What do you think Mr Richard ?
____________________________________________________________
This auction is for a new RIAT sensor, a rapidly responding version of the standard Toyota Celica GT4 (ST205 model) inlet air temperature sensor. The RIAT sensor replaces the standard Toyota sensor and is supplied with a new harness to connect with the engine loom. Heatshrink is supplied to make a professional installation.
This product:
eliminates heat soak- a weakness of the standard sensor
reduces the chance of detonation damaging your engine
improves economy
improves transient torque and power
improves your, or your tuner's, ability to map your engine closely - leading to further power and economy gains.
This sensor was developed for use on RX7's to cure a problem with the standard Mazda sensor. The same problem can be found on Toyota Celica GT4's and the fix is the same - replace the sensor with a modern open element type sensor.The sensor requires a thread adapter, supplied but not shown.
The sensor has the following resistance values:
Temperature Resistance
deg C Ohms
-10 9397
20 2500
80 323
The sensor can be fitted by a home mechanic and requires only the original sensor to be removed which is accessed from the top of the engine. No special tools are required, just a socket set and a soldering iron.
Read on for futher details...
What does the inlet air sensor do?
It sits in the airflow passing through the plenum, just downstream of the throttle bodies. This is the best place to measure the temperature of the intake air before it hits the injectors and the combustion chambers. The air temperature and its pressure are used, by the ECU, to calculate its density – and therefore the mass flow rate of air entering the engine. The correct amount of fuel is then added to burn with the air and create the combustion pressure that generates the engine torque. It is easy to understand that the ECU needs accurate data to determine the fueling, and that’s where the RIAT comes into play.
When the air is cold, it is dense, the ECU adds more fuel and the engine makes more torque, and more power. Cooling is achieved with chargecoolers, intercoolers and water injection methods. During stationary periods, radiated head from the radiator, engine block and turbo units heat the intake air, intercooler/chargecooler and eventually the whole intake tract. When this occurs to a standard sensor, it absorbs this heat and retains it for minutes after the rest of the system has cooled down. It is quite possible for the vehicle to complete a lap of a race track, or a 1/4mile run before the sensor accurately reflects the system temperature. During this period, the ECU has been fuelling the car incorrectly, thinking the air is hot – a lean condition that could lead to detonation. Tuners, and Toyota, compensate for this by running on the rich side of what is safe, which leads to poor economy and sooty exhaust during acceleration.
The RIAT will enable tuning closer to optimum, giving you greater fuel economy, power, and allowing real time management of water injection trigger points. It will also allow you to ‘see’ peak temperatures that may have been masked by the slower responding sensor. Do not be surprised if your car surges away from heat-soak situations as the ECU responds the inrush of cold air and fuels accordingly.
Finally, the sensor is an automotive grade component, designed specifically for this purpose. It will not fail and carries a lifetime guarantee. The harness is manufactured to suit, and is again automotive grade with the highest temperature resistance available. It will not melt in the heat of your engine bay. You will receive an installation document that explains how the component assembles to your vehicle, and how it is possible to check the calibration of the new sensor against the old, to ensure you are not risking your pride and joy, FENNE DEVELOPMENTS understands how important your investment is to you.
What is the problem with the standard sensor?
Two years ago I found that the inlet temperatures I was seeing (Apexi ECU with commander) with my RX7 FD3 (series 3 1992 onwards) did not tie in with what I knew to be happening. The inlet temperature should have fluctuated as I accelerated through the gears as the turbos passed through their range of efficiency. I was running stock twins, at 1.1 BAR, so they were running above their normal operating range. On inspection I found the standard air temperature sensor to be heavily shielded with a large time constant. This means that any change in temperature will not register quickly with the ECU. If you have wondered why your water injection, or a sudden increase in speed (and intercooler efficiency), does not translate into variations in inlet temperature, then the standard inlet temperature sensor is the reason.
What are the gains?
The graph (picture) shows the differences between the two sensor types when hot and cold air are applied. The RIAT sensor (in blue) can be seen to respond very quickly. Registering the initial step increase in temperature. At 20,000msec the Mazda Sensor is lagging the RIAT sensor by 15°C and fails to reach the system temperature before the heat source is removed. At 140,000msec the step inputs become larger and faster, simulating accelerating and braking around a race track. The RIAT sensor responds quickly, recording peaks of 45°C and lows of 10°C. The standard Mazda sensor is heatsoaked at this point and records a peak of 34°C and a low of 31°C. A clear demonstration of the benefits to be had by moving to the RIAT sensor.
