mbc in series with apc solenoid? [Archive] - SaabCentral Forums

: mbc in series with apc solenoid?


saabkid37
30-06-04, 05:29 PM
how do i install the mbc so that i dont completly bypass my apc system? i did a search and found out about this method but couldnt come up with specific instructions...can anyone help me out?

boxman
01-07-04, 03:55 AM
no, remove the apc sol' and connect the MBC inbetween the compressor and the waist gate,connecting the MBC in with the sol' is the way to do it on 9-3 and 9-5 with trionic 7 which doesn't allow higher boost.

boxman

ylee coyote
01-07-04, 05:51 AM
I would disagree
I ran the mbc in series with the APC for many miles

It does give you a little more protection as long as the boost is not cranked up too much

you simply cut the w hose (hose to the wastegate) and put the MBC in here ...

start off low and work up

good luck

boxman
01-07-04, 07:44 AM
sorry to disagree ylee but as soon as the apc sees the exrta boost it will just cut it down again untill you get to the piont when the apc can't reduce it any farther so you might just as well remove it from the start

boxman

johncc
01-07-04, 08:05 AM
Does it depend on which type of engine management you have? Surely the APC on the LH/DI/APC engines can't "see" boost... it has no pressure sensor. As long as the extra pressure doesn't cause any knock, why should it reduce the boost?

Disclaimer: I could, as always, be talking cobblers :)

I'm interested because I'm trying to work out all these feedback loops - particularly in the Trionic system - to try and work out why I don't have enough boost.

marcind
01-07-04, 09:48 AM
For more protection u can use map sensor IMHO.

saabkid37
01-07-04, 10:22 AM
well based on my saab knowledge (may not be very good :-? ) the apc solenoid has a thing in it that flaps back and forth and the ecu measures the speed of that...when it reaches a certain speed it cuts boost with the knock all being detected by a sensor in the di. sooo....i believe that if you slowed the pressure to the solenoid it would allow higher boost?

thats why i asked....

boxman
01-07-04, 10:37 AM
Does it depend on which type of engine management you have? Surely the APC on the LH/DI/APC engines can't "see" boost... it has no pressure sensor. As long as the extra pressure doesn't cause any knock, why should it reduce the boost?

Disclaimer: I could, as always, be talking cobblers :)

I'm interested because I'm trying to work out all these feedback loops - particularly in the Trionic system - to try and work out why I don't have enough boost.

the lh apc up to 1990 has a pressure sensor under the dash and from 1991 on has a temp sensor to determine pressure

boxman

boxman
01-07-04, 10:44 AM
well based on my saab knowledge (may not be very good :-? ) the apc solenoid has a thing in it that flaps back and forth and the ecu measures the speed of that...when it reaches a certain speed it cuts boost with the knock all being detected by a sensor in the di. sooo....i believe that if you slowed the pressure to the solenoid it would allow higher boost?

thats why i asked....

the thing inside the apc sol' that flaps is controlled by the apc ecu and not boost level and its job is to limit the amount of boost that the waist gate sees and bleeds off the unwanted boost, if the boost level is higher than the limit programmed into the ecu, the ecu will flap the apc sol' less so less boost is bleed off therfore plying the waist gate with more boost so it opens so reducing to boost back to the preset limit

boxman

johncc
01-07-04, 11:51 AM
the lh apc up to 1990 has a pressure sensor under the dash and from 1991 on has a temp sensor to determine pressure
boxman

That's what I love about this site - always more to learn! Thanks boxman. Does the trionic use the MAP sensor for the same purpose, or does it have another sensor elsewhere?

boxman
01-07-04, 12:11 PM
trionic uses the same sensor as di apc to deturmine boost its the one in the i/c to throttle pipe, the trionic map (manifold absolute pressure)sensor replaces the lh air mass meter to deturmine the amount of air entering the engine

boxman

ylee coyote
01-07-04, 06:02 PM
Wiring it in series does have advantages
by altering the pressure on the wastegate by bleeding the pressure off (bleed mbc) or stopping the pressure getting to it (gated mbc )effectively takes the control from the apc untill the pressure /bleed threshold is reached than apc control is re-established

what this does is radically alter the spool up as normally the apc starts to open the wastegate at very low boost
It does this to stop overboost but it is very conservative
the mbc simply moves it up the boost map hence you do get more spiking but removing the apc entirely you will not have control over the mbc boost threshold...

