Tuners chime in-Closely riding knock sensors

[Munit]

So the cool knock sensor mechanism this engine has is obviously beneficial in terms of safety by preventing knock much more accurately.

However has anyone who has logged data actually seen if there is any performance benefit from this system in terms of ability to keep timing advanced to the maximum ability that a traditional knock system would be unable to do because of less accuracy and specificity of the knock sensing?

Essentially does this system let the computer ride the knock sensor to get max timing more so than a traditional system? And if it is possible, does the engine actually due this?

I figure that may explain the ability to continue to make more power up to 96 octane or what not

[Krozi]

Interesting question, in for replies.

[BMRLVR]

Originally Posted by Munit

So the cool knock sensor mechanism this engine has is obviously beneficial in terms of safety by preventing knock much more accurately.

However has anyone who has logged data actually seen if there is any performance benefit from this system in terms of ability to keep timing advanced to the maximum ability that a traditional knock system would be unable to do because of less accuracy and specificity of the knock sensing?

Essentially does this system let the computer ride the knock sensor to get max timing more so than a traditional system? And if it is possible, does the engine actually due this?

I figure that may explain the ability to continue to make more power up to 96 octane or what not

You answered your own question in the last line!

The reason the engine makes more power with increased octane ratings is due to the knock sensing systems ability to maintain timing at or near the PPP (peak pressure point) in the cylinder up to the max timing advance number written in the map. An acoustical knock system listens for knock and pulls timing from the pre-determined advance number in the map where as the Ionic knock sensing system maintains timing at the PPP point.

The Key to being able to run a knock sensing system as advanced as the one on the S65 is totally dependant on having an ECM (DME in BMW speak) that is able to handle the computational abilities that a system like this requires. The MSS60 is the main reason the the S65 is able to rev as high as it does and make such power for it's displacement......... The MSS60 is one of the smartest ECM's in the the automobile industry and it's ability to process so many input signals and control so many actuators at such a high speed is why the S65 is so good! I read an interesting article about the new 5.0 Coyote/Roadrunner engine in the Ford Mustang about a year ago. The thing that stuck out at me in the article was the admission from ford that the ECM they use in the Mustang is not smart enough to control the engine reliably at engine speeds in excess of 7500RPM. The MSS60 in comparison has been tested at 9000+RPM on the dyno in durability testing.

So the short answer is yes the ionic knock sensing system is able to do things that a traditional acoustical knock sensing system can't.

[VCP]

Originally Posted by BMRLVR

You answered your own question in the last line!

The reason the engine makes more power with increased octane ratings is due to the knock sensing systems ability to maintain timing at or near the PPP (peak pressure point) in the cylinder up to the max timing advance number written in the map. An acoustical knock system listens for knock and pulls timing from the pre-determined advance number in the map where as the Ionic knock sensing system maintains timing at the PPP point.

The Key to being able to run a knock sensing system as advanced as the one on the S65 is totally dependant on having an ECM (DME in BMW speak) that is able to handle the computational abilities that a system like this requires. The MSS60 is the main reason the the S65 is able to rev as high as it does and make such power for it's displacement......... The MSS60 is one of the smartest ECM's in the the automobile industry and it's ability to process so many input signals and control so many actuators at such a high speed is why the S65 is so good! I read an interesting article about the new 5.0 Coyote/Roadrunner engine in the Ford Mustang about a year ago. The thing that stuck out at me in the article was the admission from ford that the ECM they use in the Mustang is not smart enough to control the engine reliably at engine speeds in excess of 7500RPM. The MSS60 in comparison has been tested at 9000+RPM on the dyno in durability testing.

So the short answer is yes the ionic knock sensing system is able to do things that a traditional acoustical knock sensing system can't.

1+ MSS60 can do 200million calculations per second

[BPMSport]

There are a few difference philosophies I've see in tuning for the MSS60 and MSS65:

1. Run high ignition targets and 'ride' off of the knock sensors.

The M3 calls for 32 degree of timing at redline in the stock calibration, full throttle. Many cars on 91 will hit this when not in extreme temperatures. I've seen files where there is more of a 5 degree ignition advance there even on 91 octane gas! Talk about riding on the knock sensors... Buy hey - it's good - so the engine won't blow. The car will just pull timing and make less power, although the MSS60 calibration only has a certain window of timing pull.

2. Determine the mods and octane that the car will normally run in its useful life. Program targets for timing which are realistically attainable. This way you're only relying on 'knock' feedback from the coils and plugs in extreme cases, such as very high humidity, low octane gas, or very high temperatures. This is the right way of doing it. Because of this DME's sophistication, that's why people get away with not doing it this way.


The choice is clear between them. #2 is a winner.


There are also 'minimum ignition' maps which specify the minimum amount of ignition to be run across various loads and RPM. The DME uses an interpolation function in-between given points to determine ignition at a particular point.

I attached the stock ignition targets at the bottom.

I've logged timing on the dyno and on the track. M3's on 93 and usually 91 octane will hit the 32 degree target. But as IAT's start to rise you will see it slowly drop down with successive runs. Running off the knock sensors causes power loss in the long run.

[Munit]

Thanks Mike, very helpful. I wonder why bmw did not implement that in any of their new engines? (or did they?) I guess timing is really not that important with turbo engines in terms of squeezing out horsepower from a NA engine.

So if 91 octane hits 32 degrees which is the most advanced timing the car does, what temperature do you think 91 would stop hitting the targets? I mean more external temperture with hard street driving (not track). I am finding with temps 70 degrees and below it seems like my car pulls equally hard on 91 or 94. In the Summer in temps of 100 I feel my car is a turtle to an extent and is greatly helped by 95 octane which I mix from race fuel and 91.

Any guess on a rought guide of what temps would be good to stick with 91 and what temps to start mixing? Could just save a few bucks is all.

Also- I read a lot more on your tunes and have to apologize for being rude. You actually have posted a lot of objective data and do believe you are the best straight tuner on here. With that said I am able to run 95 octane all the time and was wondering what kind of gains and spark advance could you do with 95 octane tune? Something pretty significant like 20hp?

[Bimmer-ish]

The S65 uses the ignition coils to detect knock from feedback that the spark plug and coil voltage supply. Sorry if this is bringing up an old post. But I just watched a video that showed the S85 units as a S65/S85 fix. It was a good video but the coils check each cyl. separately on the S65.