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Old 07-02-2008, 07:41 PM   #131
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Quote:
Originally Posted by R.I.D.E. View Post
Best way to understand it.

The computer reads

Mass
Atmospheric pressure
Temperature
Humidity
Velocity
He said his car had an IAT and MAP sensor. So how does it measure mass, humidity, and velocity?

I understand that some vehicles have mass flow sensors, as you described.


Quote:
The computer calculates the injector duration based on these readings. Then the oxygen sensor sends the computer a report, consisting of a voltage signal which tells the computer if it needs to refine the signal ot the injector to keep the mixture at the ideal amount.


Any change that would affect the mixture can not stop the O2 sensor from doing its job, since it is determining the oxygen content of the exhaust after combustion. The system sweeps above and below the ideal amount many times a second and is continuously adjusting the mixture within a very narrow range.
Which makes sense if the car has a mass flow sensor.

Where I'm going wrong is that severach is stating the fuel is primarily metered by temperature, citing evidence that his FE is better at warmer low altitudes (higher air density) rather than colder high altitude (lower air density). His conclusion is that fuel metering is primarily a function of temperature to account for gasoline vaporization.

If the engine control system is supposed to be measuring density, then severach's observations don't make sense. Unless of course his ECU is using a less than optimal method to compute density.

The only other thing that makes sense is when I looked at a standard atmosphere calculator, where I compared the air density at 1000 ft versus a 100 degree F temp at sea level. Turns out that the air density at 1000 ft is much higher than sea level at 100 deg F.

If severach had temperature and altitude data, a better comparison could be made.
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Old 07-02-2008, 08:27 PM   #132
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Quote:
Originally Posted by chope View Post
make one install it then tell me it wont work the guy who showed me worked for gm and has a patent pending for a device that works on this idea
chope:
Your idea does work people need to try it before judging you on your claim.Here's a patent similar to your idea..

http://www.freepatentsonline.com/4527533.html
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Old 07-02-2008, 08:29 PM   #133
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It has been known in the past that providing a means to preheat gasoline prior to entering the carburetor of a gasoline engine, can provide increased efficiency and therefore better mileage in a vehicle utilizing such an engine equipped with such a gasoline heater. For example, Canadian Pat. No. 973,439
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Old 07-02-2008, 11:24 PM   #134
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Originally Posted by ShadowWorks View Post
I think some cars use EGR to try and lower temperature and reduce knock, what would you say is to hot on a typical car engine?
It varies. I've never had the IAT in the 3.8L above 140*F but even at that temp mileage was already heading back down. The IAT is more than a foot away from the intake runners so the air is even hotter by the time it goes in. I've shot the headers on a Chevy 350 with a laser temp gun and they were at 200*F and there was no audible knock. The max is a matter of engine design but many forum posts indicate that 100*F is the optimum IAT for many vehicles.

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Originally Posted by dosco View Post
OK. So your car is using temperature and pressure to somehow determine the mass of the air entering the engine.
My many 4 cylinder cars had very few sensors which were sufficient to run the engine. The 88 Daytona Turbo with multi port FI had IAT, IAT-Manifold, CTS, Knock, MAP, Oxygen, TPS, and VSS. That's all it took to run that engine as well as any modern engine. With that few of sensors there is no cross checking so I had to check each one to ensure it was perfect. Of those sensors the only ones that can be used to calculate air flow are MAP and IAT and every car that was MAFless have had MAP and IAT. 4 years later the 92 Lumina Euro V6 3.1L had the exact same sensor set and ran very well.

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Next question...how is mass determined? Is there a standard atmosphere table in the computer, including a way to calculate density using temperature offsets? Or is there one base density number from which the mass is calculated?
The 99 Dodge Dakota 4.9L V6 does not have a MAF sensor. Some scan tools will report a MAF reading and others will not knowing that it doesn't have one. However MAF is calculated, it is and with no more than the sensors listed though the Dakota doesn't have the neck twisting torque that the MAF engines do. A MAF provides the necessary data much faster than the calculation from the MAP+IAT.

Quote:
That wasn't what I was getting at. If your car has a sensor that can directly measure air density and temperature, in combination with the lambda sensor it should be able to very precisely control the fuel-air ratio.
You're describing a 1985 Chevette with an oxygen sensor and a variable carb. I usually removed those and put the old carbs on because the system was so crude that it had poor driver response. You could push the pedal a long ways and not get anything more because your change was being compensated for by the feedback loop.

