lobuxracer

iTrader: (2)

MAF and IAT (intake air temp) generally replace MAP (manifold absolute pressure) sensors and VE (volumetric efficiency) tables. MAF is more accurate under most normal circumstances, and does a better job at emissions control. MAP is superior for determining fuel under high rates of change in operating conditions (like boosted applications, or applications where throttle position is rapidly changing, like racing applications).

Interestingly enough, most JDM systems use MAP, and almost all US systems use MAF. Even within MAF there are variations - the older Toyotas used a trap door system which is a MAF equivalent because it assumes a certain mass of air is required to displace the trap door at a given angle. Modern MAFs all use a hot wire and a thermistor. The concept is to heat the wire so the thermistor senses a constant temperature. The amount of current it takes to heat the air is directly related to the airflow through the MAF. Since this isn't a perfectly linear function, there is a MAF transfer table in the ECM that tells the ECM when the air temperature is x and the current is y, then the amount of air is z.

A MAP sensor measures pressure in the manifold. The ECM uses rpm, throttle position, and manifold pressure along with a pre-determined table for volumetric efficiency to derive how much air is entering the engine. This is why some engines using MAP get really confused by major engine changes (cams and compression) because their VE isn't what the ECM has in its table.

Does that help you understand?

ahohnstein

This same exact thing has happened to me twice in the 1.5 years I've owned the car. Both times it was VERY unnerving. Between this and a couple other things the biggest of which is the cranking engine noise, I'm thinking about an extended warranty plan when the time comes. Of course, by that time, I'm hoping to be out of this and into an IS-F. I know the wife won't go for that thought. Wishful thinking...

RocketGuy3

iTrader: (1)

I think so, lobux.

So a car doesn't really need BOTH an MAF and a MAP at any given time? They are not used simultaneously, but each is used individually depending on driving conditions? (That is assuming the car even has both... and it sounds like you're saying a car will only have one or the other).

Also, based on that information, it sounds like there isn't any need to measure barometric pressure. Or does the MAF need to know baro pressure? And would the MAP also need to know air temperature?

I'm wondering because I would think in order to accurately calculate the MAF, you would need to know the pressure (you know the temperature and the volume/current). And similarly, when using a MAP, I would think you would need to also know the temperature (you know the pressure and the volume) in oder to calculate the mass of air entering the engine.

I could be (and probably am) way off, though.

And lemme know when you get annoyed with the questions. I'll try Google again.



EDIT: Actually, nevermind, I can understand why the MAF would not need to know the pressure of the air. I guess the function of the temperature change from the heated wire should account for any pressure variations... but I would still think the MAP would need to know the temperature.

lobuxracer

iTrader: (2)

You are correct, MAP does have a temperature sensor. I forgot to mention that, and you are dead on about the MAF - it doesn't need to know pressure because it can infer density using the hot wire and temperature. That's why the transfer table values are so important to MAF, just like the VE table values are so important to MAP.

Strangely enough, the TT Supra ECM has both MAF and MAP. It's the only one I've seen like that though, and I believe they did it primarily to control the sequential turbo set up they have.

LEXCESS

This has happened to me three times now. It bounces off the limiter in either the top of first or the top of second. ECT power mode on and in D. My foot is planted to the floor in all instances and never moves. It should definitely not be doing this. Is there an update for this?

nabbun

did you take it to your dealer?

what did they tell you?

Now i'm afraid of using the power button in drive T_T

Rickster31

I did a couple donuts to wake up the tires before an aggressive drive, and while doing them I was in PWR Drive, and it bounced off the rev limited, it felt like the PWR mode knew what I was doing so it purposely didn't shift, so I wouldn't lose the power band.

Koz

The power mode may change the RPM limiter activation point (Which I thought it didn't). I’ve also noticed that just before the trans shifts the whole car lurches forward which may spike the RPMs. The problem may be that the RPMs may have lunged right at/before the shift point and just tapped the limiter (maybe going downhill). In the case of doing a burnout and bouncing the limiter, I would think that is exactly what happened. By the tire spinning the RPMs lunged past the shift point and bounced the limiter.

Koz

E-Z ES300

That is weird and these are the types of little problems people start running into when all car manufactures start throwing electronics into the cars wherever they can fit them! Lets go back to 94/95 OBDI!!!

RocketGuy3

iTrader: (1)

Sweet, that makes sense. Thanks for the answers.

fantom

Seems like bad new in Texas, as well:

In Texas - On Sept. 1, 2003, Texas state laws regarding street racing changed from a class C traffic violation to a class B misdemeanor. That's not a joking matter ... that would now be the same as getting a DWI. It's a county charge, and it aint no fun going to the county jail (not that I know first hand...)

The minimum charge for racing, as defined in the statute, is a Class B Misdemeanor (One step above a regular traffic citation and a guaranteed trip to the Travis County Justice Complex).

The charge is a Class A Misdemeanor (just below a felony) if you were legally intoxicated at the time or have an open container of alcohol as defined in the Penal Code. It is also a Class A Misdemeanor if you've been convicted once before of racing.

It is a State Jail Felony if you've been convicted two times before of racing.

Important One
It is a Third Degree Felony if, as a result of racing, someone suffered bodily injury. CliffNotes: If you get into an accident while racing and someone gets hurt, even in a minor way, it's a Third Degree Felony.

It is a Second Degree Felony if, as a result of racing, someone suffered serious bodily injury (like a broken bone or a permanent injury) or death.

Drivers License Suspensions

If you are convicted under this new racing law, your drivers license will be suspended for one year. You can get an occupational license that will allow you to only go to work, school, and home. If you are under 18, your occupational license will only allow you to go to school and home. BTW, occupational licenses cost upwards of over $300.

If you are required to perform community service as part of a conviction, after you complete the community service, you can apply to DPS for reinstatement of your driving priviledges (beg for mercy). They don't have to grant it.

If, while you are under suspension for racing, you get convicted of racing again, your period of suspension starts over from the date of your second conviction and starts over. This is in addition to all the "2nd Racing Conviction" penalties and stuff.

Keep in mind that Driving While License Suspended is a Class B Misdemeanor in itself. So, if you get caught racing while your license is suspended for racing, you'll get the Class A Misdemeanor Racing (if it's only your second and not third) and a Class B Driving While License Suspended. Plus your suspension starts all over.

For your reference for the different levels of offenses and their penalties:

Class B Misdemeanor: Jail for up to 180 days or a fine up to $2000, or both.

Class A Misdemeanor: Jail for up to a year or a fine up to $4000, or both.

State Jail Felony: Jail for 180 days to 2 years and up to a $10000 fine.

Third Degree Felony: Jail for 2 years to 10 years and up to a $10000 fine.

Second Degree Felony: Jail for 2 years to 20 years and up to a $10000 fine.

Also, there is a caveat to the State Jail Felony punishment. It states that if a deadly weapon was exhibited or used in the crime or while fleeing (that's running from the cops), then it's a Third Degree Felony. A car can be defined as a deadly weapon if used that way. Keep that in mind.

Ramon

Well my dealer called me today for an unrelated issue, my nav update DVD that they ordered for me three weeks ago finally came in. I took my car in to get the dvd put in and while I was there I told my service advisor what had happened. They were unable to duplicate the problem (not surprised) and they scanned for codes but found none, so at this point I'm just going to drive the car and see what happens.