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knock analyzers on stock ECU

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While doing some tinkering with my supercharged 4 cylinder I am at a point where I need to adjust my ignition timing to suit more fuel. I have been looking at knock detectors that I can permanently attach to the dash to help in tuning my car. Looking for an entry level device as I am on a budget and do not have every day access to a garage, dyno, and still running stock ECU.

I have come up with 3 big contestants and wondering what people have used and what works well.

#1 is the KnockLink G4 by Link engine management for around $300 USD. I have heard great things about it, it is a self-calibrating knock light about the size of a shift light. However it seems almost impossible to buy and get in the USA as no Link dealers keep them in stock or have returned my emails so after almost a month I am giving up finding one.

#2 is the KS-3 Analyzer by Phormula for $357 USD which has manually adjustable bandwidth, audible and visual alerts, back-lit LCD screen with a numeric display and graphing, however looks bulky and difficult to mount to the dash and comes with an accessory power cable I don't see any way to permanently wire it into the car, I'm hoping someone has installed one that can tell me different. Also available is the KS-4 and KS-pro that would be better suited for tuning multiple cars every day as they are super accurate with data logging, optional headphones, external triggering, and very expensive.

#3 is the last reliable device I found, the K-lite by Gizzmo Electronics for only $250 USD with 11 frequency & gain settings, automated self-calibrating procedure, 6 knock display levels, peak recall and housing 2 processors and the accuracy of their $580 KMon professional knock computer in the size of a shift light. I have heard nothing about the K-lite but the Kmon has glowing reviews and was tested out by DSport magazine.

If anyone has had any experience with these I would love to hear it, especially the K-lite as that is looking like the best choice for my current application.

On your list I would had the Plex knock monitor, but even more expensive than the Phormula.

There have been several discussions on the old forum about most of these products. Here is my notes on the products you list:

1. The KnockLink G4 is a great product for the price point and is perfect as a quick and easy visual indication. It seems to be about 95-99% accurate which still leaves a margin of error I'm uncomfortable with. I would always recommend confirming the accuracy of it with audio knock detection.

2. the Phormula KS3 is a product i haven't personally tested. Plenty of our members use it and speak very highly of it. This is a product that is much more sophisticated than the KnockLink though and is better suited to professional use.

3. I haven't used the Gizzmo K Lite so can't give any feedback on its accuracy or ability unfortunately. I actually did some beta testing of the k Mon before it was released and found it to be basically useless. it had so much static or interference that I couldn't distinguish anything at all through the head phones. I'm unsure what their production models work like as I never got sent another unit for testing.

If you are serious about tuning, I would recommend spending a little more cash on an audio knock detection unit.

My specific application I'm mostly looking for something small and easy to mount to the dash permanently and I like the idea of having something simple like an idiot light to tell me when there is an emergency, but I understand what you're saying that you get what you pay for. I'm going to give the K-Lite a try and see how that works for me, but when I decide on my stand alone ECU I'll invest in some better knock detection equipment.

Really liking Phormula's KS-4 the more I read about it and its features like the numeric display for only $450 and you can attach the separate KS-Pro for the headphones. I'm just not sure about is as a permanent fixture on the dash, better for tuning and removing.

Thanks for the input on the Kmon. They just released the Kmon2 I wonder how that compares and if they have fixed their issues...

I've tuned a few cars that came in fitted with the Phormula KS-4 kits fitted.

It was registering audible knock counts on the screen the same time as I could hear it in the headphones of my Knock Box setup.

It did pick up a bit of background noise however I was pretty impressed.

What is everyone's opinion on the Plex unit? How is it reliability? I just have a hard time totally relying on anything but my headphones.

Ive got the Gizzmo K-mon, (retail release) and I have the same problems Andre had... Ive sent them a few emails also and no reply at all... I would not recommend it. im planning to get a Plex knock monitor next

We have also tried the Gizzmo Kmon and Kmon2 and returned both units to the supplier (who was very pleasant to deal with)

Both units suffered major noise issue and made it very hard to distinguish true audible knock.

