Doing the silicone hose job this week and I've read a few threads about it. I'm generally ready, but I have one question before I get started.
How can you tell where to use 3.5mm hose rather than 4mm?
That's a small difference when looking at something old and worn

I was surprised to not find a list anywhere (or markings on the colored diagram) showing what the size of each hose is

 

99% of the solenoids and vacuum rack will take 3.5mm. Some of the nipples like the turbo actuators are slightly larger and 4mm fits better here. Its pretty easy to tell if it fits snug enough.

 

I used all 3.5mm except the pre-control/wastegate actuators and boost controller solenoid.

 

I recommend 3.5mm everywhere for the smaller lines. The turbo control actuator and boost control lines are 6mm.

People used to use 4mm as that was the only size available. It doesn't fit as nicely and usually requires the lines to be zip tied and/or glued, which is ridiculous. Proper fitting lines will be VERY tight and will never pop off or fail.

I recommend boostcontroller.com for hose, they are reasonably priced, thick wall and quality.

If you wanted to get super fancy there could be spots where 4mm will fit, but I've never felt the need for it.

Dale

 

Thanks guys
I got my hose from boostcontroller.com, so it is good stuff
Looks like the 4mm stuff can just sit until I need it for a random project. I got 40' of 3.5mm, so it should do the trick

 

I'm trying to plumb the purge control valve and catch tank right now, obviously I can't use silicone due to fuel vapors but I'm having trouble finding the right size line that will fit on both the catch tank end and the solenoid/check valve. Are these specially made hoses with different sizes on each end or am I missing something?

 

I was just looking at my purge control yesterday actually and thought the same thing. I did Google a few sites and they said silicone is good for that area. It isn't flowing fuel so it should be good. I'm going to use it.

 

If you use good quality silicone hose (the stuff from boostcontroller.com applies) you won't have problems with fuel and/or oil exposure.

The problem is a lot of the myths around silicone hose date from 15+ years ago. Lot of hose back then wasn't sized right, had thin walls that would kink, would split on the end if you didn't cut it right, turned into goo with exposure to oil, etc. I've seen that stuff in person. Modern hose won't have any of those problems.

I've used silicone hose for a long time on oil catch cans with no problems. Not the best setup, but it does work. Viton is better, but really the only place I recommend Viton is the catch can and that's it. It's too stiff, doesn't fit as well, and is really pricey and flat out overkill on all the other vacuum lines.

Dale

 

Appreciate the insight Dale, this really saved me a lot of head scratching. All the silicone I've put on my car has been from HPS so I think I'll give it a try