Help with high WGDC with PS2 PWG Built N55

[Alturiak]

I'm chasing a high WGDC issue with my car and wanted to consult this forum for ideas of what it is that could be contributing to it (or causing it). To start, I have a built N55 with forged internals, 9.5:1 compression, VAC stage 3 CNC ported head, PR coils, and full PI setup running my PS2 turbo. The motor is basically all new and I'm just dialing in the pump gas (91oct here in CA) tune with Justin at Twisted Tuning before moving onto the high powered E85 map.

He has told me many times the WGDC is way high for the boost being made, and I've told him it's always been high since I first got the turbo (99% required to hit 26psi) and because the turbo was new at the time and no one ever mentioned it to me when I was dialing in logs I assumed that was normal and correct for the turbo, since I knew ~25psi was pushing its limits anyways and so pegging the WGDC to hit that boost made sense to me.

Flash forward to now and the car will be going as high as 90% WGDC at 14psi and it's not raising. The shop that built it, Castro Motorsports, has told me several times they pressure checked it and said it was good (I don't know if that's a standard smoke test at 5psi, or if they really checked it at 25psi), so presumably the car doesn't have a boost leak. I recently put on Pure's upgraded heavy duty wastegate actuator and it had no improvement. I'm now in the next couple weeks going to switch over to the new Turbosmart BOV to replace the GFB DV+ and hope that makes an improvement.

I'm hoping the BOV replacement solves it but I wouldn't count on it. I'm just kinda stumped on what else would be causing it? There's no way I can start pushing E85 tunes and really high boost with the way it currently is. Since starting to address this I've replaced the boost solenoid with a Genuine BMW one, both O2 sensors replaced, DP gaskets, hpfp. I was dealing with bad AFRs which I feel I'm still dealing with as well, so any input on that front is appreciated as well.

Here are logs from my dyno day at EAS, with a log from back when I had a JB4 for reference with WGDC. Car put down a best 350whp in 5th and ~315whp in the other 2 attempts in 4th. Really disappointing for a built motor as I'm told it should have been well over 400whp easy for everything that's done to it

datazap.me | Alturiak | N55 PS2 high WGDC

datazap.me

 

[bandook]

Did you get it sorted? If not, how did you set your wg actuator? Should be between 6-7 inhg fully closed. I had mine set at 9-10 and was only hitting 22 psi. Readjusted and was hitting 26-27.

 

[Alturiak]

Unfortunately not. I replaced a bunch of gaskets, fixed frayed connectors and a lot of other things I found wrong that Castro left that way. I did get the new bov on though which has been fun, and I did get my AFRs sorted out. Turned out to be an exhaust leak after all.

As far as my WGDC goes though I got no improvement. From my latest logs it seems that around 16-18psi is when it starts leaking because it climbs rapidly til it's maxed and the boost line will gradually decrease even with the WGDC at 100%. For my wastegate actuator, I actually set it between 5-6inHg to bias it towards less WGDC needed but none of that has been seen because it's got a leak somewhere. I purchased a leak tester so the new shop I'm taking it to on Friday will be able to smoke test it and pressure test it properly. I'm hoping those tests will solve the problem. I'll update after the visit with the results

 

[wheela]

Did you try checking the vacuum chamber in your valve cover for oil? I know they can crack underneath and suck in oil and loose vacuum through the crack. So you'd need more duty cycle to hit the same wastegate position/boost. If I recall correctly I think you had a relatively new valve cover, but checking for oil in there is relatively easy and would at least help rule it out since no leaks are turning up anywhere else.

 

[Alturiak]

Hmm I haven't checked that. The valve cover was replaced a bit less than 25k miles ago with a Genuine BMW one, so I've had no reason to suspect that as a possibility but it wouldn't hurt to check. How do I go about checking? Am I simply just looking inside the PCV exit port, or somewhere else?

 

[wheela]

I can't find the post, but over on the other forum a guy showed how to check. If I recall correctly, he just removed the line from the vacuum pump to the valve cover (#2 in the attached picture), and then you can look down into the vacuum reservior in the valve cover to check for oil inside. I've been meaning to check this on my car too, but i've been too lazy, haha! This image is from vespa's PCV valve thread.

 

[Alturiak]

Ah okay, I know exactly the port. I didn't notice anything peculiar while I had the engine bay apart a couple weeks ago, but I wasn't also staring directly down that port either. I'll give it a look later today and let you know.

