Hey guys-

Just food for thought...

The time has come to do a vacuum line change. I think I may have found a semi-cheap alternative: high-pressure braided nitrile rubber lines. You can get 9/64" (3.57mm... just about perfect!) from McMaster-Carr for $0.91/ft.

The part number is 5394K13 - see it at www.mcmaster.com.

It's oil and gas resistant, has EXCELLENT abrasion resistance from the braiding, and (from previous experience on German cars) tends to "hold on" to nipples over time very well (thanks to the semi-rigid nylon layering around it).

For me, personally, silicone is out of the question - IMHO, it splits far too easily at the slightest hint of abrasion, oil, gas, etc. I recognize that lots of people have really good success, yadda yadda yadda... lots of people have "good success" with anything. I'm still not going to do it... the engineering design tradeoffs aren't good enough for me. It takes ~10yr. for the effects of heat to get to the stock nitrile ones, so the extra temps of silicone aren't that great of a tradeoff IMHO.

Of course, Viton is great, but that's a pile of money... something else is bound to go wrong on the engine before a new set of braided nitrile hoses goes bad :-).

Whadda ya think?

Take care,
Shad

 

I came from the air-cooled VW world and we aways used this stuff. It's easy to work with and holds up well.

I think the reason most people wind up going (to the extreme) with silicone is because they feel that the first 60k miles on their car has hardened the rubber lines so they need something "better." It's a PITA to replace all of the lines in the first place so might as well try to avoid having to get back in there any time soon.

In addition, if I was paying someone to do a hose job ($500) I could more easilly justify the cost for rubber lines (~ $50) versus silicone (~ $150).

Mazda used rubber vacuum lines. No reason you couldn't too.

 

The stuff you suggest has a pretty large bend radius. Kinking could be an issue, especially under the UIM.

 

Yes Viton has the best resistance to oil, fuel, and temperature. It is extremely expensive compared to other organic compounds.

Nitrile is a trade off. It does have the resistance to fluids I.e. oil and fuel. However the degradation temperature starts around 250ºF. We have the ability to test per several ASTM test methods. The affects of excellerated heat aging on nitrile are, hardened hoses which lose 40% of tensile, elongation suffers around 25% and durometer (hardness) can increase by 15-25 points.

There are alternatives however. Silicone is generally a weaker (tear, tensile, and elongation) material than the above listed polymers. There are several different grades of silicone though. Most companies sell peroxide catalyzed silicone. This is what 90% of people currently purchase. The alternative to a peroxide system is Platinum catalyzed silicone. All of the physical properties are increased by about 40-50%. The temperature range far exceeds EPDM and Nitrile, and is equal to Viton.

I can tell you from experience McMaster Carr is not known for selling high quality products. Did you know that all I have to use is 51% base of any polymer to use its callout. For example, I can use 51% Acrylo-nitrile, 30% EPDM, 15% neoprene and 4% SBR and still call it "nitrile"! EPDM and SBR suck for fluid resistance. Neoprene is "Ok" but nothing near nitrile.

Just adding my .02 here.

 

I got plenty of really high quality silicone hose for $50, I dunno what you're talking $150 about.

 

Hello-

Kinking isn't that problematic... I dunno if you've had much experience with braided ubber lines, but they are REALLY hard to kink... pretty stiff.

BTW, another simple reason why I will not use silicone... how many OEM's use it? Zilch. Nitrile? Tons. Viton? Tons ("fuel injection" hose!). They have millions and millions of dollars in research... that's more than everyone here put together. No offense intended... but sorry :-).

Again... it takes ~10 years for the nitrile hoses to finally have problems with heat. Odds are that 10 years from now, my engine will have to be rebuilt anyway, at which time I can cheaply replace all the lines very easily. <shrug>

Take care,
Shad

 

Hello-

So did I... have you heard of LN Engineering (www.lnengineering.com)? They make ultra-high-performance components (i.e. out of most people's price range :-) for aircooled Porsche and VW engines (and some Corvairs). I was the cofounder of that company... I was the "L" :-). I gave it over to my partner (the "N") and now am back living the life of the poor grad student!

Take care,
Shad

 

I wont get into a pissing match with anybody about polymers here. I make silicone, Viton, EPDM, nitrile and neoprene in any shape or form. However I will say that car manufactures dont always put the "best" item on an engine from the factory. They have a trade off from performance and cost. The price that "stealerships" charge you on some replacement items is rediculous. A lot of times the margin is sooo much better to sell a replacement part. So they make "wearable" items that they can sell in the parts department.

I was just making a point that nitrile may not be the solution to all problems. There are other alternatives available. I will see if I can run a heat aging test on nitrile for everybody here. Also the low temp brittle point of ACR (nitrile) is very mild around 0 to -10ºF. That means any flexing around this temperature can cause spliting and cracking.

Wall thickness has a lot to do with all of the things we have just talked about. What is the wall thickness everybody is currently getting on their lines? The reason why I ask is, that I have several thousand feet of nitrile and silicone in stock. I am trying to get rid of all of the nitrile because its shelf life is only 3-5 years per the government spec HDBK-695. Silicone shelf life is 20+ years per the same spec. When the part actually goes into use, the service life is much lower than the spec above.

