Debated with friend... 3/8" ID hose & 1/2" OD barbs vs. 1/2" ID hose

[Petra]

Hey guys! I thought that this was kinda interesting and maybe worth mentioning....

Last night I was talking with a friend and we ended up getting in a little debate over which was better or if there was even a real performance difference between using 3/8" ID hose with normal 1/2" OD blocks or using 1/2" ID hose with the same 1/2" OD blocks. He was saying that using 1/2" ID hose was pointless because blocks with 1/2" OD fittings only have an ID of 3/8" which would mean that the flow is restricted at that point and, because 3/8" ID hose is easier to fit into a case, it is best to just use 3/8" ID hose on blocks with 1/2" OD fittings. I was basically saying that even though the ID of the barbs is 3/8", the 1/2" ID hose allows more water to get to that particular barb in a given amount of time compared to 3/8" ID hose; thus, allowing coolant to move more quickly from block to block and to the rest of the parts in the system--resulting in a slight performance advantage.

Now, uhh, who was right...?

...Also, how much of an advantage is there really with 1/2" ID hose over 3/8" ID when using 1/2" OD barbs?

 

[beast]

Seems like the system as a whole would be limited by the narrowest point. If you have 1/2" ID tubing, and a 3/8" ID block (or at least a block with 3/8" ID barbs), then the overall flow would be the same as if the whole system was 3/8" ID. The water would appear to be moving faster thru the 3/8" portions than the 1/2" portions, since flow is how much volume is going a certain distance over a certain period of time.

Since water doesn't compress, the same volume of water is always moving thru the system at any given point in the system, and that's limited by the most restrictive section.

 

[weapon--]

tell your friend that while he may be a masterdebater (rimshot please), 1/2" with 1/2" is better than 1/2" fittings with 3/8 ID tubing...

weapon logic:
--unless you have an H2O loop that has nothing other than perfectly straight sections of tubing, you will get some compression at the points in the tube where it has to curve. 3/8 ID will have a smaller ID at those points than either the 1/2" fittings or the 1/2" tube.
--the ID of 1/2" fittings is not uniform across the market. some have larger than 3/8" ID. you can take a drill to the bastages as well.
--a system with 1/2" ID tubing will hold a little more water than one with 3/8" ID tubing - more water is better.

 

[mustang_steve]

Even 1/2" barbs are not 1/2" ID, so for 3/8" ID a 1/2" OD setup (like swiftech used) is an ideal situation wince the 3/8" line is only restricted byt the internal block design and not the connecting interface.

That also reminds me I have to hunt down some more speedfits for my radiator and res sometime to remove some more restrictions.

 

[Petra]

Originally posted by weapon--
weapon logic:
--unless you have an H2O loop that has nothing other than perfectly straight sections of tubing, you will get some compression at the points in the tube where it has to curve. 3/8 ID will have a smaller ID at those points than either the 1/2" fittings or the 1/2" tube.

Good point, I hadn't thought about that one before....