SaabCentral Forums banner

1 - 20 of 59 Posts

·
Registered
Joined
·
1,603 Posts
Discussion Starter #1
I want to take a look at my vac retard module.... have a look inside and possibly improve the way the car lays down the power...

I have been searching for any pictures of a open vac module or better still a walkthrough ! .....

I am a bit scared to to open it up to be truthfull...... anything I could break in there ?
erm.... how do you open it up :oops: is it a screw top?
 

·
Registered
Joined
·
1,603 Posts
Discussion Starter #2
and......... If my Vac module was not retarding enough under high boost, what symptoms could I expect?
 

·
Registered
Joined
·
295 Posts
Why don't you try opening up a carb/i Saab's vac module first? They are dirt cheap, I suppose you could get one from a junkyard with a few dollars.

Open it up first and as soon as you get to know the internals a little better, then open up the turbo vacuum capsule. The turbo capsule is a little bigger so it must have some differences but it would seem logical to open up an almost similar, but a cheaper, capsule first and then go for the turbo version.

And if your vacuum capsule doesn't work, you will experience knock at boost. Ignition must be retarded when boosting. You need less retard off-boost, and more retard on boost.

Good values to aim for are around 18-22 degrees off boost and around 10 degrees on boost (at least around 1.0bar). And yes I know you can't do that much retard with the stock capsule, that's why you either buy the AID unit from group9performance or modify the OEM capsule or buy an electronic boost retarding unit such as the MSD BTM6)

-John
 

·
Registered
Joined
·
135 Posts
I guess you're talking about the vac/boost mechanical timing pot on the distrib...not the ignition module that controls the spark and dwell.

Here's a drawing done by Raul:
http://saabpics.com:3000/albums/album22/aid1.jpg

the pic isn't too perfect but kinda works. It's been awhile but, here goes...there's two membranes bound together at the springplate, the membranes are separated by a high density plastic parameter spacer, this spacer also determines the vac/boost chamber size b/c the lid rest against it. No problem w/ opening the unit if done right. You have to cut on top along the edge where the pressed fold is, but don't cut through the lid.

Here's about as far as I got with a webpage, I try to ditch mechanical controls:
http://www.pajjakid.com/ubipa/Ign%20Pot%20DIY.htm


Search saabnet perf bb for "c900 timing" that I responded to, there's a small thread.
 

·
Registered
Joined
·
1,603 Posts
Discussion Starter #5
Ok..... Now im starting to understand.

So, the easy mod is to bend the retard stop? ..... So, I assume its almost impossible to break anything when taking the complete vac pod off the distributer.... Then its a simple case of bending the retard stop (red arrow?) in the correct direction? ..... which is?

in the direction of the blue arrow or green arrow?

 

·
Registered
Joined
·
3,467 Posts
Take the unit off and have a look, the stop will be up against the advance arm (not really shown in the pic) you need to close up the gap by bending the stop slightly.
 

·
Registered
Joined
·
295 Posts
But if you are closing up the gap then you would be lowering the retard?

I understand that if you close the gap, you eliminate the stock retard, and then you should add f.ex. an electronic controller like MSD BTM6 that would manage all of the retard.

But if one wants to modify the OEM capsule to give MORE retard, shouldn't the gap be increased?!?

-John
 

·
Registered
Joined
·
1,603 Posts
Discussion Starter #8
yes, I have a stock unit and I will be wanting to increase retard as at 1 bar max boost the engine seems to stutter quite a bit unless I go for a night time drive...as the air temp is considerably lower and I get fantastic performance..... If could achieve a 100% stable 1 bar even in summer day time conditions I will be happy.....

I am hoping this extra boost retard will help me to achieve this? ..... but as the post suggests, im new to this.... so what do I do, open it up or close it down :-?


I diddnt want to get into the specifics of what my problem could be, but the only thing I have not checked out is the timing..... Retard seems to be the next logical step to tamper with.... Pulled the plugs today..... very normal wear so the A/F and head/block seem to be A1.
 

·
Registered
Joined
·
3,391 Posts
You need to allow the boost to push the activator further. I filed mine about 1/16" IIRC. Bending it had not occured to me due to loss of integrity of the stop. I did use the stop as a push to leverage the small file off of. This may have been described before.
 

·
Registered
Joined
·
1,603 Posts
Discussion Starter #11
I don't think you have to cut the capsule open to perform the mod.
But you can try it as Ubipa explains for more control.

