Welcome to the North American Subaru Impreza Owners Club Sunday May 29, 2016
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Go Back   NASIOC > NASIOC Technical > Factory 2.5L Turbo Powertrain (EJ Series Factory 2.5L Turbo)

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads. 
Reply
 
Thread Tools Display Modes
Old 05-04-2005, 11:28 AM   #1
drfrink24
Scooby Specialist
 
Member#: 36369
Join Date: May 2003
Chapter/Region: MWSOC
Location: Rochester, MN
Vehicle:
2004 WRX STi
Java Black

Default Detonation explained with pictures

Edit: Below is the original post, however this is the common belief and actually is wrong. Please start reading at post #8 for actual information regarding the detonation process.

Quote:
Hello all, not sure if this has already been posted, but, I haven't seen it here. I think this is an excellent illustration of what pre-ignition and detonation looks like:

* Registered users of the site do not see these ads.

Last edited by 8Complex; 05-06-2005 at 09:31 AM.
drfrink24 is offline   Reply With Quote
Sponsored Links
* Registered users of the site do not see these ads.
Old 05-04-2005, 12:36 PM   #2
drdome99
Scooby Specialist
 
Member#: 56571
Join Date: Mar 2004
Chapter/Region: MAIC
Vehicle:
'05 LGT - Stage 2

Default

Is there always an audible noise with detonation? On rare occassions my CEL will flash (UTEC detecting det.) a couple times in 5th gear yet I have never once heard any type of noise or ping.
drdome99 is offline   Reply With Quote
Old 05-04-2005, 12:41 PM   #3
BigJ04STi
Scooby Specialist
 
Member#: 77239
Join Date: Dec 2004
Chapter/Region: Tri-State
Location: A Town
Vehicle:
2004 Impreza WRX
None

Default

Quote:
Originally Posted by drfrink24
Hello all, not sure if this has already been posted, but, I haven't seen it here. I think this is an excellent illustration of what pre-ignition looks like:
Just so you know... Pre-ignition and Detonation are 2 different things...

Detonation occurs after the spark, when spontaneous combustion occurs ahead of the initial combustion flame.

Pre ignition is combustion before the spark...
BigJ04STi is offline   Reply With Quote
Old 05-04-2005, 02:04 PM   #4
drfrink24
Scooby Specialist
 
Member#: 36369
Join Date: May 2003
Chapter/Region: MWSOC
Location: Rochester, MN
Vehicle:
2004 WRX STi
Java Black

Default

Quote:
Originally Posted by drdome99
Is there always an audible noise with detonation? On rare occassions my CEL will flash (UTEC detecting det.) a couple times in 5th gear yet I have never once heard any type of noise or ping.
From what I've read, yes, however, hearing/monitoring them without a device is nearly impossible in all but very bad cases.

Given the size of the combustion chamber, apparently there is a specific frequency that all detonation/pre-ignition occurs at.
drfrink24 is offline   Reply With Quote
Old 05-04-2005, 02:05 PM   #5
drfrink24
Scooby Specialist
 
Member#: 36369
Join Date: May 2003
Chapter/Region: MWSOC
Location: Rochester, MN
Vehicle:
2004 WRX STi
Java Black

Default

Quote:
Originally Posted by BigJ04STi
Just so you know... Pre-ignition and Detonation are 2 different things...

Detonation occurs after the spark, when spontaneous combustion occurs ahead of the initial combustion flame.

Pre ignition is combustion before the spark...
Corrected my original post. Sorry for the confusion.
drfrink24 is offline   Reply With Quote
Old 05-04-2005, 04:32 PM   #6
BLACK02WAGON
Scooby Specialist
 
Member#: 32574
Join Date: Feb 2003
Chapter/Region: South East
Location: North Carolina
Vehicle:
2012 Nissan GTR BE
Vibrant Red

Impreza WRX STi

Poor pictures as they should show the movement of the piston in relation to the spark and fueling. Preignition is absolute death for and engine wheras detonation in minor occurances in survivable.
BLACK02WAGON is offline   Reply With Quote
Old 05-05-2005, 04:16 AM   #7
lettucemanatee
Scooby Specialist
 
Member#: 32493
Join Date: Feb 2003
Chapter/Region: South East
Location: LSU
Vehicle:
2002 Impreza WRX
rock chipped blue

Default

that's not even a HEMI motor.
lettucemanatee is offline   Reply With Quote
Old 05-05-2005, 05:54 AM   #8
hotrod
Scooby Specialist
 
Member#: 14141
Join Date: Jan 2002
Location: [email protected] @ 5800 ft on 13T
Vehicle:
2002 Impreza WRX

Default

The illustrations are of questionable value as they perpetuate some bad information. The collision of the flame fronts does not occur and has nothing to do with either detonation or pre-igntion. This was proven some 70 odd years ago. If you have multiple sources of ignition the flame fronts will move past and through each other as if the second flame front did not exist.

