Listening for knock when mapping

[Johnny176]

Evening Guys,

 

What is the best way to go about inducing a small amount of knock? Would a low RPM high gear do it? Say 1200rpm in 5th and gently accelerating do this? If I was to do something like that in my daily I would feel a strong vibration and hear a buzzing noise when I tried to accelerate

 

Reason I ask is a have an engineers stethoscope and wanted to hear what knock or pinging sounds like and if the stethoscope is actually working. Finally, would the pinging / knocking sound heard through the stethoscope from the engine made from a 5th gear 1200rpm acceleration sound the same as running slightly lean at WOT at higher RPM's?

 

Thanks

Edited October 23, 2013 by Johnny176 (see edit history)

[Guest Roger NE]

Are you confusing the difference between big end knocking and detonation type knocking, often known as "pinking"?

 

Big end knocking is due to the bearing shell having worn or cracked . . so you certainly don't want to "induce" that ! (but if your big ends ARE worn you would hear it if you blip the throttle up to about 3000 rpm and as it returns to tickover you would hear the knocking)

 

Pinking can occur due to being in much too high a gear and putting your foot down hard to try and accelerate, like you describe . . . but I don't see how you could hear that with your stethoscope while driving along !

Edited October 23, 2013 by Roger NE (see edit history)

[Johnny176]

No I'm talking about knock, det or pinging caused by lean afr's or high load at low rpm's. Don't want to be causing big end knock!

The stethoscope can be easily run to the driver seat from the engine so I could listen while driving. Just curious if anyone had any first hand experience of this

 

Thanks

[Tricky-Ricky]

LOL! I used to have one of those stethoscope's attached to my block when I was road mapping my EMU, had a long bit of silicone pipe from the engine bay through to the cabin, at least they don't get you the funny looks that the ear defender DIY det cans do;)

 

And no the sound you get from a laboring engine in high gear is not the same, similar but because the frequency/RPM is a lot higher its difficult to describe, some say its like a crisp bag being scrunched up, but I don't think its the same, but believe me you will usually hear it with that set up, are you self mapping then?

[Johnny176]

Haha you know exactly what I mean Going down the road stethoscope in the ears and laptop on the knees. A friend and I are having a go at it, I'm not against getting a pro to map it but I just want to have a go myself. People keep saying I'm gonna wreck it but I'm taking it one step at a time and asking questions - so far so good lol

The stethoscope is connected to a bolt hole about half way along the block about cylinder 4 on the intake side. The silicone tube is then run in through the passenger footwell. I can hear the engine running away but I have yet to hear any det. It's running slightly rich atm and only up to 4k rpm at 0.4 bar

Was just curious how I can test for sure that I can actually hear det before I go any further. The low rpm's high load was my first plan but I guess I can scrap that

People have said to listen for this crisp almost metallic plinking sound. Even found a few recordings from a Google search

How did you test that your det cans / stethoscope was able to hear det before you got stuck in?

 

Thanks

[Guest Roger NE]

Blimey, I never would have thought to try and listen to the engine like that while driving along!

 

I'm a Mk3 Supra owner . . . but on here as I'm replacing my 7M engine with a 2JZ

 

But don't the 2Js have Knock Sensors? The 7Ms do . . . and as my engine has higher compression than stock, I find that if I run on anything less than 98 RON petrol I get a bit of pinking, until I guess the knock sensors have told the ECU to retard the ignition timing a bit.

Edited October 23, 2013 by Roger NE (see edit history)

[Johnny176]

Yep Rodger, I'm hoping I don't have to explain what we are at to any uniformed individuals

 

Funny you should say that tho, I have a friend who has a MK3 with a 7M and his big end bearings went, he is also looking for a 1J or 2J to replace it with.

 

Yep they do but I'm running an aftermarket ECU and I'm not using them anymore, I wouldn't want to try using them for listening for knock either. Everyone out there has said get det cans and listen. I always ran on 97 RON when I was TT - best I can get in NI. Now with the single I'll still run 97 but still need to map the ECU to it

[Guest SupraV8]

Your easiest way is just to keep adding ignition timing until it pinks (light load). Usually around 36 degrees. The best way of doing this properly though is using an ECU with built in knock control, hook that up to a Bosch wideband knock sensor and bolt that to the block. Although you may be able to avoid knock in the brief time that you're out with the car, you wont always be driving the thing with the cans on. How do you anticipate catering for change in environmental values that will effect it? What about different fuels?

[Johnny176]

Sounds good, where would you recommend doing this rpm and boost wise? It's not going to plink at idle with no load will it? Are you suggesting using the Bosch knock sensor as a visual way to monitor knock while mapping or to provide direct feedback to the ECU?

