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Chain fence eating turbo
 
Join Date: Dec 2008
Location: Austin, TX
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Det cans and helmets for racing

Been pondering this for ages. Det cans* are said to be better than electronic detonation detection equipment, reading from a bunch of tuners.

We always fear detonation, and thought how perfect it would be to use det cans during racing, so you know when to back off throttle (and possibly timing later), and to save your eardrums from your M&K Outlaw muffler.

Sure, there is J&S Safeguard and other EFI systems that use true knock sensors, but there seems be a lot of error with these systems and it is hotly debated "tuning" these is black magic. Some say it's simple, some say it takes a team of engineers to figure out the frequency band the software should be identifying detonation by. I'm neutral, just stating what I read...

Which again, leads to det cans. A lot of folks I've read claim there is no false-positives with these. When you hear "marbles in a can", it is detonation. No valvetrain noise, no piston slap, or any other mechanical sound will falsely believed to be detonation.

The problem is, how do you use a helmet with them?

Any thoughts?

Next time I get mine back together, I am tuning it with them. Next best thing to a dyno....


*Det cans are simply ear muffs with nipples threaded into each ear piece. A copper tube is rolled onto itself a few time and compressed tight as you can (vise would be best I'd imagine or a press), then a bolt hole is drilled through it. From this copper tube, you hook hoses from it to the ear muffs using a "Y" or "T" connection.

Key here is that it is AIR TIGHT.

The copper tube is then bolted to the block somewhere similar to where a knock sensor would be mounted.

When detonation occurs, the sound will travel to the ear muffs just like the principle of a stethoscope.
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Cory - '87 C3.2 (3.4, stock 3.2 heads, cams, intake, with 75mm Mustang TB) Guards/Blk - turbos new to old 1). Borg Warner S366 (66mm comp/73mm turb/0.91 T4 divided ~1.4 bar), 2). Holset HX40 8-blade (58mm/"P" trim 0.84 T4 divided 1.4 bar), 1/4 mile 12.02 @ 129 MPH (street tires), 3). Turbonetics 60-1 HiFi (60mm/"P" trim 0.81 A/R T4 open 1.2 bar), 431whp - MegaSquirt II/EDIS ignition/80lb inj
Old 10-30-2017, 01:18 PM
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Quote:
Originally Posted by Tippy View Post
Been pondering this for ages. Det cans* are said to be better than electronic detonation detection equipment, reading from a bunch of tuners.

We always fear detonation, and thought how perfect it would be to use det cans during racing, so you know when to back off throttle (and possibly timing later), and to save your eardrums from your M&K Outlaw muffler.

Sure, there is J&S Safeguard and other EFI systems that use true knock sensors, but there seems be a lot of error with these systems and it is hotly debated "tuning" these is black magic. Some say it's simple, some say it takes a team of engineers to figure out the frequency band the software should be identifying detonation by. I'm neutral, just stating what I read...

Which again, leads to det cans. A lot of folks I've read claim there is no false-positives with these. When you hear "marbles in a can", it is detonation. No valvetrain noise, no piston slap, or any other mechanical sound will falsely believed to be detonation.

The problem is, how do you use a helmet with them?

Any thoughts?

Next time I get mine back together, I am tuning it with them. Next best thing to a dyno....


*Det cans are simply ear muffs with nipples threaded into each ear piece. A copper tube is rolled onto itself a few time and compressed tight as you can (vise would be best I'd imagine or a press), then a bolt hole is drilled through it. From this copper tube, you hook hoses from it to the ear muffs using a "Y" or "T" connection.

Key here is that it is AIR TIGHT.

The copper tube is then bolted to the block somewhere similar to where a knock sensor would be mounted.

When detonation occurs, the sound will travel to the ear muffs just like the principle of a stethoscope.
With all of modern technology at your fingertips you would choose to ear trumpet knock? Seriously?
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Old 10-30-2017, 07:31 PM
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Chain fence eating turbo
 
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Quote:
Originally Posted by patina View Post
With all of modern technology at your fingertips you would choose to ear trumpet knock? Seriously?
What were you saying????:

The purpose of Det Cans

Detonation Cans, or det cans for short, are to help us hear the sound of detonation in the motor. If you don’t know what detonation sounds like, it is a “ping” sound that the motor will make that some also describe as a “knocking” sound. This is why we often call detonation pinging or knocking a motor. Det cans are earmuffs that are connected to the engine block that allow you to hear the motor better and listen for knock. While some would argue that this is the knock sensors job, most engine tuners find that once a motor has been modified, the knock sensor becomes less accurate as each knock sensor itself is tuned to match a motor set-up very precisely. As you modify the engine you run the risk of taking away the accuracy of the factory knock sensor. Many tuners have reported that knock sensor accuracy becomes considerably bad in forced induction applications where an accurate knock sensor is extremely important.

