home made heat exchangers?

[johnfevs]

Hope my old ones were of some use to you

[BOXY]

Take it you've had no problems with the silicon?

The silicone is easy to route around the drive shafts and fits the outlet on the heat exchanger with a bit of persuasion. With it fitted I get +60'C out of the windscreen vents after 20 minutes driving.

[Cheeky V]

johnfevs yes they have been very useful!

So, I have now acquired a pipe bender for stuff up to 50mm thick (aslong as its packed with sand before hand) so I'm kinda thinking it would be better to make everything from Exhaust manifolds all the way back to the triangle joiners at the silencer out of stainless (the ones i have are pretty scabby now). Now I want to have functioning heat exchangers, the shell of them is no problem! but what I cant figure out is, what do I use for the fins inside the exchangers? the original stuff is fairly brittle and im not even sure what its made of! so any ideas of what i could put inside them to help transfer more heat to the air passing through (larger surface area than just the pipes)

Cheers

[CovKid]

What you want is this stuff. You just need to find out who does it:

http://image.made-in-china.com/2f0j00mC ... angers.jpg" onclick="window.open(this.href);return false;

This company do it but as for suitability and price.....

http://www.turnbull-scott.co.uk/industr ... nned_tube/" onclick="window.open(this.href);return false;

[Cheeky V]

So really I just need some ally sheet to stamp out a load of individual fins, then slide over the pipes and tac them in place!

Cheers CovKid awesome idea, I'll contact that company to see how much they can do it for anyway

[marlinowner]

With a name like Turnbull-Scott they just had to be in the Sottish Borders. And yes they're in Hawick, 15 miles down the road from me.

[CovKid]

If you scroll down on turnbull scott page you'll see what I meant. I can't see it being practical making individual fins.

So really I just need some ally sheet to stamp out a load of individual fins, then slide over the pipes and tac them in place!

[Cheeky V]

No you're probably right would take an age! but couldn't I cut a few spirals out of the sheet and stretch it over the pipes so its like an auger screw, would mean alot less cutting and could then adjust how dense the fins are?

Had another look and a few of them look like this is what they've done

[T25Convert]

Hi,

Looking at the Turnball Scott page, they don't appear to be welded / stuck on, but wound on under tension.

To get optimum heat transfer I would have thought that the flange would need to be in continuous contact with the pipe, so just tacking on a spiral may not give you the heat transfer you'd be looking for.

This http://www.thesamba.com/vw/forum/viewtopic.php?t=227245 shows what VW did (plus as an interesting aside what a copy looks like!) Could you aim to replicate this - the fins run longitudinally rather than radially.

Good luck, interested to see what you come up with!

Cheers,

Alex

[Cheeky V]

Alex I think you're right, the fins will def need to run along the manifold so that more air passes between them and the added surface area is more use, if anyone knows what material VW used for the fins that would be awesome but it looks like its going to be a bit of trial and error working out how many metal fins will be needed (they will also need to be seam welded so there is more contact with the manifold). think I may need to test the original material to see how much heat is transferred from it to the air because I don't want to cool the exhaust to much otherwise there wont be any heat to send up to the cab right?

also think it was CovKid that said on another post that the type 4 requires some back pressure, don't suppose anyone has some ball park figures?

Have ordered some steel angle to make up a small jig to build the new manifolds/exchangers on, I have square exhaust ports so I will either need to get some square/rectangle box section to weld on the end so that it will mate properly or to re shape the round pipe to fit, anyone have any thoughts on this? the triangle-ish plates that the silencer bolts too I will just cut from appropriately thick sheet so that won't be a problem.

anything else anyone can think of?

Thanks for all the help with this guys, plenty of pics will be coming your way!

[Cheeky V]

Another question, does anyone know the size of the exhaust manifold studs? Cheeky V's need replacing as they are pretty crusty.

Built/building my jigs and using 3/8 stud for that as the mounting holes that are on the original manifolds are that size. I guess so that there is a bit of play for fitting them/poor castings, which will mean that once I've made the set on the jig they should fit no problem! [touch wood ]

[CovKid]

8mm

[sarran1955]

Hello,

Interesting thread..

When you cut apart old heat exchangers.. you find that the exchanger bit is a cast finned aluminium piece bolted round the steel hot tube..

If you are doing these in stainless..then why not TIG weld 6 longtitudinal fins of (say) 2 mm plate straight to the hot tube..

From experience.. the better the VW heat exchanger the more fibreglass (?) lagging is bonded onto the inside of the steel outer cannister.. to stop the heat escaping to waste..

Often all that is holding the rusted thing together..

If you make up the outer box nicely.. it could be in 2 bits ....riveting together with the lagging pre bonded..

Photos of jigs would be nice..

Cordialement,

[Cheeky V]

Cheers CovKid

Hi Sarran, Actually making the first set out of mild steel as I've not worked with stainless and wanted as few new experience on the first try as possible

I didn't realize they had the fiberglass lagging in them! was watching someone making a silencer the other day and they used a similar material to pack that out with which gave me the idea you've just outlined

Will definitely make the outer jackets from 2 piece's in case i need to add/remove more fins. anyone have a exhaust temperature meter fitted? I don't want too cool the pipe down too much because the colder the exhaust is, the denser the gases will be in it which then wont be helping the engine to breathe properly.

I shall post up the first jig, its not pretty but its functional

[Cheeky V]

3mm thick angle iron with 3/8 stud for the mounting holes, pretty scrappy welding (gasless mig wire) but its very solid!