Has anyone done a similar before/after dyno test on a NA car by removing the VVIS or capping the hose (opening the butterflies)?
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Boost and VVIS
- Thread starter the nsxnut
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Larry Bastanza said:
But nsxnut stated that pulling the line (zero vacuum) leaves the butterfles open, which is the opposite of what you describe. So if "open" is for lower velocity but higher flow, then my previously described approach should work, which is both better and simpler than add-ons to trigger by RPM. But it also still leaves me wondering why they aren't open under boost.
I think one of my earlier points was missed by some people. Keeping the VVIS and modifying it (if necessary) to open properly under boost to simulate stock operation may be worth considering with the BBSC due to it's relative lack of (verly) low end boost. According to the tests noted above it was worth ~20 lb/ft of torque right in the meat of daily driving RPM. I'd say that's worth having. At the same time, opening them netted ~10% in the "performance" range. What we don't know is how much more top-end power could be had by pulling it out all together. No doubt some, but enough to give up that early torque?
Now F-X informs us that they run without one entirely and it's worth a lot of ponies, which makes sense. But I'm assuming that the difference they observed was compared to the butterflies not opening at all if nsxnut is correct in his assertions, so we still don't know how restrictive the extra hardware is when operating as designed. Still, as I implied above, I think that complete removal makes sense for positive displacement SCs such as CT because they can produce significant boost at those RPM, and turbos even more so.
It would be very interesting is nsxnut could finish tuning with his by-pass mod, then remove the entire VVIS and re-tune to see what difference that makes.
Now F-X informs us that they run without one entirely and it's worth a lot of ponies, which makes sense. But I'm assuming that the difference they observed was compared to the butterflies not opening at all if nsxnut is correct in his assertions, so we still don't know how restrictive the extra hardware is when operating as designed. Still, as I implied above, I think that complete removal makes sense for positive displacement SCs such as CT because they can produce significant boost at those RPM, and turbos even more so.
It would be very interesting is nsxnut could finish tuning with his by-pass mod, then remove the entire VVIS and re-tune to see what difference that makes.
Why, Rob, I'm sure you know the good old dirty-cheating-bastard practice of never showing your hand
. After all, I have to play these cards with you at the table next week at Sebring . Indeed, how much HP are YOU bringing ? If I'm not mistaken, you have a few dirty-cheating-bastard tricks up your voluminous sleeves, no?I do too, sjs. Can't explain why it didn't function, only that it didn't. The difference was meaurable on the Dynojet, as well as the ButtDyno!
Steve,
I get it. Vacuum "pulls" them closed when the ECU decides. I had it backwards. Now I understand your idea about bleeding the valve input hose to atmosphere to open the butterflies. Makes total sense.
Thanks,
LarryB
I get it
. Vacuum "pulls" them closed when the ECU decides. I had it backwards. Now I understand your idea about bleeding the valve input hose to atmosphere to open the butterflies. Makes total sense.Thanks,
LarryB
On just a little over 5psi she put down close to 400rwhp on the Dynapacks. This is much higher than the previous Bell’s we have had on the dyno. Those are killer numbers!! What a post. Hats off to all of you that came up with this idea. As mentioned above watch out for a lean condition when making this mod. Dan
Been there, done that
To anyone with experience with forced induction intake design, this would have been a pretty obvious decision. The stock intake is designed to exploit harmonics that only work in NA applications.
To anyone with experience with forced induction intake design, this would have been a pretty obvious decision. The stock intake is designed to exploit harmonics that only work in NA applications.
Re: Been there, done that
More accurately, to someone knowledgeable in VVIS and similar systems. For example, I think Corky would be considered plenty experienced with forced induction, but not up to speed on modern variable intake design.
Besides, we have long discussed the idea of pulling it out entirely and assumed it to be worth doing on most boosted cars. That’s no revelation, but it also isn’t the point. The excitement here is for the fact that Mark seems to have discovered that the VVIS "malfunctions" under boost, not even functioning (mechanically) as intended, and that by rectifying the problem you gain back considerable HP. If true, that's huge for people not interested in yanking the VVIS out entirely. And as also noted above, we still don't really know how much more would be gained by such surgery anyway, yet.
David said:
More accurately, to someone knowledgeable in VVIS and similar systems. For example, I think Corky would be considered plenty experienced with forced induction, but not up to speed on modern variable intake design.