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source:

http://www.enginebasics.com/EFI%20Tuning/Det%20Cans.html
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Old 10-31-2017, 05:49 AM
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Quote:
Originally Posted by patina View Post
With all of modern technology at your fingertips you would choose to ear trumpet knock? Seriously?
Because often analog and the human interpretation of analog signals is superior to digital.

This is especially true with audible signals.
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Old 10-31-2017, 06:41 AM
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You can take a knock sensor cut the plug off the end and wire in a PC microphone input.

now plug that microphone into an ubuntu laptop with this DSP installed https://lmms.io/ (there are others)

now use head phone to listen to the knock sound And you can tune it with the DSP

Works on Dyno's

installed on something like this could be fully portable and do other functions like logging
Intel DCCP847DYE NUC Mini PC - TheBookPC.com
Old 10-31-2017, 08:31 AM
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Chain fence eating turbo
 
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Quote:
Originally Posted by Black_Hat View Post
You can take a knock sensor cut the plug off the end and wire in a PC microphone input.

now plug that microphone into an ubuntu laptop with this DSP installed https://lmms.io/ (there are others)

now use head phone to listen to the knock sound And you can tune it with the DSP

Works on Dyno's

installed on something like this could be fully portable and do other functions like logging
Intel DCCP847DYE NUC Mini PC - TheBookPC.com

Read jpnovak's post above yours.

The point is to use a far simpler, far cheaper, and better results oriented "system". False-positives (using digital equipment) results in (potentially that is......) timing pulled and loss of overall power.

The analog det cans are a win-win AFAIK, IMO.

Was thinking how neat it'd be to incorporate into a helmet det cans resulting in noise reduction AND to mainly keep an ear on detonation.
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Cory - '87 C3.2 (3.4, stock 3.2 heads, cams, intake, with 75mm Mustang TB) Guards/Blk - turbos new to old 1). Borg Warner S366 (66mm comp/73mm turb/0.91 T4 divided ~1.4 bar), 2). Holset HX40 8-blade (58mm/"P" trim 0.84 T4 divided 1.4 bar), 1/4 mile 12.02 @ 129 MPH (street tires), 3). Turbonetics 60-1 HiFi (60mm/"P" trim 0.81 A/R T4 open 1.2 bar), 431whp - MegaSquirt II/EDIS ignition/80lb inj
Old 10-31-2017, 12:33 PM
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There are examples of electronic amplification for this application. Some systems use electronic microphones rather than the tubing/hose connection.

This may be easier so that you can install a headphone or earbud under your helmet.

Many ways to make this happen.
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Old 10-31-2017, 01:18 PM
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Quote:
Originally Posted by Tippy View Post
The link definitely helped. I couldn't picture the folded end correctly.
I like it. I will probably be building a set for tuning my car next spring. Cheap and simple.
I will not be drilling holes in my new Simpson helmet. Even a cheap helmet would be a waist of money. IMO

Pictures for lazy people (Like Me) that don't follow links.


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Old 10-31-2017, 01:26 PM
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I can see this being useful for tuning, but if you're on the track and getting severe detonation then you probably need to do revisit your tune. Electronic knock control has come a long ways, and can respond much quicker than the driver. By the time you hear it on your det cans, the damage is already done.

My ms3pro knock control is set up for individual cylinder knock retard, and knock windowing. It also takes into account the bore size to determine frequency. The ecu will pull timing on the cylinder that knocks before it even fires again, and you cant feel it when its retarding timing, since its usually just 1 cylinder. Sure, maybe there are some false positives here and there, but id rather be on the conservative side and keep the motor happy. Want to know if its real knock? Throw in some 100 octane and see if it goes away.
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Old 10-31-2017, 06:11 PM
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Chain fence eating turbo
 
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The point of this thread was to show a simple, cheap way to check for detonation.

Det cans are like CIS. Simple and mechanical.

Figured since most here are CIS and not EFI, det cans would be a great way to do a sanity check for detonation.

Get the motor heat saturated and do some pulls. If no detonation, should be good to go minus getting a bad batch of fuel.

I understand how knock control works for EFI, but that wasn't the point.
Old 11-02-2017, 06:52 PM
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