The
JC Cosmo engine. Note Inlet manifold
Series
6 motor
There are also a few other differences. The Cosmo engine retains the Series 4 / 5 style crank trigger assembly, where the Series 6 runs an actual crank-trigger on the crank. The Cosmo engine thus makes an easier engine to do a conversion with. The Series 6 has ever so slightly better flowing port runners in the manifold than the Cosmo engine , with the Cosmo motor having around 5mm bigger port tunnels in the end-plates (roughly the same as 20B), but both are larger than the earlier 13B Turbo engines. They run an earlier exhaust port opening and closing times , and longer intake duration. From memory , the Series 6 is available in manual and automatic gearbox form , and the Cosmo in Automatic Only. You can also identify a Cosmo or Series 6 motor by looking at the rear end-plate. They have the inspection cover located to the gearbox instead of being on the plate . which helps solve the cracking problem in the older Series 4 and 5 motors.
Inspection
cover in bellhousing , not rear plate
Modifications
Standard
power from these engines is around the 140KW at the wheels , but this can
be lifted to around 220KW with just a little work.
Now
, what to do with your engine. If rebuilding it and you intend porting
it , only match up the ports as best you can , and maybe lift the inlet
around 3mm. For the exhaust port look at raising the port about 1mm and
lowering 2mm to give a little more top-end without loosing any bottom-end.
The engines run a very broad power spread as is , and require very little
work. These port mods add a little more top-end power , but they do not
loose any bottom-end that you would notice. You can go a little bigger
if you like but you will start to notice a lack of bottom-end.
If
you intend to run a large amount of boost , you should do the 3mm apex
seal conversion , or at least look at some of the tougher 2mm seals that
are available. Stock seals are meant for stock engines.
A
better intercooler will help when you up the boost too. You can leave the
standard air filter assembly alone if you have a Series 6 RX-7 as tests
have shown that there is no gains to be had over replacing it with a non-OEM
product until you have made substantial power gains. If you have your engine
screaming though , you should then start looking for something bigger.
I personally prefer foam filters over the cotton gauze types.
Look
at getting around a 3" exhaust or larger if you can fit it and still keep
the noise level within your areas requirements.
The
standard injectors on an unmodified motor will handle around 16psi up until
redline before hitting 100% duty. the more you modify the engine
eith the lower you can rev it, or the less boost you will be able to run.
A common upgrade is to replace the secondary injectors with 1600cc units.
These will require an aftermaket ECU to control them, and will supply more
than enough fuel for the motor.
Turbo
Pick
up those twin turbos in your hands , take a good look at them , then chuck
them in the nearest bin... or better yet , sell 'em to some poor
sucker. The best way with any rotary turbo engine to get power over standard
is to replce the turbos with a large single turbo. For the higher flowing
Series 6 and Cosmo engines you should look for something along these lines.
T04-S with a P or Q trim turbine wheel and 1.0 to 1.32 housing , with a
60-1 to a T66 compressor in a 0.70 4"snout cover, or sizes
there-abouts.Different makes of turbos have different wheels part numbers.
I am familiar with Turbonetics sizing so all sizes are listed as per their
catalog. A wastegate around the 42mm size will also be required, as will
a custom exhaust manifold. Doing this sort of turbo will be the biggest
gain of power you will have ever felt. Get to around 4000 rpm and hang
on ! This spec turbo running around 12psi should give a bit over
220KW to the wheels , or around 420HP at the flywheel, and if tuned well
will not compromise reliability and be still very streetable.
Engine
Management
Have
a read of the Series 4 / 5 section. But there are some things that need
to be changed. The Series 6 engine runs larger 850cc / min secondary injectors
, and so requires different engine mapping. Also the ignition system is
not fired with the "toggle" arrangement that the earlier models used. Other
than those differences the general setup is pretty close. I will try to
get a MAP on here for these engines. If you need one just leave me an email.
Also it is still possible with an E6K to control the twin turbo system,
the idle speed control, air conditioner, and any other accessories with
the appropriate outputs configured correctly.
Haltech E6K base
map for Series 6 (1992-) Mazda RX7 - DOWNLOAD