MBC... Tee'd to BOV!

[Slippi84]

I can't believe this is still being argued. For those of you who needs proof, run a boost leak test with your MBC intact and see your BOV opens as the desired pressure is reached and the MBC bleeder hole is exposed. Running your MBC to your BOV line is really no different than creating a rip on the line itself. Not tapping the BOV line is not a matter of opinion, it's a fact.

A rip in the line is a leak that will never reach a point where the line will overcome the amount of air the leak is releasing where as the bleeder valve will still pressurise.

 

[Slippi84]

Wish, as a crude example take a garden hose and punch it full of holes. Run water down it. You're going to get a lower pressure at the far end than you would at the source end. The same holds true even in a positive-pressure system... quite possibly why everyone who uses an EGT taps the thermo probe into the #1 runner, which always seems to run hottest out of the four. Odd that it's also the furthest from the feed on the rail. Sure, if it was a closed volume that was being filled to a certain pressure, gradient drop wouldn't matter in the least.. but the intake tract is a flowing pressurized system. Same reason that intercooler pressure drop from the hot to cold side is real.

I'm running from the compressor outlet elbow on my setup. I see a minor boost drop at higher altitudes. I used to run BOV teed, which solved the 'problem' (gave me a solid 16psi no matter if I was at sea level or 8,000ft instead of dropping to about 12-14psi), which was primarily caused due to a few boost leaks that have since been fixed. I still get some drop at-height, which I'm blaming on the lower ambient air density until a better explanation comes along. Swapping over also solved an annoying spike-to-19 issue that would kick in fuel cut like crazy if I wasn't careful with how I romped on it.

Air and water have totaly diffrent properties which I'm sure you know and while your anaolgy makes sense it is not a accurate comparriosn as a bleeder valve does not as is not the same as a whole in the system no less multiple whose in the system. Like dsmonster said a leak is a leak no matter where it is in teh system.

 

[dsm-onster]

I think one thing most fail to realize is that the whole system pressurizes. So if you have a boost leak you will still have the same damn boost leak at the compressor housing. If you are unable to pressurize the whole system then how is moving the pressure signal any closer going to affect anything? Having a bleeder style bov is a leak so weather it is in the line for the bov or in the line from the compressor to the wg, you still have a leak.

This is so very true. I used to blow my piping at the compressor outlet often. Also, I blew jsut before the inlet to my FMIC several times. And no matter where my boost reference was The turbo still squeeled in over spin.

Oldman, this is becoming quite a conundrum. I've ran literally hundreds of boost leak tests. I can feel my MBC vibrate when applying the test pressure. This to me shows that the pressure before it in the line is constant and at the desire boost level chosen when adjusting. I've noted no leaks at the BOV/bypass. The test pressure in the "head" of the BOV PLUS the spring rate is enough to counter the pressure applied to the valve from the test pressure.

I'm sure this has happened w/ you though. So is only my mbc vibrating (maintaining the proper pressure in the BOV line) and not others? I have ALWAYS run Gillis boost valves. . . Perhaps there's more engineering involved than I can deduce.

 

[Talesin]

Which is why I said it was a crude example. The drop from the feed end of a pressurized flowing system to the outlet end is generally the same idea though... it does not pressurize evenly across the entirety of the system, as the system itself is not static (aside from in the case of a boost leak test).
Though for basic (non compressive) flow characteristics, water can be used as a rough analogue to map irregularities and bottlenecks. But that's an entirely seperate topic.

And I wasn't arguing that an MBC is the same as a boost leak. Never said that once. I was saying that tapping from the compressor outlet elbow will not force the turbo to overspin as much in the event of a boost leak, as tapping wastegate actuation from the manifold.

 

[wishihadatalon]

Wish, as a crude example take a garden hose and punch it full of holes. Run water down it. You're going to get a lower pressure at the far end than you would at the source end. The same holds true even in a positive-pressure system... quite possibly why everyone who uses an EGT taps the thermo probe into the #1 runner, which always seems to run hottest out of the four. Odd that it's also the furthest from the feed on the rail. Sure, if it was a closed volume that was being filled to a certain pressure, gradient drop wouldn't matter in the least.. but the intake tract is a flowing pressurized system. Same reason that intercooler pressure drop from the hot to cold side is real.