A lambda sensor is too slow so the only thing it regulates well is steady state. That's what the Chevette system was doing. Since rich is always acceptable the system can richen during state changes and lean out when the state steadies again. That runs fine but the emissions and efficiency are crap. All the rest of the sensors are needed to regulate when the state is changing before the slow but reliable lambda sensor can get the information out.

Quote:
It doesn't make sense to me that the intake air temperature would be the primary variable controlling the fuel metering. However you have made an interesting observation, and your vaporization hypothesis could be correct.
MAF equipped cars always use the MAF as the primary sensor for air flow since it is the fastest and most accurate. I disconnected my MAF and the car wouldn't start on the first try. It did start on the second try but it was having trouble staying running, probably in limp home mode already. A MAP is totally unnecessary on a MAF car and many do not have one but it is probably there for finer tuning and cross checking as required by the OBD-II standard. IAT isn't being used for metering on a MAF car but it along with the CTS is being used to richen to make FI run well in the dead of winter.

Here vaporization is only affecting mileage, not what the sensors see.

Quote:
Originally Posted by R.I.D.E. View Post
The computer reads
...
Humidity
I've not seen a humidity sensor on any car. The effect is so little and lasts for so long that the oxygen sensor can handle the difference through long term fuel trims.

Quote:
Throttle postion determines desired load applied.
TPS is not used for mixture control other than at idle or WOT. Its only purpose is to provide instant driver response. When the driver stomps the pedal to the floor the computer learns it from the TPS first. Other sensors ramp up more slowly. I disconnected the TPS from the Daytona and all it did was to hesitate on acceleration, surge on slow down, and refuse to idle. The car in steady state ran no different. The TPS makes the car pleasant to drive.

Quote:
Originally Posted by dosco View Post
Unless of course his ECU is using a less than optimal method to compute density.
That's what the 4 bangers do to save money. The turbo was plenty peppy so apparently using MAP+IAT to calculate MAF works pretty well.

Quote:
The only other thing that makes sense is when I looked at a standard atmosphere calculator, where I compared the air density at 1000 ft versus a 100 degree F temp at sea level. Turns out that the air density at 1000 ft is much higher than sea level at 100 deg F.
My ears have a different opinion when going up the elevator to the air conditioned 26th floor.
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Old 07-03-2008, 04:40 AM   #135
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severach;

My experience with FI systems fades around 1995, and was concentrated on Nissan versions.

Just my opinion but it would make sense that as CPU power increases the ability to program initial trim values for fuel delivery would have become more of an ECU duty than earlier systems.

The hot wire MAF sensors were prone to failure over time so it would make sense that engineers would try to find a way to eliminate them. Probably came from working with hot wire sensors that failed, and making the system still operate in failure mode, that led to the elimination of the sensor altogether with better CPU memory and programming fuel maps of better accuracy in the CPU itself.

The Mass AF sensor would have a different reading depending on relative humidity, which served to cool the hot wire more than dry air and change the resistance value. Not a dedicated humidity sensor.

Good reading your imput, I am learning some of the newer stuff.

I have tried my WAI off and on, and it seems to have a positibe effect on mileage. However I have not tried to read temps of the air intake. I would think that temps of over 100 F would not bring on richer mixtures that quickly.

Would the 02 sensor imput still cause closed loop at IAT temps over 100F or does the system go into a failure mode and open loop?

The neat thing about my simple air intake snorkel reversal is the fact that as air flow increases the temp would decrease which helps when you need power, but also manitains higher intake temps under light loads.

regards
gary
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Old 07-03-2008, 06:02 AM   #136
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I noticed sitting in baaaad traffic on tuesday afternoon that "something happened" where I was bouncing off the fan all the time, going half to 3/4 scale and back again, then after a bit of that with very little movement, i.e. no engine bay airflow, the temp gauge just slowly started dropping to about 1/3... Now on these motors the plenum is known to heat soak, and on this year it has an IAT screwed into the plenum.... so I'm just wondering if it went rich to cool the motor... with sitting in that traffic an hour my last tank sucked... I couldn't get out of it, and it was moving too "fast" to turn the engine off, and too "slow" to P+G through.
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I remember The RoadWarrior..To understand who he was, you have to go back to another time..the world was powered by the black fuel & the desert sprouted great cities..Gone now, swept away..two mighty warrior tribes went to war & touched off a blaze which engulfed them all. Without fuel, they were nothing..thundering machines sputtered & stopped..Only those mobile enough to scavenge, brutal enough to pillage would survive. The gangs took over the highways, ready to wage war for a tank of juice
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Old 07-24-2009, 01:56 PM   #137
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Bumping an old thread here.

Was a conclusion ever reached regarding severach's assertions?
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