DIY install blow off valve spacer (BOV) pshhh
03-06-2021 | 03:06 AM
#51
Member
Joined: May 2020
Posts: 183
Likes: 24
C450 AMG
This mod is total nonsense. The valve in question is not a blow-off valve. It is a priority valve (or compressor by-pass) that prevents turbo lag. Besides making more noise, letting that air escape to atmosphere increases turbo lag and deadens throttle response, because it defeats the action of the stock design.
Priority valves were first fitted to the Porsche 944 Turbo in 1988. Prior to that everyone used blow-off valves, where needed. Any company since, that made a good turbo system, used the priority valve setup. Audi, Porsche and Subaru are legendary examples. Priority valves are so important I actually welded fittings to my 1988 Celica GT-4 intercooler and intake box to adapt the clever Porsche 944/Audi part! Much improved the throttle response.
Now, racing turbo systems over about 2.5 bar do require a blow-off valve in addition to the priority valve function. Otherwise, the over-pressure in the intake risks splitting intercooler seams or blowing off hoses. The C-Class turbo systems are nowhere near requiring this mechanical pressure relief. The opposite is true. We want to keep that pressurized air working for us, not just **** it away.
Installing an aftermarket 'blow-off valve' defeats the clever function of the stock priority valve. The priority valve is there to remove turbo lag. It does this by recirculating the compressed air back into the atmospheric side. This keeps the compressor from stalling, so when you tip back into the throttle, it makes boost instantly. This is just as true at part throttle as full throttle. It works all the time.
There is also a very clever, simple delay spring built into the system, such that this factory priority valve system, once pulled open by manifold vacuum, resists closing for ~.1 to .3 seconds due to the resistance of this spring. This delay allows the turbocharger to spin up freely (no load) for an instant. As the valve comes completely closed, the turbine is now almost up to full rotational speed, so there is more boost available, much more when opening the throttle that without it.
If you want to understand this theory, put your hand over the suction of a household vacuum cleaner. The speed of the motor rises dramatically because, although still pulling a vacuum, it is doing no work (no air is moving). That is what the priority valve does for the turbocharger, specifically by adding pressure to the atmospheric side of the compressor wheel. It lets it freewheel momentarily and not loose rotational speed. Most important is the spring delay speeds up the turbine wheel further by there being no load on the compressor side.
-=m=-
Priority valves were first fitted to the Porsche 944 Turbo in 1988. Prior to that everyone used blow-off valves, where needed. Any company since, that made a good turbo system, used the priority valve setup. Audi, Porsche and Subaru are legendary examples. Priority valves are so important I actually welded fittings to my 1988 Celica GT-4 intercooler and intake box to adapt the clever Porsche 944/Audi part! Much improved the throttle response.
Now, racing turbo systems over about 2.5 bar do require a blow-off valve in addition to the priority valve function. Otherwise, the over-pressure in the intake risks splitting intercooler seams or blowing off hoses. The C-Class turbo systems are nowhere near requiring this mechanical pressure relief. The opposite is true. We want to keep that pressurized air working for us, not just **** it away.
Installing an aftermarket 'blow-off valve' defeats the clever function of the stock priority valve. The priority valve is there to remove turbo lag. It does this by recirculating the compressed air back into the atmospheric side. This keeps the compressor from stalling, so when you tip back into the throttle, it makes boost instantly. This is just as true at part throttle as full throttle. It works all the time.
There is also a very clever, simple delay spring built into the system, such that this factory priority valve system, once pulled open by manifold vacuum, resists closing for ~.1 to .3 seconds due to the resistance of this spring. This delay allows the turbocharger to spin up freely (no load) for an instant. As the valve comes completely closed, the turbine is now almost up to full rotational speed, so there is more boost available, much more when opening the throttle that without it.
