Gene, I'm not sure if this is the "pre-limiting" info you're looking for, but I've got some info for you. The background is I have an Autometer mechanical boost gauge as well as a Banks 6-gun (the Banks is only for monitoring). The 6-gun reports the PSI signal that the MAP sensor actually sends to the PCM, with the line in the stock location and an ITP regulator on it. The Autometer reads actual boost from the AIH port. So, the two reading locations are on the same side of the intake and only a few inches apart.

What I can tell you is that the PSI reported from the 6-gun via the MAP sensor is consistently about 2 psi lower than the Autometer's readings. It stays consistent at a 2 psi difference from no boost all the way until the regulator limits what the MAP sensor reads.

 

Wow, is that Ball-Buster turbo that much different from the stock turbo?

I have a 2000 PSD Excursion with DP-Tuner F5 chip, BDP 1.0 exhaust housing, and ITP's Overboost Annihilator and I don't have the problem you've encountered.

With the engine warm, from a dead stop, it takes my Excursion about a half second to spool up before I'm screaming at WOT. And I can powerbrake it in any of my tunes...40T, 80T, 80econo, or 120hp.

Stewart

 

That's interesting, I would've expected the delta psi to progressively increase a little as the 21 psi threshold is approached. It seems to me that if the input vs output characteristics of an over boost eliminator could be accurately determined, a custom tuner like DP could possibly compensate by making a corresponding adjustment in the fueling tables that depend on MAP.

 

I have a few comments that may or may not help.

1. A "Zener Diode" by itself will NOT increase fueling. It had to have been some kind of resistor or something else that was simulating boost where it wasn't to do that.

2. I've removed plain old "Zener Diode" mods from a bunch of trucks that were having driveability problems, particularly at low boost. Taking the diode device out cured the problem so an Overboost Annihilator was installed to handle that task.

3. The reading of 2psi less on the 6 gun is not surprising. Try putting a scantool on that truck with the key on and engine off...I've seen some trucks that report -2psi MAP in this situation, and will report 2psi less than actual when driving. If this had been any other number but 2psi I wouldn't have commented, but every truck I've seen do that was -2psi.

4. The 1.0 Ball Buster (or any of the other 1.0 versions of the same) is NOT responsive down low with stock injectors. The .84 version would be much better if you're not going to upgrade injectors. Check with your dealer, I think you can get the other housing for it now.

Just my .02 ... FWIW.

 

Most of the "appendage" is facing down toward the grass and doesn't show well in the pic. It's an adjustable safety pressure relief valve from a commercial well set up that's normally used so that the well pump can't over pressurize the holding tank. This valve, in conjunction with my special regulator is my solution to several built in problems that are a common feature of all RVs.

The city water inlet to RVs has a spring loaded valve that requires positive pressure from the water input supply in order to force it open and let water flow into the RV. This valve stops the RV water lines from draining back out the inlet when the supply hose is turned off and disconnected. Sounds like a nice design feature, but the problems with this valve are 1) The spring and plunger mechanism are in the direct flow path, and this causes a pressure drop across the valve that restricts the flow of water into the RV, and 2) when the hot water heater cycles on, the water in it expands causing the pressure in the RV plumbing to increase to a level high enough to force this spring and plunger valve closed, and then the pressure in the RV plumbing continues to increase to levels of 150 psi, until the hot water tank relief valve opens. On a routine bases, RV plumbing is only good for about 55 psi before you start springing leaks!

My solution was to disassemble the city water input and remove this spring and plunger valve, and I've got my system setup with brass on/off valves (to avoid drain back) and quick disconnect fittings on the hose. Now, the pressure build up from the hot water tank goes back out the inlet, through the supply hose, and starts building up at the regulator, and that's the long story behind the pressure relief valve. My regulator is set at 50 psi, and the relief valve at 55 psi. When the water heater goes through a heating cycle, and if no RV faucets are opened during this time, the relief valve opens and about 16 oz of water leaks out onto the ground.

 

I'm not saying that I don't believe you, but something caused me to have a nice black cloud in 20T and 60T programs when I'd stand on it before I removed the wire. Yes, 80 and 120 HP programs bellow out the black smoke and the spool-up is incredibly fast. However, I don't normally drive in 80 or 120....even unloaded.

I sure wish I had any bad things to say about my simple wire setup.....

And you'll find it is true with Duramax trucks too. The PCM and a boost gauge RARELY coincide with eachother....kind of like Bank thermometers and the ones in the overhead console. Voltage drop/resistance values used are so vague for a given displayed reading that there is always a slight error.

Yes, I can get a .84 housing for this turbo but I don't want it. I bought the 1.0 for towing at highway speeds and this thing is a miracle worker for that. Just wish I knew where my fueling went........

I really appreciate your comments on the subject and would like to thank you. Thanks.