Boost line mod to Fool the ECM?

[apextrans]

This was mentioned in another thread & I don't remember which one. What do I need & how do I install it to keep the check engine light from lighting under heavy boost?

Also sorta related. Swamps told me I have a low boost issue. I'm putting out around 27-29 psi on the extreme setting. What are some of you guys making for boost? I thought I was doing ok with those #'s. Of course more would be great.....without hurting stuff.

 

[Mike]

Scott,

Check out this product to eliminate your overboost condition.

As far as total boost, you do sound low. I have noproblems at all hitting 35-37 psi boost in my TOW mode. twildman chip and Beans Stg I's.

 

[apextrans]

Thanks for the link. Based on what I read, it sounds like that will cure the SES light.

Any thoughts on the low boost numbers? David @ swamps told me to check my exhaust joints for leaks, which I did & found none. The other thing he suggested was welding the wastegate shut or wiring it shut. He told me about a truck they had there that was opening the waste gate @ 3lbs. When I did my compressor wheel I did the pedestal mod & EBPV mod and then put on a 60,000 mile turbo from my buddies '02. (He put on a BB turbo @ 60,000 miles). I figured that was a better idea than putting a 150,000 mile turbo back on.

Where else do you lose boost?

 

[Mike]

If you really are setting the SES light due to overboost, the PCM defuels the engine at +25psi so you really arent losing boost. You just dont have the fuel to make it.

 

[Double-S-Diesel]

best bet is 4.7 volt zener diode, taps into the middle wire on the map sensor.
IMHO works better than the boost tube.

 

[apextrans]

What does the diode do? I mean how does it help with what the PCM sees as overboosting?

 

[pafixitman]

I take a stab at this...

The map sensor is measuring the manifold pressure and supply a "signal" (via voltage) to the computer. This in turn regulates how much fuel is supplied. By using a Zener diode, you are regulating the voltage to 4.7 (anything higher is supplied in reverse).

 

[Double-S-Diesel]

PA got it correct. basically the diode will only allow the cpu to see 24 psi.

 

[apextrans]

ok. I might give that a try. Whats special about a Zener diode, or will any diode work. Don't know much about electronic stuff like this.

 

[pafixitman]

A regular diode is one way. Zener "sends back" anything greater than the stated voltage.

 

[apextrans]

Went to 2 radio shack's & could only find a 5.1 Zener. Will that work?

 

[pafixitman]

I don't think so. Reason being the computer is taking a voltage and "converts" that to a psi reading. The higher the voltage, the higher the psi reading. Call Baynesville Electronics on Joppa Road (@ Loch Raven Blvd). I'll bet a cold one they have it in stock.

 

[apextrans]

I don't think so. Reason being the computer is taking a voltage and "converts" that to a psi reading. The higher the voltage, the higher the psi reading. Call Baynesville Electronics on Joppa Road (@ Loch Raven Blvd). I'll bet a cold one they have it in stock.

Didn't even think of them!!!!

 

[apextrans]

Anybody ever heard of a diode causing the MAP sensor to burn up?

 

[Double-S-Diesel]

74 k on mine, dont know how many on all the others.
have had a few diodes go bad.