Drivetrain The Detroit Tuned Bypass Valve
Joined: Feb 2003
Posts: 1,754
Likes: 36
From: Metro Detroit Area, Michigan
yes i do think the throttle response is improved. the drive by wire on the mini is a bit slow and the the valve makes it feel a bit more like the car has a throttle cable. this has also bee posted by other people here on NAM. just do a search for Detroit Tuned Bypass Valve.
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3rd Gear
Joined: Nov 2006
Posts: 197
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From: OBX, NC
Well said! I have owned 30-35 cars and the MCS is my favorite.
6th Gear
Joined: Mar 2006
Posts: 1,710
Likes: 1
From: Northampton MA
A +1 for "the MCS is my favorite" +2 counting my wife.
Back to the DT BPV. This is not a 1 size fits all mod, even DT would tell you the same. However, on the street, with cars I have seen, with this mod, there has been benifit. On the track, as Don - DMH points out, it is easy to understand how modulation would be effected with lower vacuum with the kind of acceleration & deceleration demands.
Understand the system first...
then knowing what the mod does is easier. The stock BPV opens when the car isn't under large loads so that the car will be more economical to drive.... When you floor it, it closes....
Changing how well it closes (like Chad and other have said) prevents boost leak through the valve. True enough. One pound of boost? Depends on how bad yours is to start.
Changing the spring (two variables here, lenght and stiffness) changes at what vacuum the valve opens, and how open it will go. This will show up as an earlier transition to closed (lower RPM or throttle body opening).
So, let's think about this a bit. Are there light throttle conditions where it's better to be off boost? Sure there are, and you don't want the new spring set such that you are "on boost" when you don't want it. This is somewhat a matter of taste...... I, like Don, found that light throttle modulation wasn't what I wanted, so I didn't use Ryan's spring. But I did like the concept, so a went half way, using a stock spring, but stretched it a bit.
IATs..... Now, despite what others claim, the SC doesn't relly heat the air too much, it's the compression of the air that happens when the air exists the SC that heats it..... (this has to do with the fact a Roots blower isn't a compressor!) So if you turn up the boost, then you turn up the heat. They go hand and hand...... But like Ryan says, once fully closed, there is no difference between the two.
So what's this all mean? It means that the DTBPV will close at lower vacuum. Is it at the best vacuum for you? Depends a lot. For Don and me, the answer was no. For others, the answer was yes.
As far as adjusting the butterfly and the stop? You can do that yourself without changing the spring. Get the boost (if it's there to be had) for just some time and effort.
If you want the spring, the plastic tabs on the diaphram a pretty fragile, so you may just want to buy the valve all done......
Matt
Changing how well it closes (like Chad and other have said) prevents boost leak through the valve. True enough. One pound of boost? Depends on how bad yours is to start.
Changing the spring (two variables here, lenght and stiffness) changes at what vacuum the valve opens, and how open it will go. This will show up as an earlier transition to closed (lower RPM or throttle body opening).
So, let's think about this a bit. Are there light throttle conditions where it's better to be off boost? Sure there are, and you don't want the new spring set such that you are "on boost" when you don't want it. This is somewhat a matter of taste...... I, like Don, found that light throttle modulation wasn't what I wanted, so I didn't use Ryan's spring. But I did like the concept, so a went half way, using a stock spring, but stretched it a bit.
IATs..... Now, despite what others claim, the SC doesn't relly heat the air too much, it's the compression of the air that happens when the air exists the SC that heats it..... (this has to do with the fact a Roots blower isn't a compressor!) So if you turn up the boost, then you turn up the heat. They go hand and hand...... But like Ryan says, once fully closed, there is no difference between the two.
So what's this all mean? It means that the DTBPV will close at lower vacuum. Is it at the best vacuum for you? Depends a lot. For Don and me, the answer was no. For others, the answer was yes.
As far as adjusting the butterfly and the stop? You can do that yourself without changing the spring. Get the boost (if it's there to be had) for just some time and effort.
If you want the spring, the plastic tabs on the diaphram a pretty fragile, so you may just want to buy the valve all done......
Matt
6th Gear
Joined: Mar 2006
Posts: 1,710
Likes: 1
From: Northampton MA
then knowing what the mod does is easier. The stock BPV opens when the car isn't under large loads so that the car will be more economical to drive.... When you floor it, it closes....
Changing how well it closes (like Chad and other have said) prevents boost leak through the valve. True enough. One pound of boost? Depends on how bad yours is to start.
Changing the spring (two variables here, lenght and stiffness) changes at what vacuum the valve opens, and how open it will go. This will show up as an earlier transition to closed (lower RPM or throttle body opening).
