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Tuning the Nissan 200sx SR20DET engine

Content: Tombs / Papa Lazarou / Jezz_s13 / Green Meany

Editing & layout: Tombs

Copyright ©2003 the contributors and www.sxoc.com

Corrections: Creasey / Dave_S / SteveCarter200

Pictures: Papa_Lazarou / A’PEXi


IntroductionThe 2-litre SR20DET engine found in the UK-spec 200sx (s14 & s14a) provides 197 bhp and 195 ft/lbs as standard. These figures can easily be increased, through a series of modifications, initiallysimple, and later more complicated. Reaching 280-300 bhp is relatively straight-forward; with moreapplication and expense, figures of around 500 bhp and above can be achieved.

This document explains the engine various modifications, with a common path through them.However, these various modifications can be done in many different orders, and this is merely aguide.

200 bhp 300 bhp 400 bhp

Tuning Map (with power gains)approximate

Better enginebreathing

Bigger turbo

Moreboost

Increasethe boost

FMIC Cams

Uprated fuel pumpColder plugs

Engine internals?

Larger injectorsUprated ECU

Tubularmanifold


Engine breathingThe s14 200sx seems to have been designed and marketed not as an out-and-out sports car, but asa sporty car with suitability for the company-car market. With this in mind, the air intake and theexhaust are quite restrictive, making the car more refined. Removing these restrictions will unleasha good few horsepower just by allowing the engine to do its job unfettered, and as such, may evenincrease the fuel efficiency!

Air-box panel filterThe filter element from the standard air-box can be replaced with a less restrictive version, makingit easier for the engine to suck through a bit more air. The power increase will be relatively smallwith this modification, as a large part of the restriction in the air intake comes not from the filter,but from the design of the air-box itself. One test of various filters (albeit not on a 200sx) found noperformance gain whatsoever from a panel filter. This modification is useful as it isn’t obvious, andsome people won’t worry about declaring its presence to their insurance company.

The airbox can also be customised in several ways, to facilitate greater flow. The elbow betweenthe airbox and its air-feed from the front of the car can be removed, holes can be drilled in theairbox (obviously in the pre-filter side!), and ducting can be directed to the airbox from a cold airfeed.

Induction kitComplete removal of the air-box and replacement with an induction kit will allow even betterbreathing, as it eliminates both the restrictive filter and its air-box. There are various types ofinduction kit available, all with different types of filter & different filtration abilities. The idealwould be a kit with good filtration properties (which prevents dust particles from reaching yourturbo blades) but that is not too restrictive.

One possible drawback of induction kits is that they are more prone to sucking in hot air from theengine bay than the standard air-box, slightly decreasing the amount of oxygen actually taken in(as the air is less dense). It has been debated how much of an effect this might have. This problemcan be lessened by either ducting cold air to the intake, forming a barrier between the engine andthe intake, or moving the intake further from the engine, to an area of direct cold air feed.

Big-bore (cat-back) exhaustFor the sake of quietness, the standard exhaust is quite narrow, which unfortunately also restrictsthe flow of exhaust gases. This can be improved with a larger bore exhaust, letting the gasses flowfreely, making the engine more responsive. Also, ‘sports’ back-boxes are designed to be less restric-tive. Fitting a sports exhaust will alter the exhaust sound and longevity. Stainless steel exhaustshave a harsher boomier note, and will last for many years. Mild steel exhausts have a throatiersubtler sound, but will last for a shorter time.

Front-pipeIf you’re going to de-restrict the exhaust from the catalytic converter(s) backwards, it also makessense to enlarge the bore of the front pipe. This will not only improve the power, but also the‘driveability’ of the car, giving it better low-rev responsiveness.

Due to the different designs of the s14 and s14a, the front pipes are not compatible.


De-cat pipeThe catalytic converters (one on the s14, two on the s14a) also significantly restrict the flow ofexhaust fumes. Replacing them with a simple de-cat pipe results in a significant increase in powerand torque, but has moral and environmental consequences. It will also make the exhaust a lotlouder, too! The cat(s) would need to be replaced prior to an MOT test. Another problem is thegrowing number of Police road-side car checks in the UK; removal of the cats would lead to failingthese tests.

