www.neons.org

This weekend I built a "det can" and I decided to take pics and do a write-up in case anyone else is considering doing one. This should give you some ideas and detail my experiences.

So first let me say that I have no idea why this thing is called a detonation can, or "det can" for short, but that's the name given by the honda guys that are building them. There's really nothing can-like about it, but I suppose it's as good a name as any. It's catchy.

The purpose of this device is to provide a "stethoscope" that allows you to listen to the combustion events in your engine while driving or while working a tuning laptop in the passenger seat, allowing you to hear spark knock under heavy load.

The honda-tech thread that details this and the honda-tech pics I based my design off:

http://www.honda-tech.com/zerothread?id=1555006&page=1





My materials list, all from home depot:

$3.55 - 2' length of 1/2" copper tubing
$2.88 - Loctite stick and seal plastic gap filler glue
$9.94 - Ear protectors
$9.97 - 50' PVC 3/8" air compressor hose w/ fittings
$1.97 - 3/8" plastic tee

Total - ~$29

Freebies I had: chunk of 5/8" heater hose, hose clamps, a 3/8" to 1/4" pipe bushing, pipe thread sealant, bolt, stepped drill bit, other tools

Original purchase (plastic tee not shown)


The cheap ear protectors pop apart easily.


Use a stepped drill bit to put a hole in each surround on the ear protectors, and a piece of sand paper to rough both sides of the plastic up to help the glue stick better. I drilled the hole just big enough so that I could barely squeeze the hose into it. If you don't have a stepped drill bit, just be careful you don't crack the plastic with a regular wood/metal drill bit.


Cut sections about 3' long out of the middle of the air hose, and use the loctite glue to seal them into the holes in the ear protector surrounds. The goal here is to make an air-tight fit and make one that will hold up against some movement and tugging as you use the thing. If you really want to get fancy, you could get some 90* pipe fittings and thread them into the ear protectors, and adapt them to some barbs. But I'm cheap and glue works too


I glued both the inside and outside of the surrounds and let them dry over night.



Once the surrounds are drying, start on the engine end of the device, beginning with the copper tubing. I used a bench vise to flatten about 2.75" of the copper tubing.


Then I used a combination of the vice and a hammer/anvil to fold the metal on itself, making each leaf ~3/4". The goal here is to make one end air-tight so no sound escapes out of it.




Once that's done, cut a few inches of the tube off and drill a hole. The knock sensor hole on the front of my 2001 PT 2.4 engine is 10mm, so I drilled a 3/8" hole and it fit very snuggly. YMMV, depending on year, 2.0 vs 2.4, placement on block, etc.


The air compressor hose I got came with 1/4" NPT ends on it. This hose was really quite an amazing buy, 50' of 3/8" hose rated to 300psi with fittings attached for less than 10 bucks. China is revolutionizing the way we mod cars I added a 3/8" bushing over the end of the hose.


Then I took an old piece of used 5/8" heater hose, and the copper tubing and bushing fit perfectly into. The bushing has to be turned in, and then the copper tubing will fit perfectly in. I clamped the whole assembly together.


The next day, when the glue on the surrounds has dried, put the whole thing together. Decide how you're going to route your hoses, and mock them up so you can cut them to length. If you managed to get the 50' roll of air hose, you've got plenty to play with. I used a cheap 3/8" plastic tee to split the signal between the ear protectors. The finished assembly:


I bolted mine right where the knock sensor used to be, on the front of the motor between the water pump inlet tube and the starter.


The tube routes nicely underneath the bump in a DOHC hood. With the hood closed, you can still freely move the tube. Make sure you use cable ties to keep it away from belts and hot exhaust parts. I also tied mine to the review mirror to keep it from flapping at speed.



And when you get all done, you too can look this cool


Final thoughts:

This thing is fantastic. I recently purchased a knocksense unit for my MS and was a bit disappointed... turns out that electronics are terrible at distinguishing knock from just random noise, and a turbo motor makes a lot of noise. The human ear is very good at this task. This thing keeps noise from the wind, the exhaust, and the rest of the world out, and all you hear is the individual combustion events. You can here them really well at idle, especially because the rest of the car is so quiet. It sounds like an even beating coming from inside the motor. As you rev up, it smoothly speeds up, allowing you to hear only what you're interested in.

I took it out and did some 15psi runs with this apparatus strapped to my head and it really helps you hear what's going on. I wish I had some objective way to measure the performance here and present it to you, but like most DIY spark tuning this device is very subjective. All I can say is I'm a lot more pleased with this then I was the knocksense, and I've only been using this for one day.

Wearing this thing does make it hard to look left and right at intersections tho,

If I can find a microphone for my laptop, I'd like to get some samples of what it sounds like while driving, and then advance the spark until it starts to knock a bit and record that as well.

Feel free to send questions, etc. Enjoy !

-Eric

Nice work! I can't wait to build my own.

Cool. I needed an excuse to wonder aorund Home Depot for a while. My JAW should be here by the weeks end too. Home built tuning tools FTW!

