Engine knock when in Normal mode

1326 Views 40 Replies 12 Participants Last post by jjrichar, 11 d ago

jarlinge64

Discussion Starter · 27 d ago

I have recently noted a peculiarity; when in Normal mode in low RPM under load, the PDK is selecting relative high gears but still increase throttle load and the consequence is ignition knock that is quite easy to hear. When I go to Sport mode, no knock can be heard anywhere no matter the applied load.
I have seen several reports on this in this and other forums, but no solutions have really been given. I am thinking that a re-calibration of the PDK could provide a fix as the car seem to run higher gears for too long, adding unwanted load to the engine. I am running new 5/50 oil, new plugs and new components that usually can produce knocks if not maintained correctly. I have not checked any knock sensors though.
Any thoughts?

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gedwin

· #2 · 27 d ago

Hi,
I can't really respond to your particulars as detailed above, but I can offer the following. I have been chasing ignition knock in my 2013BB for 10 years. I experienced it between 1800-2800RPM under medium load only. I have worked with FVD, and they have written a tune that helped eliminate the knock. I have researched fuel, oil, timing, engine design, etc. in my quest to eliminate it. Once in a while I still would get a bit.

Cutting forward to now, this is what I believe and what I am going to do. I have concluded it is LSPI resulting from Engine design (DI), and oil additives that promote the problem. I believe switching to an SP certified oil may solve the problem. I use Mobil1 FS oil, and up to and including my last oil change, it was SN certified, and that is a problem.

Since then, the oil additives have changed (3Q 2022), Per my email discussions with ExxonMobil, and changing to that uprated oil may solve the problem. SN+ and SP oils help prevent LSPI, SN does not. SP also helps with cam chain wear.

There are other oils available that are SP certified, but I couldn't find one that was also A40 rated, so I refrained from switching at that time. Mobil1 FS European Formula is now SP and A40 certified, just make sure the bottle says so, so you don't end up buying old stock.

I will be trying this shortly, so I hope I can report back that the knock issue is finally solved.

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jarlinge64

Discussion Starter · #3 · 27 d ago

Interesting. I switched from Shell syntetic 0w-40 (A40 approved) to Mobile 1 5w-50 (A40 and SN rated) for this season, The oil is not SN+ nor SP rated ( but is a FS X1 product).

jarlinge64

Discussion Starter · #4 · 27 d ago

Done a rudimentary check; the only A40 oil with API SP rating is LiquiMoly Leichtlauf HighTech 5w-40. Any others? Any experiances anyone?

JamesBond

· #5 · 27 d ago

Ive switched to Liquimoly and like the product. I do not have knock tho. I assume your gas it high test and not from a "knock off" station. I know a guy in the petrol business and he informed me a bit ago( most important now) to use name brands that include cleaners in their fuel.

jarlinge64

Discussion Starter · #6 · 26 d ago

Only use high quality gas, premium 98 from Shell or Esso

Platinum5150

· #7 · 26 d ago

The latests PCA Tech Tactics touched on this.

The presenters strongly recommended Driven DI40.

Reactions: 1

ELCID86

· #8 · 26 d ago

Platinum5150 said:
The latests PCA Tech Tactics touched on this.

The presenters strongly recommended Driven DI40.

I’m giving it a go on my summer oil change (no knocking that I’ve noticed).

Reactions: 1

Phat Hippy

· #9 · 26 d ago

I use DRIVEN DI40 oil exclusively and at 3500 mile intervals. I would probably never run my car in the normal mode having noticed the engine load/RPM is way off for my liking, and run in sport and sport manual to keep the RPM's up. It's better for the engine. If you are going on an economy run and need to run with the PDK fuel economy shift programing, it kind of puts the engine right on the edge of knocking conditions. Add a bad tank of gas and viola you're a knocking. I also only use top tier gas from Shell or Exxon, 93 octane minimum. I also add a can of Liquid Moly Jectron fuel additive about four times a year. I hope you find it is something minor. Start there first.

Reactions: 1

jjrichar

· #10 · 26 d ago

Something that might be worth checking is a boroscope of the piston crowns. A friend of mine was chasing a pinging issue in a BMW for a long time. In the end was found to be a build up of carbon on the piston crowns from excessive oil getting into the cylinders from a poorly performing air oil separator. From your discussion prior to this of having carbon build up in the intake ports and having to walnut blast, this might be a factor that could be easily checked.

jarlinge64

Discussion Starter · #11 · 26 d ago

Thx! That is very much something I've considered especially since it seems to be on the sme side of the engine that gets most of the air/oil residue from the PCV line. I still hv not been able to explain why that is, but every time I've boroscopet the inlet valve area, it is always cyl 1-3 that gets the most. And always the right exhaust tip that is most sooted.
But a fix? Replace the air/oil separator? No excess oil seem to flow through the intake system at start-up or when running, an indication that it seems to do its job as intended. But I noticed your comments on the effectiveness of the system that Porsche might haveprioritized durability over the former. If correct, a catch can could be the only way out?

jjrichar

· #12 · 26 d ago

jarlinge64 said:
Thx! That is very much something I've considered especially since it seems to be on the sme side of the engine that gets most of the air/oil residue from the PCV line. I still hv not been able to explain why that is, but every time I've boroscopet the inlet valve area, it is always cyl 1-3 that gets the most. And always the right exhaust tip that is most sooted.
But a fix? Replace the air/oil separator? No excess oil seem to flow through the intake system at start-up or when running, an indication that it seems to do its job as intended. But I noticed your comments on the effectiveness of the system that Porsche might haveprioritized durability over the former. If correct, a catch can could be the only way out?

