• Welcome to the Contour Enthusiasts Group, the best resource for the Ford Contour and Mercury Mystique.

    You can register to join the community.

What determines the onset of stupid-rich

S

SicSE

Veteran CEG'er
Joined
Sep 7, 2007
Messages
889
Location
Kennesaw, GA
I did 3 dyno pulls today and I'm having trouble theorizing the A/F results, so work with me here.

The SE PCM goes stupid-rich somewhere after 5K and I'm trying to theorize what the determining factors are, that tell the PCM, "hey, it's time to go stupid-rich"... because stupid-rich doesn't always happen at the same time. Stupid-rich happened on run 1 at about 5600RPM, then about 5400RPM on run 2, then shortly after 5200 on run 3. I started all my runs with ECT at 201° on it's way up, (meaning the fans kicked off about 4° ago), and an IAT of 80°. The runs were all within 10 minutes of each other, so drastic barometric or humidity changes or anything like that can be ruled out. Nothing that I datalogged looked to be the trigger for stupid-rich.

At the onset of stupid-rich, the datalog shows the fuel enrichment via STFT's, the dyno chart shows the corresponding drop in A/F. Nothing else in the datalog changes much at that point. A degree change in IAT, (90°ish), or ECT, (206°ish), a 1% change in load, (104%), no change in MAFS voltage, (hits about 4.07 volts max), and spark advance holds steady at around 24°.

Anyone with any theories about the PCM's stupid-rich caculation? There is a calculation for everything and I NEED to figure out what all triggers stupid-rich.
 
SicSE said:
Yes but the PCM ignores the O2 readings in open loop so I didn't give their output much consideration... though I think they hold steady at .9v for the duration.
Click to expand...


i think that may be part/all of why it was dumping extra fuel. unless your in closed loop the PCM just looks at a table based on RPM, MAF, IAT, coolant temp and adds a preprogrammed amount of fuel that coresponds to the readings it gets from those sensors.
 
One possibility

One possibility

SicSE said:
I did 3 dyno pulls today and I'm having trouble theorizing the A/F results, so work with me here.

I don't see if you've cleared the adaptives in a power-disconnect, but your statement that the Short-term Fuel trims are causing the heavy enrichment would make me think this may be the case.

Though, I'm far from expert on the Contour fueling strategy it would make sense to look at the knock-sensor output - is it indicating knock? Is there a slight fall-off in spark advance? Excessive fuel is one method of eliminating or delaying knock onset. It's been used heavily on OEM factory apps for years for just this purpose.

Your statement that on each run the enrichment starts 200 rpm earlier seems to suggest a temperature relation. I know, the temp sensors don't show significant increase - but they are not located at down by the actual cylinder ports, where the air enters the chamber. This air is going to be heated more than the IAT shows due to heat-soaking of the aluminum intake manifold.

Intake - air temp is directly related to knock-onset.

So, suggestions:
1.Point a cooling fan at the top (rear-bank particularly) of the engine to cool the intake manifold between runs.
2. WOT fueling is open loop, meaning that fueling comes from a table without direct feedback - hence the operating environment is changing around a fixed table. So rich starts earlier.
3. Sounds strange, but the hotter the intake air, the less dense it is. So it may well be that your "stupid-rich" fueling is caused by less oxygen due to lower density.
4. It would help if you could post what the actual value of your air/fuel ratio was. If it dropped below 12.0:1 then you'll need to fix it. Any richer than this means a drop in power at any throttle. It would also indicate a problem that needs fixing - such as knock.
5. Make sure that there is a huge amount or air being forced through the radiator during your runs - check this carefully. By the time the fans come on, you're already too hot to make big power.

Hope this helps.
Click to expand...
 
99SEinLivonia said:
Though, I'm far from expert on the Contour fueling strategy it would make sense to look at the knock-sensor output - is it indicating knock?
Click to expand...
That is a VERY good point that I didn't think of.

99SEinLivonia said:
Is there a slight fall-off in spark advance?
Click to expand...
Spark advance doesn't change at all.

99SEinLivonia said:
This air is going to be heated more than the IAT shows due to heat-soaking of the aluminum intake manifold.
Click to expand...
This is along the lines of what I was thinking, but I didn't tie it in with the knock sensor... brain fart I guess.

A/F goes down to 10:1. Ratio drops below this so I can't really say how low it gets.

We use our emissions test fan to blow on the radiator & it is supposed to generate airflow equivalent to 25mph wind.

I'm already running colder plugs & premium gas because of my compression, (supposedly somewhere around 11:1), but it looks like I might have to go even colder with my plugs.

Thanks 99SEinLivonia - you've been a HUGE help. :cool:
 
its the PCM that causes the rich conditions ... SE PCMs are programmed rich from the factory ... maybe its the fuel injectors being over worked too, ie to large of a duty cycle ....
 
Most engines ideal AFR's will be between 11.7 and 12.6ish. Can't remember the exact numbers off hand, but those and "rich best torque" and "lean best torque" AFR's.

Granted engines sometimes can't run those AFR's due to octane and VE of the engine.

You'll notice that most FI cars, well tuned, with enough octane, tend to run around 11.7 AFR. Most well tuned NA engines will run around 12.5-12.7 since the cylinder pressures are much lower so you can run leaner.