imho of course

saabkid37
01-07-04, 10:23 PM
ok well i got my turboxs mbc yesterday and installed it tonight in series as i wanted..

verdict - its amazing! I have it turned up to about 20psi. it holds for 3-5 seconds and then slowly knocks me down to 15-16 ish...im guessing beacuse of knock and not due to the apc. So...if i eventually fit a larger intercooler and run some higher octane fuel i should be able to hold the boost and hopefully not toast my motor :o

boxman
02-07-04, 04:07 AM
well guys you will just have to trust me one this one :lol:

if you run your car around for a few days and then remove your MBC you will find that you have no boost 'cus the apc is trying to reduce it and can't so it will have remembered that and will be running on base boost

saabkid37
02-07-04, 09:56 AM
i believe you...but ill just worry about that if i ever remove the mbc...just wanted to let everyone know that it can work while keeping a litle more safety in my opinion.

boxman
02-07-04, 10:44 AM
the apc sol' is doing nothing to protect you engine, what is happening is the di side of it can reduce boost if the apc can't by retarding the spark, this is what is causing your boost to tail off.

to protect against boost spiking take a look here (http://www.saabcentral.com/forums/viewtopic.php?t=25211&highlight=mbc)


boxman

G96nt
02-07-04, 11:39 AM
think of it This way..
the Solenoid is told When to open And close by The ECU.
When There is knock, the solenoid opens, and allows the wastegate to "see" The Actual Boost, and open the flapper valve.

if you put the MBC between the solenoid and the wastegate, pressure will NOT get past the MBC until it meets whatever you've Set the preload for.

so, if you've set the MBC for 15Psi, pressure will NOT get past it to open the wastegate To open untilis sees 15Psi. Which means your car will be running equal-to, or greater than "x" boost ALWAYS. no matter what...
if the car is not knocking, the APC will close the "W" line, and the MBC will See NO boost. meaning you running full boost..which is okay.

now, if you DO knock, and the APC opens the solenoid, it won't Affect the MBC/wastegate until AFTER you've Reached whatever Psi you've set the MBC at.

we'll call this.."bad" or..."wrong"
you pick :D

if you place the MBC between the intake manifold and APC solenoid, you are more or less just lying to the APC.
It may "see" 10Psi, but prior to its knowledge, you have bled off 4 Psi. resulting in the net boost of 14Psi

this Still allows the APC to pull bost according To knock, but It will ALWAYS think it's lower than it is...
This way still allows the solenoid to control the wastegate flapper through it's intended range, and help prevent Detonation. you're just convincing it that there's less boost than there really is.

we'll call this "safer" or "correct"
:cheesy:

boxman
02-07-04, 02:46 PM
this Still allows the APC to pull bost according To knock, :

if the apc can pull boost if it sees knock then it can also pull boost if the boost level exceeds the preset limit

if you are getting a reduction in boost when knock accures then it is the ignition that is being retarded which reduces the boost

this debate is going to run and run :roll: we may have to agree to disagree :wink:

boxman

G96nt
02-07-04, 04:32 PM
on the pre DI Cars how is timing Adjusted?
MY undestanding, is That there's a diaphram insode the distributor what is "activated" soley on boost.

if that's the case.. then it won't matter...
if the APC is lowering boost, it's retarding timing As a result.

on DI+ Cars, it's possibe that ignition is controlled seperatrely than boost soleniod.
say: map Sensor + knock Sensor +some chart = timing Advance/retard.



what I'm getting @ though... is that if you put an MBC AFTER the APC solenoid, it completely negates anything the APC does.
it'll be a COMPLETE a seperation of solenoid and wastegate, and NO pressure will pass beyond the MBC until it's higher than whatever PSI you set it at.

which means you will run, *at a minimum*, what the MBC is set For. and none less.
which is dangerous.