So, let's think about this a bit. Are there light throttle conditions where it's better to be off boost? Sure there are, and you don't want the new spring set such that you are "on boost" when you don't want it. This is somewhat a matter of taste...... I, like Don, found that light throttle modulation wasn't what I wanted, so I didn't use Ryan's spring. But I did like the concept, so a went half way, using a stock spring, but stretched it a bit.
IATs..... Now, despite what others claim, the SC doesn't relly heat the air too much, it's the compression of the air that happens when the air exists the SC that heats it..... (this has to do with the fact a Roots blower isn't a compressor!) So if you turn up the boost, then you turn up the heat. They go hand and hand...... But like Ryan says, once fully closed, there is no difference between the two.
So what's this all mean? It means that the DTBPV will close at lower vacuum. Is it at the best vacuum for you? Depends a lot. For Don and me, the answer was no. For others, the answer was yes.
As far as adjusting the butterfly and the stop? You can do that yourself without changing the spring. Get the boost (if it's there to be had) for just some time and effort.
If you want the spring, the plastic tabs on the diaphram a pretty fragile, so you may just want to buy the valve all done......
Matt
Changing how well it closes (like Chad and other have said) prevents boost leak through the valve. True enough. One pound of boost? Depends on how bad yours is to start.
Changing the spring (two variables here, lenght and stiffness) changes at what vacuum the valve opens, and how open it will go. This will show up as an earlier transition to closed (lower RPM or throttle body opening).
So, let's think about this a bit. Are there light throttle conditions where it's better to be off boost? Sure there are, and you don't want the new spring set such that you are "on boost" when you don't want it. This is somewhat a matter of taste...... I, like Don, found that light throttle modulation wasn't what I wanted, so I didn't use Ryan's spring. But I did like the concept, so a went half way, using a stock spring, but stretched it a bit.
IATs..... Now, despite what others claim, the SC doesn't relly heat the air too much, it's the compression of the air that happens when the air exists the SC that heats it..... (this has to do with the fact a Roots blower isn't a compressor!) So if you turn up the boost, then you turn up the heat. They go hand and hand...... But like Ryan says, once fully closed, there is no difference between the two.
So what's this all mean? It means that the DTBPV will close at lower vacuum. Is it at the best vacuum for you? Depends a lot. For Don and me, the answer was no. For others, the answer was yes.
As far as adjusting the butterfly and the stop? You can do that yourself without changing the spring. Get the boost (if it's there to be had) for just some time and effort.
If you want the spring, the plastic tabs on the diaphram a pretty fragile, so you may just want to buy the valve all done......
Matt
5th Gear
Joined: Dec 2006
Posts: 727
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Originally Posted by jeffc;1324442[B
]I have a 2002 MCS and love it[/b].
Looks like I have to install the DT BPV soon. I'm getting that yo yo effect when on full throttle past 6000 rmp. I will have to have the shop call Chad and order me one soon enough. I also want to do the VGS while doing the BPV installation.
+1
I just want on/off feel to throttle pedal (on mostly)
then knowing what the mod does is easier. The stock BPV opens when the car isn't under large loads so that the car will be more economical to drive.... When you floor it, it closes....
Changing how well it closes (like Chad and other have said) prevents boost leak through the valve. True enough. One pound of boost? Depends on how bad yours is to start.
Changing the spring (two variables here, lenght and stiffness) changes at what vacuum the valve opens, and how open it will go. This will show up as an earlier transition to closed (lower RPM or throttle body opening).
So, let's think about this a bit. Are there light throttle conditions where it's better to be off boost? Sure there are, and you don't want the new spring set such that you are "on boost" when you don't want it. This is somewhat a matter of taste...... I, like Don, found that light throttle modulation wasn't what I wanted, so I didn't use Ryan's spring. But I did like the concept, so a went half way, using a stock spring, but stretched it a bit.
IATs..... Now, despite what others claim, the SC doesn't relly heat the air too much, it's the compression of the air that happens when the air exists the SC that heats it..... (this has to do with the fact a Roots blower isn't a compressor!) So if you turn up the boost, then you turn up the heat. They go hand and hand...... But like Ryan says, once fully closed, there is no difference between the two.
So what's this all mean? It means that the DTBPV will close at lower vacuum. Is it at the best vacuum for you? Depends a lot. For Don and me, the answer was no. For others, the answer was yes.
As far as adjusting the butterfly and the stop? You can do that yourself without changing the spring. Get the boost (if it's there to be had) for just some time and effort.
If you want the spring, the plastic tabs on the diaphram a pretty fragile, so you may just want to buy the valve all done......
