"knock retard" - definition? ideology?

[Lagzilla]

ok. then i have a few other question.

how much knock in degree's will it take until the computer will start to retard timing,

once its retarded some, what is the level of knock in degree's that the pcm will stop retarding timming?

if the pcm pulls timing enough to establish zero knock in degree's, whats so bad about having 5 or even 10 degree's pulled in order to have NO KNOCK? if there is no knock then there is no knock. id say thats a pretty great way to safe guard the tune.

what is the limit the pcm can retard. is it 5? 10 ? even 15? (assuming that the pcm will do wats needed to establish zero knock)

[blackbird_R/T]

The timing gets retarded because of knock. Depending on the algorithm used the PCM will continued to pull timing until knock stops, and it then may slowly feed advance back in if it detects no knock for a certain amount of revolutions. Also if there's heavy knock it can make long term timing changes where it won't run as much total advance to start with, but you wouldn't see that unless you also monitor what the timing advance is doing in addition to knock retard.

How much depends on the severity. A few degrees may be normal depending on the fuel you run and operating conditions (hot weather, etc.). Double-digit retard and generally bad things are going on in the combustion chamber. But I'd bet some of the big turbo guys trying to use a piggyback will also see some larger knock retard numbers as well when the PCM is trying to run a ton of advance but the fuel can't support it.

[Lagzilla]

well i am monitoring my timing and knock retard with the aero force guage

(BTW AWSOME MOD!!!! JUST AS USEFULL AS MY WIDEBAND)

the knock retard on both a big turbo car and ported stock turbo (only comparisons so far) are similar ... in the 5-7 range, timing is slightly lower on teh stock turbo car for some reason mb because its got higher compresion pistons. ha probably.

if timing is retarded as soon as it senses knock i dont see that as a bad thing i see it as a safe guard , its alwasy going to do that even if your tune is the safest ever, because the pcm is constantly trying to advance timing.

so how much can the pcm retard? max before it will stop retarding and , that point from what i understand is the threashold you want to stay way away from

[blackbird_R/T]

It can get down into single digit overall advance which is a worst case, can't do anything more scenario. And pulling timing is a good thing for safety. But if you can diagnose why it's doing it and correct that deficiency you should make more power. That's where the gauge can keep you in the loop. Combining wideband, knock/timing, and maybe EGT and other OBD-II data can be a very powerful tuning aid.

[Lagzilla]

so if there is say 7 deg of knock retard that doesnt mean its dangerous, it just means you could do things to gain your timing back

for lets say us big turbo guys the less timing and more boost will yeild more power compaired to stock turbo.

so if we are running 20 psi on pump and pulling 6 deg of knock retard

that is still safe correct? because there is no knock.

even more so if there is 9 deg of knock retard, that is still "safe" because its doing its job in order to eliminate knock, and still making more hp then if oen were to pull boost down to say 17 psi and run more timing.

the ideal way to run would have much higher octain to allow the computer to give you the extra timing + the amount of boost you want.

again, deg of timing retard is not dangerous but is not ideal?

[dansrt4]

Lagzilla if you want ANYBODY to answer your questions its Blackbirdrt. If he didnt like cars so much i belive he would be a NASA tech.

[Lagzilla]

ya dan this guy knows his stuff, i jsut hope its all accurate

[dansrt4]

He has been around turbo dodge's for a long time i would trust him with my car if that helps you any.

[reed32]

Quote: Originally Posted by dansrt4

He has been around turbo dodge's for a long time i would trust him with my car if that helps you any.

im with dan on that note.

[BlatallicSRT]

I always read Blackbirds posts....this is one of the few guys that ALWAYS gives vaulable info...even though at time I dont understand it, but it good to read and learn and try to understand....Steven its good that your posting all thiese questions because I was wondering the same thing too...even though I probably read all this like 4 times to really grasp a good understanding...I have the same gauge as you and hell yes, its as useful as my wideband!!!! Im waitin on pit to chime it too...he is another that know his stuff

[dansrt4]

pit viper and tex also are pimps did vector jump in here yet? If not he will cause he will catch his name in a search now hahaha

[Lagzilla]

...bump for some one to answer this

Quote: Originally Posted by Lagzilla

so if there is say 7 deg of knock retard that doesnt mean its dangerous, it just means you could do things to gain your timing back

for lets say us big turbo guys the less timing and more boost will yeild more power compaired to stock turbo.

so if we are running 20 psi on pump and pulling 6 deg of knock retard

that is still safe correct? because there is no knock.

even more so if there is 9 deg of knock retard, that is still "safe" because its doing its job in order to eliminate knock, and still making more hp then if oen were to pull boost down to say 17 psi and run more timing.

the ideal way to run would have much higher octain to allow the computer to give you the extra timing + the amount of boost you want.

again, deg of timing retard is not dangerous but is not ideal?

