sprbxr

The previous owner of my 951 removed all of the hard plastic vacuum lines and replaced them with soft silicon hose. Since buying the car I have had problems with hitting the overboost protection. I am going to rplace the hard lines anyway but I was just wondering if this could be part of my problem.

Justin

Perry 951

The silione lines are better than the hard lines, and cheaper. As long as you use good fittings, there should not be too many issues.

The line to the WG is close to the header, so I could melt. Check it, and the connection to the wastegate.

If all looks fine, the cycling valve or WG could be shot.

Hans

There should be a reason for Porsche to use the hard lines.

Does anyone know what material it is made of?

Standard soft silicone tube can handle -51 to + 238 deg C (-60 to 460 F) so should be fine in this respect.
but what about chemical resistance?

Internal diameter should be 1/8 (please correct me if wrong!!)
What is the outer diameter you guys use? 1/4? or 3/8?

Thanks

IceShark

Porsche used hard lines because they are cheaper and take up less space.

Standard silicone is attacked by various petroleum products so you don't want to use it for oil line. But for vacuum line it should be just fine for the small amount of oil in the air system from turbo blowby. There is a lot of it in use in turbos for this purpose without reported problems.

One thing you do want to make sure you get is thick wall tubing - it can take more vacuum without collapse and will stay on a fitting without using hose clamps when under boost.

The common reported problem is blowing unclamped lines off hose barbs when under boost. RX7s seem to have this problem. The solutions to this are to use heavy wall tubing and make sure the ID is small enough. Otherwise you need to clamp or wire tie.

You can use I.D. size 5/32" (4.0mm) or 3.5mm. The 3.5mm can be mighty tight on the 5.0mm+ barbs. 1/8" might be a little too tight for some of the hose barbs. The heavy wall stuff, which is harder to find, has a wall somewhere between 0.100" and 0.125". Standard wall thickness is about 0.065".

Hans, have you used 1/8" ID heavy wall (3/8" OD) and been able to get it over the larger barbs without much trouble?

Hans

Not yet, got some line with 3.2mm ID / 6.4mm OD and will test this weekend.
Let you know on monday morning.
Have a nice weekend

IceShark

Hans, that would be the equivalent (within a few thousandths) of Purosil's standard thin wall 1/8" hose. I haven't tested that size/wall thickness.

I will be interested in how it fits over the larger 5+mm hose barbs and if you think the thick wall version (twice the wall thickness) would also fit.

Also, do you have a vacuum pump? See if that hose will pull almost a full bar (say 0.8) of vacuum without collapsing. And burn a piece of the hose and see what sort of ash you get. If it is the good pure silicone grade the ash will be white. If it is lower grade and filler has been added the ash will be dark to black. There is a lot of crappy vacuum hose coming out of Asia for the RiceBoy crowd.

Thanks.

You have a good weekend, too.

Perry 951

I got all 5/32" hose, and brass connectors and have had no problems at 20psi of boost.

Many of my hard lines were cracked when I did the rebuild, so it got all new lines from 5/32" to the big stuff at the intercooler. (about $350 worth, but it looks and works great)

You are right about the thick wall stuff. If you order some of the good silicone lines, have the retailer send you a small sample of each size that you will order.

Tabor

Perry,

Where did you get yours from?

Perry 951

Hose Techniques

I asked for samples of all the hoses that I wanted to buy. They sent them out next day. Prices are pretty good. 15ft of the 5/32" (3.5mm) will do almost all the small stuff, and the larger ones for the intake boot lines and such took about 9 feet (6mm and 8mm varieties) They also have a pretty good price on the large intercooler boots.

Oh.. and the brass fittings I got from a local race (rice) shop.

IceShark

Do you know what you really got from Hose Techniques? 5/32" is their 4.0mm. Their 3.5mm is another size. Back when you bought this, Hose Techniques did not have heavy wall available in 5/32"/4.0mm - that was .065" wall thickness. But they did have thick wall ~ 0.100 in what they call 3.5mm.

Perry 951

I am not 100% on the wall thickness of the small diamater hoses I got (it was the 3.5mm, and the brass hose barbs for 5/32" vac lines fit very snug.)

I compared it to a sample my brother had sent me from his car. (2001 Hadman TFX Top Fuel Dragster, Keith Black 500cid Hemi running 40+psi, Nitromethane, and 7000 HP... oh.. and buy Fram Filters. Try the Triad filters.. and Fram Filters for life. Oil, Air, Tranny, Fuel, Fram has them all.)

Perhaps the plug will give them some luck next year and save me a seat on the line. And Skip.. you cannot have my car.. I am still waiting for yours!

The wall thikness was just as thick as what he had.

If it is good enough for them, it is definately good enough for me!

IceShark

Perry, you related to Bill Clinton?

We got no clue what you really have. Though it seems to work unlike some of your rebuild nightmare so enquiring minds would like to know!

Take a ruler to a chunk of the stuff and give us the readings. Please.

Hans

Done, fits smoothly without any lubrication, hard job to get it off again though...
Got the hose from an industrial supplier, would expect some quality here but will burn anyway.

Can do a vacuum test but this will take time.
The shop at the works will have some pumps to test in a couple of weeks, will sneek this test in and give some results when done.

Industrial supplier could be Cole Palmer.
They have a huge program of tubes in a wide varity of qualities, are relative expensive though. Look for perestaltic pump hoses there.

IceShark

Hans, I thought you might have one of those Mighty-Vac brake fluid suckers. They are handy for all sorts of extra projects like this. I believe industry standard for SVH is to pull a minimum of 25" of mercury, so a bit over 0.8 bar, without deflecting the walls over 20%.

Wow, Cole-Parmer? That is lab and medical grade stuff ... we don't need that! I found the tubing you must have got and the price is a little high at $75 for a 50' roll. One could get that retail in non medical grade for under a buck a foot. And the medical grade is not "better" hose as you probably know. Record keeping, testing, etc.

BTW, what sort of T's did you use? I have not been able to find any small brass (or stainless) Xs, only Ts. And the Ts in 3/16" (a little under 5mm) have two very short ridges on the tube fitting to act as barbs. Not a robust barb configuration you see in larger fittings. There are robust barb fitting available in nylon, but I don't think plastic is the way to go.

keith

perry - can you remember the exact sizes and lengths you ordered?

I would like to do the same.