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TDI Power Enhancements Archives on TDI Power Enhancement related items.

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Old November 23rd, 2007, 06:32   #91
StingrayRT
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ok, guys I work together with most famous engineer which has a responsibility for F1 pistons, which have a full support to MMC pistons (now is banned in F1).......I know what I do so please - no fairy tale
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Old November 23rd, 2007, 10:45   #92
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Could you then please write a few comments about my post?
There are some complicated things in DI combustion process and maby you have cnowledge to tackle them?
My english is some times really crap so if there are something that sounds really stupid, then I can try to re-write it =)
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Old November 25th, 2007, 15:02   #93
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ok !!! i am confused now!!! can some one please show me som 1.9 tdi pistons that some one have put in with lower cr and did work well, and measurements... and can someone make my pistons and of course get payed!!! please pm me
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Old November 25th, 2007, 15:42   #94
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Someone was going to I assume ..

correct me if I'm wrong
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Old November 25th, 2007, 15:55   #95
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i know what stingrays thinks have pictures of his pistons ! cant just aford racing pistons right now!!!

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Old November 26th, 2007, 21:04   #96
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Quote:
Originally Posted by TDIMeister
Unfortunately it's more complicated than that. There is no rule-of-thumb that can be applied for all engines, but rather depends on a lot of factors. The Porsche 997 GT3 engine has a compression ratio of 14.6:1 using European Super-Plus spec pump gasoline (!!!) Other race cars in the same class have found their optimal CR at lower values.
Hey David, these Gt3 engines, are these factory race engines? As far as I know gt3 engines from the factory are 12:1 compression. 14.6:1 would be sick!
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Old November 26th, 2007, 21:32   #97
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I am referring to the September 07 issue of Race Engine Technology magazine as my source of information. The factory GT3 is not one and the same as the FIA GT3 racing class, although the race cars are based on the factory GT3.
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Old November 26th, 2007, 21:34   #98
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So this was for the FIA gt3 class than?
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Old November 26th, 2007, 21:37   #99
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Yes.
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Old November 27th, 2007, 15:28   #100
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Updated links to pictures on suggested piston machining here.

Take any advice at your own risk.
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Old December 5th, 2007, 08:45   #101
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Ok so the question is what are you using to determine how much to remove? What are the formulas? If you remove squish area versus bowl area does this change anything in the formula? I need to do some calculations on 2.5l pistons so any info here would be great.
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Old December 5th, 2007, 10:15   #102
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Calculate the ccv of the piston you have in cc's. Use the proper formula to calculate the cr you want from the one you have. That is how I did it. It seems to be about 3cc's fluid volume difference in stock bore to drop compression to where I want it.
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Old December 5th, 2007, 15:17   #103
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What he said above. ^^^^^^^^^^^^^

A 1.9 TDI has a swept volume of 474 cc per cylinder. To achieve a geometric compression ratio of 19.5:1, it would have to have a total clearance volume at TDC of 25.62 cc. This volume includes the bowl, valve pockets, ring land volume, squish volume... EVERYTHING. The only way to accurately measure this is to cc the combustion chamber. The most common way to do this is by titration of a liquid (usually thick motor oil) directly to the engine.

Within the parameter of compression ratio, there is another parameter particularly applicable to DI-Diesel engines known in engine development circles as the "K-Factor". This is defined as the ratio of the piston bowl volume alone to the total clearance volume. The consensus is that a high K-Factor is desirable (large percentage of the clearance volume belongs to the bowl).

To reduce the compression ratio to, say, 16.5:1, you need a total clearance volume of 30.58 cc if the swept volume (bore x stroke) remains the same. It's obvious that if this all of the increase in the clearance volume comes from the bowl, the K-Factor increases (this is good).

How did I determine where and how much to remove material from the bowl? By visualizing the angle of the spray coming into the bowl from the injector nozzle and imagining a flow field in my mind, and not wanting to spray against any walls but rather in an area of high flow velocity (even though we don't have the benefit of performing CFD, it helps to have seen countless CFD visualizations of in-cylinder flow fields for a DI-Diesel piston bowl to get a rough idea).
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Old December 6th, 2007, 10:26   #104
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Perfect thanks guys. I didnt get a chance to read this and the other thread yesterday...
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