Cooling Tins

Some clarification would be good.

Most engines (as delivered) come with the 36 hp "doghouse" shroud. Is this what you have, or do you have stock VW, or something else?  

Stan

It is the doghouse style. 

It would seem that heater boxes are great heat sinks for pulling very hot air away from the heads and sending it to cabin or if heat is off --- dumped forward of engine for release to the air.  To support this in past - Jake Raby found that blocking the fresh air tubes makes the engine run hotter.

The sleds also speed up hot air and exit to the rear of car.  J tubes can get red hot - you'd think you would need some way to concentrate an air flow on them on them so it doesn't increase heat of the heads.  Folks don't seem to like those type 3 cooling tins (called super cooling tins) but it would appear they help circulate air (concentrated and at higher speed) around the bottom of the cylinders.  Sleds would help expel that air out the rear of the engine.  That seems logical?

If you want to keep the doghouse shroud, Clark Callis from Awesome Powdercoat can set you up with flaps, sleds, etc. to fit. Clark is in Ohio, and is a good dude. He can get you set up.

There are some guys over on theSamba who have replicated OG VW shrouds, and are selling them (click this link). This is kind've a big deal, because decent OG shrouds are not as easy to get as people would have you think. These are not cheap re-pops-- they sellers have gone to no small expense to have them made.

I'm running a DTM from Jake Raby, but LN Engineering bought the Type 4 Store, and rights to the DTM was part of that, so LN sells them now. 

I'm still thinking that 9.5:1 is going to be pretty high for a W120, no matter what you do. If you pay attention to cooling, I don't think it'll head temps that gives you problems, it'll be the detonation. 93 octane isn't likely to cut it, and you'll likely have to end up backing off your timing somewhat. 

I bought my VS last fall.  During this winter, I've been running with the cabin vents wide open.  

Since the summer is almost upon us (out west, hee, hee), i'm ready to self-martyr  with the vents open.  But, if the vents are closed, does the hot air get re-directed and dumped out to the environment?

i get all of the oil cooler chatter, but this seems like an area that you can optimize cooling for the heads.

"But, if the vents are closed, does the hot air get re-directed and dumped out to the environment?"  YES

The control flaps are either side upper part of picture.  (Suspect this is why CMC seals off either side of the front of the engine bay).  So even in the summer when heat is not used the engine cooling fan sends air over the exhaust tubes cooling them while with J tubes its just mostly air under engine.

8Yhis is a T4 but you can see it better (to air exit arrows to left)

Wolfgang

I don't think my current setup has the control flap.  Do I need to add them?  This car is mainly a nice weather car and not driven in the winter.  Are the control flaps use when starting a cold engine to not have the cold air from the Fans blowing on the cylinders?  If so, at what temperature do they need to be closed?

The control flap is usually part of the heat exchanger (except on T4 and they are a separate piece).  Do you pull a lever to regulate heat - usually by emergency parking brake?  If so it controls this valve.  I guess you could just have the slide heat controls in foot well which regulate foot or defrost.  If that's case, not sure where blocked air goes (well it would be to defrost if hooked up). (Some with old VW wire the valve to cabin heat as the control wires rust/break/lock up).

Thanks @WOLFGANG! great diagrams!

Wolfgang

Yes we have a knob we turn in the cabin by the parking park to open heat.  Our car is a Beck and has some kind of fan that sits on the firewall shelf.  I bet that is the heat exchanger.

The heat exchangers are part of the exhaust system - sort of a pipe within a pipe.  The inner pipe has the hot exhaust (yellow in Greg's/Wolfgang's figure) while the outer pipe has fresh air passing through picking up heat from the inner pipe.  The fan is just to boost airflow.

Type 4 motors have a standard fan in the engine compartment before the heat exchangers. It is supposed to come on when you engage the temp lever. Might be effective in a Speedster, but not worth a **** in a Bus. I had a 912E with that set up and the fuse for the fan was always blowing. In Canada the buses and type 4 sedans all came standard with a BA6 gas heater. I got one from a junk yard in Vancouver and put it in my bus years ago. 

Stock Type 1 heat exchangers are tiny. Guys say they are 1-3/8", but they're not-- they're restrictive by design.

They were perfectly adequate for a de-tuned 1600 making 50 hp on a good day, and a huge choke-point for any performance engine. Choking off the exhaust will without a doubt make it run hotter.

Getting over the heat-exchanger fixation is the first step towards a free-breathing engine.

I have "high performance" heat exchangers that are (I believe) 1 5/8". But they don't have the fins that help hear the incoming air, so the results are, um, tepid at best.

Stan

I am not going with the heater boxes.  Tiger is building a sidewider with center exit for me.  Not sure how long its going to take him.

