Tat..Tat Noise in Engine

[Grant Lenahan]

Hi Max,

1. The long-known audi lifter noise may be partly due to 
sticking/deposits, but is frequently known to go away with different 
oil weight, brand or simply a change. This suggests to me that it is 
hydraulicly related, nto necessarily a dirty lifter.

As to octane., the issue has little to do with mileage, and everything 
to do with compression. The compression of a turbo motor is higher than 
normal by the factor of boost - probably about 1.4x or so.

Anything less than 93 will knock at these boost and effective 
compression levels. In fact, 93 may often knock. What saves you (all of 
us) is the knock sensor that retards ignition.

The 285k suggestion by some mechanic must have been based on a (very 
tenuous) correlation between age, mileage and carbon buildup, which 
affects effective compression ratio, and also can act as an untimed 
spark plug (the carbon, that is). Other than that, its total nonsense.  
What does you owners manual recommend?  Every turbo I've ever owned 
specified premium, and if its doesn't, its at the behest of the 
marketing dept.  Octane is, quite simply, a measure of knock 
resistance. In fact, one of the two components, the "AKI" component, 
stands for "anti-knock index".  That in and of itself, says a great 
deal.

Enjoy,

Grant
On Jul 3, 2006, at 8:16 PM, Max Hoepli wrote:

> I think the issue has been answered. I mentioned all related issues.
> Are the valve lifters making such a noise because of film deposit on 
> valve
> stems? The valves are sticking. Think I'll just use highest octane
> available. Have been advised by mechanics that an engine with 285,000 
> km.
> can take medium alternately with super.
>
> Does Sunoco have RON higher than 91?
>
> Generally use Esso RON 91.
>
> Max
>
>
> ----- Original Message -----
> From: "Grant Lenahan" <glenahan at fastmail.fm>
> To: "Max Hoepli" <mhoepli at vif.com>
> Cc: "audi s-cars list" <s-car-list at audifans.com>; <urq at pacbell.net>;
> <200q20v at audifans.com>; "Quattro at AudiFans" <quattro at audifans.com>
> Sent: 03, July 2006 19:31
> Subject: Re: Tat..Tat Noise in Engine
>
>
>> Wow - so many unrelated issues to address!
>>
>> 1.) My first guess would be valve lifters, and if so, its no big deal.
>> 2.) 89 octane is too low for a -any- turbo car
>> 3.) rislone probably wont help anything unless your engine has been
>> gunked up.   I think you need to explain what you are thinking, unless
>> everyone but me knows already.....
>>
>> Grant
>> On Jul 3, 2006, at 7:27 PM, Max Hoepli wrote:
>>
>>> I have a MC engine in Type 44 Quattro, with turbo charger  with
>>> 285,000 km. when idling it makes a
>>> tat...tat....tat......tat.......tat...noise from top part of engine.
>>> When inside of car noise is not heard. Engine never overheats, starts
>>> immediately. Sometimes there is white smoke coming out of exhaust 
>>> just
>>> after starting. I alternately fill tank with RON 89 and 91. What 
>>> could
>>> problem be?...if any? Gasoline may be issue. Could Rislone additive
>>> help?
>>>
>>>
>>> Max
>>> _______________________________________________
>>> quattro mailing list
>>> quattro at audifans.com
>>> http://www.audifans.com/mailman/listinfo/quattro
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>