Power by stage
Stage 1 to 3 are the tuners' and turbo makers' own published figures; European tuners quote PS (1 PS is about 0.99 hp). Stage 4 is a thin community range, because few built-engine results are published. Real results depend on fuel, weather and the individual car.
Names with an arrow go straight to that part's product page for this car.
Stage 1: Software only
+29 to +89 hpFlash tunes need the engine computer unlocked first: Weistec says every car needs it, and Posaidon says it depends on the model year. The second limit is the CPC, a separate control unit that holds torque limits and the speed limiter; EST says a new, unused CPC coded to your car is the only safe way to lift those limits. Plug-in modules from RENNtech, RaceChip and DTE leave the factory software alone.
Typical cost: $1,499–$2,580 (Eurocharged, Weistec, RENNtech); gearbox tune $1,000 more; RaceChip €609; EST with a new CPC £1,550 including VAT.List prices, Sept 2026, before shipping, import tax and fitting.
Stage 1 tunes compared
| Tune | Fuel | Claimed power | Claimed torque | Notes |
|---|---|---|---|---|
| Weistec W.1 | Premium (no octane given) | 510 hp | 490 lb-ft | +125 hp over Weistec's own stock figure; ECU unlock sold separately |
| RENNtech Power Module | — | 490 hp | 398 lb-ft | Plug-in module; a bypass plug returns the car to stock |
| RaceChip GTS 5 Black | — | 490 PS | 540 Nm | Plug-in module (+69 PS / +40 Nm) |
| EST Stage 1 Full Solution | 99 RON | 460–480 hp | 560–620 Nm | Includes a new CPC plus engine and gearbox tunes |
| mcchip-dkr Stage 1 | — | 470 PS | 580 Nm | Find the car in the tuner's database |
| Posaidon 465 | 98 RON | 465 PS | 560 Nm | Software only; road approval not included unless stated |
| Eurocharged Stage 1 | — | 450 hp | 406 lb-ft | Works with an intake and a cat-back exhaust |
| Brabus PowerXtra B45-450 | — | 450 hp | 550 Nm | Figure from an authorised Brabus retailer; Brabus' own page is gone |
| DTE PowerControl RX | — | +49 PS | +94 Nm | Plug-in module |
Recommended with Stage 1
- Engine computer unlock flash tunes
Weistec M139 ECU tune (unlock)Posaidon M139 tune (ECU unlock)
Needed before a flash tune; plug-in modules don't need it.
- New CPC or CPC tune recommended
EST Stage 1 CPC packageWeistec M139 ECU tune (unlock)
Without it, the CPC's torque limiters can hold back an engine tune.
- Gearbox (TCU) tune optional
Weistec 8G-DCT TCU tuneEST Stage 1 ECU + TCU
No maker says it's required at Stage 1. Weistec sells it for higher torque limits, and EST includes it to avoid clutch slip.
Stage 2: Intake, downpipe and exhaust
+49 to +99 hpStage 2 adds a downpipe and an intake, with a file written for them. On European cars the downpipe is the hard part, because it sits in front of the particulate filter (OPF/GPF): many downpipes bypass it, and those are for off-road use only. Later W177s also have an exhaust-temperature sensor in the downpipe, so buy the version that matches your car.
Typical cost: Weistec downpipe $899 or Milltek £990; water-methanol kit $1,600; EST Stage 2 £2,150–£3,750.List prices, Sept 2026, before shipping, import tax and fitting.
Stage 2 packages compared
| Package | Fuel | Claimed power | Claimed torque | Required hardware |
|---|---|---|---|---|
| EST Stage 2 | 99 RON | 490–520 hp | 620–700 Nm | EST x Cobra sports-cat downpipe, new CPC, engine and gearbox tunes |
| mcchip-dkr Stage 2 | — | 500 PS | 590 Nm | Hardware not listed in the database entry |
| Eurocharged Stage 2 | — | 470 hp | 420 lb-ft | Intake, downpipe and cat-back; sold for off-road use |
| Weistec W.2 | Premium | +145 hp | +179 lb-ft | Race exhaust; gains are over Weistec's own stock figure |
Parts list
- Intake required
Eventuri intake (W177)RENNtech x Eventuri airbox
Eventuri claims 15–18 hp; the same intake fits the CLA45 and GLA45.
