Surge killing turbos

[135iTX]

Everyones car is different. I have seen 3 different N54s running three different BOV springs successfully. Springs are cheap, go with the lightest one that closes the BOV at idle - if its open a bit not a big deal, just shim it with a washer or two and youll be good to go. Not sure why this debate is getting so "scientific" lol.

 

[doublespaces]

Everyones car is different. I have seen 3 different N54s running three different BOV springs successfully. Springs are cheap, go with the lightest one that closes the BOV at idle - if its open a bit not a big deal, just shim it with a washer or two and youll be good to go. Not sure why this debate is getting so "scientific" lol.

You'd think it wouldn't need to be. Vacuum at idle is not representative of vacuum while driving and decelerating so I've never even liked that comparison. We don't boost our car while parked so the vacuum reading there is only a vague measuring stick at best. We should just use a light spring in general, the vacuum reading at idle is largely irrelevant unless your car has some issues. If a light spring can indeed account for more surge than a heavier one in a healthy environment, I am genuinely interested to know in which situations. If a 6 psi spring is used, outside of a 6.1 psi pressure differential between the top port and the charge pipe, there really isn't anything to be concerned about.

 

[doublespaces]

I just got a reply back from TiAL about their spring chart and how it applies to our drive by wire throttle blade. I rest my case.

Hi, Tyler,

Just based on your feedback, I'm going to address only the BOV spring ratings, as they apply to turbocharged engines, in this email, but there are also elements of our WG spring ratings that overlap. And there is a very different approach to supercharged engines, so if either of these scenarios is what you're addressing, we can circle back to that.

First, and foremost, it's important to remember that the published spring ratings for our BOV are simply the initial opening rate of the valve.

These are standard, repeatable values, so, for example, a Q BOV with a -10psi spring is designed to begin to open at -10psi or -20.4inHG. This rating doesn't really ever change through the life of the BOV; it's not intelligent, nor is it variable, at least within the Q and QR

The spring recommendations are, of course, somewhat general, but they're based on sound principals, and, frankly, we've been producing these devices for a bit now, and we have a good idea of how they work.

They are, admittedly, based upon mechanical throttles, as those designs are still the majority of what is popular in the aftermarket.

Trying to base recommendations upon electronic throttle-equipped cars could pose a huge challenge, as tuning strategies vary wildly, even within stock applications, and even more so for aftermarket tunes, many of which can either eliminate the symptom entirely, or in the case of the recently-popular 'overrun' tunes, can make it far, far more notable.

Another alternative, for many of these applications, is simply to use a different BOV. This is exactly why we developed the QRJ back in 2014.

Since it does not work the same way the Q and QR work, it uses a much lighter spring, but it also operates the valve, and bypasses the charge air very differently than a more traditional valve.

It's also capable of being configured for either atmospheric or recirculated discharge, which makes it better suited for cars that use a MAF control strategy, which accounts for quite a few applications that also use electronic throttles. It provides a much more linear response curve, as it's only actually fully closed under manifold pressure greater than the spring rating.

Because of this, those variations in engine vacuum, such as you described, do not have such a drastic effect on function.

You'll note that, for this reason, we actually do not publish a spring recommendation chart for the QRJ, as we recommend that most customers use the 'default' -3psi spring.

(We do offer other spring ratings for the QRJ, but it was designed around that value, and for most applications, it works quite well.)

When we are consulted, we strongly recommend that customers that have issues, such as you describe, consider using the QRJ rather than the Q. We even make a conversion flange for the QRJ that allows it to fit right on the Q and QR flange, for ease of conversion. But it doesn't mean a Q or QR owner can't make the valve work. It just may require some interpretation of the issue, and adjusting the spring pack accordingly. For applications that don't require recirculation, there really is no reason at all why a lighter spring cannot be used, since the valve being open at idle or under light-throttle conditions doesn't create a functional problem. But applications that do require recirculation can use the QR with similar success.

Hopefully this explains things a bit.

It's important to remember that the spring rating is a fixed opening point, but the spring recommendation varies in some cases. Your feedback has provided some food for thought about perhaps revising our instructions as they apply to spring recommendations, so we will certainly take this into consideration.

If you have any other questions or comments, just let me know.

Best Regards,

Mike Franke

 

[135iTX]

Wonder if machining tolerances in the BOV or maybe one being counterfeit would have anything to do with it.

 

[doublespaces]

I'm sure there are many factors, but they just said the chart is not meant for electronic throttle blades and since we don't recirculate we can run any spring. All this nonsense about needing 10 psi is rubbish.

 

[NoQuarter]

The ability to run a light spring is an indicator of a healthy system with correct plumbing.