I'm running from the compressor outlet elbow on my setup. I see a minor boost drop at higher altitudes. I used to run BOV teed, which solved the 'problem' (gave me a solid 16psi no matter if I was at sea level or 8,000ft instead of dropping to about 12-14psi), which was primarily caused due to a few boost leaks that have since been fixed. I still get some drop at-height, which I'm blaming on the lower ambient air density until a better explanation comes along. Swapping over also solved an annoying spike-to-19 issue that would kick in fuel cut like crazy if I wasn't careful with how I romped on it.

You are aware that number 2 probably runs the hottest/leanest right? I am pretty sure mitsu wouldn't stick a knock sensor on a safe cylinder

 

[dsm-onster]

Wow laminar flow would really send this topic hurling .

And I wasn't arguing that an MBC is the same as a boost leak. Never said that once. I was saying that tapping from the compressor outlet elbow will not force the turbo to overspin as much in the event of a boost leak, as tapping wastegate actuation from the manifold.

Absolutely. There is a loss of air mass in the line. But, the turbo or even the boost leak test source is more than capable of refilling the line to maintain the desired boost. The pneumatic pressure post MBC ball is controlled by the oriface and the spring inletting air particles as neccesary. The boost valve only inlets enough particles to the WG actuator so that (using the oriface) the WG actuator sees a lower boost. Every loss in mass, causes there to be an intake in mass at the intake manifold side of the line system. Therefore pressure is maintained pre-MBC. Afterall, the line diameter is MUCH greater than the oriface diameter.

There is a pressure loss where there is 'more coming out than going in'. Where there is not, pressure is maintainted. Remember(where tapping from the BOV line), just before the MBC ball spring releases, there is the desired boost (perhaps more so) in the BOV line. Unless the diameter of the oriface PLUS the release rate of the spring is more than the line can supply:
1.The desired boost pressure is still there at the BOV opening
2. The BOV still can keep the valve closed as effectively
3. It still will open as quickly because the MBC prevents the oriface from seeing vacuum and inletting air.

 

[dsm-onster]

A rip in the line is a leak that will never reach a point where the line will overcome the amount of air the leak is releasing where as the bleeder valve will still pressurise.

Nevermind the punctiation, it still took me a couple of paragraphs to state that .

 

[Slippi84]

Wow laminar flow would really send this topic hurling .


Absolutely. There is a loss of air mass in the line. But, the turbo or even the boost leak test source is more than capable of refilling the line to maintain the desired boost. The pneumatic pressure post MBC ball is controlled by the oriface and the spring inletting air particles as neccesary. The boost valve only inlets enough particles to the WG actuator so that (using the oriface) the WG actuator sees a lower boost. Every loss in mass, causes there to be an intake in mass at the intake manifold side of the line system. Therefore pressure is maintained pre-MBC. Afterall, the line diameter is MUCH greater than the oriface diameter.

There is a pressure loss where there is 'more coming out than going in'. Where there is not, pressure is maintainted. Remember(where tapping from the BOV line), just before the MBC ball spring releases, there is the desired boost (perhaps more so) in the BOV line. Unless the diameter of the oriface PLUS the release rate of the spring is more than the line can supply:
1.The desired boost pressure is still there at the BOV opening
2. The BOV still can keep the valve closed as effectively
3. It still will open as quickly because the MBC prevents the oriface from seeing vacuum and inletting air.

EXACTLY!!

 

[oldman]

Oldman, this is becoming quite a conundrum. I've ran literally hundreds of boost leak tests. I can feel my MBC vibrate when applying the test pressure. This to me shows that the pressure before it in the line is constant and at the desire boost level chosen when adjusting. I've noted no leaks at the BOV/bypass. The test pressure in the "head" of the BOV PLUS the spring rate is enough to counter the pressure applied to the valve from the test pressure.

I'm sure this has happened w/ you though. So is only my mbc vibrating (maintaining the proper pressure in the BOV line) and not others? I have ALWAYS run Gillis boost valves. . . Perhaps there's more engineering involved than I can deduce.

