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Old 07-14-2006, 12:53 AM   #1 (permalink)
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Default "knock retard" - definition? ideology?

on the areoforce guage there is a setting to monitor you "knock retard"

my buddy has his set on "timing" and "knock retard" to view them, but the value of "knock retard" thats shown is what?

is it the amount of timing being pulled because of knock to create zero knock?
or is it just a value and i shouldnt pay much attention to it, and pay most attention to my timing and make sure it doesnt make a dramatic dip ?

can anyone define a dramatic dip in timing? what would be a dramatic dip?

if "knock retard" is more important, then what is ideal "knock retard" on my buddies stock turbo car there is around 6 "knock retard" but what does that mean???

thanks
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Old 07-14-2006, 01:03 AM   #2 (permalink)
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ok ... so the way im understanding jsut to clarify for soem because i can see how it could eb confusing

"timing advance" is in timing degree's

"knock retard" is a voltage value NOT in degree's

for example if timing is 27 - 28 and knock retard is 6, that doesnt mean that it pulled 6 degree's of timing because of knock correct?? it just means that the sensor has senced some engine noise but not enough to pull timing, i guess what im wondering is what is the threshold for the pcm to pull timing down, in respect of the value of "knock retard"
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Old 07-14-2006, 01:13 AM   #3 (permalink)
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Quote: Originally Posted by Lagzilla
ok ... so the way im understanding jsut to clarify for soem because i can see how it could eb confusing

"timing advance" is in timing degree's

"knock retard" is a voltage value NOT in degree's

for example if timing is 27 - 28 and knock retard is 6, that doesnt mean that it pulled 6 degree's of timing because of knock correct?? it just means that the sensor has senced some engine noise but not enough to pull timing, i guess what im wondering is what is the threshold for the pcm to pull timing down, in respect of the value of "knock retard"

I believe KR is used to measure the number of degrees of overall timing advance that needs to be removed to prevent detonation from continuing, which will protect the engine from dying.
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Old 07-14-2006, 01:20 AM   #4 (permalink)
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I've also read that you lose about 2hp per degree of timing retard. I'm not an expert just going by things I've read on the Internet! My personal experience is that with 4 to 9 degrees of KR on my Techgauges I couldn't feel any power loss and my dyno graph was smooth without any major dips or drastic fluctuations.
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Old 07-14-2006, 03:19 AM   #5 (permalink)
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Ignition Advance what's the number suppose to be +/-

Will vary between 0-50, depending on rpm and engine load. This is most useful to look at under WOT, which for a stock car is around 30-35 deg. if I remember correctly (mine’s not stock anymore). Monitoring this will tell you if timing is being pulled, and allow you to compare values between tunes when they become available for these cars.

Knock Retard what's the number suppose to be +/-

Should be close to zero. When the PCM detects detonation or knock, it will pull timing to eliminate it. This value represents how much timing is being pulled. Getting more the 3-4 degrees would tell me to back of the boost, add octane, of reduce the WOT timing advance (if possible).
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Old 07-14-2006, 03:46 AM   #6 (permalink)
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I haven't looked at the specs for the couple gauges that are now on the market, but I know that at least one of them doesn't show knock retard in degrees. From the sounds of it the Aeroforce may not do this and I'm not sure if they're just showing the voltage of the knock sensor and providing a cleaner display of it (of possibly using their own algorithm to compute whether it's knocking) or they're trying to show timing retard in degrees.

Basically the optimal thing to monitor would be the knock retard in degrees. You can also watch the timing advance if you know what you're looking for, but because the PCM is always altering advance it's hard to say what the optimal or max advance will be. This problem is compounded when you introduce a piggyback or other device like a MAP clamp that affects the inputs of the PCM, which in turn changes what the PCM does with timing advance. So while I might know what the timing curve looks like on an optimally running stock or S1/S2/S3 car on a WOT pull through the gears, using a piggyback or similar item can change that curve.