Turbo elbowThe standard turbo exhaust elbow is fairly poorly designed, being too narrow for efficiency, andcreating too much turbulence. Replacing it with an aftermarket model will increase the powerfrom the turbo (especially at higher revs) and make the engine quicker to rev too. Due to theposition of the turbo, this is a time consuming modification to fit.

Turbo elbows are interchangeable between the s14 and s14a, and will therefore allow you to makean s14a take the front-pipe & de-cat meant for an s14.

Inlet/exhaust manifolds

Increasing the boostThis is a simple idea – increasing the level of boost will increase the amount of air the engine re-ceives; the Engine Control Unit (ECU) will monitor this air-flow, and add more fuel to maintain themixture, resulting in more power. After a point (around 300-350 bhp), all increases in power willcome via more boost through a bigger turbo; other modifications after this point are merely toallow the engine to cope with the high boost levels.

The standard UK-spec 200sx SR20DET runs at about 10psi. The standard ECU can only cope with acertain level of increased boost (and correspondingly, air-flow), before it finds itself unable toprovide enough fuel to maintain the combustion mixture. If the level of boost is too high, the riskis that the combustion mixture could become too ‘lean’ – this would make the combustion hotterthan normal, which could damage the engine.

To guard against this, the ECU monitors the amount of air entering with the Air-Flow Meter (AFM),which feeds the ECU a voltage (up to 5 volts) which is proportional to the air-flow. The ECU usesthis information, together with the ‘load’ on the engine, to trigger the ‘fuel-cut’, thereby protect-ing the engine. This prevents combustion, presenting potentially dangerous combustion cycles, butit also cuts the power produced by the engine dramatically, making the car jerk violently.

There are ways of overcoming this ‘fuel-cut’, notably the HKS Fuel–Cut Defencer (FCD). This worksby ‘capping’ the voltage the ECU receives from the AFM, so that the ECU is tricked into thinking theair flow is lower than it really is. However, if you prevent the fuel cut from operating on an enginewith a standard ECU, you obviously run the risk of the engine ‘running lean’, as the ECU will onlyprovide fuel to match the air flow it knows about, when in reality, the air-flow could be muchhigher. If you have an engine with an uprated management system, removing the fuel-cut wouldbe safe, assuming you are certain the fuelling is set up well for all possible boost values, and will notrun lean. An alternative approach is to swap the 200sx AFM for the larger model from the 300zx,which can cope with a greater air-flow; various engine management systems have a setting to allowthis change. Some engine management systems will remove the fuel-cut altogether.

Another factor to consider is the ambient air temperature – colder air is more dense, so will providea greater amount of oxygen at a given boost level. You might find that a car well set up for thesummer will trigger the fuel cut in the winter.


Some methods of increasing the boost can be susceptible to ‘boost spikes’ – short-term increases inboost above the expected level. Brief spikes rarely cause problems with ‘running lean’, but can leadto uneven power delivery and hitting the fuel cut. These spikes are unpredictable, and thus it issensible to always install a boost gauge to monitor the boost pressure, before you embark on anyof these modifications.

Boost gaugeA variety of these are available. At their simplest, they are just a mechanical pressure gauge that isplumbed into the boost circuit via a long pipe. More complicated versions may run electronically, orhave features such as ‘peak boost hold’, which lets you know the highest level of boost achievedwithout staring constantly at the gauge whilst driving.

They are usually mounted either in the driver’s eye-line (such as on the A-pillar) or on the centralconsole, near the stereo. They display the current boost pressure (either in bar or psi).

Free Boost Upgrade (FBU)This is the simplest and cheapest method of raising the boost. It involves removing a restriction inthe pipe that controls the turbo’s actuator. This is achieved either by working a brass restrictor outof the original pipe, or replacing the whole pipe with a section of identically-sized vacuum tubing.This has the effect of raising the maximum level of boost by about 3-4 psi. See appendix 1 for adiagram of which pipe to alter.

