This is a valved exhaust review of a muffler I bought from Aliexpress for the big turbo 1.8T project. The project Octavia RS has had a loud exhaust since I started working on it. I thought a valved exhaust could help, and it did, but there are some essential things to consider before buying one for your car.

Valved Exhaust Review – Background

The exhaust on the Octavia was straight-through, turbo back, with a single rear “jap-style” rear silencer. The rear silencer/muffler was made of stainless steel, it had a 70mm inlet diameter (same as the rest of the system) going to a 100mm exhaust tip. The body diameter of the muffler was 130mm. The length was around 40cm.

Valved Exhaust Review – The Problems

The issue with this setup was twofold.

There was a massive drone above around 2500-3000RPM with a frequency of around 120Hz. This made driving at motorway speeds unpleasant, to the point where it was hard to speak to passengers.

The other issue was the volume in general. Even at idle, the burble from the exhaust would reach the cabin. At larger throttle openings it was very loud in the car, I expect the 120Hz frequency was getting amplified. What it was like from outside I don’t know.

Valved Exhaust Review – Why Change Exhaust?

I wanted to get rid of the drone and I wanted to exhaust to only be as loud as it needed to be for power it was making. To put it another way, I wanted the exhaust to be as quiet as possible, as long as it wasn’t causing a restriction.

I toyed with the idea of putting an insert in the exit of the exhaust. They are cheap and easy to install. The thing that stopped me from going with this solution was the restriction to gas flow. Who knows when you want/need to open up the throttle and I didn’t fancy having to pull to the side of the road to remove the exhaust insert before I gave it some gas. Just not practical.

Another option was to fit a bigger silencer in the exhaust system somewhere and leave the rear silencer as is. I might still do that, but I wasn’t 100% happy with the exit of the exhaust and wanted something that looked a bit more OEM+.

Which is why I went with a valved exhaust.

AliExpress

From what I could see there wasn’t a valved exhaust available off-the-shelf for the Octavia RS 1.8T and the exhausts that were/are available used a smaller bore than the 70mm on the car. Couple this with the prices, 400 Euro plus, I turned to Aliexpress for something universal.

AliExpress has loads of options available with varying prices but from what I could see, all the valved silencers/valved mufflers were basically the same size (internal volume), the differences being pipe diameters, the type of valve actuator (if they came with an actuator at all) and the size of the hole that leads into the silencer (the hole where the gases go when the valve is closed).

I had seen videos on YouTube where the main pipe in the silencer had holes all-round the inside of the pipe but most just had the one hole.

Seeing as they all seemed relatively similar, I chose the cheapest, without an actuator (and hoped there would be multiple holes inside instead of just one. Hoped in vain as it turned out).

This is the muffler I bought.

A few words about actuators

All the actuators for these valvetronic/valved mufflers are the same (from what I could see), they either fully opened the exhaust valve or fully closed it. But I wanted the amount the valve could open to be variable. I had a plan to achieve this. More later in this article.

Quality of the valved muffler I bought.

On arrival the quality seemed excellent. Fantastic welds and heavy. It was a little smaller than I expected but this was my own fault. The dimensions of the exhaust matched the description.

Installing the Muffler

I’d done a ton of measuring before ordering and it looked like it would be tight but doable. I thought of fitting it myself but decided to go with a pro. The pro being Exatmiseis.eu in Thessaloniki.

All the issues I imagined, turned out to be real issues.

The heat shield needed modifying and the tail on the muffler had to be angled up quite aggressively to get close to the bumper exit. It took a lot longer than I and the installer thought it would, but it went on fine. The original plan was to use slip joints and clips but the angles on the pipes weren’t right, so everything was welded, the muffler to the system and the tip to the muffler.

Did It Do What I Wanted?

In short. Yes.

But it’s still not as quiet as I would like. I want it almost silent at idle and it’s pretty far from that.

However, from inside the car the exhaust noise has near enough completely gone. No more drone anywhere. Motorways speeds are quiet (inside the car) and generally, noise levels are much less than before. Except at bigger throttle openings when the valve opens completely. But the difference at full throttle now is the lack of resonance, it’s almost completely gone. In short, a win everywhere just not as quiet as I want.

Who Is This Valved Muffler For?

This is a difficult question to answer, it depends on what you want.

Loud Exhaust Now – Going For Stock Sound Levels

If you have a loud exhaust now and you want stock levels of volume, I’d say no, this isn’t for you. The silencer is quite small so there is only so much it can do. If you want stock sound levels, I think you need to fit a muffler that has an internal volume similar to the stock muffler/silencer. Or a muffler than is much bigger than what you have now.

Loud Exhaust Now – Going For Something A Bit Quieter

If you have a performance exhaust now and you want to tone it down a bit this muffler will probably do the job, assuming this valved muffler’s internal volume is around the same or bigger than what you have now. But there is a proviso on this, more later in the article.

Stock System Now – You want a Louder exhaust and be able to switch to same-ish volume as now, at the click of a button.

