TPS and MAF

L

Little Beavis

Member
:
2001 MP3-T (#911)
Feel free to beat me for this, but I have an idea. . .

I'm trying to determine what the TPS voltage (TPSV) is for our cars (range and value at idle), likewise what the MAF voltage (MAFV) is (range and value at idle). We stall because we have a high MAFV when we have a low TPSV.

In other words, we let of the gas and the TPSV is at the minimum, but the MAF is not. So, it would seem that we could apply a little electrical trickery to drop the MAFV at that point. Thus as the turbo is slowing down (but still sucking in air) we would be able to prevent the ECU from throwing in a bunch of air.

Now, unfortunately, I'm mechanical, not a sparky. . .however, I would think this could be accomplished with a few components and be relatively "simple". Then we can have cool BOV sounds and never stall (it only happens once in a great while).

Anyway, what do you think? Am I smoking crack again? I have a problem, I know. . .I'm working on it.
 
keep smokin crack if it keeps you thinking like that. thats cool that we might be able to fix the problem maybe with some sort of resistance device it might acomplish what your looking at trying to do like a variable risistor or something what are the voltage read outs maybe i could do some thinking
 
I believe TPSV is 0 to 4.3 V. Can anyone confirm or correct?

I have no idea what the voltage is on the MAF. Again. . .anyone?
 
Little Beavis said:
In other words, we let of the gas and the TPSV is at the minimum, but the MAF is not. So, it would seem that we could apply a little electrical trickery to drop the MAFV at that point. Thus as the turbo is slowing down (but still sucking in air) we would be able to prevent the ECU from throwing in a bunch of air.
Click to expand...

Do you mean "bunch of FUEL"?

Nick and I did some readings on my MAF back in April or so. Part of me wants to say 3v, part of me wants to say 5V. I forget.
 
the MAF Voltage is 5v, if it drops below 5v. you get fuel cut, this I know. as far as a varying voltage in the MAF, that I dont know, Shawn (chojin) might know. :D
 
Any idea what the voltage does? I'm interested in what it should be at idle and what it does under load. Thus I can see "the load" and then when TPSV goes to 0 change the "loaded" voltage to the idle voltage.

I unfortunately know nothing about the fuel cut.

Kooldino, you're absolutely correct. It was late when I posted that. . .or else I'm just really stupid. Probably both! :D

Anyway, I'm thinking of a little black box that sees load, then sees the throttle go to zero and thus uses a counter to output a modified MAFV for 1/2 (or whatever it takes), to keep the ECU from throwing in a bunch of FUEL (Damn, you Dana). Make sense?
 
This is why whe stall when going into neutral from accelerating?
I am a chowder head but it seems you said are issue is from not enough fuel not from too much?
 
Last edited:
We stall because of too much fuel!

When you let off the gas, the turbo is spinning and sucking in a bunch of air, plus you have pressurized air in the tubes. All of this air has passed through the MAF, so the ECU thinks there is a bunch of air coming in. But, the BOV lets the air out, and the computer is left throwing in a bunch of fuel. So we get real rich and stall.

So, if you could "trick" the ECU into thinking that there isn't a bunch of air in the tube, then you'd throw less fuel in. Of course this only works once the throttle is "off" and basically only compensates for the air that is still being sucked in due to the spinning turbo. If taking that part of the equation out isn't enough, it stands to reason that you could give it an even lower value to try and compensate. Basically the prototype unit would have to have a bunch of variable to tune, such as: modified MAFV signal, time the modified signal is in effect, and what voltage change triggers it. Those are the main ones I guess. Just have to know when to give it a bogus signal, what the bogus signal needs to be to keep it from stalling, and how long to apply the signal (you don't want to modify the signal if you are just shifting gears, so maybe you have to have a timer in there for the turn on as well). This won't be a simple fix I guess. . .well actually there is a simple fix. . .recirculate, but that is besides the point.
 
Really? That sucks. . .I would have to guess that is a vacuum leak then, but I'm sure you've checked into that already. You got me.

Kooldino recirculates and has no problems. . .at least I don't think he has any problems.
 
A mechanical idea another turbo guy gave me, actualy a motorcycle turb guy, was to drill a whole dead center of the TB butterfly so when closed the air can still come in. The hole doen't need to be big just enough to keep it stable. He also mentioned cracking the stop point open like I did will help slightly but the air is too turbulant and won't stop the problem totaly.
 
boostisgood said:
the MAF Voltage is 5v, if it drops below 5v. you get fuel cut, this I know. as far as a varying voltage in the MAF, that I dont know, Shawn (chojin) might know. :D
Click to expand...

the MAF has a voltage range of :: 1.5V key on.
1.6V - 1.8V engine idle
2.4V - 2.8v 2500rpm no load
it is a 5 volt sensor. The system was designed to read and process up to around 5 volts of airflow. There have been many concerns with fuel cuts and such. On the mazda speed and the regular proteges i have seen it bottm out the meter and go to fuel cut. BUT if you are tuned properly you wont have any issues. AKA 18 psi last week . NO FUEL cut no problems. Except the fact the stock vacuum hoses would blow off.
TPS voltage will be around 1.4 V at idle and go to around 4.0v at WOT some vary and will go to 4.5V
 
hummm let me do some thinking i dont know about this one though not an avrage simple fix. is the voltage readouts on a na car or turbo?
 
The airflow meter is the very first part of the intake. Any air that enters gets counted in some way or another. Any air that is released by the BOV has been counted by this meter. If this air is not returned to the intake to mix with fuel, there will be a much larger fuel to air ratio than the engine intended when it counted the airflow. The undrivable symptoms show up when you try to idle with an atmosphere vented system. If you tighten up the BOV, it wont leak at idle (not sure how good this is for the turbo), so the symptoms will not show up. This does not mean that the problem is solved. When your BOV releases between shifts, your car may not stall, but it will run incredibly rich, which hinders performance! so lets tinker with the electronic trickery and see what happens. my car ran good with the type s turned in and idled great didnt stall but what is the purpose of it then? maybe some how we could meater the unmeaterd air or use a vacume sorce with a box that shoots a signal out like the o2 modifier that makes the car think it is normal and not run rich when the blow off valve blows of. i dont know if that makes sense to you or not but its just an idea from a stoner so it might not make sense but i am just thinking thats all....
 
well, i understand what your saying.
one of the problems is the stock ecu shuts down the injectors completely till the point it reaches the "idle rpm" area. then it will flood the head port with fuel. There isnt enough air there to make a concious effort for combustion.
one thing ive tried in the past and it seemed to work pretty well, is to leave the thottle plate screww alone but to adjust the amount of air bypassing at idle or deceleration. It seemed to "sloww" the decell to idle around 1500rpm and then the IAC would take over and bring it back to normal. But in nuetral cruising situations, like to a light, with the BOV it would not stall. There was enough of a delay after the valve opened to gain enough pressure against the throttle plates and down the plenum thru the runners and to the injectors by the head port
 
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