NPP exhaust valves on my SW 3" pipe set

[mike100]

I liked the extra top end power on my recently purchased SW 3" Cat-back, but lets not even try to be diplomatic- it's pretty much loud enough to piss off your neighbors and give you a headache on a long trip.

So I got some C6-Z06 mufflers with the NPP exhaust flapper valves (vacuum actuated).
http://i29.photobucket.com/albums/c265/mschrameck/Cars/DSC02787_zpsdc20a86d.jpg
Note that the inside pipes are the loud, high flow straight thru section. This will be blocked during cruise conditions.

http://i29.photobucket.com/albums/c265/mschrameck/Cars/DSC02786_zpsa947e38e.jpg

Hacked them off to put them on my loud-*** SW mufflers.
http://i29.photobucket.com/albums/c265/mschrameck/Cars/DSC02788_zpsb91c87fd.jpg


Working out the fit- had to rotate them a touch to fit the vacuum can.
Also the diaphragm comes loose and you can reposition it so the vacuum nipple points in any direction.
http://i29.photobucket.com/albums/c265/mschrameck/Cars/DSC02789_zpsf1eec8be.jpg

http://i29.photobucket.com/albums/c265/mschrameck/Cars/DSC02798_zps2238a2a8.jpg

http://i29.photobucket.com/albums/c265/mschrameck/Cars/DSC02795_zps4888f5d6.jpg

[mike100]

http://i29.photobucket.com/albums/c265/mschrameck/Cars/DSC02790_zps67996caa.jpg

Got the staggered tip the same on both sides- sort of follows the fascia curve.
http://i29.photobucket.com/albums/c265/mschrameck/Cars/DSC02791_zps331fc03a.jpg

[mike100]

So I finally received the adjustable vacuum switch. When the vacuum controlled secondary throttle is activated on the LT5, so is my loud valve. I set it to 12" of vacuum (12 in Hg).

http://i29.photobucket.com/albums/c265/mschrameck/Cars/DSC02801_zpscc56e748.jpg~original

The switch powers a junkyard EGR vacuum solenoid. This couples the vacuum to the muffler valves. It either connects the vacuum to the valve, or vents the vacuum to the atmosphere thru the little foam filter on the 3rd port. It never has a vacuum leak on the source end. Perfect $8 solution (I should have pocketed it but I was feeling honest). The vacuum source is the nearby vacuum ball used for the a/c and air injection diverter valve. The 12v was easy too- I tapped into the under hood lamps which of course aren't even connected on my car anyhow.
http://i29.photobucket.com/albums/c265/mschrameck/Cars/DSC02802_zpsa57d5140.jpg~original

This is actually a second MAP sensor just to monitor the secondary throttle system. I 'T'-ed into it. Vacuum here means all 16 runners and injectors are working on the LT5 and it was a simple idea to switch the NPP valve off of this computer controlled load function.
http://i29.photobucket.com/albums/c265/mschrameck/Cars/DSC02803_zps80d692a8.jpg~original

Here it is idling- the loud section of the muffler is blocked off (left pipe). Will try to get a video on Saturday.
http://i29.photobucket.com/albums/c265/mschrameck/Cars/DSC02804_zps3f3c238c.jpg~original

[mike100]

Just in case you missed the picture of the SW muff. One pipe is straight-thru, the other actually muffles:
http://i29.photobucket.com/albums/c265/mschrameck/SW_muff_sm_zpsfe614c8c.jpg~original

[XfireZ51]

So whaddya think?

[mike100]

So whaddya think?

It's great! Bit of a treasure hunt to get the Z06 mufflers I found. I could leave it well enough alone, but I think I can get faster opening and closing if I run a 2nd vac solenoid and have a dedicated feed to each actuator. Bleed down would have twice the vent capacity.

I do rather like lugging the revs a tad and not droning (at all).

[Paul Workman]

Really interesting setup Mike!