Especially, since his other post mentioned 20psi.

saabkid37
03-07-04, 01:20 AM
wow...im scared at some of the things i just read...crazy amounts of info :o ...20 psi was just fpr fun in an attempt to find once and for all where fuel cutoff is...but i got scared to turn it up anymore so i never found it :wink: and have since set it at a nice 18 psi or so

sorry i started a debate here tho lol....

but im confused...G69nt - are you saying i installed it a better way or a worse way? cuz from your explanation it is working just the way i wanted but im kinda confused.... :roll:

boxman
03-07-04, 07:07 AM
what i am saying is if you connect the MBC between the turbo outlet and the apc sol' and set the MBC above the preset limit in the ECU then the apc will open up the 'w' port and stop any bleed off there for technicly the pipe from the turbo out let to waistgate is only restricted by the MBC, on the same line if you connect the MBC inbetween the apc sol' and the waistgate the apc will do the same thing, the boost pressure sensor will see higher than preset boost and try and cut it back be opening up the 'w' port and stopping any bleed off, again therefore the only thing restricting the passage from turbo outlet to waist gate is the MBC, in both cases the apc is inactive

saabkid' if you are happy with the way your car goes then thats all thats important :wink:



boxman

G96nt
03-07-04, 08:35 AM
your MBC should be between the boost source, and The APC solenoid.

on *my* saab, the boost Source is Actually a nipple RIGHT off the turbo compressor.
you'd want to use that line.
*OR*
cap that line off the compressor, and use a nipple That Sees both vacuum and boost.

if you interrupt the line that goes from the solenoid To the wastegate, you're looking For Trouble.

boxman
03-07-04, 08:51 AM
i have removed my apc sol' completely

i have a pipe coming off the turbo going to a 10psimax air pressure reg' set to approx' 4 psi from there it goes to a 'Y' connector then to the waist gate, i have another pipe coming from the throttle housing to a MBC set to about 1.4 bar from there to the same 'Y' connector tha comes from the air pressere reg', the idea of the apr is to keep the waistgate primed with boost pressure but at a level too low to open the waistgate therefore when the MBC opens at 1.4bar the waistgate actuator can react straight away insted of having to fill the waistgate actuator with boost before it can open resulting in sustained high boost from the throttle tap and no spiking 'cus of the apr, becausde the MBC sees boost from thr throttle housing instead of the turbo there is no boost tailoff across the intercooler so when the boost level hits 1.4 bar it stays there

boxman

SPATL
06-07-04, 11:03 AM
It's a beautiful thing Boxman...Watching boost rise and stick. MBC+A.

Not to mention:

No pressure overshoots; even in cold weather

Higher boost levels when pressure overshoots otherwise force lower settings

No boost pressure overshoot induced clutch slip

No controller induced boost pressure droop when fed from the TB

No boost pressure induced transient AF lean mixtures

G96nt
06-07-04, 11:46 AM
I dont' understand how what he's done could stop spiking?

spiking has nothing to do with MBC, and everything To do with air mass, and Wastegate size.

spiking will lead to lean condition, sure... but as does ANY increase of boost on a non-RRFPR.


I'm lost here.... *myeh*

do what you want :wink:

boxman
06-07-04, 12:48 PM
spikes are caused when the boost rises faster than the waistgate can control it, when you fit a gate MBC the waistgate does not see boost until the mbc has opened at the set limit, the boost then has to fill the pipe from the MBC and the waistgate accuator then pressurize, all this before the boost can be reduced and in this time the boost has continue to rise at the throttle for example if the MBC is set at say 14psi by the time the waistgate actuator has responded the boost has hit maybe 17-18psi this is a spike, with the air pressure reg' fitted inbetween boost sorse and waistgate set at 3-4 psi the waistgate is already filled with boost, but not sufiticant to open it, before the MBC opens so the time taken for the waistgate to respond to the boost pressure is much much less so therefore the spike is unnoticable

boxman

don't give me the credit for this, it was spatl who devised it

Alanb
06-07-04, 05:02 PM
Boxman,

Where did you get your air pressure reg from?

Alanb

boxman
07-07-04, 03:43 AM
here (http://webstore.norgren.com/frames.asp?gourl=/catalogue.asp) go into air preparation and the part no is R07-200-NNAA

Alanb
07-07-04, 01:41 PM
Boxman,

Great site. Do you mean R07-200-NNAG ? This is the non-relieving one, right?

Cheers,

Alan

boxman
08-07-04, 03:28 AM
sorry alan the part no i gave you was the part no i was given by spatl and it is the part no for the same thing but on the US web site the part no you quoted is the correct on for thr UK site :roll:

boxman

Alanb
08-07-04, 04:40 AM
Cheers Boxman. I've had difficulty finding a decently priced supplier. Part now ordered (although rather worryingly I note that the part nos. for the relieving and non-relieving type are exactly the same :-?)