One problem is that the FBU has been noted by some owners to cause ‘boost spiking’. If this turnsout to be a problem, the original pipe or restrictor can be replaced.

Gated boost valveThis modification involves inserting a valve into the pipe controlling the turbo’s actuator. The valveincorportes an adjustably-spring-loaded ball-bearing in a tube; when the level of boost pressurereaches the level set by the spring pressure, the ball-bearing moves, allowing excess pressure to leakout, maintaining a steady boost pressure. This allows the boost pressure to run higher than thatset by the actuator.

This is a development of a similar valve, called the Bleed Valve, which was renowned for boostspikes.

Uprated/adjustable actuatorThis replaces the standard turbo actuator, and allows a different peak boost pressure to be set.These can apparantly be more difficult to integrate with an electronic boost controller, should youlater wish to fit one.

Electronic boost controllerAn in-car module, combined with a replacement boost solenoid under the bonnet, allows differentboost levels to be set, and also changed from the cockpit whilst driving. Can also feature extrafunctions, such as an incorporated boost gauge, and look good too! Some electronic boost control-lers, such as the A’PEXi AVC-R, can learn the car’s characteristics (using fuzzy logic) resulting in afaster more responsive control of the turbo.


Spark plugsAs the power produced by the engine increases, you’ll need to exchange the spark plugs for‘colder’ rated equivalents. This is because a more powerful engine will run hotter, and this cancause the tips of the standard plugs to become hot enough to ignite premature detonation of thefuel, before they actually provide a spark. Colder plugs are formulated to resist this. The ‘coldness’of the plug needs to be suitable for your level of power; if you choose a plug that’s too cold foryour engine, it won’t reach its optimum operating temperature, and will become ‘coked up’.

Fuelling modificationsFuel PumpAs the engine becomes more powerful, it will require more and more fuel, and at higher pressures,especially at times of peak power output. The standard fuel pump can only safely provide fuel toaround 250-270 bhp, at which time it is prudent to replace it with an uprated model, to guardagainst underfuelling and running a lean mixture.

Fuel Pressure RegulatorThe fuel pressure regulator (FPR) regulates the pressure in the fuel rail. Typically a fuel pump willpump much more fuel than is actually used by the injectors. The excess is returned to the fuel tank.The regulator maintains a constant fuel pressure by controlling how much is returned to the tank(it operated by a simple diaphragm and spring). At atmospheric pressure (i.e. vacuum hosedisconnected) standard fuel pressure is 43 psi. An adjustable FPR will allow a degree of controlover the eventual fuel pressure, which can help wring a greater flow out of hard-pushed injectors.This can be slightly risky long-term, however, and larger injectors should be considered.

Another factor operating on the FPR is intake manifold pressure: fuel pressure is then variedaccording to manifold pressure in a 1:1 additive ratio. So if running 15 psi of boost, the regulatorsupplies fuel to the injectors at a pressure of 58 psi (that is 43 psi + 15 psi)

Intercooler modificationsWhen the charge air is compressed by the turbo, it heats up. The intercooler comes after theturbo, before the engine. It cools the hot air from the turbo prior to it reaching the engine, mak-ing it denser, allowing a greater amount of oxygen to reach the combustion chamber for a givenvolume or air. This increases the power and efficiency of the turbo system, compared to non-intercooled turbocharged engines. Cooling the charge air also lessens the liklihood of detonation.

The standard 200sx intercooler is mounted in the left front wing, and is just about reasonable foreveryday driving in a near-standard car. However, it is insufficient for more powerful engines:running higher levels of boost, or running the turbo near its efficiency limit, will lead to the aircharge temperature increasing beyond the capacity the of the standard intercooler. It can alsosuffer from ‘heat-soak’ upon hard driving with near-standard engines – it becomes too hot tofunction usefully as a heat exchanger, and power is lost as a result. Subsequently, a larger moreefficient cooler is soon necessary.

Another problem is that the standard intercooler was designed to cope with 10 psi of boost pres-sure. As the boost is increased above this level, the intercooler is unable to allow efficient flow ofthis greater volume of air, leading to a pressure drop. Consequently, the turbo has to work harderto provide the correct post-IC boost pressure.