I don't know of any other way to effectively eliminate the intake carbon build up other than a catch can. The AOS from what I've observed will always allow a certain amount of oil through when working correctly. Some, like you, seem to get the build up in an asymmetric way, which creates additional issues. I'm definitely not saying this is the cause of the pinging, but I think it's at least worth investigating.

Reactions: 1

gedwin

· #13 · 26 d ago

Found Mobil1 FS last night with the SP certification. Oil draining now so will test over the next few weeks.

Researched the Driven DI, and it should be ok, but decided for now I'm not going with it for my own reasons. If oil used is SP certified, it should not promote LSPI, so we will see if anything changes after the new Mobil1 is installed. If it still pings, then the cause is something else.

Car can ping in normal or sport, as long as the RPM is in the range, and medium load.

I have always used Shell Ultra 93 only, and it has pinged from new with a couple thousand miles on it. In my opinion, just about the amount of time it would take the oil to migrate past the A/O separator and move through the intake system to the combustion chambers. Same this time after cleaning the intake and intake valves.

We'll see...

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jarlinge64

Discussion Starter · #14 · 26 d ago

The Ghost in the Machinery👍

jarlinge64

Discussion Starter · #15 · 26 d ago

Just checked the product sheet of Mobil 1 FS 0w-40; in the Norwegian version API SP is not mentioned but in the English one it is. So, most likely it is.

gedwin

· #16 · 26 d ago

jarlinge64 said:
Just checked the product sheet of Mobil 1 FS 0w-40; in the Norwegian version API SP is not mentioned but in the English one it is. So, most likely it is.

Check the date on the product sheet. ExonMobil says changes were implemented 3rd Q last year. Also check the bottle.

Platinum5150

· #17 · 25 d ago

Just checked the jug I got from Wally World towards the middle of November and it's unfortunately SN.

Liquid Automotive tire Fluid Gas Cylinder

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jarlinge64

Discussion Starter · #18 · 25 d ago

jjrichar said:
I don't know of any other way to effectively eliminate the intake carbon build up other than a catch can. The AOS from what I've observed will always allow a certain amount of oil through when working correctly. Some, like you, seem to get the build up in an asymmetric way, which creates additional issues. I'm definitely not saying this is the cause of the pinging, but I think it's at least worth investigating.

I think I will add a catch can. I've been in and out of the idea, but I now conclude that it is the best option. I do not drive the car in winter.
One thing that still pussles me after seeing your video on the topic, is the ventilation valve on the Provent and the need to seal it. I do not understand why this would be required. The purpose of the valve should be to off-vent excess pressure, and if you logged elevated crank case pressure - I would have thought you needed it open?

jjrichar

· #19 · 25 d ago

jarlinge64 said:
I think I will add a catch can. I've been in and out of the idea, but I now conclude that it is the best option. I do not drive the car in winter.
One thing that still pussles me after seeing your video on the topic, is the ventilation valve on the Provent and the need to seal it. I do not understand why this would be required. The purpose of the valve should be to off-vent excess pressure, and if you logged elevated crank case pressure - I would have thought you needed it open?

The provent is designed for an engine that doesn't have a crankcase vacuum control valve, and hence it's fitted with one to control it. It doesn't vent to the outside, but does exactly the same thing as the valve in the AOS.

I did a load of testing of crankcase vacuum with the two control valves in series (AOS and the provent) and it does some really weird things. I was actually getting positive crankcase pressure with the two in series.

When I blanked off the Provent valve, it returned to standard crankcase vacuum levels that are provided by the AOS, and hence why I did so permanently. It wasn't in the video, but I did a lot of testing with a manometer over a few days to check everything before I came to the conclusion that having the Provent valve permanently open was the best option.

The way I check to see the system is working OK is to check the crankcase vacuum at the oil fill port. I show this in the video. Having two cars in the shed to check, one with a catch can and one without, is convenient. I only checked again in the last week, and they are identical. One of the problems with having the install out of view is it's difficult to easily see if everything is still connected correctly over time. Checking the crankcase vacuum at the oil fill port is a very simple way to check, as if any of the connections have come loose, you won't get crankcase vacuum.

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OneTimeCS

· #20 · 21 d ago

Are you sure it's knock? There's a valve in the intake plenum that opens and closes at low RPM and high load that makes a clacking sound.

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