Because the RIAT sensor responds so much faster, the car can be mapped leaner. Why? Because your ECU will now see the surge of cold air as the water injection kicks in or the air starts to flow externally through your intercooler, it is therefore no longer necessary to add a blanket rich map, to protect the car from heatsoak events. The RIAT sensor just does not heatsoak. At all. Why is heatsoak dangerous? When the standard sensor heatsoaks, the ECU thinks the air is 70°C. It thinks the air is hot and thin, with not much oxygen. As you accelerate away from heatsoak, joining a motorway for instance, the boost triggers the water injection and the intercooler starts working efficiently. Inlet charge temperature drops to 5°C. The ECU doesn’t know this yet as the sensor is still reading 69°C, 68°C, 67°C slowly catching up with reality. The engine is now breathing cold, dense, oxygen rich air. This causes a lean condition taking you closer to the detonation limit and potentially overheating your turbine blades in your turbo. Of cause this doesn’t really happen, your experienced tuner will have mapped your car rich because he knows that when he maps engines lean- they detonate and break rotor tips. So your engines safe, but drinks fuel and your friends tell you she blows black smoke during hard acceleration.
Is it safe?
Yes. UK tuner, Dragon Performance, has tested the unit and recommends it, commenting that “the difference is like night and day. The logs show it better than I can explain, the speed and accuracy is in another league, highly recommended.”
This sensor is manufactured by an OE supplier, has been used extensively for 5 years and has NEVER failed in service. Beware of cheap copies. These may not have been developed for the demands of the intake manifold system. Contact with fuel vapour, high temperature and vibration may age them prematurely.
Is there a fuel saving to be had?
I have calculated the theoretical possible fuel economy increase. I have used a generic temperature correction curve and assumed a worst case heat soak of 40 degrees C. To explain, the temperature correction curve is that which the ECU uses to determine how much fuel to put in, dependant on incoming air temperature. i.e hotter air=less fuel.
The heat soak is from my own experience, I have seen 70°C on a cool day, so 40°C is quite conservative. Others may have seen more or less?
The reduction in fuel for a 40°C increase in inlet air temperature is 6%. It can be argued therefore, that to guard against a lean condition, a 'safe' map would be at least 6% rich due to the sensor lag.
To conclude, a 6% reduction in the over-rich condition should be possible.
The fuel saving works out at £13.50/1000miles (20mpg, £4.5/gallon).
Why does this sensor make mapping easier?
When mapping a car you are altering the ignition timing and the fuelling at each load point. You examine the data output in four ways - knock, AFR (Air fuel ratio - lean/rich condition), EGT (Exhaust Gas Temperature), combustion pressure. With this information you can adjust the timing and fuelling to suit your requirements of power, economy, and drivability.
When rolling road mapping, the demands on the intercooling system are extreme as airflow may be down on normal road/track conditions. This can cause the inlet air to run hot and cold depending on your load state.
If the inlet air sensor is not following the actual inlet air temperature, the ECU will not be able to match the fuelling correctly and this will cause rich/lean conditions. This will actually make it more difficult to map, as you will need to wait longer at each load point for the sensor to 'catch up'. Straining your engine for longer than necessary, and increasing the risk of detonation.
It is actually easier to map a car with a faster acting inlet temperature sensor, as it is for any sensor. The better your input, the faster the ECU can respond and the steadier your outputs will be. Its important to understand that the ECU is using the inlet temperature to adjust the fueling automatically, all the time the engine is running. You will not be able to 'see' any difference unless you specifically look at air inlet temperature.
Its also important to note that if your car does heat soak, the ECU steps up the fuelling (at about 60-70°C) to reduce the detonation risk. This impairs fuel economy and makes the car sluggish, and the risk of plugs fouling is increased. This sensor eliminates the heatsoak at source. You may still see high temperatures, this will be due to an overstressed or poorly constructed intercooling assembly.
Is a re-map required?
The sensor is safe to use without a remap. It is an automotive grade unit and each sensor has it's calibration checked. There is a small risk that your own sensor has drifted out of tolerance and when your car was mapped, the fuelling was adjusted to suit this 'drift'.
The risk of damage is very small for two reasons:
1. A 40°C 'drift' is worth half an air fuel ratio. That means that if your sensor was reading 40°C cold, then replacing it with a correct sensor will cause your car to run 6% leaner (half and air/fuel ratio). If your sensor was this far out, your tuner would (should) have noticed as your inlet temp would have been -20°C in an ambient environment and replaced your standard sensor. If your car has not been remapped, the new sensor will correct any problems with your existing sensor.
2. Included in the instructions with the product is a simple method to check the calibration of your sensor. You will require a volt/resistance meter to do this, or have a laptop link/commander so that you can read what the ECU is 'seeing'.
This is a great product and those of you with Apexi Commanders and laptop links will see the benefit immediately. Don't be dismayed if you see new peak temperatures - they were there all along. Now that you are aware you can target them with upgrades to intercooling. If your car is due a mapping session, fitment of the sensor will allow your map to be leaner without risking the engine. Saving you fuel and giving you a punchy, tight response.
The RIAT sensor will be dispatched within 48hrs, postage is included in the auction price. The RIAT sensor is guaranteed for life. Should the sensor fail, simply return the unit and a replacement will be dispatched.
___________________________________________________________
