[MysticRob]

Originally Posted by milfriez

...Something to add today. Much colder out today, engine wasn't very warmed up, and I was holding RPM in 4th gear, there was a sudden BOOST and SHARP drop off. Not a back and forth motion, but as dumb as this sounds, almost like a NOS shot for a second, then just died.

You've already said you're not hitting boost targets till much later in the rpm band, and you haven't replaced the vacuum lines to the wastegate actuators, so I'm wondering some things:
1. Why haven't you replaced the lines to the actuators?
2. What size vacuum lines did you use for the rest of the vehicle?
3. Are you sure you replaced ALL other vacuum lines and done it correctly?
4. Any broken nipples on connections, like possibly the intake or the vacuum canisters?
5. Have you tested the boost solenoids for proper operation AND vacuum line routing? (did you maybe test incorrectly?)

I used 3.5mm lines like most everyone else here. Getting to the actuators is difficult but by no means impossible with a bit of WD40 on the ends of the nipples. I ask about the lines because it reminds of someone else that had similar issues, especially with boost seemingly coming on much too late, as if the vacuum built to a point where it could then overcome whatever leaks were inherent in the faulty system. I can't remember but I swear it had something to do with the vacuum system.

If your coils and plugs were bad I wouldn't expect to see a sudden rush of power as if the problems with those various parts just suddenly fixed themselves, you know what I mean? If parts like that are indeed causing a problem they aren't likely to magically repair themselves for short periods of time.

[milfriez]

Originally Posted by MysticRob

You've already said you're not hitting boost targets till much later in the rpm band, and you haven't replaced the vacuum lines to the wastegate actuators, so I'm wondering some things:
1. Why haven't you replaced the lines to the actuators?
Just a matter of finding time to do it, between letting the car cool overnight, 3 kids and sports, 50hrs week work it's a bit hectic. That and I heard it was near impossible to get to the front Turbo.
2. What size vacuum lines did you use for the rest of the vehicle? 4mm - I *thought* i read on here or N54tech that the 3.5mm was extremely tight fitting and hard to get on at times. I know its OEM size, but I went with 4mm. Would that have a negative effect?
3. Are you sure you replaced ALL other vacuum lines and done it correctly? The lines to the WG's are the only ones not done. I followed the guide that was on here, with the color-highlighted areas. (You're making me question myself, but 99% sure those are the only ones remaining)

4. Any broken nipples on connections, like possibly the intake or the vacuum canisters? 100% sure those are not broken, checked and rechecked them plenty of times. Also took care when taking off the old lines, to just cut them off and not tug on the fragile plastic.
5. Have you tested the boost solenoids for proper operation AND vacuum line routing? (did you maybe test incorrectly?) The lines were holding correct pressure when I hooked up the vacuum gauge. I also adjusted WGDC in the JB4 and it increased accordingly. That being said, this is my first time having to deal with plumbing/boost/vacuum crap, so very real possibility that I wasn't doing it correct. Again, I followed the guide on N54tech for testing vacuum, I did not do the road test with vacuum line hanging in window, or the syringe test.

I used 3.5mm lines like most everyone else here. Getting to the actuators is difficult but by no means impossible with a bit of WD40 on the ends of the nipples. I ask about the lines because it reminds of someone else that had similar issues, especially with boost seemingly coming on much too late, as if the vacuum built to a point where it could then overcome whatever leaks were inherent in the faulty system. I can't remember but I swear it had something to do with the vacuum system.

If your coils and plugs were bad I wouldn't expect to see a sudden rush of power as if the problems with those various parts just suddenly fixed themselves, you know what I mean? If parts like that are indeed causing a problem they aren't likely to magically repair themselves for short periods of time.

I appreciate everything you wrote. Anything that gets me thinking or moving towards a solution is good. I just want to get this back to where it was at stock with only the JB4. It sure seemed to move. Now, there is not much of a noticeable difference between Map1,2, and 5. All feel as if they are boosting about the same and not matching target until about 4k. The nail in the coffin is this ridiculous surging though at low RPM low speed.

