I need to replace one or both of my HPFP's. Does anyone know what is the maximum horsepower that the stock HPFP's will flow? Thanks.

 

The M178 with stock TCU tune and stock HPFP’s are good for around 600 WHP, so about 730 to 750 BHP.
The pumps are good for more HP but the TCU holds the HP back without a tune for torque limits and clutch pressure etc.
If you’re going to do an ECU and TCU tune without changing the fuel pumps you’ll get close to 650 WHP. With new pumps up to 800 WHP. With injectors, turbos, race gas etc. you can get up to the 1000 mark.

 

great info and thanks very much. that just saved me the 3500 to buy the spool kit, haha. i'm only looking to get to the 700-750 bhp mark, so i'll just replace my oe hpfp's with new oe ones. thanks very much!

 

My pleasure! New pumps and a quality ECU/TCU tune and you’ll be right where you want to be.

 

M178 engine series has forged internals from factory, right?

 

correct. gearbox/clutch will be the achilles heel with big power.

 

ok, can the Getrag 750 stand up to 750 Nm without issue?

 

That’s its max rating.

 

then is it a "yes" (?)

 

I’d say yes, I’m sure there’d be tolerances beyond the max rating.

 

Yes, Max official Torque supported by our Getrag = 750Nm per Getrag's own published specs.

Unofficial Torque ceiling = ~820Nm per secondary sources from within Getrag, but the closer/more frequent this is reached, higher probability of Failure.

 

I would be interested in seeing a listing of all of the internal components with material used and method of manufacturing.
I have a feeling that the pistons are hypereutectic alloy.

 

many factors will determine your maximum for the OE pumps. The fuel octane, the oxygen content of the fuel, whether you want to use any additional margin (ie meth), the tuner, etc.
I’m running about 250hp more at the wheels over stock with the stock pumps. I wouldn’t push it any further and still have a safety margin.

 

A fair few tuners in the UK are happy to get a GTR running over 900nm, seems way over what the box can handle, on paper!

 

Let me weigh in with some technical guidance that could save your transaxle (and maybe save you money on new FP)

The factory transaxle is officially rated for 750 crank Nm (553 lb-ft), with an unofficial upper tolerance of around 820 Nm, as reported by MBNRG. To maximize horsepower while maintaining reliability, the safest approach is a custom tune that flattens the torque curve across the mid-to-upper RPM range.

With the GTC and GTR OE turbo setups, an ideal strategy is to hold torque at roughly 750–780 Nm between 3,000–5,500 RPM, then allow a controlled rise to 780–820 Nm from 5,500–6,500 RPM. Achieving this requires precise boost management, with peak boost pressure in the 24 psi range. This level of balance is difficult to dial in, and in practice, most well-executed calibrations I’ve seen—including my own setups—tend to plateau near 680 crank hp @ 6,500 RPM (assuming ~12% drivetrain loss from wheel to crank).
I don't have numbers for the GTS, but since it uses smaller turbos, it will be difficult to reach the 750nm and I don't see any benefit for a HPFP.

A critical safeguard is torque limiting in the lower gears: specifically, torque should be capped between 1,000–5,000 RPM in 1st and 2nd gear to prevent drivetrain shock loads.

The OE fuel pump is adequate to support the above power levels without starvation.
This combination provides a balance of peak performance, drivability, and transaxle longevity, rather than chasing numbers that risk premature hardware failure.


However, if you’re planning to push beyond these limits, you’ll need supporting upgrades:

• Reinforced clutch system (e.g., Dodson)
  
• Strengthened transaxle internals (e.g., PTG billet solutions)
  
• Higher-capacity turbos (with the tradeoff of added lag)
  
• High-pressure fuel pump (HPFP) upgrade
  
• Coordinated ECU and TCU calibrations
  
  

Before chasing more torque and horsepower on this platform, the first consideration should be use case. The value of additional output is very different depending on how the car is being used:

• Street / Daily Driving: Beyond ~750–780 Nm, the gains are marginal because traction becomes the limiting factor. Extra torque will mostly translate into drivetrain stress, heat, and shorter component life rather than usable performance on public roads.
  
• Track / Road Course: Here, usable power is about balance and consistency. A flat, predictable torque curve that carries strong but controlled power to redline is far more valuable than brute-force torque spikes. This makes the car more manageable mid-corner and improves lap-to-lap consistency without overloading the transaxle.
  
• Drag Racing / Roll Racing: Higher peak power numbers are beneficial, but only if the transaxle and clutch are upgraded. In this scenario, additional torque is useful, but the priority is ensuring driveline reliability and maintaining efficient power delivery throughout the run.
  

In short:

• If the goal is longevity and balanced performance, you want controlled torque (750–800 Nm) with a linear delivery.
  
• If the goal is maximum peak numbers for straight-line racing, then you need significant hardware upgrades to keep the platform alive at 820+ Nm.
  

Without a clear use case, chasing additional torque/horsepower becomes more about numbers on a dyno sheet than performance you can actually put to the ground.

 

If you check GAD Motors in Germany and their recommended power stages for the AMG GTS, you’ll notice that a high-pressure fuel pump (HPFP) upgrade is only specified when stepping up to larger-than-OE turbos.
For stock turbos, it isn’t required—so don’t waste time or money on an HPFP unless you’re going that route.

https://www.gad-motors.de/50aqawgh9a...-gt%2Fgts-m178