I think I have the jist of what you've done, but pls allow me summarize what I think I understand, and then maybe you can clear up where I "lost your trail".:o

The adjustable vacuum switch receives vacuum from the "T" connection that also feeds vacuum to the MAP (under the ECM on a 1900 Z). At or below 12" Hg, the switch closes, activating the vacuum solenoid.

Normally, this solenoid connects plenum vacuum to the NPPs - keeping them closed. But, when plenum vacuum drops below 12" Hg, the vacuum solenoid receives its signal and "vents" the vacuum to the atmosphere (through the foam filter), thus relaxing the NPP diaphragms and thus opening the exhaust gates.

Now, if not already, is where I get a little:confused:...

You referenced a second MAP, and dedicated vacuum solenoids for each NPP valve. I get the reasoning for the dual system - decreasing bleed time - but I'm missing a link here...

It looks like the vacuum solenoid (pictured) would directly operate the NPPs. But, it is this additional MAP you mentioned, and the electric/vacuum circuitry at the NPP end that has me :icon_scra. I gather the system as it is now is a "work in progress", is it? By that, I mean the NPP end of the setup is yet to be upgraded for individual operation???

As you can see, Mike, I wandered off the path somewhere... :(

[-=Jeff=-]

Mike,

you needed the tips as well correct? mind if I ask how much you paid for the NPP mufflers?

I have seen the valves themselves on eBay for about $100 each for new ones

[GOLDCYLON]

Nice thread and a great solution. Dom did you do this electronically or via vacuum like Mike? GC

[XfireZ51]

Nice thread and a great solution. Dom did you do this electronically or via vacuum like Mike? GC

Mine are connected via what was the vacuum line for the canister and plugged into driver's side plenum port. The one that was previously used for the secondaries. No switch so the NPP valves open progressively like vacuum secondaries on a Quadrajet carb. Sounds a bit like it too. BBBWWWWAAAAAAAAAA! Pretty sure Pete, Al, and BobGs set ups are similar.
Pete has his valves grafted onto B+B tips, Bob and I use the Z06 tips.


Paul,

Were u working on another source for the valves? It is an Easter Egg hunt to find someone who'll cut the tips off and sell for a reasonable price.

[XfireZ51]

Mike,

I see you have mounted the valve on the inboard side of the muffler. The FBI valves are on the outboard side.

[-=Jeff=-]

Mike,

I see you have mounted the valve on the inboard side of the muffler. The FBI valves are on the outboard side.

He did it on the the straight through tube on the exhuast, I guess it really would not matter though, still gets the job done :)

[GOLDCYLON]

Mine are connected via what was the vacuum line for the canister and plugged into driver's side plenum port. The one that was previously used for the secondaries. No switch so the NPP valves open progressively like vacuum secondaries on a Quadrajet carb. Sounds a bit like it too. BBBWWWWAAAAAAAAAA! Pretty sure Pete, Al, and BobGs set ups are similar.
Pete has his valves grafted onto B+B tips, Bob and I use the Z06 tips.


Paul,

Were u working on another source for the valves? It is an Easter Egg hunt to find someone who'll cut the tips off and sell for a reasonable price.

Dom do you think these would make a difference on a corsa system ?

[GOLDCYLON]

Mike,

I see you have mounted the valve on the inboard side of the muffler. The FBI valves are on the outboard side.


its a left coast right coast thing... actually thats where his straight throughs are on the system. I think the Corsas are outboard like the FBIs setup as well.

[-=Jeff=-]

brand new 2.5"

http://www.ebay.com/itm/380606319348?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

http://www.ebay.com/itm/Stainless-Steel-Exhaust-Control-Valve-Set-Vacuum-Actuator-2-1-2-63mm-Pipe-/380722445361?pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr&hash=item58a4d37c31

[WARP TEN]

Dom do you think these would make a difference on a corsa system ?

