Tech Tips

Tips to make car modification life easier

by Julian Edgar

Click on pics to view larger images

At a glance...

  • Detonation detection
  • Making an oxy welding bench
  • Sourcing dirt-cheap mufflers, cat converters, intercoolers and airboxes
  • Accurate angle finding
  • Scouring secondhand machinery yards

Here are some ideas that will make your car modification life easier and/or cheaper!

Detonation Detection

In a number of articles over the last decade we’ve covered DIY detonation detectors. In each case, we’ve used a remote-mounted microphone (eg clipped to the engine head), a long shielded cable leading back into the cabin, and then an amplifier and earphones.

Despite its simplicity – you’re just listening directly to the noise transmitted through the engine metalwork – this approach works very well. The ‘tink tink’ of detonation can be clearly heard above other noises and, furthermore, when you get experienced at listening, you can also detect the harsher note an engine gets just prior to audible detonation.

But the more you can focus on hearing the correct sounds, the better the system works. The enemy is louder, normally low frequency, noise coming from the engine, the tyres and so on.

And here’s where a new approach comes in. Noise-cancelling headphones and earphones are now widely available. These use an inbuilt microphone to ‘listen’ to the ambient noise and then cancel this noise by feeding an out-of-phase signal to the ears of the wearer.

The Sony units pictured here can decrease the noise in the 40 – 1500Hz range, reducing it by as much as 14dB at 300Hz. That lets you more clearly hear the noises you’re listening for - the result is a much more effective detonation detection system!

Oxy Welding Bench

When I bought my oxy acetylene welding equipment, I needed a bench on which to work. That bench needed to be fireproof, and most people suggested using special firebricks. But, not having any firebricks and wanting to get started straight away, I used concrete paving stones.

I assembled a working surface by laying these on a wood and steel frame, using multiple timber slats to support the relatively small pavers. I then grabbed a few more pavers to use as props and supports. It was all because I had nothing else to use – but over the years since, it’s proved to work brilliantly!

The paving stones that form the working surface can be moved and gaps opened-up, so allowing an object being welded to project through the surface. This makes jobs like welding end-caps on tubes really easy. The individual pavers are a great size and shape to acts as weights, supports and packing under items being welded. The pavers haven’t cracked, exploded or degraded when subjected to heat. (But some might, so initially experiment with care!)

All in all, the approach has worked extremely well!

Buy Those Cheap Bits!

I’ve said this before but it can stand repeating: right now, on eBay and similar venues, there are great bargains to be had, especially in exhausts, intercoolers and airboxes. Well, bargains if you’re working with engines developing under 200kW, anyway!

What you need to look for are people with large and powerful cars who are upgrading these aforementioned parts. Oftentimes, they then put the standard parts up for sale or auction at tiny prices, happy to get whatever money they can. But these parts are perfect for less powerful cars – plus they have OE factory durability and build quality.

In fact, hanging in my home workshop right now I have a complete five year old Holden V8 exhaust, from the manifolds to the tip. In addition to the pipework, that includes two cat converters, two resonators and a single muffler. Total cost? I think it was $2. The cat converters alone are worth more than that in scrap value!

I’ve also got hanging up (out of the way, so no space is used up) a complete Falcon XR6 Turbo exhaust, and up on a shelf a complete XR6 Turbo intercooler and plumbing, in as-new condition. Again the prices were tiny – well under 1/10th the cost of buying aftermarket parts.

Since in the future I ‘m most likely to modify small engines, I’ve got sitting waiting for my use a good quality, high flowing intercooler, cat converter, resonator and muffler. All for basically nothing.

Now I just need to buy up some good airboxes…

Angle of the Dangle

When you’re constructing something, a bubble level is very useful. And not just when putting up shelves, or levelling a concrete path. A bubble level is also excellent when making sure parts of a fabricated structure are parallel, or ensuring things are square to one another, especially when you can’t fit a conventional square into the structure.

But even better than a level is a clinometer. A clinometer – or angle finder – shows you angles that don’t have to be horizontal or vertical, giving you much greater flexibility in use.

For example, when using a bench-mounted tube bender, you can use a clinometer to ensure that two bends are formed in the one plane (just keep the first bend and the tube former on the same angle), you can ensure that two duplicate structures containing lots of angles are in fact made in the same way, and you can use it like a bubble level – but without having to ‘pack’ items to make them level in the first place!

You can also use a clinometer to measure castor and camber of wheels, seat and windscreen angles – and so on.

The clinometer pictured above is available from good hardware and tool stores, while if you have an I-Phone, you can buy from the I-Tunes store a very cheap application that turns the phone into a digital clinometer.

Secondhand Machinery Yards

If you live in an area that has secondhand machinery yards, it’s well worth taking an occasional walk around them.

Curiously, where I live I can’t find even one decent machinery disposals yard, but in an interstate city - one I know well - there is a bunch! So, whenever I travel to that city, I put aside the time to go out to its industrial areas and have a good dig through the junk.

But why bother? Well, what’s pictured below is a good example.

The best way to make custom turbo exhaust manifolds is to use ‘steam pipe’ parts that are (more correctly) called ‘buttweld fittings’. These, as the name suggests, are designed to be welded together. The buttweld fittings of most interest to manifold constructors are the bends. The bends are designed to cope with very high pressures and are made of very thick, high quality steel.

So? Well, the other day, while scouting out the back of a machinery disposals yard, I came across a whole bag of buttweld 90 degree bends, with an ID of about 25mm and a wall thickness of 3.6mm. A few had some surface rust - something a wire brushing would take off in moments – but other than that, they were in new condition. Rather than ask for a price per bend, I asked how much the lot would cost – and was told $5 a kilogram!

Fifty dollars later the bag of bends was mine – a later count showed no less than 70 bends in the bag… so a cost of 71 cents a bend. Even paying freight home, the bends were still only a little over a dollar each – a pretty good saving when the last turbo manifold I built used nine bends at a total cost of $70!

Now of course you can’t guarantee you’ll walk into a junk yard and walk out with items like those buttweld bends – but it’s very likely that you’ll find something of use to car modification!

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