The actual process of detonation actually occurs in the partially burned gases behind the flame front. The flame takes time to consume all the fuel and oxygen present and the combustion process continues for some period of time after the initial flame front passes a location in the combustion chamber. Detonation is the result of a nearly explosive reaction (combustion occuring faster than the speed of sound) where the burning process transitions from a smooth burning process to a point source of very rapid pressure and temperature rise where all the remaining fuel energy is released in a couple milliseconds.

The result is a sharp shock/pressure wave that is several times stronger than normal combustion pressures.

The first illustration is accurate, the second on pre-ignition is accurate except the comment about colliding flame fronts, the third on detonation is basically the prevailing view on detonation in the late 1920's and 1930's.

Larry
hotrod is offline   Reply With Quote
Old 05-05-2005, 06:59 AM   #9
SaabTuner
Scooby Specialist
 
Member#: 67608
Join Date: Aug 2004
Location: SoCal
Default

One of, what I (and I think Larry too since he showed it to me) consider to be the pivotal documents on the matter was published by NACA back in the 40's. Here's a link: http://naca.larc.nasa.gov/reports/1948/naca-report-912/

And that has ACTUAL pictures of both detonation (well, the result of detonation to the combustion process, it happens too fast even for their camera) and pre-ignition in a real running cyllinder, which, as the paper showed, turned out to be totally seperate processes.

The camera NACA (aka the old name for NASA for n00bs) had to use to discover the difference between detonation and pre-ignition took 40,000 frames per second. Very impressive for 1948!!

Adrian~
SaabTuner is offline   Reply With Quote
Old 05-05-2005, 09:16 AM   #10
8Complex

Moderator
 
Member#: 922
Join Date: Feb 2000
Chapter/Region: MWSOC
Location: Schaumburg, IL
Vehicle:
16 WRX (white)
04 FXT (red)

Default

Quote:
Originally Posted by SaabTuner
One of, what I (and I think Larry too since he showed it to me) consider to be the pivotal documents on the matter was published by NACA back in the 40's. Here's a link: http://naca.larc.nasa.gov/reports/1948/naca-report-912/
AWESOME link!
8Complex is offline   Reply With Quote
Old 05-05-2005, 10:27 AM   #11
drfrink24
Scooby Specialist
 
Member#: 36369
Join Date: May 2003
Chapter/Region: MWSOC
Location: Rochester, MN
Vehicle:
2004 WRX STi
Java Black

Default

Since my attempt at enlightening some people here pretty much sucked, I would advise this thread be deleted, before too many people have seen the poor pictures.

Amazing that a website, with a reprint and multiple paragraphs of details could be so dead wrong. Goes to show you can't always trust what you read.

It was all in good intentions though, not trying to mislead or misinform anyone.
drfrink24 is offline   Reply With Quote
Old 05-05-2005, 10:43 AM   #12
SaabTuner
Scooby Specialist
 
Member#: 67608
Join Date: Aug 2004
Location: SoCal
Default

Quote:
Originally Posted by drfrink24
Since my attempt at enlightening some people here pretty much sucked, I would advise this thread be deleted, before too many people have seen the poor pictures.

Amazing that a website, with a reprint and multiple paragraphs of details could be so dead wrong. Goes to show you can't always trust what you read.

It was all in good intentions though, not trying to mislead or misinform anyone.
Don't feel bad. You won't find that NACA info on the Society of Automotive Engineers webpage, and several documents I've read published recently by Mitsubishi and other car makers still perpetuate incorrect information. Very very few people know of NACA's engine research ... and it was damn good research too.

In fact, almost of your college level engineering courses also still perpetuate the wrong information and people believe it because they think it's "newer" than NACA's 1947 experiments ... if they even know of the experiments. (Usually they just haven't heard of them.) They just don't realize that the incorrect theory has its roots in the 1920's.

