To BOV or not
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TriggrPullrUSMC (07-18-2022)
#28
Junior Member
Just installed my renntech BOV adapter and took them off within 10 minutes of driving. Performance impact aside... makes it borderline embarrassing to drive in public.
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TriggrPullrUSMC (07-18-2022)
#29
Member
Flow of air through the compressor wheel isn't what creates boost pressure though, it's exhaust gases. I am unconvinced that the split second release of air into the intake box will keep the turbo spooled up, but I could be wrong. Just never heard of this before. Traditionally, anti lag would be used to keep the turbo spooled between shifts.
The stock electronically controlled diverter/bypass valve will redirect pressurized air from the turbo output to the low pressure (turbo input) side. Thus, the turbo input pressure will increase a bit (above the normal atmospheric-ish pressure), and less air would need to flow through the air filter.
More importantly, the electronically controlled stock valve brings the turbo output pressure to near the turbo input pressure. If the input and output sides of the turbo are kept at near equal pressures, there will be minimal resistance, so the turbo will keep spinning for longer.
If you install a BOV, in addition to pissing away pressurized air (a slight loss, as the stock setup will slightly pressurize the turbo input side), the bigger impact is that the BOV will cause the output side of the turbo to remain at an elevated pressure (the BOV pressure needed to overcome its spring). This increased output side pressure when you’re off the throttle (electronically controlled diverter valve open, output redirected to aftermarket mechanical BOV) will actively slow down the turbo, causing turbo lag after shifts or letting off the throttle.
In short, installing a “BOV” on these engines is counterproductive and creates turbo lag.
Last edited by wizee; 06-14-2020 at 12:32 AM.
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#30
#31
Member
I haven’t looked at the construction of the Renntech BOV. If you connect the “BOV” to the bypass path of the electronic diverter valve, you could get away with a blow off “whistle” instead of a valve, since there’s no need for a spring. In this case, there could be less pressure drop across the whistle than in a true BOV, but there would still be some pressure drop, and still a waste of pressurized air.
#32
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'18 AMG GTC, '96 BMW 318i, '10 Audi Q5 (wife)
I have never understood the appeal of a BOV. There is a lot of engineering effort in making turbo engines behave and sound like NA while overcoming or masking the downsides of turbos. BOVs go in the opposite direction. If you like BOVs, great. I just don't get it.
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peejalino (06-16-2020)
#34
You are confusing two different things here.
Recirculating the air is NOT about stopping air from "banging against the compressor wheel." The purpose of a BLOW OFF VALVE (which is NOT what the products being discussed here are) is for cars running HIGH BOOST. The GT family of cars from AMG do NOT run high boost. Without a blow off valve, cars with HIGH BOOST, will have issues when you let off the throttle because pressurized air will stall the turbo wheel or rupture pipes/hoses. This will not happen with these AMG cars. So a blow off valve is not needed.
Recirculating the air with the type of valve these cars have helps the turbo stay spinning a bit between gear shifts and when you let off the throttle.
Ask yourself this question: if recirculating the air does nothing, why would a large company like Mercedes, that most likely does everything possible to reduce redundant manufacturing procedures in order to save money and reduce cost... why would they utilize a system that does nothing? They wouldn't. That should tell you something about why they chose to use the type of recirculating valve these cars have. It's not for emissions. And it's not to keep the car quiet.
Tell you what, write a letter to Mercedes/AMG engineers and R&D and tell them the way they build the engine is wrong. I'm sure they'd love to know.
Recirculating the air is NOT about stopping air from "banging against the compressor wheel." The purpose of a BLOW OFF VALVE (which is NOT what the products being discussed here are) is for cars running HIGH BOOST. The GT family of cars from AMG do NOT run high boost. Without a blow off valve, cars with HIGH BOOST, will have issues when you let off the throttle because pressurized air will stall the turbo wheel or rupture pipes/hoses. This will not happen with these AMG cars. So a blow off valve is not needed.
Recirculating the air with the type of valve these cars have helps the turbo stay spinning a bit between gear shifts and when you let off the throttle.
Ask yourself this question: if recirculating the air does nothing, why would a large company like Mercedes, that most likely does everything possible to reduce redundant manufacturing procedures in order to save money and reduce cost... why would they utilize a system that does nothing? They wouldn't. That should tell you something about why they chose to use the type of recirculating valve these cars have. It's not for emissions. And it's not to keep the car quiet.
Tell you what, write a letter to Mercedes/AMG engineers and R&D and tell them the way they build the engine is wrong. I'm sure they'd love to know.
as far as the technical argument you are making I have absolutely no idea so I have to accept your point. My only comment is that I have read somewhere that any excess boost is fed back to the system to burn off any unburnt fuel for emissions targets but I don’t know how or where that happens.
#35
Junior Member
Yeah, I'm a salty ******* for sure lol. Just seems strange that a dude is like Why? It's explained. He says "I'm not convinced. But again, why?" It's explained again. "Yeah, I'm not convinced..." Just going in circles. Believe it or not. Buy a fake BOV or not. Whatever.
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ZAC MOTORSPORT (07-18-2022)
#36
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2017 C63s AMG - 2011 CL65 AMG - 2015 G63 AMG
You are SO VERY WRONG and believe you’re right. Think about it, the air box IS CONNECTED TO THE ATMOSPHERE! Therefore, installing the spacer simply vents it to the SAME ATMOSPHERE that the stock recirculating valve vents to. BOV spacer neither harms or benefits performance, IT ONLY ADDS SOUND. The air box in no way holds pressure, as air filters are DESIGNED to be as unrestrictive as possible. Therefore, the extra “air” from the recirculating valve simply escapes out the air filters. AMG designed a recirculating valve instead of venting to atmosphere because NOT EVERYONE LIKES THE SOUND.
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axelwphoto (04-28-2024)
#37
Junior Member
Yes reading through the thread just frustrates me, seeing how obviously wrong he is but how he attacks you even though you are right. It simply takes a bit of common sense and understanding of simple engineering principles to figure out the function of the recirculating valve.
#38
FWIW that noise is a bit too boy racer for me.
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user33 (04-29-2024)
#39
so how would one hook up a blow off valve or a "noise maker" to the M278 engine? A rich neighborhood kid approached me and would like to waste some of his daddys money...help...haha
#40
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Bentley Continental GT; AMG GT
This is the AMG GTxxx forum and probably not the best place for info on the M278, but there is a forum vendor that probably could help you (or your rich neighbor) out. Try here:
M157 / M278 Meth / BOV Kits - MBWorld.org Forums
Best,
#41
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AMGs :)
It's not a performance mod. In fact, it retards performance. The stock setup is what it is for a reason. It recirculates pressurized air back into the manifold to keep the turbos spooled between shifts. This reduces turbo lag. Install the faux BOV (not really a BOV in reality), and you are actually making the car slower just to have a cool sound.
There is no performance gain to a BOV spacer though, you are right there.
EDIT, become a part of a bit of a gravedig here, sorry.
Last edited by ZAC MOTORSPORT; 07-18-2022 at 04:21 AM.
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#42
Disregard sorry...
Last edited by TriggrPullrUSMC; 07-18-2022 at 10:19 AM.
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#45
Early indicator of a soon-to-be car enthusiast? Seriously, I bet many of us did this as kids. #;-) Personally, I still think BOVs and "crackle tunes" sound silly ... but I respect that others like things I don't.