Drivetrain Aftermarket Bypass Valves and Fuel Mileage - why?
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1st Gear
Joined: Jan 2007
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Aftermarket Bypass Valves and Fuel Mileage - why?
My wife has the CooperS, I am merely the pit crew and I am looking to buy a Detroit Tuned Bypass valve at MOTD this year for her birthday.
In other threads, people have mentioned installing a DT BTV vs. OEM affects fuel mileage, or the first question asked to someone who installed a DT BPV is "How much did it change your mileage?"
Why would an aftermarket bypass valve, from any vendor, make you lose mileage when compared to a correctly functioning stock valve? Both valves are supposed to hold the same boost pressures, just the Detroit Tuned does a better job of it (I think). I can understand having better mileage when unknowingly running a leaking bypass valve (as boost pressures are lower so there's less fuel required), but when comparing OEM new vs. DT new, mileage should be equal.
Right?
In other threads, people have mentioned installing a DT BTV vs. OEM affects fuel mileage, or the first question asked to someone who installed a DT BPV is "How much did it change your mileage?"
Why would an aftermarket bypass valve, from any vendor, make you lose mileage when compared to a correctly functioning stock valve? Both valves are supposed to hold the same boost pressures, just the Detroit Tuned does a better job of it (I think). I can understand having better mileage when unknowingly running a leaking bypass valve (as boost pressures are lower so there's less fuel required), but when comparing OEM new vs. DT new, mileage should be equal.
Right?
6th Gear
Joined: Jul 2004
Posts: 2,664
Likes: 1
From: Orlando, FL
I think the deal is that aftermarket valves, along with sealing more completely, include a stiffer spring. This spring causes the valve to close sooner. Closed valve means more air into the engine, which means more fuel needs to be added to maintain correct A/F ratio, which results in lower gas mileage.
My wife has the CooperS, I am merely the pit crew and I am looking to buy a Detroit Tuned Bypass valve at MOTD this year for her birthday.
In other threads, people have mentioned installing a DT BTV vs. OEM affects fuel mileage, or the first question asked to someone who installed a DT BPV is "How much did it change your mileage?"
Why would an aftermarket bypass valve, from any vendor, make you lose mileage when compared to a correctly functioning stock valve? Both valves are supposed to hold the same boost pressures, just the Detroit Tuned does a better job of it (I think). I can understand having better mileage when unknowingly running a leaking bypass valve (as boost pressures are lower so there's less fuel required), but when comparing OEM new vs. DT new, mileage should be equal.
Right?
In other threads, people have mentioned installing a DT BTV vs. OEM affects fuel mileage, or the first question asked to someone who installed a DT BPV is "How much did it change your mileage?"
Why would an aftermarket bypass valve, from any vendor, make you lose mileage when compared to a correctly functioning stock valve? Both valves are supposed to hold the same boost pressures, just the Detroit Tuned does a better job of it (I think). I can understand having better mileage when unknowingly running a leaking bypass valve (as boost pressures are lower so there's less fuel required), but when comparing OEM new vs. DT new, mileage should be equal.
Right?
do a search for yo-yo effect , i am sure you will find a better explanation than i can give.
Thread Starter
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1st Gear
Joined: Jan 2007
Posts: 26
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OK, I'll agree with that - I guess that spring being considerably stiffer would result in the car being "on boost" faster. I thought the spring would be more for holding the boost, but what you say makes sense.
Thanks for the quick response.
Thanks for the quick response.
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1st Gear
Joined: Jan 2007
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RatBlast,
Didn't even see your response last night - sorry to not acknowledge it. My wife's S does have a weakened valve which is why are changing it out. After meeting the folks from Detroit Tuned at MOTD last year they're getting my business - I just couldn't wrap my head around the reported drop in mileage.
Didn't even see your response last night - sorry to not acknowledge it. My wife's S does have a weakened valve which is why are changing it out. After meeting the folks from Detroit Tuned at MOTD last year they're getting my business - I just couldn't wrap my head around the reported drop in mileage.
RatBlast,
Didn't even see your response last night - sorry to not acknowledge it. My wife's S does have a weakened valve which is why are changing it out. After meeting the folks from Detroit Tuned at MOTD last year they're getting my business - I just couldn't wrap my head around the reported drop in mileage.
Didn't even see your response last night - sorry to not acknowledge it. My wife's S does have a weakened valve which is why are changing it out. After meeting the folks from Detroit Tuned at MOTD last year they're getting my business - I just couldn't wrap my head around the reported drop in mileage.
thanx for the reply
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