RSRRacer

Over the last few weeks, the max boost has gradually dropped. That is, under "baseline" normal operation conditions, I would see .7 bar with an occasional .8

Now I see .5 with an occasional .6

Ruled out bad fuel or ambient temp.

What would be a few of the most logical faults? Loose hose to IC? Bad diverter valve?

Thanks

PorschePhD

I wouldn't assume anything until I put a mechanical gauge on it to confirm. The cluster has a pretty low resolution and at times will not read right. Also the MAT/Boost sensor could be a little slow as well.

msindi

Could it be a failing dump valve??

RSRRacer

Stephen:

Thx for the reply. Its not just the guage, definitley loss of power, I am guessing it is only making 320-340HP since it was accelerating at .6 bar about like my old 996 NA.

PorschePhD

Keep in mind that the system will watch the way you drive the car. If it see a trend that is more geared towards fuel economy and not performance it will slow it's self down. I would try to run out to a nice stretch of highway and roll it in a higher gear like fourth and fifth and roll in to the boost a little shy of 3K and make a few long runs like this. See if the system reacts positive and comes back to life. As temperatures get warmer you may see a drop in performance as timing is pulled and boost to accommodate a safe range.

RSRRacer

Steven:

Sorry - should have added that these probs occured not only over the last few weeks during street driving, but most recently and most severly (today) at a track event. Even reset the DME by disconnecting the battery.

Thx

Ruiner

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by RSRRacer:
<strong>Steven:

Sorry - should have added that these probs occured not only over the last few weeks during street driving, but most recently and most severly (today) at a track event. Even reset the DME by disconnecting the battery.

Thx</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">I'd hook up a mechanical gauge, honestly. You might have a loose vacuum hose somewhere. That is sometimes the problem. I wonder what the wastegates are set to open at by default.

Boost is highly affected by ambient conditions; namely heat/humidity. Heat soak can be a problem on the intercoolers as well as knock inside the engine. If the system sees knock, it will retard the timing, knock down the boost, etc, to keep the balance. I was reading up on the knock system and it is rather advanced in the Turbo. Could be your problem, but I would put this farther down the list.

Also, if you reset your DME, it will take a few for the system to 'learn' how you are driving. Not sure on the time frame for the Porsche's system, though. I would assume that you need to push it a few miles rather hard, though, if you it is going to have an aggressive setting.

Honestly, I believe that I heard a 'honk' or two on one of my diverter valves yesterday. I couldn't reproduce it, though. I am guessing that one or both are leaking, though. My boost is staying consistant, but I am sure that boost recovery might be a smidge slower than normal because of it. However, unless the valves are leaking badly, then that really won't affect your peak boost.

Check hoses (with a system pressurize if possible to listen for leaks). That is where I would start. Then look at your fuel and perhaps ambient conditions.

PorschePhD

RSR,
It wouldn't surprise me that the system would do this after a track day. The adaptive system can take some time to relearn your street habits. In fact when I program an ECU I will drive it for 50 miles in the manner I know I have driven the rest of our cars <img border="0" alt="[burnout]" title="" src="graemlins/burnout.gif" /> Then go dyno it. 20 miles sometimes will not make a difference. In fact some of the parameters in the system as well as fault codes will need to cycle 40 times before they are cleared or set. That means that the ECU has to see operating temp not just a start up before it will say that is one cycle. The system is running 4 wideband 02 sensors that are calibrated on the assembly line to each specific sensor. The car knows the conditions probably better than we do. On a side note things such as hose etc are a good thing to check, although they almost always throw a code. There is a TSB out on the intercooler hoses FWIW. See below

Turbo Pressure Hose - Power Loss/Slow Acceleration
911 Turbo
2/00 2139

Binder - 2, Fuel, Exhaust & Eng. Ele.

10-6-00

Power Loss and Lack of Acceleration

Vehicle Type:
911 Turbo (996)

Model Year:
As of 2001(1)

Concern:
Poor acceleration and loss of power because of the pressure hose connecting the turbocharger inner cooler is loose.

RSRRacer

Thank you all very much. I'll post the outcome when availble.