I have done this many times and the results are the same, a slightly opened BOV, most don't notice this because either the MBC is disabled during a leak test or the BOV is recirculated during normal operations. Also keep in mind that you are only talking about a ball and spring type MBC so far, put the ever so popular turboXS bleeder type MBC in the picture and your entire theory crumbles. There is definitely a valid discussion to be had of pros and cons between manifold and compressor boost reference but the BOV line should not be in it. Would you tap your FPR line for your MBC knowing there is a bleeder hole? Another test that can be done is to log a wideband WOT pull then move your MBC to the FPR line and see if AFR changes. Although I have not done this test yet, common sense tells me you should run leaner.

 

[Slippi84]

Nevermind the punctiation, it still took me a couple of paragraphs to state that .

yeah yeah it's all good. I just try and keep the big words to a minimum so if a newb was to read he could understand. I can follow yoru theory and logic when brakin stuff down but I know some people look and go WTF

 

[Slippi84]

I have done this many times and the results are the same, a slightly opened BOV, most don't notice this because either the MBC is disabled during a leak test or the BOV is recirculated during normal operations. Also keep in mind that you are only talking about a ball and spring type MBC so far, put the ever so popular turboXS bleeder type MBC in the picture and your entire theory crumbles. There is definitely a valid discussion to be had of pros and cons between manifold and compressor boost reference but the BOV line should not be in it. Would you tap your FPR line for your MBC knowing there is a bleeder hole? Another test that can be done is to log a wideband WOT pull then move your MBC to the FPR line and see if AFR changes. Although I have not done this test yet, common sense tells me you should run leaner.

good thing no one said that putting it there would be a good idea

A slight change if any in elapsed time to pressurise a system that is connected to something that controls fuel is a little diffrent from something controling your bov which doesn't rely on that vaccume and pressure line to regulate as frequently.

 

[dsm-onster]

I have done this many times and the results are the same, a slightly opened BOV, most don't notice this because either the MBC is disabled during a leak test or the BOV is recirculated during normal operations. Also keep in mind that you are only talking about a ball and spring type MBC so far, put the ever so popular turboXS bleeder type MBC in the picture and your entire theory crumbles.

AH! Well, my theorys don't crumble. They only encompass ball and spring MBCs . I have only used ball and spring. I love ball and spring MBCs. There is a sharp increase in boost response because of negating the effects of the bleeder oriface.

Constant bleeding DOES lower the pressure of the entire line and any line the same size. This circumstance calls for the entrance of the line system to be at a diameter so as NOT to maintain the boost of the manifold. Therefore, any items used referencing this line will see a lower pressure as the entrance of the line CANOT maintain the flow to keep up w/ the bleeder. . .

I wonder if the form of MBC has been the sole difference between those who have noted issues and those who have not. ???

Would you tap your FPR line for your MBC knowing there is a bleeder hole? Another test that can be done is to log a wideband WOT pull then move your MBC to the FPR line and see if AFR changes. Although I have not done this test yet, common sense tells me you should run leaner.

Again, I have run such a a/f ratio test (albiet accidentally). I chose to use the FPR reference when running my Gillis valve and noted no change in A/F ratio. MY AGP WG actuator points tot he alternator. And I had no threaded nipple for my compressor reference source. It was infact closer to route the line on the accessory side of the engine. I use the narrow band simulation on my LM-1 in place of an o2 sensor for closed loop. So my wideband is always running in my setup.

To me, the difference in the MBC types mean everything here. I suspect that any running a properly built ball and spring MBC would see no difference. FWIW, Gillis suggests tapping the BOV line as well .

 

[oldman]

A slight change if any in elapsed time to pressurise a system that is connected to something that controls fuel is a little diffrent from something controling your bov which doesn't rely on that vaccume and pressure line to regulate as frequently.

You have to make up your mind on whether there is a difference, according to your posts thus far, there is absolutely no difference in pressure due to the bleeder hole, therefore you should have absolutely no problems with tapping the FPR line.

Furthermore if memory serves, didn't you have a bleeder type MBC (TurboXS) tapped to the BOV line that was giving you all kinds of BOV problems? Are you guys saying your theory still holds when dealing with a bleeder type MBC which is a constant boost/vacuum leak?

