TurboSmart BOV overboost and potential engine runaway soluti

Vmcrdrod · **Joined:** Wed Mar 22, 2017 9:21 am **Posts:** 33

Just got the Turbosmart BOV from XDP TS-0304-1006. It works off of pedal current has an overboost relay as well as cruise control relay cost me $280 shipped. I’m using Sasquatch CAC hose port to run air for the solenoid and BOV placement somewhere upstream of the fcv. With a relay on the over boost ground relay in the connection to the controller one could in theory control run away by using a E stop lock closed switch to ground the solenoid should the condition present itself The only trick would be that 12 volts would need to be supplied to the solenoid to maintain an open. A second solenoid would be ideal with a constant ground and a switched 12 volt directly to the Batery in any case these BOV could serve as at least an option if not a viable solution to the engine run away theory. :ALONE:

Should have everything to install it in the next week.

flash7210 · **Posted:** Fri Oct 25, 2019 8:44 am

Please post pics of the installation. This would be interesting to see in action.

Now for the big questions...

Do you have a boost gauge?
What do you expect the BOV to do for your engine? (you have to completely block off the engine air intake to stop a run away)
At what psi do you plan to set the BOV at?
Anything less than 22-23 psi is a waste of boost.
Anything more than 24 psi and the BOV will likely never open.
Of course this is assuming you have a stock tune and a stock turbo.

Vmcrdrod · **Joined:** Wed Mar 22, 2017 9:21 am **Posts:** 33

From what I’ve read the turbos with varied geometry suffer from delayed reaction of the turbine vanes and when the fuel is abruptly removed the lack of turbine side pressure is reduced and the boost is then forced back through the turbo causing wear on the turbo. the controller allows for the BOV to open in instances of pedal current changes with adjustment in sensitivity With regards to the pedal and duration with Regards to BOV relief. As far as the pressure setting for overboost I was unsure what to set it at but I’d read that 25psig is what a lot of guys are reporting I’m here at 6600 ft so I’m not sure I’ll get that much but it’s a cool feature. I plan on using the controller with the auto meter elite pro control set points that should give me a lot of user friendly manipulation of setpoint changes if I change elevations during a trip or something. I wanted to go with the us tuning shop Turbo but they've ceased to do business in that area. Looked into diesel guys turbo setup but it’s too new and without a tune I don’t think I’ll go that rout. I like the idea of controlling compressor flow reversal. This used in conjunction with a choke of some sort could be an option Ive drawn up some circuits but am looking into how the tunes work as far as fcv function. I think that a BOV down stream of the fcv could allow for inlet due to vacuum if the fcv is closed but I think it’s possible to come up with a fix for that.
I figure that a BOV will disrupt the combustion and may not stop it right away but he’ll it’ll give you enough time to be stuff a sock in the box inlet. and if one BOVs good two are better.
Doing head replacement rockers studs. With all I’ve spent I’m just looking to keep this thing running as long as I can. Decreased tubo fatigue is appealing to me even if it’s just a little bit.
Thanks
Vmcrdrod

WWDiesel · **Posted:** Fri Oct 25, 2019 2:39 pm

I said I was going to refrain from commenting on this subject, but what the heck! :banghead:

This horse has been beat to death and just does not seem to want to die! :roll:

There is absolutely no need for a BOV on normal diesel engines! But if you think you need one, go for it, it's your time and money!

I have a mechanical boost gauge gauge on my CRD (no EGR/FCV) and there are NO spikes in boost pressure when you let off the go pedal no matter high hard you are accelerating, the boost pressure falls instantly! I have played with this extensively as I have a way to turn boost up electronically on top of the Stage IV Hot Tune all the way until it can put it into "limp" mode due to the MAP sensor runs out of it's upper range and the ECM does not like that. Even at momentary pressure bursts above 30 psig on the boost gauge, the pressure drops the split second you take your foot off the go pedal. When you take your foot off the go pedal all you are doing is removing fuel, the engine is still rotating and the valves are still opening and closing allowing air to pass through the engine and turbo while it is slowing down. Remember, a diesel engine is just a big air pump!