Much of the problem, IMHO, is that this information may have at one time been classified as it was published so soon after WWII, and still before the jet-engine era. NACA's name was probably changed to NASA before it was either declassified, or well known-of. NACA was also more well known for its developments into aerodynamics, not internal combustion engines. Plenty of SAE references to the NACA airfoil shapes, but not one single reference that I could find to the NACA engine research. Which is a shame since it's exactly the sort of thing they SHOULD be looking for ...

People will catch on ... eventually ... in the mean time you can just feel a little snobby with the understanding that you have some rather esoteric knowledge of knock and pre-ignition. heh heh heh

Adrian~
SaabTuner is offline   Reply With Quote
Old 05-05-2005, 02:36 PM   #13
Jon [in CT]
*** Banned ***
 
Member#: 2992
Join Date: Nov 2000
Chapter/Region: NESIC
Location: Connecticut, USA
Vehicle:
02 WRX Sedan
Silver

Default

Quote:
Originally Posted by hotrod
The actual process of detonation actually occurs in the partially burned gases behind the flame front.
Everything I've read on spark knock says it begins in the endgas, ahead of the flame front. I think you need to provide a reference.

BTW, my favorite description of detonation for the layman is at:
http://www.factorypipe.com/Technical...Deto/deto.html

Last edited by Jon [in CT]; 05-05-2005 at 02:51 PM.
Jon [in CT] is offline   Reply With Quote
Old 05-05-2005, 08:40 PM   #14
SaabTuner
Scooby Specialist
 
Member#: 67608
Join Date: Aug 2004
Location: SoCal
Default

Quote:
Originally Posted by Jon [in CT]
Everything I've read on spark knock says it begins in the endgas, ahead of the flame front. I think you need to provide a reference.
Maybe you should have read the NACA link. It shows clearly with photographs that the knocking reaction moves outward from behind the flame front demolishing it and pushing it outwards as it does.

Hard to beat photographs of the actual process ...

Adrian~

p.s. Jon, the link you showed is another one based on even older research than the NACA paper and has been repeatedly proven false. The NACA 912 report was not the only report done on the matter, and all reached the same conclusion. Detonation is not spontaneous ignition of the end gas, and the detonation reaction occurs behind the flame front.

Last edited by SaabTuner; 05-05-2005 at 08:46 PM.
SaabTuner is offline   Reply With Quote
Old 05-05-2005, 09:08 PM   #15
SaabTuner
Scooby Specialist
 
Member#: 67608
Join Date: Aug 2004
Location: SoCal
Default

So maybe not everyone reading the thread wants to read the whoooole link.

Here's the Schliren images for the part of the report showing that the detonation reaction occurs behind the flame front. The combustion was initiated by four spark plugs and in the early images you can see the flame waves slowly moving away from the plugs.

A key thing to note is that, between any two consecutive frames without a detonation reaction or pre-ignition, the difference between the two frames is very very small. Detonation can be characterized by a sudden change in a particular image which does not flow with the rest of the normal process.

I put two red arrows pointing to the key parts in the two images between which the detonation reaction started. Notice the small part of the flame-wave approaching the end-gas, which is now to the right of it surrounded by flame waves from the 4 spark plugs. Notice that, in the frame after the small part has been eliminated, the rest of the flame fronts are obliterated by the knock reaction.

Because neither the end gas, nor the flame fronts on the right side of the image are yet affected by the knock reaction at the time the small portion of flame front on the left hand side of the end gas is eliminated, it can be inferred that the knock reaction went from left to right in the cyllinder and originated behind the flame front, not in the end gas.



I hope this clears up things. For more info consider reading the entire link that was posted. If you search the NACA home page for knock you'll find more similar reports. There's also a lot on water injection.

Adrian~

p.s. Sorry for the size of the image; it was necessary for clarity.

p.p.s. Sorry for the weird dialog in the middle of the captured image. I just realized it was there and I'm too lazy to fix it since it's not over the frames I'm interested in. If you want to see the image without it, just go to the link.
SaabTuner is offline   Reply With Quote
Old 05-06-2005, 03:19 AM   #16
JScoob
Scooby Newbie
 
Member#: 48163
Join Date: Nov 2003
Location: socal
Vehicle:
2003 wrx

Default

Those actual frames of detonation are pretty damn cool. But...If det is caused by the mixture trailing the flame front, shouldn't a stoich or higher mixture leave nothing left to combust? Where is the det getting its "fuel" from? Logically, since det can happen at stoich, there must always be some fuel trailing the flame front...
JScoob is offline   Reply With Quote
Old 05-06-2005, 03:39 AM   #17
SaabTuner
Scooby Specialist
 