The Corsa is straight through on both pipes so it wouldn't make any difference. If you put the valves on a Corsa you would simply restrict flow. Might lower sound intensity a bit. As I understand it, on the Z06 and the SW one side is more muffled than the other, although I could be wrong. -Bob

[mike100]

Mike,

you needed the tips as well correct? mind if I ask how much you paid for the NPP mufflers?

I have seen the valves themselves on eBay for about $100 each for new ones

I got the mufflers for $300. This is a good price for Z06 mufflers even though it was more than I wanted to pay. It did fit, solved my problem, and looks like it is a vette part.

Interestingly, when I was at the local muffler place, the guy gave me a 2.25" exhaust flapper from a twin turbo BMW 335 (made by Boysen). They use one per car and they are full open with half the vacuum signal (only 5" vac vs. 10" on the C6 version). This may be a source of decent valves if you can score take-off 335 mufflers.
http://i29.photobucket.com/albums/c265/mschrameck/Cars/DSC02792_zpsec81db6e.jpg

http://i29.photobucket.com/albums/c265/mschrameck/Cars/DSC02793_zpsc55eb812.jpg

[mike100]

its a left coast right coast thing... actually thats where his straight throughs are on the system. I think the Corsas are outboard like the FBIs setup as well.

Yeah, the SW muffs have the inlet on the inboard part of the muffler.

[mike100]

Really interesting setup Mike!

I think I have the jist of what you've done, but pls allow me summarize what I think I understand, and then maybe you can clear up where I "lost your trail".:o

The adjustable vacuum switch receives vacuum from the "T" connection that also feeds vacuum to the MAP (under the ECM on a 1900 Z). At or below 12" Hg, the switch closes, activating the vacuum solenoid.

Normally, this solenoid connects plenum vacuum to the NPPs - keeping them closed. But, when plenum vacuum drops below 12" Hg, the vacuum solenoid receives its signal and "vents" the vacuum to the atmosphere (through the foam filter), thus relaxing the NPP diaphragms and thus opening the exhaust gates.

Now, if not already, is where I get a little:confused:...

You referenced a second MAP, and dedicated vacuum solenoids for each NPP valve. I get the reasoning for the dual system - decreasing bleed time - but I'm missing a link here...

It looks like the vacuum solenoid (pictured) would directly operate the NPPs. But, it is this additional MAP you mentioned, and the electric/vacuum circuitry at the NPP end that has me :icon_scra. I gather the system as it is now is a "work in progress", is it? By that, I mean the NPP end of the setup is yet to be upgraded for individual operation???

As you can see, Mike, I wandered off the path somewhere... :(

Ok, there is some reference to the 2nd MAP sensor- that was meant for another non-ZR-1 forum where people aren't aware of the function of our vacuum secondaries (for those of us who still run them anyways:p).

To clarify, manifold vacuum closes the muffler flap- they are open at rest.

-To have run the valve straight from the secondary pump would have had the logic 180 reversed- plus they draw too much air and would have messed up the function probably.

So what I did was use the normally open contacts on that adjustable vacuum switch that triggers another vacuum source (through a GM EGR solenoid) when the secondary activates. What it actually does is release the actuator vacuum to the vent(when u step on it) as the solenoid is allowing vacuum through in the off condition (during cruise conditions). It is sort of reverse logic.

The vacuum source is NOT plenum vacuum. it is an is a check-valve isolated source (the vacuum ball under the d/s headlamp.

[XfireZ51]

The system here in FBI land is using the DynoMax Utlraflow. These are straight thru w either tube. I didn't ask about Mike's positioning because of performance.
Rather it was for fit. Perhaps the SW muffs allow positioning on the inside. The DynoMax really have a better fit with the valve on the outside.
Al or Pete could offer better insight on this.

[-=Jeff=-]

The system here in FBI land is using the DynoMax Utlraflow. These are straight thru w either tube. I didn't ask about Mike's positioning because of performance.
Rather it was for fit. Perhaps the SW muffs allow positioning on the inside. The DynoMax really have a better fit with the valve on the outside.
Al or Pete could offer better insight on this.