Stock ECU's are tuned to run cars at 10:1 because they'd rather lose the 20hp that most people will never care about in order to cut engine warranty claims.
 
Contour.jpg


It looks like it stays at 10:1 because the computer hooked up to the dyno only goes down to 10:1... I can't drop the minimum lower so I don't know how low it actually gets.

This looks to me like the addition of fuel is the PCM's reaction to something that happens at just before 5500 RPM, and causes an initial power loss. The PCM is seeing a fault, or discrepancy in what it WANTS to see, and goes full-rich right at 5500 RPM. Which could give weight to 99SEinLivonia's theory about knock. Except for the fact that the initial response to knock should be retarded spark... it shouldn't jump right to full-rich and NOT retard spark, if it's seeing knock. Unfortunately, Ford got rid of the knock sensor PID in their datalogging software so I can't monitor it to tell either way. :confused:
 
Last edited:
Keyser said:
Is the cat converter protection turned off? The ECU throws extra fuel when it gets too hot.
Click to expand...
Still the stock PCM... nothing is tuned yet.

When what gets too hot? Coolant and IAT temps stay below 210° & 87° respectively.
 
Clarification

Clarification

SicSE said:
Still the stock PCM... nothing is tuned yet.

When what gets too hot? Coolant and IAT temps stay below 210° & 87° respectively.
Click to expand...

He means the temperature of the catalyst monolith or brick. There is a specific temperature at which the ceramic structure (the monolith) inside the steel casing begins to fail. This temperature is measured by placing a thermocouple in the middle of the brickwhile running on the dyno and in-car during development. If kept at too high a temperature for too long the monolith melts and plugs the exhaust.

Again, I'm not familiar with the fueling strategy in the 'Tour, but this suggestion makes a great deal of sense. While fueling cools the combustion chamber, it also cools the exhaust - same gases-different place and now without water-cooling.

The important part here is that since the PCM is dumping fuel, it is for protection of some component. Because the spark is not being retarded, the protection is aimed at either the Catalyst or the exhaust-valves.

The reason I say this? Fuel takes a specific amount of time to burn at any given A/F ratio, so if the spark is retarded the fuel will still be burning as the exhaust-valves open - dramatically overheating them in short order.

Think of running important bits in the hot part of a blow-torch. Not good if you want to keep the bits intact for a long time.

The same thing will happen to the close-coupled catalysts which are less than a foot away from the exhaust-valves. Either way, the fueling is there for a reason. That reason appears to be temperature reduction of some component either in the combustion-chamber or downstream of it.

Not sure of a solution just now. Hope this spurs further thought though.
 
A cynical thought

A cynical thought

Barge said:
Stock ECU's are tuned to run cars at 10:1 because they'd rather lose the 20hp that most people will never care about in order to cut engine warranty claims.
Click to expand...

A cynical thought for you. Between warranty issues and protecting the Prestige of the Premium SVT power ratings (something like 170Hp SE vs 190Hp SVT-depending on year) - which is more important to Ford?

Obviously, warranty. But I would argue that running richer than 10:1 was absurdly un-necessary.

Finally, from personal experience running calibration on an engine-dyno I can state that even on air-cooled engines (NA) running any richer than 12.2:1 will cause torque to fall off. Running lower than 11.5 will begin quenching combustion and <9.7 rich misfire predominates (excluding cold-start).
 
SicSE said:
Contour.jpg


It looks like it stays at 10:1 because the computer hooked up to the dyno only goes down to 10:1... I can't drop the minimum lower so I don't know how low it actually gets.

Should have asked before - what type of A/F meter are you using and when was it last calibrated? Was this checked against an alternate meter/sensor?

Also, do you have the option of logging MAF data via any method? I'll try to find the intake-tuning frequency of the stock engine. Maybe this is where the cylinder VE falls off due falling off the peak?
Click to expand...
 
99SEinLivonia said:
He means the temperature of the catalyst monolith or brick.
Click to expand...
Which the PCM has no way of monitoring in a properly running engine, other than looking for knock. It HAS to be detonation... HAS to be. It makes even more sense now. Before I was thinking it weird that spark wasn't being pulled, but technically, it is. The PCM should continue to advance spark as RPM's rise to compensate for the shorter time that the fuel has to burn. Spark that doesn't continue to advance as RPM's rise is theoretically the same as retarding spark at a steady RPM.

Kick ass. Thanks a lot for your help guys. Now I just need to figure out the easiest way to remedy the detonation. It really sucks that the colder plugs didn't help much, if at all. I guess that would have been a little too easy though. :rolleyes:

99SEinLivonia said:
Should have asked before - what type of A/F meter are you using and when was it last calibrated? Was this checked against an alternate meter/sensor?
Click to expand...
Not sure of brand, just know it's a wideband. Not sure if it's been calibrated, no it hasn't been checked against another one. Given what happens to power and that all other pids correspond to a drastic increase in fuel, there was no reason to doubt the readings.

99SEinLivonia said:
Also, do you have the option of logging MAF data via any method?
Click to expand...
Yes, I always datalog on the dyno. It's the best way I've found to get repeatable runs, PLUS I make recordings to be able to go back & look for problems & make sense of what the graph looks like.
 
Last edited:
You must log in or register to reply here.
Back
Top