Matt
Changing how well it closes (like Chad and other have said) prevents boost leak through the valve. True enough. One pound of boost? Depends on how bad yours is to start.
Changing the spring (two variables here, lenght and stiffness) changes at what vacuum the valve opens, and how open it will go. This will show up as an earlier transition to closed (lower RPM or throttle body opening).
So, let's think about this a bit. Are there light throttle conditions where it's better to be off boost? Sure there are, and you don't want the new spring set such that you are "on boost" when you don't want it. This is somewhat a matter of taste...... I, like Don, found that light throttle modulation wasn't what I wanted, so I didn't use Ryan's spring. But I did like the concept, so a went half way, using a stock spring, but stretched it a bit.
IATs..... Now, despite what others claim, the SC doesn't relly heat the air too much, it's the compression of the air that happens when the air exists the SC that heats it..... (this has to do with the fact a Roots blower isn't a compressor!) So if you turn up the boost, then you turn up the heat. They go hand and hand...... But like Ryan says, once fully closed, there is no difference between the two.
So what's this all mean? It means that the DTBPV will close at lower vacuum. Is it at the best vacuum for you? Depends a lot. For Don and me, the answer was no. For others, the answer was yes.
As far as adjusting the butterfly and the stop? You can do that yourself without changing the spring. Get the boost (if it's there to be had) for just some time and effort.
If you want the spring, the plastic tabs on the diaphram a pretty fragile, so you may just want to buy the valve all done......
Matt
or it could be a lean surge , are you afs okay?
Banned
Joined: Jun 2006
Posts: 2,381
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"Well, there you go: "the vast majority of the community says that it will improve throttle response and that previous testing has proven that DT BPV may not raise IATs all that much." It must be good then!"[/QUOTE]
Well there where do I send my check.
Well there where do I send my check.
OVERDRIVE
Joined: May 2003
Posts: 7,926
Likes: 40
From: Greensboro, NC
then knowing what the mod does is easier. The stock BPV opens when the car isn't under large loads so that the car will be more economical to drive.... When you floor it, it closes....
Changing how well it closes (like Chad and other have said) prevents boost leak through the valve. True enough. One pound of boost? Depends on how bad yours is to start.
Changing the spring (two variables here, lenght and stiffness) changes at what vacuum the valve opens, and how open it will go. This will show up as an earlier transition to closed (lower RPM or throttle body opening).
So, let's think about this a bit. Are there light throttle conditions where it's better to be off boost? Sure there are, and you don't want the new spring set such that you are "on boost" when you don't want it. This is somewhat a matter of taste...... I, like Don, found that light throttle modulation wasn't what I wanted, so I didn't use Ryan's spring. But I did like the concept, so a went half way, using a stock spring, but stretched it a bit.
IATs..... Now, despite what others claim, the SC doesn't relly heat the air too much, it's the compression of the air that happens when the air exists the SC that heats it..... (this has to do with the fact a Roots blower isn't a compressor!) So if you turn up the boost, then you turn up the heat. They go hand and hand...... But like Ryan says, once fully closed, there is no difference between the two.
So what's this all mean? It means that the DTBPV will close at lower vacuum. Is it at the best vacuum for you? Depends a lot. For Don and me, the answer was no. For others, the answer was yes.
As far as adjusting the butterfly and the stop? You can do that yourself without changing the spring. Get the boost (if it's there to be had) for just some time and effort.
If you want the spring, the plastic tabs on the diaphram a pretty fragile, so you may just want to buy the valve all done......
Matt
Changing how well it closes (like Chad and other have said) prevents boost leak through the valve. True enough. One pound of boost? Depends on how bad yours is to start.
Changing the spring (two variables here, lenght and stiffness) changes at what vacuum the valve opens, and how open it will go. This will show up as an earlier transition to closed (lower RPM or throttle body opening).
So, let's think about this a bit. Are there light throttle conditions where it's better to be off boost? Sure there are, and you don't want the new spring set such that you are "on boost" when you don't want it. This is somewhat a matter of taste...... I, like Don, found that light throttle modulation wasn't what I wanted, so I didn't use Ryan's spring. But I did like the concept, so a went half way, using a stock spring, but stretched it a bit.
IATs..... Now, despite what others claim, the SC doesn't relly heat the air too much, it's the compression of the air that happens when the air exists the SC that heats it..... (this has to do with the fact a Roots blower isn't a compressor!) So if you turn up the boost, then you turn up the heat. They go hand and hand...... But like Ryan says, once fully closed, there is no difference between the two.
So what's this all mean? It means that the DTBPV will close at lower vacuum. Is it at the best vacuum for you? Depends a lot. For Don and me, the answer was no. For others, the answer was yes.
