yoeddynz

As per the title this next stage of building the exhaust silencer/muffler/back box/ take your pick has taken much more time and effort than I had always expected.

I started by taking the blue imp apart.  To Woolf valley garage I went....

..where I removed (rusty mild steel) exhaust, bumper and rear valance..

Popped it onto rusty imp shell...

Now I knew exactly how much room I have to play with.

Whatever I was going to build had to work with several things.

I wanted the box to be mounted higher than the existing one behind the Datsun engine as I was sick of scraping it on steep driveway exits.

It had to be built completely of stainless steel, no exceptions. No more corrosion.

It had to look tidy and fit within the bumper line, tailpipes excluded.

The tailpipes were to be twin centre exit. I had a very specific look in mind and they have to be just right.

It had to be quiet enough and yet still sound sporty. This last one is tricky and will most likely need modifications to get right hence the last design point...

It has to be modular, easy enough to disassemble and repack with sound deadening (most likely glass fibre)

Now I knew the size I could build it to I started by making some flanges. This so I can unbolt the flexible sections between the V clamps and the box. Made to suit the 44mm tube as per the tube off the V clamps.

Lifted the big folder we'd made onto the bench top and folded up some 1.2mm stainless. Although heftier than I could have used I've gone with this thickness to helped avoid the tinny sound thin stainless boxes can make.

I wanted perforated stainless tube but couldn't find any within NZ. Got some perforated sheet instead - again 1.2...

Which I cut strips from and formed up into tubes as such...

Welded...

Now I had the start of a box and some tube. I could sit down and nut out a design. I have had some basic ideas for ages on how it might look inside but it was really good to sit down and see how it might work. Drew some ideas up..

Nutted out something I think would work well and be easy enough to change if need be. Time to commit. I had to cut some blue steel. First actual act of modification to the imp in my quest to plonk a flat six in it.

Now I could double check box sizing and weld the flanges in place.

Folded up the second box side..

Complete with captive nuts to suit a lid..

Tail pipe time. I almost went with twin 2" exits but they were just a tad too big. Settled on twin 45mm.

Tacked them to yet another stainless pair of flanges to work with the modular design aspect. Happy with the look I then fully welded them on the inside.  The flanges will be sealed with a soft copper gasket.

Happy I had the look right I cut the centre top from the box, created a recessed bit and carefully welded in the second threaded flange.

So now I have inlets and outlets where I want them and just have to connect the dots. 

Ideally a nice long a route to dampen sound while keeping it as smooth flowing as possible.

Plus, as per original brief,  it has to allow for easy disassembly and re-packing.

There was quite a bit of head scratching with this bit of the build but eventually I sorted a design out.

I cut various bit of sheet and put big holes in them with a nice brand new holesaw set.

Made little boxes with more big holes...

Shaped bits like a heart...(#putmyheartandsoulintoit.....)

Welded the ends onto the main box, curved in bit to help with flow and also hide the external bobbin mounts from view a little.

Now I had a collection of parts that would come together and form a london underground of tubeways for the exhaust gases to follow.

I was pretty happy with the layout for its potential silencing effect.  However I now wondered if it might just end up being a touch too quiet and restrictive.

Luckily I had come up with an idea early on where I could add some valves. Quite a little bit of extra work involved but the more I'd thought about it the more I was convinced it could work well. With this in mind I had built the middle chamber width to allow for some valves and made sure they could be removed to fit said valves in place.

I cut some 44mm holes in the middle chamber lids and made some to valves to suit...

Whipped up a little press form to create brackets..

Valves mounted.

Underside of lids have the heart halves which help direct flow from one tube back too the next, or up and out through the open valves..

Valve shafts stick out through back of box. Sealing will be by a combination of spring loaded fibre and silicone washers.

Now for an exciting point in life that every shed 'Barry' looks forward to.  Emptying out those boxes of little random fittings that have been stashed away 'just in case you might need them'...

Such fun!  I selected my (stainless!!!) treats and scribbled on some alloy.

Made lots of alloy swarf..

Ended up with these levers. Pinch bolted to the shafts along with added grub screws. The short length of threaded rod will be changed for a long length of stainless rod, actuation method from within the car yet undecided. Possibly a 12volt door lock motor etc or maybe mechanically with a bicycle cable.

Recessed the backs to allow for seals..

So yeah. Lots of parts! Compulsory photo of thing exploded into many bits...

All together now with some arrows. Remember each side is just a mirror of the other side (there is a small cross over hole in the centre plate that separates the sides)

Valve closed...

Valve open...

I think it'll be quite a difference in sound and look forward to hearing it.

Valves can be seen in action in this very exciting video...

So It's pretty much complete except for the mount points which I'll do once I've got some bobbins from engineering shop along with seals. The lid will be sealed by running a bead of silicone which I'll let set before clamping the lid down.

Oh I weighed it too. I was worried it might end up quite hefty but it will be only about 6.4 kg once all the bolts are in/packed with fibreglass..

The box will be painted satin/matt black leaving the tailpipes shiny. Silencer mounted in place...

View from above showing plenty of room for the valve linkages in place.

I ended up cutting a tiny bit more of the valance away so there's room for a stainless heatshield.

I then covered the valance with some masking tape to help prevent it getting too scratched while I put back in some internal strengthening and capping it all off. I'll also be adding mount areas for the bobbins.

I'll remove the engine next and add in the big multi-pin connector to the engine loom.

Then I'll be seriously very close to removing the Datsun engine and cutting out the under seat area just as I have on this rusty shell.  Wow!!