Racecar Engineering – September 2019

30 http://www.racecar-engineering.com SEPTEMBER 2019

direct area where performance has been

improved is of course in the combustion

chamber, but the difference is not night and day,

it is again many small things. Friction reduction

is also an area we have worked on.’

A major change for Honda is that it is

supplying two teams in 2019, for the first

time since Super Aguri collapsed early in the

2008 season, when Honda was in F1 with its

own works team. While Red Bull Racing and

Toro Rosso share the same owner and many

anti lag system. The regulations force all current
power units to meet this description, but there is
still scope for innovation in the power unit, and
in a fuel flow restricted formula this is mostly
focussed on the combustion chamber.
This work actually started in 2017 when
Honda tried to increase efficiency by raising
the compression ratio and running a leaner
mixture. To do this it had to change a major
element of the design, and this had unintended
consequences. All of the previous Honda power
units mounted the compressor at the front end
of the block but entirely between the cylinder
heads. It sat on a common shaft with the MGU-H
and the turbine mounted at the rear of the
block. To increase the compression ratio Honda
felt that it needed to increase the size of the
turbine, so on the RA617H it did exactly that,
which had the additional benefit of allowing
the MGU-H and turbine to be lowered, which
resulted in a significant lowering of the centre
of gravity. It also freed up some space for the
variable inlet system to take a slightly more
optimal shape, improving performance.
However, this relocation of the compressor
meant that an irregular shaped oil tank had to
be used and this resulted in reliability issues for
the unit throughout 2017. Honda solved these
problems, but it was too late for McLaren, which
opted to part ways with the Japanese company
and use Renault power instead.

Chamber made
Late in 2017 Honda introduced a pre-chamber
ignition system to the RA617H to prepare for
the 2018 season. The power unit development
continued iteratively from that point throughout
the 2018 season and on into 2019 and the new
RA619H power unit. ‘The name of the power unit
is new but we have kept the same concept, but
have developed it to improve both performance
and reliability, that was the main target and
goal, improving durability and performance,’
says Toyoharu Tanabe, technical director Honda
F1. ‘It is hard to put an exact percentage number
on how much has changed. While we have not
made any big changes we have made many
tiny steps right across the unit. So yes you
could say that most of the design has carried
over from the RA618H, the block and head
castings are really the same. In terms of the
weight of the unit it is the same too, but the
weight has been made differently, so we
have added weight in some areas to improve
reliability, but in other areas we have saved
weight, so adding in some areas losing in others.’
Visually, however, it is clear to see that the
plenum is an area that has been modified for
2019, like the RA617H (and RA618H) it is split
into two independent sides, one for each bank

of the engine but the shape has changed. This

is thought to be due to a new variable inlet

system, but Honda will not confirm this. ‘That

part of the unit has been improved a fair bit,

the execution is quite different but the overall

concept is pretty much the same,’ Tanabe says.

‘The shape is a bit different, but its not a drastic

change. I should say that in terms of improving

the performance we did not just focus on

combustion, we also looked at other areas of

the unit, however it is fair to say that the most

The work started in 2017 when Honda tried to increase efficiency

by raising the compression ratio and running a leaner mixture

FORMULA 1 – HONDA RA619H

The compressor

remains at the front

of the block – the oil

system issues have

now been resolved

The plenum shape has changed from how it was on the 2018 power unit. This is possibly due to a new variable inlet system

‘While we have not made any big changes we

have made many tiny steps right across the unit’