As I understand it the whole capsule should be detached from the distributer with 2 screws to expose the retard stop we have to adapt..
 

·
Registered
Joined
·
510 Posts
Does bending the stop curve do the same thing as spending $200 for an AID? I thought there were other advantages to the AID. Somethings like easily modifiable and handles 20 btdc off boost.
 

·
Registered
Joined
·
57 Posts
I'd like to do this mod too, but am new to this and am not really clear on what to do. When vacuum is applied the advance arm goes up right? so when boost is present is it pushed down, but only to a point as the round stop tab is in the way? So if you bend the stop tab downwards the advance arm will go lower under boost? Or is that totally wrong? I'm really confused!
 

·
Registered
Joined
·
4,666 Posts
I think the AID has a stiffer spring to make the retard me linear with boost and is also externally adjustable. It can be a bit of a pain to keep having to remove the end stop and bend things to adjust the amount of timing.
 

·
Registered
Joined
·
4,666 Posts
NSE said:
I'm going to have to try this. Knock is killing my boost. I measured the retard last weekend and got about 14 degrees retard.

So, if we are cutting the capsule open, how do we close it up?
Do mean 14° retard, or the timing is retarding to 14°? If it is only coming down to 14° what is the timing at idle with no boost?
 

·
Registered
Joined
·
1,603 Posts
Discussion Starter #16
I hold my hands up high here ! ....... I would welcome ANY advice about T16 timing at all! ..... The more basic the better..... I had thought that increasing the retard was going to help out my boost but new spark plugs/electrics seemed to do that / fix it anyway' recently.
but maybe this extra retard is a good thing anyway?..... At the moment with my new electrics I hold a steady 1 Bar boost..... Should I worry about extra retard?
 

·
Registered
Joined
·
3,391 Posts
Garry,
The timing is done in reverse to na cars. Place a pressure equivalent to your max boost + about 2 lbs on to a line connected to the vac module. Time your engine at idle to the most retarded setting desired. I'm at 9º btdc. Connect the vac back to the intake and read the timing. My vac has been modified to allow 23º btdc at idle. I like the high advance because it allows the engine to breath while not under boost. At 10º btdc the apc cuts out about .25 bar earlier with my set up. I hold 1.5 bar. I paid $3 for a junk yard vac cap, and modified it. I also tested it removed from the distributor with air pressure equivalent to verify that it indeed would retard as required. IIRC about 10 psi would take it to full retard. I liked that because predetonation would be reduced if the heat produced by early firing, was removed. The amount to file was calculated by comparing the unmodified movement of the vac cap, with the normal retard amount (5º) and the desired retard. BTW search earlier posts. Luck.

PS- DO NOT CUT OPEN THE CAP. You only need modify the space between the stop and the L shaped cut in the actuator arm, at atmospheric pressure.
 

·
Registered
Joined
·
563 Posts
Alex said:
NSE said:
I'm going to have to try this. Knock is killing my boost. I measured the retard last weekend and got about 14 degrees retard.

So, if we are cutting the capsule open, how do we close it up?
Do mean 14° retard, or the timing is retarding to 14°? If it is only coming down to 14° what is the timing at idle with no boost?
It is retarding to 14 degrees. I have the timing set at 20 deg. at 2000 rpm as per Bentley. From what I have read, I should set it to around 10 deg. on boost. My boost currently peaks a little past 3/4 of the yellow on the APC gauge but quickly drops to about 1/2. Pressumably the APC is lowering it due to knock.

*edit*
PS- DO NOT CUT OPEN THE CAP. You only need modify the space between the stop and the L shaped cut in the actuator arm, at atmospheric pressure.
Thanks for clearing that up. :)
 

·
Registered
Joined
·
2,879 Posts
Wow NSE, that's not much boost!
I get a bit into red, then backs of to hold just before the yellow/red line, then declining, depending on fuel airtemp. and so on...
Will be looking into this mod myself aswell, maybe a swing by the junkyard next time I'm in that area will do me good :D
Btw: Willy, thanks for the basic's of the vac-module, will help me a lot...
Daniel
 

·
Registered
Joined
·
563 Posts
Saab-Daniel said:
Wow NSE, that's not much boost!
I get a bit into red, then backs of to hold just before the yellow/red line, then declining, depending on fuel airtemp. and so on...
Can't wait until I can get into the red. My tranny is on the way out so I'm waiting to replace it before modifying the engine/increasing boost. Hoping the tranny will last another month if I take it easy.
 
1 - 20 of 59 Posts
Top