jeanmarcboilard

I recently purchased a beautiful 02 996TT with lots of mods including Tial 44 mm wastegates, Greddy controller and Softronics tune. I'm getting boost spikes up to 1.5 bars at just past 1/2 throttle. My question is could this be an issue with the tune or more likely with the boost controller and wastegates? Any info would be greatly appreciated. Thanks

993GT

I'd bet the wastegates are to blame

"02996ttx50

^1 improperly adjusted wg's will put your boost all over the map no pun intended. the greddy only further complicates all of it, i would imagine.

jeanmarcboilard

Thanks for the suggestions and sorry for the delay on any updates but we've been trouble shooting for weeks now. I got rid of the electronic boost control and am now trying to run on the N75. One external wastegate isn't opening until 1.5 bar with 1 bar springs or 0.5 bar springs causing my boost spikes (faulty wastegate). I've purchased new external wastegates that I will be installing next week. My question is has anyone ran external wastegates controlled by the N75, and if so, how were the boost hoses configured?
Thanks

jeanmarcboilard

Clarification: Testing the wastegate with a 1 bar spring installed resulted in opening at 1.5 bar. Testing the wastegate with a 0.5 bar spring installed also resulted in opening at 1.5 bar. Conclusion, faulty wastegate

"02996ttx50

...yes, but could also be in combination with bad n75 valve and even the other two check valves, and you also MUST confirm there are no obvious vac leaks. but the valves i mentioned are equally important and work in direct concert with boost pressure, waste gate actuation. e.g. the n75 is actually called a "boost re-circulation" valve. that must mean something.\

if you've reached the upthread/updated conclusion on your own and new wg's do not eliminate the issue, then i would think on what i said and then ask an expert.

jeanmarcboilard

Update: I have 2 brand new Tial 44 mm external wastegates with 0.5 bar springs installed (tested and fully opened by 0.7 bar) and the boost pressure hose connected directly from the y-pipe to the wastegates (eliminate potential for N75 issues) . With the car on the dyno, I quickly get up to 1.3 bars at 3400 rpm, then limp mode kicks in and reduces the throttle to 35% but the boost still creeps up to 1.6 bar by 5000 rpm and then the dyno is stopped.

My Tech/tuner thinks that the GT2860's are just pushing way too much air and that the 44 mm wastegates can't keep up with venting the excess exhaust. He believes this car was never properly functioning with this set up. The paper work that came with the car indicate these mods were installed in 2008. I find it hard to believe that the previous owner would have this set up for 6 years if it wasn't functioning properly.

If anybody has, or knows of anyone who has this set up, could you please confirm that it can be done.

Thanks

jeanmarcboilard

If you're not interested in external wastegate boost hose configuration, just skip to the last paragraph.

Well, after a long winter of endless research about Porsches, 996 Turbos, turbos, wastegates, and everything else I could find related to my car, I was finally able to take her out of storage and start troubleshooting again. I had received a bit of feedback on my posts and emails from a few members here so I started looking into my external wastegates and pressure hoses. With everything left hooked up (boost hose to the bottom port on the wastegate, vacuum hose to the top port on the wastegate) the way it was set by the local Indy shop (who appeared to know what they were doing since they have a "million dollar" AWD dyno and a giant Porsche sign out front of their meticulously clean shop and showroom) I started running some Durametric logs.

My first run resulted in the ECU cutting the throttle body to 35% and still making 1.6bars and barely hearing my external wastegates dumping exhaust to atmosphere. Scary, I know. I figured I would disconnect to "vacuum" hose on the top of the wastegate since it must not be letting the boost pressure push the wastegate open.

My second run resulted in my throttle body cutting to 35% again however now a sustained boost of 1.1bars and hearing the wastegates dumping. A lot better, but I have .5 bar springs in my wastegates, because the Indy shop installed them since they couldn't control the boost. So I knew that it still wasn't right.

I was having a hard time following the boost and vacuum hoses in the engine compartment so I decided to lower the engine a bit so I could possibly see where the shop had hooked up the top "vacuum" hose to the vacuum side of the turbo. Well, once I could finally get a good look at all the hoses I discovered that the "vacuum" hose was actually tied into to the boost hose, essentially creating a net zero effect on the wastegates and not allowing them to open when they were both connected to the wastegates and also bleeding of the pressure when I disconnected the top one. So I disconnected their set up and reconnected only the boost hoses from the N75 to the bottom wastegate ports. Voila, the boost is finally controlling at set spring pressure. Now I just need to install my 1bar springs, get a tune, and I should be set.

Moral of the story, just because a shop has a flashy dyno and a big Porsche sign out front does not mean they know what the **** they are doing.

"02996ttx50

i find it astonishing how many owners of modded cars live with issues that they shouldn't and half the time aren't even aware that issues exist! like improper boost levels etc. vac leaks etc

and shops are much the same way. it;s much harder to find one that can quickly sort out issues with modded cars, than it it is to find ones that are largely clueless. dealerships!? forget it lol

Dock

I think sometimes it's a matter of the owner not really knowing what all the mods are. Some people buy a 996 Turbo and have no idea what mods they bought as the dealer wasn't told by whoever traded the car in. Additionally, I don't think all dealers or independent mechanics spend time learning all of the various tuner's programs and how they are supposed to operate, so diagnosing a problem in these cases can be difficult.

rmc1148

It surprises me how many people have issues and with little mechanical knowledge attempt to diagnose and repair= this is a complicated set up. Most shops don't really understand the systems completely and guess. I'm lucky as in so far I've never had something go wrong that I couldn't figure out and repair with some reading.

"02996ttx50

that has to be true. the more tuners and various differences, the more variables, etc etc.

buying a car with unknown mods isn't a process of discovery i would ever hope to embark upon.