Author Topic: Fools Guide To Basic Tuning  (Read 9906 times)

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Offline Crab Doctor

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Fools Guide To Basic Tuning
« on: April 15, 2016, 02:18:52 PM »

***** = Very difficult, professional only.
****   = Difficult, experienced or professional help required.
***     = Fairly easy to someone with some experience.
**       = Easy, can be done by someone with relatively little experience.
*         = Very easy, can be done by anyone.

Air System


Price: Roughly 300 for a kit from Airtec.

Difficulty: ****

Function: To understand the Intercooler more, it is best to first understand how a turbo works. The turbo is bolted to the exhaust manifold and is 'powered' by the exhaust gasses as they exit the cylinder head. This spins the fans which actively compresses the fuel/air mixture up to 50% before it enters the cylinder, typically resulting in up to 50% more power or 'boost' (In theory).

The typical PSI (Pounds per Square Inch) that a turbo produces is 6-8psi. The atmospheric pressure at sea level is 14.7psi. This means that the turbo increases pressure by up to 50%. However the turbo fans are spun by the exhaust gasses exiting the cylinder which inevitably increases the pressure slightly for the engine to push the gasses out. This means that the turbo'boost' is in reality closer to 30% - 40%.

The air mixture exiting the turbo is hot which takes up more space than cool air. This is where the Intercooler comes into play. The Intercooler sits between the turbo and the fuel injectors. It is effectively a small radiator and its job is to cool the air before it enters the system, resulting in more fuel air mixture and a bigger bang in the cylinder head. Remember, more bang is a good thing! A very good thing!

A good Intercooler will have less pipework and slightly higher diameter pipes resulting is better flow and more efficient cooling resulting in more fuel/air mixture and a bigger bang.

Induction kit;

Price: Between 200 to 300

Difficulty: **

Function: The Induction Kit is basically a filter. Standard factory fitted filters are a compromise between efficient filtering and noise reduction. An Induction Kit is a loose filter that allows more air to flow into the engine. Whilst they do still efficiently filter out particles from the air before they can enter the engine and cause damage, they are a bit louder.

However the Induction kit does sit in a hot engine bay and will effectively be sucking in heated air which reduces your bang. You can get around this by fitting a cold air feed pipe to introduce air from outside he engine bay. Consideration is needed when deciding where to put this pipe feed though.

Care should also be taken in which kit to choose as they vary hugely. It is best to choose a kit with a cotton gauze filtration medium although it is always best to get a kit that is designed specifically for your model of car.

Turbo System

Recirculation Blow Off Valve (BOV)/Atmospheric Blow Off Valve (BOV);

Price: 75 to 100

Difficulty: **

Function: The Blow Off Valve or 'BOV' is attached to the intake tract on the turbo itself. Its job is to protect against 'compressor surge' which is what happens when you suddenly lift off of the throttle and the throttle plate closes. A rush of boost heads to the engine but is stopped by the closed throttle plate and has nowhere to go. It then returns to the turbo and really starts to mess things up. It slows the turbine and can damage it but will also create lag and affect throttle response which can be undriveable. This is where the BOV comes into play. The valve vents the excess pressure into the atmosphere (Atmospheric Blow Off Valve) and creates the 'PSSHHhhh' noise that turbo heads crave so much. However the type of BOV you require really depends on your engine and its management system. For example the MultiAir engine is a MAF (Mass Air Flow) type system where there is a sensor that detects the airflow entering the engine. If this air is then released by the (Atmospheric) BOV the ECU will not be able to fuel the system properly resulting in stalling, poor throttle response, inability to idle etc etc. This is where you will need a Recirculating BOV. This recirculates the excess gasses back into the turbo system before the compressor inlet which gets around the Mass Air Flow sensor issue.
The idea of fitting a custom BOV is to will allow the valve to release the pressure at the PSI of your choosing. This can affect turbo lag, throttle response etc. and improve the efficiency of the turbo, particularly in relation to the rest of the modifications you have made.



Difficulty: **

Function: The Actuator is a valve attached to the turbo and controls the maximum boost or PSI from the turbo. As the exhaust gasses build up and spin the turbine, the valve opens at the required PSI and vents the gasses away from the turbine. The purpose of this is to prevent the turbine over-spinning and reducing wear and tear or even causing potentially catastrophic damage to the turbo and engine. The problem with factory fitted actuators is that as you start adding components to increase power or in particular boost (from plug and play tuning boxes or remapping etc.) the actuator will open earlier that you'll want as the pressure builds to the level that the device is set to. It is advisable then to fit a custom Actuator to allow for the increased demand for boost. This will allow the turbine to spin higher creating more pressure.

Exhaust System

The exhaust system on the whole if fairly simple in theory. The basic principle is that the system itself goes some way to slow the engine down as the gasses offer resistance as they are forced through all the pipes and boxes etc. Imagine it like you are trying to blow through a small straw from a child's juice carton. Then compare that to a McDonalds straw which is far bigger. The bigger straw is easier to blow through, right? Well it's with that the same principle that more power is gained through the exhaust system. This is explained in greater detail below by APC member William Webb:

To elaborate on the above, your exhaust is made from three separate sections.

Downpipe: The part that bolts onto the turbo and comes down and under the front of the engine. This section usually contains the Catalytic Converter (CAT) and the Lambda Sensor.

