Catch Tank Rule Problems - VW Porsche and others please comment

[Bob Roth]

In reading the proposed 9.3.15, I think its going to cause a lot of problems. Before I send this note to the CRB, can you Porsche and VW guys comment on your cooling systems. I know you have external pressure relief tanks, but I don't know if there are drain fittings on them. I don't think there were for Saabs. Also, I don't even know if there were pressure relief caps on them for sure. Please comment and mark up the proposed language so we get the best rule possible.

GCR
Item 1. Effective 3/1/09: Insert a new section 9.3.15 and renumber subsequent paragraphs:
Coolant Catch Tanks Cooling systems shall be equipped with coolant catch tanks with a minimum capacity of 1 US quart.

I think it needs to be reworked to clarify its intent as in regards to what is required and when this rule is applicable.

I assume the intent of 9.3.15 is for water cooled radiators, having a pressure relief cap, whose neck has a hose fitting for conduit of steam and fluid to a safe location. Most modern cars today have a catch tank of the type required by this rule, but some such as my '66 mustang had just a dump hose. For a '66 mustang and other cars with a pressure relief and neck with hose fitting, this rule is clear and easy to implement.

There are several cases where it is not so clear and easy;

1) The rule does not tell what the tank should be hooked to; I believe there are examples of cars where the radiator system has a separate pressure relief tanks of a quart or larger vapor space to capture coolant expansion. I believe its common practice for these systems to have no hose fitting in the pressure relief neck. I do not have the ability to confirm this, but I believe that 1980's Saab 99 and 900's, some VW’s, and Porsche 924/944s all have systems of this type.

If there are cars without hose connections, I think it becomes very difficult to implement this rule with the alternatives being
- Replace the OEM pressure relief tank with custom tank that has a relief fitting. (Expensive and difficult because this would be a custom built pressurized reservoir with multiple cooling hose connections)
- Replace the OEM pressure relief cap with one that has a built in relief fitting. (I don’t know of any available)
- Shroud the neck of the pressure relief cap and plumb that to a catch tank. (I think there would be space interference with the hood as the tank is at the top of the engine compartment)
To eliminate this problem, I recommend allowing pressurize relief tanks as an alternative to catch tanks as long as their vapor capacity is 1 quart or larger. (Note; the one quart rule may be tight for Saab and VW’s.)

2) The rule does not define what cooling systems this applies to; Does this rule apply to any fluid cooling system or just the engine radiator cooling system?
- My water cooled race car has an oil cooler as part of its lubrication system. It’s also
common for lubricant heat exchangers to be added to differentials and power
steering systems. As these systems are closed and have no external pressure
reliefs; how, where, and for what purpose would I connect the catch tank to them?
- My car has a cool suit system. How and where do I connect a catch tank to it?
To eliminate this problem, I recommend that this rule only apply to “radiator cooling systems with an pressure relief” per the GCR definition of Radiator.


I don’t think its SCCA’s intent to put catch tanks on oil coolers or make it very difficult for Saab and Porsche drivers to conform to the rule. As such, I think this rule should be held and studied further. An option to address my above concerns that SCCA may want to consider would be modifying 9.3.15 as follows
Radiator Coolant Catch Tanks
Radiator engine cooling systems having a means of pressure relief shall have either a pressure relief line connected to an coolant catch tank having a minimum capacity of 1 US quart or a pressure relief tank within the cooling system that has at minimum 1 US quart volume vapor space between the normal liquid level and the relief device during operation.

[Greg Amy]

Bob, a couple of points.

- First, "coolant", in most common-usage of the word, refers to the water-based portion of the engine cooling systems. There's no intent here to apply this to anything else.

- Second, the intent of this rule, as I read it, is to ensure that open, blow-off systems, such as what's on most 'Merican cars, have tanks of sufficient size to capture all coolant that may bleed when the engine gets hot. Volkswagens do not have a "catch tank" per se; the V-dub (and Audi and presumably Porsche) system is a fully-enclosed, flow-through system. The plastic tank you see is nothing more than a convenient reservoir/expansion tank, and is actually part of the cooling flow circuit.

I see no application of this rule to either lubrication oils nor to flow-through systems such as the VW/Audi example. At worst there may need to be a simple edit to the proposed rule that this would not apply to fully-enclosed, non-blow-off, flow-through systems.

GA

[tom91ita]

is the section number referenced right? it said to add 9.3.15 but there is already

9.3.15. CRYOGENIC TREATMENT
Cryogenic treatment of components is allowed unless specifically prohib-ited in the category or class preparation rules.

am i in the wrong spot?

[Greg Amy]

GCR
Item 1. Effective 3/1/09: Insert a new section 9.3.15 and renumber subsequent paragraphs:

...