Member#: 67608
Join Date: Aug 2004
Location: SoCal
Default

Quote:
Originally Posted by JScoob
Those actual frames of detonation are pretty damn cool. But...If det is caused by the mixture trailing the flame front, shouldn't a stoich or higher mixture leave nothing left to combust? Where is the det getting its "fuel" from? Logically, since det can happen at stoich, there must always be some fuel trailing the flame front...
Combustion is far from "done" after the flame front. Many reactions, such as the oxidation of NO and CO into NO2 and CO2, take much longer to complete. While I don't actually know what chemical reaction is responsible for detonation, I highly suspect that, when there is a surplus of unburnt hydrogen in the presence of CO before it is oxidized to CO2, some of the hydrogen steals the oxygen from the carbon monoxide to form H2O, and in the intermediate OH-. The reaction CO + 2H = H2O + C should be exothermic, and, since the combustibles are already mixed, as soon as the right temperature was reached, they would combust all at once.

But, that's only a theory, and there may be a better one I'm unaware of.

You're right about richer mixtures actually being more likely to detonate. That may sound totally ludicrous, but the only reason it doesn't normally work out that way is because the richer mixture lowers the combustion temperatures enough to make up for that.

That's actually one of the reasons water injection does better than a rich mixture in most cases. They both cool the combustion process, but the water doesn't exacerbate the condition which allows detonation to happen in the first place, an incompleted combustion after the flame-wave.

Just more to think about ...

Adrian~
SaabTuner is offline   Reply With Quote
Old 05-06-2005, 05:21 AM   #18
JScoob
Scooby Newbie
 
Member#: 48163
Join Date: Nov 2003
Location: socal
Vehicle:
2003 wrx

Default

I wonder if there must be something other than fuel that is combusting - if det is so much faster and explosive than the flame front, that leads me to believe that det is an entirely different chemical reaction. Fuel may be an ingredient, but there must be others, perhaps a catalyst that causes it to be so much more violent. But certainly fuel must be part of the equation, otherwise high octane fuels would have no effect. I wonder if the by-product of high octane fuel is what suppresses det and not the pre-burnt fuel itself...
JScoob is offline   Reply With Quote
Old 05-06-2005, 08:12 AM   #19
SaabTuner
Scooby Specialist
 
Member#: 67608
Join Date: Aug 2004
Location: SoCal
Default

It's not "fuel" literally that I suspect as the source reaction for detonation. Rather, I suspect intermediate products of the combustion process, some of which have considerably faster reaction rates at combustion temperatures.

One of the other reasons detonation is faster than normal combustion, and even auto-ignition, is that it is spread by a pressure/shock wave, rather than a flame-wave.

Technically, as I understand it, detonation is an explosion, rather than a combustion, because of the method through which it propogates. (IE pressure/shock instead of flame/heat)

Anyway, more research needs to be done. But, because so few people understand that detonation is NOT pre-ignition, the research doesn't appear to be taking place ... yet.

Adrian~
SaabTuner is offline   Reply With Quote
Old 05-06-2005, 02:47 PM   #20
Tgui
Scooby Specialist
 
Member#: 44771
Join Date: Oct 2003
Default

Thanks so much for all this info.

I've nothing of value to add to this thread.
Tgui is offline   Reply With Quote
Old 05-06-2005, 03:18 PM   #21
Depeche
Scooby Newbie
 
Member#: 33650
Join Date: Mar 2003
Chapter/Region: MWSOC
Location: Lake County
Vehicle:
3005 Ford
Thundercougarfalconbird

Default

awesome thread!
Depeche is offline   Reply With Quote
Old 05-07-2005, 01:25 PM   #22
bboy
Scooby Specialist
 
Member#: 56468
Join Date: Mar 2004
Chapter/Region: NWIC
Location: Seattle, WA
Vehicle:
04 Improved STI
Dirty White

Default

My $0.02. I've been in one of these threads before. For what its worth I'd like to re-word something that hotrod and Saab_Tuner said about "behind the flame front......".

