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Can you really map an RX8?

There is always constant chat and conflicting theories behind the mapping of the Mazda RX-8. Beyond maintenance benefits and dwell adjustments, can you actually extract additional horsepower from a map? We took the RotorSport RX-8 to the dyno to find out...

A simple Google search on the Internet will provide you with copious amounts of reading material on the subject to mapping and the Mazda RX-8. Topics such as adjustments for dwell timing, lowering fan temperature cut-ins, increasing OMP injection rates, removing CELs are all interspersed with claims of huge, minimum or even no BHP increases.

Having released the EasyTuning range of custom maps in June 2016 and experienced first hand the improvements in at least on-track drivability and throttle response, we thought we properly investigate whether the standard and adaptable Mazda ECU map had any disadvantages over other 'custom' maps.

The Tests

Consistency

To ensure fairness and accuracy, we employed the services of the renowned engine tuners from Circuit Motorsport in Wiltshire and used their on-site Dastek rolling road. The rolling road was operated by them and it was agreed that all power runs would utilise the same dyno configurations and variables.

The Vehicle

For the test we used the RotorSport Mazda RX-8 231 which does benefit from many performance modifications including engine porting, intake, exhaust, pulleys, flywheel/counterweight, clutch. We felt that by choosing a heavily modified vehicle, we would be better placed to see whether the individual maps actually provided any benefit. It is easy to say a map on a standard car doesn't provide any benefits and there maybe nothing to benefit, however with increase breathing, lighter rotations etc if we would gain anything then it would be on this setup.

We ran the tests on the same 9j x 17" wheels with 255/40 17 Yokohama AD08R tyres maintained to a consistent pressure throughout.

Power Runs

It was agreed we would undertake 2x power runs for each of the 3 maps we would be testing. A total of 6 power runs. For the maps themselves, we were testing:

  • Original Mazda OEM ECU Map;
  • Circuit Motorsport Custom 'Live' Map
  • Aftermarket Bespoke Custom Map

Conditions would be/were maintained throughout the runs with the same period of elapsed time between runs to ensure consistent engine and fluid temperatures.

The Results

In the back of our minds, we always had an idea of how these results would pan out - however even we were surprised by the net results - which remember, were completed back-to-back, same variables, same conditions and duplicated to ensure no fluctuations in results, spikes etc.

Original Mazda OEM ECU Map (BENCHMARK)

Maximum Power - Wheels 207.8 bhp @ 8,505 rpm Correction Factor 102.3%
Maximum Power - Engine 241.5 bhp @ 8,505 rpm Environmental Temperature 16.8 C
Maximum Torque 150.0 lbft @ 8,377 rpm Barometric Pressure 986 mBar

As our 'OEM' benchmark, we were actually surprised to see that the generic, adaptable map as supplied by Mazda on the OEM ECU netted gains on standard power - remembering a 231 model usually outputs around 170-185 whp (at the wheels) on most dynos including the one used for these tests.

Presumably we can now officially call this car a 231? And by rights, if we listen to what we told on the Internet, we should see some healthy gains with a custom map.

Circuit Motorsport Custom 'Live' Map

Maximum Power - Wheels 209.1 bhp @ 8,514 rpm Gain of 1.3 bhp Correction Factor 102.4%
Maximum Power - Engine 242.2 bhp @ 8,544 rpm Gain of 0.7 bhp Environmental Temperature 17.3 C
Maximum Torque 150.1 lbft @ 8,417 rpm Gain of 0.1 lbft Barometric Pressure 986 mBar

Not known for their rotary mapping, Circuit Motorsport are well known and respected within the Fiat, BMW, Ford and VAG world for their custom live and remote maps. This car was originally mapped by Leighton at Circuit Motorsport back in March 2016 with this very map albeit when looking at the graphs themselves, the only real benefit is an increase in torque at the mid-range, around 4,000 to 6,000 rpm over the stock OEM map.

Aftermarket Bespoke Custom Map

Maximum Power - Wheels 201.3 bhp @ 8,377 rpm Loss of 6.5 bhp Correction Factor 102.5%
Maximum Power - Engine 234.7 bhp @ 8,437 rpm Loss of 6.8 bhp Environmental Temperature 17.7 C
Maximum Torque 147.7 lbft @ 7,925 rpm Loss of 2.3 lbft Barometric Pressure 985 mBar

This 'aftermarket' bespoke and live road tested map had the better 'bum-dyno' feel in terms of throttle response and driveability on track. From the 'bum-dyno' alone you would have expected this to results in higher power and torque figures over both the stock and Circuit Motorsport maps - however the data tells otherwise!

The torque curve itself was far linear producing the most power of all 3 maps from 5,000 rpm up to 7,250 rpm where the Circuit Motorsport map produced more power and the 'aftermarket' map began to tail off which also contributes to the lower rpms for each max power result. This map also didn't suffer the usual drop around 6,500 rpm. These factors could explain why the map ultimately feels better when raced on track, as the car is usually maintained above 5,500 rpm but is potentially negated by the loss of power from 7,250 up to the adjusted rev limiter at 8,600.

Our Summary & Conclusions

It is important to note we are not claiming these results as gospel. We know too well that each engine, its level of modification and configuration behave differently to different environments and maps. Nor are we claiming any 'wins' in terms of our figures or the performance of this engine and build. We are more than aware that dyno figures can vary, configurations and variables come into play frequently and other considerations. This experiment is purely to test the theory of mapping a normally aspirated Mazda RX-8 231.

Leighton's summary following his own mapping of this vehicle and an evaluation of the stock RX-8 map is that only very minimal gains can be made on the stock configuration. The biggest benefits to be made are from maintenance settings such as OMP rates, fan temp, cold start rev limiter and throttle response and to this extent we agree.

For road-going vehicle with no or very little track use, we cannot find a benefit to 'power' mapping your Mazda RX-8 231. There is ultimately NO power to be had over and above the stock Mazda OEM map and in some cases, power outputs can be reduced.

For track, performance and race vehicles however, there is an argument that 'torque' mapping a Mazda RX-8 231 could be beneficial, but only to level out the production of torque and therefore power within the optimum power band range you will be operating the engine. For track/race cars spending the majority of their time above 5,500 rpm then this would be the ideal scenario, however on longer or faster circuit when the upper end of the rev range may be an important factor, care would need to be taken to ensure torque and therefore power is not lost at this critical phase.

So what have we learnt?

  1. The stock Mazda OEM map is MORE than adequate to support any number of performance modifications.
  2. If you want power 'bragging' rights from your RX-8, then leave the map alone.
  3. Even advanced 'mapping' only extracts minimal power gains over the stock ECU map. We don't believe these to represent any value for money for the cost.
  4. OMP rates, cold start rev limiters, fan temp switch timings and throttle responses can all be uprated for as little as £45 adding drivability and increased maintenance to your RX-8.
  5. Only consider custom mapping your RX-8 if you want to maximise your performance between 5,000 and 7,000 rpm.
  6. We need to look at our race car maps further to see if we can fine tune the 'aftermarket' map to maintain power up to the rev limiter rather than dropping off from 7,250 rpm.

Thanks for Leighton at Circuit Motorsport for the use of their dyno and expertise.

2017 March Mapping compressed

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