I like this statement. It is concise enough to remember and easy to understand.

 

[Rob09msport]

I'm sure there are many factors, but they just said the chart is not meant for electronic throttle blades and since we don't recirculate we can run any spring. All this nonsense about needing 10 psi is rubbish.

Now your generalizing . Majority of bov sold came with 10psi spring and non forum users installed and had no issues. If was wrong vendors would have changed. Now noone is saying that heavy fixes surge and technically 1 psi should not leak. Now our cars are not sensitive because speed density but you still don't want unfiltered air and the electronic throttle blade Is great in our case cause it will allow blow off in the event of a throttle closure. I think everyone is over thinking this and truth is a healthy car should be fine with a 6psi or 10psi leaving room for alot if placebo. I will say to tight Is worse then to light imo.

 

[doublespaces]

Now your generalizing . Majority of bov sold came with 10psi spring and non forum users installed and had no issues. If was wrong vendors would have changed.

They didn't report issues. Doesn't make it the ideal spring to send.

Now noone is saying that heavy fixes surge and technically 1 psi should not leak.

Actually he was alluding to this.

Now our cars are not sensitive because speed density but you still don't want unfiltered air and the electronic throttle blade Is great in our case cause it will allow blow off in the event of a throttle closure. I think everyone is over thinking this and truth is a healthy car should be fine with a 6psi or 10psi leaving room for alot if placebo.

Or we could just tell everyone who isn't sure to get the 6 psi spring and shim it like we are right now. Why would we advise someone to use something potentially too stiff?

I will say to tight Is worse then to light imo.

And knowing exactly where that is can be incredibly difficult for the average person. So why not err on the side of being safe and use a light spring if we are going to insist on atmospheric blow off valves and not something like forge DV? Sending everyone a 10 psi spring would be the wrong choice, despite everyone doing it. Don't get caught up in the status quo.

I think this is new information for a lot of folks, and this means a lot of mostly bad advice has been given out over the years. They didn't make the new bov until 2014, so you can imagine charge pipe and turbo kits designed in 2011 did not consider or include it.

 

[doublespaces]

What are you talking about what am I wrong about ? Every kit sold for years came with a 10 psi spring for n54s . I agreed with a post saying part throttle chugging was fixed by 10 psi spring. I have numerous times thought about going to a lighter spring but have seen no more than 2psi spikes on shift etc and personally I don't wantv to loose boost on shift.
Now if I was being all super complicated junk science aggressive I would say I'm faster with 10lb spring cause my 20 hg of vac help spool my turbos on transitions theoretically. Lmao

The bottom line if you have the means you can measure and use chart but that needs a healthy engine and 4 an reference. Or do what the turbo community has done for yrs and go the min that closes valve at idle . Greddy and other styles you adjusted them tial you shim or change spring but n54 needs to get the bolt on kit with instructions mentality gone. These are no longer virgin cars they have been molded and treated differently so no one size fits all. And I stick with agreeing with if your having part throttle issues a heavier spring can help . That is not saying it always will but a car right on boost threshold can have a certain chop to it.

See my reply I edit it

 

[Rob09msport]

See my reply I edit it

Unless you dont want me to I'll delete my response as well and I agree with both of you as long as not trying one size fits all and if it was buying now I'd prob start lighter. I just don't think people with 10 should switch and people with 6 shouldnt either unless they are experiencing problems like in this thread .

 

[doublespaces]

Unless you dont want me to I'll delete my response as well and I agree with both of you as long as not trying one size fits all and if it was buying now I'd prob start lighter. I just don't think people with 10 should switch and people with 6 shouldnt either unless they are experiencing problems like in this thread .

I would agree with that.

I have numerous times thought about going to a lighter spring but have seen no more than 2psi spikes on shift etc and personally I don't wantv to loose boost on shift.
Now if I was being all super complicated junk science aggressive I would say I'm faster with 10lb spring cause my 20 hg of vac help spool my turbos on transitions theoretically. Lmao

I woke up not long ago. Right about the time I sent my first reply actually. But can you explain how you'd lose boost during a shift boost spike? The two pressure sensors are aggregated by MHD and I have been told they can be separate parameters. But I assume the manifold sensor's vacuum reading overrides a positive measurement in the chargepipe. @jyamona would need to chime in for me as I'm not sure. But if I'm right then if you see a boost spike, despite a shift or throttle closure, then the bov is not seeing vacuum either and therefore won't open. If I'm looking at this wrong feel free to clarify for me.

