Can I buy the RTD4 on its own?

Not on the site. It comes with every DEFI tune, and the tune price already includes it and the HP Tuners licensing. If your car was flashed in the shop and you want to add one, call: HP Tuners licenses each vehicle per interface, so the car needs licensing again on the new device, and we will tell you what that is before you commit.

What does the RTD4 cost?

It is $350 of every DEFI tune price, which already includes it — there is no second invoice, and shipping it to you is included.

I already own an MPVI or an RTD4. Do I need another?

No. If it is an MPVI2, MPVI3, MPVI4 or RTD4 linked to HP Tuners TDN, you can buy the calibration alone — $500, or $1,100 on the supercharged and halo platforms — and supply the licensing yourself. The RTD4 is our choice; on an MPVI we lock the file with HP Tuners’ tune security.

No. Logging, uploading, reading codes and flashing are all done in HP Tuners’ TDN app on your phone.

Can I use it on more than one car?

Yes, with a licence for each vehicle. HP Tuners licenses every vehicle separately on each interface, so a second car is a second licence.

Tuning interface · included with every DEFI tune

The DEFI RTD4

The device your calibration arrives on — and the line back to us for every change after it. The hardware is HP Tuners’. What makes it worth having is the tuner on the other end.

Find your vehicle Call (951) 405-4465

Included in every DEFI tune price, with the HP Tuners licensing. Shipping it to you is included.

The DEFI Motorsports RTD interface device and package contents

Why get your interface from DEFI

You are buying the tuner, not the box

Anyone can sell you the hardware. These are the things it does because a calibrator is on the other end of it.

Revisions without a visit

A revised file arrives in the TDN app and you write it to the car from your phone — in your driveway, or in the pits.

Datalogs from your phone

Start a log, drive, upload it. No laptop. We read what the engine did on your fuel, in your climate, under your right foot.

Pump gas and E85, both on board

Every DEFI tune includes both maps. They sit on your device and you flash the one that matches the tank.

Parts added later

A supercharger or a cam next year is a revision to the same device — and HP Tuners does not charge licensing again for re-flashing the same vehicle on it.

Codes read from the app

Check-engine light? The app reads the trouble codes; send them with a log and we tell you what it is and whether it is safe to drive.

Your tune stays your tune

The RTD4 cannot open a tune file in HP Tuners’ editor, so the calibration on your car stays the one we wrote for it.

Three ways to get the tune on the car

Flashed in the shop, on an RTD4, or on your own

	Flashed in our shop	DEFI RTD4 — our choice	Your own interface
Revisions sent to the car remotely	No — the car comes back	Yes	Yes
Datalogs from a phone, no laptop	No	Yes	Depends on the device
Add your own interface later	Licensing again	Already on the car	Already on the car
The tune file can be opened	—	No — the RTD4 cannot open it	Locked with tune security
Licensing	Included	Included	Yours — you supply the credits

Your own interface: an HP Tuners MPVI2, MPVI3, MPVI4 or RTD4 linked to TDN. Licensing per HP Tuners: each vehicle is licensed separately on each interface.

Setting it up

Set it up once

01Create an HP Tuners TDN account and install the TDN app on your phone.
02Plug the RTD4 into the diagnostic port and pair it. Let the first update finish.
03Choose LINK YOUR TUNER and enter the invite code we send you.
04Read the car in the app and sync files — that puts your stock file with us.
05Your calibration comes back to the app. Write it, drive it, send us a log.

What is in the DEFI Motorsports RTD package: the interface device and its OBDII cable

The DEFI Motorsports RTD interface and cable laid out, as supplied

Guides

What owning one looks like

Before you buy

Questions people ask

Can I buy the RTD4 on its own?: Not on the site. It comes with every DEFI tune, and the tune price already includes it and the HP Tuners licensing. If your car was flashed in the shop and you want to add one, call: HP Tuners licenses each vehicle per interface, so the car needs licensing again on the new device, and we will tell you what that is before you commit.
What does the RTD4 cost?: It is $350 of every DEFI tune price, which already includes it — there is no second invoice, and shipping it to you is included.
I already own an MPVI or an RTD4. Do I need another?: No. If it is an MPVI2, MPVI3, MPVI4 or RTD4 linked to HP Tuners TDN, you can buy the calibration alone — $500, or $1,100 on the supercharged and halo platforms — and supply the licensing yourself. The RTD4 is our choice; on an MPVI we lock the file with HP Tuners’ tune security.
Do I need a laptop?: No. Logging, uploading, reading codes and flashing are all done in HP Tuners’ TDN app on your phone.
Can I use it on more than one car?: Yes, with a licence for each vehicle. HP Tuners licenses every vehicle separately on each interface, so a second car is a second licence.