If you want to understand this theory, put your hand over the suction of a household vacuum cleaner. The speed of the motor rises dramatically because, although still pulling a vacuum, it is doing no work (no air is moving). That is what the priority valve does for the turbocharger, specifically by adding pressure to the atmospheric side of the compressor wheel. It lets it freewheel momentarily and not loose rotational speed. Most important is the spring delay speeds up the turbine wheel further by there being no load on the compressor side.
-=m=-
Who told you all of this? LOL. First of all it’s not a priority valve or whatever else you called if. It’s a diverter valve and the only reason there’s no “blow off” valve on these cars is simply because most of the MB owners out there are snobby and don’t like the loud noise, so they opted out of putting them on the car making it harder on the life of the turbos, but hey.. what do they care? The yuppy snobs get their quiet Mercedes and Mercedes gets the money from the repairs down the road. Now for the spacers.. they are a big help in keeping boost pressure up through gear changes and release unwanted excess air so it’s not forced back into the engine creating unneeded pressure and forcing the engine to deal with the excess air which then creates your turbo lag, not the other way around. Plus these cars with the spacers installed aren’t that loud and they sound more manly and less girly when not installed. I hope whoever taught you how to work on cars didn’t teach you how to change the oil or put gas in the car the same way they taught you about turbos LOL! You’ll be a frequent customer in the service department. So please don’t go spreading this awful advice to anyone else.
Get the spacers if you’re not over the age of 80 and you want to add some cool noise to your car and save the life of your turbos.
P.S don’t listen to garbage info like this.
-The son of a Mercedes Benz engineer.
03-06-2021 | 11:52 AM
#52
MBWorld Fanatic!
Joined: Nov 2003
Posts: 2,235
Likes: 453
From: Earth
2015 C300 4Matic Sport
Who told you all of this? LOL. First of all it’s not a priority valve or whatever else you called if. It’s a diverter valve and the only reason there’s no “blow off” valve on these cars is simply because most of the MB owners out there are snobby and don’t like the loud noise, so they opted out of putting them on the car making it harder on the life of the turbos, but hey.. what do they care? The yuppy snobs get their quiet Mercedes and Mercedes gets the money from the repairs down the road. Now for the spacers.. they are a big help in keeping boost pressure up through gear changes and release unwanted excess air so it’s not forced back into the engine creating unneeded pressure and forcing the engine to deal with the excess air which then creates your turbo lag, not the other way around. Plus these cars with the spacers installed aren’t that loud and they sound more manly and less girly when not installed. I hope whoever taught you how to work on cars didn’t teach you how to change the oil or put gas in the car the same way they taught you about turbos LOL! You’ll be a frequent customer in the service department. So please don’t go spreading this awful advice to anyone else.
Get the spacers if you’re not over the age of 80 and you want to add some cool noise to your car and save the life of your turbos.
P.S don’t listen to garbage info like this.
-The son of a Mercedes Benz engineer.
Get the spacers if you’re not over the age of 80 and you want to add some cool noise to your car and save the life of your turbos.
P.S don’t listen to garbage info like this.
-The son of a Mercedes Benz engineer.
You don't get any credit for being the SON of anyone. Wut?
I can be the son of a rocket scientist, but that doesn't make me one.
Trying earning your own credentials bud.You also sound a bit butt hurt you can't afford a Mercedes.
Which isn't that difficult to achieve.
03-06-2021 | 02:11 PM
#53
Member
Joined: Aug 2016
Posts: 139
Likes: 79
From: Redondo Beach
20 E450 Luxury
A bit long on noise and a bit short on information?
A priority valve is just a clever diverter valve...as would have been clear from a more careful reading.
Or to quote San Francisco’s legendary Firesign Theater, “Don’t hear, I can shout you!” From their 1968 album “Waiting for the Electrician, or Someone Like Him” (a Covid relevant album, btw)
my teachers? lol...since you asked for it.
Roger Hildebrand for physics, at 18 an important member of the Manhatten Project, first both running and repairing the Berkeley cyclotron. He had a very distinguished career. I’d like to believe I paid attention in class.
