I think it is time to see if all the injectors are firing at 2000 rpm.

Along these lines, these ECUs were very easy to get a programmer for, easy to make your own cal, etc. And easy if you flip one config bit to totally screw things up.

 

[ttmott]

6ms on the MEFI1 and systems of that design is 6ms twice per engine rotation, 4x per engine cycle, which is 24ms for each cyl. That would be about right at that RPM, that's about 50% duty cycle. That works out about right.

By port injection systems, do you mean sequential fuel systems? This engine is a port injection system, but there only 2 injectors in the ECU and in this application they fire 4 injectors twice per engine revolution. This worked well on systems before we had cam sensors... the engine didn't need to know which side of the cycle it was on. If you mean port injection systems that fire sequentially, once per engine cycle, then yes, 6ms wouldn't like be correct, unless it was a boosted system (not in boost) with huge injectors but then idling would be a bitch with such high flow injectors.

On GM the 1st sequetial systems were the LT5 vette in '90 (which I also did the SW for) then moving on to the LT1, and across the bord in mid-90s. Racing wise, the '89 Chevy-Ilmor was also a sequential FE system, the 1st for those engines... stop by the Indy museum and see the ECU with my SW in it!

Still it is the cumulative mass flow rate per 720 degrees of crank rotation. It doesn't matter if you fire one injector or all at the same engine cycle. Fuel injectors are typically designed to operate between 1.5 to 90 percent duty cycle. Below 1.5 is idle stability problems and over 90 typically results in overheating the injector. At high load, which this engine is showing in the data, duty cycle should be very high.

 

[Ericinmich]

Still it is the cumulative mass flow rate per 720 degrees of crank rotation. It doesn't matter if you fire one injector or all at the same engine cycle. Fuel injectors are typically designed to operate between 1.5 to 90 percent duty cycle. Below 1.5 is idle stability problems and over 90 typically results in overheating the injector. At high load, which this engine is showing in the data, duty cycle should be very high.

Agreed, and 24ms is almost 50% duty cycle at that rpm, which isn't close to where the engine has highest volumetric efficiency... not likely it could be more than 50% with those injectors. If so, no way it would run to 4500 rpm where the amount of time would be less than half.

24ms of fuel likely is the right amount.

If you are interpreting the data as meaning each cylinder gets 6ms of fuel, this is incorrect.

 

[aerobat77]

I still think it's running on one bank and to prove it I'd start pulling injectors or one back of power to injectors or pulling spark plugs to see if the engine changes.

Should in this case the injector times not be around normal to avoid a lean condition and the power reduction occours just by running 4 cylinders firing and 4 cylinders acting as an airpump ?

Further : when switching off 4 cylinders in a crossplane V8 You SHOULD hear the difference when you make a V4 out of it - even when for sure not 4 cylinders on one bank shut off but two-two on both banks .

For me it somehow appears from the scan and the reports the engine still fires on all 8 but gets way to little fuel commanded for WOT .

Whatever : i,m with you to physically pull the injector or plug wires while running to verify if its true or false buts its easier to say than to do on a running boat.

Question : do you not force the engine into a power reduction mode when you pull plug or injector wires while underway and get so a false verification ?

However : If it indeed shuts 4 cylinders its imho a hidden sensor not reported in the scan , if it fires on all 8 its imho the ECM itself or the engine is mechanically not correct . Everything else was checked and verified.

 

[Ericinmich]

Should in this case the injector times not be around normal to avoid a lean condition and the power reduction occours just by running 4 cylinders firing and 4 cylinders acting as an airpump ?

Further : when switching off 4 cylinders in a crossplane V8 You SHOULD hear the difference when you make a V4 out of it - even when for sure not 4 cylinders on one bank shut off but two-two on both banks .

For me it somehow appears from the scan and the reports the engine still fires on all 8 but gets way to little fuel commanded for WOT .

Whatever : i,m with you to physically pull the injector or plug wires while running to verify if its true or false buts its easier to say than to do on a running boat.

Question : do you not force the engine into a power reduction mode when you pull plug or injector wires while underway and get so a false verification ?

However : If it indeed shuts 4 cylinders its imho a hidden sensor not reported in the scan , if it fires on all 8 its imho the ECM itself or the engine is mechanically not correct . Everything else was checked and verified.

