Tricking the Mass Airflow sensor//voltage resistance

[pauls]

Several months or years ago there was a thread on adding resistance to the air flow sensor circuit. It involved using resistors from Radio Shack and splicing them in the wire. The goal was to trick the computer into thinking the air charge was much colder. I'd like to try this at the track, but be able to return to normal for the street. I'm thinking of something like a fusable link in the wire that can be altered and returned to stock.

Anyone have experience with this? And how did you determine the resistance needed, what did you use. Did it work at the track.

 

[Ulysses]

A MAF? Sure it was here you read that?

 

[ewave]

Viper's don't have a mass air flow sensor.

The CPU monitors the Manifold Pressure, and looks at the RPM to make guess (from pre-programmed tables) of the amount of air that is entering the engine. In addition, the throttle position and air temperature are also measured, to help estimate this.

When the car is running at part throttle, the system is closed loop, meaning that the CPU looks at the Oxygen sensors output, and based on this it adjusts the fuel quantity to get as close to the correct fuel/air ratio as possible for reduced emissions. This is a emission requirement set by law. When the car is at WOT, or close to this, then the system switches to OPEN loop. It ignores the reading of the O2 sensors, and just looks at the manifold Pressure, Air temperature and engine RPM. At this point the CPU is guessing what amount of fuel to add, and does not check to see what the O2 sensors are saying, hence the name "Open Loop". I'm pretty sure that there are no EPA emission requirements for a car when it is operating with WOT.

So, if you want to change the fuel mixture ratio at part throttle, when the CPU is running in closed loop mode you have to at least fake the O2 sensor output to the CPU: If you output a lean condition, the CPU will try to compensate and make the mixture richer.

If you want to change the fuel mixture ratio when at WOT (Open Loop), you can do this by faking the signal coming from the manifold pressure sensor. Telling the CPU that the pressure is higher will cause it to dump more fuel into the engine.

I'm sure there are others who know more about this. Please anyone correct me if I am wrong.

 

[GR8_ASP]

Paul gave an excellent summary of the MAF situation for the Viper.

My guess is the fuel/air ratio solution you saw was the inlet air temperature sensor. It is located on the airbox near the inlet hoses.You could measure its signal and adjust it to provide a desired amount of fuel. An in-line resistor might be able to do just that. Note that the difference would be applied under all open loop conditions.

Ron

 

[GTS Bruce]

Correct me if I'm wrong but doesn't the viper run too rich at WOT? Bruce

 

[GTS Dean]

I can't remember the guy's name now, but he's from Las Vegas and loves to use Nitrous Oxide.

"Jason Vegas" was it?

 

[Marv S]

You thinking of jason tarnutzer? He had the abs setup and other esotaric viper mods. http://vca1.viperclub.org/cgi-bin/ubb-cgi/search.cgi?action=simplesearch&SearchIn=&ForumChoice=ALL&SearchTerms=&BooleanAND=&SearchDate=&[email protected]&ExactNam e=yes&File=temp-2452347-133630-3yqp.cgi&Total=15&StartAt=1


<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by GTS Dean:
I can't remember the guy's name now, but he's from Las Vegas and loves to use Nitrous Oxide.
"Jason Vegas" was it?<HR></BLOCKQUOTE>

 

[pauls]

Yes, there was a Jason Tazmer??? Vegas Vipers. Used to have his own discussion board.

 

[LTHL VPR]

We have tried using variable resistors on the IAT (intake air temperature) sensor like you are talking about. It doesn't really do too much for the Vipers. The reason is because the IAT sensor is in the airbox, so it doesn't really get hot like it does in other cars that have the sensors placed in the intake itslef or other areas closer to the engine. There are some other modules that can adjust the IAT with the ECT in an attmept to richen or lean out a mixture. They haven't worked too well on the Viper either. We have been able to test products like these on our dynojet, but it hasn't shown any consistent gains. I would look somewhere else to try and get a few more ponies.

-Wayne (LTHL VPR)

 

[GR8_ASP]

I read the post again. Is your intent to increase the fuel - air ratio? If so there may be easier ways. One of the easiest that I am aware of is increasing the fuel pressure which increases fuel injector flow rates. Another way is to purchase higher flow injectors. These are ways to provide more fuel at the given settings. Of course you could also remap the controller.

Ron

 

[Jack B]

Merely moving the air temp sensor into the outside air stream will help. This has been done for many years with a variety of cars.

Another issue, the NOS brand nitrous setup puts a variable resistor in the air temp sensor circuit to fool it into thinking it is -20. At the same time it tricks the coolant temp sensor. Both must be done simultaneously to get full rich.

 

[RoyV101621]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by ewave:
If you want to change the fuel mixture ratio when at WOT (Open Loop), you can do this by faking the signal coming from the manifold pressure sensor. Telling the CPU that the pressure is higher will cause it to dump more fuel into the engine.

I'm sure there are others who know more about this. Please anyone correct me if I am wrong.

<HR></BLOCKQUOTE>

sounds like Sean Roe's VEC-1

 

[pauls]

Yes, Dr Speed that is what I'm inquiring about. Air inlet temp. Tell it( the sensor) it's colder on a warm day and more fuel is added at WOT.
Someone presented a way to trick this sensor via more resistance. Doing this artificially on the Dyno produced a HP increase I want to create at the track. Looking for input from the person who experimented with this.

 

[9 seconds]

The NOS "dry" system taps into this AIT sensor. This is how it gets its fuel enrichment to go with the N2O. Ask BTR Tom. I'm sure he knows what is inside one of these control boxes.