Burning question about G13

300k_logician

Well-known member
Joined
Feb 24, 2018
Location
Kansas. The middle of nowhere.
TDI
2000 Jetta ALH 5-speed
Greetings.


(I apologize if this is in the wrong forum. I'm not sure where to put this, but this seemed most appropriate, considering that I'm testing an ALH)


For those of you who don't know, I'm presently acquiring education for the servicing of heavy-duty diesels. Sometimes I raise my hand in class to ask about why my VW is different, and typically get the answer, "because it's a VW", which does not satisfy my curiosity.


Following a lecture on cooling systems, where we learned about cavitation erosion, and all the various OAT coolants out there, I had a burning desire to test my coolant with test strips, so I went out and bought a kit.


(This kit in question is NAPA part #4107, it's a drop-shipped WIX heavy-duty diesel coolant test kit.)


When I tested my coolant, and also some spare G13 I had (as a comparative test), they both came out with ZERO nitrite!


So how DOES G12/G13 protect against cavitation? Please enlighten me. I know that G12/G13 were engineered quite well, but what exactly is it? How does it work?


And... do the turbo vanes create exhaust backpressure to reduce air/fuel ratios to speed up engine warm-up under idle conditions on the ALH? 'Cause DI diesel engines, according to the material, will never heat to operating temperature at idle unless airflow is restricted somehow. Do they default to 90-95% closed like the heavy-duty VGT's that the textbook discusses?


Thanks y'all:)!
 

Nero Morg

Top Post Dawg
Joined
Oct 19, 2017
Location
OR
TDI
2014 A6 TDI, 2001 Jetta TDI, 2014 Passat TDI
They are accurate about heavy duty diesels not wanting to warm up at just idle. Most, if not all, diesels are cold blooded engines.

As for cavitation, that's mostly prone on engines that have poor cooling efficiency. Yes, it CAN happen to our engines, but the cooling system is so effective that it's very unlikely. I'd expect to see it more on a poorly maintained 7.3 IDI versus ours.

Another difference our engines have that is shared with all modern diesels, is having a surge tank, rather than a coolant overflow tank. The coolant is constantly flowing through the aeration lines to the surge tank. This added flow helps the engine dispel heat better. As compared to an engine, like a 7.3idi, where it has the pressure relief cap on the radiator, with no extra resivoir, and an overflow. There are no anti-aerstion lines present. So hotter areas, like around cyl 7, are prone to cavitation.

I'm sure there's other points I've missed, but just to get the conversation ball rolling.
 
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