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3mm or 4mm Silicone Hose

9K views 11 replies 6 participants last post by  rickerlove 
#1 ·
Hi,

Quick question - when replacing the vacume hoses around the engine, is it best to go 3mm or 4mm hose? I have 3mm all over but I am sure I have read recently that 4mm is what it should be?

Cheers
 
#3 ·
is it best to go 3mm or 4mm hose? I have 3mm all over but I am sure I have read recently that 4mm is what it should be?[/b]
Whoever told you it should be 4mm does not know what they are talking about. The standard hose is about 3.5mm internal diameter.

4mm may be more likely to come off than 3mm. I see some people have to fasten theirs with cable ties.

3mm hose on my car for last five years and never an issue.
 
#8 ·
I prefer 4mm personally- I find that 3mm is a bit tight over some of the nipples, especially the dump valve. This increases the risk of splitting, as although silicon hose is very flexible, it's less elastic than rubber. I'm quite happy with a cable tie as extra security.
 
#10 ·
I've got Ø3mm hose throughout, for most (if not all) runs, there is little airflow per se, only enough to equalise the pressure from one end to the other. Change in pressure is not a sudden (in terms of engine management) occurence happening over a relatively long period of a few milliseconds
the difference in flow area . the main restriction to flow is in reality the diameter of the hole on the bit the hose fits fits. which, when you think about it is way less than the diameter of even the Ø3mm hose. The biggest restriction is this hole which doesn't change, irrespective of what diameter hose you use.

The efect of hose diameter on flow is not an issue really in this instance
 
#11 ·
Thanks TB, thats the best answer. And also the 3mm is about 20% cheaper. I've used a mix of 3mm and 4mm without any problems - Most of the original vac hose was intact but the hose connecting to the Fuel pressure regulator was just about ready to fail. Don't toss away the orignal OEM stuff if it is still good (hang on to that if you can).

I used black silicon because I don't like all those colours but was tempted to use something like white just so I could tell at a glance if something blew off.

I've also heard recently that the Silicon hose can shrink over time and that got me a little paranoid. I'm going to write some manufacturers to get a straight answer before asking here in the forum :crazy:
 
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