This is an old quote from LOST back in 2014.
WWDiesel wrote:
All the 2nd generation common rail Dodge Cummins Diesels came from the factory with NO EGR, FCV, CAT, or any of that other junk! I know, I own one and the waste gate has been blocked off since day one right after I bought it new.
So all this nonsense about needing a blow-off valve or EGR valve to relieve pressure is a bunch of hogwash!

Just as others have stated; when you abruptly let off the throttle under hard acceleration, the first thing that happens is the fuel is reduced and the engine begins to slow down and the energy to spin the turbo is reduced very quickly thus reducing the boost almost instantly. If you have a boost gauge installed, you can observe this! Its amazing how quickly it happens!

My Dodge is 16 years old and still going very strong with no turbo related failures of any kind! And yes, on occasions when pulling a heavy load and you back out of the throttle very quickly, you might hear an occasional turbo bark as everything comes to a quick slowdown! You learn how to drive the diesel and try and avoid this.

Remember, the diesel engine is just a big ol air compressor that moves gobs of air through the motor, fuel is added to obtain energy or work out of the motor while all this air is being pumped through it...

To read the whole thread:> CRD blowoff valve? http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=80138

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

Vmcrdrod wrote:

From what I’ve read the turbos with varied geometry suffer from delayed reaction of the turbine vanes and when the fuel is abruptly removed the lack of turbine side pressure is reduced and the boost is then forced back through the turbo causing wear on the turbo.

I was severely dubious of this, but after a fair amount of reading, it seems there is at least some truth here. Whether there is practical value, I don't know... my CRD has 180k on its turbo and it's tight as a drum... but academically speaking, a sudden loss of exhaust pressure (caused by a lack of combustion) at a moment of high boost pressure does create the scenario where compressor surge can occur, and a BOV would alleviate the issue.

My argument against a BOV would be that with an automatic transmission used on the street this scenario rarely occurs. In a racing application, with a lot of aggressive throttle transitions OR with a manual transmission requiring lift to shift, then, maybe, there's something to be won.

Vmcrdrod · **Joined:** Wed Mar 22, 2017 9:21 am **Posts:** 33

I think you’re right about there being more occurrences in a Manual transmission vehicle but Instances where you have to break fast would probably be more likely especially on the interstate or in some city streets. As far as over boost it probably wouldn’t rear it’s head except when towing going down a hill or at a catastrophic failure like the whole run away scenario or a stuck vane. In any case it could be an added safety feature if that something ever happened you could remove some or all charge air.

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

Yeah, but do remember that venting the intake under boost can quickly create an overspeed condition that is VERY dangerous. Overspeed can cause the compressor wheel to physically expand, contacting the housing and sending shrapnel into the engine. Using a BOV to control boost is VERY dangerous. I would not recommend doing that. Gas or diesel, the only time a BOV should be open is when you're off the pedal.

I don't think a BOV can cure a runaway. Diesel runaway happens as a result of a fueling problem (unmetered fuel, etc.). The way to stop a runaway diesel is by blocking the air supply. Opening a BOV - providing another air path - would make things WORSE.

Vmcrdrod · **Joined:** Wed Mar 22, 2017 9:21 am **Posts:** 33

Hmm makes sense but if the engine is fueling and less oxygen is available for combustion due to the valve being opened the reaction would become fuel rich and theoretically taper off. If used in conjunction with a fcv close command you could remove cac air upstream of the fcv so you don’t overpressure the compressor which in itself would throw it into the casing. The reason I started looking into this is the whole egr open on shutdown with the fcv closing as a means to manage a cleaner engine stop so that GDE or weeks could be executed without removing that feature from the scenario. But it’s just an option for anyone who might like to play around with it. I am I’ll let you know if I blow up! :dizzy:

