Saabscene Saab Forum - Saab Technical Information Resource banner
1 - 12 of 12 Posts

·
Registered
Joined
·
54 Posts
Discussion Starter · #1 ·
i just got a 86 9000 turbo. with a straight through exhaust, whats the most i can safly turn up the boost? when will it cut timming? and what is the exact turbo i have on it? i know it dosent look as big as a t3... i'm in USA, did we get smaller turbos the the uk?

thanks guys
 

·
Registered
Joined
·
1,219 Posts
you have a non-watercooled T3 turbo (45 trim i think) the timing isn't computer controlled, it is manually set (using the dizzy) and as for turning the boost up, i would rather modify or buy a modified APC unit. I modified mine, (i have the '87 9k T with the watercooled T3) I also modified the advance/retard capsule, or to be more correct, i modified the retard stop on it, so that under boost it will retard the timing more than stock. I modified the APC so that it runs 15 PSI all the way to rev limiter, with no boost taper. i also wired in an LED to flash when the APC detects knock, and a potentiometer to give me 5-15psi manual control.
 

·
Registered
Joined
·
54 Posts
Discussion Starter · #4 ·
whats the stock boost set at amd what is the AR on the exhaust housing? So all the timing controll is done without a computer? Does the knock sensor just adv. till it pings and then back it off? Is there a boost cut that shuts off fuel or spark? Are the pistons forged?

Thanks.
 

·
Registered
Joined
·
3,618 Posts
For a B202, it will be 0.85bar +/- 0.05 bar peak for a non-cat (from factory) car or 0.75bar +/- 0.05 bar peak for a car with a cat.

According to Haynes.

Pressure switch cut-in is about 1.1bar on a stock car.
 

·
Registered
Joined
·
8,216 Posts
The knock sensor is not connected to the ignition system at all on your car. It is a simple conventional system, with only a hall-effect pickup and ignition amplifier as a concession to modern electronics (even my 8V, single-carb, 100hp 90 has that).

Ignition timing is controlled purely by mechanical means in the usual way, using a combination of centrifugal and vacuum/boost advance in the distributor. The knock sensor is only used by the boost control. This "aims" for a certain boost/RPM curve but will reduce boost if it detects knock. It also considers transient behaviour but that's the gist of it.

Later 9000s with DI/APC (direct ignition and digital boost control) used the knock sensor to control ignition timing as well as boost pressure. After that, 9000s with Trionic control sensed knock using ionisation current across the plug gaps.

Some 9000 non-turbos were fitted with EZK ignition, which used a knock sensor in the way you describe.
 

·
Registered
Joined
·
1,219 Posts
Ah... BillJ.. the 9000 (actually all non-DI 16v enines) had no centrifugal advance... just vac-advance and boost retard.

Adrian W - now why does that make you grin?
 

·
Registered
Joined
·
8,216 Posts
I find that impossible to believe, Grentarc. Unless flame-front propagation speed rose in direct proportion to engine speed (and I'm pretty sure it doesn't), you would need to advance the ignition timing with increasing engine speed.

I'll have to check it out.
 

·
Registered
Joined
·
1,219 Posts
all the 8v engines need the timing adjusted at 2000rpm because of the centrifugal advance, whereas the 16v is done at idle, and once you set it, if you raise the revs (with vac hose disconnected) it does not advance the timing (checked this out myself with timing light) also with centrifugal advance, the rotor is loose in the distributor, where on my engine, it is solid. the timing is set to 16° BTDC at idle, so it really cant afford to be advanced with rpm.


i am not looking at specs, only what i have found on my engine....
 

·
Registered
Joined
·
8,216 Posts
What I've found on a '93 900S (LPT) is that the ignition timing, once set to 16 degrees, advances when the engine speed is raised. It would have to be so since otherwise the fuel would still be burning when the exhaust valves open at higher RPM, leading to loss of power, burnt exhaust valves and high exhaust gas temperatures. The whole idea of advancing the ignition as engine speed increases is that the speed of the flame front through the charge is roughly constant so it needs to be started earlier at higher RPM to keep combustion synchronised with the power stroke.

The rotor arm on that car doesn't feel significantly different from that on my 8-valve 90. The fact that the 16V engines are timed at idle doesn't necessarily mean they don't have centrifugal advance. They're just timed at a different point on the advance curve.
 

·
Registered
Joined
·
1,219 Posts
well.. mine doesnt advance with rpm (as i said, i checked with timing light) and i dont want it to, as the detonation would be horrible then, as it is a PITA as it is, with me having to make it retard more under boost.

[edit] when i bought the car, it had a check valve between the advance capsule, so that it wouldnt advance the timing with vac, and would retard under boost only. don't know why you would want that setup
 
1 - 12 of 12 Posts
Top