What is a "Klopfregelung"?

Finn, Dominik and others,

The S38 does not have a knocksensor (Klopfregelung). Instead, it's DME is preset with values to allowe the use of Euro 95 Octane unleaded. This means that the DME does not alter ignition timing other fuel parameteres when other petrol is used. In the case of Super Plus 98 (or higher) this means no objective power increase, and with the use of 91 Octane benzin (Criminal offence ), this means that the ignition timing is not retarded and thus a high risk of knock.

Knocking (klopfen) will occur when the petrol/air mixture is not able to withstand high compression. The petrol/air mixture will 'self' detonate before the DME tells the ignition coil(s) to do so. Result, an uncontrolled explosion in the compression phase that could lead to the destrcuction of your pistons/bearings ect.

The higher the Octane rating, the higher it's abilities are to withstand high compression. With other words, Super Plus 98 will be able to withstand a higher compression then Euro 95 which is the minimum requirements for the E34 ///M5. But there is no power gain when using higher octane fuel.

Another reason why I always use Super Plus 98 is it's lowercontent of sulphur. Although the S38 has a cast iron engine block and is not affected by the sulphur-caused bore wear of the M60 engine with it's nikasil coating, the S38 does have a lot of other alloy parts. I may be bit dogmatic in this, but this is enough reason for me not to use Euro 95 or lower.

Never, ever run your S38 engine on Bleifrei 91, not even in an emergency situation. This fuel is not able to withstand the high C/R of the S38 and knocking will occur. Why risk a ++10k Euro At engine?

Zitat von donati

Dominik & Mad1980,

Thank you for the translation.

I am considering installing these:
http://tinyurl.com/2v2en

In a 3.8'er (3.9L ) for my trackcar, and the seller told me that i "might have to change the ignition system, because of the "Klopfregelung"."

I agree that there is no knock sensor on the S38 engines, so it makes little sense to me

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Karl,

I don't know why the brochure says so, but why doesn't the S38B38 technical information mention a knock-sensor.

I have helped translating the original Dutch version into an English version
version for the then m5springboard and I never read anything about a knock-sensor either.

Also the original German version doesn't mention anything about a knock sensor.

Which one do you then believe? The commercial version or the technical version. Added to that comes the fact that we have beaten this topic to death on the E34 ///M5 mailing list some while ago and the general concensus was that both the S38B36 and the S38B38 don't have a knock-sensor.

But I agree that based on your question, we can refire this question.

Karl,

One outcome of knocking are excessive vibrations. Even though there may be other technical possibilities to detect that, the use of knock sensors is the accepted method of implementing a anti-knock regulation. The technology behind it is widely available and easy to implement. I can't think of a valid reason to use a different and bc. of R&D cost a more expensive system.

I always make a distinction between commercial and technical information. Brochures always contain a disclaimer that specifications may change without notice. Since the 92 brochure is the same as the 93 brochure, it may very well be that the brochure is based on a draft specification thay may contain a knock-control regulation. The M5 3.8 technical description however does not mention this.

However, this is speculating and arises a new question that probably can only be answered by a design engineer from BMW ///M Gmbh.

As you suggested, I submitted this question to the mailing list on yahoo groups.

Rgrds,

Raymond

Zitat von m5tourreg

Raymond, the wording is taken from the 'Technik-Lexikon' of that broschure.
As I might hv mentioned before, my technical knowledge is limited. What I
am trying to say here is, cud it all be based on a basic misunderstanding ??
Cud it be that there
- is in fact a 'Klopfregelung'
- BUT without a 'knock sensor' ?? and controlled by the DME instead ???
-
just a thought ? what does -Gary- say abt it

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