February 18, 2012

Super Knocking!

I've been observing "Super Knocking" is a common problem associated with EP6-DT* engines. At the beginning it is not easy to detect by normal "feel" [or with "buttDyno"] because most of the time the ECU would regulate the combustion parameters accordingly to make the engine run as usual after it had sensed "knocking". Not withstanding, once happened, there is a high probability for a series of unfortunate events to happen which lead to a catastrophe.

The remedy could cost a fortune!

It is essential for you to have OBD2 diagnostic tools ready all the time - as the "first aid" kit and lets you know what's happening in your car engine. The diagnostic tool normally comes as a stand alone device [OBD2 Scanner] or a set of ELM327 dongle and diagnostic software [for laptop] can be bought on-line cheaply nowadays. Some diagnostic software can even be downloaded for free!

The Causes of Engine Knock
Simple answer to engine knock is "Abnormal Combustion", but no one really knows exactly the reasons behind "super knocking". Based on what had happened to myPeugeot308 looks like the mechanics at an authorised SC is doing trial-and-error* method to solve it.

Episode 1 - Sept 3rd, 2011
Happened on my way back from Kelantan via Gerik. Just after Ipoh the car lost power. Set the car on autoCruise at 90kph for 20km. Power back again. Very powerful!. A week later the car was sent to an authorised SC to rectify the problem . A HPFP was replaced [foc]

Episode 2 - Nov 6th, 2011
Drove to Kelantan via KLipis. Happened again at the beginning of the trip but restored after Gombak Toll Plaza. Got all the power needed for Karak Highway

Episode 3 - Nov 8th, 2011
Loss power while driving from Kelantan towards Kuantan. It happened just after passing Jertih. Drove the car all the way to Kuantan at reduced power. Top speed on newly opened ECE2 was less than 180kph. Normally I did above 200kph there. The next day continued driving along coastal roads to JB. In JB the car was diagnosed for "mis-communication" between gearbox and the ECU hence fuel regulation fault detected - rich mixture at low load and lean mixture at high load.

Read more on the 1500-km misadventure HERE.

Episode 4 -Dec 12, 2011
Infamous "Intermittent power loss" happened again. This time more often than before. Sent the car to an authorised SC again. The mechanic suggested for top overhaul to change ignition and valve timing mechanisms including timing chain... sounded very scary. Spare parts not available. Got to wait. Drove the car back home. No more power loss after resetting the ECU but a couple of time the engine jerky briefly. Total count for ECU resetting done to date is FIVE...

Episode 5 - Feb 14th 2012
Spare Parts arrived. Sent the car again to get the work done.

*Note: I've heard they even offer engine replacement. Not in Malaya of course. Read HERE- but there are cases here in Malaya where cylinder heads had got to be replaced as a result of the "super knocking".

Better get it done during the warranty period. The time bomb is ticking. Yours could be next.

If you notice a metallic rattling noise coming out of your car engine and/or a sudden loss of power when the accelerator pedal is pressed down aggressively that means the engine is suffering from a condition known as "engine knock".

What you have to do is immediately back off the throttle and drive the car at low rpm to allow the ECU investigate and respond accordingly. There is a knock sensor that detects this as it happens and the ECU backs off the fuelling causing the engine to run lean and reduce/avoid knock. The knock sensor however, may not save an engine from the effects of a "super" knock.

What exactly is engine knock and how dangerous is it?
Engine knock is a condition where the fuel in the engine ignites prematurely and can cause serious damage to the engine. When the engine ignites prematurely where the piston has not arrived at its TDC position there is a tendency of forcing the crank to run in the opposite direction which puts a lot of stress on the crank and pistons hence causing damage in a long run.

What makes the fuel ignites prematurely?
When there is an excessively high pressure inside the combustion chamber the fuel can ignite prematurely before the spark timing. For instance, too much turbo boost setting (by remapping and chip tuning) will also increase the risk of compression based pre-ignition. Another cause of premature fuel ignition include hot spots inside the engine. The infamous carbon deposit around intake manifold in direct-injection engine will make it glowing red hot and igniting the fuel as it enters the combustion chamber.

How to avoid engine knock and pinging?
1. Back to old school-book advice... the octane rating of fuel describes the fuels resistance to engine knock. In a lot of cases simply switching to a higher octane fuel may solve the engine knocking problem. A lot of modern cars run on high compression ratios and require high octane fuel be used. If you want to save money on fuel and use RON95 back off the throttle and drive with low rpm speeds. 

2. Top-overhaul and de-carbon... there are also a number of effective engine cleaning methods that do not require top-overhaul such as by spraying "certain chemical" into the intake to clean and remove the carbon/tar-like deposits.


pyan said...

Bro ahwan, wat abot EP6CDT engine?? Affected as well?

AHW said...

EP6CDT is Euro5/updated version of EP6DT engine. At this point of time I'm not so sure whether it is not effected but I'm certain it is not a problem free engine.

mohdnazri said...

Hi... I am also facing this super knocking problem when acc to 90kmh.. any good news to solve this problem?


Jeff Sin said...

Hi Ahw308, do you change to new cyclider head?

Jeff Sin said...

Hi Ahw308, may i know do you replace your cylinder head claim by service center?

Jeff Sin said...

do you have any idea to clear off carbon issue by direct injection engine?

Jeff Sin said...

so after the cylinder head changed, is there any side effect, known that engine parameter all different already, and the car engine has been dismantle, not like original anymore :(


How about EP6CDTM (408turbo)?

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