Knock sensing on an A20?

[cygnus x-1]

So I'm wondering, has anyone ever managed to get knock sensing to work on an A20? Obviously you would have to use a sensor from another engine and have a way to process the signal; but it would work just the same.

Awhile back I rigged up a home made sensor by RTV-ing an electret microphone (out of an old cell phone head set) into a large crimp on ring terminal. The terminal is bolted to the side of the block and I can listen to the noise with a small mic amplifier and some headphones. I have some idea of what to listen for but I haven't yet heard anything that sounds like spark knock. But then I haven't heard the engine actually ping either that I can tell for sure. My intake manifold makes some odd screeching noises at certain MAP levels and sort of a loud hissing at higher RPMs so it's hard to listen for pinging.

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[86AccordLxi]

The simplest way is to hook up a knock light.

I put one of these on my ka24e-t, and seemed to work ok: viatrack.ca

the sensor itself should be placed between cylinders #2 and #3, about 2 inches down from the top of the block (headgasket). Because the ka (and I'm assuming the a20) doesn't have a good spot to drill and tap a hole (and because that makes me nervous as shit), I used a big magnet to attach it. I'm not sure if that messes things up, or what effect it has, but I did get the light to come on at 14psi vs 9psi.

[cygnus x-1]

Yeah, I've seen that before. I have a Megasquirt too so I can datalog it too along with everything else. Did you get the sensor from them too?

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[86AccordLxi]

Yup, got everything from them.

[Dr_Snooz]

The simplest way is to hook up a knock light.

I put one of these on my ka24e-t, and seemed to work ok: viatrack.ca

Getting a malware warning when I visit this site?

[2oodoor]

good thread
the detonation in these as far as I noticed, is very subtle as far as slightly lean, of course speaking only of basically stock engines.
Seems like an exhaust temp sensor would be nice to have on a NA engine with extreme mods.

[Dr_Snooz]

I'm two years late to this party. Anyway, I've been reading up on knock sensing a little more. MSD makes an aftermarket knock sensor kit for too much money. There are a few different kinds of knock sensors, but they are all basically a piezoelectric crystal (like what lights the click-type cigarette lighters) housed in a sensor bolted in the block. The crystal fires when rattled at 15kHz, which, conveniently enough, is also the frequency that pinging makes in your block. You just need something that can detect the sensor producing voltage and light up a warning light. (Well, ideally, it would dial back the timing, but you'd need computer-controlled electronic timing to do that.) That's the theory anyway. It should be relatively easy to find old knock sensors at the junkyard. You'd be looking for an older one with only one wire and no special boxes between it and the ECU. I'm not sure what to use to detect any signal it puts out.

I'm probably going to try HHO here in the near future and getting it to work properly requires leaning out the fuel mixture when you are running the gas. Too lean and I get to rebuild another engine. Seeing as I just rebuilt the dumb thing not more than a couple years ago and that I can't hear when it pings, some kind of electronic knock detection is very important to me.

[Dr_Snooz]

I'm two years late to this party. Anyway, I've been reading up on knock sensing a little more. MSD makes an aftermarket knock sensor kit for too much money. There are a few different kinds of knock sensors, but they are all basically a piezoelectric crystal (like what lights the click-type cigarette lighters) housed in a sensor bolted in the block. The crystal fires when rattled at 15kHz, which, conveniently enough, is also the frequency that pinging makes in your block. You just need something that can detect the sensor producing voltage and light up a warning light. (Well, ideally, it would dial back the timing, but you'd need computer-controlled electronic timing to do that.) That's the theory anyway. It should be relatively easy to find old knock sensors at the junkyard. You'd be looking for an older one with only one wire and no special boxes between it and the ECU. I'm not sure what to use to detect any signal it puts out.

I'm probably going to try HHO here in the near future and getting it to work properly requires leaning out the fuel mixture when you are running the gas. Too lean and I get to rebuild another engine. Seeing as I just rebuilt the dumb thing not more than a couple years ago and that I can't hear when it pings, some kind of electronic knock detection is very important to me.

[A18A]

Interesting. I'll be looking forward to your project Dr. Snooz

[RobT5580]

I tapped a knock sensor into my B20A on the rear of the block which was read on my AEM EMS. I realize that many would not buy or use the AEM but i did enjoy the many features it had. I plan to use Hondata this time so i will have to look into the options but it should do much more than what i will need.