Yeah I think the SW might be side specif due to the inlet maybe? I like how he did it, the Valves are tucked up out of the way..

Either way works...

GC,

I see no reason to add these to Corsa unless you are swapping out the Corsa mufflers

(I am probably one of the only FBI guys running Corsa's) and one of the last who has not ported anything either

[XfireZ51]

Yes, remember the valve effectively eliminates the need for a resonator. I'm running just an SW Xpipe(unbaffled) with the muff and valves. Reduces weight, cost and restriction.

[ZZZZZR1]

Question

Could you add the npp and the mild to wild switch?

With mild to wild you can press a button to open and close
the exhaust

Possible?

Thanks

David

[GOLDCYLON]

Yeah I think the SW might be side specif due to the inlet maybe? I like how he did it, the Valves are tucked up out of the way..

Either way works...

GC,

I see no reason to add these to Corsa unless you are swapping out the Corsa mufflers

(I am probably one of the only FBI guys running Corsa's) and one of the last who has not ported anything either


Ok Im still running em but have ported everything.

[-=Jeff=-]

Ok Im still running em but have ported everything. Are not the Corsas only one strraight threw I remember a tennis ball demo over at corvette forum. The other pipe is stricky decorative?

Pretty much yes decorative as far as I know.

if you had a pair with dual outputs then the flapper would come into play

[-=Jeff=-]

Question

Could you add the npp and the mild to wild switch?

With mild to wild you can press a button to open and close
the exhaust

Possible?

Thanks

David

it all depends on how it is set-up on the C6 vs our modded set-up.. if done the same way then it is easy.. if it is not it may take a small bit of figuring it out to get it working

[BigJohn]

Have you ever heard Callaway Megaphones!!!

:cheers:

[mike100]

Ok Im still running em but have ported everything. Are not the Corsas only one strraight threw I remember a tennis ball demo over at corvette forum. The other pipe is stricky decorative?

You are correct. The single outlet acoustical trick along with Corsa's cleverly designed resonator reduces/eliminates drone, but they are still loud from outside the car, decibel-wise.

I remember when I traded a B&B for the Corsa- much more driveable, but still pretty loud from outside the car. Then I went stock for awhile (sans resonator), but missed the extra power and went with the group buy on the SW stuff (but back to obnoxiously loud). This way with the valves is basically having my cake and eating it too.

[GOLDCYLON]

Pretty much yes decorative as far as I know.

if you had a pair with dual outputs then the flapper would come into play


I remember somebody cutting one of these open the other side is a backpressure plug but it certainly does not flow like the straight through

[Mystic ZR-1]

Have you ever heard Callaway Megaphones!!!

:cheers:

Yep!

[GOLDCYLON]

Have you ever heard Callaway Megaphones!!!

:cheers:


What? I cant hear you and im bleeding from my ears.

[WARP TEN]

Question

Could you add the npp and the mild to wild switch? With mild to wild you can press a button to open and close the exhaust Possible? Thanks
David

Hi David--That's what I have with the electric cutouts. Stock system for quiet (well, a little louder than stock with headers and no cats) but then I can open up the cutouts all the way to a complete straight through system. Very loud. What I have been doing is running with the cutouts cracked just a little bit to add some rumble. Quite livable. But it is fun when they are wide open.:dancing -Bob

[ZZZZZR1]

Hi David--That's what I have with the electric cutouts. Stock system for quiet (well, a little louder than stock with headers and no cats) but then I can open up the cutouts all the way to a complete straight through system. Very loud. What I have been doing is running with the cutouts cracked just a little bit to add some rumble. Quite livable. But it is fun when they are wide open.:dancing -Bob

Bob

You have Corsa and electric cut outs too??

Ohhhhhhh. Details please!!!!

Love these modifications!

Cheers

David

[Paul Workman]

Ok, there is some reference to the 2nd MAP sensor- that was meant for another non-ZR-1 forum where people aren't aware of the function of our vacuum secondaries (for those of us who still run them anyways:p).