- Downpipe required
Weistec M139 downpipeMilltek downpipeEST x Cobra Sport downpipeAkrapovic downpipe with cat
Weistec's needs its W.2 tune, and Milltek's includes an OPF/GPF bypass and needs a Stage 2 remap.
- Exhaust optional
Akrapovič Evolution Line
Akrapovič claims +6.4 kW; its road approval is void if you fit a downpipe.
- Water-methanol injection optional
Weistec water-methanol kit
Weistec claims 20–80 hp, depending on the tune.
Stage 3: Hybrid turbo
525–600 hpStage 3 upgrades the factory turbo, usually as a hybrid built on the original. Posaidon's RS525 claims 525 PS on 98 octane and can come with German road approval. EST, MACHGRADE and Weistec claim 545 to 600 hp, but all say fuel, cooling and a custom tune must come with the turbo.
Typical cost: hybrid turbos $2,999 (Weistec) or €1,470–€4,499 before VAT (TTE, MACHGRADE); EST570 £6,995–£8,550.List prices, Sept 2026, before shipping, import tax and fitting.
Turbo upgrades compared
| Kit | Fuel | Claimed power | Claimed torque | Notes |
|---|---|---|---|---|
| Posaidon RS525 | 98 RON | 525 PS | 600 Nm | Software and hardware; German road approval available |
| EST570 | — | 545–570 hp | 640–680 Nm | Hybrid turbo, full intake, downpipe and charge-cooler kit |
| MACHGRADE 550 / 600 | — | 550 / 600 hp | — | The 600 needs a bigger turbine side and new oil and coolant lines |
| Weistec W.3 | — | 590 hp | — | Rebuild of your own turbo; custom tuning required |
Parts list
- Hybrid turbo required
MACHGRADE M139 turboTTE560 turboWeistec W.3 turbo (M139)MuchBoost M139 hybrid turbo
Sold with, or tuned for, a file written for that turbo.
- Gearbox tune and new CPC required
Weistec W.3 turbo (M139)EST Stage 1 CPC + TCU package
More torque needs higher gearbox limits and a CPC that doesn't cut it back.
- Charge-cooler upgrade required
EST x ProAlloy charge cooler kit
EST lists its charge-cooler kit as the minimum for EST570; owners in hot climates report heat soak on the factory cooling.
Stage 4: Built engine
600–650+ hpFew built-engine M139 results are published, so this is a thin community range. The biggest turbo claims stop at about 590–600 hp (Weistec W.3 and MACHGRADE 600), and forged pistons and rods are sold for Stage 3 and racing builds. Owners on a UK forum say that 600 hp and up works on the stock engine internals, but that about 700 on the stock gearbox clutches won't last.
Parts list
- Forged pistons and rods required
IRP forged pistons and rods
Sold for Stage 3 builds and dedicated racing use.
- Bigger turbo and fuel system required
MACHGRADE M139 hybrid turboWeistec W.3 turbo (M139)
With the fuel and cooling upgrades the turbo maker specifies.
- Gearbox clutches and cooling required
The dual-clutch gearbox is the limit at this power.
Quick answers
- How much horsepower does a stock Mercedes-AMG A45 S have?
- 421 hp from the factory.
- How much hp does a Stage 1 Mercedes-AMG A45 S make?
- Tuners claim 450–510 hp at Stage 1, up from 421 hp stock (Stage 1 options).
- How much hp does a Stage 2 Mercedes-AMG A45 S make?
- Tuners claim 470–520 hp with a Stage 2 file and the parts it needs (parts list).
- How much hp does a Stage 3 Mercedes-AMG A45 S make?
- Tuners claim 525–600 hp at Stage 3: hybrid turbo (Stage 3 parts).
- How much hp does a Stage 4 Mercedes-AMG A45 S make?
- Stage 4 is the top of the ladder for this car: built engine. The biggest builds claim 600–650+ hp. Check which fuel each figure needs: Israel sells 95 and 98 octane only (Stage 4).
