[F31B48]

Originally Posted by e90bae

did you ever figure out what it was? I have the exact same issue. the first inch of throttle between 2k-3k rpm I hear what sounds like chain slap, but once I add more load to the engine it goes right away and comes back when I release the pedal and pass the same spot. I can coast and hold the pedal and hear it constantly but as soon as I go past that point it goes away. It gets a lot quieter after 10 minutes of driving but I can still barely hear it. changed my oil, did a full engine flush, took off the accessory belt and drove but the noise is still there, so that means it's internal. took out my valvetronic motor and inspected. there is some wear on the spindle and on the gear inside the valvecover. maybe I didn't seat it right when I replaced the valve cover gasket last time and it damaged that gear or something? can barely hear it at idle when I rev it up but since there's no load on the engine its barely audible but if I feather the throttle quickly between 2k-3k rpm you can hear it better at the beginning of each feather of the throttle. my friend was under the hood when I tried this and he said its definitely coming from the top of the engine and not the front(timing chain) or the bottom(exhaust). When I replaced my valvetronice motor it went away, but I got and engine code for accidentally taking off my maf and forgot to replug it in, but I didn't notice and thought I messed up the Valvetronic motor so I took out the valvetronic motor and replaced/relearned end stops but now the noise is back and can't seem to get the noise to go away even by replacing Valvetronic motor and relearning the end stops again. I'm at a loss.

What you are hearing is highly likely to be combustion detonation/knock or "pinging" The easiest way to confirm this is to put some high octane fuel in it and see if it improves. My car dors it as well and i found that running it on 100 octane greatly reduces it. If i use 91 it rattles really really badly. 95 is better but still not to my liking. Try some 100 if it's available over there.

[rjahl]

Originally Posted by EvaBmw

What you are hearing is highly likely to be combustion detonation/knock or "pinging" The easiest way to confirm this is to put some high octane fuel in it and see if it improves. My car dors it as well and i found that running it on 100 octane greatly reduces it. If i use 91 it rattles really really badly. 95 is better but still not to my liking. Try some 100 if it's available over there.

Not likely, throttle tip in would have a very low VE and cylinder pressures. Also, it's very unlikely that you will here these motors knock.

The DME is constantly monitoring the engine noises and adjusting the ignition timing as needed. The DME will pull timing well before the human ear can hear any type of preignition knock.

That's OEM tune, if you are running an aftermarket Tune, it's a different story.


I really expect the problem or noises to be the common lifter knock.

[Spitfire007]

I never figured it out. Sold the car over a year ago.

[F31B48]

Originally Posted by rjahl

Not likely, throttle tip in would have a very low VE and cylinder pressures. Also, it's very unlikely that you will here these motors knock.

The DME is constantly monitoring the engine noises and adjusting the ignition timing as needed. The DME will pull timing well before the human ear can hear any type of preignition knock.

That's OEM tune, if you are running an aftermarket Tune, it's a different story.


I really expect the problem or noises to be the common lifter knock.

I agree with you 100% in the sense that that is how is supposed to work, but for some reason my car detonates really badly when using low octane fuel, and using 100 octane reduces it a lot. I suspect that the voltage signal that the knock sensors produce diminishes over time and mileage and as a result the DME is unable to adjust the timing accordingly. That is just a theory though. What are your thoughts on that theory?

[rjahl]

Originally Posted by EvaBmw

I agree with you 100% in the sense that that is how is supposed to work, but for some reason my car detonates really badly when using low octane fuel, and using 100 octane reduces it a lot. I suspect that the voltage signal that the knock sensors produce diminishes over time and mileage and as a result the DME is unable to adjust the timing accordingly. That is just a theory though. What are your thoughts on that theory?

Don't really subscribe to this idea. I had 200k on mine and the knock sensors worked just fine.

You can log the sensor outputs and see if the values make sense.

Are you running stock or do you have a tune? Some of the "wild cat" tuners do strange things to the ignition timing and knock control.

[F31B48]

Originally Posted by rjahl

Don't really subscribe to this idea. I had 200k on mine and the knock sensors worked just fine.

You can log the sensor outputs and see if the values make sense.

Are you running stock or do you have a tune? Some of the "wild cat" tuners do strange things to the ignition timing and knock control.

I just have the Bimmerlabs 325i tune in mine that i put in when i changed to a 3 stage manifold. I have the N52B25. It was doing this on the stock 323i tune as well. Didnt change at all.

I'll take it for a drive with INPA and see what i can see. It's 36°c here today so it should do it consistently.

[F31B48]

Wasn't able to find knock sensor values in INPA or ISTA.
I think i will replace the knock sensor and see if that improves it.

[rjahl]

I don't recall if this was in knock sensor values were in INPA or not, Pretty sure they would be. I always used Test-o for logging and I used a custom job that included the KLOP signals.

Why to hard to do a full throttle run though the gears while watching INPA on a laptop. Anyways things happen too fast for you to catch it. Values might go high for 1/10 of a second.