Precups and 18:1 ?

[coxfmly]

I searched the archives for messages about Precups and after reading a few this is still a mystery to me.
What exactly are they and what are they used for?
Are they something you change or upgrade?
Also, is 18:1 the magical number for diesel compression?
Yes, I am very new "green" to the diesel world.
Thanks ......

[Dieselboy]

Welcome to the page.

Our engines have 21.3:1 compression, and that's largely as a result of GM wanting easier starting and better naturally aspirated performance. A drop to 18:1 or 19:1 allows for more fuel and boost to be added before reaching the limit of the heads' clamping force.

The prechambers are little cups in the head where the injector fires. The combustion begins there, and rapidly expands into the cylinder. Different prechamber sizes will do different things to power and fuel economy. Larger "T" cups allow for more power, but sacrifice economy. Smaller NA cups are found in 6.2Ls and are setup for economy.

[TimK]

Welcome aboard. I personly believe oil burning vehicles are the only sane way to drive. Here is a link to another website to check out. http://tdiclub.com/TDIFAQ/ The TDI club website mainly focuses on VW turbo charged direct injection diesels where on our site of course we focus on indirect injection GM diesels. However, their FAQ section has a lot of good basic informaiton on diesels, oil, fuel, fuel gelling and maintenance. It's good reading if you're just getting into diesels. You will also see a lot more folks on that website talking about running WVO and VO which is waste vegtable oil or vegetable oil.

Of course knowledge is power. Here is one more website to check out that also focuses on diesels. http://www.mercedesshop.com/shopforum/forumdisplay.php3?f=15 This forum focuses a lot on the Mercedes diesel. A different engine and each engine type has their own idiosyncrases but the basics are the same. I would send you a link for the TDR - turbo diesel registry that caters to Cummins engines but you would probably start reading that and realize that the Cummins are a near perfect diesel engine and when you realize you don't have a Cummins and it gets depressing.... well, why go through all that anguish.

Good Luck.

TimK

[coxfmly]

Thanks for all of the information. I will bookmark the site and check them out later.
Since my engine was NA and was upgraded with a turbo later would it be safe to assume that the precups on my truck are the smaller size? If so is this the proper way to go?

Thanks again.