 

[Alturiak]

Quick Update: Car was finally smoke tested and at not even 5psi there was smoke spewing out of where the auxiliary injectors connect to the PI manifold! I've ordered oversized o-rings that should work and be more than adequate to seal that up and then I'll be back to continue smoking it and work up to the pressure test. The good thing is I could not find smoke coming from any connections between the turbo and intake manifold, which is nice since that was the area I had focused on. I had never even contemplated that the injectors could be leaking smh. Will update further after the new o-rings are in!

 

[miksebik]

Well, I am helping with a build of F30 335i Pure turbo PWG, just gas, no PI, no meth. The car behaves pretty wild and to be honest, I am disappointed. Last year, the turbo just blew, as it was maxed around 100% WGDC and 21 PSI. Fortunately Pure accepted the claim and repaired it.
Now it runs around 90% WGDC, 21,5PSI target. The car is being tuned by Motiv, we measured 520HP on a Superflow dyno but the car threw various codes. Since last revision, the car still boosts around 21PSI but now slowed down so that it makes 100-200kmh in 9.5s.

 

[Alturiak]

Another update: the new oversized o-rings from McMaster came earlier this morning so I threw them on the injectors with a bit of chemplex to help seal and lubricate them and took the car for a couple quick logs. In 4th gear at 6k rpm it was boosting 1.6psi higher than before the o-rings were replaced, and in 3rd it was boosting about 1psi higher. So a definite improvement as far as boosting goes, but WGDC is still maxing out at the end of the gear so I'll be back at the shop on Friday to continue smoke testing it. I'm hoping we'll be able to actually pressurize the system above 5psi this time around but we'll see. Fingers crossed! Will update after the next visit, but I'm stoked to be on the right track to getting this thing sorted!

 

[Alturiak]

Took the car for more smoke testing on Friday, and found the injector fix was resolved. With having the smoke plumbed into the turbo inlet and the oil cap off, all the smoke was just pouring out of the oil fill hole. Since it was low pressure I felt it was safe to cap off the oil fill and see where it comes from next. After a couple minutes smoke was pouring out of the turbo inlet/diverter valve/turbo outlet area. I couldn't tell exactly which connection was the culprit since it's so crowded in that spot, so I'm tackling the o-rings on the Pure high flow inlet and the o-ring on the turbo outlet pipe. I pulled the Pure pipe to inspect it and found the o-rings are totally shot (worn down and cracking) and since I'm working in that area anyways I'll replace the TIC chargepipe o-ring as well, just currently waiting on Fred from ER to get back to me on the O-ring groove dimensions so I can order something. I ordered a VRSF o-ring just in case it works (which I'd think it should but neither company wants to confirm that for me lol). Will update once the new o-rings are on the car!

Also when I'm done with this whole journey I will compile a list of all the o-rings I've done and their respective McMaster Carr part numbers to share with the community. It's ridiculous for vendors (not going to name names here) to charge $25 for 6 intake manifold o-rings. Also the o-rings I've been selecting will have higher temperature capabilities and better materials if available (i.e. silicone o-rings over buna-N and such). If anyone has any questions so far just let me know and I'll be glad to help

 

[Alturiak]

Figured I'd update this since it's been a minute. In short, I'm leaning towards my PS2 is worn out/leaking and that's what is causing my WGDC issues. When I try to smoke test from the pure high flow inlet (with oversized o-rings so I know they are sealing) I still see smoke coming from that area. The only part I can definitively say it is not leaking from is the turbo outlet connection. This leaves either the diverter valve (TurboSmart BOV) connection, inlet (which is unlikely since that becomes fairly difficult to push in with the larger o-rings and grease), or somewhere else on the turbo that is not holding any type of pressure. I cannot even get to pressure testing because that connection can't hold the <5psi smoke test pressure. I'm going to upgrade to the SpeedTech EFR kit in a few months and eliminate the turbo being worn out from the equation.