Uprated wing-mounted ICThis is suitable if your tuning intentions are only up to about 300bhp. It’s a straight replacementfor the small standard IC, but provides better cooling and flowing abilities. As it’s well-hidden andfairly similar to the original item, some people would not feel it necessary to declare it to theirinsurance company…

Front-mounted ICThese intercoolers are improved by virtue of providing a much larger surface area for cooling, andby being better positioned for access to cool air, in the middle of the front spoiler, below thebumper. They can require cutting of the front bumper to be fitted, and some will require theinstallation of a smaller battery, or relocation of the battery to the boot. FMICs also look mean.

Turbo modificationsThe standard turbo on the SR20DET is a Garrett T28. This can be exchanged for a large range ofturbos, each of which will alter the engine’s characteristics in various ways.

� Larger turbos can provide a greater volume of air for a given boost pressure, meaning thatlower boost levels are required for the same level of performance.

� Larger turbos are less restrictive to the engine at the exhaust manifold, so provide greaterperformance for a given pressure.

� Larger turbos heat the air less for a given pressure, resulting in cooler and denser charge air.

� Larger turbos can provide more boost in the higher reaches of the rev range, where smallerturbos start to run out of puff and drop the boost they produce.

� Larger turbos generally require a longer time to ‘spin up’ and start making boost – they have agreater ‘lag’. This can make them less convenient for every-day driving, but is less of a problemfor power/speed applications. This can be minimised by specifying a ball-bearing turbo.

� Larger turbos need a greater amount of exhaust gas to spin them up, which results in themonly providing their boost from a point higher in the rev range.

� ‘Ball-bearing turbos’ suffer from less friction, so spin up faster (and therefore have less lag) thantheir non-ball-bearing equivalents. Thus you could have a significantly larger turbo than stand-ard, without sacrificing driveability. Also, ball-bearing turbos such as the Garrett GT series arestronger and not prone to fail at high boost like conventional 270 degree bearing turbos.Unfortunately, they are also much more expensive.

� Conventional turbos have 270 degree thrust bearings – the bearings go three quarters of theway around the shaft. This is fine until you start running much higher boost than standard,which puts much higher thrust loading on the bearing, causing the turbo bearing to wearrapidly and eventually fail. Turbos with 360 degree thrust bearings are designed to be muchstronger, and are necessary if you want to run above (approximately) 17 psi.

� Some turbos will be direct ‘bolt-on’ replacements for the standard T28; other turbos will requiremodifications to be made to the turbo manifold or the oil/water feed pipes. Some will requirean external wastegate.


Fuel injector modificationsPut simply, larger injectors can provide more fuel per single injection, so can maintain the correctair:fuel mixture at a higher boost level, in a more powerful engine. One pitfall is that the standardECU cannot cope with controlling larger injectors; they must be accompanied by some form ofimproved engine management system.

80% is generally the industry’s maximum desired duty cycle for continuous operation of fuel injec-tors. It may surprise you to learn that the standard 370cc injectors are only suitable for up toapproximately 235 bhp at 80% duty cycle at normal fuel pressure. For shorter periods of time theycan be run at 90%, usually without any problems, but under no circumstances should they goabove 95%. At 90% duty cycle, assuming fuel line pressure of 58 psi, they can support around 270bhp. At 95% they can support around 280 bhp at the same fuel pressure. At 68 psi fuel pressure(this is an estimate of the pressure you might see at 15 psi boost, with a 1.7:1 fuel regulator) theycan support just over 300 bhp at a 95% duty cycle. Remember, the fuel pump will be workinghard to supply fuel at this fuel pressure, so a decent upgraded fuel pump is essential.

So 370cc injectors CAN support 300 bhp, but it is not recommended, and only for short periods.

450cc injectors can support 295 bhp (at 80% duty cycle assuming fuel pressure of 61 psi, i.e assum-ing you are running 18 psi boost). At 95% duty cycle at this fuel pressure they can support a maxi-mum of 350 bhp.

