Hello Paul,

     My name is David, I am from Spain and I'm doing a master's
degree  about   motorsports in Epsilon Euskadi's facilities (METCA,
 that is  managed by   Sergio   Rinland).

     I have been reading your website and i find very interesting
the Turbo     Compounding in order to improve the engine performance
and  efficiency,   that's why i would like to do the master's
project  about it.

     Sergio Rinland suggested me to get in contact with you in order
  to find an   automotive company which is developing it, so i could
  help them in that   developing work.

     I have seen that the Turbo Compounding could be applied as it is
  in the   examples you show in your website, to transmit the
turbines  torque to the   crankshaft of the engine, but also, i
think it could  be interesting to use   it as a "battery charger"
for a hybrid car.

     I hope you can help me, because i think this is a very
  interesting project   that could help the automotive industry in
the  nearest future.

     I look forward to hearing from you,

     Kind Regards
     David Garcia

  Yes I know Sergio Rinland. I met him at the World Motorsport
  Symposium in Oxford.  It can be used as a battery charger but
  perhaps that is not the best way to use it.  Each time one converts
  energy from one form to another there are some losses.  These
losses  rapidly multiply.  If a generator is 90% efficient and a
motor is  90% the over all efficiency becomes only 81%. Ultimately a
car  requires mechanical energy to move.

  The first thing one
  must do with a turbo compound is to convert the momentum and heat
  energy in the exhaust to mechanical energy.  It is best to use that
  mechanical energy directly to move the car for the reasons stated
  above.  Turbo compound truck engines are rapidly becoming the norm.
  Turbo compound ship engines frequently utilize the waste energy in
  the exhaust to generate electricity for use on the ship.  Large gas
  turbine power plants use the exhaust energy to generate steam for
  steam turbines which increases the overall plant efficiency to over
  50%.  These are called "combined cycle" or "bottoming cycle" power
plants.

  A typical car engine is less than 35% so herein lies
  the opportunity to drastically reduce the world wide consumption
of hydro  carbon fuels.  The piston car engine loses 20% of the
energy in the exhaust  to aerodynamic and heating losses on the
exhaust valve.  Of course  over 50% of the energy in the fuel burned
in the IC is lost to the  exhaust.  The Wankel rotary by comparison
is "piston ported" so to  speak so these exhaust valve loses are
drastically reduced.  It has  no exhaust valves.  It is true the
current Wankel rotary design is 5  to 10% less efficient than the
current piston engine but it still  remains the best choice for high
power to weight ratio turbo  compound engine used to power both
airplanes and cars.

    The turbo compound Wankel rotary would become the most efficient
internal  combustion engine suitable for vehicles.  Engine weight is
a key  factor in the overall empty weight of both airplanes and
cars.  A  lighter vehicle is a more efficient vehicle.

  The aircraft and recreational boat application of the turbo
compound  rotary is trivial from an engineering point of view while
the real  challenge is the wide dynamic range of the passenger
vehicle engine.

  Paul Lamar

    Hello Paul;

    So, as I was wondering, having in account the losses of
converting  the  mechanical energy to electrical energy it's a
better idea to  use the  mechanical energy of the turbine directly.

    You think it is a good idea to apply this technology to
passenger vehicle    engines. Do you know if any automotive company
developing it so I  could  get in contact with them and try to
collaborate in that  developing process?

    In case I could not get in contact with any company I would like
  to develop  it on my own, but I don't know if you could help me
with  my doubts during  the developing process. I don't have too
much  experience on this yet.

    Thank you very much,

    Kind regards
    David Garcia

    Using the mechanical energy directly means one does not have to carry
    the extra weight of a battery, generator and electric motor.
Also there    is a world wide limited supply of lithium for advanced
batteries.

    The best approach to the problem is use two engines. One small
one    for cruise on the autobahn and a larger one for acceleration and
    hill climbing. As you can see from this chart the optimized BSFC
    island of a large engine is too far, in terms of throttle opening
    (manifold pressure) and RPM, from constant speed flat road
    load requirements. This has been mitigated somewhat in modern
cars    by using a lower reduction ratio (lower cruise RPM) in top gear.
    Most of the improvement in MPG has come from this practice
despite    large weight increases due to government crash requirements.

    This dual engine idea can and has been implemented by partially shutting
    down a few cylinders in multi cyclinder piston engines. One good
   way of  doing this is allow the exhaust or intake valve to remain
  open or closed  while that  cylinder is not needed. Since the
piston  is still going up and down there  are still pumping and friction
  losses from the shut down cylinders.

    The Wankel on the other hand is unique in the fact the straight eccentric
    shaft can be made concentric with a smaller interior shaft. That
would    allow the larger engine to be completely shut down.

