Effects of timing retard

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I understand that timing retard causes loss of power, but what else besides that ? Does it affect anything else like combustion(quality/completeness), possibility of carbon deposits,
incorrect air-fuel ratio, and the EGR system ?
 
Retarded ignition timing will generally give you less power and lower fuel economy. It'll also reduce the engine's tendency to 'ping', allowing you to run lower octane gas (I'm assuming we're talking gas engines here).
 
You could be exposing more of the cylinder walls to the flame front with the timing retarded.. You should really try to keep that in the combustion chamber between the head and the top of the piston as much as you can. Cylinder walls don't make very good combustion chambers and the rings like it even less the next time they come around. You might also run warmer coolant and oil temps because of all that. Also the combustion pressure on a piston top that is falling away too quickly now that it's away from TDC is not as useful in producing torque. Also because the volume is much larger, the flame prorogation is more variable and the engine might run rougher. You will also effectively lower the heat range of your spark plug and reduce its performance and shorten its life. One place it will work in some engines running at max rpm and load and will actually produce more torque by retarding the timing a couple of degrees. It's common in land speed record attempts with a variation. You run the engine just past it's torque peak not max rpm. When you are running down the salt and hit a tiny gust of wind and the engine slows a few rpm you back up onto the torque peak and have your ignition mapping so that at that instant the timing gets retarded maybe 2 to 4 degrees and the torque goes up to answer the gust of wind and the speed tends to return, in other word like cruise control for racers.
 
I noticed an incredibly smooth, stable, low idle when I was futzing around on an old mazda truck.
 
What about the effects of retarding the timing by the PCM when running a engine that has torque management? I have a 07 Silverado with the 6.0. Every time the trans shifts under anything over half throttle ,the PCM cuts timing by about 20 degrees and it feels like you are taking your foot off the gas. This is supposed to help preserve the trans but I wonder what it is doing to the inside of the motor. I will be removing the torque management through a mail order or custom tune in the near future.
 
typically how much timing does the pcm retard when it detects engine knock ?
and those burnt exhaust valves and glowing manifolds - is that even in "normal" timing retard i.e. when knock sensor detects knock ? or just in extreme cases of timing retard ?
 
Re: Effects of timing retard [Re: LAGA]

TOTAL OUTRAGE!!!!
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shocked2.gif
You're not supposed to call 'em retards any more!!
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Now their some kind of "challenged" or something!

Why would you want to time them anyhow??
 
Knock sensors are simple microphones.
They are not a great system, but a fail safe system.
They pull a LOT of timing - 4-8 degrees, depending.
They can and are set off by other vibrations and normal engine conditions.
I pulled mine off my car, like so many other tuners/enthusiasts. The power curve smooths out because there are no false readings that yank timing here and there.
Use good fuel.
I like as much ignition advance as possible, with no spark knocking.
Better gas mileage and power.
Retarded ignition advance can be good for certain emissions, and was a quick way to help pass a test. Then we would put it back to where it belongs.
 
wouldn't it set a DTC and scale back to a "safe" timing curve if it didn't find a knock sensor or a faulty one ?
 
When they appeared in the 80s on turbo motors I believe they did a real rough job as a failsafe. So the timing curve was never meant to be altered unless there was a suprise problem... therefore saving the motor.

Recently though honda was bragging about squeezing a few more HP from some accord, due to an improved knock sensor. Also there was a dodge that ran on regular but could perk up with premium. I would fathom that the knock sensor is becoming or has become a regular part of the engine managment feedback loop.

To regularly disconnect a knock sensor without considering its effect on your specific car's calibration, is perilous.
 
The things that come to mine are higher EGTs, lower NOx emissions, less power, potentially higher water and oil temps, and much, much faster turbo spool.

I've found it's usually better to have the octane and timing curves right and not use the knock sensor at all. Besides the fact that knock is bad, it will usually pull more timing to stop the knock than if you had the timing right in the first place.

As for the comment about the Honda Accord, they suck. My TL pulls timing all the time whether it's light driving or WOT. WOT shows over 10 degrees of retard. It takes a minimum of 96 octane to suppress the knock and my car is stock. Many others have this problem. I'm not happy having to run good gas in a 258hp car. The knock sensor should be a failsafe, not a normal part of the ignition system like Honda seems to think.
 
so when it detects knock and retards timing then how long before it comes back to the "normal" advanced timing again ? Just in the next few strokes ? or are you stuck in it for .... how long ?

Is there any logic built into the PCM to go into retarded timing mode for a extended, if not permanent, period of time if it keeps detecting knock ? Like for example in a situation where you run low octane in a motor that calls for higher octane.
 
Originally Posted By: youdontwannaknow
so when it detects knock and retards timing then how long before it comes back to the "normal" advanced timing again ? Just in the next few strokes ? or are you stuck in it for .... how long ?

Is there any logic built into the PCM to go into retarded timing mode for a extended, if not permanent, period of time if it keeps detecting knock ? Like for example in a situation where you run low octane in a motor that calls for higher octane.


I'm not sure on the newer stuff. Watching the retard with the TL, the numbers moved up and down very fast. On my Buick, most of the aftermarket chips alter how the timing is put back in. Stock it's pulled out much faster than it's put back in. With most aftermarket chips it's put back in as quickly as it's taken out. Not sure on an actual time frame. I think it would be safe to assume any car puts the timing back in after a second or so of no knock.

I would never unplug the sensor unless you have to. If it's hurting performance, you need more octane. An exception is the faster of the GNs in my house has a solid cam and the valvetrain noise would set the sensor off continually.
 
Originally Posted By: BuickGN
I think it would be safe to assume any car puts the timing back in after a second or so of no knock.


I'd imagine the same too, but my experience with the Acura (mdx) has been different. When I switch to low octane fuel, it pretends as if nothing happened - for about half to full tank of gas, you wont feel any loss of power or mileage. But by 2 or 3 tanks it has degraded slowly to a point where I can easily tell. Then as soon as I switch to high octane again, in about 10 miles or so, it's as if it sprung back to life! The difference is very noticeable, and that too almost immediately.

Just trying to figure out why it does what it does....
 
Quote:
Just trying to figure out why it does what it does....


Are you always filling when empty. It almost sounds like you're diluting premium to the point where it's only regular ..then throwing back in premium (and making sure that you're near empty) to restore the octane. I mean, the effect would be the same if this was the case.
 
If it were dilution then it should work the same way when I start using premium again - i.e. a slow come back.
But I dont think its dilution. Yes I fill up only when its empty. In fact much after the "gas" light comes on. Usually there is a couple of gallons after that.
 
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