Regarding a V8 running in half cyl mode, they run surprising well... just down about half on power! You can hear a different sound during the transition. As far as pulling a plug or injector, that will not force any power reduction mode.

This ECU is a version of the late 80s V8 controller, very simple, not much diagnostics, etc.

 

[ttmott]

The data shows the injector pulse width to be 6.35 ms. That means each and every injector is 6.35 ms.
Duty cycle is pulse width X RPM / 1200 so that would mean about 26% duty cycle for WOT at 2000 RPM. Not nearly enough for high load acceleration.

 

[JayhawkCurtis]

You guys are pretty impressive, if @Hoplite808 sticks with it, I have no doubt you guys will solve this issue

 

[PlayDate]

You guys are pretty impressive, if @Hoplite808 sticks with it, I have no doubt you guys will solve this issue

Get back to the Bikini Thread....your skills in that thread are a powerful motivation force.

 

[Ericinmich]

The data shows the injector pulse width to be 6.35 ms. That means each and every injector is 6.35 ms.
Duty cycle is pulse width X RPM / 1200 so that would mean about 26% duty cycle for WOT at 2000 RPM. Not nearly enough for high load acceleration.

I'll try this one more time, then give up.

MEFI1 has two injector drives and were used for both TBI (one or two injector systems) and PFI systems wired with each driver firing four injectors at the same time (V8s). Each driver could be configered to fire it's bank once or twice per engine revolution, we called it banked double fire. The "data" showing the injector pulse width as 6.35ms is how long the ECU would fire each injector twice per engine revolution.

If you put an O-scope on the injector, you will see that it fires 6.35ms, and you will see that it fires twice per engine revolution, 4x per engine cycle. The advantages of why we did that was that fast sync and no cam sensor needed. The main disadvantage is that some fuel is injected into the cylinder while the valve is open which makes cold start/idle tougher and under load emissions get tough as well.

So no, each cylinder isn't getting just 6.35ms of fuel.

 

[ttmott]

I'll try this one more time, then give up.

MEFI1 has two injector drives and were used for both TBI (one or two injector systems) and PFI systems wired with each driver firing four injectors at the same time (V8s). Each driver could be configered to fire it's bank once or twice per engine revolution, we called it banked double fire. The "data" showing the injector pulse width as 6.35ms is how long the ECU would fire each injector twice per engine revolution.

If you put an O-scope on the injector, you will see that it fires 6.35ms, and you will see that it fires twice per engine revolution, 4x per engine cycle. The advantages of why we did that was that fast sync and no cam sensor needed. The main disadvantage is that some fuel is injected into the cylinder while the valve is open which makes cold start/idle tougher and under load emissions get tough as well.

So no, each cylinder isn't getting just 6.35ms of fuel.

Ok I get what you're saying. Can you tell us how the injectors get to sub- 1ms to get a decent idle mixture based upon firing four times per cycle? If the injectors are firing at that duty cycle (which isn't much at all) and four times per engine cycle, how in the world can you trim back to get idle?
In this engine I have 120 LB/Hr peak and hold injectors and will need to run them at 95% duty cycle for the anticipated load. I really need larger injectors but for the sake of limiting pulse width to greater than 1.5ms at idle I really can't go larger to get a reasonable idle mixture unless I go with 16 smaller ones. The injectors can't cycle faster and reduce fuel delivery beyond about 1.5ms.
I guess what I'm saying is you can only cycle injectors so fast and the saturated style like he has are even more "lazy". So, how is this done?

 

[Bill Curtis]

Now your talking with that picture. MMMMMMMMMMMMMMM old 426 style HEMI...

 

[aerobat77]

Regarding a V8 running in half cyl mode, they run surprising well... just down about half on power! You can hear a different sound during the transition. As far as pulling a plug or injector, that will not force any power reduction mode.

This ECU is a version of the late 80s V8 controller, very simple, not much diagnostics, etc.

If this is true he should indeed find a way to check if he in fact does not has a 4 cylinder here .

I assume in your scenario one injector bank is shut down which physically means every other cylinder on both sides of the vee ?

Reading your another post you say its not a truly sequential fuel injection following the firing order with injectors firing 4 times a cycle so the total amount is basicly 6.35ms x4 ( minus fuel wasted when firing into an open valve ) .