 

[Rob09msport]

If throttle partial close a stronger spring could help stay shut . Under boost with partial close you wont have manifold vac but you will have differential in charge pipe and I have honeywell map sensor on my charge pipe logging through my torqbyte so I can see raw boost data . Mhd also has diff params that's why you have boost and boost mean

 

[doublespaces]

So I just had a talk with a couple tuners. The manifold doesn't need to see actual negative pressure values. If the differential between the top port and chargepipe is greater than 10psi then it can open.

So if there is a pressure differential if 10 psi, vacuum or not, then it could open. Now, how often that occurs and how much of this responsibility should be on the tune rather than the hardware is another discussion I suppose.

Also, regarding the point about vendors changing it. I was told n54 is a bunch of cheap asses and they don't care what you guys do. Lmao.

 

[Rob09msport]

So I just had a talk with a couple tuners. The manifold doesn't need to see actual negative pressure values. If the differential between the top port and chargepipe is greater than 10psi then it can open.

So if there is a pressure differential if 10 psi, vacuum or not, then it could open. Now, how often that occurs and how much of this responsibility should be on the tune rather than the hardware is another discussion I suppose.

Also, regarding the point about vendors changing it. I was told n54 is a bunch of cheap asses and they don't care what you guys do. Lmao.

Lmao literally seconds apart

Anyway because of my history with certain people and arguing about tunes and hardware I didn't want to get into the tune part but yes a perfect tune and perfect car should technically be extremely resistant to oscillations and chugging stalling etc.

 

[doublespaces]

Additionally, it appears the QRJ is just a fancy diverter valve. With the plunger bottom now being the outlet, boost is applied to the side of the piston which eliminates this pressure differential discussion.

I think I may switch to a QRJ and see it I can notice any differences. Skip to 1:40

 

[doublespaces]

a perfect tune and perfect car should technically be extremely resistant to oscillations and chugging stalling etc.

So if not a hardware issue, what is happening when someone reports the "chugging"? I'm trying to wrap my head around what this even means, until then I can't identify a solution.

Is this open throttle surging? Or perhaps the BOV literally being pushed open due to throttle closures and pressure differential?

 

[Jeffman]

The compressor wheel doesn't make a perfect seal with the housing and when lifting off the throttle, pressure can equalize going out of the intake rather than into the engine or out the bov.

Hey, I didn’t know this. News to me. Something to keep in mind. EDIT: (This is a great thread.)

I used all the different springs and the 10 performed the most responsive without any issues. All the other ones had response and stability issues.

This is my experience too. 10psi spring seems to snap shut faster and I get better response when driving sportily.

Everytime I pushed the pedal in the mid range power band it would vacillate between open and close. After replacing with the 10psi one, it never wavers, it just works and doesn't vacillate.

This was also my experience. The 10psi “plain” spring seems more responsive than the 8psi “white” spring.

But now I’m noticing for the first time “chugging” or “lugging” at low rpm (below 1500 rpm) in 3, 4, or 5th gear going uphill. I’m not sure if this is due to BOV / spring or something else. Thoughts?

(One other thing to consider is whether the low rpm lugging up hill is a result of the transmission tune. I had recently flashed xHP Stage 3 V2.1, upgrading from Stage 3 V2.0. It kind of surprised me that the tranny was shifting up under low torque request below 1500 rpm...:headscratcher

 

[doublespaces]

But now I’m noticing for the first time “chugging” or “lugging” at low rpm (below 1500 rpm) in 3, 4, or 5th gear going uphill. I’m not sure if this is due to BOV / spring or something else. Thoughts?

This is in D mode? I don't have any hills where I live so I can't really test this out. I can only speak from my experience with a single turbo, there is no way I'd want to be at 1500 RPM going up a hill. If I'm cruising on a flat road perhaps but honestly I like to shift when I dip below 2k.

 

[Jeffman]

This is in D mode? I don't have any hills where I live so I can't really test this out. I can only speak from my experience with a single turbo, there is no way I'd want to be at 1500 RPM going up a hill. If I'm cruising on a flat road perhaps but honestly I like to shift when I dip below 2k.

Yep. D mode. Stock turbos.

 

[doublespaces]

Yep. D mode. Stock turbos.

What boost levels are you making there? Vaguely recall stock turbos make max torque in that range. If you've got a lot of load going up a hill at low RPM, the engine may not be ingesting much air, but load is increasing wastegate duty and your turbos are surging. I'm not a tuner but that is my only explanation for it. Turbos are making more boost than the engine can consume, pressure rises too much and the air stalls and you've got surge. Air goes backward making funky noises. I suppose this is a tuning related problem? I don't think we can blame the spring size here, you are going up a hill so the throttle should be open. If the latest xhp tune causes you to be in a higher gear than normal in that load condition, then it would seem your tunes aren't matched well or something. I think this is surge, not a bov spring issue but I'm just guessing.