prj tuning

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Archive for the ‘Tuning’ Category

LPG – liquid petroleum gas.

Most of us have probably heard about it, let’s see how production cars are converted to it, and what is usually done wrong.

I will talk about the 4th generation LPG system, where extra holes are made in the intake manifold and an injector is added for each cylinder.
Technically the system is pretty simple…

How it works

From a mechanical standpoint we have a high pressure tank, from which the liquid gas goes through an evaporator, that takes it to it’s vaporous form. From the evaporator it is distributed to the injectors via a common rail.
After the injectors are nozzles, which are sized to a certain size, according to calculations. So the same injectors can be used for many different applications and the injected quantity is adjusted by sizing the nozzles.
The evaporator also serves as a pressure regulator for the fuel, and is usually connected to a vacuum line in the inlet manifold.

Electronically most LPG ECU‘s are fairly simple. The cars petrol injectors are re-wired through the LPG unit, and the LPG unit just gets the reading from the main ECU in regards to the injector pulse. After it gets the start of the injector pulse it can correct it to be longer or shorter. It can also switch the gasoline injectors on or off.
The LPG ECU tends to have a gas pressure and temperature sensor and also allows for correction based on LPG temperature, as the density of a vapor fuel is affected quite a bit by temperature.

The way these systems are normally installed, is that they are set up to turn on only after a certain engine temperature is reached (the car only starts on petrol), and then it is calibrated with a narrowband sensor so, that the mixture is roughly stoichiometric in the cruise area. The ignition timing is not touched in most installs, and the car feels down on power. The nozzles are also rarely big enough for the car to work correctly in the entire range.

How it should be done in an ideal world

The best way is to use the additional LPG ECU to only provide correction for fuel temperature and switching settings. The engine management should be done by the already existing ECU by facilitating “map switching” based on whether LPG is used or not. This means that a signal should be taken and fed into the ECU.

A real world example

The car I will talk about is an old Audi V8, with the PT 3.6 liter engine, 2nd generation Motronic management with dual distributors and a 4th generation “Tornado” LPG system.

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Ruslan’s UrS6


  • K26 turbo (bigger turbo planned)
  • 044 fuel pump
  • 630cc Siemens Deka injectors
  • 4th generation LPG system
  • RS2 exhaust manifold
  • Automatic switchover of mapped ignition, boost and fuel in Motronic ECU for LPG
  • Up to 30 degrees of timing advance under boost on LPG
  • Decreased fuel consumption and increased power on LPG

Tuning a Diesel


This post will be a little bit different to the one-car-per-post format. I want to give people a little overview of what a “Stage 1″ tune is and just describe the general approach to chip tuning.

One of my cars is MY2000 Opel Omega-B 2.5TD, and I will use this one as an example.

What makes these cars a little special, is that the engine is lifted from a BMW. It is the intercooled version of M51D25, slightly detuned.
In return, BMW’s using this engine are fitted with GM’s AR35 automatic transmissions.
However, Opel in their infinite wisdom used the AR25 box on the diesel and the AR35 on their petrol engines. The 25 and 35 are just torque limits – 250nm and 350nm accordingly.

I bought the car with a blown trans for peanuts, and luckily the only difference between the AR25 and AR35 are uprated internals. So I acquired an AR35, retained the torque converter and bell housing from the AR25 and hey presto, I have a transmission that can handle 350nm. After fixing the boost leaks (the intercooler on this Omega was like swiss cheese) the car can be tuned for more torque and power.

First step was to find the ECU and check how boost is controlled.
The ECU turned out to be in the fusebox under the hood, and just slides out. The connector is a typical JPT-55 used in most Bosch applications of the 90-s (remember, the engine was developed in 1991!), and the control unit itself is a Bosch MSA-11 type or in other words – ancient by even 2000′s standards when the car was built. Forget any flashing, only the manual approach will lead to results.
Around the turbo there are no fancy solenoids – the boost is mechanically controlled by a spring to about 1 bar.
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Steve’s RS2


  • K26/K27 #6 turbo
  • H-Rods
  • EV14 510cc injectors
  • 044 fuel pump
  • Wagner EVO exhaust manifold
  • 3.3 sec FATS
  • 9.5 sec 100 to 200 km/h


Chester’s UrS4



  • K26/K27 #6 turbo
  • RS2 EM
  • 440cc injectors
  • HRC 290 LPH fuel pump
  • 4.3 sec FATS with 1900kg weight.

Toomas’ UrS4



  • K26/K27 #6 turbo
  • Block bored to 83mm
  • Toyota Supra 7M-GTE pistons, machined
  • BMW M50B20TU connecting rods
  • MC crank, machined
  • FMIC
  • RS2 exhaust manifold
  • 3″ turboback exhaust
  • Autobox to manual box conversion
  • Single mass flywheel with SRE clutch
  • RS4 MAF conversion
  • 440cc injectors
  • Uprated fuel pump
  • 2 bar at 3300 rpm in 3rd.
  • 250 km/h trap speed on One Mile Challenge
  • 380 hp at 55C IAT. 400hp and 600+ nm at 45C IAT. Realistic IAT is 20-30 degrees lower, so approx 450hp.



Kirill’s UrS6



  • 3071R / K26 #6 turbo
  • Fully balanced engine, but stock rods
  • Head ported
  • Uprated clutch
  • RS4 MAF conversion
  • Bosch 044 fuel pump
  • Siemens Deka 630cc injectors
  • 7A camshafts
  • Blitz FMIC
  • RS2 exhaust manifold
  • Modified inlet manifold
  • So far the car has run 12.6 1/4 mile with full interior, including climate control.
  • 441 PS and 574 NM on dyno


  • RS2 Hybrid turbo
  • Thick headgasket
  • 480cc Delphi injectors
  • Stock engine
  • A lot of suspension mods :)
  • The car was running some generic chips, and the result was 375 PS and 544 NM at 2 bar of boost.
  • After re-mapping the ECU, it made 392 PS and 577 NM at 1.8 bar boost on the same dyno. This also means lower IAT and EGT.

Richard’s Black RS2



  • Garrett 3071R turbo with 0.82 A/R hotside
  • Wagner Evo T3 manifold
  • Siemens Deka 560cc injectors
  • Bosch 040 fuel pump
  • Stock engine
  • 430 PS and 610 NM at the crank on the MRC dyno.