[Dr_Snooz]

Rob, do you know if it worked or not? I read a thread elsewhere last night and the posters were pretty convinced that retrofitting a knock sensor is really hard to do. According to them, every engine has it's own resonant frequency ranging from ~4-6 kHz (not 15 kHz like the one page I read said). To get the knock sensor to work, you'd have to determine your engine's resonant frequency and then find the specific frequency a knock in your engine makes using an o-scope. I think that's overstated though. Pinging is a very distinct sound. Anyone who hears it knows it. Either the thread is wrong or the one-size-fits-all sensors don't work on all cars.

I will probably build something like the "Build Your Own Knock Sensor Display" like on this page so I can watch and make sure everything works. Once I've decided that it's working okay, I can integrate the sensor into a Megajolt box someday if I decide to do EDIS.

[Dr_Snooz]

Rob, do you know if it worked or not? I read a thread elsewhere last night and the posters were pretty convinced that retrofitting a knock sensor is really hard to do. According to them, every engine has it's own resonant frequency ranging from ~4-6 kHz (not 15 kHz like the one page I read said). To get the knock sensor to work, you'd have to determine your engine's resonant frequency and then find the specific frequency a knock in your engine makes using an o-scope. I think that's overstated though. Pinging is a very distinct sound. Anyone who hears it knows it. Either the thread is wrong or the one-size-fits-all sensors don't work on all cars.

I will probably build something like the "Build Your Own Knock Sensor Display" like on this page so I can watch and make sure everything works. Once I've decided that it's working okay, I can integrate the sensor into a Megajolt box someday if I decide to do EDIS.

[cygnus x-1]

You know, I messed around with the home made knock sensor but I have NEVER been able to observe the engine pinging for sure. I've had it so lean that it was misfiring badly, but still no pinging. I tried advancing the timing but eventually chickened out. My old Chevy would ping easily but this A20 just doesn't do it. Or I can't hear it anyway. It would be interesting to see what other people can figure out.


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[gp02a0083]

snooz i wouldn't even bother with the HHO, not sure what you exactly want to do with it, its been thrown around here and there , but i think its been proven that its junk. Look more into it , i have some articles i can dig up if i can get my other computer to work, but basically you will need a high frequency generator , and a saturated sodium hydroxide solution if i remember correctly.

cyngus you probably heard the knock/ping easier on the v-8 being our engines are 1/2 the size. I never have had a problem with knock or ping with the 3 FI hatches ive owned

as far as resonance frequency is concerned , that's something really really tough to pin point and it may have several resonance frequencies between that 4-6kHz range, ive recently sent out samples to have acoustic, vibration and shock tests done outlined by NASA. ill tell you one thing the acoustic testing is really frigging expensive if someone was to go through with it , its roughly 10-15k to rent the time and have the test preformed.

i would have thought the resonance frequency would be more or less in the mega Hrz range

[RobT5580]

Mine worked because my AEM EMS logged all of the engine noise so i could tell when looking at my laptop. Mine was added as a way to see my engine noise while using a computer. I never looked at the frequencies but when i blew it up you can see when it happened in reference to RPM's etc.

[Dr_Snooz]

snooz i wouldn't even bother with the HHO, not sure what you exactly want to do with it, its been thrown around here and there , but i think its been proven that its junk.

I know it's real controversial. I'm not sure it will work, but here's the deal. I've been disappointed by all the self-proclaimed experts who have pooh poohed HHO without genuinely testing it. I've seen lots of rhetoric about how it won't work, but no honest tests that weren't compromised in some way or other. For instance, I read a Popular Mechanics article the other day where one of their editors put a generator on his car for a few days and proclaimed that it didn't make any difference. He didn't install a fuel preheater, or an EFIE, didn't lean out his fuel mixture or anything else that HHO guys tell you to do. He just stuck the bubbling pot under his hood and waited for a miracle. He didn't even bother to measure his fuel consumption! He had some gizmo in the car that measured injector pulse width while he was driving. The pulse width didn't change in the two weeks he tested it, so he proclaimed boldly that HHO was complete bunk, though he hadn't even measured his gas mileage! That was the article that convinced me to try it.

