ETK Performance

🔥 BACK IN STOCK – V8 OM628 400 CDI High-Pressure Fuel Pump 🔥

⚡ Limited availability – these usually sell out quickly.

Looking to push your Mercedes CDI build further? The OM628 V8 high-pressure pump is now back in stock.

✔️ Perfect upgrade for OM646 / OM647 / OM648 / OM611 / OM612 / OM613 engines
✔️ Designed to deliver much higher fuel flow for performance builds
✔️ Ideal for bigger injectors, hybrid turbos, and high-power setups
✔️ Proven solution when aiming for 400+ HP capable fuel systems

👉 Get yours here:
https://ecutuningkaunas.com/product/v8-high-pressure-om628-400-cdi-pump-for-mercedes/

Many clients asks why we stopped using bullet bolts in our hybrid turbochargers?

We conducted many tests, and that’s why we stopped using them a long time ago. We’ve received many questions asking why we no longer use them - so here’s a post explaining our decision.

What does the compressor actually want?
At the inducer (compressor inlet), the goals are:
Uniform axial velocity
Minimal pre-swirl
Maximum static pressure recovery
Stable, attached flow into the blade leading edges

Anything that disrupts this hurts:
Compressor efficiency
Surge margin
Why is the bullet-shaped nut worse?
It creates a stronger stagnation region.
A pointed nose forces the flow to decelerate earlier and more abruptly.
This creates a larger stagnation pressure zone upstream.
The flow then accelerates rapidly around the nut.
Rapid acceleration plus curvature increases boundary-layer separation risk.

A flat or short nut:
Creates a smaller, more compact stagnation zone that reattaches faster.
The bullet nut also:
Increases wake length and turbulence
Produces a long, low-pressure wake
Sends this wake directly into the inducer eye
Causes velocity non-uniformity entering the blades

The bullet shape:
Acts like a flow director
Converts axial flow into unwanted radial and tangential components
Increases pre-whirl, which compressors do not want at the inducer
A blunt nut disturbs flow less directionally.
Reduced effective flow area
Even if the bullet has a lower drag coefficient:
Local acceleration around it increases Mach number
Higher local Mach → higher losses (especially near choke)
The inducer “sees” a smaller effective inlet

This results in:
Slightly worse choke flow
Earlier efficiency drop at high mass flow
Why OEMs use the “ugly” nut

OEM turbo designers optimize for:
Total pressure loss
Stability across the entire compressor map
Manufacturing repeatability
CFD and test data consistently show:
Short, blunt, axisymmetric hub features perform better
Especially in high-Reynolds-number, low-Mach internal flows

If the bullet nut were better:
OEMs would already be using it everywhere
They don’t—because it doesn’t help.

Final thoughts

At our ETK headquarters, we have balanced many turbochargers, and bullet-shaped bolts are significantly harder to manufacture compared to stock bolts. They are also much heavier.

Internal flow is not governed by drag coefficient alone. In a turbocharger inlet, pressure recovery, wake behavior, and flow uniformity dominate. A bullet-shaped nut increases wake length, induces swirl, and worsens inlet flow quality—reducing compressor efficiency instead of improving it.

Basically: it looks fast, but performs worse.

We apologize for the grammar, as it is not our native language.

BMW 306/D2 EDC16C1 204/218 HP standalone kit.
ForSolenoid injectors with vacuum or electronic turbo management.
Stage 1 or stage 2 tuning option can be programmed with 4 bar map sensors.

https://ecutuningkaunas.com/product/bmw-306-d2-edc16c1-204-218-hp-standalone-kit/