what is the difference between an open or closed deck engine. i see a lot of talk about them, but no explanation. could some one help

rob

 

Open and closed deck refers to the cooling of the block and cylinders. In an open deck the cylinders are completely surrounded by a "water jacket" which is great for keeping cylinder and piston temperatures down. In a semi closed deck, instead of being one uninturupted water jacket there are large water channels with reinforcing bridges around the cylinder. In a closed deck there is no water jacket whatsoever. Obviously the trade of is cooling (prevents detonation, allows for higher cylinder pressures) for block stregnth (in an open deck, too high cylinder pressures can warp the cylinder sleeves). A semi-closed deck is a good compromise, in fact in my integra (which comes with an open deck) i am running golden eagle sleeves, which save the water jacket, but are ringed by supportive ridges which brace the sleeve agaisnt the block.

edit: heres some examples

This is a stock WRX block, notice the water jacket. This is an open deck.

Here's a small block ford, straight up closed block, no frills hunk of metal right there.


Heres some golden eagle sleeves so you can see what I was talking about, notice the ridges around the outside of the sleeve braced agaisnt the block. This is pretty much the same idea as a semi-closed block, except in a proper semi-closed block it is cast with ridges like that going right up and down the legnth of the sleeve.

 

thank you for clearing that up for me (and others that might not have known).

rob

 

Hello,

Using Subaru blocks as an example:

Open:


Semi-Closed:

Note the extra metal around the outside of the cylinders at the 12 and 6 o'clock positions.

Closed:

Note the extra metal around the outside of the cylinders at the 12, 1:30, 4:30, 6, 7:30, and 10:30 o'clock positions, pretty much surrounding the bore.

All pics taken from Cobb Tuning's webpage. They offer semi and fully closed deck blocks for WRXs and 2.5RSs.

Semi or Fully closing the bore is most important to allow higher RPMs safely. At higher RPMs, the cylinders will tend to move around and the pistons can crash into them. By closing the deck, you reduce the amount the cylinders can move or deform from cylinder pressure.

Fully closing also offers significantly more gasket mating area and can make the gasket much less likely to blow, a good thing only if you've got strong pistons and a strong head.

Joel

 

Joel,

Great pics and the wording to bring it all together. Thanks!

Richard...
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Sorry to raise the dead on this 3yr old thread, but I thought somebody else may read this and get confused...

While what he says is true, he fails to mention that the closed-decked engine in question (ej22t) has oil squirtters to keep the pistons cool (as does the closed-decked 4g63t if anyone cares. I know this because I have bothe engines in my garage). This more than makes up for any loss of cooling from block design.

It is also important to remember that the change in block design (to the open deck) had to do with changes in casting process. It was done to save money and to increase consistency in production, not for cooling.

 

Does anybody know if the JDM '02MY Version 7 motor is semi-closed deck? Thx

 

crap sorry just saw this
its semi closed and here is some other stuff
w00t bug eyes!!

Forged bottom end (crank, rods and pistons)
8250 rpm redline
No TGVs
Sodium filled exhaust valves
AVCS