With a factory DRB-III scan tool and some of the high end aftermarket units you have access to a lot of specific Chrysler protocols in addition to the basic, generic OBD-II information. That includes knock voltage, whether the PCM has determined there is knock (under some conditions you might get noise/knock volts and the PCM is smart enough to filter that out), overall timing advance, knock (timing) retard, and so on. The most powerful one to tune with is going to be knock retard in degrees. You don't have to worry about trying to backwards compute knock degrees from overall advance (nearly impossible to do with great accuracy) and you will be able to see if the PCM is unhappy and pulling/reducing timing for any reason. It is still very important to watch overall timing advance, and you do so to make sure you're not running 35+ on a big turbo at the top end. You might not get major knock doing that depending on fuel and other variables, but seeing that much advance should raise a flag that you're really pushing it.
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Old 07-14-2006, 08:32 AM   #7 (permalink)
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so what is ideal knock retard and timing advance for say a big turbo car?
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Old 07-14-2006, 08:40 AM   #8 (permalink)
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Not to rain on the aeroforce gauge, cause its an awesome gauge, but I asked this same question to the Tech Gauge guy and got a response that told me the Tech Gauge was showing degrees of timing retarded due to knock.

We 'think' we verified this with a w/i kit... s2 with toys and exhaust... Obviously on pump it would not hold hom for more than a second or two, and we had anywhere from 6-9 degrees of knock retard with timing at redline around the mid to low 20's.... Installed w/i and the count went down to .5, and timing advanced up to 35 degrees at redline.

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Old 07-14-2006, 11:17 AM   #9 (permalink)
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ok, so what your saying is that mopar programed HOM to fall out above 5 KR value shown on the tech guage aeroforce sells,

do you think that 5 is the amount of knock in degree's seen?
or do you believe that 5 is just a voltage value determined by the guage.

is the 5 is in degree's of knock, if in degree's of knock 5 degree's of knock is allot to me. i dont think a manufacture would allow anything more than 2.5 degree's of knock before timing is pulled.

vs

is 5 degree's pulled in order to retain a zero Knock in degree's, that it is the amount of timing degree's lowered from the level of "timing advance" to retain zero Knock in degree's.

vs

5 as a voltage value not knock in degree's or timing being pulled, just a value the sensor is seing in relation to knock, not necessarily saying that your car is knocking 5 degree's, or that timing is being pulled 5 degree's to retain zero knock in degree's, but that because the pcm is constantly trying to advance timing the KR value at the timing advance value is sensing (for example) 5 points of KR. it doesnt mean that it is too much its just letting you know that your value is this much. is there a maximum value we should stay away from? what is ideal value seen. if this 3rd statment is true im assuming since u said that with 5 or lower value it held HOM, sounds like 5 is the threashold others without the "kick out of agresive tune" feature should stick to


thanks
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Last edited by Lagzilla; 07-14-2006 at 11:26 AM.
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Old 07-14-2006, 12:41 PM   #10 (permalink)
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Quote: Originally Posted by Lagzilla
ok, so what your saying is that mopar programed HOM to fall out above 5 KR value shown on the tech guage aeroforce sells,

First, I was talking about the Tech Gauge, sold by Tech Gauges. NOT the aeroforce gauge.
Secondly, I don't know how Mopar programed HOM... I just know what we saw on a s2 with toys and exhaust car. I wish I could tell you more, but its all speculation and observation of ONE car... Not enough to base fact on.
Quote: Originally Posted by Lagzilla
do you think that 5 is the amount of knock in degree's seen?
or do you believe that 5 is just a voltage value determined by the guage.

Personaly, I believe its a voltage value... HOWEVER, the head guy at Tech Gauges told me its actually degrees of timing being pulled DUE to knock. So a five value is five degrees of timing retarded due to knock. You might PM PitViper... He worked with the Tech Gauge crew to develop the Tech Gauges... He may be able to tell you more about it.

Quote: Originally Posted by Lagzilla
is the 5 is in degree's of knock, if in degree's of knock 5 degree's of knock is allot to me. i dont think a manufacture would allow anything more than 2.5 degree's of knock before timing is pulled.

The SRT4 runs SO much timing under boost, the NGC MUST take care of itself. It probably pulls back way too much at first, then adds timing back in until knock is encountered again. It probably does that to simply protect the engine. Think of it as a child touching a hot pan... The child doesnt have to YANK its hand away from the pan, but it does. The NGC probably doesn't have to pull 5 degrees of timing, but it does to stay safe. Again, that is my OPINION... Dont take my word for it.