Detonation is an explosive reaction concurrent or after combustive burning has begun. Burning is a linear progression, like a fuse, it starts at one end (spark) and burns to the other (radially in a cylinder). The main point here is normal combustion is an orderly chemical reaction. When detonating, it's as if you lit multiple fuses, each with their own flame front. They are not all lit at exactly the same time, many will coincide with the spark, but some will be later. In chemical parlance, detonation is a "multi-nucleate" event, like bubble formation in boiling water.

You can see the multi-nucleations in the NACA pictures.

In the first picture of this thread are both "pre-ignition" cartoons where a second nucleation event is unconnected to the spark, and, it would seem, while the piston is traveling up toward TDC.

Another way to look at detonation/knock is that it depends on the sparkplug/spark. If there is no plug, or you uncap the plug, there is no detonation. Pre-ignition is a spark independent event, much like a Diesel reaction.
bboy is offline   Reply With Quote
Old 05-07-2005, 01:31 PM   #23
santofontana
Scooby Specialist
 
Member#: 26876
Join Date: Oct 2002
Chapter/Region: NESIC
Location: 1990 GMC Sierra 4x4 350ci
Vehicle:
1994 Camaro Z28 383
Black M6

Default

Question for the experts; whats the deal with cars with two plugs per cyl? I used to have a Nissan 200sx that had this. It seems like it would increase the chances of det? Or do they fire at different times?
santofontana is offline   Reply With Quote
Old 05-07-2005, 02:10 PM   #24
SaabTuner
Scooby Specialist
 
Member#: 67608
Join Date: Aug 2004
Location: SoCal
Default

Quote:
Originally Posted by santofontana
Question for the experts; whats the deal with cars with two plugs per cyl? I used to have a Nissan 200sx that had this. It seems like it would increase the chances of det? Or do they fire at different times?
Firing two plugs instead of one speeds up how quickly the combustion process progresses. Since less timing is required with twin-plug ignition systems, the peak pressure is usually less and that lowers the chances for detonation.

You get a similar effect with quench pads, which also speed up the combustion process.

A faster combustion process puts more pressure where it is usefull, after top dead center, so that you don't need as much pressure to do the same amount of work.

Adrian~
SaabTuner is offline   Reply With Quote
Old 05-09-2005, 07:22 PM   #25
Jon [in CT]
*** Banned ***
 
Member#: 2992
Join Date: Nov 2000
Chapter/Region: NESIC
Location: Connecticut, USA
Vehicle:
02 WRX Sedan
Silver

Default

Quote:
Originally Posted by SaabTuner
Maybe you should have read the NACA link. It shows clearly with photographs that the knocking reaction moves outward from behind the flame front demolishing it and pushing it outwards as it does.

Hard to beat photographs of the actual process ...

Adrian~

p.s. Jon, the link you showed is another one based on even older research than the NACA paper and has been repeatedly proven false. The NACA 912 report was not the only report done on the matter, and all reached the same conclusion. Detonation is not spontaneous ignition of the end gas, and the detonation reaction occurs behind the flame front.
Sigh. Got any evidence from the last 60 years?

From John B. Heywood, Internal Combustion Engine Fundamentals, Intl. Ed., 1988:
Quote:
9.6.2 Knock Fundamentals

As yet, there is no complete fundmental explanation of the knock phenomenon over the full range of engine conditions at which it occurs. It is generally agreed that knock originates in the extremely rapid release of much of the energy contained in the end-gas ahead of the propagating turbulent flame, resulting in high local pressures. The nonuniform nature of this pressure distribution causes pressure waves or shock waves to propagate across the chamber, which may cause the chamber to resonate at its natural frequency. Two theories have been advanced to explain the origin of knock: the autoignition theory and the detonation theory. The former holds that when the fuel-air mixture in the end-gas is compressed to sufficiently high pressures and temperatures, the fuel oxidation process -- starting with the preflame chemistry and ending with rapid energy release -- can occur spontaneously in parts or all of the end-gas region. The latter theory postualtes that, under knocking conditions, the advancing flame front accelerates to sonic velocity and consumes the end-gas at a rate much faster than would occur with normal flame speeds. These theories attempt to describe what causes the rapid release of chemical energy in the end-gas which creates very high pressures, locally, in the end-gas region. The engine phenomenon "knock" includes also the propagation of strong pressure waves across the chamber, chamber resonance, and transmission of sound through the engine structure. The detonation theory has led many to call knock "detonation." However, the more general term "knock" is preferred, since this engine phenomenon includes more than the end-gas energy release, and there is much less evidence to support the detonation theory than the autoignition theory as the initiating process. Most recent evidence indicates that knock originates with the spontaneous or autoignition of one or more local regions within the end-gas. Additional regions (some adjacent to already ignited regions and some separated from these regions) then ignite until the end-gas is essentially fully reacted. This sequence of processes can occur extremely rapidly. Thus, the autoignition theory is most widely accepted.
From Richard Stone, Introduction to Internal Combustion Engines, 3rd ed., 1999:
Quote:
The flame front propagates away from the sparking plug, and the unburnt (or 'end') gas is heated by radiation from the flame front and compressed as a result of combustion processes. If spontaneous ignition of the unburnt gas occurs, there is a rapid pressure rise which can be characterised by a 'knocking'.
From Richard van Basshuysen and Fred Schäfer, Hanbuch Verbrennungsmotor (Internal Combustion Engine Handbook), 2002:
Quote:
14.2.3.4 Engine Knock

