BMW E46 2.8 Turbo M52TU

I had a BMW brought in to have Invent EMS and LPG installed and tuned.
The car is very nice and well maintained, doesn't look its age at all.
Motor M52TUB28 (2 vanos)
Forged connecting rods, CR 8.5
Turbine Garrett 3076GTX

The LPG components were selected with the aim of achieving maximum power on gas.

KME Twin reducer. This is actually two reducers connected together. The declared power is 410 hp.
There was only one possible place for the reducer: under the intake pipe. We had to suffer a lot while we placed the reducer and 8 hoses to it (2 gas supply, 2 gas output, 2 reducer heating, 2 vacuum lines to both halves of the reducer).

The pressure lines to the reducer, MAP-sensor, pressure regulator are plastic. Due to the rigidity of the walls and large internal cross-section, the response to the throttle pedal is significantly improved.

An 8mm plastic tube from the bottom is connected to two valves. Then two 6mm plastic tubes are connected separately to each half of the reducer.

Hana Blue injectors and T-pieces

We have assembled the gas rail. In the final version, we shortened the hoses from the nozzles to the connections.
Gas supply is provided from both sides of the rail to ensure better pressure stability at high power.
The gas supply injectors are placed so that they come out almost in the middle of the intake pipe. The tips of the injectors ( unfortunately the photo is lost) are cut off at an angle to create the effect of gas being extracted from the injector by the airflow.

The arrangement of the injectors is obviously inconvenient from a maintenance point of view. However, we chose it because our priority was to maximize output. This design allowed us to position the injectors as close to the valves as possible and reduce the length of the hoses. This in turn allows the high-speed Hana injectors to flow more freely.

After installing the gas filling system, we encountered an issue with the reducer freezing. Liquid circulation only began after warming up the engine and opening the thermostat, which was also observed in the turbine cooling line. After several days, we identified the culprit as the turbine cooling system. The water supply to the turbine was connected from the cabin heater, and the drain was made into the cylinder block. The M52TU motor has a coolant pump located at the bottom of the cylinder block that pumps the coolant upwards. As a result, the pressure of the liquid in the cylinder block is the same as that in the turbine supply hose. However, the motor assemblers did not consider this important detail, resulting in a blocked fluid circulation through the turbine connection. The hose connection was redesigned, resulting in normal fluid circulation in the reducer and turbine.

The car was originally equipped with standard injectors and a Chinese adjustable pressure regulator, which maintained a rail pressure of 6 bar.
However, there were suspicions of pressure instability from the beginning. After a few attempts to adjust the valve, it began to seriously fail, not holding the pressure and even cutting off the fuel at times when the pedal was released. The standard regulator was reinstalled on the rail, which resolved the issues with engine starting and pressure surges.

A customer brought in Bosch 440cc green injectors, which are often used in tuning projects.

These injectors don't fit the BMW manifold well. It's all about the spray angle. The picture schematically shows the spray pattern of the BMW injectors in the manifold. The injector seat is made almost parallel to the runner, in a special recess. The injector has a downward spray slope of about 10 degrees.

And this is what happens when you install conventional injectors. The spray will not reach the inlet valves, and a lot of gasoline will remain on the walls.

Since we already had injectors and planned to primarily use gas, we decided to use what we had to avoid wasting time. To optimize injector performance, we developed an interesting solution: tilting the injectors. We calculated the angle of inclination required to aim the injector at the inlet valve.

The boost was limited to 0.4 bar by a spring and the wastegate was looped. To improve the system, we installed an eletronically controlled solenoid. Initially, we used a Mercedes adsorber valve, but it proved to be too weak and would occasionally stick at pressures above 0.9 bar. Therefore, we replaced it with a more robust adsorber valve from the RX8. The issues with boost control have since been resolved.

We installed Invent EMS-2.

It controls coils, petrol and gas injectors, dual vanos (intake and exhaust), boost control solenoid, fuel tank level gauge (details below), and automatically switches between gas and petrol. There's also automatic launch control, which helps inflate the turbo on startup.

The place for the ECU was found in the standard ECU box. There is a free slot available. The standard wiring is used to the maximum, most of the connections are made right next to the ECU. Outside the box there are only wires for gas injectors, commutators, relay, wastegate solenoid, map sensor and EGT sensor.

I've been looking for a place for the gas/gasoline button for a long time, because in E46 it's not easy to place it so that it doesn't look ugly. To find a place on the panel is half the trouble, it is necessary to have enough space under the panel to install the button. After much consideration, the button was mounted like this.

The toggle switch turns on the gas mode. The lamp on the toggle switch shows waiting for switching to gas (slowly blinking), working on gas (lit up), gas is finished (quickly blinking).

We managed to make a gas level indicator using Invent EMS. The gas level sensor was connected to the analog input. The required signal to the dashboard was generated using PWM. In the circuits of petrol level sensors (there are 2 of them here) we cut in a relay that switches between standard sensors and our signal generator. When you turn the toggle switch to the "gas" position, the instrument panel shows the remaining gas. When the toggle switch is turned to the " petrol" position, the gauge shows the remaining petrol.

The car was brought in for tuning without an external oil radiator. While driving in the city, the oil temperature stays around 100 degrees, which appears to be sufficient. However, after a few minutes of fast driving on the highway, the temperature exceeded 110 degrees. It is recommended that the motor assembly team should have insisted on the installation of a radiator, especially since the M3 has one despite having noticeably lower power.

The car arrived with a standard ECU, but the airflow meter was disconnected and the fuel pressure was set to 6 bar. As a result, the car emitted black smoke from the exhaust. It is surprising that the spark plugs were able to keep up with this. The car drove well above 4000 RPM, when the turbo kicked in, but below that range, it was underwhelming, producing only 160NM of torque at 3,000 RPM.

Results after tuning. Solid line - gas. Dashed line - petrol.