Plus, I think your getting some things confused... You don't see 2.5 degree's of knock... You are seeing 2.5 degrees of timing being reduced DUE TO detonation (knock).

Quote: Originally Posted by Lagzilla
is 5 degree's pulled in order to retain a zero Knock in degree's, that it is the amount of timing degree's lowered from the level of "timing advance" to retain zero Knock in degree's.

Thats the way the head guy at Tech Gauges explained it to me.

Quote: Originally Posted by Lagzilla
5 as a voltage value not knock in degree's or timing being pulled, just a value the sensor is seing in relation to knock, not necessarily saying that your car is knocking 5 degree's, or that timing is being pulled 5 degree's to retain zero knock in degree's, but that because the pcm is constantly trying to advance timing the KR value at the timing advance value is sensing (for example) 5 points of KR. it doesnt mean that it is too much its just letting you know that your value is this much.

When the aeroforce gauge came out, and several people were testers for it, that was the idea. It just assigned a value to knock based off the voltage of the knock sensor. Obviously higher values meant more knock. The guys at tech gauges tell me their gauge measure the amount of timing being retarded due to knock.

Quote: Originally Posted by Lagzilla
is there a maximum value we should stay away from? what is ideal value seen. if this 3rd statment is true im assuming since u said that with 5 or lower value it held HOM, sounds like 5 is the threashold others without the "kick out of agresive tune" feature should stick to

I don't know about maximum values... Id try to keep it as close to zero as possible.

Yeah, it sounds like 5 is the threashold for hom on s2 with just exhaust. But that is NOT fact.. That is an observation we made on ONE car...

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Old 07-14-2006, 12:46 PM   #11 (permalink)
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thanks TJ for more tuning Guru's input
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Old 07-14-2006, 01:15 PM   #12 (permalink)
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TJ is very spot on with his evaluation. I have a decent amount of experience with the Aeroforce tech gauge (I bought one in the first ever group buy, they were originally produced for the grand prix)...Knock retard is just a measurement that is showing how many degrees of timing is being pulled because of detonation. As far as I know, there isn't a real measurement for knock...the knock sensors just know when they see a small ping or a big ping.

The level of ideal knock retard is always going to be 0 (for safety and longevity of the engine at least...), some of the grand prix guys made their fastest times with 3-5* of knock retard (including myself), but I feel that losing a tenth in the quarter mile is worth it because you are making the engine more reliable.

Hope that helps just a little bit...gotta go run to the bank to go get a cashiers check for a certain car...but if you have any more questions, just ask..and I'll try to answer if I can.

edit - oh, I forgot to mention this.

Knock Retard in a certain level can't be labeled as dangerous or safe per se, because if you have 3* of knock retard on stock timing advance and boost levels, there isn't as much danger as if you've added say 5 degrees of timing advance, and 4 more psi of boost. This is because timing advance adds extra cylinder pressure, and boost also adds more cylinder pressure, as well as higher compression ratio (this is why lower compression can run more boost)...but if you're running a lot of boost and timing, and get a hard ping, it's going to do a lot more damage to the piston than a ping of the same level, but with less cylinder pressure. It's like hitting the piston with a 30 pound sledge hammer compared to a 20 pound sledge hammer (those numbers were all completely made up by the way, just hypothetical.)

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Old 07-15-2006, 08:22 AM   #13 (permalink)
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Our gauges show knock retard in degrees. It indicates how many degrees of advance are being removed due to the presence of detonation sensed by the knock sensor. This is a very valuable parameter to monitor, as much so as A/F ratio if not more.

Zero knock retard is ideal but not always realistic. My rule of thumb has been to keep it at 3 or below, some say 5 is ok. Any more than that and I'd take steps to reduce it.

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Old 07-15-2006, 11:24 AM   #14 (permalink)
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thanks =] i purchased your gauge the blakc black red display =]
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Old 07-17-2006, 09:15 AM   #15 (permalink)
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Quote: Originally Posted by forcefedjunkie
Our gauges show knock retard in degrees. It indicates how many degrees of advance are being removed due to the presence of detonation sensed by the knock sensor. This is a very valuable parameter to monitor, as much so as A/F ratio if not more.

Todd

This is good news to know! Both top notch gauges show actual knock retard, not just a value assigned to the knock sensor.



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