Abarth Racing UK have been working in conjunction with Turbo Technics to develop a game-changing turbocharger for both road and race cars. Through extensive testing, the expertise of Abarth Racing’s Head Engineer Andy Dawson has combined with TT’s 35 years manufacturing turbochargers to produce a ground-breaking product.
The back story
The standard twin cam engine with Bosch ME7.9 ECU gives 135bhp with boost of 0.8bar as standard and 0.95 in Sport mode. This is the engine that all Abarth 500s, Abarth Puntos and early Alfa Mitos were type approved with in 2008; it was in production until early 2015.
The Esseesse upgrade and the early 595 cars had a simple ECU upgrade that altered the boost to 0.95bar as standard and 1.2bar in Sport mode and increased the power to 160bhp, the limit of the IHI turbo. It is possible to achieve nearer to 170bhp with this specification by overfuelling, but this comes at the expense of driveability.
The next level of power output from the twin cam engine came when a bigger turbo was fitted; the Garrett GT1446 from the Multiair version of the same engine family. This is the Punto Esseesse conversion and gives just under 190bhp as standard at 1.6bar of boost. The conversion consists of: an exhaust manifold that is dimensionally the same but made from better material, new injectors, new pressure sensors, a remap, a new hose from the air cleaner to the turbo, a longer turbo oil feed pipe, a longer oil drain pipe and a new exhaust downpipe/catalytic converter.
There are two pressure sensors, the boost sensor in the pipe from the intercoolers to the throttle body (below the battery on a standard 500) and the MAP sensor in the inlet manifold. The standard sensors are good to 1.6bar (2.6 absolute) and the upgraded units are good to 3bar (4.0 absolute). The ECU programme (maps) must be changed for the upgraded sensors so that the program gets the correct pressure info to give the correct fuelling and ignition timing.
The 190bhp is good with a standard air cleaner and exhaust. Testing has shown a big exhaust (63mm with motorsport cat and large silencer in the tunnel) gives an extra 3bhp, and a much nicer exhaust note!
The next stage is what Turbo Technics have now developed in consultation with Abarth Racing UK. The team has experimented with remapping, but found it to be a costly and mostly fruitless exercise. Fitting a Garrett T25ish turbo gave good power (240+bhp) but the response and bottom end weren’t good.
Three iterations further on, the specification is fixed and the unit is being produced.
The turbo is a direct replacement for the GT1446 and we expect it to give 260bhp with a standard air-cleaner and 275bhp with a foam filter picking up cold air (not one of the popular kits that pick up hot air from the back of the engine bay!) We have good maps and are still making them even better.
Intake temperature is something we have watched closely during the development process; a key takeaway has been that a front mount intercooler isn't a necessary add-on for road use. The standard pair of intercoolers perform the job perfectly well: they don’t interrupt the air flow into the water radiator, they have plenty of capacity and are keeping the intake temperature at less than 20 degrees above ambient. For motorsport where there isn’t an air con radiator then a big front mount makes sense, but it is superfluous for road use. The popular readily available front mount is only 1100 mm2 the standard coolers have a cross sectional area of 1410mm2, the Punto unit used on the factory rally cars is 1660 and the one used on Marten Bonner’s successful Abarth 500 racer is 2800.
To confuse issues, the latest cars have a new Bosch ME17.3 ECU. The prediction is that the reduction in exhaust back pressure will release the same extra power the Euro 4/5 engine spec 180 gives; 180 will become 190 with Euro 6 mapping in the new ECU. We presume that the reduction in exhaust back pressure will release the same extra power that we have on the Euro 4/5 engine spec. We will be doing this test later this week.
Fitting the big turbo to a standard car with no other changes is something that we have tried, 135 becomes just under 180 and 160 becomes just over 200. Currently the test car, a 70,000 mile example has done over 1000miles and no problems even with the IHI exhaust manifold.
We can also provide remaps for the turbo, having acquired the necessary kit and proven through extensive testing that it works. Together, ARUK and TT are formulating the best way of providing these remaps, so that our customers benefit from the turbo in the most seamless way possible.