 

[dsm-onster]

You have to make up your mind on whether there is a difference, according to your posts thus far, there are absolutely no difference in pressure due to the bleeder hole, therefore you should have absolutely no problems with tapping the FPR line.

Furthermore if memory serves, didn't you have a bleeder type MBC (TurboXS) tapped to the BOV line that was giving you all kinds of BOV problems? Are you guys saying your theory still holds when dealing with a bleeder type MBC which is a constant boost/vacuum leak?

I am not, Bruce . Again. I feel that the type of MBC is important here. Further, I feel that if one knows the effects of both styles of manual boost controlers, then he/she can determine the best and most convenient reference. I'll say that if you have a ball and spring mbc, then you can put her pretty much anywhere. If you have a bleeder then you are limited to a line from where no other components are referencing boost. Again, I suspect this is why T'ing off the bov line has yielded such mixed results.

There IS a MBC out there that can yield no ill effects from tapping at the popular BOV line. But, one has to know what he/she has purchased before using (as always).

BTW, my Gillis Valve is far cheaper than a TurboXS Valve and does not spike. It seams to exhibit the capability of being mounted anywhere and this one valve has been used for several years and on several different cars.

 

[oldman]

There IS a MBC out there that can yield no ill effects from tapping at the popular BOV line. But, one has to know what he/she has purchased before using (as always).

Even if I were to agree with this statement, which I don't, it would be a good reason to just not using the BOV line period since the ill effects are mostly hidden until it's too late...mostly. As for why I disagree with your above statement, I have done this test on both of my 90'/Hallman EVO RX PRO and 95'/good old joe p and the results were the same, opened BOV, I would say that both Hallman and Joe P are "WELL BUILT" ball and spring. This acutally came about accidentally years ago while helping a member in a boost leak test thread where OP was freaking out that his BOV was leaking bad during the test. It turned out that he didn't disable his MBC and the BOV leak stopped as soon as he pinched the line to the MBC shut. I know nothing of the Gillis MBC so I will not comment on it.

 

[Slippi84]

You have to make up your mind on whether there is a difference, according to your posts thus far, there is absolutely no difference in pressure due to the bleeder hole, therefore you should have absolutely no problems with tapping the FPR line.

Furthermore if memory serves, didn't you have a bleeder type MBC (TurboXS) tapped to the BOV line that was giving you all kinds of BOV problems? Are you guys saying your theory still holds when dealing with a bleeder type MBC which is a constant boost/vacuum leak?

I have had no such bov problems. I simply was playing devil's advocate I don't think there is any diffrence but even if there were the VERY slight diffrence that yoru claming would not be enough to compramise bov opperation but may with a fpr. I am not agreeing that there is a diffrence but even if there were it would be a diffrent situation with the two locations.


edit: I looked back over my past threads only situation with bov related problems had to do with a stock style maf with tial style bov. The bov was never the problem or line.

 

[oldman]

I have had no such bov problems. I simply was playing devil's advocate I don't think there is any diffrence but even if there were the VERY slight diffrence that yoru claming would not be enough to compramise bov opperation but may with a fpr. I am not agreeing that there is a diffrence but even if there were it would be a diffrent situation with the two locations.


edit: I looked back over my past threads only situation with bov related problems had to do with a stock style maf with tial style bov. The bov was never the problem or line.

If in fact you still have THE TurboXS bleeder, I strongly suggest that you remove it from the BOV line ASAP especially for your BB GT3082 CHRA, it's physically impossible to not have any ill effects with a bleeder valve, it is guarrenteed. I would be worrying about compressor surge on a BB turbo if I were you, regardless if it's noticeable or not.

 

[Maglin]

I have to agree with Oldman on this one. I had a very long and detailed post about this but when they changed the board email rules I for some reason got thrown into the crop and couldn't post for a day. So that HUGH post wasn't posted. But basically is said that a bleeder style MBC on the BOV line would allow the BOV to open under high boost cause the pressure at the BOV inlet would be lower cause of the controlled leak at the MBC. With the BOV having it's own dedicated line it would hold more pressure before leaking cause it has move force applied to the diaphragm due to the high pressure at it's inlet. The effects of this wouldn't be as sever on a ball and spring MBC but it would still be their to an extent. The ball and spring MBC still has a bleeder orifice after the actual valve to release the pressure in the line to allow the actuator to close again.