To clarify, manifold vacuum closes the muffler flap- they are open at rest.

-To have run the valve straight from the secondary pump would have had the logic 180 reversed- plus they draw too much air and would have messed up the function probably.

So what I did was use the normally open contacts on that adjustable vacuum switch that triggers another vacuum source (through a GM EGR solenoid) when the secondary activates. What it actually does is release the actuator vacuum to the vent(when u step on it) as the solenoid is allowing vacuum through in the off condition (during cruise conditions). It is sort of reverse logic.

The vacuum source is NOT plenum vacuum. it is an is a check-valve isolated source (the vacuum ball under the d/s headlamp.

OK, I got a clear picture now.

Your approach is interesting, and I suspect has very "digital" (read: either ON or OFF!) characteristic, compared to the direct vacuum line from the plenum to the NPPs (i.e, the FBI approach).

Simple and elegant vs. complex and wonderful?

I don't have a feeling either way, far as which is a better solution. From a simplicity view, the FBI approach is as simple as it gets. However, I think your method has potential to sharpen the NPP operation considerably - especially if dual, electrically triggered solenoids were used; one each for each NPP were to be employed.

Yours is an interesting approach, "fer sher". Thanks for sharing!!:)

[Paul Workman]

Bob

You have Corsa and electric cut outs too??

Ohhhhhhh. Details please!!!!

Love these modifications!

Cheers

David

Bob posted a picture of his electrically controlled cutouts a while back - located in place of the elbows behind the differential. The open gates open straight back, and when closed the cutout valves angled outlet point in the direction of the port/starboard mufflers; the only way to go with the single outlet Corsa muffs.

[Paul Workman]

brand new 2.5"

http://www.ebay.com/itm/380606319348?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

http://www.ebay.com/itm/Stainless-Steel-Exhaust-Control-Valve-Set-Vacuum-Actuator-2-1-2-63mm-Pipe-/380722445361?pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr&hash=item58a4d37c31

AH! Thanks very much for the links, =Jeff=!

Dom: As you know my situation was to find a replacement for the one NPP actuator I have with a perforated diaphragm. I found an actuator that might in fact work quite well, in the form of an exhaust heat riser gate valve. But, the gate itself is only about 1.5" in diameter and would be restrictive. So, one would require some bracket fabricating to fit the actuator to the bigger NPP gate.:(

If Jeff's source eliminates all the fussing to convert it, then I'm all for it! I'll have to check the ID of the NPPs I have, but I suspect the 2.5" valves Jeff located are the correct size (or close enough, especially on a dual outlet 17228 Dynamax muff!)

[WARP TEN]

Bob You have Corsa and electric cut outs too?? Ohhhhhhh. Details please!!!! Love these modifications! Cheers
David

Sorry to disappoint you Dave but I ditched the Corsas recently after 15 years on 2 different Zs. In my old age I am just tired of the constant noise and my wife thought they were too loud (she always said she could hear me coming about 3 blocks away!). I am back to my stock '95 system (Marc still had it at his shop from the swap last year) plus the QTP cutouts. As I noted in an earlier post, the Corsas are straight through on both pipes of the mufflers so cutouts wouldn't add anything there. The stock setup gives me relative quiet when I want it (slightly louder than pure stock as I have headers and no cats). The cutouts provide a full straight through system for the track or just for general intimidation and grins. I am currently running them cracked open just slightly for a little extra rumble. --Bob

[Pete]

Sorry to disappoint you Dave but I ditched the Corsas recently after 15 years on 2 different Zs. In my old age I am just tired of the constant noise and my wife thought they were too loud (she always said she could hear me coming about 3 blocks away!). I am back to my stock '95 system (Marc still had it at his shop from the swap last year) plus the QTP cutouts. As I noted in an earlier post, the Corsas are straight through on both pipes of the mufflers so cutouts wouldn't add anything there. The stock setup gives me relative quiet when I want it (slightly louder than pure stock as I have headers and no cats). The cutouts provide a full straight through system for the track or just for general intimidation and grins. I am currently running them cracked open just slightly for a little extra rumble. --Bob

Bob,as I remember Corsa has one tip open on the mufflers other is a dummy tip, this is why one tip is cleaner then the other.