- How much does a Stage 1 Mercedes-AMG A45 S cost?
- List prices: $1,499–$2,580 (Eurocharged, Weistec, RENNtech); gearbox tune $1,000 more; RaceChip €609; EST with a new CPC £1,550 including VAT.
What we'd do
On an A45 S we would stop at Stage 1 and spend the rest of the budget on making it hold. Software alone claims 450–510 hp from 421 hp stock. Stage 2 claims 470–520 hp, so the top of the range moves by only about 10 hp, and it asks for a downpipe that sits in front of the particulate filter. Here that pipe needs approval, and a bypassed filter fails the test.
A full Stage 1 on this car is three pieces of software, not one: the engine file, the CPC that holds the torque limits, and the gearbox. EST's package (£1,550 including VAT) fits a new CPC coded to the car plus engine and gearbox files. Weistec sells them apart: $1,500 for the tune, $1,699 to reflash the CPC and $1,000 for the gearbox, $4,199 before the computer unlock. None of these tuners has an Israeli dealer on its own list. If no shop here can do the CPC, we would take RENNtech's plug-in module ($2,580, 490 hp claimed): it leaves the factory software alone and a bypass plug returns the car to stock.
Buy in this order. First a health check: Mercedes' service bulletin on broken valve springs covers every M139, so a rough idle or a misfire gets looked at before any tune. Then the software, written for 98, the best fuel sold here (EST's figures are on 99 RON). Skip the downpipe, the hybrid turbos of Stage 3 and any figure on E85.
The thing to watch is heat. Owners warn against long full-throttle runs on a plug-in box above 30 °C, and EST lists an upgraded charge cooler as the minimum for its turbo kit. Log intake temperature through your first Israeli summer before you ask for more.
Tuning it in Israel
- New price in Israel
Still sold new. The importer's price table lists the AMG A 45 4MATIC+ (the page shows the A 45 S) from ₪549,000 plus a ₪5,499 licence fee, ₪555,399 in all (mercedes-benz.co.il, checked November 2026). At launch it cost ₪519,900 (icar, 22 December 2019).
- Parts from abroad
At the Bank of Israel representative rate of 26 October 2026 ($1 = ₪3.078), with 18% VAT and purchase tax, about 40.66% combined on car parts and car electrical devices above $75 (our import guide):
- RENNtech plug-in module $2,580 × 3.078 = ₪7,941, × 1.4066 = about ₪11,170.
- Weistec downpipe $899 × 3.078 = ₪2,767, × 1.4066 = about ₪3,892.
Both before shipping, which is taxed too. A downpipe is an exhaust part and needs an approval at import. A flash tune or a CPC reflash is a service, not a parcel, but a new CPC unit sent from abroad is.
- Fuel
Use 98. Posaidon's 465 PS file is written for 98 RON, and EST's Stage 1 and 2 figures are on 99 RON, which isn't sold here, so ask EST or any tuner for a file written for 98. Weistec gives no octane but says low-octane fuel hurts output and can hurt the engine. Never run a file written for a higher octane than the fuel in the tank (95 vs 98 after a tune). E85 figures don't apply in Israel.
- Regulation 380 and the test
The Road Safety Authority reads Regulation 380 as covering engine software, so record a tune like any other change (how approval works). The Ministry's list names a special exhaust outright: a downpipe or cat-back needs a part with a lab prototype certificate, a licensed installer and an entry in the licence. Akrapovič's Evolution Line is road-approved, but Akrapovič says that approval lapses once a downpipe is fitted. Many M139 downpipes bypass the particulate filter, which fails the test. Passing the test doesn't make an unapproved change legal. Fixed noise fines are ₪250, or ₪350 for driving without an effective silencer.
- Where to get it done
Of the brands in this guide, only the exhaust makers list Israeli dealers: Milltek lists Top RPM (Holon) and Akrapovič lists Frontech (Tzur Yigal). Weistec, RENNtech, EST, Posaidon, Eurocharged and the box makers list no one here. These are the brands' own lists, checked October 2026; we have no link with any of them.