I'm running a Link G4 atm and have a seperate table that will adjust fuel trim depending on IAT using + or - values to stop AFR's drifting if under bonnet temps start to rise or its a hot / cold day. I don't have any correction for different types of fuel, I'd need a fuel flex sensor, switchable maps or allow my AFR to trim my fuel table accordingly. PLanning on keeping that one simple and sticking with 97 RON all the time.

[Guest SupraV8]

I never suggested any DET' at idle with no load, but yes, given enough timing it would for sure. As it would at a steady speed (say 30MPH), stick it at 3k and just add the timing until you hear detonation. I will warn you though, it's dangerous water if you don't know what you're doing.

 

I was suggesting wiring the Bosch sensor into the ECU, setting the correct frequency given your bore diameter and letting the ECU detect the knock and adjust timing to suit. Of course, this needs professionally setting up ideally.

 

How do you know that each tank of fuel you get is going to be as stable as the last? You need to allow for crap fuel when mapping the thing too. For instance, Tesco's premium brand appears to be more stable than Shell's V-Power (my experience). This of course changes during the winter, all of the fuels change at different times of year for stability, preservation etc.

 

Before you even attempt this, I would spend a good few weeks reading and learning about this, BEFORE picking up the keyboard. I've a Supra in my workshop at the moment for a second rebuilt. It's been subject to ignoring the above advice and has a couple of rather crisp valves now. It lasted a week, and the guy spent around 6k on the engine build.

 

Just my 2p's worth, it's up-to you if you take it or not.

[Tricky-Ricky]

Yes as Mr v8 says if your running a link G4 you will be able to ad std or a Bosch sensors and setup the ECU to listen for knock and retard ignition timing and adjust fueling across the load map, so once set up correctly you should be OK, if you err on the side of caution with ignition timing.

However I used to play its safe and had a Phrmula KS4 knock detection with the Bosch wide-band sensor also fitted to my Supra full time just in case.

And as he said just add some timing on a low load area at mid RPMs, once you hear knock you wont forget, your on the right track by only making very small adjustments before moving on, I'm presuming you have a base map to work from?

[Johnny176]

Yep SupraV8, that sounds like a good way to do it. I've done a few easy runs so far and data logged it so I can see whats happening. I started with a base map and then adjusted from there to pull AFR's down as they were quite high. I'm running 14.7 while idling, 13.4 at 100kpa 13.2 at 120kpa and 12.9 at 140kpa. I know these are slightly rich but I don't want to do anymore until I know I can hear knock when it happens.

Those are good points tho, I'll have to allow some margin for changing fuel quality and other things. I know what you mean tho, theres a good few things to look at regarding the mapping. I started to this mid august and its only recently able to drive at low boost. I'd hate to be the next guy with his engine in with you for a rebuild

 

I like this safety margin Ricky, I'd hate to blow something up or melt my engine so taking it easy enough. I checked out the Phrmula KS4 and it looks a good job. I had looked at the Link knock block and the knock link for the same thing. What did you think of the KS4? Did you use it instead of the det cans?

Think I'm going to go for the 30mph 3rd gear plan and add a little timing at low load and listen closely.

 

My ignition table looks like this currently -

 

[Ian C]

The closest thing I can compare it to is the way Dude described it to me long ago - the sound of the metal ball bearing in an aerosol can of spray paint as you shake it up. A 'sping'ing noise.

 

It's not what det sounds like that matters really, it's familiarising yourself with the rattly cacophony that the engine sounds like while listening to it with det cans/stethoscope. Then, any new noise that crops up while you try and induce det is probably det

 

Don't even think about relying on the knock sensors to sort it out at the mapping stage, that's not what they do or why they are there.

[Tricky-Ricky]

Yes the KS-4 is very good, but as Ian says I would not rely on it alone for mapping, and in any case with it set up right and using det cans/scope you will be able to adjust it to show real det from engine noise,

And like I said the Link is capable of responding to det (once setup correctly) and can be set to pull an amount of ignition timing and adjust the fueling should it detect any det, obviously once you have mapped it fully, its a safety precaution for bad or low octane fuel.

 

Looking at that timing map the first thing that strikes me (unless I have got my conversion wrong) is that you will need to reconfigure the load scale (unless your going to be running high pressures?) as as it stands your never going to be using the top third of it, so your limiting the scope of the map, I'll double check my conversion and get back to you on that though.

[Wez]

The closest thing I can compare it to is the way Dude described it to me long ago - the sound of the metal ball bearing in an aerosol can of spray paint as you shake it up. A 'sping'ing noise.

 

it does stand out from normal engine noise when listening, I have used homemade det cans, knock box and the phormula kit too, all do the trick and its up to user preference really.

