Easy Knock Detection System for the 3sgte!, DIY ! Options

[lagos]

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

----------------------------------------------------------------------------------------------------------------

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

[MaskedMan]

wow this was a great writeup man, i will try this out on my Alltrac! (when i get it running right )

[hitcachi]

mega siiiccccccccc. Sticky most definitly. This is awesome.

[beno]

What specifically happens when knock is occuring?

[airfron]

What specifically happens when knock is occuring?

For you Beno Click Me!

Awesome idea Lagos def. worth $4......STICKY!!!

[zipstrips]

thats an intresting way of checking knock.... where'd you come up with this one! im going to look into doing this too i think. how bright are the LEDs at night that high up on your dash?

[CilverSeliST205]

Just brilliant

[lagos]

thats an intresting way of checking knock.... where'd you come up with this one! im going to look into doing this too i think. how bright are the LEDs at night that high up on your dash?

well, its not really an original idea of mine. there has been talk of doing this on mr2oc for a while now. so i decided to look into it and see how well it works. the leds and very bright and easy to see. a lot of it will also depend on how close to eye level you put them. i think the spot i picked for mine works out perfectly.

so far i managed to test this AND it did pick up knock at 1bar of boost that i was not aware of ! its pretty amazing how long the stock ecu tries to keep you in low boost mode after a knock. i did a 1st and 2nd gear run, and it stayed in low boost mode for the rest of the time the car was on. i had to turn it off to get out of it. then another time i got knock in a 4th gear highway run at about 5grand, but after that one, it only took 30secs or so to go back to normal. now i got to figure out why im knocking at those boost levels. it really opens your eyes to how you should never just go by what other people say is ok boost for your car.

[Bitter]

any idea if something like this would be easy to do on a 7afe of 5sfe?

[lagos]

any idea if something like this would be easy to do on a 7afe of 5sfe?

pretty much impossible. those enignes didnt come with a factory turbo, so their stock ecu dosnt have a low boost mode you can monitor.

but, what you can do, is get an safc2 and use its knock detection feature to monitor the knock sensor. you wont get any type of warning, but youll have a knock value that you can compare to your other runs.

[Bitter]

well i know theres no turbo or low boost, and i know about the safc2 (i got one awaiting install) but do you know where i can find information about what voltage level corresponds to how bad of knock?

[lagos]

there is no easy way to monitor it from the knock sensor. the knock sensor is just a microphone. it picks up all kinds of engine noises. so there is no easy way just to tap in a cheap led into it without some complex processor to figure out what is or isint knock. if u really want an LED, some company makes an expensive device called the knock guard, that will do pretty much what my tvsv leds do.... but its way over priced. i would just hook up the safc2 if i were you and use that.

[Bitter]

i have a way to watch its voltage, but i have no reference as to whats a normal voltage reading and whats considered knock.

[lagos]

i have a way to watch its voltage, but i have no reference as to whats a normal voltage reading and whats considered knock.

but what im trying to say is that i dont think it would work correctly with just something like a multimeter.

anyway, here are some tech specs on the factory knock sensors
http://www.autoshop101.com/forms/h38.pdf

[Bitter]

yea, ive seen that already. theres no specs contained in there, just a general description of operation (which i already understand well).

[lagos]

your best bet will be the safc then. install it while the car is still NA and watch the values you get, then when u turbo, youll know if you go above that value then you probably have knock. you can also compare your numbers to what other safc owners are getting on their cars and know whats good/bad that way.

[NuclearHappineS]

1- if the light isn't red that doesn't mean that you are 100% knock free (just so you don't trust your life when the light is green).

2- u can't log the knock sensor voltage... because it's based on a knock count...

u have to take the sensor voltage and filter it at a specific frequency (a frequecny that corresponds to the resonant frequency of knock in a 3sgte) ...the frequency IS motor specific... then once you have the voltage data for JUST that band of frequencies you threshold it at a certain amplitude... and even then, crossing that threshold doesn't mean you have knock...

either , 1 you cross that threshold mutliple times within a fixed time window (which you will hear DSM guys refer to as knock count) and if that count is greater than x counts per second then u have a knock EVENT which causes ECU responce... or you have to look ath teh SLOPE of the voltage at that frequency... if the peak voltage rises rapdily say from 0.3 volts to 2.3 volts that means there's a knock event...despite of where the actual knock count threshold comparison voltage is...

so in short... no it's quite complex to make your own HKS knock amp

[Bitter]

thankyou

[presure2]

cool idea, art.
added to the stickys

[CilverSeliST205]

next locate the "tpc" function on the ecu. it will be on the 1st ecu plug from the left, pin6, blue and red wire.

Diagram below shows that "TPC" is the pin#12 for JDM st185 1993 gen2 ?? IIRC that is the same ECU you are sporting ??

only USDM sw20 gen2 from 1991 has TPC on pin# 8

little explanation ?