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Sorry for the common crossover question. I can't remember what the rule on using DI's is at the moment and I can't find what I need from search.

A friend has a spare DI leftover from when he sold his Viggen. It is a black DI. Can I use it on my 1994 Aero 5MT?
 

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You will see varying opinions on this. My experience is that you absolutely can use a black "newer" DI cassette. I drove a 9000 with a black DI fo9r nearly a month and it ran fine. I am told that you give up some knock detection. My approach is to keep the one I have as a spare.
 

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From what I understand it's a "Yes, yes you can." B235/234's are in a sense, the same engine. Minor design changes here and there. The only reason you wouldn't want to is from what I've heard, and I can't verify this, the older Black DI's "Spark" hotter, thus giving a bit better read and detection.
 

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NO! The T5 computer WILL NOT get proper information from the black DI when the engine is knocking, and will not retard timing or cut boost when knock occurs! The red T5 cartridges are acceptable for brief testing use in T7 cars, the black T7 cartridges ABSOLUTELY CAN NOT be used in T5 cars! Either is apparently OK in the early DI/APC 9000s (up to '92). I would only use a black DI in a T5 car if I were stranded on the side of the road and it was the only spare I could get.

As for spark, the red DIs spark is more intense but less duration--black is less intense but more duration.

Again, the format from the knock signal is totally incompatible with your T5 ECU. Anyone who tells you otherwise is dead wrong. Do it at the risk of your engine. If you absolutely insist, put in only the highest octane fuel you can get from a big-brand station, and go EASY on the boost! You may think you can/have heard engine knock that could potentially destroy your engine, but the proper DI can detect this FAR BETTER than you can! DON'T RISK IT.

Here are some quotes from one of the engineers involved in designing the DI system for Saab:

Hi !

RED cassette has got a DC spark.
We have two different RED cassettes:
----------
Then, BLACK cassettes:
BLACK cassettes has got an AC spark, and thus a longer spark duration.

NOTE:
Cars with DI or DI/APC (MY 90-92) can use the BLACK cassette as "Dr Boost's fix".
The longer spark duration will make the engine to run smoother.
Do NOT use BLACK cassette on a T5 car.
Hi !
For a "simple test", you can use a BLACK cassette in a T5 vehicle, or if you want the other way around.
However, the "signal interface" are slightly different, or in ither words, the combustion and knock signals are different.
that's why I don't want you to do this, unless it's a simple test.
Just to check if the engine starts or not. I really hope I'm making myself clear enough.....
Hi !
As some of you know I work at Saab.

All DI cassettes are "capacitive discharge".
Short description of RED cassette:

The DI Cassette is feed with B+(12V), the B+ is then converted to 400 VDC, inside the DI C. There are four individual ignition coils.
Between the 400 V capacitor and each coil there is one thyristor per coil.
When the ECM triggers the thyristor, energy that has been stored in the capacitor will be dumped into the primary (winding) side of the ignition coil.
As a result there will be a hi voltage across the secondary side.
The duration of the "spark" is quite short, because the use of a thyristor. (DC spark)

BLACK cassette, well more or less the same description, BUT with one important difference: we don't use a thyristor to dump the energy, we use a triac.

The difference between a thyristor and a triac is that the thyristor will only conduct current in one direction, triac in both directions.
And that's why we get a AC spark in the BLACK cassette.
The BLACK cassette's spark duration is approx. three times longer than the RED.

On the New 9-3 SportSedan we do not use capacitive discharge ignition system anymore, we've got an inductive system.
Still one coil per cylinder, and still the ionization concept to analyze the combustion conditions.
The BLACK DI C will work on your MY/91 LH 2.4.1 But do not use the BLACK DI C as a replacement for a RED DI C if the car has got Trionic T5.
 

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You will see varying opinions on this. My experience is that you absolutely can use a black "newer" DI cassette. I drove a 9000 with a black DI fo9r nearly a month and it ran fine. I am told that you give up some knock detection. My approach is to keep the one I have as a spare.
NO! The T5 computer WILL NOT get proper information from the black DI when the engine is knocking, and will not retard timing or cut boost when knock occurs! The red T5 cartridges are acceptable for brief testing use in T7 cars, the black T7 cartridges ABSOLUTELY CAN NOT be used in T5 cars! Either is apparently OK in the early DI/APC 9000s (up to '92). I would only use a black DI in a T5 car if I were stranded on the side of the road and it was the only spare I could get.

As for spark, the red DIs spark is more intense but less duration--black is less intense but more duration.

Again, the format from the knock signal is totally incompatible with your T5 ECU. Anyone who tells you otherwise is dead wrong. Do it at the risk of your engine. If you absolutely insist, put in only the highest octane fuel you can get from a big-brand station, and go EASY on the boost! You may think you can/have heard engine knock that could potentially destroy your engine, but the proper DI can detect this FAR BETTER than you can! DON'T RISK IT.
Jeff knows what he's talking about. I was mis-led by my former indie Saab mech that the black DIC runs fine on my T5 B234 ('93 9000CSE, now Jeff's ride). It ran, and I used it for like 4 years (!) until Jeff told me not to. Swapped back a spare red DIC someone else had and wham-o, my car was instantly better in all ways.

So moral of story ..... black cassette will work but will compromise your car's performance and risk knocking your engine block to the point of failure. Use at your own risk !
 

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Hard to believe how many times this question is asked.

Thanks to Jeff for the full answer, and for the quotes.;ol;

This should be stickied on this forum and the NG900 forum.

Funny how people ignore this.
 

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Let's ban them all !!! :lol::eek:;)
;ol;

Yes, :D lets go back to points, feeler gauges,dwell meters and timing lights, any old plugs will do, simple as stuff.:lol:
 

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T5 can NOT be used on T7, T7 can be used on T5 BASED ON MY EXPERIENCE (although many contest otherwise on this subject). Maybe there are some consequences, but whatever they are, they have done some serious good for me;ol;, as far as boost control and such. I shall eat my shorts if switching back to my T7 black DIC has a negative effect on my car.;)
 

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Discussion Starter #10
Again, the format from the knock signal is totally incompatible with your T5 ECU. Anyone who tells you otherwise is dead wrong. Do it at the risk of your engine.
But how do you really feel? :)

Thank you for the informative response Jeff.


Yes, This should be sticked. I wasn't coming up with the information I sought through a simple search.
 

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I work at an indy, and every single T5 car that comes in here that needs a new DI gets a Black one. Never EVER caused a problem. However, we had one 9-5 come in with a red DIC and it melted the DI plug, so our rul e of thumb is:
Black DI's for all 4cyl Saabs
Red DI's for any T5.

I run a Red one on my 9K but I would run a Black DI in a heartbeat if my Red one failed.
 
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