[TunafishE93]

Was wondering if anyone had any experience with the adjustable BOV like in the title. They seem similar to cheap eBay ones if not the same. I asking about the adjustable part, how you adjusted it, any hints or troubles you ran into? Thanks.

[Rob@RB]

Get a quality authentic BOV with a 50mm flange, nothing smaller (ie. certainly NOT the HKS) if you plan on tuning moderately or above on even stock turbos, popular for this platform is the Tial Q or Turbosmart Raceport. Also get a vacuum reference upgrade while doing it, no exceptions to this either. The amount of N54'ers who essentially kill their turbos by getting bunk BOV/Diverter setups is (and always has been) out of control.

[TunafishE93]

I would like the topic to stay on the cheap adjustable bov. Thanks though.

[Rob@RB]

Originally Posted by TunafishE93

I would like the topic to stay on the cheap adjustable bov. Thanks though.

If you are referring to these valves?
https://www.summitracing.com/parts/x...wQGmK2Evok7WXg

They appear to be about the size of OE N54 diverters and could be better than some other options, but for similar goals usually the Turbosmart Kompacts (which has a BOV version) is the go-to for quality/function. However due to volume capacity discharge limitations (combined with relatively small turbos that spin to 200,000+RPM with less than desirable thrust bearings) you will want to ideally keep power to around 400whp (or less), with any of these size limited valves (tiny diverters or small BOV's using OE style chargepipe provisions); or just replace your turbos when you pound out the compressor side of the thrust bearings in short order.

Other than their limitations they should work fine with any OE style diverter chargepipe based, assuming the BOV's have 1" bungs, but likely can find tapered couplers if larger as well. Having 1" provisions on the chargepipe is a large limitation though, and is a big reason to move away from them if you can.

You will need to do a vacuum reference upgrade, if you care to get proper function, where in this case dedicated vacuum rated hoses for each valve to its own properly sized dedicated intake vacuum reference fitting. Skimping on this and just using the OE tiny plastic nipple, T'd to both valves, will lead to lazy reaction and even worse outcomes.

Regarding adjustment the spring settings are typically based on engine vacuum at hot idle, so surely you can find an adjustment with some trial and error using a worse case by ear. However if you can see when the valve opens/closes this would make it really easy, and I'd assume you can see this with the mini filter removed.

Ultimately you want the valve to be either very lightly closed, or just ever so lightly opened, at hot idle. If it is too far open the spring is too soft (so you'd adjust it harder) and it if it is too hard closed the spring is too hard (so you'd adjust it softer). Most valves do this by replacing the springs entirely for coarse adjustments, but if the base spring stiffness is close adjustment style valves can work well for fine tuning.

What I have seen over the years is that those who cheap out/cut corners on these things, usually pay the price in shorter time than they'd like, noted by many hundreds (of the couple thousand sets in total) core tear downs I've performed over the years. As such while no one has to take heed to what I am saying here, I am just trying to give helpful advice that may save you or another from some regrets.

Rob

[TunafishE93]

The blow off valves are designed from side by side, made by Holley, they own the xdr label.
They are 25mm (stock size) the side by side run ~16inhg vacuum at idle which is about what the n54 runs and they have ~14psi boost which is more than a stock n54 so it should hold up.
My main question is the adjusting, they tell you how to adjust the side by side. Softest setting, rev in neutral and let off, if rpms drop down below idle, harder one turn and repeat till rpm doesn't drop below idle.
Thats the part that i am not sure will work on the n54. Concept is the BOV being too soft will be open at idle but i dont see how this would effect idle on the n54. Maybe you can physically see them open? Or on the charge pipe side at idle there would be a vacuum or pressure that is being vented? That is where i am getting stuck. I know the manifold side of the throttle will have a vacuum at idle but not sure what the post turbo side before the throttle will have.

[Rob@RB]

Originally Posted by TunafishE93

The blow off valves are designed from side by side, made by Holley, they own the xdr label.
They are 25mm (stock size) the side by side run ~16inhg vacuum at idle which is about what the n54 runs and they have ~14psi boost which is more than a stock n54 so it should hold up.
My main question is the adjusting, they tell you how to adjust the side by side. Softest setting, rev in neutral and let off, if rpms drop down below idle, harder one turn and repeat till rpm doesn't drop below idle.
Thats the part that i am not sure will work on the n54. Concept is the BOV being too soft will be open at idle but i dont see how this would effect idle on the n54. Maybe you can physically see them open? Or on the charge pipe side at idle there would be a vacuum or pressure that is being vented? That is where i am getting stuck. I know the manifold side of the throttle will have a vacuum at idle but not sure what the post turbo side before the throttle will have.

I'd agree if you are not looking for much of an upgrade and just rather a replacement/minor upgrade for the OE diverter, such as something that is good for stock turbos moderately tuned (ie. like the Turbosmart Kompacts or other valves using stock provisioning) then these could be a fair option. Fitment wise sounds like they'd work well.

