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The mkiv Supra Owners Club

Technical bods - I need your help for some info for this site


Aerotop Dave

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I'm trying to compile a list of Supra mods for the technical section but I don't have a clue about the stuff. The idea is to list each mod, what it actually is, it's common abbreviations and the pros and cons. So for example, something like this:

 

Name: Race Logic Traction Control

Abbreviations: RLTC

What is it? Programmable (via DAT file) traction control unit, with in-car adjustment via a control box.

Pros: Great in the wet, almost a 'standard' upgrade for the Supra

Cons: Needs professional fitting, DAT file software not the easiest to use.

 

Put in as much or as little as you like, and there's no requirement to be too technical about the whole thing, so if a dump valve makes a nice swooshy noise, mention it! If everyone does one each we should have this done in no time. My only request is that we don't get into any arguments over the exact pros and cons. If the wording is broadly in agreement with most people's perceptions then we'll leave it there.

 

To kick it off I've compiled a list off the top of my brainbox of what we need doing, but if you can think of anymore by all means put them down.

 

Race Logic Traction Control

Fuel cut defender

Hybrids

Induction kit

Dump valve

Turbo timer

Wheel spacers

Basic Performance Upgrade (BPU)

 

Thanks folks :thumbs:

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Name:

Solar Sensor

 

Also known as:

"the round dome thingy on the top of the dashboard"

 

What is it?

It's the round dome on top of the dashboard. It's part of the aircon system and detects strong sunlight coming through the windscreen.

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Name:

Misfire under boost

 

What is it?

You get a misfire under high boost, usually over 1 bar.

 

Caused by:

Running higher than stock boost on stock spark plugs

 

Why?

Spark plugs have different temperature ranges, and 'colder' ones are designed to run in a hotter running engine, if that makes any sense to you. Warmer plugs start to fail under high temperatures, higher boost causes these higher temperatures. As the resistance in the plug increases due to the heat it's exposed to, the spark may not be strong enough to take place. This causes the misfire.

 

How bad is this problem?

It ruins the driving experience, but above that the too-hot plug will degrade at an accelerated rate and may eventually disintegrate. Having chunks of spark plug going through your cylinders and turbo is A Bad Thing.

 

Remedy:

Install a colder grade of plug. Denso IK24's are good if expensive, NGK BKR7E's are cheaper but may not be good enough for serious applications and don't last as long. Denso IK22's are slightly colder than stock if you want a long-lasting easy starting plug for mildly upgraded engines.

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Name:

Fuel cut

 

What is it?

Your car pulls strongly and then loses all power like you've lifted completely off the accelerator. The Malfunction Warning light on the dash (red excalamation mark) lights up for a couple of seconds, and then you get power back.

 

Caused by:

The stock Supra is set up to see 0.8bar of boost. The ECU has a failsafe system in it to prevent runaway boost from damaging the engine. It does this by cutting fuel delivery if it sees over 1 bar of boost for a short period of time. This is the sudden scary loss of power and it's also signified by the malfunction light on the dash.

 

Why?

You have decatted the car, fitted a boost controller that ups the boost beyond 1 bar, or have a problem with the wastegate system. Too much boost develops when giving it large.

 

How bad is this problem?

Short term it's a pain in the backside, but it can also be dangerous if you are caught mid-overtake or booting it round a bend due to the sudden abrupt loss of power. Long term it's accelerating wear on all drivetrain components.

 

Remedy:

Either lower the boost below 1bar mechanically (fix wastegate system, fit restrictor ring, refit cats), or fit a Fuel Cut Defender (FCD). See elsewhere in the FAQ for FCD's.

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Name:

Fuel Cut Defender

 

Also known as:

FCD

Boost cut controller

 

What is it?

It's a bit of electronics that changes the airflow signal to the ECU so that it never sees more than 1 bar of boost. This is to avoid Fuel Cut.

 

Pros:

No more fuel cut when hitting over 1.0bar of boost

 

Cons:

Crap FCD's scale the airflow input so that when the stock sensor hits 1.25bar (it's maximum) the ECU gets a shade under 1.0bar. This also has the effect of scaling the ENTIRE airflow signal so the ECU always receives a lower airflow value than the engine is really getting. Messes up the whole fuelling map towards the lean end of the spectrum and is therefore highly not recommended.

 

Good FCDs merely clamp the signal at a certain voltage, meaning the ECU sees the correct airflow signal until 0.99bar and then that's all they see. Of course, a big drawback now is that if you are running more than 1bar of boost, you need some way of making sure the fuelling is correct, as the ECU will only ever fuel for what it thinks is 0.99bar.

 

Also you now have no overboost protection any more, however a *really* good FCD will clamp the signal and then initiate fuel cut if the FCD unit itself sees an overboost condition (up to the limit of the stock pressure sensor).

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Guest Terry S

Check out the new tech mod:p

 

To be added

12v Mod ( pointless;-) )

Fuel pump upgrade

Adjustable FPR

Alignment specs

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I've got one for the list:-

 

charcoal cannister

 

Here's my crack at a FMIC:

 

Name:

Front Mounted InterCooler

 

Also known as:

FMIC

 

What is it?