During normal combustion relatively "gently pressure curves" with maximum pressure increase rates of approximated 2 bar/KW are to be observed. By comparison, sharp pressure fluctuations occur in the air-fuel mixture during knocking combustion that can be explained by the following process. After initiation of the combustion by the ignition sparks, the unburned residual mixture is further compressed by the propagating flame front and, hence, additionally heated up. If the ignition limit is exceed in the process, then a spontaneous autoignition takes place in the remaining mixture. This practically isochoric residual gas combustion results in steep pressure gradients that spread in the form of pressure waves in the combustion chamber, causing the familiar knocking or ringing noise.
Below is some of the research available online. I've chosen to cite only reports which contain combustion images, knowing how much faith SaabTuner places in pictures.
The 1985 paper at http://powerlab.mech.okayama-u.ac.jp...1/C85_P259.pdf says:
Quote:
Although for many years there was much disagreement as to the nature of this mechanism, it is now commonly accepted that end-gas autoignition is responsible for the accelerated heat release rate that leads to knock.
The 1991 paper at http://www.mech.nitech.ac.jp/~thermal3/Identify.pdf says:
Quote:
Engine knock is due to the autoignition of the low-temperature charge ahead of the normally propagating flame front.
The 1995 report at http://www.marubun.co.jp/laser/lambda_pdf/no46.pdf says:
Quote:
Looking from a chemist's point of view, the fundamental understanding of the chemical process has been achieved. Nevertheless, detailed understanding of the mechanisms leading to knock is still being worked on, i.e., so far it is not known whether inhomogeneities in temperature or species distribution lead to exothermic centers (hot spots) which on their part initiate knocking combustion.

The evolution of combustion in a knocking engine cycle is shown schematically in fig. 1. The black circle represents a combustion chamber filled with fuel/air mixture. After the charge is ignited (here near the wall; red spark) a flame front develops and travels through the combustion chamber (direction of the arrow). Finally, the compression by the burnt gasses leads to formation of hot spots within the unburnt end gas region. These hot spots locally initiate the autoignition process of the end gas.
The 2004 paper at http://powerlab.mech.okayama-u.ac.jp...4/C4_3_073.pdf says:
Quote:
In spark ignition engines, knock can be defined as self-ignition of a certain portion of the unburned gas beyond the flame front. This abnormal combustion releases a chemical energy that excites within the cylinder volume pressure oscillations that are responsible of engine noise and sometimes damage.
That last paper should be especially interesting to SaabTuner because it also looks at ion current knock detection.

It's interesting to note: the more recent the research, the less doubt expressed about whether knock is due to end-gas autoignition ahead of the flame front.

Last edited by Jon [in CT]; 05-09-2005 at 07:34 PM.
Jon [in CT] is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Explain this picture MPRZIV Off-Topic 19 10-29-2009 08:21 PM
OT Aviators: Explain this picture to me... MattDell Off-Topic 24 08-28-2008 07:00 AM
Can someone explain this picture? CrazyMike13 Off-Topic 12 02-02-2005 01:46 AM
Detonation Explained - Cliff Notes Version projectmp Engine Management & Tuning 3 03-16-2004 07:47 PM
Can anybody explain this picture STi-Nane Off-Topic 27 03-03-2003 09:23 PM

All times are GMT -4. The time now is 04:45 AM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2016, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2016 Axivo Inc.
Copyright ©1999 - 2016, North American Subaru Impreza Owners Club, Inc.