Regarding the adjustment the main spring stiffness is going to be the biggest concern, but as you said it "should" be very close based on the engine hot idle vacuum when comparing the sxs to N54. So assuming all is well there and onto the fine adjustments, I'd mentioned above you maybe able to see the valve move, and if so described how that would help you determine how to adjust it with some level of precision. If you get to that point and the adjustments are not working well for you then the spring may need to be swapped accordingly.

The "how to" adjustment they are giving for the sxs application doesn't sound too great, perhaps a "that should do it" type of adjustment at best lol. However if the sxs is a mass air system (which I don't think it would be?), perhaps it would apply a bit more due to loss of metered air upsetting the fueling. The N54 is certainly not mass air so there is no air metered that is lost.

Still run upgraded vacuum references as also mentioned above and good luck, I doubt anyone else has tried swapping them in so you will more than likely be pioneering this one. While it could be a much better way to go then dumping a ton of coin on Turbosmart Kompacts to still get close to no where, I'd still stand by that if you feel you will want to make bigger power someday to skip it all and jump straight to a 50mm BOV such as the Tial Q or Turbosmart Raceport which are (fairly inexpensive) simplified upgrades that have large potential for growth.

[TunafishE93]

I installed the blow off valves with little issues. My charge pipe was previously changed so i already had 2-1" barb for the factory BOV.
I adjusted by provided instructions, seat all the way down and back out 2 1/2 turns. Wasnt getting noticable blow off so went all the way loose. Got blow off, and valve was closed at idle. Put both at 3-1\2 turns out but might loosen up.
They do seem to be working and quality seemed good, piston was round and holding vacuum. Spring might be to strong/long though cause even at the softest setting i am not getting piston to open at idle. Will have to experiment with the setup.

[oVeRdOsE.]

thanks Rob for the info.

On my car I've those small 1'' BOV from previous owner (the one you've posted) and when I did a single turbo conversion, I kept only one BOV and max out the spring.

The logic here was if it's maxed out and small, but still blowoff some air , even if it produce some resistance, is nothing like those guys running no-bov for the stustustu...

anyway, bushing 26psi 7.5° 535whp, and seems to run fine, no leak (I think), the logs looks fine.


I'm thinking getting a ''proper'' one , but not sure if it work it.

[TunafishE93]

Ok, i think I am gonna put this to sleep for me, at least for adjustment. I data logged and found the 2.5 turns from bottom to be the best. One turn less spring pressure dropped high rpm boost by about 2 psi. One turn more spring pressure produced same boost as 2.5 turns but a longer delay in pressure release.
The new BOV has about a 2 psi improvement over the factory BOV thru most of the RPM range doing a pull.

[Rob@RB]

Originally Posted by TunafishE93

Ok, i think I am gonna put this to sleep for me, at least for adjustment. I data logged and found the 2.5 turns from bottom to be the best. One turn less spring pressure dropped high rpm boost by about 2 psi. One turn more spring pressure produced same boost as 2.5 turns but a longer delay in pressure release.
The new BOV has about a 2 psi improvement over the factory BOV thru most of the RPM range doing a pull.

Did you do any vacuum reference upgrade for each new valve, or did you just Tee them together and back to the factory tiny plastic nipple as it was stock? If the latter, do the vacuum reference upgrade, then work on the adjustment.

None of the aftermarket valves (diverters, BOVs, etc) respond well to an undersized/shared vacuum reference. In the case of aftermarket/upgraded diverters I'd suggest two new bungs, one dedicated for each valve, size the new bungs ID's similar as the valves bung ID and use vacuum rated hosing and spring clamps. Cheapest way is to drill/tap manifold (by the existing bung) to thread in new larger bungs, or buy some quality kit. Many times overlooked but very important to do this part correctly, especially as poorly responding valve(s) will lead to a much quicker internal turbo thrust bearing demise.

Rob

[Rob@RB]

Originally Posted by oVeRdOsE.

thanks Rob for the info.

On my car I've those small 1'' BOV from previous owner (the one you've posted) and when I did a single turbo conversion, I kept only one BOV and max out the spring.

The logic here was if it's maxed out and small, but still blowoff some air , even if it produce some resistance, is nothing like those guys running no-bov for the stustustu...

anyway, bushing 26psi 7.5° 535whp, and seems to run fine, no leak (I think), the logs looks fine.


I'm thinking getting a ''proper'' one , but not sure if it work it.

There are applications that things may "work" even when adequate for the airflow level, such as larger turbos that spin half the speed and are 2x the size of the native N54 turbos, there are applications do not use release valves at all. But on this platform which usually involves the use of smaller frame twins (especially the stockers with fragile thrust bearings) that spin to the moon with ease (ie. 200,000+ RPM), having a very effectively sized discharge port and a quickly responding valve is very critical to bearing life and in some cases even to prevent catastrophic turbo damages.

Fortunately any stressors are easily prevented by just getting the proper parts and setup for the application. What we've found over the years is that the cheapest/best/easiest/cleanest way to go is to jump straight to a 50mm style BOV (Tial Q or Turbosmart Raceport) with matching chargepipe and a quality simplistic single larger vacuum reference.

Rob