Not boosting properly after darintake and bi pipes?
10-10-2016, 04:41 PM
#1
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Not boosting properly after darintake and bi pipes?
Long time listener, first time caller....
03 a6 BEL 2.7t tip. stage 1 ECU, forge diverters. All else stock except for the recent darintake mod and larger bi pipes
So I did the darintake and put some bigger bi pipes on and now it seems like it doesnt build boost like it used to. Kind of hard to explain with it being a tip tranny. Before, at around 33% throttle, boost would come on strong at 3-3500 rpm. Now, I have to be at 75% or more to hit full boost. It still is there, but it *seems* like I have to push the throttle down much further to get there. At first i though it was a boost leak so I tightened all the intercooler piping and took it for a spin. Didn't really change anything. Is it possible that the n75 valve is the culprit? Maybe since there is more available air, the car doesnt need to boost to deliver the requested throttle position at lower rpm? Basically before, in order to match throttle request the car needed to boost, and now, with the available air, iits doing the same work n/a? Is that reasonable? I don't have vag software. Only *diagnostic* tool is a p3 vent gauge and its difficult to see where I'm hitting full boost when full throttle. Any advice? Am i crazy? lol thanks in advance for any help/direction.
03 a6 BEL 2.7t tip. stage 1 ECU, forge diverters. All else stock except for the recent darintake mod and larger bi pipes
So I did the darintake and put some bigger bi pipes on and now it seems like it doesnt build boost like it used to. Kind of hard to explain with it being a tip tranny. Before, at around 33% throttle, boost would come on strong at 3-3500 rpm. Now, I have to be at 75% or more to hit full boost. It still is there, but it *seems* like I have to push the throttle down much further to get there. At first i though it was a boost leak so I tightened all the intercooler piping and took it for a spin. Didn't really change anything. Is it possible that the n75 valve is the culprit? Maybe since there is more available air, the car doesnt need to boost to deliver the requested throttle position at lower rpm? Basically before, in order to match throttle request the car needed to boost, and now, with the available air, iits doing the same work n/a? Is that reasonable? I don't have vag software. Only *diagnostic* tool is a p3 vent gauge and its difficult to see where I'm hitting full boost when full throttle. Any advice? Am i crazy? lol thanks in advance for any help/direction.
10-11-2016, 10:46 AM
#2
I still suspect vacuum or boost leak. Your darintake and bipipes should not make a difference, unless you got rid of the throttle boot leak and the renewed pressure opened up another leak. There is a simple boost pressure tester diy. http://www.vaglinks.com/Docs/Audi/C5...ure_Tester.pdf
Test all the check valves with a MityVac or at least mouth blow/suction. Double check BPV's for sticking, f hose (in front under intake pass side), hoses going to/from N249 and hoses to from N75.
Once all that checks out, the N75 might be the culprit. FYI, I once threw a new N75 in with no change...hate to chase by throwing parts.
Test all the check valves with a MityVac or at least mouth blow/suction. Double check BPV's for sticking, f hose (in front under intake pass side), hoses going to/from N249 and hoses to from N75.
Once all that checks out, the N75 might be the culprit. FYI, I once threw a new N75 in with no change...hate to chase by throwing parts.
10-12-2016, 10:38 AM
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I am seeing normal vacuum pressure, but of course, that is a different world than a boost leak. Ill look in to that. I had this set of bi pipes on ince before but took them off due to it blowing off under boost at the tbb. So, i wouldnt really doubt it if that is the issue. I had cheap aftermarket silicone tbb, now i have a much better quality one. Just wanted some opinion on other possibilities before pulling them out again. Thanks bud.
10-12-2016, 01:19 PM
#5
Since you indicate full boost at 75% - WOT, your BPV's might be bleeding boost via vacuum to BPV's from N249. You might try bypassing the N249 and connecting the BPV's directly to intake vacuum/boost to rule out N249. T a line from fuel pressure regulator to BPV feed at metal pipe and plug hose from N249 to metal pipe on bracket to preserve vacuum to fuel evap system. Take your time and recheck everything.
More air flow does not have anything to do with it. Really should make the boost build easier.
More air flow does not have anything to do with it. Really should make the boost build easier.
10-12-2016, 04:42 PM
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I think ill start with a boost leak test. That will give me the biggest bang for the buck i think. Then ill work on inspecting the check valves, then ill try the n249 bypass. Then maybe a n75. Probly throw in a maf cleaning as well (i did "disturb" it a bit). If none of that gets me anywhere, i guess it could just be an extraordinarily timed turbo failure lol. Car ran out great before, but i couldnt just leave well enough alone...
Hopefully i can try some of it this weekend if the weather holds up.
10-18-2016, 12:59 PM
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Most likely the least technical advice you'll get, but how difficult would it be for you to go back to the old setup ? Did you throw away the old parts ? If it's not too time consuming, put them back and see if the car returns to normal
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10-18-2016, 03:51 PM
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I still have the old parts and i could pretty easily put them back on. Im starting to think its all in my head..
I did the boost leak test and didnt find anything. Going to need to research a little more on bypassing valves before i commit. Dont want to mess things up as this is my only vehicle.
I did the boost leak test and didnt find anything. Going to need to research a little more on bypassing valves before i commit. Dont want to mess things up as this is my only vehicle.
10-18-2016, 05:25 PM
#9
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Yes. You're crazy and apparently incompetent. Take get car to a mechanic
Long time listener, first time caller....
03 a6 BEL 2.7t tip. stage 1 ECU, forge diverters. All else stock except for the recent darintake mod and larger bi pipes
So I did the darintake and put some bigger bi pipes on and now it seems like it doesnt build boost like it used to. Kind of hard to explain with it being a tip tranny. Before, at around 33% throttle, boost would come on strong at 3-3500 rpm. Now, I have to be at 75% or more to hit full boost. It still is there, but it *seems* like I have to push the throttle down much further to get there. At first i though it was a boost leak so I tightened all the intercooler piping and took it for a spin. Didn't really change anything. Is it possible that the n75 valve is the culprit? Maybe since there is more available air, the car doesnt need to boost to deliver the requested throttle position at lower rpm? Basically before, in order to match throttle request the car needed to boost, and now, with the available air, iits doing the same work n/a? Is that reasonable? I don't have vag software. Only *diagnostic* tool is a p3 vent gauge and its difficult to see where I'm hitting full boost when full throttle. Any advice? Am i crazy? lol thanks in advance for any help/direction.
03 a6 BEL 2.7t tip. stage 1 ECU, forge diverters. All else stock except for the recent darintake mod and larger bi pipes
So I did the darintake and put some bigger bi pipes on and now it seems like it doesnt build boost like it used to. Kind of hard to explain with it being a tip tranny. Before, at around 33% throttle, boost would come on strong at 3-3500 rpm. Now, I have to be at 75% or more to hit full boost. It still is there, but it *seems* like I have to push the throttle down much further to get there. At first i though it was a boost leak so I tightened all the intercooler piping and took it for a spin. Didn't really change anything. Is it possible that the n75 valve is the culprit? Maybe since there is more available air, the car doesnt need to boost to deliver the requested throttle position at lower rpm? Basically before, in order to match throttle request the car needed to boost, and now, with the available air, iits doing the same work n/a? Is that reasonable? I don't have vag software. Only *diagnostic* tool is a p3 vent gauge and its difficult to see where I'm hitting full boost when full throttle. Any advice? Am i crazy? lol thanks in advance for any help/direction.
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