SaabCentral Forums banner

1 - 20 of 28 Posts

·
Registered
Joined
·
731 Posts
Discussion Starter #1
Hi...

I've just got one of Spatl's lovely MBC+A kits to go on my CSE 2.3T. The setup is in 2 stages - first set up the (ball and spring) MBC as normal, then set up the +A part. Trouble is, I've never use an MBC before so I'm a bit clueless.

Is there a good idiot-proof procedure?

My guess is that I need to set it up so that I can't hit the fuel cut-out no matter what I do.

Is there a direct correlation with the non-Aero turbos between the amount of boost and the RPM? It seems to me that no matter how I adjust the MBC, the peak boost above about 3000RPM is pretty much the same - I am wondering if this is a limitation of the turbo. In other words, do I need to concentrate on adjusting the boost at low revs?
 

·
Registered
Joined
·
7,975 Posts
john, if you cant get higher than standard full boost ie 1bar, then your waist gate actuator is weak and the exhaust gas pressure is forsing the gate open, i had the same prob on my 2.3 carlsson, you need to deal with this first before setting the mbc is possible
 

·
Registered
Joined
·
731 Posts
Discussion Starter #3
I was wondering about that ... but I can in lower revs, and in higher gears, and I think it holds it OK. I haven't really had enough time to play yet. But I was also thinking.. I know the T25 is limited .. i.e runs out of puff at higher revs. I was wondering what this translates to.. how soon it happens, and what sort of max boost we are talking, e.g. at 3000rpm or 4000rpm, assuming wastegate stays closed.
 

·
Registered
Joined
·
731 Posts
Discussion Starter #4
I am beginning to think you may have a point, Boxman. I am finding that avoid hitting the cut out, I have to set the boost at a point where the car is generally more mild than it was with the APC system. Generally the boost rises quickly in a couple of seconds up a to a peak, and then within a couple of seconds more falls right back to a much lower level.

The pressure I get in any given situation is quite variable, but I'm not sure how normal that is - I'm not sure how many variables affect the boost pressure (e.g. speed, gear, throttle position, rpm, gradient, etc.)

Trouble is, an actuator is not cheap, so it's not a case of just saying to heck with it and fitting one to see if it helps!

The "boost spike" that people talk about with MBC's.. how much is it usually, and how long should it last?

Also, with an MBC, would you expect the pressure to hold steady, or to taper off, and if so, how much and how fast?
 

·
Registered
Joined
·
640 Posts
not worth it fitting your car with MBC as the boost will be floating.

invest a bit more money and get an electronic boost controller so that you dont have to get out of the car to adjust the boost + have a couple of modes saved and switch between them within miliseconds + also set up so that the boost is not floating.

example: greddy profec b spec2
 
R

·
Guest
Joined
·
0 Posts
My actuator is weak too, so I followed Basre's advice and added a slave spring.

Started gently and then reversed the bracket to give it a bit more tension. The pic shows before the bracket reversal (the one on the actuator body).

This has stabilised my boost to 1.1 bar. Like you, I didn't want to spend another £100 (just now). The spring cost me 20 pence and I used bits and bobs that I had rolling around in my toolboxes.
 

·
Registered
Joined
·
731 Posts
Discussion Starter #8
That certainly looks to be worth a try! Out of interest, should I decide to replace the actuator at some point, can it be replaced without removing the turbo?
 
R

·
Guest
Joined
·
0 Posts
Yeah, a two minute job.

Undo the two bolts you can see in my second picture, then remove the 'R' clip from the wastegate control arm (the other end of the spring) and slide the end of the actuator rod off. Oh, and you have to pull off the pressure supply pipe from the APC solenoid (or the turbo if you don't have APC).

When ordering a new one you need to give the rod measurement, whether it's straight or kinked and how much boost pressure you intend to run.

:cheesy:
 

·
Registered
Joined
·
7,975 Posts
johncc said:
By the way Boxman, can you delete some PMs from your inbox? :cheesy:
done ;)

i also used a spring to help my WGA, i used a drum brake shoe return spring but i dont know from what car :roll:
 
R

·
Guest
Joined
·
0 Posts
When you fit the new actuator, you will have to check your basic charging pressure, but that's a relatively simple procedure on the APC cars. Just need a boost gauge and a bit of time for the engine to cool (or asbestos hands).
 

·
Registered
Joined
·
7,975 Posts
semyhr said:
not worth it fitting your car with MBC as the boost will be floating.
i disagree, with the set up that spalt has come up with you get very stable boost levels and at a fraction of the price of the electonic boost controllers



also, to move the boost tap to the trottle side of the i/c i used a i/c to throttle pipe from an auto, as this has a boost tap for the tranny, its not ideal but its the best i could sort out as tapping the trottle housing didnt work to well for some reason
 
R

·
Guest
Joined
·
0 Posts
For a great write up of how to set the basic charging pressure, have a look at this link:

http://www.saab9000.com

There is a fantastic passage (ooer) under 'Procedures' then 'Exhaust system and turbo' which gives all the steps in the process plus what the levels should be and how to obtain them. :cheesy:

Crikey, could we be any more helpful?! I think not! LOL! :cheesy: :cheesy: :cheesy:
 

·
Registered
Joined
·
731 Posts
Discussion Starter #14
Thanks for all the info :) I've used BillJ's procedure before in fact. What spring did you use, Returned?
 
R

·
Guest
Joined
·
0 Posts
I went to my local DIY shop and bought a little selection of springs (well, 4 actually).

Then with my head buried under the car, I chose the best fitting one and made the bracket. The space under there is pretty limited and I found that only a thin bodied spring would fit and move without catching on any of the surrounding hoses / pipes etc.

I could get you an identical spring and chuck it in the post to you if you want John.
 

·
Registered
Joined
·
731 Posts
Discussion Starter #17
That would be ace :) Do you have a Paypal account? :D

Seriously, I'll reimburse you the postage and cost gladly.

Another question - did you re-adjust your base boost after adding the spring?
 
R

·
Guest
Joined
·
0 Posts
On me mate.

Nope, as the basic charging pressure (with the wastegate closed) remains the same.
 

·
Registered
Joined
·
731 Posts
Discussion Starter #19
You suprise me. AFAIK, the wastegate involves gas pressure acting on a piston, against a spring. The length of the spring (i.e. force) is adjusted to set opening pressure. If you add another spring in parallel, you are effectively modifying the spring, and so it should change the pressure.

In my case though, the base boost setting is actually not particularly important, with the MBC+A.
 
R

·
Guest
Joined
·
0 Posts
Yes, in essence, but with a weakened actuator spring the basic charging pressure will have been lost. The slave spring puts back the resistance so as long as the base boost hasn't been adjusted to compensate for the actuator weakness, it should be roughly the same.

But you're right, probably worth checking anyway.

Even with the spring my base boost was too low (about 0.1 bar as I recall!), when I'd corrected that she suddenly woke up and started boosted accordingly. Now charging at 0.35 on base and 1.1 on full, although my aim is 1.25 bar (18 psi).
 
1 - 20 of 28 Posts
Top