I know there is a lot of info scattered on the subject of too much boost. I did some searching (see below), but would like to provide the specifics of my car/situation and ask for other's opinions.

The car is an 02 996tt tiptronic (not X50, stock turbos). I bought it stock and for the past 20 months, have driven it with only (1) basic flash by Switzer and (2) Europipe catless stage 2 Loud exhaust. Boost readout has always been 1.1 bar constant at WOT with 93 octane.

A couple weeks ago, I was getting on the highway and heard a loud hissing/whooshing sound, then lost boost pressure (max at .4 bar). Turned out to be the N75/timing valve and a couple hoses blew. No big deal, couple hundred dollar repair that was inevitably expected, and I also took this opportunity to install EVO black billet diverter valves.

Now, with the aftermarket DV"s and replacement hoses, the car hits 1.3-1.5 bar WOT. After running for ~10 minutes, it seems to cap/hold at 1.1 bar WOT again, but just after properly warming the engine/oil temps to get on the loud pedal, even ~75% throttle will hit 1.3-1.5 bar. The weather is a little colder here, but last winter I never passed a spike of 1.2 bar. The boost/pull and throttle response is definately stronger and more responsive, which I love, but I do not wish to cause engine/tranny damage. Could this just be due to the aftermarket DV's, or do you think my wastegates may not be opening properly?

I do not wish to jeopardize my engine or tranny, so I'm looking for opinions on if this is a safe situation or I should look at retuning or the wastegates? I (incorrectly) told Switzer we had 91 octane, but actually use 93 octane. What difference does this make with respect to the tune? I guess I'll call Switzer and see what he says too, or maybe he could chime in here.

Thanks, and here are some other threads I found on the issue:

https://www.6speedonline.com/forums/...-pump-gas.html

https://www.6speedonline.com/forums/...uch-boost.html

https://www.6speedonline.com/forums/...rging-fix.html

 

Probably a hose to the wastegates not working on one or both sides. Check to be sure they are connected to the turbos and didn't blow off there as well or on the N75 side.

 

OEM Wastegates will not be able to run 1.3 bar or more.. who did the install... something is wrong only after you put in the parts.... check your installation..

 

Midwest Auto Group in Columbus, OH did the install.

 

Time for a boost leak test! Most likely a hose is off somewhere!

 

Mike, sorry to hear more issues! Keep me in the loop as to what the problem is. Looks like another loaner

 

This would be the third boost test, after the initial loss of boost pressure. MAG gave me the car back after the first drop off after replacing the N75 valve and it was no better, still .5-.6 bar. Dropped it off a second time and they had it for a long time (thier boost tester was supposedly broken and they borrowed one to eventually find the leaks in the hoses). I've got a bag full of the old hoses that were replaced, so it sounds like they perhaps just did not connect something properly this second time around (when they also installed the DV's). I think I'm at about $500 in labor and parts costs so far, which includes $115 labor for the DV install.

Tony, thanks for the comments (and others too). I'm not really sure what I'm doing in this area so will probably just take it back in. I'm sure/hope there will be no extra labor charge as this will be my third trip back since the initial boost loss. They owe me a upgraded loaner! FWIW, I've only had MAG do a couple things on the 996tt (ignition switch lock repair, belt/tensioners maintenance) and they are normally top class in speed and getting things done right. This boost issue is a little more complicated, but it's disappointing that it will take at least 3 trips, with the second one lasting over 2 weeks they had the car. It's also disappointing that they knew and told me it was spiking at 1.5 bars and diid not mention that this is way to high, even for a tuned car. If I did not read this forum, I'd probably eventually end up with a very serious problem.

Bux996tt, when she's back up and running properly, I'll give you a ring and we can go on a spirited cold weather drive soon. Anyone else near Columbus, OH is welcome to join.

 

Yep, def don't want 1.5 - not enough fueling to keep it safe for sure and other things... Lean mix and high boost = boom $$$

They should have leak tested it after they replaced all that stuff as well... Either they have something hooked up wrong or a leak.

Hope you get it sorted soon!

 

disconnect your n75 valve from ecu...after that you see your base boost ..with stock wastegates 0,5 bar ore with 1 bar wastegates 0,9 bar +/- 0,1bar.. more shows a failure behind the lines of n75 valve

check wastgates....(......small leak in membran under part throttle)
check n75 valve and installation

ore do you have a overboost only between shifts? in this case the diverter valves are the reason

 

I went out for a long drive today and experienced the following:

1. Never saw higher than 1.3bars now, at any time, but did not WOT until after 10 full minutes of city driving and previously the 1.3-1.5 spikes were between 5-10 minutes after starting the engine IIRC. That could have just been coidence.

2. From stop, launches through first and second gear only once briefly hit 1.2 bar, and 90% of the time were pulling at 1.0-1.1 bar. However, immediately upon entering third, there were initial spikes to 1.2-1.3bars for a second or two before falling back to 1.0-1.1 bar for the vast majority of the pull in third (and I always run out of runway before I can do much with fourth ).

3. Driving in second gear, then WOT, never spiked above 1.2, and 90% of the time spiked at 1.1 and pulled at 1.0-1.1 through the rest of second.

4. Driving in third gear, then WOT, had consistent, initial hits of 1.3 bar which lasted for about a full second before dropping to 1.1 bar again.

5. I can't remember the results of highway driving in 4th/5th then WOT, but I believe the results were the same as third gear, with brief spikes in to 1.3bar then the rest of the pull level at 1.0-1.1 bar.

Does this still sound like too much boost? I sure it's not somehow correcting itself, but I never saw 1.4 or 1.5 bar at all today, but again, the engine was running for 10+ minutes of city driving before I got aggressive and last time the 1.3-1.5 bar readouts were only in the 5-10 minute engine on time frame.

