overboosting??? what is the 4.7 diode boost fooler???

[strokin'_tatsch]

what is this that i hear about a 4.7 diode boost fooler for 99 and up 7.3's? i have a friend who has a '99 psd with a chip, intake, built tranny, and new injectors and after driving it myself i have noticed that it is rather laggy on the top end. it felt like the truck was defueling really badly and i'm thinking it's from overboost, but it doesn't set a CEL except for at really high rpm's, then the CEL will flash on, but will go right back off. i unplugged the wastegate on it to see if i could get the boost pressures up higher to see if it would set the CEL, but it still didn't. what do y'all think??????? is his map sensor seeing too much boost? i want to help him out with a boost fooler and was wondering about this 4.7 diode thing. thanks in advance for any help!!!

 

[Tail_Gunner]

what is this that i hear about a 4.7 diode boost fooler for 99 and up 7.3's? i have a friend who has a '99 psd with a chip, intake, built tranny, and new injectors and after driving it myself i have noticed that it is rather laggy on the top end. it felt like the truck was defueling really badly and i'm thinking it's from overboost, but it doesn't set a CEL except for at really high rpm's, then the CEL will flash on, but will go right back off. i unplugged the wastegate on it to see if i could get the boost pressures up higher to see if it would set the CEL, but it still didn't. what do y'all think??????? is his map sensor seeing too much boost? i want to help him out with a boost fooler and was wondering about this 4.7 diode thing. thanks in advance for any help!!!

In general, the 4.7 zener diode is an electronic method of doing the same thing as a Boost Relief Regulator.

When the PCM starts defueling due to an excessive boost signal from the MAP, the MAP is sending a 5 to 6 volt signal to the PCM. Depending on the program on the PCM, when the PCM gets a MAP voltage above a certain threshold point, it defuels the motor. What the 4.7v zener diode does is "bleed off" to ground, any voltage above 4.7 volts. The end result, the MAP signal to the PCM never exceeds 4.7 volts and the PCM never senses an overboost condition, and the PCM doesn't defuel the engine.

 

[strokin'_tatsch]

cool. so how would i go about doing the 4.7 diode boost fooler on this truck? we have to do something to get it to stop feeling "laggy" it accelerates good all the way until it gets to around 2500 and above rpm's then it starts to feel like that. i want to do this mod. can y'all help me figure out how to do it?

 

[bbressler]

Not sure where I found this, but:

To hook it you simple splice the banded end of the diode to the LG/BK wire and
the other end of the diode to the GY/R wire at the map sensor.

I did it on my old truck, didn't know the OBS map sensor does frequency and not voltage changes..

I found a Zener diode at a Chinese TV repair shop. Ripped me off and charged me $7.00. Texas Electronics in Lubbock has them like 10 for $3.

 

[strokin'_tatsch]

cool. so can i get these diodes at radioshack or no? would it be better to just buy the overboost annihalator???

 

[bbressler]

Radio shack doesn't have them. I think you're better off building your own....you KNOW what's going on with your truck, not to mention it's a LOT cheaper.

I'm going to be in Lubbock tomorrow, I may can pick you some up and mail them to you....

I'll let you know tomorrow if I can get them.

 

[bbressler]

I've got two...PM me your address & I'll send you one (or two if you want)