MSD boost timing master? [Archive] - SaabCentral Forums

: MSD boost timing master?


johniemi
16th May 2003, 04:46 AM
I am getting the MSD boost timing module for my T8 900. Do you guys have any suggestions how should I set it up (meaning, how much retard) and what should I do _first_ to the standard ignition system before fiddling with the MSD settings? Do I need to modify the springs or the vacuum system?

FYI: I am running also a fifth injector, aquamist water injection, 3" downpipe etc. Unfirtunately I only have the stock garret T03 turbo and will raise the boost as much as the stock unit can handle... 1.3-1.5 bars maybe?

So what kind of ignition setting would be good around 1.5 bars? (1.5 bars = ~22psi)

-John

Carl Hernandez
16th May 2003, 02:24 PM
www.twinsaabs.com has a good guide on how to set up the msd unit.

johniemi
18th May 2003, 05:35 AM
Thanks! That really helps me.
-John

tandino
18th May 2003, 11:51 AM
I think ive found the ideal set-up with the BTM,
I run 22'BTDC at idle (giving good off boost drivability)retarding to bang on the nail 11'BTDC on full boost.
Ive disabled the retard at the vacuum capsule so all retard is taken care of solely by the BTM.
Ive got a pressure relief valve in the vac line to the BTM module which is set to 13 psi - therefore all retard is in by this stage.
Hope this helps.

Pete.

johniemi
19th May 2003, 04:19 AM
I think ive found the ideal set-up with the BTM,
I run 22'BTDC at idle (giving good off boost drivability)retarding to bang on the nail 11'BTDC on full boost.
Ive disabled the retard at the vacuum capsule so all retard is taken care of solely by the BTM.
Ive got a pressure relief valve in the vac line to the BTM module which is set to 13 psi - therefore all retard is in by this stage.
Hope this helps.

Pete.

Thanks for your opinions as well! All these different setups really help me to figure out the best for me. Just two things; what is a pressure relief valve, i.e. what does it do?

Also, doesn't T8 have centrifugal (?) weights in the ignition to retard timing alongside with the vacuum retard?

By the way, how do you measure the ignition at boost? Do you have some sort of high pressure air pump that you use to pump f.ex. 1.0 bar air into the MSD BTM? I was just wondering because I don't think I can drive the car with 1.5 bar boost and at the same time try to measure the timing under the hood with a timing lamp :D

-John

Carl Hernandez
19th May 2003, 07:50 AM
hehehe.
a pressure relief valve is nothing but a valve with a ball inside of it that you can set the bleed pressure at IE: when the car hits 12psi of boost it will start to bleed air off of that line and all the pressure in that line will be at 12psi.
the 8v turbos do have a mechanical advance. but no retard, as this is controled by the vaccum canister (i could be wrong here).
and finaly as for the last one i am not really sure, i believe that by using some sort of equation that you can figure it out.

john-w
19th May 2003, 07:55 AM
Nothing so scientific :lol: :lol: just pete's old bike pump and a boost gauge :roll: :roll: Pump up the vac canister and watch the timing :! :!

johniemi
19th May 2003, 08:05 AM
Nothing so scientific :lol: :lol: just pete's old bike pump and a boost gauge :roll: :roll: Pump up the vac canister and watch the timing :! :!

Ok. What do you mean by the "vac canister"? Is it the line going into the MSD box? Sorry but my english isn't very good...

tandino
19th May 2003, 08:17 AM
Pressurise the btm line with the bike pump and you can them set the timing with the btm dial to get the toal amount of retard you want to go down too.
Dont forget the retard you add with the BTM will be on top of the retard you get with the distributor vacuum capsule unless you bend the tab in the capsule to remove this.

Pete.

johniemi
19th May 2003, 08:24 AM
Pressurise the btm line with the bike pump and you can them set the timing with the btm dial to get the toal amount of retard you want to go down too.
Dont forget the retard you add with the BTM will be on top of the retard you get with the distributor vacuum capsule unless you bend the tab in the capsule to remove this.

Pete.

I am probably going to disable all other ignition retards except the one that MSD box offers... Could I just put a bearing in the vacuum line to disable the vacuum retard?

What do you mean by "bending the tab in the capsule"... What tab? What capsule?