550cc injectors can support 370 bhp (at 80% duty cycle assuming fuel pressure of 63 psi, i.e assum-ing you are running 20 psi boost). At 95% duty cycle at this fuel pressure they can support a maxi-mum of 440 hp.

740cc injectors can support around 515 bhp (at 80% duty, assuming fuel pressure of 68 psi, i.eassuming you are running 25 psi boost). At 95% duty at this pressure they can support a maximumof 610 bhp.

850cc injectors can support around 590 bhp at 80% or 700 bhp maximum at 95% (fuel pressurevalues as above)

Type of injectorsThe 200sx SR20DET uses Side Feed, High Impedance injectors. The injector pushes right into the fuelrail (as opposed to being fed from the top). High impedance means they are driven by the ECUwithout the need for dropping resistors. This type of injector design is more modern than the topfeed type, and generally is very reliable, but unfortunately is more expensive to buy in terms ofaftermarket upgrades. It is technically possible to fit top feed injectors, but this will require exten-sive modifications including an aftermarket intake plenum and fuel rail. There are a few typescommonly available which can be used on the 200sx:

Unisia JECS (Hitachi): These are fitted as standard to the 200sx SR20DET, and so the larger, higherflowing injectors fit straight in the fuel rail without any further modification required. This is theeasiest upgrade. Upgrade sizes available are 450cc (reddish brown connector), 555cc (yellow con-nector), and 740cc (red connector). Sold by Nismo, Apexi, and HKS.

Denso: A couple of different designs can be fitted to the 200sx. The first type is the RX7 (FD3Smodel) injector. This requires a spacer kit and minor modification to the injector to fit in the fuelrail. They also require different connectors to be fitted to the wiring harness. They are available in550cc (purple connector) and 850 cc (red connector). These injectors, and their fitting kits, are soldby companies such as Blitz and D Speed.

Thesecond type of Denso injector will fit, but requires a different spacer kit to the first type. Theseare much longer overall than the RX7 injector. At time of writing we are not sure which car(s) theyare normally used in, but they are sold by aftermarket companies such as Sard and D Speed. Theyare 550cc and have red connectors and a large silver pintle cap at the bottom.


ECUs & MappingTo run correctly an engine needs two essential things: the correct amount of fuel to be injectedwith the air and the fuel and air mixture to be ignited at the right time. The Electronic Control Unit(ECU) controls both of these tasks.

The ECU on the SR20DET contains a 16-bit processor, which handles inputs from many sensors andcontrols a large number of solenoids and actuators. The diagram below shows most of the inputsand outputs of the ECU.

INSERT ECU DIAGRAM


How does it work?It’s actually very complicated, so only the basics will be covered here. The main inputs are the airflow meter (AFM) and crank angle sensor (CAS).

The air flow meter sits in the air-flow just after the air filter; it measures the mass of air that isflowing through it, into the engine. The voltage signal from the AFM rises as a greater mass of airflows through it per second.

The crank angle sensor determines the position of the crank, by measuring the angle of the ex-haust cam, and figuring it out from this.

The signals from these two sensors tell the ECU the load on the engine and the cranks position.Using this information the processor looks up the required injector pulse width and the time thespark plugs should be fired to ignite the fuel and air mixture (from a number of look up tables).These tables are often called maps.

As you might expect there are 2 maps contained within the ECU: One for fuelling and one for theignition timing. These maps are 2 dimensional tables containing values to make a 3 dimensionalmap. Below are example fuel and ignition tables with their 3D maps.

7 10 16 21 26 31 36 42 47 52 57 60 53 68 73 83

500 5 5 5 5 5 5 5 5 16 16 18 18 20 20 22 22800 5 5 5 5 5 5 5 5 16 16 18 18 20 20 22 221200 12 12 9 10 11 10 7 1 1 24 24 24 24 25 25 251600 11 11 9 12 9 9 8 8 8 27 27 27 27 45 45 452000 18 18 18 10 10 10 10 10 11 15 28 29 37 38 40 402400 18 18 18 10 10 10 10 10 10 10 10 27 41 45 49 492800 18 18 18 10 10 11 12 12 12 12 12 30 38 47 52 533200 18 18 18 18 13 13 14 14 17 17 27 32 40 41 54 563600 16 16 16 16 16 16 16 16 17 17 29 36 41 41 59 594000 19 19 20 20 19 19 16 16 14 17 28 35 39 41 62 634400 37 39 43 46 35 30 28 27 26 26 32 35 38 50 64 694800 33 35 37 38 34 32 30 29 28 34 41 44 50 53 75 775200 45 46 47 48 42 38 32 31 40 47 51 54 61 62 80 866000 34 35 36 39 36 36 36 42 52 59 63 68 72 86 89 906400 36 36 38 39 39 37 44 49 61 67 70 76 78 88 92 93

