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IndyCar
INDYCAR: Honda’s Turbo Change Explained
Learn about the background and technical aspects of the change INDYCAR allowed to the single-turbo setup currently used by Honda.
Marshall Pruett looks at the physical changes to INDYCAR's single-turbo setup, what it means for performance and how it has performed so far for Honda in Brazil. (Photo: BorgWarner)
For those of you who were fortunate to miss the nasty politics that took place at-times between CART engine manufacturers, the over-the-top scenario that played out between Chevrolet, Honda and the IZOD IndyCar Series during the past two weeks served as a reminder at just how unpleasant things can get when manufacturers squabble over the minutia.
To quickly replay what took place, BorgWarner, after being selected as the sole turbo supplier by INDYCAR, looked to create single- and twin-turbo options for the new 2012 engine providers. The goal, in simple terms, was to equalize the performance and the efficiency between the two layouts, allowing manufacturers some flexibility to choose the turbo layout of their choice without experiencing a performance disadvantage.
Using its line of “EFR” turbo units it already had in inventory, BorgWarner did what made sense, selecting a bigger, single-turbo unit and also smaller twin turbos that were meant to deliver as close to half the performance (each) of the single turbo as possible.
Add the performance and efficiency of the twin turbos together and, theoretically, they would match what the single turbo offered. The problem was--and although we’re talking about very small percentages--the off-the-shelf solutions for both turbo layouts did not provide exactly equal performance and efficiency, which was brought to the attention of BorgWarner and the series by Honda in March of 2011.
Although the call for a different housing for the single turbo has come to a head recently, it’s worth reiterating that the request for a more equal single-turbo housing was first made 13 months ago.
Things start to go haywire politically when, according to reports, Chevy was not included in these early discussions. The relative surprise for Chevrolet and Ilmor after learning a new turbo housing was being pressed into service at Long Beach helps to explain Roger Penske’s uncharacteristic and fiery response to the situation.
Threats of legal action and an eventual protest ensued from the Chevy camp, which led to INDYCAR reversing its decision and requiring Honda’s teams to re-install the original turbo housing in the Long Beach paddock.
Some procedural mistakes by INDYCAR in 2010 were highlighted during the protest, but the series’ original decision to allow Honda to use the new turbo housing was reinstated for Brazil onwards.
So, all of the procedural bits aside, the physical changes to Honda’s new BorgWarner turbo housing, which has led to plenty of speculation, offer some direct benefits that should establish more parity between the two layout options.
Turbos, as we’ve discussed, use exhaust gasses to spin a turbine—the “hot side” of the turbo—to draw in and compress air via a separate turbine on the “cold side” of the turbo, at which point that air is then forced into the intake plenum. Without getting too technical, the opening of the inlet for each side--hot and cold side--coupled with the radius of the snail-like turbo housing, gives a ratio, the area over radius (A/R) figure that’s used to determine how much air the hot or cold side can flow.
BorgWarner’s John Norton once again helped with a few explanations from the turbo manufacturer’s point of view, and how larger A/R turbo cover should perform.
“The reason why the compressor cover change is particularly applicable to INDYCAR is because they are operating at low boost levels and high flows which push the operating points to a strange area of the map,” Norton explained.
To quickly replay what took place, BorgWarner, after being selected as the sole turbo supplier by INDYCAR, looked to create single- and twin-turbo options for the new 2012 engine providers. The goal, in simple terms, was to equalize the performance and the efficiency between the two layouts, allowing manufacturers some flexibility to choose the turbo layout of their choice without experiencing a performance disadvantage.
Using its line of “EFR” turbo units it already had in inventory, BorgWarner did what made sense, selecting a bigger, single-turbo unit and also smaller twin turbos that were meant to deliver as close to half the performance (each) of the single turbo as possible.
Add the performance and efficiency of the twin turbos together and, theoretically, they would match what the single turbo offered. The problem was--and although we’re talking about very small percentages--the off-the-shelf solutions for both turbo layouts did not provide exactly equal performance and efficiency, which was brought to the attention of BorgWarner and the series by Honda in March of 2011.
Although the call for a different housing for the single turbo has come to a head recently, it’s worth reiterating that the request for a more equal single-turbo housing was first made 13 months ago.
Things start to go haywire politically when, according to reports, Chevy was not included in these early discussions. The relative surprise for Chevrolet and Ilmor after learning a new turbo housing was being pressed into service at Long Beach helps to explain Roger Penske’s uncharacteristic and fiery response to the situation.
Threats of legal action and an eventual protest ensued from the Chevy camp, which led to INDYCAR reversing its decision and requiring Honda’s teams to re-install the original turbo housing in the Long Beach paddock.
Some procedural mistakes by INDYCAR in 2010 were highlighted during the protest, but the series’ original decision to allow Honda to use the new turbo housing was reinstated for Brazil onwards.
So, all of the procedural bits aside, the physical changes to Honda’s new BorgWarner turbo housing, which has led to plenty of speculation, offer some direct benefits that should establish more parity between the two layout options.
Turbos, as we’ve discussed, use exhaust gasses to spin a turbine—the “hot side” of the turbo—to draw in and compress air via a separate turbine on the “cold side” of the turbo, at which point that air is then forced into the intake plenum. Without getting too technical, the opening of the inlet for each side--hot and cold side--coupled with the radius of the snail-like turbo housing, gives a ratio, the area over radius (A/R) figure that’s used to determine how much air the hot or cold side can flow.
BorgWarner’s John Norton once again helped with a few explanations from the turbo manufacturer’s point of view, and how larger A/R turbo cover should perform.
“The reason why the compressor cover change is particularly applicable to INDYCAR is because they are operating at low boost levels and high flows which push the operating points to a strange area of the map,” Norton explained.
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