[Gary L]

Volkswagens do not have a "catch tank" per se; the V-dub (and Audi and presumably Porsche) system is a fully-enclosed, flow-through system. The plastic tank you see is nothing more than a convenient reservoir/expansion tank, and is actually part of the cooling flow circuit.
GA

But if there is a pressure cap (and therefore, a relief orifice) on that expansion tank, the rule would apply just as surely as it would to the pressure cap and overflow tube on top of Bob's '66 Mustang radiator. I agree that the wording of the proposed rule could use some work.

[Greg Amy]

But if there is a pressure cap (and therefore, a relief orifice) on that expansion tank, the rule would apply just as surely as it would to the pressure cap and overflow tube on top of Bob's '66 Mustang radiator.

Why?

The designed intent of Bob's Mustang's overflow tank is to bleed excess liquid coolant overboard due to expansion, because there is no expansion area inside the cooling system. Bob's V-dub, on the other hand, is a fully enclosed system, built with expansion area internally (in the properly-named "expansion tank"), thus is not intended to blow off liquid at any time. Unlike on his Mustang, his V-dub's "radiator cap" (actually, the "expansion tank cap") is not intended to allow air/liquid to escape ever except as a point of last resort to keep other parts from failing (such as a radiator hose).

To require a "catch can" in such a system is analogous to requiring a "catch can" for all other parts of the system that may fail (such as a radiator hose catch can).

But, if the rule is enforced to the letter of the law, then Bob's system is, in fact, illegal because it does not actually have the required "catch can". And to require one would negate the functions of the system (actually - to the letter of the rules if you want to get picky - it doesn't say that catch can has to be attached to the cooling system...)

[Gary L]

Why?

The intent of Bob's Mustang's overflow tank is to bleed excess liquid coolant overboard due to expansion, because there is no expansion area inside the cooling system. Bob's V-dub, on the other hand, is a fully enclosed system, built with expansion area internally (in the properly-named "expansion tank"), thus is not intended to blow off liquid at any time. Unlike on his Mustang, his V-dub's "radiator cap" (actually, the "expansion tank cap") is not intended to allow air/liquid to escape ever except as a point of last resort to keep other parts from failing (such as a radiator hose).

To require a "catch can" in such a system is analogous to requiring a "catch can" for all other parts of the system that may fail (such as a radiator hose catch can).

But, if the rule is enforced to the letter of the law, then Bob's system is, in fact, illegal because it does not actually have the required "catch can". And to require one would negate the functions of the system (actually - to the letter of the rules if you want to get picky - it doesn't say that catch can has to be attached to the cooling system...)

I would have to assume the purpose of the proposed rule is to help keep coolant off the racing surface. To that end, the fact that the V-dub expansion tank is not intended to allow liquid to escape, will be of little consequence when something goes wrong. It's no different than the '66 Mustang, it just takes another lap or two for it to happen. And possibly even less, if the system was inadvertently overfilled.

[itracer]

the fact that the V-dub expansion tank is not intended to allow liquid to escape, will be of little consequence when something goes wrong... And possibly even less, if the system was inadvertently overfilled.

So you want me to drill a hole in my closed system and create a weak point so that I can prevent something that hasn't happened yet? I think we should require coolant catch tanks on air cooled beetle too. There is no breather valve on the VW system. So there is no place to vent it from. To do so, would illegally modify the cooing system IMHO.

[joeg]

In my car's stock application, the Rad resovoir is open--hose from rad filler neck just drapes itself into the resevoir (half of which is the molded windshield washer tank!).

What can I do with this new rule. Scrap my washer tank for a nice aluminum rad overflow tank???

[pfcs]

Quote:
Originally Posted by Gary L
the fact that the V-dub expansion tank is not intended to allow liquid to escape, will be of little consequence when something goes wrong... And possibly even less, if the system was inadvertently overfilled.

So you want me to drill a hole in my closed system and create a weak point so that I can prevent something that hasn't happened yet? I think we should require coolant catch tanks on air cooled beetle too. There is no breather valve on the VW system. So there is no place to vent it from. To do so, would illegally modify the cooing system IMHO

The late VW spherical tanks have a countersunk area where the cap recesses; in that recess is a drain passage the comes out the back of the sphere as a rectangular opening 1/2"x1". If the vehicle overheats badly, SOME of the void comes out this irregulayly shaped opening (its a "spherical rectalangle"). Only an asshole should be required to connect a hose to it.

[Gary L]

So you want me to drill a hole in my closed system and create a weak point so that I can prevent something that hasn't happened yet? I think we should require coolant catch tanks on air cooled beetle too. There is no breather valve on the VW system. So there is no place to vent it from. To do so, would illegally modify the cooing system IMHO.

If you have a pressure cap (by that I mean one that is designed to open at a pre-set pressure), you already have a hole in your "closed system". Consequently, it is no different than the '66 Mustang setup... when something goes wrong, it is going to piss coolant on the track. By design.

[Greg Amy]

If you have a pressure cap (by that I mean one that is designed to open at a pre-set pressure)...

They're not designed that way, Gary.

