I've noticed that after boosting for several minutes, APC cuts me back to base boost. I assume if it was a fuel quality issue, it would have cut back much sooner. It seems like if I drive hard for a while the car gets sort of tired and doesn't want to produce full boost anymore. If I turn the engine off and back on, I get full boost again for a while. Does the computer keep track of how long the car has been boosting?
Why would it go back to full boost after turning the engine off and back on again? I didn't think heat soak would be an issue at 80+ mph. Does T5 have any time-based boost limiting parameters?
Why would it go back to full boost after turning the engine off and back on again? I didn't think heat soak would be an issue at 80+ mph. Does T5 have any time-based boost limiting parameters?
After a period of hard acceleration, the motor, turbo, transmission, etc get hot....
If you beat the crap out of the car for a few miles, you may need to drive for several miles at a relaxed pace in order to get the full boost back. This is set this way as to not destroy the motor.
So what exactly tells the motor to back off? A parameter like intake charge temperature or coolant temperature? Or does it clock how much time the motor spends under load?
No.
It should be able to run at boost for days (see the 100,000 Mile Test in 1986).
What you describe sounds like an ECU going into Default; it resets when you power up.
That can happen when the Boost Control, Fuel Delivery, and Ignition Systems can't communicate with each other. I bet a Tech II could show you what's happening.
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If you beat the crap out of the car for a few miles, you may need to drive for several miles at a relaxed pace in order to get the full boost back. This is set this way as to not destroy the motor.
I experience the same cut-off after a few miles of full boost. But by then my automatic speed governor who's in the passenger seat would ask me to pull over to the nearest rest stop so she can go take a pee.
I experience the same cut-off after a few miles of full boost. But by then my automatic speed governor who's in the passenger seat would ask me to pull over to the nearest rest stop so she can go take a pee.
My car will cut back to about halfway between full boost and base boost even if I am just sitting in hot weather in traffic. Annoying when the traffic finally breaks and I have a gutless car
The only boost limiting parameter is the knock sensor. When the APC computer processes continuous knock from one cylinder then the boost is cut back in steps until no knocking is detected. APC cars use a piezo electric sensor on the cylinder block below the cylinder head temperature sensor (between intake pipes 2 and 3. The pressure waves from this sensor are processed and if this matches a detonation wave then the APC triggers the APC solenoid to dump boost. This is a feedback process and continuous.
Consistent knocking back of boost will result if cylinder head or spark plug temperatures are elevated as these are prime contributors to detonation. The intercooler runs at fairly stable temperatures unless speed is low.
This is correct
1) you,ll find that a dodgy spark plug can cause false knock signals - not uncommon - so first thing to try is a fresh set of plugs set accuratly at 1mm gap - disconnect the battery whilst doing this to enable to ECU to re set
2) A dodgy DI can do the same - so look for a swap
note both of the above - you may not notice any missfire or otherwise indication of failure - but if you had a knock indicator fitted - you would see the false signals
3) maybe you have a real knock issue - so the first place i,d look is your fuel delivery - fuel filter - pump - and pressure regulator i.e. are you getting enough fuel during high demand - something as simple as a leaking hose to the pressure reg. would cause this issue
So is there a piezoelectric element on my engine or no?
The base boost only comes as a result of beating on the car for miles. If I'm driving around casually and floor it, I always get full boost. I'm running 87 octane fuel with water injection and the behavior isn't any different than running 93 octane. The tires still break loose in 2nd. Maybe I'll hook up a knock LED and see if I notice anything.
So is there a piezoelectric element on my engine or no?
The base boost only comes as a result of beating on the car for miles. If I'm driving around casually and floor it, I always get full boost. I'm running 87 octane fuel with water injection and the behavior isn't any different than running 93 octane. The tires still break loose in 2nd. Maybe I'll hook up a knock LED and see if I notice anything.
APC cars are not Trionic and have no DI cassette. APC stands for Automatic Performane Control and used a separate ECU and a knock sensor to control boost. Ignition timing was not mapped and was responsive only to mechanical advance and vacuum/pressure timing adjustment. This does not use the spark plugs to detect anything. The last APC cars were 1990 or perhaps 1991, I believe.
