Oilslick964

I have an 01 996TT and it has the engine remapped to the 505hp setting with headers and exhaust. I recently replaced the alternator and, since then, at WOT or pretty hard throttle, it will take off for an instant then lose power. It is still pulling just no where near full power. The stock boost gauge is acting silly, too. It will bounce up to over 1.5 bar (normally, .9 or 1.0 max). I spoke with a tech who thinks maybe the belt tensioner is failing and somehow tricking the computer? I'm not very tech-savvy and I'm hoping someone might have experienced this before. Any help? Thank you!!!

pwarnery

Please make sure the electrical plug is connected as well as the three rubber hoses. See below link.

http://www.6speedonline.com/forums/9...oh-dear-8.html

blockhed

check that before she blows up, also check for leaks and or crimped vacuum lines. 1.5 should be NOT seen by your car specially not on pump gas

Macster

If the behavior was not present before the alternator replacement then something during that job got disturbed or a vacuum line fuel supply line, something, got damaged.

If a tensioner was failing I think you'd hear the belt squeal at engine start or at other times, perhaps even see pieces of it in the rear view mirror as the belt comes apart at high rpms.

But it is worth a look to ensure the tensioner and idler rollers are ok.

Of course, while you are there, give the belt a check.

If it has 1 or both edges sharp it is rubbing and that's a sign of a problem.

If the v-ribs have sections missing that's a sign the belt's deteriorating and this can be due to improper tension.

Long shot but be sure the belt is routing properly.

Another thing to suspect, and one I lean towards more than the above, is the DME is dialing back ignition timing due to detonation signals from the knock sensors.

505hp is a lot of bump in HP.

For the engine to be able to make max. use of that and do so without coming apart requires the plugs, coils, fuel supply, knock sensors, O2 sensors, and so on be in tip top shape.

You are not seeing a CEL so misfires aren't happening, which strongly suggests to me the above items are in reasonable condition.

Thus, this leaves you with the real possibility the DME is dialing back timing to save the engine from destruction.

Sincerely,

Macster.

Oilslick964

Macster,
Thank you! That was a very helpful and insightful post. I really appreciate it. I agree, it is probably an issue with the DME. I went ahead and set up an appointment with an old friend and Porsche Turbo Guru, John Reaves of Speed Sportz (formally of the Numbered Car Co.) in Tulsa. We may end up changing the tune on the car. Either way, I think, with my limited knowledge, it's best to let the professionals handle it. Thanks again!
Paul

adam_

The first response to your original post was likely spot on...OR close. Your issue is boost control- the DME is seeing overboost DUE TO A DISASSEMBLY ISSUE DONE DURING THE OTHER WORK- and is dialing back.

(macsters post about knock sensors is nonsense...just FYI)

I was curious as to what tune you have now...DO keep in mind that many professionals will like what they sell, and you may end up with a new tune needlessly.

GL

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03 996tt

did you reset/calibrate the throttle body after reconnecting the batt? After replacing my batt, I encountered weird things. A simple reset solved my problem, including a spike in boost.