We now have the PLEX knock monitor V2 and the Link G4 knock block, both these units are very good and offer clear audible knock detection.



I worked with a KS-4 and KS-pro since i started with tuning and tested recently the Plex knock monitor V2.

I installed both last week on an Subaru Ej207 and compared them together. To give you a small review:

Audio: the KS-pro has slightly more background noise frome the electric interferences . I would say you can distinguish knock easy on every second engine. But on the other half, i needs alot of concentration on the KS-Pro to listen for detonation. The filtering on the Plex makes it much easier to hear knock and it is much less exhausting if you are tuning for several hours. You can also turn on a beep ton if knock is detected. This will turn on your full attention if you are working on other stuff and maybe have reduced the volume level. In generally I had to turn up the volume on the KS-pro really high (which is bad for our ears in the long term) do clearly distinguish knock. That’s not necessary on the Plex device.


I always felt that the KS-4 detected knock really really well on high rpm and quite often detects knock before you even can heard it. But it has a lack to adjust rpm dependent noise threshold. If you run into clear det it will show that, but the threshold at low rpm is often too high to trigger knock if the engine suffers only light det. A work around is to do dyno runs only to say 4500rpm and adjust the threshold lower.

The Plex offers the ability to adjust rpm dependent threshold which is a quite good thing. I found it a bit difficult to find the right threshold, especially if you raise the boost. If found that noises on lower rpm can raise more while you raise the boost relative to the changes at high rpm. I have to made some more experience on other engines.


Both manufacturers offers a good case which it’s up to the task for daily use on the workshop. I really like the professional motorsport-like wiring on the PLEX unit. The plugs are nice, but unfortunately no very handy to plug/unplug very often. The KS-4 and KS-Pro are connected through stereo cables (2,5mm earphone plugs), which I had to change twice over the years. The earphones which comes with the KS-Pro does have a very good quality and will last for a few years. Plex doesn't come with any earphones. It has two 2.5mm outputs which are useful, while you listen on one channel and feed the other one to MIC input on your laptop to make a FFT analysis to find the right knock frequency or let your buddy listen to your engine. Also a nice thing is the PC software which comes with the Plex Knock Monitor V2. Actually the software is quite basic and there is a potential for some additional functions like FFT analysis.


The KS-4 (or KS-3 without output) is a quite good and reasonable priced unit. It's a good tuning aid and one of the best insurance for your performance engine (of course a Plex knock monitor would be even better, but much more expensive) The KS-Pro are good product, but has definitely a lack of audio filters.

If you are looking for a tool to tune engines or you are willing to spend a lot for a fantastic engine insurance and make a permanent install, the Plex Knock monitor looks like the benchmark at the moment. The main benefits are the audio filters and rpm defendant knock threshold over the Phormula products. In addition it is one unit, don't need to be connected together (KS-4-KS-Pro) and can be powered over USB, which makes it very hand for the usage on the dyno and for workshops.

Reaper Customs, I just read the review of the Kmon by DSport magazine (http://gizzmousa.com/file-copies/GIZZMO_KMON.pdf) and it looks like there is a special feature where you can adjust the frequency but also a noise filter to focus in on detonation noise, did that make any difference or is there pretty much no way to filter out engine noise?

Adrian, how was it mounting the KS-4 in the vehicle is there a way to permanently wire it into the car or are you limited to the auxiliary power cord?

It looks like the only USA dealer of Plex Tuning products is AMS performance in Illinois I may have to email them for a price quote.

absolutely no problem to mount the unit. You have only to connect to a ground and 12V source and plug in the knock sensor, which is delivered with the kit. You can also connect it to OEM knock sensors, but i found the Bosch donut style sensor, which is delivered with the kit work best.

Do many of you guys use the "Knock Box" product by Smith Racing?