Besides, we have long discussed the idea of pulling it out entirely and assumed it to be worth doing on most boosted cars. That’s no revelation, but it also isn’t the point. The excitement here is for the fact that Mark seems to have discovered that the VVIS "malfunctions" under boost, not even functioning (mechanically) as intended, and that by rectifying the problem you gain back considerable HP. If true, that's huge for people not interested in yanking the VVIS out entirely. And as also noted above, we still don't really know how much more would be gained by such surgery anyway, yet.
Re: Re: Been there, done that
Originally posted by sjs
More accurately, to someone knowledgeable in VVIS and similar systems. For example, I think Corky would be considered plenty experienced with forced induction, but not up to speed on modern variable intake design.
I consider VVIS to be a subset of intake design, but I guess I could be wroing.
Besides, we have long discussed the idea of pulling it out entirely and assumed it to be worth doing on most boosted cars. That’s no revelation, but it also isn’t the point.
My bad. I could haved sworn there was a post asking what should be used to substitute for the VVIS plate if it is removed. Sorry.
we still don't really know how much more would be gained by such surgery anyway, yet.
I think the dyno results on Marc's car are a pretty good indication. I gained over twenty peak hp and saw gains troughout the boost curve. Don't know if there were any losses at very low rpm because my boost comes on pretty fast. FI likes big plenums.
Sorry if I mucked up the thread with missinformation. Won't happen again.
Carry on.
Originally posted by sjs
More accurately, to someone knowledgeable in VVIS and similar systems. For example, I think Corky would be considered plenty experienced with forced induction, but not up to speed on modern variable intake design.
I consider VVIS to be a subset of intake design, but I guess I could be wroing.
Besides, we have long discussed the idea of pulling it out entirely and assumed it to be worth doing on most boosted cars. That’s no revelation, but it also isn’t the point.
My bad. I could haved sworn there was a post asking what should be used to substitute for the VVIS plate if it is removed. Sorry.
we still don't really know how much more would be gained by such surgery anyway, yet.
I think the dyno results on Marc's car are a pretty good indication. I gained over twenty peak hp and saw gains troughout the boost curve. Don't know if there were any losses at very low rpm because my boost comes on pretty fast. FI likes big plenums.
Sorry if I mucked up the thread with missinformation. Won't happen again.
Carry on.
David, don't go on sabatical again... I don't think sjs had any malicious intent.
At any rate, the rest of the NSX community is just now getting to the point you were at 2 years ago! Stick around and teach us a thing or three.
At any rate, the rest of the NSX community is just now getting to the point you were at 2 years ago! Stick around and teach us a thing or three.
yeah David Where's the avatar
Yes you should stick around
Yes you should stick around
I think the real meaning of this reaction David is that no one (including you from the posts and articles you have graciously written for 'Prime and NSXDriver) has shown how it works and why it does or does not for FI. We discussed this openly at Texas NSXPO, as CTSC plots did not have the first bump that BBSC plots did. It was conjectured that it was because of the lack of VVIS butterflies in the CTSC. Lots of talk, but no one has actually brought forward results. I realize many tuners like to keep some of their tricks close to the vest, but I would think that this one would have been discussed here in detail before. ICBW
Something that was also done a year or two ago was running the vacuum pot from the VVIS to it's own manifold source, when you do this the VVIS opens as you go into positive pressure.
Re: Re: Re: Been there, done that
David, the last thing any of us want is for you stop contributing, but that shouldn’t deter healthy debate.
As for your response to my comments:
I consider VVIS to be a subset of intake design, but I guess I could be wroing.
Sure, VVIS is a subset of modern intake design. I’m just not sure all turbo/SC system builders have been exposed to it. But this is a debate without a point so I’ll move on.
My bad. I could haved sworn there was a post asking what should be used to substitute for the VVIS plate if it is removed. Sorry.
Yes, someone did ask about what should be used to substitute for the VVIS plate, and you were simply addressing that question. I took the answer differently, so my bad on that. Sorry.
I think the dyno results on Marc's car are a pretty good indication.
My point here was that Mark’s results were achieved without removing the VVIS, so that means with an improved modification (such as Gerry just described) he can retain the significant low-end torque benefit of the system while still gaining the HP observed in his tests. But that still leaves the question of how much more might be gained by removing it completely. Enough to be worth giving up the torque? Perhaps, but that’s what we’d like to know.
