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Electronic Bi-Modal Valves

stooge

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I was only responding to a member asking about bimodal valves for DPE mufflers...

i was only responding about increasing the volume by adding valves to non bimodal style mufflers.
i thought the question being asked was about more volume not less but it seems that the question must have been about making the v6 quiet.

i can totally see that blocking a pipe on some mufflers could lower the volume because there would be less points of noise like having 4 speakers and turning 2 off
i cant see how adding a valve to a muffler that does not have the straight through pipe could increase the volume by blocking an outlet.
 

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Bimodal exhaust is simple a plumbing method to circumvent the principles of exhaust noise laws. In essence it largely bypasses the rear muffle via the internal straight through pipework.

Conceptually, it isn’t very different to detecting a pollution test routine via wheel sensors and switching on exhaust pollution systems to reduce the bad gasses and power levels along with it.

In a bimodal system, the valve is controlled via the ECU which places some li it’s of when it’s allowed to be open in the hope of remaining legal… So one could expect that making your own controller and bypassing the ECU logic so it can be turned on at will, when normally it’s not allowed to be on, would be a noise pollution defeat device and thus illegal… But who cares, I love the diy bimodal controllers :p

as to mods, the truth as I see it is that unless the rear muffler has an internal straight through pipe that can be “opened” to release the noise, then welding such flaps on a muffler not designed for it seems a bit backwards. By that I mean spending $1000’s for a new free flowing exhaust and rear muffler that makes noise and then trying to choke the life out of it by closing a valve on one outlet to quieten it down is backwards. If one wants a quieter exhaust, don’t upgrade….

If only there were aftermarket exhausts with well designed rear bimodal mufflers that produce a better throatier V8 sound that is quiet when closed and more mean V8 deep throat when open, that would be the go (my aural preference - don’t like tinny sound). But to take a muffler not designed for two modes of operation and weld a bimodal valve on it is just wasting more $ to cover the waisted $ spent on the aftermarket exhaust one seems to not like the sound of…

Doing such is home hacking 101 and almost certainly not going to be optimal. Can home hacks work, yes, sometimes we’ll but it‘s conceptually backwards. Well I think so anyway.

@RevNev, got any pictures of the internal changes on your modded muffler and any sound bites with valve open and closed? I’m curious…
 
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RevNev

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my original response to another member asking about welding valves into a non bimodal muffler looking to increase the volume was...
You originally responded to this Stooge

Has anyone here opened up a DPE muffler? I was going have a set of valves welded in. But would like to see what the internals are like beforehand.

Your response was
if they are not designed for bimodal they will not have a straight through pipe and adding a valve to the tip will have little effect.

A DPE muffler is a Defillipo sports muffler isn't it, not a stock Holden non-bimodal? I'd assume given that Defillipo mufflers aren't quiet and tend to be on the loud and droney side, the idea of adding a valve in this instance in to quieten an already loudish and notey exhaust.

The next response was this
haven't opened up a DPE muffler, but I have vacuum bimodals on my Maloo's DPE exhaust.
If you want to experiment, get a couple of people to help.
Get them to cover one tip on each side with the sole of their shoes.

We're talking about adding a valve to DPE mufflers, nothing to do with Holden bimodals on a V6 and your response was to argue the toss with Imoengnr who'd already done it, bit disrespectful don't you think given that you haven't obviously conducted the same physical test?

Whilst you're arguing an unfounded ideology contradicting Imoengnr's experience valving DPE's, I responded with this
It does if you do it right. I cut my bimodals open and converted them to a centre chambered dual outlet Lukey style perforated tube fibreglass packed mufflers. The inlet is 2.25" and the outlets are twin 2" and with the valve closed exiting through one 2" pipe, it's a lot quieter and sounds almost stock inside the car. With the valves open, it's sound like a typical V8 aftermarket (sports) exhaust.

Valving a bimodal adaptable muffler I've likewise confirmed does result in two modes of loudness, you're still arguing the toss on a perceived ideology that you've never personally conducted to have an informed opinion.

Are we clear yet Stooge, or do want to continue arguing a topic you won't win?
 

RevNev

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I was only responding to a member asking about bimodal valves for DPE mufflers...
Mine are always open, except when:
Cold starts in the garage.
Driving through a breath test station.
When pulled up by the plods.

I wired an override switch in the EDI system to keep them open on the Maloo.

Bimodals are always open on the Magnum...
That's how I use my modified stock bimodals and to save going into Mylink to switch them over to quiet mode, I added the HSV mode dial for simplicity. Otherwise mine are open and the car's notey and loudish at idle and low speed as you'd expect a performance V8 should be.

20210904_172631.jpg
 

Skylarking

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or do want to continue arguing a topic you won't win?
Is it really a matter of winning? People can have differing views and both view can have merit.

As yet, I’ve only seen a bimodal system by vehicle manufacturers that works to make the exhaust quiet in the default normally closed state… Can it be designed normally open and noisey, yes, but it’s not designed that way probably for compliance reasons…

Rather than win/loose, I‘m more interested in what you have done inside your rear muffler to get it to work with bimodal valve :cool:

Maybe it’s just COVID and people getting hot under the collar and it becomes win/loose… but both you guys are in non locked down states so that can’t be it :p:p:p:p
 

stooge

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You originally responded to this Stooge



Your response was


A DPE muffler is a Defillipo sports muffler isn't it, not a stock Holden non-bimodal? I'd assume given that Defillipo mufflers aren't quiet and tend to be on the loud and droney side, the idea of adding a valve in this instance in to quieten an already loudish and notey exhaust.