Hey Gerken, You can choose a center frequency and then a bandwidth either side of that to filter out other engine noise... But engine noise isnt the problem... For whatever reason (im not pc or audio guru) the system is extremely sensitive pc noise sources, By that I mean If I have the Laptop charger plugged into the laptop with the Gizzmo running on it I get alot of static through the headphones... Same if I have the same laptop plugged into the dyno or ecu... I have to run it on a dedicated laptop that is fully charged and not too close to my other laptops or the thing just buzzes..

No doubt there is a fix for this... but they wont reply to emails and there isnt many other avenue's for support.

If I do all that I can get fairly clean audio, but still dont trust it 100% yet

Hey benchmark,

The Knock box was actually the first knock detection system I used and relied on. It's a pretty good piece of equipment by all accounts and does a god job. It's similar in performance to the Link G4 Knock Block but doesn't offer the ability to output knock info to an ECU. It's not quite as sophisticated in its noise cancelling compared to the Link unit and definitely a step behind the Plex. All things considered though it is an effective product.

The only thing I didn't like was that it uses its own specific knock sensor which means if the sensor got damaged you couldn't simply fit a new Bosch donut-style sensor. Not a biggie if you don't damage the supplied sensor though I guess :)

I currently use the Link G4 Knock Block but as they have recently discontinued production I have just purchased a Phormula Pro Kit with KS-4 and analyser to replace it, product support is key should something happen to the equipment.

I considered the Plex unit as I was introduced to it a long while before general release whilst it was under beta testing but for soe reason thought it was out of my price range, I really didn't think the price was as close to the Phormula until I checked my old email after I had placed my order.

Not to worry I'll be putting it to the test in the next few days and will see how it performs and integrates with my Dynapack

Love to hear your comparison chris, since I used the same setup (phormula KS-4,KD-pro and Dynapack) and i've wondered for a long time how it willl compare to Link's knock block.

Sorry if the question is off topic, can I connect more than 1 instruments in a single knock sensor? For example the ECU and a Knock monitor, or headphone...

@Fabry, I wouldn't recommend sharing the knock sensor output between devices. The signal level is quite low and sharing it may result in a reduction in signal strength. For example if you have a car with a factory fitted knock sensor, I would always add an additional sensor for my knock detection system.

Hi Andre, perfect, Thanks for this reply...

Can I mount the extra knock sensor in the same place of the factory? If no...how I can find the good place to mount the extra sensor?

I have the same question, where to and how is the best way to mount the aftermarket knock sensor? I was told anywhere on the intake side of a 4 cylinder block is ok and on a V style engine pretty much anywhere on the block? What about on a boxer engine?

Center intake manifold bolt seems to be the most commonly used place for inline 4's

H4's run the factory sensor on the passenger side block half way up piston #4

Ideally you want to mount the knock sensor to the engine block high up near the deck surface. You can always take a guide from where the OEMs mount their stock sensors and try and replicate the location.

Often you will be limited as to where you can practically mount the sensor and the ideal spot may not be possible due to a lack of free threaded holes. In order of preference I would aim for:

1. The top of the block near the deck surface, ideally located somewhere centrally

2. Low on the engine block

3. On the cylinder head (can be problematic for solid/mechanical lifters)

4. On the intake manifold.

@Adrian, I finally got to test the Phormula at the weekend and it is about 10 times better than the G4 Knock Block, I had the volume turned down to a third of full volume, the Link has always been used on full volume as it always felt a little bit quiet. Both units used without any filtering, knock sensor on the same location on the same engine. Definitely money well spent

PLEX = Brilliant, Excellent, Outstanding

im curious what you guys recommend for a friend looking for a "safety net" knock detecting system.

have a friend who wanted a knock light on a haltech platinum ECU, now I know you can use a 0-5v signal to act as a trim to remove timing. but it seems expensive to put a knock block or Ks-4 in a car for just a knock light.

are there any more accurate and cost effective methods to add a knock light to a non- knock sensing ECU?

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