So I have pretty much stopped pursuing smoke testing for the time being, and am now looking at a bigger issue. I got an oil report back from BlackStone that said my wear INCREASED from the last report. It's a fresh motor build so it should if anything have decreased a good amount on this last oil change (2nd change after breaking it in). I feel this is because of the cold start issues the car has had where only on cold starts, it'll start right up and stay alive for a second and then stall/die. I end up having to manually hold some RPMs to get it to stay alive and after a few seconds of holding it is fine. After the car is warm it starts up and stays on no problem. No codes, nothing looks weird in logs, literally all parts in the system are new (lpfp, fpr/filter assembly, fuel lines, hpfp, DI injectors). So I take the car back to Castro Motorsport where it was built to get this sorted, and after a bit he says my IAT readings are super high and throwing fault codes and the cold start problem is there when these faults are present. By high readings, I mean like 150F+ on a cold start where ambient is maybe 70F. Has anyone had this happen or seen this happen before? He said he tried swapping all temp reading sensors (MAF, TMAP, MAP) and nothing changed. He started suggesting its a DME issue and maybe the DME is bad, but that's a pretty expensive fix for what seems like a guess to me. I found someone else with a similar IAT fault issue, but they never posted what the solution was. Could it be possible my DME is cooked? I didn't think they were common failures on our cars...

 

[wheela]

Sorry to hear your still having issues. It sounds like you've ruled out a boost leak pretty well. How much investigation have you done on your vacuum system? If your vacuum pump isn't pulling hard enough vacuum, or if you have any leaks in the system, then you'll get less vacuum to the wastegate canister at a given wgdc%. So there will be less force to counteract the WG spring, and force of exhaust gas pressure against the WG flap. So you'll need more wgdc% to hit the same WG position / boost. The auxiliary vacuum that controls the WG also controls the exhsust flap, so a weak vac pump, or leak anywhere in that system could contribute to your problem.

Attached is a graph I found in a BMW n55 tech brochure. It describes the vac pump as two stage: a high capacity one for the brake booster, and a lower capacity one for the WG & exhaust flaps. I also attached a sketch of the vac layout.

Do you have any tools to verify what level of vac is present in your system when the car is running? If it's low you could have a leak somewhere, or potentially a weak vac pump, though I don't know how common that is.

For that temp issue, I have no idea. I've read that these cars can start acting really buggy and throw weird codes when the battery is getting low, so I'd probably start there if you haven't yet.

Hopefully it's not your dme. But if it is your dme, or a low battery, maybe that also could explain your wgdc issue, if it's impacting the actual cycle going to your boost solenoid? IDK.

Btw, those speedtech efr kits look awesome! If you end up going that route, would you mind following up with how it goes? I reached out to them this last August, and he couldn't tell me when the e-chassis efr kit would be available due to limited interest.

 

[wheela]

Also, would you mind sharing what size o-rings you used for your pure inlet, and the turbo outlet? I have the vrsf inlet, and this happened during installation, so I'll be finding better orings...

 

[Alturiak]

Sorry @wheela, it's been a minute since I've been on here. If its not too late for you, I'll share the sizes I was experimenting with. I have to note though mine were used on the Pure Inlet, so hopefully VRSF has the same groove dimensions. Off McMaster Carr, I got the best fit with a 2.4mm wide, 47.6mm ID Buna-N o-ring. However, the groove really should be opened up a little, because getting the tube in is TOUGH afterwards lol.

I'm working on a whole new intake setup right now that's an N55 version of the N54 hotside/turboside intake system, that uses the CTS Turbo inlet, and I can confirm that thing has a great seal to the turbo

 

[wheela]

No worries, thanks for responding! I'll look into those o-ring sizes

 

[wheela]

Random question - do recall if the pure heavy duty wastegate actuator was the same physical dimensions as the oem unit? On their website, they claim it gives about 2psi more that stock for a given duty cycle%. I wasn't sure if they were doing this with a larger diaphram area (larger casister diameter?), or a softer spring constant, other? Nobody seems to sell new oe n55 wastegate actuators. Obviously the pure unit is designed to work for an n55 turbo, but i'm still curious if the outside dimensions are any different than a stock unit.

By the way, I like your new thread with that turbo side inlet!

 

[Alturiak]

I'm pretty sure they're just swapping the spring on it, as it is exactly the same dimensions and looks oem compared to the actual oem wastegate actuator. Actually when I got it, I was a little concerned I was only sent an oem unit haha. And unfortunately for my situation I didn't see a big improvement in my logs to reduce WGDC, so take that as you will.

And thanks! Just tried out a new tune from Twisted and it's almost dialed in Can't wait to be running full E85 and high boost again!