Prices and rules checked 2026-11-10.
Also useful: tuning shops in Israel, the import tax calculator and the annual test checklist.
What owners ask
- Does my A45 S need a new CPC for a tune?
Usually yes, for a flash tune. Owners explain that the CPC (central powertrain controller) holds the torque limits and the speed limiter. A CLA45 S owner was told by his tuner that a stock CPC can pull an engine-only tune back toward stock power over a few months, and that the original unit can't be reprogrammed, so a new one is coded to the VIN. An owner relaying Posaidon's answers wrote that the A45 S CPC has a 500 Nm limit. Weistec reflashes your own CPC ($1,699); EST fits a new one. Ask which method your tuner uses.
Sources: aclassclub.co.uk: A45 tuning discussion, page 14 (2021), aclassclub.co.uk: A45 tuning discussion, page 28 (2021), Weistec: M139 tune and CPC
- Do I need a gearbox (TCU) tune at Stage 1?
Owners disagree. One wrote in 2021 that Stage 1 doesn't need a gearbox tune and only a turbo upgrade does. An owner who relayed Posaidon's explanation wrote that once the engine and CPC are remapped, the gearbox computer must be remapped too, to raise clutch pressure, and that this allows 600 Nm; Posaidon's plug-in box stays at about 560 Nm. EST includes gearbox software in its Stage 1 to avoid clutch slip. Our rule: if the file claims more torque than about 560 Nm, budget for the gearbox software.
Sources: aclassclub.co.uk: A45 tuning discussion, page 10 (2021), aclassclub.co.uk: A45 tuning discussion, page 28 (2021), EST Performance: A45 S Stage 1 and 2
- A plug-in box: can the dealer see it, and is it safe in hot weather?
Nobody in the thread could say for sure whether a dealer can find traces once a box is removed; one owner noted that the engine computer records out-of-range values. Fitting one needs a sensor that is only reachable from under the car with the undertray off. The same owner, in Australia, warned against full throttle with a European-calibrated box above 30 °C. Posaidon, as quoted there, says its box cuts boost on long full-power runs and can't be combined with a downpipe. RENNtech's module comes with a bypass plug to return the car to stock.
Sources: aclassclub.co.uk: A45 tuning discussion, page 53 (2022), aclassclub.co.uk: A45 tuning discussion, page 28 (2021), RENNtech: Power Module for M139
- Are broken valve springs on the M139 caused by tuning?
Mercedes doesn't say so. Its October 2022 service tip covers all M139 engines: the complaint is an engine light, rough running, hard starting or stop-start trouble, with misfire codes on cylinders 1 to 4, and the surest check is to remove the cam cover and look at the springs. On the owners' forum, one member said the cases he had heard of were all stock cars, while another said higher revs and boost are the main causes of spring failure. If your car idles rough or logs a misfire, have the springs checked before you tune it.
Sources: Mercedes-Benz XENTRY TIPS LI01.30-P-075439 (via NHTSA, 2022), aclassclub.co.uk: M139 engine broken valve spring(s) (2023)
- What should I ask a shop before it tunes my A45 S on a dyno?
Ask about the dyno itself. An experienced owner pointed out in 2023 that the A45 S needs a four-wheel-drive dyno whose front and rear rollers are linked to turn at the same speed, which many dynos can't do. He also said engine power figures from different dynos can't be compared, so use the same machine before and after and treat the result as a before-and-after check. His other two questions for the shop: which tuning software it uses for this generation, and how it deals with the CPC.
Sources: aclassclub.co.uk: A45 tuning discussion, page 76 (2023)
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Questions to ask the shop
- Does my engine computer need an unlock, how is it done, and what does it cost?
- Do you supply a new CPC? Without one, are the torque limits still active?
- Is a gearbox (TCU) tune included, and what torque does it allow?
- Which fuel is the file built for (95, 98 or 99 RON, or E85), and is there a safe map for the fuel I can buy?
- Do you log intake temperature and timing on hot, repeated pulls, and how do you deal with heat soak?
- Is the downpipe or particulate-filter work legal for inspection here, and what happens to my warranty?
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