996 turbo misfire and overboost

i have got a 2001 x 996 turbo. when i accelerate hard the car reaches 5000 and starts juddering and wont pull any more, also it pops the abs and psm lights on. when put on a diagnostic check, it said hot film air mass meter and torque reading to dms. i have put an airflow meter on and this hasnt cured it. i have since taken it to another specialist who noticed it is over boosting (1.5 bar). due to the high boost it has been popping off the intercooler pipe. the car runs perfect on light acceleration. also it runs lumpy when cold, but probably not related. does anyone have any ideas what could be causing the high boost? my limited knowledge is pointing at sticking wastegate. many thanks, steve.

1.5 bar boost is way too high, 0.7-8 on an unmapped turbo is normal, I'd take it back to your nearest indy to get checked out.

its at the porsche specialist now. i dont think the car is actually boosting to 1.5, or at least i hope not. i think its more an issue of its not getting rid of the boost it builds up, hence the high reading, so it builds up more and more. has anyone had anything similar to this before? it seems to me like ecu or wastegate, but i have limited mechanical knowledge.

mine runs 1.4bar , many tuned GT2/X50's that have been remapped will boost to 1.1 to 1.4. Unless you can confirm otherwise your car may be re-mapped. A quick way to check is to pull the ECU, open it and check the PCB. Another tell-tale is usually the exhaust....std or aftermarket? At the end of the intercooler pipework are billets which have a seal and a barb on them. The whole lot is held in place by a wire clip through the billet housings. When the boost rises(>1.1bar) it can blow off a pipe(usually the ones at the intercoolers) When this happens the ECU light comes on(by default) and the power goes. High boost cars are better fitted with the pipe alu billets which have a higher barb profile. They "hold on" better than the factory billets head/barbs. A broken, seized or incorrectly adjusted actuator(s) and or sticking wastegate is a common issue on cars >5 years old. If the actuators have been on a while and are at fault then replacements/careful re-setting is usually required

You're running 1.4bar Who's tune is that & what other mods do you have ? Thats pretty aggressive boost, most GT2/X50 tunes run 1.2bar spiking at 1.3bar... maybe.

http://www.evo.co.uk/carreviews/evocarreviews/225093/dms_997_turbo.html 1.2,3 or 4 bar is not an issue on GT2'/Turbo's that has been set-up to handle it. Mine runs about 570BHP. Usually it sits on 1.3 but if the conditions are right(ie very cold and with 99 octane) it will hit 1.4bar. also...details on the latest GT2's engine, inc boost levels..... The GT2's engine again is a modified version of the Turbo's powerplant. It features a remapped ECU raising boost to 1.4bar, different turbochargers with an enlarged compressor wheel and a flow-optimized turbine housing, a new expansion intake manifold system using the oscillating air during the cooler expansion phase and a back-pressure-optimized lightweight exhaust system partially made from titanium (titanium rear-end silencer and titanium tailpipes). The results of these modifications read as follows: 530bhp @ 6500rpm and a maximum torque of 680Nm available between 2200 and 4500rpm. The fastest of all models in the 911 series accelerates to 100 km/h in just 3.7 seconds and reaches a top speed of 329 km/h. Famous race car pilot and Porsche development team member Walter Rà¶hrl drove the GT2 round the famous Nürburgring in 7:32'44 and therewith getting extremely close to Porsches supercar the Carrera GT. " I understand that there are a few 997 GT2's/Turbo shoving 1.5/1.6bar and >650Bhp.....here is a sample for the seriously brave :floor: http://www.vividracing.com/catalog/...urrency=GBP&osCsid=v8aqtt0gn3kau5f079iqffvj54

wizard993 - you are absolutely spot on!!!! the car had been remapped and was blowing the intercooler pipe off. the ecu has been set back to standard and runs a dream now. considering i took it to 4 garages and 2 of them were Porsche main dealers, its very impressive you got it in one without even seeing the car. i would also like to thank zentrum porsche specialist for putting it right when everyone else struggled.

Glad your cars sorted and this forum was useful.......that's why we are here :thumb: :bye:

"You're running 1.4bar Who's tune is that & what other mods do you have ? Thats pretty aggressive boost, most GT2/X50 tunes run 1.2bar spiking at 1.3bar... maybe." The special 1-bar actuators and closed-loop DV's with higher/tuned spring rates give the extra .1bar.....and yes they make a difference, especially when the engine hit's 4500 rpm I have chased a few slightly modded 997 turbos on track and from low speed to about 80 there is not much in it but then the GT2 with it's extra grunt gets it's second wind.......great fun :thumb: