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Discussion Starter #1
Hello

Does anybody know the standard non tweaked setting for a 1990, 900 16v Turbo?

I can not seem to find this information anywhere?

I have an 18 Psi vacuum at idle and i am wondering of this is ok? should it be more or less?

I can boost to 14, 15'ish Psi which i dont do but i have been told i should only be able to boost to 8 psi?

When i bought the car the chap took the APC valve away so it boosted into the Red way into the Red, i found a 1988 APC valve on Ebay and pluged it in and replaced the brass bleed valve, then it started to boost less and at time it cuts the power when i put my foot down to over on the motorway.

Does the APC need to be from the same year of Saab? what should a 1990 Turbo boost too? its the ME 03 turbo i think, not the Garret one.

I would be grateful for any help.

Thank you.
 

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Check base boost first, this should be carried out with the APC solenoid disconnected, should be 5.8 +-0.4 bar. You can set this higher for more performance, some set at 6.0-6.5 bar.

Maximum boost pressure should be 12.3 +-0.7. But again this can be set higher by adjusting the pots in the APC.

Both of the above jobs have been covered many times, so please do a search & you will find all you need in the archives.

BTW the above applies to cars without CAT settings are lower for cars with.
 

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ShadowWorks said:
at time it cuts the power when i put my foot down to over on the motorway.
It sounds like when you removed the bleed valve you connected up the overboost fuel cut out switch again which had been disconnected before. Hitting fuel cut will mean that when you are accelerating fairly hard, when boost pressure reaches a certain point (I think just below 1 bar on a T16) it will suddenly jolt and you will lose all power. If you take your foot off the gas and then re-accelerate, power will resume until you hit that point again. You can recalibrate or bypass the fuel cut out switch fairly easily - lots on this in teh archives on here.

A couple of links that might be useful:

http://www.thesaabsite.com/APCadjustment.htm

http://www.thesaabsite.com/Base Boost adjustment.html
 

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18 PSI of vacuum is not possible! If you mean 18 In HG, then that's perfect (18-21 In HG is the correct range for a healthy engine).
 

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Discussion Starter #7
Hello and thank you all for your post.

I bought an aftermarket gauge a Sunpro it gives me a reading in Psi.

At idel its sitting at 18 Psi vacuum, it was at 16Psi before and i discovered a few air leaks, then i corrected them and the vacumm was more suckky at 18Psi

You right about the fuel cut out, i have no idea if the chap did something to the APC box, i hope not, i really want good MPG from my car, I am not into wearing my tyres out.

The car will boost to 20Psi (end of the gauge)without the soloniod connected? i assume thats not normal?

is a small air leak from the gauge a problem? as in poor MPG? i can hear it wishper when the engine is in boost from behind the dash.
 

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Any air leak afetr the air mass meter will mess up the fuelling. You're allowing unmetered air into the inlet.

I can never remember how much stock boost is on an FPT :roll: (0.8bar?) but the gauge should point to the orange/red border. 20PSI with no supporting mods is asking for trouble, especially as the MBC gives you no protection against knock or pre-ignition.

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Discussion Starter #9
Matthew said:
Any air leak after the air mass meter will mess up the fueling. You're allowing unmetered air into the inlet.

I can never remember how much stock boost is on an FPT :roll: (0.8bar?) but the gauge should point to the orange/red border. 20PSI with no supporting mods is asking for trouble, especially as the MBC gives you no protection against knock or pre-ignition.

I understand and agree with you, i just went to B&Q and found some plastic piping and i will replace the black piping that is prone to splitting.

I only wanted to see what the car can boost too without the APC connected, i dont not ever want to blow my head gasket and i dont drive fast.

Its just 2 days ago i had to over take a slow moving tracker and 4 other cars, i put my car into 3rd and slowly put my foot down and half way the fuel cut in kicked in, its a horrible feeling, i always feel like i have popped something.

But the standard APC gauge never when way over into the red? just 3 mm into i would say, boost was around 8psi i think?

My car been so bad on fuel i wanted to sell it but i just cant bring myself to do that, right now i get around 225 mile from a full tank and thats on the M6 at a steady 72 to 75 ish.

can i up load pictures to show you the vacuum gauge, it maybe Hg and not Psi, i wish i had not thrown the packaging away now
 

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I only wanted to see what the car can boost too without the APC connected,
This is really not a good idea.

There's a bit of confusion going on here about your boost figures which needs clarification. On a stock T16, your peak boost should be 0.75 bar, which is 10.8 psi. This is around the border of the red section on the APC gauge, usually a little below. Fuel cut/overboost is 1 bar (someone else should confirm this, as I'm one of them wacky LPT types which are different). At idle, it should be around -0.5 to -0.7 bar, which is -0.7 to -0.10 psi. On overboost, accelerating hard then letting off quickly, you might even hit lower.

Your base boost should be set to half your peak boost. use the links I posted earlier for more details. Since you don't know what the car is running at, and bearing in mind that one overtaking manoeuvre could blow your engine apart by melting a piston, quite apart from any head gasket issues, you need to get it back to stock as soon as possible, and then if you want, tweak it up gradually, using other mods to help protect the engine as well as only running high octane fuel. You really need proper pipework as well. replacement rubber vac hoses are fine, silicon is even better. If you have one small vacuum leak that can ruin the way the car drives.

Your running rich could be a load of things. It is probably a good thing at the moment, because it is preventing you from leaning out with your unknown rate of boost. If you are really on 20 psi regularly, which is the end of the red, and have no other mods, then you really need to back it down. Get it back to stock then we can start troubleshooting the other issues.

You can upload pictures by using the Manage Attachment button when you post a reply to upload them as attachments, or you can host them on another site and use the
button to put them in IMG tags.
 

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Discussion Starter #11 (Edited)
I will take some pictures tomorrow.

Honestly I am trying to make my car standard, unlike the last owner.

I want to get it to 350K and i know if I push it that wont happen.

I replaced a few vacuum lines and i have even more vacuum now, the reading is 20 now, its smoother and quiter as well, there is less of a fuel smell from the exhaust.

Funny that when i turn on all my lights and fan heater the vacuum reading drops to 18.5, i know the alternator gets stiff with that kind of current draw, its just nice to see and know how much effort it takes from the engine.

This forum has helped me already, thank you all.
 

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just semantics here...


as was earlier posted by orca- there is no such thing as '18 psi vacuum'. the correct measurement of vacuum is done in inches of mercury: 'in/hg'.

it is physically impossible to have 18psi of vacuum as 'psi' denotes 'pounds per square inch'.

30 in/hg is perfect vacuum. on throttle decel a healthy engine should see 25-28 in/hg.

James
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http://www.saabworks.com
 

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Discussion Starter #13 (Edited)
I managed to take some pics and load them up.

The second picture of the after market gauge, the non running reading at 0 Psi or Hg am not sure TBH?

The third picture is at idle, siting at minus 20 now as i replaced the vacuum lines with new clear poly ones.

The Saab gauge sits at around 10 o,clock now when the engine is idling.

is this normal?

What is a Hg equal too in Psi for pressure?

Just so you know, When normally driving I try and keep the needle from crossing the 0 point and this is just before the yellow area on my standard gauge.
 

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