Sorry if I mucked up the thread with missinformation. Won't happen again.
Carry on.
David, cut me some slack. I'm not some a-hole giving you crap, at least that wasn't my intent. A few others are finally committing the resources to get where you have been for a couple years, and the rest of us are grateful to everyone willing to share their knowledge.
David, the last thing any of us want is for you stop contributing, but that shouldn’t deter healthy debate.
As for your response to my comments:
I consider VVIS to be a subset of intake design, but I guess I could be wroing.
Sure, VVIS is a subset of modern intake design. I’m just not sure all turbo/SC system builders have been exposed to it. But this is a debate without a point so I’ll move on.
My bad. I could haved sworn there was a post asking what should be used to substitute for the VVIS plate if it is removed. Sorry.
Yes, someone did ask about what should be used to substitute for the VVIS plate, and you were simply addressing that question. I took the answer differently, so my bad on that. Sorry.
I think the dyno results on Marc's car are a pretty good indication.
My point here was that Mark’s results were achieved without removing the VVIS, so that means with an improved modification (such as Gerry just described) he can retain the significant low-end torque benefit of the system while still gaining the HP observed in his tests. But that still leaves the question of how much more might be gained by removing it completely. Enough to be worth giving up the torque? Perhaps, but that’s what we’d like to know.
Sorry if I mucked up the thread with missinformation. Won't happen again.
Carry on.
David, cut me some slack. I'm not some a-hole giving you crap, at least that wasn't my intent. A few others are finally committing the resources to get where you have been for a couple years, and the rest of us are grateful to everyone willing to share their knowledge.
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Re: Been there, done that
We make the VVIS replacement plate that David is using in this config. If anyone is in need of one, just give us a call.
Regards,
-- Chris
We make the VVIS replacement plate that David is using in this config. If anyone is in need of one, just give us a call.
Regards,
-- Chris
David said:
To anyone with experience with forced induction intake design, this would have been a pretty obvious decision. The stock intake is designed to exploit harmonics that only work in NA applications.
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ok my motor is now out and low comp build has begun i have a question has anyone milled out the inside of there intake not just the vvis. and if so how much did you mill did you completly remove all of the runners or just the devider it looks like there could be major inprovements made here.
Anyone else try this?
Armando
Armando
I presume that the VVIS system is using a vaccum actuated solenoid attached to a negative-vaccum driven actuator, right? Wrong? If so, you can use electronics to control the duty cycle of the solenoid based on RPM and/or manifold pressure.
If so, you can use electronics to control the duty cycle of the solenoid based on RPM and/or manifold pressure.
I looked in the FSM, and I see on page 11-119 information on the chamber volume control system. What I take from it is:
CVCS actuator is pull design, utilizing vacuum as the pull force. Default mechanical state (not pulled), controlled by actuator spring, is valve OPEN.
There is a solenoid (as I expected) called the CVCS solenoid connected directly to ECU.
a. It is ON below 4800 rpm.
b. It is OFF above 4800 rpm.
Manifold vacuum ---> solenoid [ vacuum in ] ---> [ ECU controlling solenoid duty cycle ] ---> solenoid [ vacuum out ] ---> CVCS actuator
Below 4800 rpm, ECU sets solenoid duty cycle to 100%, allowing full vacuum to pass through the solenoid air-path - which results in engine vacuum pulling the actuator rod, which closes the CVCS valves.
Above 4800 rpm, ECU sets solenoid duty cycle to 0%, allowing no vacuum to pass through the solenoid air-path - which prevents engine vacuum from reaching the actuator. Since default state is actuator rod extended the CVCS valves stay open.
This is why disconnecting the vacuum source to the actuator leaves the CVCS valves open - the ECU does exactly the same thing, but it uses a solenoid valve, controlled electronically, to do it. Honda has used the same system on various other VTEC engines.
The reason positive manifold pressure (boost) does NOT pin the CVCS actuator rod from moving is because positive pressure never makes it past the one-way check valve as shown in the diagram. Even if you could get it past the check-valve, it wouldn't get past the solenoid when closed @ 4800 rpm. I'm still a little unsure as to why positive manifold pressure also prevents the actuator arm from returning to default position after the solenoid air-path is closed past 4800 rpm. My only theory is that the positive pressure in front of the check-valve is preventing the actuator diaphragm from releasing the stored vacuum resulting in pressure equalization on both sides of the solenoid. But I could have sworn that solenoid is vented, based on the diagram.