Trying to push 7500RPM 550hp thru a single 2 1/2" pipe hmmm

Pete

[WARP TEN]

Bob,as I remember Corsa has one tip open on the mufflers other is a dummy tip, this is why one tip is cleaner then the other.

Trying to push 7500RPM 550hp thru a single 2 1/2" pipe hmmm

Pete

You may be right about the Corsa mufflers although I thought both pipes flowed exhaust. I do know that the stock C4 Corvette mufflers are like that, however, as the rear two thirds of the stock muffler is a closed section called a helmholz resonator. That's why one pipe is essentially a dummy. The helmholz resonator has a pipe going into it but no exit, so just sound waves go in. Its purpose is to cancel out the sound waves for one of the two resonance frequencies of our engines (I think the one at 1,800 rpm while the center resonator handles the resonance at 3,400 rpm. Or the vice versa). It performs a similar function to that of Corsa's "Reflective Sound Cancellation" approach which has the resonators located around the outside of an otherwise straight through pipe. --Bob

[mike100]

OK, I got a clear picture now.

Your approach is interesting, and I suspect has very "digital" (read: either ON or OFF!) characteristic, compared to the direct vacuum line from the plenum to the NPPs (i.e, the FBI approach).



Believe me, I would have liked to have just run from plenum vacuum, (I tried it), but there is rarely a flat stretch of road where I live and the uphill sections raise the engine load and cause the manifold vacuum to drop down enough to let the flapper start to crack open. It doesn't have to open very far before the resonance starts in.

My way requires both a (programmable) minimum rpm and throttle position condition. Surprisingly, it isn't as 'digital' as I would like it since my vacuum hose diameter being restrictive, causes a pretty slow opening and closing. As time permits I will run a second line and fiddle with the vacuum switch setting. I might even tweak the secondary activation curve in the lower revs near the resonance point around 1800-2000 rpm.

It was a fun modification, especially since I have an aversion to all the extra attention loud pipes get you.

[mike100]

The one thing I completely forgot about was that once the secondary is activated, it will stay on until less than 5% throttle position occurs. You have to let off the gas all the way briefly to get it to set back to quiet.

Another less complicated method might be to use the vacuum switch to just trigger on plenum pressures x amount of KPa near atmospheric or full throttle-high load. hmmm. thanks for the ideas...

[WARP TEN]

Believe me, I would have liked to have just run from plenum vacuum, (I tried it), but there is rarely a flat stretch of road where I live and the uphill sections raise the engine load and cause the manifold vacuum to drop down enough to let the flapper start to crack open. It doesn't have to open very far before the resonance starts in.

My way requires both a (programmable) minimum rpm and throttle position condition. Surprisingly, it isn't as 'digital' as I would like it since my vacuum hose diameter being restrictive, causes a pretty slow opening and closing. As time permits I will run a second line and fiddle with the vacuum switch setting. I might even tweak the secondary activation curve in the lower revs near the resonance point around 1800-2000 rpm.

It was a fun modification, especially since I have an aversion to all the extra attention loud pipes get you.

This is why I like the electric cutouts--you can adjust them whenever you want. I run them closed around town for a quiet stock sound, or cracked slightly open for some extra rumble. For the track--or just for grins--wide open. --Bob

[HAWAIIZR-1]

Sorry, I'm a bit late...........but FRIGGIN SWEET!! Thanks for sharing.

[Paul Workman]

The one thing I completely forgot about was that once the secondary is activated, it will stay on until less than 5% throttle position occurs. You have to let off the gas all the way briefly to get it to set back to quiet.

Another less complicated method might be to use the vacuum switch to just trigger on plenum pressures x amount of KPa near atmospheric or full throttle-high load. hmmm. thanks for the ideas...