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

Overspeed has nothing to do with fuel or combustion. You have a compressor acting against a fixed intake volume, which effectively limits its speed. If that intake volume suddenly become infinite because a gaping hole to atmosphere has been opened, controlled speed immediately becomes uncontrolled speed and you have pieces of metal everywhere. Really, don't do that!

flash7210 · **Posted:** Fri Oct 25, 2019 7:41 pm

Like WWdiesel, I have a mechanical boost gauge and I’ve never seen a surge in boost when lifting off the throttle.
However I have occasionally heard a “thrush” sound from under the hood when accelerating and then suddenly lift off the throttle.
I don’t really know what that means but I’m sure the only reason I can hear it is because I’ve ditched the factory air filter box and went to a open conical filter.

With some mods, I’ve pushed as much as 28 psi from my factory turbo. Though I prefer to keep it in the 23-25 psi range.
I’ve got 230,000 miles on that turbo and it’s still in good shape.

layback40 · **Posted:** Fri Oct 25, 2019 8:29 pm

I find this thread interesting. It appears to be getting some comments by people who have done a lot of reading & little practical experience & one or 2 who actually know some about diesels.
How many of you have actual experience with diesel runaway? I suspect the reply would be silence by most.
Having had the misfortune to have experienced it 3 times ; once with a Mercedes 300DT, Once with an Isuzu turbo diesel & once with a 2 stroke GM, I can tell you that I doubt that a blow off valve would have done much.
The GM 2 stroke has a butterfly flapper in the supercharger inlet with a cable back into the cab to allow the air to be strangled to shut it down. I have had to do this. After the first time you make sure the cable is well lubricated & it works. Very scary when it happens to a scraper with a full load of earth, around 30 tons trying to speed up out of control.
Its a bit like the flapper in the inlet of our CRD's. An override on this to allow it to be closed may be worth looking at if you have a concern.
The Mercedes are known to do it when the oil seal in the turbo fails. As they are auto, you have your foot on the brake, hand brake on, up against a tree & try & block the air inlet with a block of wood. Its not fun but if you are quick you can save it.
The Isuzu was a small turbo diesel that was very worn in the rings & had lots of blowby. Cloud of white smoke out the back, turned the ignition (fuel) off & braked (it was manual) until it stalled.
Despite these 3 incidents in my life, I have not seen the need to fit a BOV & dont think it would do much. With the Mercedes, if you put the palm of your hand over the air inlet it would probably get crushed & sucked into the air cleaner.
Would be interested to hear of anyone who has had a run away with a VM CRD. I suspect if you blocked the air inlet to the airbox, it would just crush it & suck it into the turbo.

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

My GM 6.5l nonturbo ran away once. Merging onto the freeway it kept merging onto the freeway.

Fortunately it was very heavy and very slow, so it wasn't too terrifying from that regard. Once I talked my wife down, we planned a recovery and executed it flawlessly.... Brakes, neutral, jump out the door while she slid over to the driver's seat to pop the hood and put her foot on the brake while I put my wadded up shirt over the air filter snorkel to snuff it out. It never happened again, but I started keeping a cap in the engine bay in case it ever did.

I am not sure modern diesels are prone to this behavior since the injection is 100% electronic. It would be a crazy set of circumstances that resulted in the injectors accidentally being held open.

geordi · **Posted:** Sat Oct 26, 2019 12:35 pm

I have personally experienced (and partly controlled) a runaway in the CRD, after changing a turbo out that had failed and dumped oil into the intercooler.

This was in a driveway and I was manually controlling the engine RPM, it wanted to start running away anytime the RPM went above about 2k, b/c the suction started picking up the oil from the intercooler. Cutting the key was enough to stop it b/c I had my hand on the key and ready for the potential, and it didn't get above about 3500 before dying each time - but that only stopped WITHOUT added fuel from the injectors!