Finally, I have two old hoses that were replaced, along with the old DVs that were replaced:

1. 996.110.681.73 - this hose has a large split in it and clearly was the initial leak that caused loss of boost to .4 bar max.

2. 996.110.683.73 - I think this is the Y hose, right? I cannot see any visible cracks/leaks in it. I plug the ends and blow in it and it holds 100%, so I'm not sure whey they removed/replaced it.

3. I also have the old DV's.

Can someone link to a picture guide showing where the N75 valve and wastegates are. I really don't know what I'm doing in this area, dont' have a pressure tester, and certainly don't have small hands. I can probably take it back to MAG and have another diagnosis free of charge at this point, but I'm sure they'll find a way to charge a hundred or so in "misc shop charges" also.

If I continue never topping 1.3 bar except for spikes in 3rd higher gears initially before leveling off to 1.1 bar, is that still unsafe to drive long term on 93 octane with tune/exhaust/dvs?

 

[QUOTE=MikeR397;3351929

Can someone link to a picture guide showing where the N75 valve and wastegates are. I really don't know what I'm doing in this area, dont' have a pressure tester, and certainly don't have small hands. I can probably take it back to MAG and have another diagnosis free of charge at this point, but I'm sure they'll find a way to charge a hundred or so in "misc shop charges" also.
[/QUOTE]

I suggest you do not dabble on your own.. you can just mess everything up...
Take it to a place that works on P car 996 TTs...
Yes You need a pressure test from the turbos.. and good luck getting a shop to do it right...

here read this up a little so you get a grasp on what's up...

markski

https://www.6speedonline.com/forums/...cs-inside.html

 

Hum. From stop, i had 1.0-1.1 bar until second, which only rarely touched 1.2 bar immediately upon entering second then leveled at 1.0-1.1 bar pulling the rest through second, then immediately shifting into third was when I had 1.3 bar hits then falling off to 1.0-1.1 bar the rest of the pull.

Also, driving in third, then WOT would also spike to 1.3bar for a second or two (no gear change) before leveling off to 1.0-1.1 bar for the rest of the pull through third.

btw, the car is a tiptronic.

The DV's I had installed (voluntarily, no evidence of stock failures) were lightly used, Evo black billets, Mag supposedly inspected first and said there were in good working order. As I said, DV's went on at the same time they put the replacement hoses on as they said they'd do it for just 1 hour labor charge for the DV install and I was never going to get my large hands in there without going mad.

ETA: Thanks for the link Marski! I'll check it out. I like to be informed and know what is going on, but I'm not so patient or great at actually doing the fixes myself. Oil changes are the extent of my typical involvement, and an occasional brake change. MAG http://www.magcars.com/index.htm is the big exotic place in Columbus and certified porsche dealership/service, so they should be able to do things right. Maybe third time is a charm if people think I'm still having too much boost (see above post) at 1.3 bar spikes in third for a second or two. There are some indy options too, but MAG always is reasonable for me and I like getting the loaners for a change.

 

Didn't you just come back from a shop with this issue soon after...... if so then get it fixed right...

 

Or even the plug for the valve. Most guys take the wye pipe off to replace the F-hose and DV's. Bring the car back to who ever did the work.

 

I took the car back and more tests with no resolution. Wastegates are opening fine, hoses to them are holding pressure. I'm still getting the same symptoms I've mentioned above.

The issue is either the diverter valves I put in (stock ones were still fine) OR the timed valve (part 99660515500) that they replaced the first time...let me know what you think here...

1. 1.5 years with tune always proper 1.1 bar peaks/pulls with stock DV's.

2. The diverter hose breaks and I get a max of .4 bar.

3. First time I take the car in, they did not catch the hose split and instead ONLY changed the timed valve (99660515500), and instantly (still with the split hose) it was at .6 bar rather than the .4 bar, with occasional spikes at .7 bar. Obviously still low.

4. I take the car back in, this time they find the split hose (diverter hose, attached to the DV's with a big split). This was replaced, along with the Y hose (which was fine and I don't know why replace). Also, used (but supposedly fine functioning) evom black billet DV's were installed to replace the stock DV's that still were working fine. The car is now doing the current 1.3-1.5 bar spikes.

5. Today I take car back, wastegates are opening, no detected leaks to wastegates.


My guess is that it can only be either the DV's I installed (but spikes are not just between gear changes, 1.5bar spikes occur in 3rd gear WOT with no gear change (see above)), OR it's that new timed valve they put in the first time before finding the split hose, which I'm told controls the wastegates. It's frustrating b/c they should have easily found that BIG split in the diverter hose with a proper pressure test, but I guess thier pressure tester was broken and they missed it so now there are more variables and they are getting fed up with me it seems like. I told MAG it was a tuned car, but I guess the mechanic didn't know, saw .7 and thought that was fine. I was explicit it should be pulling 1.1 bars, but still got it back that first time at .6-.7, then the second time at 1.1. This is probably my last shot there or I'll have to take it elseware labor bills are really adding up .

I've called Switzer and he's getting back to me. MAG wants to flash the car back to stock to diagnose, but I think that is a waste and not a potential issue. Mag has the car now and wants to know what to do by tomorrow afternoon. Should I put the stock DV's back in and also put the original timed valve back in? It's 1.5 hours labor whether I do both or one. I'd like to keep the aftermarket DV's, but if they are the problem it's getting annoyingly expensive to keep doing this.

TIA. This has been very frustrating 30 days++ with no resolve yet from an original simple boost hose leak that they failed to diagnose properly the first time and now it's overly complicated.

FWIW, otherwise MAG has always been great wrt to servicing.