Engine block
A couple of days before Christmas the engine from US finally arrived to me after a long trip over the North Atlantic Ocean by boat.
My engine builder started disassembling it and was surprised as one cylinder had a large amount of gearbox oil in it.
Squirting a minor amount of oil in cylinders to act as protection during transportation is normal but not pouring it in.
Engine was advertised as a plug and play unit by the seller, if we had fired it up it could have hydro-locked and done some bad damage to rods, crank, bearings.
Luckily we had no intentions of running this engine stock
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Contacted the seller and he refunded me a fair amount of money for the trouble, thankful for getting some money back as the import taxation fees where greater then wished for.
During an extended period of time I've been collecting information on forums and in Elsa to understand the differences between the 2.5 NA and 2.5 TFSI engine block.
It's been stated on forums that they are 95% identical besides the slight different combinations of metals in the iron cast.
As there's no summary of this on the web I figured I'll share my knowledge in this post. Pictures are not mine, just used as reference.
The major differences are on the rear of the block. For those of you that are color blind, I'm sorry for this visualization method...
Red - Right hand side knock sensor mounting location is higher. When I detected this difference a couple of weeks ago I got stressed as I thought the knock sensor location on my 2.5 block would prevent me of installing the OEM turbo.
After a test fitting of the 2.5 TFSI head on the 2.5 NA block with the turbo I was relived. Knock sensor is physically not interfering with the turbo
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I'm not certain of the reason for the re-positioning done by Audi on the 2.5 TFSI engine block but presumably it's because of the heat from the turbo.
Will specifically ensure to protect the knock sensors from the heat with heat wrapping. Alternatively the re-positioning can be due to the measuring cylinder knock capability but I think that less likely. Thoughts are welcome on the topic.
Orange - Turbo coolant feed. I'll machine/drill/tap into the same location on the 2.5 block as the cast is available.
Blue - Turbo Oil feed. I'll connect to the 2.5 TFSI head instead.
Yellow - Turbo oil return. I'll drill and tap into the block just below in the threaded cast part of the block.
Brown - Mounting point for the turbo hot air outlet tube. I'll secure it in another way.
Pink x 2 - The support bracket for the angle drive utilizes these positions. I'll have to re-design the bracket to fit the 2.5 NA block mounting points.
Purple x 3 - Mounting points for a metal heat shield protecting the cables and knock sensors from heat. Won't be needing that, I'll wrap and protect the cables in another way.
White x 2 - Used for the mounting of the turbo coolant return pipe. Not crucial...
On the front of the engine block there's only one deviation.
Blue - One of the coolant thermostat mounts is not available on the 2.5 NA block. Will produce a bracket that utilizes the mounting point on the left hand side as support.
One final difference, the water pump. The 2.5 TFSI water pump (housing diameter of the water pump) is larger. Thereby the block has a larger internal water pump diameter to fit the larger pump.
I could have it machined but I've decided against as I'll compensate the cooling with a auxiliary oil cooler and a larger cooler radiator. More on this topic further ahead in my build.
My conclusion, overall internal and external block design is identical when you see them as complete units but the accessories mounting points and connections are different.
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