Ping/detonation vs. engine timing
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Ping/detonation vs. engine timing
This is a basic engine theory question - please don't flame me if this sounds stupid.
Using a JRSC on a Type R (but this shouldn't change the answer):
So ping/detonation occurs when fuel/air mixture ignites itself either due to high temperature, high pressure, lean mixture, etc. prior to when the plug is timed to trigger that ignition.
So, my question is, if when using a higher than spec boost, the instructions are to add retard to the timing (i.e. spec is 16°BTDC, recommendation is 7°BTDC with 92 octane @ 5lb boost). My understanding is that this is to eliminate ping/detonation. But if the fuel/air pressure/temperature is going to self-pre ignite anyway, how does delaying the plug spark till after that event help?
Again, please be nice - just getting started here.
Thanks
Using a JRSC on a Type R (but this shouldn't change the answer):
So ping/detonation occurs when fuel/air mixture ignites itself either due to high temperature, high pressure, lean mixture, etc. prior to when the plug is timed to trigger that ignition.
So, my question is, if when using a higher than spec boost, the instructions are to add retard to the timing (i.e. spec is 16°BTDC, recommendation is 7°BTDC with 92 octane @ 5lb boost). My understanding is that this is to eliminate ping/detonation. But if the fuel/air pressure/temperature is going to self-pre ignite anyway, how does delaying the plug spark till after that event help?
Again, please be nice - just getting started here.
Thanks
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From: Colorado
Originally Posted by boosted hybrid
Knock and Pre-Ignition
Knock is the most important abnormal combustion phenomenon. Knock is created as the flame front travels across the combustion chamber, and the unburnt mixture ahead of the flame called end gas, is compressed. The compression of the end gas causes its pressure, temperature and density to increase. The product of this event is that the unburnt gases rapidly release its energy up to 25 times that of a normal combustion event. This in turn causes high frequency pressure oscillations inside the cylinder, that in turn produces a sharp metallic noise called knock.
The presence, or absence of knock reflects the outcome of a race between the advancing flame front and the precombustion reactions in the unburned end gas. Knock will not occur if the flame front consumes the end gas before these reactions have time to cause the fuel-air mixture to auto ignite. Knock will occur if the precombustion reactions produce auto ignition before the flame front arrives.
The other significant abnormal combustion phenomenon is pre-ignition, or surface ignition. Surface ignition is ignition of the fuel-air charge by overheated valves or spark plugs, by glowing combustion-chamber deposits, or by any other hot spot in the engine combustion chamber: it is ignition by any source other than normal spark after normal ignition (post ignition). It may produce a single flame, or many flames. Uncontrolled combustion is most evident and its effects most severe after the spark plug fires (post ignition), the spark discharge no longer has complete control over the combustion process. Surface ignition may result in knock. Knock occurs following normal spark ignition is called spark knock to distinguish if from knock which has been preceded by surface ignition.
Knock is the most important abnormal combustion phenomenon. Knock is created as the flame front travels across the combustion chamber, and the unburnt mixture ahead of the flame called end gas, is compressed. The compression of the end gas causes its pressure, temperature and density to increase. The product of this event is that the unburnt gases rapidly release its energy up to 25 times that of a normal combustion event. This in turn causes high frequency pressure oscillations inside the cylinder, that in turn produces a sharp metallic noise called knock.
The presence, or absence of knock reflects the outcome of a race between the advancing flame front and the precombustion reactions in the unburned end gas. Knock will not occur if the flame front consumes the end gas before these reactions have time to cause the fuel-air mixture to auto ignite. Knock will occur if the precombustion reactions produce auto ignition before the flame front arrives.