I also have one of Tiger's Sidewinders, but you are probably smart in skipping the heat exchangers and saving the $$$

Lane Anderson posted:

I have "high performance" heat exchangers that are (I believe) 1 5/8". But they don't have the fins that help hear the incoming air, so the results are, um, tepid at best.

EMPI flanged heater boxes are 1-1/2". The 1-5/8" are big money (really big money), and available from Tiger.

99% of the guys wanting to run heater boxes are going to use stock-ish boxes that are size-tiny. Telling them they'll run cooler with them is true in the abstract only-- it assumes that the engine is sized and tuned to use them. That means about 50 hp, which means that overheating isn't going to be an issue anyway.

I used to obsess about this. I had a car with a deliberately undersized engine because I wanted heater boxes. When I had the IM coach built, I speced a gasoline heater. I wouldn't do that again, either. It's a lot of complexity, and a bomb sitting in my lap.

These cars are fair weather conveyances. Doing it again, I'd get seat heaters and a 12 v electric blanket and skip any heat whatsoever. For everybody else-- run the exhaust that best matches the engine and lets it breathe freely. Spend the $1000 you'd have to give for big heater boxes (that don't really do anything) on something nice-- like seat heaters, some blankets, and a good shroud.

Seat heaters are a must as it makes the top down driving season longer and for real heat get a subie engine, and roll up windows ..... now you can go into December if you have no snow.  

Stan,

ok, so what you're saying is: ditch the cabin air that we get from the fan that's blowing on encased, hot oil because we care more about over-heating the heads than luxuriating in dubious, engine air.  so, straighten the pipes, take a shot of whiskey, put on your big boy pants and act like you gotta pair.  

that sounds about right to me....

WOLFGANG posted:

It would seem that heater boxes are great heat sinks for pulling very hot air away from the heads and sending it to cabin or if heat is off --- dumped forward of engine for release to the air.  To support this in past - Jake Raby found that blocking the fresh air tubes makes the engine run hotter.

Fresh air tubes? If you are talking about the tubes that come from the shroud down to the heater boxes then I have to ask why would blocking them make the engine run hotter? It would seem like blocking them at the shroud would keep more cool air going down to the cylinder fins. The hot air going down to the heater boxes really has no place to go if you have the flaps in the closed position so I block mine off at the shroud in the summer months and have gotten positive results.

And Stan - I have 1 5/8 boxes on mine!

Lane Anderson posted:

I have "high performance" heat exchangers that are (I believe) 1 5/8". But they don't have the fins that help hear the incoming air, so the results are, um, tepid at best.

     I have the same ones Lane has but mine throws out some decent heat. Plenty to warm the cabin on a 40 degree night with top up but no curtains. I think with the curtains in it would handle 30 degrees. Thankfully I don't need to test it.

      I bypassed the frame ducts and ran some decent black hash to the pvc rocker pipes. It seems to hold more heat in and transfers it well because I get a real strong blast of air out of the floor vents

Rusty - That was from a study of shrouds that Jake Raby did years ago.   Impossible to find that complete study online anymore.  (I know he spent lots of hours on that study so it is his intellectual property so justly so).  If you look in the shroud photo I posted you can see welded fresh air outlet scoops that direct air to the fresh air vents.   I'm sure the internal air flow is disrupted by them - is it a big deal? - probably not but that 25 cents of metal was put there for a purpose years ago along with the other vanes in the OEM shroud.  A lot of VW testing and engineering went into it. Maybe they should be removed?  I'd love to see a shroud designed for North Africa - I'm sure it has a different internal vane design.  (The 181 Thing has no heater boxes (gas heater instead) and its vanes are different from other VW shrouds). Ironically, many of the cheap aftermarket 36hp center mount shrouds completely leave out the internal cooling vanes.

Comments (see source below) about Jake Raby's T1 DTM study:

When Jake was doing T-1 DTM development he was measuring both open and blocked fresh air hoses. His testing on shrouds he said that the fresh air outlets still needed to flow some air in order to keep the proper airflow through the shroud. This is because the heater outlets were designed to constantly leak some air and the factor shroud was designed for maximum flow with this in mind. Completely blocking off the outlets apparently, disrupts the airflow to the cylinders in some way. He was apparently able to back this up with pyrometer data.

This is from an old 2008 ShopTalk thread - heck someone even proposed drilling hole it the fresh air plugs as compensation to the air flow turbulance!

http://www.shoptalkforums.com/...hp?f=18&t=142663

Bypassing the frame is the key!

majorkahuna posted:

Bypassing the frame is the key!

Troy suggested I do this when I bought my car and what a difference. My wife uses the heat on cool evenings and when she opens her side vent I can feel the blast on my side. VERY powerful stream of VERY warm air.