A turbocharger works by compressing air and forcing it through the intake into the engine. Because the intake air is under pressure, more air enters the engine which can be mixed with more fuel to produce more power. However, increasing the pressure of a gas also increases its temperature (Boyles law). Also the turbocharger itself gets very hot, and some of this heat is transferred to the intake air as well. This is bad, because hot air is less dense than cooler air, and also hot air can make the fuel/air mixture ignite before it is supposed to in the engine (detonation). The colder the air going in to the engine the better for power and for reliability. This is why cars are more powerful in colder weather.

An intercooler is an air to air heat exchanger. The intake air going into the engine flows through it and is cooled down by air passing over the intercooler like a normal car radiator. The Supra as standard has a fairly small side-mounted intercooler in the right-hand sidepod under the headlight. It's pretty efficient, and fine for stock power levels, but for more power you need something a bit better. A front mounted intercooler is much bigger, and sits in front of the car, in front of the radiator.

 

An alternative is an uprated Side Mounted InterCooler (SMIC).

 

Pros:

Cooler intake charge means less risk of detonation (or more boost for the same risk), more power, looks good, usually comes with hard pipes.

 

Cons:

Blocks airflow to the radiator so more risk of overheating, you really need a bumper with a bigger hole to get the most out of it.

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Additional cons to FMIC:

You need some ducting to get the most out of it, otherwise a large proportion of the incoming air goes around it - path of least resistance. You also have to remove the active spoiler mechanism to fit one.

 

-Ian

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Name:

12v fuel pump mod

 

Also known as:

The fuel pump mod

 

What is it?

The stock fuel system of the Supra has a switched power fuel pump. Anything off-boost and it runs the pump at 9v. Anything on-boost and the ECU switches to running the pump at 12v. This is probably for pump longevity and maybe some NVH reasons. The 12v mod is where you wire the pump to always run at 12v in the belief this will improve your fuelling at high boost high revs.

 

Pros

A warm fuzzy feeling that you've improved your fuelling at high revs high boost for £0

 

Cons

It doesn't affect your fuelling one jot. At best, running the pump at a higher voltage when off boost merely shortens it's life a bit. It could also affect fuelling and drivability off-boost due to overpressurising the fuel system. As the pump switches to 12v as soon as you get on boost, this mod isn't going to change the behaviour of the fuel system when positive boost is occuring in the slightest.

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Name:

Charcoal canister

 

Also known as:

"A black box that makes funny rattley noises, smells of petrol a bit, it's at the back of the engine bay on the right"

 

What is it?

It's part of the emissions system and therefore tedious. It contains charcoal to absorb fuel vapours, and that plus a valve system makes the rattley noise and the petrol smell.

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What is it?

EGR

 

What does it stand for?

Exhaust Gas Recirculation.

 

What does it do?

Popular misconception:

EGR "cleans" the exhaust gas of unburnt hydrocarbons by running it through the engine a second time.

 

What it really does:

EGR manages the tradeoff between two different types of exhaust emissions: HC and NOx (unburnt hyrdocarbons and oxides of nitrogen) by controlling the speed of the combustion process within the cylinder.

 

Most likely modification:

Removal / deactivation.

 

How it works:

A fast burn of the fuel / air mixture inside the combustion chamber will tend to produce NOx emissions. A slower burn will tend to produce unburnt hydrocarbons. In order to control NOx, we need to have a way to artificially slow down the combustion process, which would normally proceed at its own rate according to the conditions inside the conbustion chamber.

 

Exhaust gas, although it can contain a degree of unburnt fuel, is essentially inert. Trying to re-brun the exhaust gas from an engine with correct fuelling is akin to trying to re-light a burnt-out fire.

 

The burn time of the combustion process is linked, amongst other things, to the physical distance between the fuel molecules. It takes time for the flame front to progress across the cylinder (assuming a single, controlled source of ignition) for information, the rate of combustion is measured in Mass Fraction Burn time (the time taken for a certain percantage of the mass of fuel and air to be consumed).

 

By inserting molecules of an inert gas in between the combustable fuel / air mixture, the progression of the flame front can be artifically slowed down and the MFB time increased. This significantly reduces the level of NOx emissions.

 

Pros:

Lower NOx emissions levels.

 

Cons:

The EGR system generally feeds a small proportion of the exhaust gas into the intake charge via a long tube and a valve. During the passage, the gas hopefully loses a degree of heat. However some heat will be retained, which is undesirable. Many tuners advocate removal of the entire EGR system because of the supposed intake charge temperature increases, and the charge dilution effects. However, EGR generally only operates in the low speed / low load area of the map (where emissions tests are performed) and so should not be a concern for WOT performance.

 

The entire system consists of a valve and some metal tubing, which weighs approximately 1kg.

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What is it?

Crankshaft pulley damper

 

Also known as:

Torsional vibration damper (TVD).