    The Wankel also has the turbo compound advantage of no exhaust
  valve to  reduce  the energy in the exhaust stream so it is ideal
  for the turbo compound  configuration. NASA studied the Wankel
turbo  compound engine in this  technical paper:

    http://www.rotaryeng.net/NASA-Paper-turbo-compound-rotary.pdf

    NASA concluded it was possible to recover 80 free HP from a
    Mazda sized rotary engine with minimal increase in fuel burn.
    Unfortunately NASA ran out of money before this could
    be tested in hardware.

    Here is a design that implements this dual Wankel engine
approach.  Small  and large Wankel engines are available off the
shelf to build  a prototype  for testing. The small engine would be
turbo compounded  to lower the  fuel burn for the 95% of the time
the car is in cruise  mode.

    http://www.rotaryeng.net/RX8.
    http://www.rotaryeng.net/RX8-TC-eng3.html

    So far to my knowledge no car company is working on this turbo compound
    idea. Mazda is ideally positioned to do this so you might try
    contacting Mazda.

    I will be glad to help including a trip or two to Spain
    if necessary at my expense.

    Paul Lamar

  Hello Paul,

  As i told you, i put in contact with some people from Mazda and
also  from AER engines, a company that works for Mazda.

  They told me that they can't help me because their projects depend
  on their customers, and nowadays they don't have any about turbo-
  compounding, so i think that i will have to develop this project on
  my own, with your help, of course.

  I have been thinking about how can i start it, and i don't know yet
  how can i structure the process. I have a clear idea, i will use
the  design of an ordinary turbocharger, where i can adapt the
gearbox  and all the things i need for the design.

  I guess that the best engine to adapt the Turbo-Compunding is the
  1.3 liters engine of the RX8, what do you think? in case of using
  this engine, do you know what kind of turbo is the most common used
  in this rotary engine? i will look for information of it and i will
  try to start the 3D design of it.

  when i decide what engine i will use, i will need some information
  about the exhaust gases, such as speed and temperature, so i will
be  able to simulate the turbine runing, obtaining the speed of it.
do  you have that kind of information?, or do you know where i can
find it?

  Thank you for your attention!

  Kind regards,

  David Garcia

  That is like Mazda saying they are not interested in better gas
  mileage :) I think you have a communication problem David.

  Whom did you contact at Mazda?
  Email me your letters David and I will take a look.

  I am not surprised about Advanced Engine Research (AER) in the UK
as  they do only custom turbo charged 2 liter 4 cylinder piston engines
  for Mazda through Dyson racing. They are not that competant as the
  best they have accomplished so far is a 3rd in LMP2 class at Le
mans  in 2009. http://www.aerltd.com/

  IMHO it is a misguided attempt by Mazda to put their stock mediocre
  4 cyl piston engine on the world wide racing scene. Better and much
  larger companies than AER build better racing piston engines and
  spend ten times more money doing it. Renault, Ferrari and Mercedes
  Benz for examples.   IMHO Mazda would be better off putting the
  money into their unique Wankel rotary to improve the efficiency.

  The rotary has put Mazda on the world racing map since the early
  1970's culminating with an over all outright win at Le Mans in
1991.  Not their piston engines with the exception of SCCA Miata
spec.  Sometimes I think Mazda forgets that fact. Without the rotary,
 Mazda  will always be second rate to Toyota, Honda and Korean car
 manufactures that generally do a better overall job of building
 cars. Understandably so because they are ten times larger.

  IMHO Mazda needs to try harder on the rotary.

  Paul Lamar

David,

I was sent a customer satisfaction questionnaire after the Mazda3
purchase. At the bottom they asked if I had any complaints and
suggestions. Complaint was fuel economy. Too much gear 4.105 final.
My suggestion was to look at Paul's turbo compound article on his
web site. Naturally I have heard nothing back.

Their fuel economy improvement seems based on the Skyactiv
technology without turbo charging. This may come from the ignorance
and stupidity of the buying public that does not know what is
required with a turbocharged engine; idling at start and before shut
down to let the turbo cool and the turbine to slow down.

Even on a boing boing engine you would pick up fuel economy with a turbo
compound and change the gearing to 3.5:1 instead of the above
mentioned gear.

Dale Davies

Mazda may be the only company in the world that does not have the
rear axle ratio optimized for MPG :) The RX8 ratio is too high as
well. However in the RX8 they also  need a fast shifting automatic
manual transmission to go along with it as it as the rotary has near
zero torque at 2000 RPM:)

Paul Lamar

Yup! ZOOM ZOOM.
A taller axle and even just a power recovery turbine would help. Taller gear =
wider throttle opening at lower RPM. Lost zip from gear picked up by turbine
torque.

Dale Davies