Intriguing situation...

Well, having thought about your circumstances a little - specifically the hill/mountain factor (almost foreign to us FBI and other flatlanders) - there are perhaps a couple solutions: Go to a manually controlled, electrically switched cutouts (as Bob suggested) or control the vacuum solenoid with a sensor sampling and triggering on the TPS voltage perhaps???

The manual approach is, well, manual! (But, NOT spontaneous by any stretch, which is the main purpose of NOT going that route.).

I like the TPS voltage approach because the "on or off" aspect depends on throttle position only, and the spontaneity, of course. The threshold could theoretically be adjusted to trigger at any desired amount - even on the fly, if that was desirable too (several interesting options - discussed further down).

To address your concerns for lag and latent "on" mode (until the throttle dips under 5%), it might be addressed in three parts:


locating your EGR type vacuum solenoid(s) at or near the NPP valves, and
install a vacuum ball reservoir also close by the NPPs
triggering electrically from actual throttle position instead of ECM secondary control.

Having the solenoid close to the NPPs localizes the access to atmosphere, and further reduction in vacuum bleed off in the NPPs could be cut in half again by twin EGR type solenoids; one for each NPP, if even necessary.

Vacuum closing the NPPs would come from the vacuum ball nearby when the vacuum solenoids* is/are switched "off".

*Keys to the system are 1) a sensor/switch that reacts to perhaps the specific TPS voltage without interfering with its intended purpose (such as perhaps a high input impedance op amp circuit set to trigger at a predetermined voltage close to the WOT value), and 2) the vacuum solenoid needs to isolate the vacuum side of the switch when "ON" so as not to bleed air into the vacuum ball reservoir when the NPPs are switched open.

In the end, hypothetically the system would spontaneously react very quickly ON and OFF, according to throttle demand. And too, the system could be turned off completely with a switch, so as to avoid nuisance activation, OR locked ON too, for that matter.

In the end, this could also quicken the response to the vacuum only (FBI) setup, IF desired...IF.

The current vacuum system would change (the sound) from a mmmmWAAAAAH and back to more of a mmmmBAAAAH and equally/nearly as quick back to "mmmm" sort of thing!;)

Food for thought...

[mike100]

...
To address your concerns for lag and latent "on" mode (until the throttle dips under 5%), it might be addressed in three parts:


locating your EGR type vacuum solenoid(s) at or near the NPP valves, and
install a vacuum ball reservoir also close by the NPPs
triggering electrically from actual throttle position instead of ECM secondary control.



I like those ideas. Next trip to the wrecking yard and I may come home with another GM vacuum ball and another EGR solenoid. A high impedance TPS monitor circuit should work, as would going low-tech with a micro-switch just like my old nitrous system used to employ. It isn't too bad on the secondary though, just more instant activation would probably be a good first adjustment.

[Paul Workman]

I like those ideas. Next trip to the wrecking yard and I may come home with another GM vacuum ball and another EGR solenoid. A high impedance TPS monitor circuit should work, as would going low-tech with a micro-switch just like my old nitrous system used to employ. It isn't too bad on the secondary though, just more instant activation would probably be a good first adjustment.

I get the sense that you're getting very close to something good here, short of transplanting the entire NPP electronics and hardware to this app.

Bouncing this back and forth, for the sake of discussion, I completely glossed over you mentioning moving the vacuum switch to the plenum. That might work w/o designing a TPS voltage sensor/switch.

Now, the one thing that is NOT a problem with the electrical/manual cutouts or the relatively slower to react FBI system, i.e., the plenum activated NPPs, is rapid oscillation between ON and OFF or "chattering". This problem would depend largely on the sensitivity of the particular vacuum sensor/switch, primarily at the critical moment vacuum level crosses the trigger value. (I wouldn't want to unnecessarily "fix" a problem that never existed, but worth keeping in mind it could happen, and a fix could be applied if needed.)