I don't know where FPR line came from in this threed but that is just stupid to do. FYI the only reason 1:1 raising rate FPR's are used is to counter the effects of the pressure applied to the bottom of the injector. If it was a constant FPR then the injectors would effectively act as larger injectors at vacuum and smaller injectors under boost do to pressure differentials. Useing the FPR line for a boost gauge is ok but I still wouldn't do it personally and just get it from the TB as everyone pretty much gets rid of their emissions and the port is their for it.

2 years ago it was the way everyone said to run a MBC. Off the BOV line and not the compressor cover. Now it's changed and the same mentality is being applied to it as it was back then. And that is "Everyone is doing it so it's the only way and I will listen to mods before you."

I believe on the first page if I recall someone said that they only listen to Wisemen and mods and not to anyone else cause they should know. Well I know a certain Wiseman on here personally and he brings his DSM to me to fix it. Also the same person that only trusts mods/wisemen also said the BOV line is supposed to be pressure only. That is way wrong. You want a manifold pressure source on their so when you let off the vacuum helps to open the valve faster which will help with compressor stall issues. And as oldman hit on using the BOV line for a bleeder MBC can help cause surge due to the BOV opening under boost.

edit: also as a personal opinion on MBC's. When I'm asked which one to buy it's always the same. If you have an external WG get the bleeder style TurboXS MBC. It's the best bleeder MBC I've used to date. If using an actuator then #1 is TurboXS High Performance MBC which is ball and spring or the bleeder TurboXS MBC. They are just easy to adjust with the newer housings and no tools required and very very accurate as far as bleeder MBC's go.

 

[Slippi84]

If in fact you still have THE TurboXS bleeder, I strongly suggest that you remove it from the BOV line ASAP especially for your BB GT3082 CHRA, it's physically impossible to not have any ill effects with a bleeder valve, it is guarrenteed. I would be worrying about compressor surge on a BB turbo if I were you, regardless if it's noticeable or not.

Thanks for the concern but I don't and have never had a bleeder style bov. My bov is a homemade sbr style mbc

 

[oldman]

And as oldman hit on using the BOV line for a bleeder MBC can help cause surge due to the BOV opening under boost.

I was thinking more along the line of BOV opening too slow after letting off due to vacuum leak, the only ill effect of an open BOV under boost is constant turbo overspin, unless of course if the BOV is improperly vented.

 

[Maglin]

I was thinking more along the line of BOV opening too slow after letting off due to vacuum leak, the only ill effect of an open BOV under boost is constant turbo overspin, unless of course if the BOV is improperly vented.

Then it's stall not surge.

 

[dsm-onster]

I am still lost as to why a ball and spring mbc (which acts as a check valve) would cause surge or any issues related to this discussion. If the pressure goes down at the BOV nipple then the spring/ball will close the bleeder oriface. The ball has the assistance of the spring to encourage to it to shut long before the pressure before and after the MBC becomes equal. There will be no bleed at such a point where the ball seals. Further, the rapid open/close of the ball valve suggests that the line to the MBC remains at a constant pressure and the spring is modulating the flow out of the valve for anything after the MBC (actuator).

Oldman, your example of a ball and spring mbc still causing a BOV to open is noted. I just don't understand it. I agree that if there are mixed results, "better safe than sorry". But still I'm perplexed. What is going on w/ my setup and all the other's i've had my hands into?

 

[oldman]

Then it's stall not surge.

Didn't not know the difference, education time.

 

[oldman]

Oldman, your example of a ball and spring mbc still causing a BOV to open is noted. I just don't understand it. I agree that if there are mixed results, "better safe than sorry". But still I'm perplexed. What is going on w/ my setup?

Perhaps the pressure in the line itself is stabilized but that doesn't ensure the stabilized pressure equals the pressure in the UICP. There are too many variables involved here, I would suspect the size of the bleeder hole also plays a big role.

 

[Slippi84]

Perhaps the pressure in the line itself is stabilized but that doesn't ensure the stabilized pressure equals the pressure in the UICP.

That's why they make diffrent size stronger springs and or bigger bov pistons thus my 50mm bov with 12psi spring I think it will hold just fine.