6800 40 42 44 44 44 47 51 55 68 72 80 80 82 91 95 96

Engine load

RPM

RPM

Engine load(=AFM input)

Fuel

ling

7 10 16 21 26 31 36 42 47 52 57 60 53 68 73 83

500 36 36 36 37 37 41 41 38 37 36 34 34 34 34 34 34800 56 46 42 39 38 36 35 34 34 34 32 31 31 31 31 311200 56 46 43 41 40 39 38 37 37 35 32 32 32 32 32 321600 56 48 44 43 42 41 40 39 39 36 34 34 34 34 34 342000 56 50 48 48 47 46 44 40 40 40 38 33 33 33 33 332400 61 51 50 50 49 48 46 41 41 41 39 36 35 33 33 332800 66 53 52 50 47 46 44 44 44 43 40 37 34 33 33 333200 66 61 58 57 54 52 52 51 51 48 43 40 36 33 33 333600 66 66 66 63 61 60 59 58 58 52 45 40 37 34 33 334000 66 66 66 62 62 61 61 58 58 52 46 41 41 39 35 354400 66 63 63 62 61 61 59 58 57 52 47 45 38 37 35 354800 61 61 61 61 61 59 58 58 54 49 44 43 42 37 33 335200 60 60 58 59 59 59 59 50 53 47 44 41 39 37 33 336000 60 60 58 58 57 55 55 53 49 45 42 40 39 36 33 336400 56 56 54 54 54 52 54 53 49 43 42 39 38 35 35 356800 54 54 53 53 53 52 53 51 50 42 41 39 38 35 35 35

RPM

Engine load


As you can see these maps are not at all linear. This is due to the physical design and characteristicswithin the engine. If any changes are made to the engine, its sensors, solenoids, or actuators thenthe tables stored within the ECU will be less than optimal. For example, if you fit a larger turbo orincrease the boost pressure more air will be delivered under certain conditions. As the ECU is notexpecting this change it will not be supplying optimal signals to the fuel injectors or spark plugsunder these conditions. This can lead to over or under fuelling or ignition that is too advanced orretarded for a given engine condition. Re-mapping or “chipping” the ECU alters the values in thesetables to, hopefully, supply the correct amount of fuel and get the ignition timing just right forevery engine condition.

What are the best conditions for maximum power?Theoretically is takes 14.7kg of air to completely burn 1kg of petrol. This is an air fuel ratio (AFR) of14.7:1. As usual, theory assumes perfect burning conditions where every hydrocarbon in the fuelburns with all of the oxygen. This mixture of 14.7:1 would give maximum power in perfect condi-tions. In real life this is not the case. When fuel is burnt in an engines cylinder some of it sticks tothe cylinder head, piston and bore and doesn’t get burnt. This un-burnt fuel gets pumped out ofthe engine and travels down the exhaust to eventually “burn” in the catalytic converter (if present).On a light throttle this AFR of 14.7:1 is what designers aim for - all the fuel is burnt with all theoxygen, which keeps emissions down to a minimum.

It turns out that to obtain maximum engine power we need an air/fuel ratio of about 12.5:1. Thismeans that for every 12.5 kg of air we need to supply 1 kg of fuel to get the most energy. This isthe full throttle AFR designers aim for when populating the fuel table. This is known as mappingthe fuelling.

