Which vac lines carry or pontentially pass small bits of oil?

 

no one metioned that silicon hoses kink very easily.

 

There are both positives and negatives of nearly every elastomer known. None of the big chemical companies have come up with a material that will fit all needs. They have come close but there is always a certain application where the material fails.

As previously stated in the other thread (https://www.rx7club.com/showthread.p...ighlight=viton)

Most expensive to least are:
Viton, Silicone, Nitrile

Best fluid resistance to least:
Viton, Nitrile, Silicone

Highest temperature resistance:
Silicone, Viton, Nitrile

Longest life:
Silicone, Viton, Nitrile

Test for oil resistance---
Oil resistance, Test Method D 471, 70hours @ 212ºF
Change in hardness
Chane in tensile
Change in elongation
Volume change

Results---
Silicone
0 to -10 points in hardness (softens)
-30% Tensile (loses strength)
-30% elongation (tears easily)
0 to + 15% swell

Viton 70hours at 400ºF
± 5 points in hardness
-25% Tensile
-20% elongation
0 to + 5% swell

Because our bread and butter is silicone we have sold many kits for the RX7 using this material. We have put a lot of time into designing a compound that will have superior physical properties than the competitors, have a stronger thicker wall thickness and kink less.

I think one of the members has said it the right way. If you plan on keeping your vehicle and have the money Viton is the best way to go. If it is outside the budget and/or you may not keep your car for 5+ years go with silicone.

There are aromatic hydrocarbons circulating within the system. I assume that there are cases where some engines may have more than others. Viton truly is plug and play for vacuum lines. Silicone on the other hand will need to be inspected occasionally. I would suggest at least looking inside the hose ends at least once a year. You are looking for the overall softness and appearance of the hose. If it appears to be "sweating" or have any oily residue on the outside, the oil is permeating through the wall. Silicone has a very high permeation rate compared to Viton and some other polymers. You want to make sure and look for oil within the hose itself. If the hose is cracking or splitting it will happen from the inside out. Also the most common place for this to occur is on a tight radius.

There are many different grades of silicone. This industry is not controlled by what we put in our compounds and extrude the tubing. Silicone is one of the few rubber materials that can actually "recycled" in a way. You can grind silicone down to the consistency of flour and add it back into a vigin base. A lot of companies due this to lower their raw material costs. We only use 100% virgin platinum catalyzed silicone compounds in our products. The use of re-grind as it is called, will lower the physical properties of the silicone yet have the same appearence.

Viton is another material that isnt really controlled. It comes from a family of elastomers called "fluoroelastomers" which contain fluorine. Many people sell fluoroelastomer but in order to say it is Viton, the base material must come from DuPont-Dow. This is the material we use in our Viton hose.

Confusing I am sure to some but if you have any questions fire away and I will do my best to answer them ASAP.

Jim

 

I'm a mechanical engineer, and I referred to my materials resources and nothing he has said yet doesn't agree with the 'book'. He's one of the few aftermarket resellers who doesn't inflate claims or blow smoke.

Dave