I see all these guys with fancy credentials telling me it won't work based on their opinions and false tests. There is another bunch of guys without fancy titles telling me it does work based on their experience. Whom should I believe? I'm also impressed that, unlike fuel line magnets, vortex swirlers and other such nonsense, HHO has well outlived its initial hype. It's still around after all the controversy and guys are still building it in their garages and saying it works. It may not work, but I'm sufficiently intrigued to find out for sure.

Wish me luck.

[cygnus x-1]

I saw that PopSci article and wasn't impressed. There have been more controlled lab studies done on hydrogen injection in order to assist lean burn combustion, but the variables are many and I don't believe there has been enough study to make a determination either way. Although ultimately it probably won't matter because direct injection will move gasoline engines closer to diesel like operation which are lean burn by their nature.


I know the combustion chambers on the A20s are pretty lazy, making for a slow and not so efficient burn as compared to newer designs. This combined with the short duration at TDC (short rod to stroke ratio) makes for a highly knock resistance engine.


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[Dr_Snooz]

I think the opportunity is that the gasoline engine is roughly 25% efficient. The most efficient engines get near 30%, but that still leaves all kinds of room for improvement. I mean, we put catalytic converters and smog pumps and all kinds of smog controls on cars because so much of the fuel we put into the combustion chamber gets dumped, unburned, right out the tailpipe. That's shockingly inefficient. There's plenty of research out there showing that hydrogen supplementation allows you to run a much leaner fuel mix without making a lot of NOx emissions or knocking your engine to pieces. If anyone is interested, some articles are available here, about 1/4 of the way down the page under the heading "Research." The real question is, is hydrogen potent enough to offset the power penalty of producing it on demand as you drive?

It's nice to know that the A20 is relatively knock proof. I will probably try water injection too. If I can get it all to work, I should be able to use a very lean mix indeed without issue. That's the theory anyway.

[cygnus x-1]

What I was getting at is that there are other ways to accomplish lean burn without using hydrogen injection. And the OEMs are doing those things. So even though it may work, it's probably going to be irrelevant before long.

BUT, if you can make an A20 run leaner than about 16:1 without misfires, that will be something.

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[hondalude86]

I hate to bring up an old dead thread here, but i was also curious about listening for *ping, but still I've not noticed that my car was pinging. The most ignition advance i've ran at WOT is 46degrees of advance, but of course I also have a blown head gasket helping saturate the mixture (think of it as water meth injection! hahahaha). Anyway, I'm still curious about this, and would love to see this thing roar back to life with more info!

[cygnus x-1]

I hate to bring up an old dead thread here, but i was also curious about listening for *ping, but still I've not noticed that my car was pinging. The most ignition advance i've ran at WOT is 46degrees of advance, but of course I also have a blown head gasket helping saturate the mixture (think of it as water meth injection! hahahaha). Anyway, I'm still curious about this, and would love to see this thing roar back to life with more info!

46 degrees at higher RPM may not be enough to induce spark knock because there isn't sufficient time to build enough pressure. The most likely place for knock to occur is under high loads at low RPM. Put it in 5th gear at 2000RPM and mash the throttle.

It seems to me like the first thing needed to figure this out is an engine that knocks. I'm not particularly keen to volunteer mine though. And probably neither would anyone else.


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[2ndGenGuy]

Last time I was listening for knock to tune my ignition, my head gasket blew out. I can make my car knock pretty easily. I'll volunteer to test it out if someone wants to send me some knock sensing equipment. Maybe the ARP head studs will help this time.

[2oodoor]

bump, that's interesting now because the only time i've ever heard any of mine pinging was when it did have a blown HG.
It never overheated nor was the matter caused by overheating.

[ShyBoyCA6]

Mine engine is knocking loud but you can't really hear it when its at idle. when i drive in low speeds i can hear below 2500rpm, after that you can't really hear much. i would volunteer but i don't have the money to do this project. I'm just gonna dump the block in the scrapper since its been knocking for the past 1,000 miles and really dont wanna bother fixing it up.

[DBMaster]

Mine used to ping plenty when it was newer, especially in the summer. I had to run mid grade (89 octane) for the first half of the car's life. Reformulated gas (RFG) was a mixed blessing. Initially, it had a bit of ethanol and MTBE mixed in. Later, the MTBE was eliminated and the gas now contains 10% ethanol. While it does mean lower fuel economy, the "increased octane" from the blend pretty much eliminates the pinging and I have been able to run on regular 87 octane for a long time. Of course, I cannot advance the timing beyond the factory specification of 15 degrees BTDC.