Sub 10$ knock detector. (3SGTE and maybe others?)

[OnAll-FOUR]

I saw this idea in another forum and I think it is one of the best I have heard.

On the 3sGTE they come with knock sensors standard and the ECU is able to monitor its output and has a TVSV to control the boost when it detects knocking. when we fit an aftermarket ECU or boost controller we usually disable the TVSV rendering the knock control useless.

This guy had the simple Idea of connecting the TVSV output to an LED and hey presto instant knock sensor

This is definitely on my todo list as I still have the stock ECU i the car after fitting the Wolf v500. Im hoping that I can just power the old ECU and and connect up the knock sensor to it independently from the Aftermarket ECU. I can't see why not?

after my last dyno visit, i decided that i wanted a way to monitor knock on my car. after some reseach i decided to install some LEDs to monitor the factory TVSV system. for those that might not know, TVSV is the factory boost controler that puts the car into "low boost mode" when it senses knock. problem is, that we disable the TVSV system when we install an after market boost controler. anything from bad spark plugs, cold/hot weather, bad gas, etc.. can cause knock at any time. by hooking up LEDs to the tvsv pin on the ecu, you get a very cheap and very realiable knock detection system.

here are the basics of setting this up:

go to radio shack and buy 2 12v led lights (one red, one green) with built in resistors. next locate the "tpc" function on the ecu. it will be on the 1st ecu plug from the left, pin6, blue and red wire. Tee another wire into that one and run it to where you want your led to go. the way this wire works, is that when u are off boost, it provides 12v, but as soon as u boost (and the ecu senses no problems) that wire changes to a ground. get your red LED and hook up its red wire (+) to the tvsv cable. hook the other end to a ground point. next take your green LED, and hook up its red wire (+) to any power source (like the cig lighter), and hook up its ground wire to the TVSV wire (same one u hooked up the red LEDs positive wire to). then install the lights wherever you want in the car.



if u did this correctly, it will work like this:

if the car is at idle, cruising or driving off boost. the RED LED will light up
once you start to boost, the GREEN LED will light up
if you are boostin, and the ecu detects knock, the RED led will stay on under boost. if u see this, let off the gas asap because your engine is knocking. youll also notice that the RED led stays on for a few min after a knock was detected. sometimes it will even stay on untill you shut the engine off and turn it back on again.

this is a great way to monitor if the boost you are running really is safe, or if the hesitation you feel is or isint knock resonse.

total cost for this mod: $4
not blowing your motor: priceless

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Here are some additional notes on the operation of this mod, that should clear things up for a few people:

1. If you are at idle, or just cruising/daily driving, the tvsv led will stay red. This is normal.
2. Once you start to build boost, it should turn to green and stay that way until you let your foot off the gas.
3. If you are boosting, and the led suddenly turns from green to red, then you have experienced detonation. take your foot off the gas asap, and lower your boost to a level that does not show signs of detonation.

Exceptions to the rule:
The TVSV led is useless in the winter time when temps reach 40deg or lower. This is because the stock ecu lowers boost in the winter to help prevent you from boost spikes that normally happen when the air is much colder.

The factory ecu DOES NOT have any type of boost limit built in for hot summer days. Your led should stay green under boost. If you are seeing the led turn red in the summer, then you are getting detonation. This is normally caused by:

1. Running too much boost - Forgot all people that claim xxPSI is ok. Every car is different.
2. A bad AFM sending incorrect fuel and timing signals to the ecu - very common problem on the 3sgte.
3. Possible fuel system problems. Most likely a fuel pump problem or wiring problem - if you are still on your NA fuel pump, then this might be to blame.

This post has been edited by lagos: Jan 10, 2008 - 7:55 PM

[SillyCarS]

+rep i'll be running my 1g with an lt12s, i'll be looking into this

[Joshstix]

Surely for this to work, since it is just adding a LED to visually let you know when the TVSV has reduced boost, you would have to still have the full stock management installed for it to work. If you remove the stock ECU etc there is nothing to process the knock sensor signal or switch the TVSV.

[JustenGT8]

and if you're into it, then by the time you have noticed the pretty red light it's too late anyways.

I've only ever lost one engine to det and it was a 3SGTE....no warning light would have saved it. 1st det event was the last det event...all over

Just tune the Wolf well and it won't det

[OnAll-FOUR]

is it really that quick? I was under the impression that you might get away with a few before it goes?