So I'm sure you're asking: how do you keep the CVCS system with a forced induction setup?
First, a side-note:
On the FD3S we have 2 sets of oil injectors that inject oil into the rotor housings from an oil metering pump located on the front housing of the engine. This is done for internal seal lubrication and combustion cooling. These oil injectors work off of vacuum from the compressor INLET so that off-boost they still see normal engine vacuum and on-boost they see higher levels of vacuum due to the compressor pull. Either way, the capacity of oil injected into the engine is determined by vacuum and NEVER positive pressure.
Now the reason I mention this is because there is a similarity in that you have two systems which were never meant to see positive pressure in order to work properly. The way Mazda handled it with the oil metering was to place a vacuum source pre-compressor, right on the intake elbow.
In my opinion this is the proper solution to get the CVCS solenoid to work correctly. The source of it's vacuum should be moved to a point before charge compression. Tapping a small vacuum nipple into the intake piping before the compressor (TC or SC) would be a pretty easy solution here.
Another solution without moving to a pre-compressor source could be to tee between the solenoid and actuator a one-way check valve that vents to atmosphere but doesn't allow air to be pulled in from the atmosphere (vacuum state) which would allow the actuator rod to snap back even with positive pressure before the check valve.
A somewhat cheesier way might be to experiment with removing the check-valve and solenoid altogether which would allow vacuum (partial throttle, etc.) to still pull the actuator rod, but positive pressure (boost) would result in the actuator spring pulling it back to short/large intake runner mode. I say cheesy because this would just go right to high rpm mode the second you create manifold pressure (which you can do at 2000 rpm if you floor it - and the high rpm runner path isn't the best choice for 2krpm, FI or not).
I'm not a vacuum/charge-control expert by any means, but troubleshooting the over-complex FD3S sequential turbo system that is actuated primarily with a load of vacuum lines and solenoids has given me a lot of insight on how these types of systems work.
The way Honda is using solenoids here is totally basic, in fact, they're not even using duty cycles at all - just on and off. You guys have got it easy!
Typically this is what some us more savvy FD owners do with our vacuum/solenoid control system:
(clickable thumbnails)
From:
To:
CVCS actuator is pull design, utilizing vacuum as the pull force. Default mechanical state (not pulled), controlled by actuator spring, is valve OPEN.
There is a solenoid (as I expected) called the CVCS solenoid connected directly to ECU.
a. It is ON below 4800 rpm.
b. It is OFF above 4800 rpm.
Manifold vacuum ---> solenoid [ vacuum in ] ---> [ ECU controlling solenoid duty cycle ] ---> solenoid [ vacuum out ] ---> CVCS actuator
Below 4800 rpm, ECU sets solenoid duty cycle to 100%, allowing full vacuum to pass through the solenoid air-path - which results in engine vacuum pulling the actuator rod, which closes the CVCS valves.
Above 4800 rpm, ECU sets solenoid duty cycle to 0%, allowing no vacuum to pass through the solenoid air-path - which prevents engine vacuum from reaching the actuator. Since default state is actuator rod extended the CVCS valves stay open.
This is why disconnecting the vacuum source to the actuator leaves the CVCS valves open - the ECU does exactly the same thing, but it uses a solenoid valve, controlled electronically, to do it. Honda has used the same system on various other VTEC engines.
The reason positive manifold pressure (boost) does NOT pin the CVCS actuator rod from moving is because positive pressure never makes it past the one-way check valve as shown in the diagram. Even if you could get it past the check-valve, it wouldn't get past the solenoid when closed @ 4800 rpm. I'm still a little unsure as to why positive manifold pressure also prevents the actuator arm from returning to default position after the solenoid air-path is closed past 4800 rpm. My only theory is that the positive pressure in front of the check-valve is preventing the actuator diaphragm from releasing the stored vacuum resulting in pressure equalization on both sides of the solenoid. But I could have sworn that solenoid is vented, based on the diagram.
So I'm sure you're asking: how do you keep the CVCS system with a forced induction setup?