 

No, I hadn't. Been out of that work for 5 years or so. Looks like you guys put together some nice products there.. Too bad that the market for air-cooled stuff, at least here on the east coast, is either for the diminishing market of racers, or for kids who are broke. I was down at the shop today actually (Peek Performance in Lanham, MD) and was reminded of the ghetto-ness of much of the customers.

..Sorry for off-topic post.

 

Hello-

Unfortunately, you are correct... the VW aircooled scene is huge, but primarily consists of cheapskates. There is an upper echelon group, but it's kinda small. We started out in VW and very quickly included Porsche... there's a lot more money there :-).

Take care,
Shad

 

High Temp Silicones, I think I just bought some of your stuff. I bought the silver in 4mm and 6mm if you remember. Ayways, the stuff looks awesome. The wall thickness on the 4mm is great too and is very hard to kink. Great customer service as well.

-Aaron

 

Aaron,
Thanks for the praise, I do my best to make sure people are taken care of. I was always buying from other companies and wanting to be treated with respect if I didnt know about something.

Anyway I am glad you like the hose. The silicone you purchased was Platinum cured and will resist kinking like no other silicone on the market. Have you seen our new products?

 

60k miles & 5 years later....
Silicone hoses still holding.
No kinking.
No ripping.
No degregation. (I have removed the UIM off 3 times)

Just thought I'd share

 

I realize there are potentially better materials for vacuum lines, but silicone is an excellent compromise between performance and cost.

 

So H.T.S,
Gimme your web addr. I guess when I do the silicone hose job, I'd be interested in the Platinum catalyzed silicone. Do U have a 3rd gen? If so, you tell ME the length and wall thicknesses. Ballpark prices are..??

Sounds like 2a+Ron is happy with 4 & 6 mm. In addition I'd like some for the air pump - ~3" long, about 3" bend radius, maybe tighter, about 1" I.D.

TIA
Jeff

 

HTS,

Almost forgot.... Black please.

J

 

If you guys want the best, hands down, get DuroBlu.

If its good enough for airplanes its good enough for cars. Mil spec says it all....

I have NEVER seen another silicone hose meet mil-spec.

You can purchase it by the foot here: www.rxforyour7.com

 

hightempsilicone.com is the address. We are in the process of building our website. I have sold to several other members of RX7Club.com. One of your memebers found us on ebay believe it or not. He wanted a kit that was equal to the hosetechniques kit that was selling for $153.00 + Shipping. I put together a a special package at that time for $80.00 + Shipping for a kit that had more 3.5MM and 4MM than the hosetechniques kit.

I am now working on some red, black and blue intercooler hoses for another member. So the name is getting out a little bit.

For those of you that like to buy hosetechnique stuff, ask the owner who makes his vacuum hose for him??
I know everything you need to know about silicone and I dont have to go ask anybody what it does.

And by the way, we make mil-spec hoses. I can give you a whole host of specs on any polymer. If Viton is the hottest thing I will try to price all of the vacuum hose sizes out of Mil-R-83248C Ty2 CL1 (Mil-spec Viton) just dont ask to do it in colors. Viton will only color black, brown or off-white (dirty white). Also Viton is for high temp applications and will crystalize at low temps for those who live in extreme weather areas.

 

At what temperature does Viton crystalize?

 

Hey I have your Viton kit and it kicks ***! Good service and good people. If there is intercooler hoses coming maybe a group buy?

 

I too purchased the VITON kit from HTS, and couldn't be happier! Sure, the cost is high, but what ISN'T on an FD?

After working with this stuff, I love it!

 

So viton is the best all around(except for price?) followed by nitrile, then silicone, then rubber? I have the rubber ones on my car now and Ive split a few. For some reason I always thought silicone was good stuff but someone here mentioned it splits w/ abbrasion? I really dont want to do the hose job....uhg.

 

It has an operating temperature of -15F to 400F, and can handle brief periods at 500F. If abraded, has lower tear resistance.

Silicone is similar, but has less resistance to oil/fuel degradation. If abraded, has lower tear resistance.

Nitrile has an operating temp of -20F to 220F, but is resistant to fuel/oil.

Neoprene (stock material, I think) has an operating temp of -20F to 212F, and isn't resistant to much. But it doesn't tend to abrade or tear, rather, it hardens in the heat and breaks.

Dave

 

Just for grins I put a piece of 3.5mm VITON in the freezer and left it overnight, along with a digital temperature/humidity tester. Freezer maintains 6 degrees and 51% humidity, the VITON was simply unaffected...it was merely cold, and was still flexible.

 

IMHO, I still don't see the rationale behind going with viton. I have been using quality silicone lines for YEARS now (like closing in on 10 years) with NO problems. No splitting, hoses popping off, whatever. They just work, day in, day out. Easy to remove for service, too.

There are a few lines that it's smart to use Viton on, though - I do concede that. The lines for the PCV system see a lot of oil, and it will degrade the silicone over time. I have actually used silicone on PCV lines before, and they've just gotten soft and expanded a bit - no dramatic failures.

You just don't get the cost benefit by going to Viton. Period. It does work well, but it's extra money you could spend fixing something else on the car.

Dale