-John

johniemi
19th May 2003, 08:31 AM
Oh yes, one more thing; does the 8-valve turbo have also centrifugal retard or not??? If it does, I'll have to make that inoperative as well...

tandino
19th May 2003, 08:34 AM
Dont disable the distributor capsule - this provides advance under vacuum.
What you want to do is disable the retard on the capsule and let the btm take care of this side of things.
Remove the vacuum capsule from the distributor - 2 screws then pull/wiggle it free form the locating lug in the distributor - you will see the arm on the capsule has a hole on the end - this fits over a lug inside the distributor to control the timing advance/retard.
You will see a tab on the vacuum capsule arm that limits the amount of retard that can be achieved when pressure is placed on the diaphram of the capsule.
If you connect a bike pump to the vacuum capsule nipple you will see the arm and stop move towards the metal tab - you need to bend the tab or knock it with a hammer so that there is no movement - this will then give you no retard under boost conditions but still allow for advance under engine vacuum.
Then you can now use the btm soley for retard without having to worry about the vacuum capsule also adding retard along with the btm.
Does this make sense now??

Pete.

johniemi
19th May 2003, 08:52 AM
First of all, thanks for your patience and help! Now here are a few things I need clarification on:

"Dont disable the distributor capsule - this provides advance under vacuum. What you want to do is disable the retard on the capsule and let the btm take care of this side of things."
>>>>What is the "capsule"? Is it this part: http://www.twinsaabs.com/msd/msd_enginebay.jpg the one on the very right of the picture, sitting on the distributor, that has one yellow hose running into it? I know it's called "alipainekello" (vacuum-clock) in finnish but don't know the direct translation.

"Remove the vacuum capsule from the distributor - 2 screws then pull/wiggle it free form the locating lug in the distributor - you will see the arm on the capsule has a hole on the end - this fits over a lug inside the distributor to control the timing advance/retard.
You will see a tab on the vacuum capsule arm that limits the amount of retard that can be achieved when pressure is placed on the diaphram of the capsule.
If you connect a bike pump to the vacuum capsule nipple you will see the arm and stop move towards the metal tab - you need to bend the tab or knock it with a hammer so that there is no movement - this will then give you no retard under boost conditions but still allow for advance under engine vacuum."
>>>>Ok, I understand what I need to do, but don't understand why... I mean, how is it possible to bend the tab so that it doesn't give retard under boost, but gives it under vacuum? Well, I guess I have to take the parts out and try to figure it out myself. Maybe it becomes clear when I use the bicycle pump to manipulate the arm's movement.

Or do you mean that the arm moves to one direction under vacuum and the other direction under boost? F.ex. under boost, arm moves to left and under vacuum arm moves to the right. And I want to disable the "under boost" movement which means I bend the tab so that the arm cannot move to the left and can only move under vacuum (to the right)?

But as I can mimic the boost conditions with a pump, how could I then mimic vacuum just in case I want to test whether the vacuum retard still works and I haven't broken anything when bending the arm?

tandino
19th May 2003, 09:58 AM
Right ive taken a couple of pics to clear things up :! ,
The bottom is of the capsule itself,
The top is a close-up of the arm and the tab that it contacts with to limit retard (the tab is the raised round bit!) - you need to close up the gap completely to stop retard occuring on boost.
You will still get advance as you are only limiting the travel of the arm in one direction.
here's the pics:-
Hope this helps :-??

Pete.

johniemi
19th May 2003, 11:41 AM
Great pics, thanks!

So can I just weld some metal on the cap or put some "plastic padding: chemical metal" on the cap? Or do you suggest bending the arm? And if so, why?

Thanks!

Nuts
19th May 2003, 12:19 PM
Bending the arm is the easiest way IMHO, rather than messing about with glues & the possibility of FOD (foreign object damage - I like the term 8) ) - a couple of taps with a suitable drift & hammer will sort it out - the gaps only small as mentioned by Pete.

john-w
19th May 2003, 12:22 PM
You can just knock the tab with a drift, it will move enough to close up the gap!!

Nuts
19th May 2003, 01:20 PM
You can just knock the tab with a drift, it will move enough to close up the gap!!

Sorry, that's what I meant - bend the stop on the arm :! And not the arm itself :!