This morning, I came to a rolling stop at a stop sign, and in 2nd gear lightly gave it some gas and it jerked forward quick, then settled back into its normal acceleration. It was a strange sensation, and I was sure it would have tossed a code, but so far nothing. If this crappy rain ever lets up, i'll try and get out there and get to the lines on the WGs. Would having mixed IDs of tubing cause strange issues?

[MysticRob]

Originally Posted by milfriez

I appreciate everything you wrote. Anything that gets me thinking or moving towards a solution is good. I just want to get this back to where it was at stock with only the JB4. It sure seemed to move. Now, there is not much of a noticeable difference between Map1,2, and 5. All feel as if they are boosting about the same and not matching target until about 4k. The nail in the coffin is this ridiculous surging though at low RPM low speed.

This morning, I came to a rolling stop at a stop sign, and in 2nd gear lightly gave it some gas and it jerked forward quick, then settled back into its normal acceleration. It was a strange sensation, and I was sure it would have tossed a code, but so far nothing. If this crappy rain ever lets up, i'll try and get out there and get to the lines on the WGs. Would having mixed IDs of tubing cause strange issues?

As long as any given vacuum line doesn't collapse, it doesn't matter what the inside diameter is, or if there are different IDs within the same system, as long as the lines all attach securely to the connectors and don't freely move or leak.

I really liked the snug fit of the 3.5mm lines. They didn't rotate around the connectors at all. I've read here many times that 4mm is too big and may cause sealing problems with the various connections, though I can't tell you for certain having never used that 4mm size.

Do your lines rotate easily around the fittings at all? I know others have used 4mm here but I'm uncertain if they had issues or not after a while. Something else to keep in mind is manufacturer tolerances. One company's 4mm might not be the same as another company's 4mm.

[milfriez]

Originally Posted by MysticRob

As long as any given vacuum line doesn't collapse, it doesn't matter what the inside diameter is, or if there are different IDs within the same system, as long as the lines all attach securely to the connectors and don't freely move or leak.

I really liked the snug fit of the 3.5mm lines. They didn't rotate around the connectors at all. I've read here many times that 4mm is too big and may cause sealing problems with the various connections, though I can't tell you for certain having never used that 4mm size.

Do your lines rotate easily around the fittings at all? I know others have used 4mm here but I'm uncertain if they had issues or not after a while. Something else to keep in mind is manufacturer tolerances. One company's 4mm might not be the same as another company's 4mm.

I haven't had any feel as if they are going to fall off or rotate easily. They are a little bit easier to remove, but still require some force and twisting to get them to release. I went with the one that was being tossed around a lot on here. It's the Verocious motorsports platinum cured 4mm.

I suppose I could step down to the 3.5, but I think replacing the lines going to the WGs and any other areas that I may have overlooked might be the route to go first. I'll see if somehow I can get to the rear turbo, and then Ill have to try and figure out how to get to the front one also.

[james92]

Originally Posted by milfriez

Something to add today. Much colder out today, engine wasn't very warmed up, and I was holding RPM in 4th gear, there was a sudden BOOST and SHARP drop off. Not a back and forth motion, but as dumb as this sounds, almost like a NOS shot for a second, then just died. Its really making me feel like something is just not measuring correctly and is messing with values. Which values? I couldn't tell ya, fuel pressure? ignition? AFR? boost? Could symptoms like this be from dirty/contaminated MAP sensors? Like I said, it seems like all this bucking was exasperated after replacing HPFP, low pressure sensor, high pressure sensor, and injectors all at once.

I've been experiencing something very similar to this for some time now and am interested to see that it may not be specific to those using MHD.
Here are two logs of when this sudden surge was felt - throttle position shots up when accel pedal remains near enough the same.
LINK1 4th gear @ 2811rpm and 5th gear @ 2820rpm
LINK2 @3224rpm

First noted this on MHD v7 and have since had hybrids, inlets, LPFP stg2 and a map from Pureboost and am still encountering this surging issue as well as the occasional bucking. Our issues may be completely unrelated but the above logs might give some sort of idea as to what is happening. Very interested to know if you get to the bottom of it!

[Khalidbiary]

Hey! Did you ever fix this?