[blackbird_R/T]

It's about midnight here and I've still got to answer a couple PM's before I crash for the night. I was looking through my computer and still have some videos showing what timing does on a scan tool. That might give some visual examples of what's good and what's not so good to watch for. I just need to re-compress them which might take a while. I'll try to get back to this tomorrow.

For now and to give you some background on exactly what is timing, take a look at the following thread if you haven't already read it:

http://www.srtforums.com/forums/show....php?p=3077281

Post #38 gives an explanation on what the timing numbers actually mean which might help in understanding what you're watching on the gauge.

[TJ1376]

Quote: Originally Posted by Lagzilla

so if there is say 7 deg of knock retard that doesnt mean its dangerous, it just means you could do things to gain your timing back

Yes and no... The computer will take active measures to reduce and prevent detonation. That being said, it is still safe, but the car is still detonating. Detonation is NOT safe and hard on pistons. Remember, your not the first big turbo car on the block.. Many big turbos are out there, and have been running fine without problems, although I am sure under those increased pressures in the cylinder, they are experiencing a little bit of detonation, just like you.

Quote: Originally Posted by Lagzilla

for lets say us big turbo guys the less timing and more boost will yeild more power compaired to stock turbo.

Over the stock turbo sure.. But your thinking is backwards... MORE timing and MORE boost = MORE power. But there is a flip side. MORE timing and MORE boost = MORE prone to detonation, keeping all other variables as close to constant as you can.

Idealy, the rule of thumb is if you increase cylinder pressure, you want to retard timing. We have no way to do that in the SRT4. Infact, piggyback AFC's actually INCREASE timing while we increase cylinder pressure. When you think about this, our entire engine must be built by some of the best engineers on the planet.. Think about it, we have 500+ whp SRT4's running on stock internals and AFC's. The programming in the NGC HAS TO BE extremely conservative, and the engine must be built like a rock. Running into a little ping at those levels would normally be deadly.

Quote: Originally Posted by Lagzilla

so if we are running 20 psi on pump and pulling 6 deg of knock retard

that is still safe correct? because there is no knock.

No.. If the NGC is pulling 6 deg of retard, its due to something. The aero force guys have already chimed in and said that its due to knock. So, is it safe... Seems to be. Because there is no knock? Absolutely incorrect. The engine is experiencing detonation (knock) and taking corrective action to reduce timing advance to keep the pistons (and your wallet) happy.

Quote: Originally Posted by Lagzilla

even more so if there is 9 deg of knock retard, that is still "safe" because its doing its job in order to eliminate knock, and still making more hp then if oen were to pull boost down to say 17 psi and run more timing.

The safest knock retard to shoot for is zero. 9 may not be safe, and it definately will not produce as much power as zero. Will it make more power than 17psi and more timing. Thats only something you can find out on a dyno, and with an EMS system that will allow you to control timing. Your afc will not let you do that without SERIOUS modification.

Think about it like this... All the stage 0 guys who slap on an AGP wga without any kind of afc.. What exactly are they doing? They are increasing cylinder pressure, and allowing the computer to see it. What do we know about AFC's? They hide cylinder pressure from the computer. This increases timing advance and leans out the mix. Now, remember in our scenario, there is NO afc.. So, the computer sees the increase in pressure. We know that decreasing pressure causes a leaner mix and more timing... Take that the other way, increasing pressure and allowing the computer to see the increase in pressure MAY cause a reduction in overall timing advance and a richer fuel mixture. The final result? Their agp wga SRT4 can't run much faster, if ANY faster than a stock SRT. And I have proved this at the strip time and time again. Timing advance (even though you can't control it with an AFC) is JUST AS important as the amount of air you shove into the cylinder.

Quote: Originally Posted by Lagzilla

the ideal way to run would have much higher octain to allow the computer to give you the extra timing + the amount of boost you want.

again, deg of timing retard is not dangerous but is not ideal?

Runing higher octane gas does not allow the computer to give you more timing. It just allows the computer to continue to advance timing further than pump gas. As you increase timing, you are increasing cylinder pressure... Increasing cylinder pressure increases the likelyhood of detonation with all other variables held as close to constant as possible. The higher octane of race gas helps eliminate detonation.

In your situation, I would say the deg of knock retard you are running into is not a problem. Knock retard is definately not ideal, and if you solved your detonation problem, you would gain more advance and thus more overall power.

Please let me know if I need to be corrected anywhere in my thoughts. I am not a timing expert, and you have throughly exhausted my knowledge of timing, but I believe my thoughts are spot on. Please advise if you think otherwise.

TJ

[Lagzilla]

well i no on the same amount of boost, the computer will give you some timing back that was once retarded at least in my circumstance on race gas