welding project Juular's Scandi Noir. Volvo C70, 240 &122. Earth day.

[grogee]

On 02/09/2024 at 13:17, juular said:

I've also started taking steps to sort out the annoying exhaust drone.  I picked up one of these decibel killers from the same manufacturer as the exhaust itself. It just hammers into a straight section and acts a bit like a hemholtz resonator in that it bounces soundwaves back up the pipe.

Curious to know if this works. My Maestro is too loud inside, especially on a cruise. I was thinking of maybe just getting a custom stainless system made up with the brief of 'not loud but still fast'. But that is obviously spendy.

Do they do different diameters? Where did you get it? 

[juular]

14 minutes ago, grogee said:

Curious to know if this works. My Maestro is too loud inside, especially on a cruise. I was thinking of maybe just getting a custom stainless system made up with the brief of 'not loud but still fast'. But that is obviously spendy.

Do they do different diameters? Where did you get it? 

In summary, and as @Supernaut suspected, it didn't do much at all.  It may well have reduced maximum decibels and be measurable on a sound meter, but in terms of how it feels, I haven't really noticed any reduction to the boominess..

Here's the one I bought. They do different diameter ones, although their web shop is not that easy to find things on.

Jetex Exhausts Ltd – Decibel insert [2 inch] [aluminised steel] L=280mm

I'm not really sure where to go next with this.  I've sealed up every join on the exhaust with foil tape to eliminate leaks as the cause, and it's definitely the deep bass emanating from the backbox that's causing the problem.  I'm also considering handing it in to an exhaust place and saying 'fix it'.  I get the feeling a backbox with more restrictive baffling would solve it, and if I lose a few BHP, I feel this engine has plenty to spare so I'd be fine with it.

[Supernaut]

1 hour ago, juular said:

In summary, and as @Supernaut suspected, it didn't do much at all.  It may well have reduced maximum decibels and be measurable on a sound meter, but in terms of how it feels, I haven't really noticed any reduction to the boominess..

Here's the one I bought. They do different diameter ones, although their web shop is not that easy to find things on.

Jetex Exhausts Ltd – Decibel insert [2 inch] [aluminised steel] L=280mm

I'm not really sure where to go next with this.  I've sealed up every join on the exhaust with foil tape to eliminate leaks as the cause, and it's definitely the deep bass emanating from the backbox that's causing the problem.  I'm also considering handing it in to an exhaust place and saying 'fix it'.  I get the feeling a backbox with more restrictive baffling would solve it, and if I lose a few BHP, I feel this engine has plenty to spare so I'd be fine with it.

I ended up buying a standard spec back box for my 323i, I should have done that 3 years ago.

I now have a Powerflow back box sitting in the shed and nobody off gumtree wants to buy it.

[Sunny Jim]

Great sleuthing getting to the bottom of your electrical problems - hope additional earths do the trick.

[juular]

15 hours ago, Supernaut said:

I ended up buying a standard spec back box for my 323i, I should have done that 3 years ago.

I now have a Powerflow back box sitting in the shed and nobody off gumtree wants to buy it.

This is what I thought about doing, but since the new exhaust is much larger bore than the original I'll need to find a standard exhaust off something else.  Anyone know which cars have a 2 inch exhaust as standard?

[juular]

My head has not really been up for much of anything at the moment, but I took some time yesterday to chuck a couple of new earth straps onto the Amazon engine to see if it sorts the electrical fault.

I don't know how much the positioning of earth straps matter as long as they go to a bit of chassis or body, so I have attached one between the alternator bracket and front panel, and between the exhaust manifold and bulkhead.

Interestingly I noticed that where the throttle bar is resting against the stop, there was a bit of wear that looked different from normal mechanical wear, which is perhaps the smoking gun that some arcing has been taking place there.

I did try to take it out a run, but it wasn't for starting. Eventually tracked the problem down to the ignition points gap having closed up so far that it doesn't break contact at all.  I reset the gap, but by that stage I'd drained the battery, so it got plugged in to charge and left where it is.

I tried to remember when I last set the points gap or did any routine maintenance on the igition bits, then realised that I haven't done anything since the car went on the road which coincidentally is about exactly one year ago! So that's a bit of a milestone in itself. Happy birthday.

If the earth straps solve the electrical fault, then I'm down to just two non-urgent things to fix on this car. 

Firstly, the boomy exhaust which still does my nut in.  I'm thinking the first step here is to find a cheap 2 inch backbox from another car and bolt it on and see how it sounds.  That is proving a bit difficult as it's impossible to find from browsing parts what the diameter of the inlet pipes are.  I know that 240s use a 2 inch system so I might try picking up a used backbox from one and see how that works out. I'm open to suggestions here though.

The other option there is to dismantle the Simon's backbox and change it from a straight-through design to a baffled design by fabricating some parts and rearranging the internals.  That's the cheapest but largest faff option, but it means I get to use the parts I've already paid for and I don't see myself making it much worse!

Universal off-the shelf silencers seem to all be of the straight through type which is not going to help matters at all.

The last issue with the car is the brake lines, which although I made new ones up this time last year from so-called kunifer pipe, they have all rusted to fuck and look terrible. I don't have much faith in the pipes actually lasting much longer. I'm going to redo the whole car in halfords brake line since I've found it seems decent quality.