okay, i know vtec engages at diff rpms depending on what motor or ecu...but...mine in a b16a, p30, s21 tranny, i know for vtec to engage, your coolant has to be a certain temperature, oil pressure has to be a certain value blah blah,......my question is, why wont it engage in neutral, ppl say that your car has to be moving atleast 10mph but that is bullcrap! i can be driving 70mph, throw it in neutral with the cluth still engaged and rev it up and no vtec, how does the ecu know that it is not in gear?

 

Well it relies on the VSS

 

Why the hell are you trying to hit vtec in neutral ? lol

 

im just trying to figure out why it doesnt...cant ever know too much

 

it works off a few sensors but if you want it to work even in nuetral then get the ecu chipped my skunk2 even engaged in reverse

 

its not that i want it to work in neutral, i just want to know Why it wont...im redoing a harness for a car im builidng and i dont want to eliminate anything i will need, that is the main reason, i know it works off coolant temp, mine doesnt have vtec oil press, i dont think the clutch switch has anything to do with it and i dont think the vss has anything to do with it like most ppl THINK, i was hoping someone would know for sure thats all

 

it pops in reverse lol

 

vss has to do with it for sure VSS codes= no vtec.The ECU looks for inputs from many sensors before it will engage VTEC. None of those inputs engage VTEC. only the ECU, however the ECU must know that certain things are ready... Tach, Pressure switch,ECT, VSS,TPS. If you have a problem with one of these or more the ECU prevents you from running your car ***** to wall because you have a problem. Its just a safeguard. Its just Honda trying to protect you from yourself.

 

because in neutral you basically have no load, if you are in any gear you have a greater load on the motor than in neutral

 

LOL...look at the schematics and you will have your answer when it comes to wiring..-__-

 

okay, you dont know what your talkin about

 

just tellin me what i already know

 

Then what are you asking?

 

The main reason you aren't allowed to VTEC in neutral is because VTEC fuel maps are entirely too rich for a no engine load situation. You could quickly ruin a catalytic converter this way.

 

look at my first post...how does the ecu know its in gear? let me ask what im asking again for all the ppl who cant comprehend what they read
HOW DOES THE ECU KNOW THAT THE TRANSAXLE IS IN GEAR?
HOW, ECU, KNOW?

 

do you have info to support this or is this what you just assume?

 

I'm not sure about our hondas, but some vehicles calculate gear by looking at the VSS and RPM readings. When the two readings properly rise and fall with each other, the car is in gear. Which gear is calculated by how fast you are going at your current RPM. Again, I don't know how Honda ECU's were programmed so this is just a guess.

 

the answer seems there to me...
obviously there is no sensor to know what gear you are in, AIM displays sell a sensor to know, but thats besides the point .. it runs off of pressure and how does it know if its in gear or not because of pressure when engine in neutral the pressure doesnt increase to the right psi for vtec to engage why no load...., in comparison to when the engine is in a load the pressure rises to the desired vtec pressure to activate. simply, because of the load in the gear itself. -___- 2cents..

 

Yes there is a sensor to tell whether the car is in gear and that gear is engaged....meaning load on the engine. It is called the MAP sensor. MAP readings are one of the most critical sensors on the vehicle MAP,TPS,ECT rule your engine management even if it is stock.

 

correct there is and MAP sensor migbeht the one telling it to activate, but the sensor is not located ontranny its on tb and that was my point!.. so pressure, map, ect, is what tells the vtec to activate in gear, and not without a load.

 

i think the ecu take more into account than you are thinking, before it tell the motor to go into beat mode.. as far being in nuetral there is no load on the transmission or the motor and im pretty sure there is some kinda sensor for that stuph.. and the ecu will need all that to calculate the fuel tables.. since it doesnt know it does nothing...