Straight answers

The honest answers

What does a tune actually cost me, beyond the money?

Longevity, fuel economy and emissions compliance. More power means more cylinder pressure, more heat, and more stress on parts specified for the factory figure. Economy usually falls. The vehicle will not pass a California smog inspection in the tuned state. Any shop telling you gains are free is not being straight with you.

Will my car stay smog-legal?

No. Calibration alters emissions-related engine management. Our work is sold for off-road and competition use. We would rather you hear that here than at a testing station.

Do I need supporting modifications?

Often, yes — and the "you do not need a tune for that part" advice you have read online is usually wrong in the other direction too. Fuel system capacity, cooling, clutch capacity and knock margin all constrain what a calibration can safely ask for. We will tell you where your combination runs out before we take the job.

Will you turn work down?

Yes. If the combination will not support what is being asked, or the vehicle is not mechanically healthy, we say so rather than take the money and hand back a compromised result.

Buying a tune

Can you ship a tune for my car?

For 285 of the 775 vehicles in our catalog, yes. The rest are supported only as in-shop work because their ECMs cannot be reached over the Tune Delivery Network. Search your vehicle and the page states which applies before you buy.

How much does a tune cost?

Every price is built from three figures: DEFI Custom Tuning $500, a Mainline dyno session $350, and the DEFI RTD4 $350, plus the HP Tuners licensing your vehicle needs. A remote tune is tuning + RTD4 + licensing. A dyno tune on a factory ECU the RTD4 supports is all three, $1,200 + licensing. Supercharged and halo platforms such as the C8 Z06, Hellcat, TRX and GT500 take $900 of tuning instead of $500. A locked ECU or TCM adds its air return from HP Tuners, once per order: $100 2-day or $140 next-day. Dyno testing alone is $350. Every vehicle page shows its exact figure.

My ECU is locked. What happens after I order?

First we email you an HP Tuners order number on our account. Do not ship anything before that email arrives, and write the order number on the OUTSIDE of the package in marker — HP Tuners works to the order number, and a module with no number attached cannot be matched to your job. Then you remove the ECU (and the TCM, if that is locked too), package it and ship it to HP Tuners in Illinois at your cost. They unlock it and air-return it from Illinois straight to you — on a shipped order it never passes through us at all. We pay that return when we place the order, so it is billed when you order, once per order: $100 for 2-day air or $140 for next-day.

Why do I have to buy an RTD4?

Because we never flash an engineered DEFI calibration without one. The tune travels to the RTD4 encrypted and is written to your ECU locked, so it cannot be read back off the car and copied. The RTD4 is yours to keep, and it is how datalogs reach us and every revision reaches the car. There is no file-only option and no credit for an interface bought elsewhere.

Is the E85 map extra?

No. Every tune includes a pump gas map and an E85 map at the same price. Flex fuel, one calibration that adapts to any blend through a sensor, is $300 more, and a map beyond the pair, such as race fuel, is $300. E85 needs a fuel system that can keep up, and it costs fuel economy.

Why are there no returns?

Licenses are consumed on application and bind permanently to one ECM. They cannot be recovered, transferred or resold by us or by the platform vendor — so after application there is genuinely nothing to return. We disclose this on the product page and require an explicit acknowledgement at checkout, before payment.

What if I need a revision after delivery?

Send a datalog and tell us what fuel was in the tank. We revise and publish the update to the same device you already have. Most vehicles need at least one revision and that is normal.

The dyno

Why does a hub dyno matter?

Because a roller dyno measures power after it has passed through the tire, so tire compound, pressure and temperature move the number. Our Mainline ProHub bolts to the hubs, which removes that variable and makes results repeatable between visits. Repeatability is the only property that makes a before-and-after comparison mean anything.

Why is my number lower than the one another shop showed me?

Possibly because it was measured differently. Correction standards, dyno types and ambient conditions all move the figure without anything changing on the car. We publish our conditions and correction factor on every sheet precisely so this can be checked rather than argued about.

Do I get the full sheet?

Always, including runs we were not happy with. Cropping to the peak is how the industry hides work it does not want compared.