got a BOMB Q that maybe someone can answer

[drewRoberts]

ya'll might remember me wanting to know what kind of easy ways I could make a little show smoke from my 04. 5. I stumbled across something that I did and was wondering what the effects would be of doing this.



across the 5v input and the Boost sense line of the MAP sensor I put a 36ohm resistor in at first and realy didnt get much out of it even though I was adding in ~138mV to the sense line. so I lowered the resistance and put in a 33 ohm resistor that added ~150mV to the sense line. I can definately tell a difference there so while I was messing around with it I threw on a 30 ohm in, added ~166mV. this resistor was smokin hot in more ways that one :-laf (not only did I break the tires loose in 4th, but I also saw 1350F )



anyway, I know this is not adding timeing to the injectors, but I am wondering if this is adding duration or increaseing rail pressure. I'm thinking this is upping the antie on the rail since the way it acts. this is something I dont want to do for fear of popping something. am I right in saying this is just adding pressure, or have I stumbled onto something that only adds a little duration to the injector pulse.



I could figure this out if I had my 4 channel o-scope, but it is out for calibration right now



oh, BTW, I popped a code P0238 on the 30 ohm when I let the grid heater cycle, however I'm running just fine on the 33 ohm. might toss the 30 back in wired up to a 3 way switch :-laf

 

[WUnderwood]

so confused... .

 

[ohnoitsyu]

If your resistor was getting too hot, you may need a resistor if the same value but with a higher wattage rating. The higher wattage won't change the resistance, but it will solve your heat issues (with the resistor, not your EGT).

 

[Tomeygun]

ya'll might remember me wanting to know what kind of easy ways I could make a little show smoke from my 04. 5. I stumbled across something that I did and was wondering what the effects would be of doing this.



across the 5v input and the Boost sense line of the MAP sensor I put a 36ohm resistor in at first and realy didnt get much out of it even though I was adding in ~138mV to the sense line. so I lowered the resistance and put in a 33 ohm resistor that added ~150mV to the sense line. I can definately tell a difference there so while I was messing around with it I threw on a 30 ohm in, added ~166mV. this resistor was smokin hot in more ways that one :-laf (not only did I break the tires loose in 4th, but I also saw 1350F )



anyway, I know this is not adding timeing to the injectors, but I am wondering if this is adding duration or increaseing rail pressure. I'm thinking this is upping the antie on the rail since the way it acts. this is something I dont want to do for fear of popping something. am I right in saying this is just adding pressure, or have I stumbled onto something that only adds a little duration to the injector pulse.



I could figure this out if I had my 4 channel o-scope, but it is out for calibration right now



oh, BTW, I popped a code P0238 on the 30 ohm when I let the grid heater cycle, however I'm running just fine on the 33 ohm. might toss the 30 back in wired up to a 3 way switch :-laf

Sounds like what we were doing to the TST powermaxCr's -- We would feed a 5v signal to the input to the TST, and it would read 44psi all the time. . Talk about fueling NOW!



Although this sounds like the opposite - showing a lower boost so the ECM fuels harder to get higher boost...



ok,ok, honestly I have no idea... .

 

[KBennett]

I don't think you are putting the resistor in the right place. Sure, you may have got the results you were looking for but you may be putting a big load on the MAP sensor and eventually kill it. I would try a voltage divider network to create the same scenario.



Try putting a resistor in series with the signal wire and another resistor after that between +V or Common to get the results. This will divide the output across the two resistors.

 

[drewRoberts]

it is not the resistor that is getting hot, I'm useing 1/4 watt resistors.



all I am asking is this. . .



when I up the voltage of the MAP sensor boost sense line, the computer sees more boost than there actualy is. by the computer seeing more boost is this raiseing the pressure the CP3 is putting out, or are the injectors being held open longer?



the computer is seeing higher boost, I can tell through my boost and EGT gage, I'm just wondering what effect this is having on the rail pressure.

 

[nickleinonen]

by the computer seeing more boost is this raiseing the pressure the CP3 is putting out, or are the injectors being held open longer?

probably a combo of both pressure increase and duration increase. piggyback the rail pressure sensor with your with your meter [pin 1&2 i believe] and see what the voltage is there when there is no resistor and when there is a resistor. . more voltage there would mean more pressure. . i believe somewhere in one of the threads there is a chart showing what the rail pressure/signal voltage is. . [i remember it being under the spa rail pressure gauge threads]