Alan

boxman
08-07-04, 07:13 AM
the relieving one is RO7-200- R NAG r= relieving

the nonrelieving one is RO7-200- N NAG n= nonrelieving

boxman

Marrk
08-07-04, 09:27 AM
Boxman,
I need you to send me an idiots guide plus piccies on what you have done as I'm very interested as I want to control my boost spikes also.

SPATL
08-07-04, 09:39 AM
I have fit a MBC+A kit on a 9000 Aero. I made up a plate to mount the APR and MBC just right of the BPC. It is monted to the frame of the car. From there, you can run your lines from the TB to the MBC and the turbo to the apr with ease. You might want to either replace the line off the turbo to the APR with a longer on or use a straight hose barb connector to add some length to it. Without a plate, you have an APR and MBC hanging around in the engine bay lookng like a snake farm. I think I have a picture I can post somewhere.

Here is the spot that seems to work best for the mount:
http://im1.shutterfly.com/procserv/47b4d929b3127cceb192d154c5fd0000001610

This is the proposed setup on the mount (if using s dawes style MBC):http://im1.shutterfly.com/procserv/47b4d929b3127cceb192c96144f40000001610

Once a TB tap place has been selected, you will take boost pressure from the TB to the MBC, the APR will be tapped at the turbo compressor, and then the two "y'd" back together to the WGA.

The mount is just a good idea to clean up the setup. It works well in the 9-3/NG900. The problem has been to find a universal location to tap the TB for boost pressure in the 9000 due to the many changes of the TB in that car.

If you do something that works, please post about it. I am interested in what others think of this rig on a 9000. The cold weather will really be the telltale time for the rig.

SPATL
08-07-04, 09:59 AM
One other note, on certain years, 1993 being one of those years, there is no real good location for tapping boost at the TB. Therefore, this setup can still be used, but the turbo hose will need to be y'd to split the line so that the apr and MBC are run in parallel and then "y'd" back together to the WGA. The APR will allow pressure up to its set pressure and not any more, somewhere around 5psi, enough to fill the line with air but not enough to crack the WGA off its seat. Once the MBC's ball lifts off its seat, the pressure from the MBC will be greater than that of the APR pressure and the MBC will see business as usual. The length of lines is less worrysome being that the line is primed. The mount location only extends the hose length by less than a foot.

While you think about a good boost tap downstream of the IC, Boxman has found a good one using a brass barb tapped in a blank. The 9-3 uses a 3/4" hose tapped with a straight hose barb between the TB and the IAC. If your car uses an AIC, that might be a good sorce as it is closed loop. Off boost the AIC is open, on boost, it is closed.

Alanb
09-07-04, 03:08 PM
Jeff and Boxman,

I've now set up the MBC+A in my Aero but I have not really noticed much difference (i.e. boost spike and then taper). I bought the Norgren R07 model. It has about 10 turns from fully closed to fully open (i.e. 0 psi to 10 psi) and I have it turned about 5 times. I'm running the anticipator and MBC in parallel with anticipator going from compressor to wg and MBC from TB to wg.

Does it matter where you tap the vacuum source around the TB? I've just tapped mine from a line that goes to the boost gauge. Might this be a cause of the problems? Unforunately, this is a TCS car so I don't have an AIC to tap from.

Cheers,

Alan

boxman
11-07-04, 05:04 PM
hi alan
jeff and i have discussed this and have come to the conclusion the the boost tap isnt important as long as it sees boost cus as the manifold sees vacumm the MBC closes, but what i did find on my 9000 is the size of the tap needed to be the same size as the turbo tap also i think the MBC needs to be turned up after moving the tap the the throttle body. are you saying that you still get the spike if so your waist gate might be too stronge 'cus when i did your trick with the extra spring on it i had trouble with spiking so i had to use a weaker spring.

boxman

Alanb
12-07-04, 08:36 AM
Excellent point about the spring Boxman :wink: I have a sring assister fitted at the moment and my base boost is somewhere around 14psi :oops: I should have thought of this!

Alanb

SPATL
19-07-04, 09:12 PM
Any Progress on this AlanB? Where are you guys attaching your assistor spring on the 9000. I've seen this done on a c-900 but not on a 9K.

boxman
20-07-04, 03:39 AM
i hooked one end of the spring through the split pin that stops the waist gate actuator coming off the waist gate then the other end to a little braket that i bolted to the waist gate actuator mounting bolts.