You have a stock system now and you want to be able to turn up the volume when you want and revert to stock (or close to stock) levels when you don’t, I think this valved muffler should fit the bill. Again, assuming the internal volume of this muffler is close to what you have now. But there is a proviso, details below.

Quality After Fitting

I didn’t change my mind, I still think the quality is good/excellent, I have no issues at all.

What’s Next?

Because the noise level is not as quiet as stock, I’ll probably re-visit the exhaust and add another silencer (with as big a volume as possible/available) where the original factory resonator was located (towards the centre of the car & also leave this one in). With this done I think the sound will be what the owner of the car wants. But as it stands now, volume in the car is very good, huge improvement, so no rush to change it, at the moment.

Valve Actuation

I said I didn’t order an actuator with the system, so how am I controlling the exhaust valve?

Servo

I had a high power 12-volt servo (like the ones used in RC cars) lying around. I made up a bracket from some thickish steel and mounted the servo horizontally over the pipe that comes out of the muffler and goes back to the main pipe.

Heat Insulation

I used a decent amount of heat insulation on the bottom of the bracket and so far, I do not see any heat problems at all. The servo is rated to 75C (and 35kg). The max ambient temp I’ve tried it in was 15C and touching the servo, its temp seemed like ambient. Surprising given how hot the muffler gets. The heat was my biggest concern with using the servo but so far, my concerns looked unfounded. The heat shielding is definitely helping.

Weather Proofing

I should also note that I weather proofed the servo by spraying it with plastic spray (something like Plasti-Dip) and I also placed an o-ring around the base of the servo shaft (I got tips from this video).

Linkage

I connected the servo to the valve using some small rose joints and 5mm threaded bar. I was going to use aluminum plate but in testing this got very hot. With the steel threaded bar, no such issues. So far!

Control

To control the servo I’m using an Arduino. I have the valve opening in proportion to the MAF sensor signal. The theory being as air flow increases, the valve opens more ensuring no restriction to flow. I could be opening the valve too much and/or too early. But I think the settings I’m using are sensible. Touch wood. In an ideal world, I think having the valve open according to exhaust back pressure would be the way to go. This way I know the exhaust valve is only opening as much as it absolutely needs to.

To use an exhaust back pressure sensor (EBP), I’d need to put a bung on the pipe before the muffler and of course plumb & wire in the EBP sensor. This may happen in the future.

***Provisos/Warnings*** – Valved Exhaust Mufflers

The biggest issue I see with this muffler is the diameter of pipe the exhaust gases go through when the valve is closed. I estimate that its only around 40mm (I modified this one by cutting an extra hole in the main pipe to let more gasses flow in to the silencer body).

If you’re fitting this muffler to a stock exhaust system which has a bigger diameter than this (40mm), then you will need to open the valve at medium/full throttle at least, and possibly in high load conditions generally.

You do not want a big restriction in the exhaust.

And because the (stock, vacuum type) actuators are not dynamic/automatic you’ll need to remember to open the valves when you give it some.

But having said that, I did see mufflers supplied with an OBD BT dongle. I assume, when engine load gets to a certain point the valve is activated automatically.

If you don’t want to do the custom actuator like I did, getting this BT functionality is probably worth it. I mean who’s going to remember to manually open the valve every time the give it some beans?

Exhaust Valve Review – Conclusion

All-in-all a worthwhile exercise.

The main goals have been achieved, namely reduced noise levels in the cabin (so much so, tyre roar is the main noise now).

In hindsight, expecting stock volume levels from such a small silencer was never going to happen so adding an extra silencer is still on the to-do list, but much further down.

If you have a stock system with the centre silencer and you want to ability to have some exhaust sound when you want and have stock levels (or close-ish) when you don’t (and assuming your current rear silencer has a similar size to this one) getting one of these valved exhausts will probably do the trick. And if you want to make your life as easy as possible, order it with an actuator as well (I’d recommend the ones with a vacuum pump built into the external control unit. Especially if you have a turbo car. I can’t see the extra $20 spend ever being regretted for the extra flexibility).

And to repeat (because I think it’s very important), if your stock exhaust system has a bore more than 40mm, I also recommend getting the automatic actuator option I talked about above for the reason I stated above, which connects to the OBD2 system (or make your own actuator) so when the engine is under higher loads, the valve can open automatically to stop back pressure.

A Quick Word on “ValveTronic” Trademark

This term seems to be used by many different exhaust manufacturers and there is even a manufacturer called “Valvetronic Designs”. I’ll say for the record, I have no clue what the situation is with the trademark on these valved exhausts. Did Valvetronic Designs start using the term before anyone else? Or did they capitalise on the usage of the word for their brand? I don’t know.

I checked trademarks registrations for “Valvetronic” in the USA and the only thing came back was for BMW and their Valvetronic system. So I’m left wondering, can anyone use the term Valvetronic on their valved exhaust? If you know, let me know, I’m curious!

That’s it for this valved exhaust review, if you enjoyed it, subscribe to the newsletter and the YouTube channel here & I’ll see you next time.

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