As far as adjusting the butterfly and the stop? You can do that yourself without changing the spring. Get the boost (if it's there to be had) for just some time and effort.
If you want the spring, the plastic tabs on the diaphram a pretty fragile, so you may just want to buy the valve all done......
Matt
During my testing with heavier springs, temperatures in the output side of the SC (pre IC) consistantly rose by over 50F during light load (off boost) such as a steady cruise state at 80mph...my guess is that the heavy springed valve has shut in this low vacuum window and thus the SC is pumping against itself?
I like to know what your take on this is Matt...
Last edited by MSFITOY; Jun 10, 2007 at 06:54 AM.
1st Gear
Joined: May 2006
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I own a 2006 MCS. Dinan CAI and inital Dinan software upgrade. No other mods. Experience stumbling starts 2/4, no start 1/4 and clean start 1/4 of time on first turn of the key. No correlation between results and temp, time of day, whether recently driven or not, brand of gas (always 93 oct), etc. Also experience (by feel, not by discernable movement of the tach) hesitation when accelerating, easing off/and after easing off and steady pedal, especially between 3K and 4K. Little hesitation noted below 3K and just two or three "spots" when steadily or quickly accelerating beyond 4K to redline. My desire is for car to always start on first turn of the key and--much more importantly--to be able to smoothly accelerate, ease off or hold steady pedal. Am considering DTBPV for possible cure or improvement. I have read this and a number of other threads on BPV. There appears to be an assumption that the stock BPV is poorly constructed because it does not close all the way when the set screw would otherwise allow it to do so; but there IS a set scew and it is set to not allow the butterfly to close. It would seem that "light around the butterfly" is of little concern to if it is already intended to be open to some degree at all times. And WHY has the stock BPV been intentionally set to be somewhat open in the first place? Has anyone experimented with adjustments only to the set screw setting without other changes to the BPV? Would appreciate any comments/answers. Thanks, Odas
good question!
I own a 2006 MCS. Dinan CAI and inital Dinan software upgrade. No other mods. Experience stumbling starts 2/4, no start 1/4 and clean start 1/4 of time on first turn of the key. No correlation between results and temp, time of day, whether recently driven or not, brand of gas (always 93 oct), etc. Also experience (by feel, not by discernable movement of the tach) hesitation when accelerating, easing off/and after easing off and steady pedal, especially between 3K and 4K. Little hesitation noted below 3K and just two or three "spots" when steadily or quickly accelerating beyond 4K to redline. My desire is for car to always start on first turn of the key and--much more importantly--to be able to smoothly accelerate, ease off or hold steady pedal. Am considering DTBPV for possible cure or improvement. I have read this and a number of other threads on BPV. There appears to be an assumption that the stock BPV is poorly constructed because it does not close all the way when the set screw would otherwise allow it to do so; but there IS a set scew and it is set to not allow the butterfly to close. It would seem that "light around the butterfly" is of little concern to if it is already intended to be open to some degree at all times. And WHY has the stock BPV been intentionally set to be somewhat open in the first place? Has anyone experimented with adjustments only to the set screw setting without other changes to the BPV? Would appreciate any comments/answers. Thanks, Odas
Yes...
what happens is you get slightly increasing peak boost until the little sucker is limited by the bore, and not the set screw. If this is bad enough, it starts to stick on it transitions before it opens, and this shows up as some smoothness issue or a "stumble".
But this is probably easier to test yourself than you think! Turn the set screw and see what happens! If it won't go, heat it a bit as they're useing a thread locker.
The gap is a manufacturing tolerance issue.
Matt
ps, when I read the original post I had to chuckle. These changes to the stock valve were CREATED to deal with drivability issues on the early new Minis...
But this is probably easier to test yourself than you think! Turn the set screw and see what happens! If it won't go, heat it a bit as they're useing a thread locker.
The gap is a manufacturing tolerance issue.
Matt
ps, when I read the original post I had to chuckle. These changes to the stock valve were CREATED to deal with drivability issues on the early new Minis...
1st Gear
Joined: May 2006
Posts: 35
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what happens is you get slightly increasing peak boost until the little sucker is limited by the bore, and not the set screw. If this is bad enough, it starts to stick on it transitions before it opens, and this shows up as some smoothness issue or a "stumble".
But this is probably easier to test yourself than you think! Turn the set screw and see what happens! If it won't go, heat it a bit as they're useing a thread locker.
The gap is a manufacturing tolerance issue.
Matt
ps, when I read the original post I had to chuckle. These changes to the stock valve were CREATED to deal with drivability issues on the early new Minis...