First, a side-note:
On the FD3S we have 2 sets of oil injectors that inject oil into the rotor housings from an oil metering pump located on the front housing of the engine. This is done for internal seal lubrication and combustion cooling. These oil injectors work off of vacuum from the compressor INLET so that off-boost they still see normal engine vacuum and on-boost they see higher levels of vacuum due to the compressor pull. Either way, the capacity of oil injected into the engine is determined by vacuum and NEVER positive pressure.
Now the reason I mention this is because there is a similarity in that you have two systems which were never meant to see positive pressure in order to work properly. The way Mazda handled it with the oil metering was to place a vacuum source pre-compressor, right on the intake elbow.
In my opinion this is the proper solution to get the CVCS solenoid to work correctly. The source of it's vacuum should be moved to a point before charge compression. Tapping a small vacuum nipple into the intake piping before the compressor (TC or SC) would be a pretty easy solution here.
Another solution without moving to a pre-compressor source could be to tee between the solenoid and actuator a one-way check valve that vents to atmosphere but doesn't allow air to be pulled in from the atmosphere (vacuum state) which would allow the actuator rod to snap back even with positive pressure before the check valve.
A somewhat cheesier way might be to experiment with removing the check-valve and solenoid altogether which would allow vacuum (partial throttle, etc.) to still pull the actuator rod, but positive pressure (boost) would result in the actuator spring pulling it back to short/large intake runner mode. I say cheesy because this would just go right to high rpm mode the second you create manifold pressure (which you can do at 2000 rpm if you floor it - and the high rpm runner path isn't the best choice for 2krpm, FI or not).
I'm not a vacuum/charge-control expert by any means, but troubleshooting the over-complex FD3S sequential turbo system that is actuated primarily with a load of vacuum lines and solenoids has given me a lot of insight on how these types of systems work.
The way Honda is using solenoids here is totally basic, in fact, they're not even using duty cycles at all - just on and off. You guys have got it easy!
Typically this is what some us more savvy FD owners do with our vacuum/solenoid control system:
(clickable thumbnails)
From:
To:
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Good stuff, but wouldn't the idea of tapping in ahead of the compressor give the wrong results? If you are ahead of the throttle plates you get no indication of manifold pressure/vacuum. In fact, conditions that give the greatest vacuum in the stock configuration will give none this way. Did I misunderstand your suggestion? Your thoughts of trapped vacuum seem like a good bet.
Your car has to idle right?
You will most definitely get vacuum there.
Pre-compressor, all you will see is vacuum, which is exactly what one wants in this situation.
You will most definitely get vacuum there.
Pre-compressor, all you will see is vacuum, which is exactly what one wants in this situation.
clayne said:Your car has to idle right?
You will most definitely get vacuum there.
Pre-compressor, all you will see is vacuum, which is exactly what one wants in this situation.
One of us is confused. It may just be that we are talking different physical configurations, but any time you tap in before the throttle plate you won't see vacuum as needed for this. Sure, you will see airflow, but not at a significant negative pressure level (vacuum). That's caused by being on the engine side of the throttle plate where it is trying to pull large volumes of air past a nearly closed throttle. Same air flow on either side, but vacuum reading only on the engine side.
That's corresct sjs, you will NOT see engine vacuum there (ahead of the throttle plates.) In fact, with a BBSC, that's exactly where the Bosch by-pass valve is located and even at engine idle speeds, the compressor is "blowing like hell" out this bypass valve. Conversely, you will have about 20" of vacuum just downstream of the throttle plate.
kpond,
The bypass valve you speak of is most likely located between the compressor side and the throttle body plates. What I referred to was BEFORE the compressor side (right after the air filter).
sjs,
I see where you are headed, and you are correct on that. What I was saying was wrong. But under throttle, you will see vacuum and only vacuum at that location (pre-compressor).
Hooking up a boost gauge to this source should be pretty indicative of what to expect.
The bypass valve you speak of is most likely located between the compressor side and the throttle body plates. What I referred to was BEFORE the compressor side (right after the air filter).
sjs,
I see where you are headed, and you are correct on that. What I was saying was wrong. But under throttle, you will see vacuum and only vacuum at that location (pre-compressor).
Hooking up a boost gauge to this source should be pretty indicative of what to expect.
But you will never see much vacuum, and it won't be meaningful. Or more accurately, if you see more than a very small amount then I think it is a sign that your intake is too restrictive, such as a too small or dirty filter, or circuitous plumbing.
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