SAAB Trionic, excuse me but...

[C M Smith <cmsmith@domain.elided>]

This was not the first for SAAB. Initially, Bosch/Volvo/SAAB collaborated 
on the first Lambda system on the Bosch K-Jetronic system. It was a very 
clever design and is the foundation for all modern emissions related engine 
management systems. The key insight was the feedback loop. All the 
engineers needed was some way of automatically sensing the mixture and 
adjusting it on a  continuous basis. The O2 sensor was the key element, 
then a simple "computer" could adjust the mixture essentially in real time 
( a very small time delay) by adjusting the fuel pressure at the fuel 
distributor. 1975 was the first year of this system I believe.

This feedback concept was later adapted by SAAB to control boost in their 
turbo cars. Performance went from 145 hp to 175 hp with this simple 
computer. The feedback sensor in this case was a knock sensor on the 
cylinder head. SAAB developed a boost control solenoid that bled boost 
pressure away from the wastegate control until the knock sensor signalled 
detonation. Then the computer signalled the BPC to allow the wastegate to 
"see" the actual boost pressure and dump boost. The feedback aspect allowed 
this to be done continuously and effectively in real time. the result was 
an overboosted engine that never detonated. This system was released in the 
1982 model year I think.

Finally, SAAB integrated ignition timing into their engine management 
system, together with the boost pressure control and mixture control. Hence 
the Trionic name for the three variables controlled by one ECU. The 
brilliance of Trionic relies upon the circuitry that eliminates the 
separate knock sensor and replaces it with an ion sensor inside the 
combustion chamber which detects the chemical nature of the post combustion 
gases in the combustion chamber and adjusts boost, timing, and mixture to 
reflect actual combustion events. The O2 sensor is a minor player in this 
system. Timing is non linear as for Motronic.

Technically, SAAB's system is capable of producing exhaust gas cleaner than 
the air in most cities in the world. It is an ULEV I believe, and produces 
250 hp from 2.3 liters in the current 0 5 Aero. Squeaky clean. 
Modifications to this system have produced well over 300 hp in fully 
streetable (though perhaps a bit less clean?) form.

SAAB's claims are  not just for the press, they actually do it. In one 
fairly dramatic demonstration the exhaust from a two stroke SAAB engine is 
fed into the intake of a new 9 5 and the exhaust from the 9 5 is still clean.

Love 'em, and if GM can allow Alfa to do what they allow SAAB to do, we are 
in for some really good cars if Alfa ever returns.






Michael Smith
White 1991 164L
Original owner
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