Next we need to ensure that the spark happens at just the right time so that peak cylinder pressureoccurs at the right time to produce the maximum force possible on the crank. Common terminol-ogy for ignition timing is as follows: advancing the ignition means that the spark happens earlier inthe compression stroke. Retarding the ignition means that the spark happens later in the compres-sion stroke. You may think that to achieve maximum power the spark should occur when thepiston is at the top of its compression stroke, but this is not the case. The spark needs to occurearlier than this to allow the air and fuel time to start burning, which does not occur instantane-ously. The air and fuel actually starts burning as the piston is moving up in the bore on the com-pression stroke. Too much advance and the cylinder pressure gets too high before the pistonreaches the top of its stroke. This can lead to enormous cylinder pressures and cause detonation.Too retarded and the peak cylinder pressure occurs too late and a lot of the energy goes to wasteout of the exhaust.

How can we modify the fuelling and ignition timing to obtain maximum power?There are a number of ways to modify... TBC :)


ECU Upgrades

Standard ECU modified by daughterboarde.g. Horsham Developments ECU, Blitz Access, Mines VXA modification is made to the car’s standard ECU allowing a modified set of maps to be run (theseare burned permanently into an EPROM). Parts and software are available to do this yourself if youhave the knowledge. See sites such as www.925style.com for more information on this aspect.

Advantages: Allows modification of all engine parameters, including those which cannot usuallybe altered by piggyback systems. Generally the cheapest route to ECU modification.

Disadvantages: Might be tricky to re-map (usually has to be sent back to its maker). In seriouslymodified vehicles the need to retain an Air Flow Meter may cause a problem (as explained above).Unless mapped actually on the vehicle, you may still need a piggyback computer to get it “per-fect” due to differences in particular modifications, and variances between individual vehicles.

Piggyback ECUsThese are wired into the car’s ECU loom and work by modifying the signals that the ECU sends andreceives.

A’PEXi S-AFC/S-AFC II - These nice looking units (with blue screens) act on the car’s AFM signalallowing you to trim fuelling +/- 50% at a number of RPM and throttle points. Can be used toinstall larger AFM and/or injectors. It has no ability to alter ignition timing, nor any “fuel cutdefencer” function. It is however quite cheap and is very popular worldwide.

Greddy E-manage – this is a relatively new system. Out of the box, it is a very basic Air Flow “trim-ming” device similar in capability to the old model S-AFC, with 5 screws on the front to adjustfuelling at 5 RPM points. With the optional software and harnesses it becomes a fully mappablepiggyback capable of controlling ignition timing as well as fuelling. It also has built in drivers for 2extra injectors, “fuel cut defencer” function, and an idle stabiliser. An optional pressure sensorallows it to operate when the car’s AFM’s capacity has been exceeded. Unfortunately, few tuningcompanies in the UK are currently familiar with the product, although it is quite straightforward touse the software.

Dastek Unichip - Commonly offered by tuners in the UK. This operates in a similar manner andoffers similar capabilities to the E-manage. Some reports suggest it may be less able than othersystems when it comes to dealing with larger injectors due to a limited range of adjustment.

HKS Fcon S - Suspect that it has similar capabilities to E-manage, but not enough information toconfirm this. Setup must be carried out by a HKS specialist.

HKS Fcon Pro V - This takes the concept further in that it is actually a complete management sys-tem installed in the manner of a piggyback. It is actually capable of running the car without theoriginal ECU according to HKS. This system is used in many “big power” cars in Japan. Custom fitlooms for many applications. Specialist (expensive!) set up required.

A’PEXi PowerFC: a précis is needed...

Full management systems are available, such as those from Motec, Omex, DTA, GEMS, etc. Thesecompletely replace the cars standard management system. They generally require a large amountof custom re-wiring and may require other changes, such as to the ignition system. They are gettingmore competitively priced now, and it may be possible to get one installed for less than £1000.

Information that is still needed:Modified Engine internals

Layout of engine for dummies – what constitutes the ‘bottom end’, for example?


Appendix 1 - the FBU

Could I have the original version of this picture (or one like it) without the arrow & caption, please?I also need to know who to credit it to.

Appendix 2 - engine error codes

Appendix 3 - disabling the EGR

I’ll sort these out when I have a minute... :)

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