Ted,
I can attest to that statement . All of your logic and explanations (both here and there) sound right on to me. Thanks again for posting the info. I realize you did not have to share this information.

Doug,
The ECM also gets an input from the combination Inlet Air Temp/ Pressure Sensor located in the air cleaner box. That sensor measures true ambient barametric pressure and would decrease at altitude. Isn't it possible that the ECM is subtracting that pressure reading from the MAP reading and is reacting to the difference which is boost? Wouldn't that result in a truck at high altitude also being effected (at least to some degree) by the over-boost/defueling condition that Ted is talking about?

The Boss Hog
(just an idea . . . . )

 

Can someone provide detailed instructions on the wategate adjustment? Like Chadrock I am not ready to invest in a box, yet would like to realize the full benefit of the opened up exhaust and intake.

 

thefb and others... I started a new thread about the wastegate question. Hopefully people will chime in there.

 

So basically what all this boils down to is... my exhaust and intake mods are useless and doing nothing for me. Isnt that wonderful.

 

They do help keep the EGT's cooler, not a total waste then.

 

Was planning on a exhaust upgrade but now I will hold off with this information. Guess I will do the VA and exhaust upgrade together.

MikeyB

 

I'm going to echo some of Ted's comments here. We've found that swapping out exhaust systems rarely has a positive effect on horsepower, UNLESS the fueling is there to keep up with the exhaust.

We usually don't see a negative like that though. I'd suspect that the wastegate hasn't been adjusted correctly from the factory, and the truck is indeed being driven into defueling by a slight overboost condition.

On the air side of the equation, however, we have seen boosts in mid-range power on the dyno with a variety of air systems. The higher the elevation, the greater the boost in power due to the IAT/AP sensor on the airbox. Of course, a poorly adjusted wastegate will negate those gains as the 03 ECM compensates for the additional boost.

Rod

 

So the moral of this story is...buy a box of some sorts that fools the boost.

I'm off to purchase my 4" exhaust now that I've my EZ and eagerly awaiting the call from Rod or Scotty to tell me they've found my long awaited Scotty III air assembly for my, ooops, I mean my wife's truck!