APC Mod Question [Archive] - SaabCentral Forums

: APC Mod Question


Custard
14th May 2002, 03:10 PM
Would anyone be kind enough to provide me with a rough starting point to start adjusting my APC? Something along the lines of turn P pot x number of degrees/turns and F pot Y number of degrees/turns? Just want to know the best starting posistion and then go from there. I've never played with a turbo setup like the T16 has before so any help is gratefully recieved. What sort of power might I get just by playing with the APC?

One more thing does anyone know how the sections on the boost gauge (orange/red) corrolate to the actual boost pressure?

Thanks In Advance

Alex
14th May 2002, 03:49 PM
A good place to start is Tweakers site at

http://www.geocities.com/tv41mxa/tweakyourapc.html

This gives some starting resistances to go with, easy to measure with a multimeter.

On the standard boost gauge, the end of the orange segment should be around 12psi. However it is not unusual for these to read inaccurately. Its not the expensive to get a calibrated gauge.

Marko A
15th May 2002, 01:48 PM
Custard,

Do you have ohm-meter? If so, Iīd suggest you to try for start something like F-400 ohms and P-15Kohms. This should not give any spikes etc. Without ohm meter, adjust pots (see little arrow on the indicator) F to 11.00 and P to 7.00 (like clock dial).
If it spikes too much, reduce P.

"Adjust F & P to taste, P for boost rise rate, F for high RPM boost pressure"

(and P gives the peak around 3100 rpm)

Iīd suggest you to not to go over 1/2 of the red zone. On my boost gauge itīs 1bar roughly. Without any other mods keep that as a maximum limit. Boost will taper to 1/3 on the red no matter what.
Then, Exhaust,Intake,Fuel supply(Chip for Lucas!),larger IC, water injection... :eek:

With your Mitsu turbo, APC is not really clever. It has been designed for Garret T03.
Mitsu spools up quicker -> APC is too late...

Problems, questions, donīt hesitate to email me.


./uploads/Lucas.jpg

Johann F
16th May 2002, 04:13 AM
Marko,
This is pretty much what I have settled for on my 91 (with a few mods to fueling intake and exhaust + the Red box mod ) - maxed out F and gradualy reduced P until I got rid of spikes. Depending on the fuel it goes up to about 1bar and comes down to just inside the red after a few seconds or at high revs. Plenty enough power for overtaking manouvres and no sudden surge or spike to put a sudden load on the gearbox or unsettle the front end.

Reincheck
16th May 2002, 06:11 AM
Marko A!

I tried to email to you considering apc mods, but your email, do not work.

Jani

Custard
16th May 2002, 11:43 AM
Just finished tweeking. Set F pot to about 12 o'clock and P pot to about 8. Car now boosts halfway into the red (just a touch over half up hill in third) then winds down to just inside the red. It drives mucg better now, the feeling of lots of power then not a lot as it drops the boost at high rpm's has gone now.

Whats the next step? Chip for the Lucas to up the fueling or will it be ok at this level with the standard setup? I don't think I'll go much further just a filter and exhaust. The APC seems to be functioning as it should, will it still protect the engine at this level or should I get a chip for it?

Thanks

tom
16th May 2002, 12:07 PM
Chip for APC or are you talking about the ECU? I have a modded APC box. It came of a 9k, and the seller told me it was chipped. I thought he was talking about the mod. I was under the impression the ECU is chipped and the APC unit modded?

btw, the new modded APC unit is set to boost all the way up to 1,5bar. A bit too much for my 8valver. So I have to tame it down a bit.

Janne Selinummi
16th May 2002, 04:27 PM
There can be misunderstandings in this area, sometimes sellers tell the car's chipped, even though only the APC has been modded.

