Hello Paul,
My name is David, I am from Spain and I'm doing a master's degree
aboutmotorsports in Epsilon Euskadi's facilities (METCA, that is
managed bySergioRinland).

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 anautomotive company which is developing it, so i could
help them in thatdeveloping work.


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

I hope you can help me, because i think this is a very
interesting projectthat 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


G'Day David, why don't you research the Tesla Turbine? I understand it could be direct coupled to the e shaft and use the rotary's extremely energetic exhaust and so act as a muffler. There would be no gearbox involved and so minimal energy loss.
The main problem would be the high temperature exhaust - ? Inconel discs, ?ceramic discs ? cast iron housing.

John Evans