Whoa. Very cool.

I've always known headphones as "cans", especially when they're big over-the-ear style ones like those ear protectors look like they are. "Det cans" makes sense to me. they're cans (headphones) that let you hear detonation.

I believe I shall be building a pair of these at some point too.

Good stuff, i have that same orange hose for my air compressor 2x50" lengths and it was $10 at Lowes.

I will be building some also, but was thinking of using smaller dia hose if the price is right.

I will be doing some test also, specifically to find out if 100%meth or 50/50 water/meth is better. Going to keep low boost(13psi) w/ just 93 octane and add timing till I hear something. Then run 100%meth @ same boost and add timing, then add 1/2 gallon of water and mix up in tank, do some pulls to make sure it starts getting the mix(not just straight meth in the line), then add timing to that. Reason being is I cant find any concrete data on which is better.

Good luck, normally find where it pings(should be torque peak) and remove 2 deg's there and leave the rest and test again. Knock is less likely at high rpms, above 6000rpms, so you can normally add 2 degs or so after peak torque for a little more peak HP.

you know...it looks goofy and ghetto as hell, but its an ingenious idea really...I think I'll be building me a set when I get to that point

Thats bad *a#S!d^f*. Does this count as being a cyborg, where your own hering is suplemented by mechanical devices? i submit that it does!

http://autospeed.drive.com.au/cms/article.html?&A=0348


here's another solution

WOW great write up. I to didnt like the Knocksense. I might build this today and see how it works.

This is from that article.


It basically says that if you dont use the stock knock sensor, which is tuned to ~6KHZish(afaik, at least the older 8v td motors are, but have a 1 wire sensor, newer are 2wire, should be similar). Then hearing is the best way, which is what we are getting at.


Some good info from Innovate's forum.

So if you hear it w/ ears then remove 3 deg, if you hear it w/ the det cans, remove 1deg.

ROFL!!!

A rack of beer to the first paparazzi that shoots Eric driving w/ this on!!!!


Great, low-cost solution. You deserve a big cookie, too!!!!!

You can use a compression fitting instead of that rubber hose and hose clamps. 1/2" compression fitting to 3/8" NPT it looks like.

V

LOL, don't worry.. as you can see I'm very willing to post stupid pictures of myself with no outside interference

Thanks for all the feedback and ideas, there's lots of good info above. Vitor, I especially like the link to the cheap electronic box.. I think I will try something like this also. It would be good to compare the two. In fact, I think I can probably hook them both up at the same time and see which one sounds better while driving.

And yes, I could have used a compression fitting, or pipe fittings, or sweated an NPT adapter on with solder, but the piece of heater hose and the two clamps were free Redneck engineering ftw !

-Eric

I wonder if using a fluid in the hose would help at all.

No, not really. In fact it would do just the opposite. You wouldn't be able to hear much of anything. And anything you did hear would be severely distorted.

I just made up a set for $12.78!

I don't really know how well they'll work yet, but I used some 3/8" thinwall brass tubing from the hobby shop @ $2.53, $3.99 hearing protectors from Harbor Freight, 3/8" poly tubing from Menards-15ft for $2.59, a barbed poly "T", and two 90 degree 3/8" barbed end to 3/8" NPT end-about .89 cents each.

I used the 3/8" NPT tap I got for installing my MegaSquirt sensors, and tapped into the cans. The 90s point the barbed ends downward to make it a little easier to deal with the very stiff tubing. Pretty slick, and very cheap, but I have yet to see what the results will be. . .

Thad

saw this today, with an extension and a mountable probe end (its just a threaded rod, easily moddable)

http://www.harborfreight.com/cpi/ctaf/D ... mber=95653

not bad but the head phones to the box are only 11" so it would be hard to use them unless your on a dyno

Anybody try this with a microphone in the end of the tube under the hood instead of running the hose all the way to headphones? You could run a small mic wire to the car into your laptop, AND not look like a doofus!

Could record it then, too- match it up with your datalog even.

It's pretty sweet even if you look stupid, though.

HAHA Love the pic, ima make one also

just get a headphone extension =p

or learn to read. The 11" number is for the second probe. The headphone wire is obviously longer.

I made some today also but I got riped
I paid $12.87 for teh same exact ones, guess the saying is true, "Lowes blows"

Anyway, hopefully this weekend I can get some thourough testing for 93oct and 10gph 100% meth, this is on a higher CR of ~9:1.

Excellent, definetly post your results and what you think.

And FWIW, I actually prefer Lowes, they seem to have better quality and selection. I only use home depot because it's a half mile away vs 7 or 8 miles to get to Lowes. But uh, sorry about your extra three dollars

-Eric

When you guys go and buy the air line dont buy the 50ft of it for 12bucks

go to the plumbing/copper section and look where they carry clear hose and different hoses then look for 3/8th air line hose, its light orange redish
its .33cents a foot and works great. You knly need about 15ft of it.