Crankshaft damper.

Crank pulley.

 

What does it do?

Harmonically cancels out undesirable vibrations in the cranktrain.

 

Most likely modification:

Replacement with non-damping "lightweight" version.

 

How it works:

The crankshaft in an internal combustion engine does not rotate at a constant velocity. If it did we would not need a large flywheel to store up rotational inertia and smooth out the rotation. The crank is accelerated by (in the case of the 2JZ) one power stroke every 120 crank degrees. The effort that this stroke produces varies as the crank angle changes. Simulataneously, the other cylinders will be drawing in a fresh intake charge, compressing it, or expelling spent exhaust gases - i.e. resisting the power stroke. Therefore, the crank is "nudged" around in a series of close, but individual, impulses of energy.

 

Any mechanical system will have a natural, or resonant, frequency. A systems' resonant frequency is that at which it will vibrate in free air on its own if given a single impulse of energy. For a practical example, twang a ruler over the edge of a desk. The vibration that it vibrates at is its resonant frequency. You can see how this varies as the mechanical system changes by shortening the overhanging length of the ruler - the frequency goes up the shorter the ruler gets.

 

Another effect of the natural frequency is that if, instead of a single impulse, you can input a series of impulses which are timed at the same frequency as the natural frequency then the vibrations will very quickly raise to the point where they are out of all proportion to the input. However, the moment that the frequency of the input impulses moves away from the natural frequency the vibrations quickly come back under control. This effect is called resonance and is most usually encountered when you have an out of balance wheel. The wheel has a natural frequency by virtue of its out of balance. The input impulse is the speed of the wheel. At a certain narrow range of road speeds, you will find that you can feel a vibration through the steering wheel. This is the speed at which the wheel goes into resonance.

 

So how does all this relate to the crank pulley?

 

We have already mentioned that the cranktrain is being driven by a series of energy pulses. The cranktrain, like any other system, has a natural frequency. The input frequency can be approximated to the engine speed, at certain engine speeds the cranktrain will tend to go into resonance and vibrate out of control. These vibrations can have effects ranging from discomfort, noise, poor misfire diagnosis and other ECU sensor problems, to the physical failure of the crankshaft.

 

Cranktrain vibration comes in more than one flavour. First of all consider the crankshaft as a watch spring, oscillating back and forth (but generally turning in one direction). This is torsional vibration. Secondly, consider the crank as the ruler from earlier on. Except this time instead of a single desk edge as a support we have a series of supports in the form of the main crank bearings. Also, instead of a single energy input we have all four strokes of the four stroke cycle all acting at different places along the crank in different degrees at different times. These forces can cause the crank to bend along its length. This makes for a very complex system (both in torsion and bending) but it will still exhibit resonances in both.

 

However, resonance can work for us, and this finally brings us to the purpose of the crank damper.

 

The torsional vibration damper (TVD) consists of a mass of a known intertia which is attached to the crankshaft via a piece of rubber of a known stiffness. The mass can spring torsionally around the crank centreline. The inertia of the mass and the stiffness of the rubber are precisely tuned so as to go into resonance in an equal and opposite manner to that of the cranktrain. Therefore they cancel each other out.

 

A bending damper has a mass which is added to the end of the crankshaft via another piece of rubber. This type of damper nods up and down and cancels out bending vibrations along the crankshaft.

 

These masses, for convenience, are usually added to the front crank pulley.

 

Pros:

The most common reason to remove the damper is to reduce weight to lighten the car, or to reduce inertia to make the engine rev more freely (inertia by definition resists changes in rotational speed). However to do this you have to sacrifice the damping actions of the stock pulley. You cannot retain the same damping effects and reduce the mass at the same time. This is akin to having your wheels balanced using stick on balance masses, and then binning them and replacing them with lighter masses. The wheel will obviously go out of balance again. Likewise if you remove the damping pulley, the crankshaft will go into resonance.

 

Cons:

As mentioned above it can be as little as noise and vibration or as severe as total crankshaft failure through fatigue. Fatigue is the failure of a part through repeated application of loads which are far smaller than those which would cause failure in a single application. These are most severe when the loads are reversing or alternating (like bending a paperclip back and forth). This sits nicely with the kind of vibration seen in undamped cranktrain systems.

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Originally posted by Ian C

Name:

12v fuel pump mod

 

Cons

It doesn't affect your fuelling one jot. At best, running the pump at a higher voltage when off boost merely shortens it's life a bit. It could also affect fuelling and drivability off-boost due to overpressurising the fuel system. As the pump switches to 12v as soon as you get on boost, this mod isn't going to change the behaviour of the fuel system when positive boost is occuring in the slightest.

 

LOL, Ian clearly recomends this modification :D

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Originally posted by carl0s

carbon canister:

 

would that be this then?

http://www.css-networks.com/carbon.jpg

 

I was about to post to ask what it was - sounded like something arc'ing before (engine off).

That's it. Of course you wouldn't have posted cause you'd have used the search and found my post about it - wouldn't you! :stickpoke
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