Karl Zinner, trained a number of PhD turbo machinery engineers at Mannheim University, and a was a director at M.A.N. He wrote “Turbocharging” (Springer Verlag in German), still considered a seminal treatise on turbocharging.
Fritz Indra, late board member and design head at GM (Formerly Opel) Europe engines.bEarly in his career developed Alpina B6 and a consulting designer/developer of BMW F1 turbo motor.
There are also a couple of interesting projects I am, let us say, ‘aware of’. The TAG/Porsche F1 V6, which before testing work in an unnamed west coast American city could not make reliable power. Then, the Nissan IMSA GTP motor that could make 1200hp for fifteen seconds. It could simply pull out and pass a 962 Porsche on the second or last lap from the finish, but just often enough to win the championship. No need to be greedy.
In closing, the reference article to read (with decent English language extract) is, Motor Techinisch Zeitschrift 944T engine technical description. Probably Fall 1987 issue if I recall. It introduces the simple spring loaded priority valve concept in place of a simple diverter valve.
PS - My son is a forensic accountant and lawyer. What he can explain about cars is not very much and not very well. Get the drift?
Or to quote San Francisco’s legendary Firesign Theater, “Don’t hear, I can shout you!” From their 1968 album “Waiting for the Electrician, or Someone Like Him” (a Covid relevant album, btw)
my teachers? lol...since you asked for it.
Roger Hildebrand for physics, at 18 an important member of the Manhatten Project, first both running and repairing the Berkeley cyclotron. He had a very distinguished career. I’d like to believe I paid attention in class.
Karl Zinner, trained a number of PhD turbo machinery engineers at Mannheim University, and a was a director at M.A.N. He wrote “Turbocharging” (Springer Verlag in German), still considered a seminal treatise on turbocharging.
Fritz Indra, late board member and design head at GM (Formerly Opel) Europe engines.bEarly in his career developed Alpina B6 and a consulting designer/developer of BMW F1 turbo motor.
There are also a couple of interesting projects I am, let us say, ‘aware of’. The TAG/Porsche F1 V6, which before testing work in an unnamed west coast American city could not make reliable power. Then, the Nissan IMSA GTP motor that could make 1200hp for fifteen seconds. It could simply pull out and pass a 962 Porsche on the second or last lap from the finish, but just often enough to win the championship. No need to be greedy.
In closing, the reference article to read (with decent English language extract) is, Motor Techinisch Zeitschrift 944T engine technical description. Probably Fall 1987 issue if I recall. It introduces the simple spring loaded priority valve concept in place of a simple diverter valve.
PS - My son is a forensic accountant and lawyer. What he can explain about cars is not very much and not very well. Get the drift?
11-11-2022 | 11:29 AM
#54
Newbie
Joined: Nov 2022
Posts: 2
Likes: 0
CLS 400 Base
Does anybody have the install photos or video of how to install a passenger side blow off valve spacer on a C43/c450 3.0L TwinTurbo? somebody told me The passenger side turbo was upside down? I do t see from just looking under the hood. And there isn’t much on youtube worth watching. There’s an Asian chick trying to show us how to, but she was lost too. They sound great and I feel a difference in my shifts with just one so far
11-11-2022 | 12:42 PM
#55
MBWorld Fanatic!
Joined: Jun 2012
Posts: 1,013
Likes: 123
From: Toronto
2022 E53 AMG
I have this on my car... two of them as I have two turbos and love the sound. It does not give you any HP, it's just a sound.
Last edited by Cosworth2000; 12-15-2022 at 05:35 AM.
The following users liked this post:
dagger22 (11-14-2022)
01-16-2023 | 12:29 AM
#56
Junior Member
Joined: Jan 2022
Posts: 42
Likes: 13
C400
If you use a socket hex driver about 2" long or a little longer, it can be done entirely by feel. If you're near VT, I'll install it for ya once it's not freezing outside- it'll cost you a pizza and beer, though.
The following 2 users liked this post by VTSummit:
Darrington (01-16-2023),
Kush Desai (01-16-2023)
