DIY ecu mapping with ByteFlash

"Using the ByteFlash handheld ECU engine tuning/remapping device"

"Following negative feedback from our readers and our own experiences with Rob Bentley at JR TUNING in Kent we are not recommending this company, until all outstanding issues, debts, complaints have been resolved to our satisfaction."

This is a review of the handheld ecu flashing device from ByteFlash.

A bit of background first, Waynne, the owner and creator of TorqueCars wanted to see what the options were on tuning his main family car an Audi A3 2.0 TDi 140bhp BKD engine.

20-TdiAfter much research a simple tune/remap was decided upon, this would effectively add a large power gain without requiring extensive modifications to the engine or affecting fuel consumption or reliability.

Ideally a switchable tune/remap would be ideal, one which allows a car to be economical in the daily commute and a performance option which allows the car to become a lot more fun to drive.

There are many options out there and plenty of engine tuning/remapping companies offering a wide range of choices and options so we'll shortlist here some of the main options and look at the chosen solution.

Option 1) Tuning box (or specifically a piggy back ECU or digital tuning box), these simply plug into the engine ECU and alter the timing/fuelling and boost parameters. This offered quite good figures for a relatively small outlay. Sadly though it is not a custom solution, only generic mapping can be performed but there are a few boxes that give you some switches allowing you to fiddle around and settle for the ideal map but most will just dump more fuel into the engine.

Option 2) A full tune/remap of the ECU, there was even a few specialists offering a switchable tune/remap controlled via the cruise control menu. I liked this option but it would have meant taking my car to the mapping company. I would also need a cruise control switch to be fitted. There is also the risk that the map will be erased when Audi service the car if they update the software.

Option 3) A handheld ECU programmer which allows the user to upload a chosen map or restore the car to normal. Downsides of this are that most of these ECU flashers only provide generic maps and Waynne wanted to get the most out of his car, especially when using it off road on track days. This allows the owner to tune/remap a car at will and overwrite any factory resets performed by Audi.

After much looking around we were offered the ByteFlash unit from JR tuning in Kent.

The ByteFlash handheld engine tuning/remapping unit seemed to tick the most boxes for our needs.

As an Audi fan the owner of JR tuning knows the range well. All the maps provided are custom tweaked and if necessary a rolling road session can be arranged to create the perfect map.


The units are reusable too, meaning you can reset the ByteFlash for your next car and start over again without needing new hardware.

The old map will need to be reverted to standard before you sell the car or your unit will be "locked" to the old car.

An economy map, performance map and track day map were provided in our unit and tailored to Waynne's very exacting requirements.

It is worth noting that the standard performance map positively transformed the car, thanks in part to JR tunings knowledge of the Audi engines.

When the Byteflash unit is plugged into a computer it downloads a software update, so this is best done before you connect the unit to your car.

Turn off the ignition, plug in the unit and turn the ignition key so power comes up but do not have the engine running.

We plugged in the unit, and selected the nearest model of car we could find (A3 2.0 TDI 8P) and downloaded the standard map into the unit from the Bosch Ecu.

The file is sent over to JR tuning, you should specify your requirements, are you wanting it for towing, do you need a restricted top end for economy purposes, a low power valet mode, performance tune, blended tune or a fast road track day tune? Further tweaks and preferences can be taken into account by JR tuning creating a custom map. If you have other mods to your car a full rolling road setup can be arranged and a custom map set can be created for your car.

It is worth noting on the PD engines that economy figures are pretty good as standard and the ECU does not have as much control over the fuelling compared with the later CR engines (the fuel rail pressure cannot be controlled).

For this reason I would recommend you opt for a performance map, where economy figures are pretty similar to the eco tune and better than standard.

A full track day map is also nice to play with and this maximizes the fuel delivery to wring out every drop of power.


All maps and tweaks are designed to maintain reliability, we would recommend more frequent oil changes and the use of high quality oil on any mapped car.

A short while later we were emailed a flash file, which we uploaded to the Byteflash unit and took this to the car.

We found a blank white screen sometimes when plugging this in to the car.

Run the engine briefly then try again, this cleared up the white screen.

A welcome screen comes on in a few seconds on the Byteflash unit. Choose the map required and flash it to your car, this process takes few minutes.

The car will beep and show up warning lights, this is normal so don't worry. Instructions on the screen will tell you when to turn on the ignition (don't start the car though) and when to turn it off.


The Byteflash unit will verify the map installed and tell you to turn off ignition and remove the unit.

After flashing the car will need about 15 miles to get used to the new map, you'll hardly notice this process thanks to the careful initial setup but as each car is different the ECU will need to adjust itself for optimum performance.

TorqueCars will publish a full review with results and performance figures here, but we need time to collect them.

We will run each map on a full tank and report back.

An initial 0-60 run on the Economy map yielded a 0-60 time of 7.6 seconds, down from the quoted 9.3 but still getting massive wheelspin at 3000rpm!

The car felt much quicker in the mid range with plenty of pull.

Economy figures are too early to tell but not that impressive but JR tuning have tweaked the economy map further for me. Economy wise there is little difference on the economy map over standard but the extra power at high RPM is nice, there is an annoying flat spot around 1500-2000rpm which is even more noticeable on the race map. We have emailed JR tuning about this but not had a response or any further feedback. Economy on the race map is around 10% worse than standard and the exhaust is quite smokey at full throttle but there's loads of power on offer.

The race tune turns in a very respectable 7.3 seconds 0-60 and gives about 43 mpg on my usual monthly commutes. There seems to be a massive torque surge around 3000 rpm, almost like there is another engine coming on line! 5th & 6th gear cope ok with low speeds of around 30mph, testimony to the huge amount of torque on offer.

Turbo whine is becoming a problem so I expect I will at some point need to update

A tune/remap on the 2.0 TDI BKD engine will yield a respectable power increase, not just a spike but a linear power gain through the whole rev range. MPG has not actually changed to any noticeable degree on the economy map which is a disappointment. This is not surprising really as the PD engines do not have a great deal of fuel delivery control compared to the later CR units. The extra power does lend itself to providing a few more MPG on motorway runs or if driven very carefully but in the real world we notice more of a difference filling up with Vpower diesel compared to the standard lower Cetane fuel.

Following negative feedback from our readers and our own experiences with Rob Bentley at JR TUNING in Kent we are not recommending this company, until all outstanding issues, debts, complaints have been resolved to our satisfaction.

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2 Responses to “ByteFlash Handheld DIY ECU mapping”

  1. Raymond Power says:

    This company JR tuning and owner Robert Bentley is a scammer fraud. I paid money and don’t receive my items. BeWare! !

  2. Barry Shereston says:

    I echo what Raymond Power has said:
    This company JR TUNING and owner Robert Bentley is a scammer fraud. I paid money and don’t receive my items. BE VERY AWARE!!

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