But this is probably easier to test yourself than you think! Turn the set screw and see what happens! If it won't go, heat it a bit as they're useing a thread locker.
The gap is a manufacturing tolerance issue.
Matt
ps, when I read the original post I had to chuckle. These changes to the stock valve were CREATED to deal with drivability issues on the early new Minis...
Good to hear from you Matt.
Have read many of your inputs. Gather from what you have said here that (1) in your experience, some butterfly tolerances are so far off that they stop closing even before the set screw comes into play; (2) that, likewise, in your experience, the butterfly tolerances are so far off that the butterfly hangs during transitions; and (3) that earliest BPVs didn't have a set screw and that it was added to help solve driveability problems (I can see the basis for the chuckle
.) That the gap is indeed a manufacturing issue, I can believe. I do plan to adjust the stock set screw and see what results. Thanks, Odas
5th Gear
Joined: Dec 2006
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Here is what I have been experiancing since changing to DT BPV. I have a slight but noticable hesitation or rather what I like to call it a "DEAD SPOT" where this hesitation starts when your gradually accelerating between the 3-4k rpm, this happenes only in vaccum or right around "0" boost. The hesitation is evident when the load is slightly steady and the boost is at or below "0" and the RPM between 3-4k. This hesitation goes away when in boost or post 0.
Any idea why this is happening?
Any idea why this is happening?
Deja Vu all over again...
Each car respondes differenty. This is because of the ECU software (I think). Read "The Yo-Yo Chronicles" (I think that's the thread name) for hours and hours and hours of debates on this.
The first valves did have the set screw stop, it just wasn't thread locked at the factory setting. The tolerances are from huge gaps to none as the valve comes from the factory, in general, the earlier ones had more spread than the newer.
The consensus now seems to be that the gap shouldn't be gone all the way (sticking) but as small as you can make it.
The spring in the DT valve changes when, how fast, and how far the valve opens. Some love the "snappy" feel of the sudden transition, some not so much. This is a matter of personal taste.
I think the ECU doesn't know exactly what to do (in some software revs) as it will see different pre and post SC pressures, and the pre is used for the drive by wire system the sets the opening of the throttle body.
BUT, there are many sources that can cause the flat spot. Some found the DT valve (search on RyePhix II, I think) makes it better, some worse. Andy Smith from Ross-Tech (doesn't post here much anymore) coined the phrase "Vacuum Gain System" for a mod that involves getting the vaccum for the valve from the post SC vac lines, as opposed to how it's plummed stock ,from between the TB and the SC. Some have had this improve the flat spot, some it makes it worse. No matter what, make sure that you don't have leaks, and if you use standard vacuum hose for any mod in this area, make sure to wire tie it tight, as the post SC side sees both vacuum and boost, and the rubber hoses can expand a bit and leak or slide off the nippels (quite a few have come off at the fuel pressure regulator if you don't wire tie, mine included once).
Hope this short version helps, there's litterlay hundreds of pages on this if you take the time to read it. Sadly, there is no universal fix or expalanation that covers every combinations of symptoms and changes.
Matt
The first valves did have the set screw stop, it just wasn't thread locked at the factory setting. The tolerances are from huge gaps to none as the valve comes from the factory, in general, the earlier ones had more spread than the newer.
The consensus now seems to be that the gap shouldn't be gone all the way (sticking) but as small as you can make it.
The spring in the DT valve changes when, how fast, and how far the valve opens. Some love the "snappy" feel of the sudden transition, some not so much. This is a matter of personal taste.
I think the ECU doesn't know exactly what to do (in some software revs) as it will see different pre and post SC pressures, and the pre is used for the drive by wire system the sets the opening of the throttle body.
BUT, there are many sources that can cause the flat spot. Some found the DT valve (search on RyePhix II, I think) makes it better, some worse. Andy Smith from Ross-Tech (doesn't post here much anymore) coined the phrase "Vacuum Gain System" for a mod that involves getting the vaccum for the valve from the post SC vac lines, as opposed to how it's plummed stock ,from between the TB and the SC. Some have had this improve the flat spot, some it makes it worse. No matter what, make sure that you don't have leaks, and if you use standard vacuum hose for any mod in this area, make sure to wire tie it tight, as the post SC side sees both vacuum and boost, and the rubber hoses can expand a bit and leak or slide off the nippels (quite a few have come off at the fuel pressure regulator if you don't wire tie, mine included once).
Hope this short version helps, there's litterlay hundreds of pages on this if you take the time to read it. Sadly, there is no universal fix or expalanation that covers every combinations of symptoms and changes.
Matt
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