I know when I was running the old air to air intercooler the ecu would interfear quite quickly. is it possible that the ecus are set up to be rather sensative? and hence this might actually work?

[LeeRoy]

Its going to depend how bad it is really. An engine will withstand small knocks alot longer than big ones. Also worth a note, an engine see's temperature extreme's on a dyno when its getting tuned and if its going to knock it will be during this time. With the exception of shit fuel of course.

I guess this would be one of those things that would be really useful to people using interceptor things, ie fuel cut defenders, SAFC's, etc, where it is mostly done by the 'DIY' mechanic so to speak.

[JustenGT8]

is it really that quick? I was under the impression that you might get away with a few before it goes?

I know when I was running the old air to air intercooler the ecu would interfear quite quickly. is it possible that the ecus are set up to be rather sensative? and hence this might actually work?

Factory knock sensors are there to protect Jo Average who wouldn't know det, will likely use the cheapest fuel he can find, will service his car rarely etc etc. The factory have an expectation of long life as well........all things not applicable to the enthusiast.

All the factory knock sensor ever did for me was pull timing and hurt power as it is definitely over sensitive.

An engine will survive some det....nearly every modern engine det under high load low revs and will take this no probs. On a turbo engine you'll hear mildly damaging det that if sustained will wreck you engine. So if you're paying attention i reckon you'll notice that before you notice a little red light Big engine destroying det happens in an instant and nothing will save you from that...that's what got me and you could see the 5 or so individual det events on the pistons that did the damage. On the track it felt like a single miss...all over

If it gives you piece of mind go ahead and add more complexity to your wiring...for mine it's just one more thing to go wrong

Now you have the Wolf det worries should be a thing of the past. If you're worried your IC isn't up to the job then get that WI sorted

[kaido]

that greddy boost controller that guy is running (older style profec) has an external switch function, maybe he could of worked something out to implement the TVSV into the boost controller so it switches to low boost when it detects knock

[OnAll-FOUR]

Factory knock sensors are there to protect Jo Average who wouldn't know det, will likely use the cheapest fuel he can find, will service his car rarely etc etc. The factory have an expectation of long life as well........all things not applicable to the enthusiast.

All the factory knock sensor ever did for me was pull timing and hurt power as it is definitely over sensitive.

An engine will survive some det....nearly every modern engine det under high load low revs and will take this no probs. On a turbo engine you'll hear mildly damaging det that if sustained will wreck you engine. So if you're paying attention i reckon you'll notice that before you notice a little red light Big engine destroying det happens in an instant and nothing will save you from that...that's what got me and you could see the 5 or so individual det events on the pistons that did the damage. On the track it felt like a single miss...all over

If it gives you piece of mind go ahead and add more complexity to your wiring...for mine it's just one more thing to go wrong

Now you have the Wolf det worries should be a thing of the past. If you're worried your IC isn't up to the job then get that WI sorted

Cheers guys,

Kind of ironically at the dyno day today apparently the car was pinging slightly not what you want to hear after a fresh tune. The only thing I can think is the inter cooler heat soaked and I didn't take it for a long drive to cool it down before the run becuase I was thinking that I didn't want to heat it all up too much before the run. don't know

I will give the tunner a call tomorrow and hopefully they are willing to have a look a it. The only other thing it could be is that I replaced the rotor on the distributor as it was shagged. Maybe I bumped it somehow, but all I did was take the cap and rotor off.

more incetive for WI anyway.

[ONCE-NA]

You can run the output from a knock sensor (computer, not just the actually sensor) into the wolf and get it to take out timing if the sensor detects knock. There was a how-to somewhere but I cant find it now.

[oldeskewltoy]

from my understanding.......

a knock sensor is after the fact..... while a wideband can sense a similar problem before......

So why not use a wideband and be done with it

[Joshstix]

All a wide band is going to tell yo abot is mixtre issues or missing. Running lean is not commonly the cause of detonation.

There is not much of a prem-emptive way to measure pinging, the best wold be plasma sensing across the spark plug gap to detect when combustion chamber pressures are too high.

[inertia]

oldeskewl, are you thinking of ion (sp?) sensors, like the new M5's v8 and some older engines use.

[web]

Yup, ion sensing, not sensors - it's not a sensor. Ion sensing basically monitors spark current flow. You could say the spark is being used as the sensor. Using nothing but a modded igniter, so to speak.

"ion sensing" as google words give you hours worth of reading on the subject!