The other significant abnormal combustion phenomenon is pre-ignition, or surface ignition. Surface ignition is ignition of the fuel-air charge by overheated valves or spark plugs, by glowing combustion-chamber deposits, or by any other hot spot in the engine combustion chamber: it is ignition by any source other than normal spark after normal ignition (post ignition). It may produce a single flame, or many flames. Uncontrolled combustion is most evident and its effects most severe after the spark plug fires (post ignition), the spark discharge no longer has complete control over the combustion process. Surface ignition may result in knock. Knock occurs following normal spark ignition is called spark knock to distinguish if from knock which has been preceded by surface ignition.
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Thanks for the reference - I'll need to chew on this one for a while.
Your byline "'92 Civic Hatch - 10.9 @ 135 MPH, 100% streetcar (SFWD) spinning down the 1/8th VIDEO all at 6000feet elevation." is interesting.
I am getting ping with this ITR/JRSC combo at 5K ft elevation with a short ram and all else stock w/91 octane. The only way I can get it to stop is with the stock air box, which limits power. From the reference, I'm wondering if headers would help clear the cylinder of the unburned end gas and help eliminate. I'm not sure if pre-spark knock or post-spark knock.
Your byline "'92 Civic Hatch - 10.9 @ 135 MPH, 100% streetcar (SFWD) spinning down the 1/8th VIDEO all at 6000feet elevation." is interesting.
I am getting ping with this ITR/JRSC combo at 5K ft elevation with a short ram and all else stock w/91 octane. The only way I can get it to stop is with the stock air box, which limits power. From the reference, I'm wondering if headers would help clear the cylinder of the unburned end gas and help eliminate. I'm not sure if pre-spark knock or post-spark knock.
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sorry for the delay - had to step out -
There definitely aren't any fuel leaks, and it doesn't act like vacuum leaks (i.e. running a marshall fuel pressure gauge - pressure set at 61psi, with quick throttle, pressure jumps rapidly, etc.).
I'm not familiar with a wideband, but aside from the Jackson, everything else is stock.
I've had to play with fuel pressure and timing - and of course using the stock air box - to get rid of the nock. the FMU is installed properly (reviewed it about a dozen times), all else appears to be correct as well.
I'm wondering if the altitude/pressure drop is greater affect than the thinner air at the intake. It certainly doesn't perform to JRSC quoted dyno graphs. We dynoed before, hit 163hp @ 8.5K - it now has ~ 30-40% gain until it hits 6K, then stays on linear slope hitting 175hp @ 8.5K. From the dynos, it appears the VTECH is kicking in correctly. I questioned Jackson about the FMU performance - they say it's working properly. I've also heard their FMU is not very good.
Thanks for any ideas.
There definitely aren't any fuel leaks, and it doesn't act like vacuum leaks (i.e. running a marshall fuel pressure gauge - pressure set at 61psi, with quick throttle, pressure jumps rapidly, etc.).
I'm not familiar with a wideband, but aside from the Jackson, everything else is stock.
I've had to play with fuel pressure and timing - and of course using the stock air box - to get rid of the nock. the FMU is installed properly (reviewed it about a dozen times), all else appears to be correct as well.
I'm wondering if the altitude/pressure drop is greater affect than the thinner air at the intake. It certainly doesn't perform to JRSC quoted dyno graphs. We dynoed before, hit 163hp @ 8.5K - it now has ~ 30-40% gain until it hits 6K, then stays on linear slope hitting 175hp @ 8.5K. From the dynos, it appears the VTECH is kicking in correctly. I questioned Jackson about the FMU performance - they say it's working properly. I've also heard their FMU is not very good.
Thanks for any ideas.
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From: Colorado
The best solution for any FI car is proper tuning... I'm not completely convinced that you don't haver a mechanical problem though. I know those FMUs (as well as all FMUs) suck ass. Make sure you've got a good solid vacuum system (you could pressure test it if you wanted to).
Can you post a pic of the dyno graph?
You should considera standalone EMS... you can get great dwals on them now, and its much cheaper than rebuilding your ITR... where are you located?
Can you post a pic of the dyno graph?
You should considera standalone EMS... you can get great dwals on them now, and its much cheaper than rebuilding your ITR... where are you located?