In gear on the road... I seriously doubt you would be able to stop it, and I don't know how many different ways this can be said: The computer DOES NOT have a provision in it for stopping a runaway, and this design DOES NOT need a BOV or any of that "open the EGR when off the throttle" nonsense b/c there is NO restriction on the boost continuing to be pumped through the engine and exhaust.

The boosted air (without fuel) balances the pressure between the intake and the exhaust, and both bleed down equally and in milliseconds. There is no imbalance condition. The sound you are hearing when you let out of the throttle is the turbo wheel re-entering the range of human hearing as it slows down, not the sound of air flowing backwards. If you want to prove this for yourself, get a logging OBD program and log the MAF reading as you drive around. If there WAS such a change of the air going backwards, then you would see it on the MAF reading as a blip to ZERO airflow as the direction reversed. This won't be seen because it DOES NOT HAPPEN on the CRD, since there is NO THROTTLE PLATE that can block the intake.

Installing this is silly and won't solve a problem that you don't have, but hey... It's your money to burn.

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

What you just described is the reason why "runaway diesel" isn't a thing on electronically injected common rail engines... because you could stop it with the key. That's why the Jeep CRD doesn't have a ASOV/AISV/ESD whatever valve... because when you cut power to the injectors with the key, the engine stops.

On older mechanically injected diesels with mechanically driven fuel pumps, they can enter a cycle where the engine *cannot* be shut down. Once a mechanically injected diesel starts, the only way to stop it is by cutting fuel or air. Normally you stop a diesel by cutting fuel, but if you lose control of the fuel, you're hosed. The engine spins, the pump runs, the engine spins, the pump runs. There is no action the driver can take to make it stop except cut off the air supply. Since there is no throttle butterfly, the only way to do that is with an emergency valve or, as I learned, your shirt.

The fuel supply on the CRD is very isolated from the intake. I personally don't see a way for unmetered fuel to get in. I don't think the CRD can suffer from runaway barring some sort of catastrophic electrical short that permanently energized the injectors. It's beyond unlikely. I'd 100% agree even if it could the FCV does not act as an ASOV/AISV/ESD valve like you find in some older diesels. Those are very specific devices, and there is no reason for such a device on a CRD. It would be like fitting a redundant throttle body on a gasser. Nobody would do that.

WWDiesel · **Posted:** Sat Oct 26, 2019 5:12 pm

A few key summary points to reiterate that some have already briefly touched on.
1. Geordi is correct, no fuel to the engine from whatever the source and the engine dies regardless of circumstances, it will not run on air. When you cut power off to the ECM, fuel injection stops immediately as the injectors stop injecting.
When I first got mine Jeep CRD I floored it on an open highway and when I took my foot off the go pedal it kept accelerating on its own for a few hundred feet all the time blowing black smoke out the exhaust. It was due to the intercooler (CAC) being full of oil that had accumulated before I bought it over time. I immediately pulled the intercooler, cleaned it, and installed a ProVent to keep from collecting oil in the intercooler in the future. But I was totally able to control it with the brake pedal, no runaway engine.

I have been on this forum since 2013 and I do not ever remember anyone reporting a runaway engine to self destruction on one of these vehicles.

2. If you are in a high boost situation and you suddenly open a port on the pressure side of the turbo to atmospheric pressure thus relieving all boost pressure, it will instantaneously drive the turbo into an extreme overspeed condition and most likely will self destruct in nano seconds sending shrapnel everywhere. The backpressure of the boost pressure on the turbo blades is one of the things that limits it's peak speeds along with the variable vanes on the exhaust side. If you suddenly remove this backpressure using a BOV or EGR valve opening, there is nothing to stop the turbo from overspeeding itself into self destruction.

