Question for RODBOLT

[Bilge Rat]

Could you explain Speed Density.
I am trying to get a better understanding of the F 150 engine control system.

It would be nice to get some factory information on how these motors work. I am too old to change careers but not too old to learn.

Thanks for your time on here.

[rodbolt17]

speed density EFI is dirt simple.
as air pressure changes the map sensor records it for that key on cycle.
as intake air warms up this is monitored as well.

from there the ECU is basically looking at engine speed and load.

unlike mass airflow EFI.

at the end of the day both systems attempt to introduce fuel in the intake at about 14.7/1,

[boscoe99]

speed density EFI is dirt simple.
as air pressure changes the map sensor records it for that key on cycle.
as intake air warms up this is monitored as well.

from there the ECU is basically looking at engine speed and load.

unlike mass airflow EFI.

at the end of the day both systems attempt to introduce fuel in the intake at about 14.7/1,

You might want to double check on this. Do you have an O2 sensor/gauge that can be plugged into the exhaust outer cover plate on a Yam EFI motor? I suspect that you will be surprised as to what you might see.

Stoichiometric Fred Breu was surprised.

[Bilge Rat]

How does it determine load?
Vaccuum pressure vs. rpm?

I am more at home with a die grinder, flow bench, jets, and reading plugs. Injection, ECU, etc. sure make HP now but in the end the 14/1 rule is what spins the wheel.

I think i found the answer in another thread to the above question.
Is there a tech manual on the 4 stroke EFI that a non dealer mechanic could get ?

The Navy trained a lot of electrictricans and electronic techs in the last 40 years. I have 2 uncles that learned their craft there.

[boscoe99]

How does it determine load?
Vaccuum pressure vs. rpm?

I am more at home with a die grinder, flow bench, jets, and reading plugs. Injection, ECU, etc. sure make HP now but in the end the 14/1 rule is what spins the wheel.

I think i found the answer in another thread to the above question.
Is there a tech manual on the 4 stroke EFI that a non dealer mechanic could get ?

The Navy trained a lot of electrictricans and electronic techs in the last 40 years. I have 2 uncles that learned their craft there.

What is the 14/1 rule?

[rodbolt17]

did my BE/E and FCA schools at Great Lakes naval traing and my CIWS C school at Damneck VA.
did 3 years of various electronics schools bvefore I ever saw a ship.

is there a port on the Yamaha EFI 4 stroke where O2 information may be obtained?
kinda on most.
however Yamaha has no technical data nor tooling to monitor it.

the 14/1 rule is gasoline,as a fuel for an articulated rod internal combustion motor must burn at the correct air to fuel ratio.

14.7 parts of air to one part gasoline is the magic number.
much richer that about 12.5 parts air to 1 part fuel and performace suffers dramatically and various emissions increase.

much leaner than about 15.5 parts air to 1 part fuel and performance suffers,various emissions rise and combustion temps start heading to catastrophic failure zones.

engine load is determined by manifold absolute pressure,throttle angle and engine speed.

air density is determined by a barometric reading that is locked on at the start of each key on cycle and stays at that pressure until the next key on.
its also monitored by an intake air temp sensor.

engine coolent temp is monitored and fuel trimmed during warm up.

the ECU is a simple truth table.
it monitors various input voltages and makes outputs based on this.
the ECU on some models monitors engine gear position and cranking and engine stop signals as well.

while the outboard market is closing the technology gap between automotive VS marine most outboard ECM's are rather stone aged.

[boscoe99]

All of the EFI Yams have a port into which an EGT probe or 02 sensor can be threaded. See photo below from an F150.

I ran tests on an F70, F150 and the new I4 F200. With first an EGT probe installed and then with an 02 sensor installed. With both 87 octane and then with 93 octane.

Air/Fuel ratios were in the range of 12~13/1 at idle to ~11.5/1 at WOT. At 4000 RPM the ratio was approximately 13.5/1. At no time did I see anywhere near stoichiometric of 14.7/1.

My 02 sensor and gauge were brand new. I have no reason to believe that it is inaccurate. It compared favorably with another 02 sensor.

Some folks claim that higher octane gasoline burns hotter. I did not see this with the EGT probe. All exhaust gas temperatures were virtually the same with either 87 or 93 being used. Which contradicts some statements that indicate that higher octane gasoline burns "hotter". There was also no loss of WOT RPM or boat speed with the higher octane gasoline. Which leads me to believe that higher octane gasoline does not burn slower than a lower octane, as is so often cited. If it burns slower I would have expected to see less WOT RPM and top end boat speed.

[rodbolt17]

that's because of the emissions, 14.7/1 is the best ratio.
however to alter various emissions to pass our EPA they tend to run a tad rich.
as the emissions standards get tougher you will see O2 sensors,catalitic converters and closed crankcase venting.

it only took 20 years to get closed gas vapor recovery systems on outboard EFI.

the stern drive market is closing in on the automotive ECU technology faster than the outboard market mostly due to EPA emissions regulations.
and some European countries have even stricter standards than the US market.

all new production stern drive hulls from jan 2010 must have catalytic converters.
when repowering I have to show why I cannot use a catalyst motor due to engine box space.

wont be much longer and you will not be able to purchase a carbed stern drive engine and not much longer after that the MPI non-catalyst engines will go away.

on the octane rating, most of todays 4 stroke outboards are less than 9/1 compression and anything above 87 octane is a waste of money and as it does burn slower it will leave more deposits.

now on a two stroke it can make a difference and I have observed it on my IDC dyno.

some of the higher output Yamaha 4 strokes do require 89 octane minimum.

once the Yamaha 4 strokes go to an O2 sensor you will most likely see a bit leaner burning as the fuel will have a "trim" control at all RPM ranges.

just as stern drives went to catalyst con*****ed engines with pre and post cat O2 sensors and crank position "tone" wheels so will outboards.

the Volvo catalyst engines can monitor which cylinder misfired and records how many times it misfired based on pre and post cat O2 sensor signals and the "tone" wheel signal.

wont be long and the outboard world will go the same route.

[ausnoelm]

much leaner than about 15.5 parts air to 1 part fuel and performance suffers,various emissions rise and combustion temps start heading to catastrophic failure zones.

engine load is determined by manifold absolute pressure,throttle angle and engine speed.

air density is determined by a barometric reading that is locked on at the start of each key on cycle and stays at that pressure until the next key on.
its also monitored by an intake air temp sensor.

engine coolent temp is monitored and fuel trimmed during warm up.

the ECU is a simple truth table.
it monitors various input voltages and makes outputs based on this.
the ECU on some models monitors engine gear position and cranking and engine stop signals as well..

That's what I waned to know in the question I asked a few days ago.

[keylime1]

Excellent discussion. Thank you.