Yet another 12AT question
 

Alright I am missing something in the translation here... Is the 12AT fuel injected, or is it utilizing a carb and blow-through box? I feel stupid for asking, but I keep reading conflicting info.

Also, any links to sites dedicated to the 12AT engine would be great. Found plenty of pics of nice cars that have them, but no real info on them. Just fun homework for me. No motor swaps planned.:D

Thanks in advance,
James

Turbocharged and fuel-injected 12A (Japanese models only, produced 1983-1985)

The TURBOCHARGED and fuel-injected 12A has been confined to the Japanese market, powering the first Cosmo and Luce cars starting in late 1982 and (in it's uprated version) the P132 RX7 from September 1983 through to the end of it's model life.

The 12A Turbo was the first production turbocharged and electronically fuel injected rotary engine.

In it's turbo guise the 12A reverted to four side intake ports.
Each bank has one injector, located in the intake port near the port opening in the trochoid chamber.
Because of this location, which is a cross between manifold and direct-injection methods, Mazda engineers call the fuel injection "semi-direct injection".
The injector is actuated by electrical current and satisfactorily meets the rotary's widely varying fuel demands, from a 600-rpm idle to a full 7000-rpm operation.

Air and fuel mixing is promoted at lower speeds by an air bleed to the injector nozzle receptacle, at higher rpm by a mixing plate socket, an open-sided plastic tube with twin perforated plates. The plates splash and squeeze injected fuel, aiding mixture atomisation.

The fuel injection control unit is an analogue type made by Nippon Denso; it works in conjunction with a Mitsubishi Electric digital emission control computer.
Fuel is injected once per intake stroke, simultaneously in both chambers. As there is a 180-degree difference in the two rotors' working phases, one chamber is injected at the beginning of the intake stroke (or more precisely "travel" in the rotary), whereas the one in the other chamber receives fuel when almost two-thirds of that rotor's intake travel are covered.
As the rotary has an "internal" intake ports (each chamber takes in fuel and air on one side of the trochoid-housing and travels to the other side, where combustion occurs) chamber filling and mixture strength become uniform between the two banks, despite the staggered injection timing.

Primary intake-port timing is unchanged from the carburetted 6PI engine: opening at 58degrees ATDC and closes at 40degrees ABDC.
Opening of the secondary intake port is advanced to 32degrees ATDC; closing remains at 40 degrees ABDC.
The single peripheral exhaust port opens at 75degrees BBDC and closes at 48degrees ATDC.

Of interest in the air-only secondary intake port and manifold are dual throttle valves.
A second butterfly is located upstream in the manifold; it opens slightly later than the lower one.
The dual-valve arrangement prevents sudden air-pressure shocks and, together with the semi-direct injection system, allows a smaller plenum chamber.

The 12A Turbo was originally boosted by a Hitachi HT18-BM turbocharger with a 62mm diameter, 11-blade turbine and a 63mm 12-blade compressor supplying a relatively modest maximum boost of 320mm Hg (6.2 psi); Typical for a Japanese Turbo piston engine is about 400mm Hg (7.75 psi).
Conversely, the compression ratio does not need to be lowered as much as that of a piston engine: only to 8.5:1 from the naturally aspirated 12A's 9.4:1

The 1982 12A turbo produced 160 BHP JIS at 6000 rpm, and a maximum torque of 224 Nm (165 lb-ft) at 4000 rpm; 15-20% should be deducted to get the approximate SAE net values.

Later, the engine was given a new turbocharger, Hitachi's HT18S-BM, with a smaller 57mm turbine and a 56mm compressor, it was dubbed an "Impact Turbocharger" by Mazda engineers because it fully exploited the rotary's forceful exhaust-gas impact with it's new turbine blade shape. The new turbo added 5 more horsepower to the engine's output, as well as improving low-end torque characteristics and minimising turbo lag.

The 12A turbo also has a knock-prevention system. Mazda engineers found in developing the engine that knocking would only occur under certain operating conditions: in a 2500-3750 rpm zone when intake temperature exceeds 85 degrees celcius.
The system, comprising of ignition-pulse, intake-temperature and boost sensors, detects this knock-prone zone and feeds a signal to the emission-control and fuel-injection computers, which in turn call for ignition retard and more fuel (in the latest 13B turbo a more usual piezometric knock sensor is used).
Ignition is basically unchanged from that of the 6PI engine, which now employs semi-surface discharge sparkplugs.

As the turbo rotary's performance and consequently the thermal loads have been considerably increased (for the latter some 30%), lubrication of the trochoid sliding surface and turbocharger has become more critical.
A new trochoidal surface treatment, called MCP (micro-channel porous plating) is employed in the turbo rotary.
It is a development of the pinpoint-porous chrome plating of the normal 12A; the pinpoint holes are interconnected by miniscule channels.
Also, in contrast to the carburetted 12A's oil mixing in the carburettor for seal lubrication, the turbo rotary has separate oil injection; per chamber, one nozzle into the primary manifold and another directly into the trochoidal chamber, both fed by a metering pump.
The turbocharger is also amply lubricated, thanks to the rotary's already adequate lubricating capacity (the rotors are oil-cooled too).

The 12A turbo engine (with all manifolds, turbo, fan, alternator, power steering and air-conditioning pumps) is 786mm long, 548mm wide and 638mm tall (30.9 x 21.6 x 25.1 inches) and weighs 162 kg (356 lb).

