ITB Fuel Injection 101 | 2.5L V6 Alfa Romeo 155 TI DTM [TECH NUGGET]

When you spot a 420HP Alfa Romeo 155 TI DTM car at the Goodwood Festival of Speed the gentlemanly thing to do is shoot a quick video of it, and in this one you can learn about the individual throttle body setup.

If you want to make as much power as possible from an NA engine, there are a few challenges involved when it comes to squeezing every last Nm of torque possible in the right places.

One common option is to tune the length of your inlet trumpets, aka velocity stacks to suit your preferences or even the track you are racing at. A shorter trumpet, or stack, will give you better performance at high RPM, which of course means a longer trumpet will be better for low RPM performance and it’s not uncommon to find a mixture of both lengths on some setups to try to maintain the best of both worlds.

Another feature found on many track dedicated NA setups such as the 1995 2.5L V6 Alfa Romeo 155 DTM of Alessandro Nannini which via the aid of fuel injectors directly above the trumpet inlets produced approximately 420HP at 11,500rpm.

The advantage of this setup is that the fuel and air have more time to mix before reaching the combustion chamber which helps the mixture burn better, producing more power at wide-open throttle (aka WOT or ‘giving it some jandal’) and high RPM. The trade-off, and there’s always one, is that when the driver is off the gas and the inlet is closed, the fuel will pool and then enter the engine in liquid form which is much harder to burn and can also cause other issues down the line.

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