The VWoA group uses an expansion cap with a one-way valve, designed to allow air *in* when in vacuum, but block exit of any liquids, gas, or pressure *out*. I only mentioned the "last resort" for the cap because that's what typically fails first (if you don't pop a hose). I've link a photo at the bottom.

But this is not necessarily germane to the conversation. I think Bob's point is that we now have a requirement for a "catch can", a catch-all (har-de-har) rule that doesn't necessarily apply to all systems. I was simply pointing out that the rule was not intended to apply to systems such as the VWoA's; you certainly don't want to hack into these systems to add a catch can, it would be problematic, dangerous, and flat stupid.

If anything, the rule will be enforced intelligently, i.e., tech inspectors will recognize this rule doesn't apply to these systems; if not then it will need to be adjusted accordingly. - GA

[Gary L]

They're not designed that way, Gary.

I agree... but what you've pictured is not a pressure relief cap. And I would agree, that type of system should not require a catch tank.

I'm referring to those systems that have an expansion tank with a normal radiator pressure cap on that expansion tank, designed to relieve coolant pressure at a preset value. I suspect this is the very type of system that Bob R. was referring to in his original post, when he brought up the Saab, Porsche, et al. I know I can certainly point at one car that has such a system. I race it... the ubiquitous Volvo 140.

[Greg Amy]

I'm referring to those systems that have an expansion tank with a normal radiator pressure cap on that expansion tank, designed to relieve coolant pressure at a preset value.

Roger, I agree. That's what this new rule is designed to address. But, it throws out this all-encompassing, all-assuming net...

BTW, Porsche's system is the same as VW's; in fact, many Audi and Porsche expansion tanks are actually the same part number as a Volkswagen Rabbit's (VW, Porsche, and Audi all share common engineering roots)...

GA

[JeffYoung]

I've only scanned some of this, so forgive me if I am off base.

My car has a radiator without a cap, and a hose to an expansion tank which does have a cap. The expansion tank has an overflow hose that dumps to the ground.

My read on the rule is that it is simply trying to prevent the latter, which I agree with -- overflow coolant should go to a 1 quart overflow "tank" (or Gatorade bottle as the case may be) with at least 1 qt of vapor space. And that is what I shall do -- just run the overflow line to a one quart Haterade bottle.

On the VWs, you aren't dumping coolant anywhere by the very design of the system and while I agree that doesn't fit "nicely" within the rule, since it is clear from the design of the system that coolant "overflow" isn't going going to ground, then all seems to be ok (to me anyway).

[Gary L]

I've only scanned some of this, so forgive me if I am off base.

My car has a radiator without a cap, and a hose to an expansion tank which does have a cap. The expansion tank has an overflow hose that dumps to the ground.

And the system that I am referring to is like yours, but there is no hose, nor a nipple for same... simply a hole in the neck of the tank that is uncovered when the cap relieves pressure at the preset value.

Greg - I may be wrong, but I would almost bet if you go back far enough, you'll find the same system (as my '71 Volvo) on the German cars... an expansion tank with a regular radiator pressure cap on the tank instead of the radiator. As I said in my first post on the subject, the wording of the proposed rule could use some work.

[Greg Amy]

Greg - I may be wrong, but I would almost bet if you go back far enough, you'll find the same system (as my '71 Volvo) on the German cars...

Believe it or not Gary, VWoA has used the same exact general design from the very first water-cooled VW, the 1974 VW Rabbit. In fact, the expansion tank was the same exact part number from that '74 all the way through all the A1 model lines (Rabbit, Scirocco, Jetta), gasoline and diesel. The only differences were tank and radiator shape and size for chassis-specific placement, like the longitudinal placement in the Dashers, Audis, Porsche 924/944, and the space requirements of the A2 Golf chassis onward...and all through it they used the same exact expansion tank cap. Hell, my 2000 S4 still uses a variant of that same exact design and I'd not be surprised if Audi and V-dub still do it for new stuff today.

In fact, this system is so efficient that many other pure-race cars use Scirocco radiators and expansion tanks...

I will admit I haven't seen an early 1970's Audi 100Ls in probably 20 years, but if someone is racing one of those then the cooling system is the LEAST of their worries...

[Gary L]

...and all through it they used the same exact expansion tank cap.

Then someone needs to tell the suppliers about this.

Here's what the internet parts places seem to think is the correct tank for the early (I checked '77-82) Porsche 924, and it definitely does not appear to have the screw-on cap, rather the pressure relief type I'm talking about. Like Jeff's tank, this one even has a nipple to hook up an overflow hose.

[shwah]

Gary, that nipple on the filler neck connects via hose to the radiator. The larger bottom nipple connects to the water exit of the head. Yes that is the VW system, and yes it is fully closed.

[pfcs]

This is the A3 VW expansion tank and cap. The 2 hose nipples are for circulation. There's no way to plumb a recovery tank that is sensible. As far as I know, these caps relieve pressure @15-17psi. They do in my shop when the pressure tester is teed into the system.
EDIT-see tank on next page