The next response was this


We're talking about adding a valve to DPE mufflers, nothing to do with Holden bimodals on a V6 and your response was to argue the toss with Imoengnr who'd already done it, bit disrespectful don't you think given that you haven't obviously conducted the same physical test?

Whilst you're arguing an unfounded ideology contradicting Imoengnr's experience valving DPE's, I responded with this


Valving a bimodal adaptable muffler I've likewise confirmed does result in two modes of loudness, you're still arguing the toss on a perceived ideology that you've never personally conducted to have an informed opinion.

Are we clear yet Stooge, or do want to continue arguing a topic you won't win?


please show me who asked about making anything quiet?

i have said to you multiple times that adding a valve to a non bimodal muffler will not increase the volume and you have yet to show a single instance where adding a valve to a non bimodal muffler has increased its volume and i am not talking about modifying the internals of the muffler, just welding a valve on.

the problem is that you "assumed" my comment was about making the muffler quiet and you talked a lot of bullshit based on your own delusions and assumptions, i never said anything about making it quiet.
people are asking about how to make the exhaust louder and you keep banging on about how to make it quiet lol

you will never win this argument because you started it with the wrong assumption, the simple fact is you got it wrong from the start.

i will gladly wait for you to conduct the test showing that adding the valve to a non bimodal muffler will increase its volume.
 
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stooge

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Maybe it’s just COVID and people getting hot under the collar and it becomes win/loose… but both you guys are in non locked down states so that can’t be it :p:p:p:p

yeah no lockdowns here but i am just having fun with him. :p
 

RevNev

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If only there were aftermarket exhausts with well designed rear bimodal mufflers that produce a better throatier V8 sound that is quiet when closed and more mean V8 deep throat when open, that would be the go (my aural preference - don’t like tinny sound).
As I mentioned previously in the thread, I've built and modified exhausts since 1978 as a passion that's still active today. Despite the bimodal being louder and sounding more like a V8 should sound, the note in my ears is tinny, raspy and not good enough for me to like and retain. From experience, you need big rear mufflers on any car that are perforated tube fibreglass packed to get the smooth deep note with the minimum of drone and stock bimodal can's are a good size. Starting from scratch, I'd probably roll up a can 8" in diameter 14" long. Most aftermarket exhausts I think aren't using big enough rear muffler cans. Noise level I adjust in the midpipe and I've found with an X or H pipe, the VE/VF 2.5" exhausts need only two hot dog like resonators in the midpipe.

I didn't reinvent the wheel with my bimodal modification and simply used the old open chamber Lukey design. Lukey mufflers in the day produced the best notes and over the years, I've cut many open to discover why they sound the best. Here's the bimodal and I'll explain what I did to mine.


I left the inlet side of the muffler stock, it's 2.25" perforated tube with fibreglass packing in the first chamber. The straight (unperforated) pipe I cut out of the muffler and replaced it with twin 2" perforated tube. The centre chamber I left fully open to act as a Helmholtz resonator and open collector for the dual outlets and the outlet chamber I packed with fibreglass. It's exactly the same design as the original Lukey single inlet dual outlet mufflers we can't buy anymore and sounds just as good, super smooth and deep.

Twin 2" flows the equivalent of a 2 5/8" single pipe, so a twin 2" outlet is ample and flows more than a 2.5" single and with the valves open, the muffler functions like a 2.5" straight through. With the valves closed adds restriction maximising the Helmholtz effect in the centre chamber and stepping down to a 2" outlet, reduces noise quite considerably. It's not as quiet as a stock bimodal with the valves closed but quiet enough to be perceived stock for a V8. Sounds pretty much stock inside the car with no drone.

Normally I wouldn't bother with bimodals and I'd configure the exhaust to optimally function and sound good permanently that's not overly loud. I played around with the bimodals because they're already an OEM fitment and configuring a V8 bimodal is an exercise I had done before. I've done several BMW's however their bimodals are mostly transverse mufflers entirely different to the Holden setup with loud and raspy 6 cylinder turbo notes to improve and control, a different ball game to the trusty V8!

This would be worth a try starting from scratch using full length perforated tubes with fibreglass packing with an external bypass at the rear of the muffler. The valved side is 2.5" straight through and the bypass "quite mode" is 1.75" straight through. You could incorporate a Helmholtz chamber on the quiet side only if the muffler body is big enough.

bimodal 3.jpg


20210904_201948.jpg
 
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RevNev

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please show me who asked about making anything quiet?
Stooge are you saying that lmoengnr is claiming to have added valves to DPE non-bimodals to make them louder? I assume that he added valves to quieten the DPE's down and that's what I'm responding to. Of course adding valves to a stock muffler won't make them louder or increase flow, it's a no brainer that I'm sure most would have the intelligence to work out for themselves. As far as making a stock muffler louder, requires you to chop it up and reconfigure the internals or fit a different less restrictive muffler.

Show me where I've recommended fitting valves to stock non-bimodals to increase flow and noise. Post that statement from me and we'll continue the discussion.

@ lmoengnr, did you fit valves to your DPE's to make them louder or to quiet them?
 
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