The CAT consists of a fine honeycomb mesh which is coated in precious metals which chemically reacts with the gasses and renders the harmful particles inert. The process of the harmful gasses passing through the mesh slows them down and creates a 'bottleneck' which will in turn slow the engine resulting in slightly reduced power.
You'll hear people talking about a 'Sports CAT'. These are usually 150 to 250 cell. This describes how many honeycombs are in each square inch. In comparison, standard Abarth CATs are 400 cell. So you can see, the fewer cells, the more airflow through the system resulting in slightly increased power from the engine.

Fitting a 'DeCat' replaces the CAT with a downpipe. This requires that you fit an Emulator to fool the system into thinking that the gasses are cleaner than they are. Note that fitting a DeCat would make the car fail to pass an MOT and make the car illegal to drive on the road so this should only be done to a track car.

Mid-section: On the Punto Evo this is a straight pipe with a 'mandrel bend' (explained below). On the original Grande Punto this section had a silencer in it.

'Mandrel bends' retain their diameter throughout the bend so you don't affect the flow too much. This gives better performance as it allows the gasses to escape the exhaust much easier. Cheap exhaust systems have crushed pipes that deform the inner and outer edges, reducing the diameter.

Silencers are basically a box with a perforated pipe running through the middle. The perforations allow some of the gassed to pass through and into a material, usually a fibreglass matting or similar. This reduces the sound that the exhaust emits. The negative to this is reduced flow and performance.

Rear Box or 'Back Box': This is basically another silencer as described above except it has two unconnected pipes, one of which comes the back end of the mid section and lets the gasses enter the box itself. The box is filled with a baffling material, again usually fibre glass. The gasses then enter the second pipe and vent into the atmosphere.
As you can imagine, this is a restrictive path and significantly affects performance. Fitting a straight pipe Back Box improves flow but drastically increases noise.

William Webb

Engine Management System

There are several ways that the engine management system can be tweaked or even re-programmed. The easiest is the 'Plug and Play' boxes that are more or less easy to install. However these are pre programmed and do not take the changes you may have made to the car or your personal preferences into account. The alternative but more expensive method is 'remapping'. This involves reprogramming the management system itself which is far more bespoke to you and your car's needs.

This is explained in further detail below by APC member Thomas Robert-Eagles:

'Effectively, plug and play boxes such as the TMS unit for example changes the value in situ. So the value of 0.5 might be 0.4 after passing through the TMC box. This would trick the engine into injecting more fuel or increasing boost pressure.

A remap comes in two different 'flavours'. A generic remap which is a reflash (re-write) of the ECU instructions that govern the engine.

The second is a live remap where the car is placed on rollers and mapped according to the engine and its response to changes. This allows tweaking to the customers preferences, engine limitations or hardware limitations. for example you can live map to artificially lower torque to protect the gearbox.'

Thomas Robert-Eagles

APC member Tim Clarke adds:

'Remapping is the process that a tuner uses to make changes to the values which determine ignition timing, fuel injection, boost limit, RPM limit to provide amongst other things smoother idle, better pick up, higher boost and/or torque. However you should fit all other mods on your wish list before you attempt a remapping of the ECU as this will achieve better results.

Chipping is basically a potted version of this with generic improvements to the values which are not matched specifically to your car or your engine.'

Tim Clarke

Right that's about all you can really do with these cars. Any questions then don't ask me, I'm a complete noob so your guess is as good as mine!
« Last Edit: April 15, 2016, 08:28:48 PM by Bertie »

Offline Motion Lotion

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Re: Fools Guide To Basic Tuning
« Reply #1 on: May 03, 2016, 07:44:25 PM »
As a novice I am enlightened and appreciate the straight forward talking as I am about performance more than the noise etc.

Quick question, some say the BOV is just a gimmick and its not really worth having one; however from a technical perspective, should the right BOV work to reduce turbo lag and give you faster turbo spin and higher pressure? Bigger bang?

Just don't want to be spending hard earned dosh on the wrong things!

Motion Lotion
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Offline Crab Doctor

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Re: Fools Guide To Basic Tuning
« Reply #2 on: May 03, 2016, 07:57:50 PM »
I'm also a novice at this and as such I am not aware of any performance enhancing BOV for the Tjet engine (500 range and Punto Grande). The forge BOV for example, which I believe is an atmospheric BOV is just a noise maker and will not improve performance (from what I'm told).

However I do know that the unit I based this on, the GFB (Go Faster Bits) BOV is only available for the MultiAir engine (Punto Evo) and it does reduce turbo lag and increases boost etc etc. I drive a Punto Evo essesse and the difference it made was astonishing. I don't think it increases BHP but it does pull harder and the lag between gear changes is gone.

Great little mod  8)

Offline buckwits

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Re: Fools Guide To Basic Tuning
« Reply #3 on: May 30, 2016, 08:55:32 AM »
If I could add my 2 pence worth, lowering is a cheap and easy mod. I did mine myself in a few hours for less than 100. Makes a world of difference to both the look and handling of the car.

Offline Crab Doctor

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Re: Fools Guide To Basic Tuning
« Reply #4 on: May 30, 2016, 09:50:28 AM »
Agreed, I drive an Abarth Punto Evo Essesse and as such it's factory lowered. I took it to Brands Hatch last Tuesday and cornering speed on standard road tyres surprised a few people including me! However this thread is about tuning specifically, not modding.