Performance applications of the 12A turbo:
The first of these started to arrive in Australia in the late 80s (88-89) at a fairly high cost of $Aus 3500, dropping to a low of about $Aus 800 in 1994.
Although many thousands of these engines were made from late 1982 to 1985, these engines are now (March 2001) hard to find at importers. If they are available expect to pay about $Aus 1200-1500.

These engines quite literally bolt straight into an early RX7. A stock non-turbo RX7 5 speed gearbox would probably be OK with a standard engine, but a slightly stronger gearbox was used with the 12A turbo motor. These gearboxes also bolt straight in.
Other cars which accept these engines without too much modification are RX2,3,4,5.
R100 will fit but I think it is tight/requires some further modifications such as relocation of the turbo.
Realistically an RX4 or RX5 are too heavy for even a turbo 12A if you want some decent performance.

The stock power is around 160BHP (depending on what measurement units (PS/JIS/SAE) are used ).
As the engine is not intercooled in stock form, the addition of one will gain extra power even with the stock boost (perhaps 180-190hp?).
Evidently a stock engine with stock turbo and injectors with an intercooler and increased boost (about 12PSI is the limit) is reliably capable of around 230-240hp.
I have heard that the upper limit is about 280-300hp, but at this level you would probably go for a 13B turbo.

12A turbo engines seem to run successfully on virtually any injection computer around, so unless you have a complete wiring loom, airflow meter and computer it's probably going to be easier to use an aftermarket computer. Besides, the factory trapdoor airflow meter these engines used belong in the stone age, and are easily damaged by backfires. It seems the standard distributor based electronic ignition works acceptably.

Perhaps the one thing to watch when fitting any turbo engine is that the oil and water temperatures are kept down.

Felix.... I may just leave my wife for you...

Thanks for the excellent info!! You da man!

Later,
James

I have now been informed. NEXT!

Mazda UK produced a limited edition turbocharged 1st gen also

I think it was done in conjunction with TWR and the Elford's Mazda dealership in bournemouth

These cars were known in the UK as "Elford Turbo's" and use a Garret Turbocharger and and HIF SU carb.

I'm not to sure about the details but i belive it was a bolt on kit that was fitted to the 12A in the UK and rebadged for sale as a limited edition ... quite a common thing to do over here

... Just thought you may be interested

P.S all of this off the top of my head so some details may be incorrect :D

I remember we had a conversation about this conversions a while back. I beleive Paul Fitzwayne had all the details :)

https://www.rx7club.com/forum/showth...5&pagenumber=2

P.S the car featured is not an elford turbo but a TWR one + as incorrectly stated in this post TWR doesn't stand for Tom Wilkinson Racing but Tom Walkinshaw Racing as in the guy who now owns the Arrows formula one team.

also as far as I can find out the elford turbo's never came with fuel injection ... just SU carbs

Elfords had a choice of dual SU's or a single Holley 4-barrel.

At least, according to my info :)

Mazda UK did not produce a turbocharged RX7. They agreed that a conversion produced by Elford's did not cancel their Warranty. The version was a complete package.

Tom Walkinshaw though TWR Mazda Motorsport offered various performance parts including a turbo kit based on the SU carb, and as Peejay said a upgraded Holley to replace the Nikki.

Both versions retained standard compression rotors. and NA fuel intakes.

Mazda only produced the 12AT engined RX-7 for sale in Japan, all FI not NA. Before the 13BT became readily available, several owners imported used 12AT engines/transmissions from other models. However, the real turbo model had many features exclusively found on the USA GSL-SE.

Yep, the GSL-SE was the US version of the 12AT.

Another thing mazda got right... bigger engines are more in the american idiom than turbo ones :) More idiot-proof, and this country seems to be mostly populated with idiots. (Which explains why when you get a coffee, the cup says two times each in four different languages (English, French, Spanish, and German) that you better be careful, coffee is hot and can burn you.

That crap is because americans are SUE happy... Like the lady at mcdonalds that burnt her old coochie, sued them for like a lot of $$$'s and won. Im like god damn common sense will tell you that it will burn your ass!

Now with that said: I wanna know if I hold a lighter under my hand will it burn me? Shouldnt they put labels on them saying lighters could start forest fires? Stupid stupid!

Paul Im sorry i got your name wrong there :) Dont see you around much so I couldnt remember :D

No problem Mike many get my name wrong, except the taxman!

Been working in the outback for the past few weeks with poor communication. Plenty of wildlife so used a 4 wheel drive with bullbar. Coming back home I used the RX-7 and hit a large kangaroo at 70mph. The impact threw the roo across the headlight taking it off and blew the fuses. It was five in the morning and I had to drive for two hours on the light of a tourch out the window. There was no other damage which shows how tough the front is. It least it gives me the chance to fit a modified carb and manifold I got from REVHED.

what is the deal with this felix guy.
he seams to know everything.

That's because he if FELIX WANKEL, the Inventor and Creator of the Rotary Engine. He sold his Patent to NSU back in the 60's, and he didn't get much money for it.

So, to make up for it, he prowls around on the RX-7 Forum where he get to be treated like a God by Newbies.

:D

http://thelittlebaby.dhs.org/kenny/s...nfo[1].gif

Dude, Not to take any credit from Anthony (Felix), but there is such a thing as Cut and Paste.

Hell yeah, I can't type THAT damn much.