3. Bottom line, adding a BOV our simply using the EGR valve to relieve boost pressure could be setting your turbo up for total destruction. I would strongly advise against it!
But as always, it's your vehicle, you can do whatever you desire to it.... :juggle:

Vmcrdrod · **Joined:** Wed Mar 22, 2017 9:21 am **Posts:** 33

We’re talking about a catastrophic failure here. Fueling due to failure of some component feeding oil into the intake or directly into the combustion chamber. This controller also alleviates the condition known as turbo bark. In a post gde states that during something like 115 % pedal change the egr would open for the same reason. It’s a tool that could be used to comtrol the possible situations they may never happen and that’s great but if the did.... also the Bov operation is controlled electronically through the controller it’s not open untefinaly you set it on two seconds not enough time to completely evacuate the cac.

Vmcrdrod · **Joined:** Wed Mar 22, 2017 9:21 am **Posts:** 33

Geordi if the boost is going anywhere it’s back through the turbo in the milliseconds that’s you describe the volume of compressed air is metered by the cam duration and the valves arn’t open long enough to deplete the intake , Inter cooler, and hoses of compressed air. It’s not Just cubic feet at atmosphere but it compounded by the pressure at say 25 psig that when the combustion flow tapers off cannot put the work onto the turbine and the work is then done to the compressor spinning it backwards. Run away due to fuel injector injected fuel may not be something that happens often but there are scenarios where it could and the fcv would be the only way to choke by physically blocking the cac flow path so as to snuff out the reaction by making it fuel rich should an injector fail or valve seal leak. Using the fcv in this mannor it would be wise to vent the cac system so that you don grenade a turbo.
Saying it could never happen could be careless. I am really gracious for all of the input though it really helps to see the issue from all perspectives. I am sorry if this discussion is frustrating to you veterans.. I love reading this forum and have only just come into the money to be able to tinker with these things. I realize that leaves me open to we to tell me that I’m wasting my money but I just don’t see it that way and respect your opinion.

geordi · **Posted:** Sun Oct 27, 2019 12:29 am

This is a fundamental misunderstanding on how a diesel works. There is no "tapering off" of the combustion flow, when the throttle is released, the injectors are just OFF. Period. Instantly. There is never a restriction in the CRD airflow to slow it down or make it change direction. NEVER. "turbo bark" just does not happen.

The valves are absolutely open long enough to inhale the entire contents of the intake - that is exactly what they continue to do whenever the engine is running whether it is being driven by fuel injection events or from the spinning transmission. The air volume passing through the engine is actively being sucked in on the intake stroke, EACH CYLINDER has about a 4.5" diameter and about a 10" stroke. That is a HUGE volume of air and it absolutely changes position from the intake to the cylinder in the milliseconds that the valves are open.

Here's something else to consider about this that I hadn't really realized until tonight.
Let's say that the turbo is at max boost in the instant before the throttle is released. So there's 23psi in the intake. Because of the fuel and combustion happening, the exhaust MUST be under high temperature... BUT also high pressure to drive the turbine.

Cutting the throttle and opening the EGR is part of the factory software, this we know.

What I realized: We do NOT know what the actual pressure in the exhaust manifold is, and it is hot gas expanding at extreme velocity into the closed turbo vanes and driving the turbine through a very small gap - OR forcing its way into the intake through the EGR valve! Opening the EGR valve may not be letting boost OUT into the exhaust, it may just be letting EGR force its way IN to the intake right then - at the instant that fuel is cut from the injectors, there will be an excess of hot fueled gasses expanding and creating MORE pressure, and here's the EPA always wanting to capture the exhaust and re-burn it to ensure that there isn't any fuel leaving the engine.

Their programming is NOT about the turbo or protecting it, that isn't anywhere on the list of what the EPA cares about. But there is a very good chance that the drive pressure in the exhaust manifold is far higher than 23psi because of the gasses expanding. So opening the EGR would send MORE pressure to the intake... BUT IT STILL DOESN'T CAUSE TURBO BARK because the engine is right there dragging that air into the cylinders, and pumping it out past the now-opened vanes. The air is always being sucked in - it cannot be anything else.