[Wez]

Looking at that timing map the first thing that strikes me (unless I have got my conversion wrong) is that you will need to reconfigure the load scale (unless your going to be running high pressures?) as as it stands your never going to be using the top third of it, so your limiting the scope of the map, I'll double check my conversion and get back to you on that though.

 

250kpa is about 1.5bar boost, we cannot see the rest but can assume its prob in the region of 300kpa which is 2bar boost roughly.

[Tricky-Ricky]

250kpa is about 1.5bar boost, we cannot see the rest but can assume its prob in the region of 300kpa which is 2bar boost roughly.

 

Just checked via a couple of converters and 180 Kilopascals = 26.1067928400 Psi and 250 Kilopascals = 36.259434500 Psi, so unless he is using high ish boost pressures, the top third of that map is defunct, which I why I suggested changing the load scale to something more suitable, he hasn't mentioned running big power.

[Wez]

Just checked via a couple of converters and 180 Kilopascals = 26.1067928400 Psi and 250 Kilopascals = 36.259434500 Psi, so unless he is using high ish boost pressures, the top third of that map is defunct, which I why I suggested changing the load scale to something more suitable, he hasn't mentioned running big power.

 

180kpa would be approx 0.8bar, up to 100kpa would roughly be absolute as the sensor reads vac as well as positive pressure.

 

In imperial units the Standard Atmospheric Pressure is 14.696 psi. 1 atm = 1.01325 bar = 101.3 kPa

[Tricky-Ricky]

Still amounts to a large part of the map not being utilised if he is only running lowish boost whatever way you look at the figures;)

 

It also looks like that map scale is not set up to read vac either, so a re-scale is in order.

Edited October 24, 2013 by Tricky-Ricky (see edit history)

[Ian C]

It's probably using absolute pressure rather than relative, Ricky, so 0kpa = vacuum, and 100kpa is atmospheric, so it'll measure about 21psi of positive boost which is reasonable

[Johnny176]

The closest thing I can compare it to is the way Dude described it to me long ago - the sound of the metal ball bearing in an aerosol can of spray paint as you shake it up. A 'sping'ing noise.

 

It's not what det sounds like that matters really, it's familiarising yourself with the rattly cacophony that the engine sounds like while listening to it with det cans/stethoscope. Then, any new noise that crops up while you try and induce det is probably det

 

Don't even think about relying on the knock sensors to sort it out at the mapping stage, that's not what they do or why they are there.

 

I have a rough idea as to what knock sounds like but I'm sure the first time I hear it I'll know! I can hear this cacophony of sound you are talking about lol, can hear the cams and valves a little as well but no det as yet. Initially I'm after a way to be 100% sure that the stethoscope is working rather than me just not being able to hear it if there is knocking present.

 

Looking at that timing map the first thing that strikes me (unless I have got my conversion wrong) is that you will need to reconfigure the load scale (unless your going to be running high pressures?) as as it stands your never going to be using the top third of it, so your limiting the scope of the map, I'll double check my conversion and get back to you on that though.

 

Yep my table goes up to 300kpa for 2bar, I'm not going to be running any more than 1.4bar or about 22psi. I had seen that function in the Link software but hadn't touched it since I don't have any knock feedback to give the ECU. As you said tho that would be really good to have set up incase as SupraV8 said earlier I get bad fuel or something has me running lean.

 

As far as my figures go in the ignition table do they look normal enough?

[Tricky-Ricky]

It's probably using absolute pressure rather than relative, Ricky, so 0kpa = vacuum, and 100kpa is atmospheric, so it'll measure about 21psi of positive boost which is reasonable

 

That calculation was absolute Ian, but relative does work out to 246.11490699216168 KPa, =21 psi as you say so the map must be as you say taking vacuum into consideration doh!

[Wez]

It's probably using absolute pressure rather than relative, Ricky, so 0kpa = vacuum, and 100kpa is atmospheric, so it'll measure about 21psi of positive boost which is reasonable

 

This is exactly right and how most ECUs interpret load when using kpa

[Guest SupraV8]

I wouldn't be running any more than say 33-34 degrees timing until you know how your engine behaves. That map you uploaded is showing 40 in some places, I would quite happily place bets on that starting to knock around that area. Where did you get the base map? Was it straight from link or someone elses map that's been messed with?

[Tricky-Ricky]

What I usually do is find a std fueling and timing map and start from there, that one does look a little odd in places, I did have a couple of std maps saved, I'll see if I can find them.

 

These are not the ones that I was hoping to find but you will get the idea, the first is a std TT timing map, a bit hard to make out, the second is from a tuned TT just to give you and idea, I am not suggesting that you use either of them but it should help with ideas on values differences.

 

 

Edited October 24, 2013 by Tricky-Ricky (see edit history)