Trionic (for Timing, Boost and Fuel Mixture control hence "Tri" and fully electronic control, hence "onic") uses a DI cassette and detects actual combustion conditions by means of low voltage signals across the spark plug gaps which then feeds that info to the integrated engine management ECU controlling all aspects of the engine combustion.
Trionic cars are not sensitive to elevation, air temperature or poor fuel quality (Aero engines with manual gearboxes are not tolerant of 87 or 89 octane but non Aero engines are) as the Trionic system adjusts for all these factors.
They also do not get "tired" but the ECU will respond to extended periods of hard driving by reducing boost, enriching mixture and retarding timing to ensure optimum combustion for any conditions.
Trionic was introduced in 1991 I believe but perhaps those early cars were still APC even though tey had DI cassettes. Certainly all the 2.3 turbos were Trionic.
APC cars are not Trionic and have no DI cassette. APC stands for Automatic Performane Control and used a separate ECU and a knock sensor to control boost. Ignition timing was not mapped and was responsive only to mechanical advance and vacuum/pressure timing adjustment. This does not use the spark plugs to detect anything. The last APC cars were 1990 or perhaps 1991, I believe.
...
Trionic was introduced in 1991 I believe but perhaps those early cars were still APC even though tey had DI cassettes. Certainly all the 2.3 turbos were Trionic.
partially correct, the last apc cars were 89-90 IIRC, BUT then there were the pre-trionic DI/APC cars as well, which detected knock via knock sensor up until 92
Trionic (for Timing, Boost and Fuel Mixture control hence "Tri" and fully electronic control, hence "onic") uses a DI cassette and detects actual combustion conditions by means of low voltage signals across the spark plug gaps which then feeds that info to the integrated engine management ECU controlling all aspects of the engine combustion.
not too sure if this is true with the 93, as it has a "hybrid" version of trionic, which is 5.2, which was a one year only thing before the complete trionic system was realeased in 94.
Trionic cars are not sensitive to elevation, air temperature or poor fuel quality (Aero engines with manual gearboxes are not tolerant of 87 or 89 octane but non Aero engines are) as the Trionic system adjusts for all these factors.
i thought that ALL trionic engines were not tolerant of the lower octane fuels, they would run, but boost and timing would be cut back, due to the lower octane
They also do not get "tired" but the ECU will respond to extended periods of hard driving by reducing boost, enriching mixture and retarding timing to ensure optimum combustion for any conditions.
They do not get "tired" but the ECU will respond to extended periods of hard driving by reducing boost, enriching mixture and retarding timing to ensure optimum combustion for any conditions.
So my original question was, does the ECU cut back boost as a result of elevated intake/coolant temperatures, or does it use time/boost dependent parameter to do this?
I had same problem on my tuned 9000. Came down to be a DI. Try changing/regapping plugs first, and putting some dielectric grease.
Also, ICs get dirty and oily after a while, reducing their efficiency. Therefore you might be due for some cleaning. Basically this could be a combination of things, weak ignition system with an older IC, leading to higher temp, worse spark, knocking and finally boost retardation.
Spark plugs are brand new and properly gapped. I have two DI's to test with and there's no change of behavior between them.
I know that Trionic cuts back after a few hard miles, my question is how it decides to do this.
Superaero, first you said knock was the one and only factor involved in cutting back boost, then in a later post you said:
They also do not get "tired" but the ECU will respond to extended periods of hard driving by reducing boost, enriching mixture and retarding timing to ensure optimum combustion for any conditions.
My question is what causes the ECU to cut back?
1. Knock alone, possibly heat-soak induced.
2. The ECU deciding it needs X seconds of rest after Y seconds of boost (even if no knock is present)
I'm inclined to believe the latter since I get full boost after turning the key off and back on again. Does anyone know for sure if Trionic uses any time-based parameters to control boost?
Trionic uses detonation as the boost limiting factor. Detonation is sensitive to: air pressure, air temperature, fuel mixture, octane rating, ignition timing and combustion chamber conditions such as hot plugs or deposits in the combustion chamber.
There is no time limited feature on any SAAB turbo system.
There are some other manufacturers (Mini for example) that allow a timed overboost situation but SAAB does not do so.
OK, thanks. It must be heat soak then. It still boosts to the end of the red on 87 octane, so there's no knock, at least not initially.
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