**This is a replay from the old podcast series lost to the internet**

Original upload date: 26/11/2020

I’ve been able to live under a rock and avoid the hype around the Nissan 400Z release which was difficult being a made 240Z owner and fan.

In this episode I emerge from under that rock and review the hype for myself raising the question, is if difficult for a manufacturer to design something unique while following the legacy of a classic?

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**This is a replay from the old podcast series lost to the internet**

Original upload date: 27/10/2020

There are three types of valve-train used in petrol engines and all three are still produced new. This a guide we're going to discuss OHV vs SOHC vs DOHC, the good the bad and the ugly of each.

I've been lucky enough to own and fiddle with variants of all three. Bear in mind this is a generally overview and there will always be examples that push the limits or are highly efficient.

Watch the latest Built On Purpose YouTube video HERE

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**This is a replay from the old podcast series lost to the internet**

Original upload date: 13/10/2020

Cast and forged pistons are made from the same materials. Both types of pistons have the same density. So what makes forged pistons stronger than cast?

Watch the latest YouTube video HERE

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YT: ⁠Built On Purpose⁠

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**This is a replay

Original upload date: 6/10/2020

Now, match porting manifolds. This is the process of modifying ports to align smoothly at the gasket, removing obstructions to the air flow pattern.

Why do this? Well let’s jump into some background info on fluid dynamics. Air is essentially a compressible liquid and conforms to hydraulics.

Whenever a fluid particle changes direction it loses energy. You might read about achieving laminar (or smooth) flow, a characteristic when certain velocities for a given situation are achieved that all the fluid particles move parallel with good efficiency, this is ideal for pipe flow but will never truly occur in an engine intake or exhaust.

Laminar flow requires continuous velocity and this state is not achieved. The flows are stop started by the natural operation of the valves.

For some applications there is benefit in having an uniform obstruction. Whaaat I hear you ask? Well, particularly in carburettor applications, the waves created from the valve operation can cause a phenomenon called reversion.

Carbs rely in vacuum to draw fuel into the air mixture and reversion can sometimes knock fuel particles out of the air stream and push them out the end

Watch the latest YouTube video HERE

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YT: ⁠Built On Purpose⁠

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**This is a replay from the old podcast series lost to the internet**

Original upload

What is dynamic compression ratio? It is not commonly known. Most are familiar with static compression ratio used to describe a characteristic of engine. But what is the difference of dynamic compression ratio vs static?

Static compression ratio uses the volume associated with a full sweep of the piston from bottom dead centre through to top dead centre. Dynamic compression ratio is governed by the stroke derived from when the intake valve closes which is normally after bottom dead centre.

Longer duration cams cause the intake valve to close later reducing the dynamic stroke and as such the dynamic compression ratio.

Link to spreadsheet: https://kyushaspeed.com.au/shop/dynamic-compression-ratio-calculator/

Link to blog: https://kyushaspeed.com.au/what-is-dynamic-compression-ratio/

Please leave a rating or review if this was useful and check out the rest of the podcast.

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YT: ⁠Built On Purpose⁠

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**This is a replay from the old podcast series lost to the internet**

Original upload date: 22/09/2020

The detonation or knock threshold may not be properly understood by some. In this episode I break down what is detonation, knock, pinging threshold and how auto ignition contributes.

Knock, pinging, detonation is the name given to the phenomena when one or more auto ignition flame front, separate to the spark plug triggered flame front, collide generating high localised pressure spikes in the combustion chamber. The spike in pressure can be strong enough to physically damage metals and alloys.

Please leave a rating or review if this was useful and check out the rest of the podcast.

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YT: ⁠Built On Purpose⁠

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**This is a replay from the old podcast series lost to the internet**

Original upload date: 21/07/2020

So what is the difference between coil over plug and distributor?  Simplistically the difference is the number of ignition coils.

A distributor-based ignition has one coil for the whole engine using mechanical means to distribute the spark.  This type of ignition does not require any electrical control and is reliable. However as RPM climbs the time between events shortens to the point which insufficient time exists for the coil to prepare the high voltage spark and ultimately spark strength suffers.

For coil over plug (coil on plug) which has more coils meaning less duty per coil.  Spark strength is normally consistent across all engine speeds.  Coil on plug requires an ECU to control the individual coils as well as a crank trigger and cam reference.  If you are converting an ordinary distributor ignition to coil on plug, fitting these items may add additional cost opposed to fitting a CDI unit to your distributor system.

Please leave a rating or review if this was useful and check out the rest of the podcast. 

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**This is a replay from the old podcast series lost to the internet**

Original upload date: 14/07/2020

What is spark plug gap? It is the measurement between the ground electrode and the centre electrode that the ignition spark arcs between. You can have the most advanced ignition system around but if you do not have the gap between electrodes correct your ignition system will not function correctly.

The gap between electrodes determines quality of the spark and the reliability of firing. The gases between the electrodes form a resistance and this promotes a minimum threshold voltage to arc across. However too small of a gap and the voltage requires is less. Too large of a gap and the voltage required may exceed your ignition system.

In summary a small gap promotes reliability of spark but at the expense of spark voltage and heat. Large gaps promote hotter and fatter sparks but may mis under load.

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**This is a replay from the old podcast series lost to the internet**

Original upload date: 07/07/2020

How CDI systems work is thanks to capacitors. Capacitors are a form of batteries that can physically store energy.  This is useful to ignition systems as the energy can be discharged instantaneously unlike traditional ignition coils which require time to generate and collapse a magnetic field to generate the high voltage needed for an ignition spark.

The short stronger spark produced by CDI systems greatly benefits the upper rpm range. This is not very good for low load and rpm conditions which require longer spark durations to complete combustion. Most manufacturers use multiple sparks over a short period of crankshaft rotate to combat this.

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**This is a replay from the old podcast series lost to the internet**

Original upload date: 29/06/2020

What is ignition coil dwell time? It is an important parameter which is governed by how an ignition coil works which was covered in the previous episode.

Using an incorrect dwell time for your ignition coil could result in misfires from weak spark or damages coils from heat.  How long does dwell timing need to be?  That depends on the coil.  Each coil is different from a couple of factors such as primary winding wire diameter, voltage and current available and winding ratio.

DTEC article on ignition: http://dtec.net.au/Ignition%20Coil%20Dwell%20Calibration.htm

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