Prove it to yourself with a MAF graph, this seems to be the easiest way. If there was to be a flow reversal, the MAF reading would have to drop to zero even for an instant. An ELM327 device should be fast enough to catch this.

WWDiesel · **Posted:** Sun Oct 27, 2019 2:04 am

Geordi, don't forget the role the FCV plays in the operation of the EGR flow.
When the engine is spinning hundreds of RPM's and you let off the go pedal and the injectors are no longer injecting fuel, the ECM closes off or chokes off the FCV.
When this happens, it is just like a throttle plate in a gasser. The piston are still trying to suck volumes of air into the combustion chamber so they create a negative pressure zone in the intake while the FCV is shut. At this point when the intake is at 0 pressure or under negative pressure, the EGR opens and injects spent exhaust gases into the intake.
Without the butterfly flapper plate in the FCV, the EGR could never get exhaust gasses into the intake because the majority of the time the intake would always be under pressure.
Diesels like my early Dodge that didn't come with an EGR system, have no need for a FCV.

Onnzo · **Joined:** Wed Jun 03, 2020 6:51 pm **Posts:** 2

Hi all - I don’t have a Jeep but have an OM642 3L V6 Turbo diesel in a Mercedes r300 which I believe is a common engine in certain Jeeps as well.

I recently noticed compressor flutter on my engine and have been searching to see if anyone else has the same issue. It seems like there is a fair bit of knowledge on this forum!

Below (sorry for the wall of text) is an overview and some videos of my the compressor surge. Since the below post, I’ve checked the actuator controlling the turbo vanes which seems to be working well and I also cleaned the egr pipe that feeds into the intake (it was full of crud). I’ve also ordered an icarsoft scan tool to see if it is throwing any codes.

Does anyone else have any thoughts or opinions?

OM642 3L Diesel Turbo Chatter/Surge and PCV leak.

Hi all - over the past couple of months I’ve taken this time to do a massive overhaul of my 2010 R300 CDI with the OM642.
It has hit 140k kms and i’ve had it for 90k kms of those. Up until recently, I didn’t notice any turbo surge/chatter when letting off the accelerator and it is really annoying me! I am also getting lots of blowby (as you can see in the video).

Firstly I have changed over my COMAND unit to a Kenwood double din and am waiting for the MOST amplifier converter so there is no music in the car currently. Maybe that is why I’m hearing all these sounds!

Re the overhaul, I’ve done, Lower ball joints, front airbag, front rotors/brake pads, transmission fluid, transfer case and both diffs and std engine oil and filter change.

Videos of the Turbo chatter / surge with intake on and off.

Intake on
https://youtu.be/3SWYPNniQmA

Intake off
https://youtu.be/KMK4IT7Sk_c

I originally thought the sound was drivetrain related (given the recent drivetrain work) but that was quickly dismissed as it happened in park/neutral. I then narrowed it down to turbo surge. I pulled the intake pipe from the front of the car and put my ear to it and it is definitely turbo surge.

Does anyone notice the surge in their cars (with the sound system off). It is prominent when lifting off at 1500 rpms plus revs (I guess when the turbo starts spooling). It is reverberating in the airbox and creating a grinding like sound but only sounds like that because of the reverberation in the intake system.

In the second clip you can see there is no grinding/whooshing sound with the air intake off.

After reading comments here, Im thinking the surge might be due to a Faulty turbo actuator (since checked) - The vanes not opening fully/quickly when lifting off (whilst the actuator is working the vanes might not be working properly due to crud buildup), or possible the intake valves sticking.

You can see the actuator moving much higher when the turbo is spooling at 2500 rpms to slow it down, compared to the small movement when revved to 1500rpm.

Im thinking if the exhaust side isn’t slowed, this will continue to create pressure in the intake valve which has no where to go except for out the intake system causing the noise.

Does anyone have any ideas what could be causing the surge?

TurboSmart BOV overboost and potential engine runaway soluti

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