The chipping procedure for your car is to reprogram the fuel injection computer, and this is done by changing the "brain" chip of the FI ECU. Such a fuel chip you can get, for example, at BSR. (www.bsrab.se)

Johann F
16th May 2002, 04:52 PM
Custard,
The APC will still be protecting the engine with your mods - as you are finding when the boost drops back after short time of boost. Extra fuel won't prevent the boost from cutting back or tappering at these levels - if you were to mearure the A/F ratio you are not running lean. it's just that the combustion temperatures are getting too hot to handle this amount of sustained boost - without making funamental changes to the engine and turbo - water injection is the only way you can keep the in -cylinder temps down. What a fuel chip or a RRFPR will give you is a bit more 'zing' - better throttle response and quicker revs pick up.

Marko A
16th May 2002, 10:02 PM
Reincheck:

There was a mistake on my email address, didnīt notice it before. Thanks for notifying.It should work now.
ANyway, itīs marko.alatalo@kotinet.com

Custard

Your APC function sounds very much normal. Iīd still suggest you to reduce P a bit since, if you are going 1/2 red or little more, you are possibly really close to fuel cut switch.And that could be really dangerous (and frightening) like during overtaking.

Go on with the mods you described. Intake, Exhaust,Fuel etc.etc. If you experience boost drops on high rpm (over4500) thatīs just normal and can be cured with other modifications. Might need a degree or two more timing retard under max boost,
time will tell.

johniemi
13th August 2004, 02:28 PM
Could someone please tell me how do you measure "12:00" or 7:00"? I mean, I have the box on my table now and I'd like to try out Marko's and Custard's settings. Which way do you hold the box in order to set the pot at f.ex. 12:00?

Box sideways so that the letters P F and K can be read normally (25 pin connector at 3:00)?

Box so that the 25 pin connector is at 6:00?

I have the BSR mod, and it seems that it's the passive mod you are talking as I get a huge spike to 1.5 bars and then a stable 1.0 bar boost up till redline. I'd just like to get rid of the spike, maybe 1.2 spike could still be ok. I have the stock Mitsu TE5-12b turbo.

Actually I like this mod so much due to the stable boost that I was planning to put a Dawes device into the inlet manifold that would open at around 1.1 bar, thus bleeding some of the excess boost spike air into the atmosphere thus lessening the spike. Could that work? I assume it would work because the fueling is already maxing out so the air/fuel ratio would remain pretty much the same although some of the air is bled out?

-John

Janne Selinummi
13th August 2004, 04:26 PM
I'm not sure about the clock positions, bit I do remember it was the "most obvious" way round. I can't remember which way exactly :oops:

About the bleed valve, perhaps a second APC solenoid in conjunction with a pressure switch? That would be smoother and more secure IMO. Big surprise: That's what I'm doing :D

keymosaaby
15th August 2004, 01:52 PM
try this site for modifying APC... http://www.900aero.com/ ...look under tech info tab, hope that helps

Alex
15th August 2004, 03:28 PM
The clock postions are related to the orientation of the APC as installed in the car, which is with the wiring from the bottom.

Kaas
16th August 2004, 02:48 PM
Mine 900 t16 from 1990 with lucas, has 195 hp and 292 Nm. I have mod. my APC and vac. module and set the base boost to 0.5 bar. It's a little over middle in red in 5 gear "1.2 bar" and it do not spike. It holdes the max boost steady :D
R42 = By passed with wire
R138 = 40 K.ohm resistor
R40 = 1300 ohm resistor
P = 13,7 K.ohm
F = 332 ohm

Vac. module : 19 degrease at idle and 5 degrease with 1 bar of pressure.

http://www.home1.stofanet.dk/900turbo/195,5hk.jpg

Lars - Denmark

Reincheck:

There was a mistake on my email address, didnīt notice it before. Thanks for notifying.It should work now.
ANyway, itīs marko.alatalo@kotinet.com

Custard

Your APC function sounds very much normal. Iīd still suggest you to reduce P a bit since, if you are going 1/2 red or little more, you are possibly really close to fuel cut switch.And that could be really dangerous (and frightening) like during overtaking.

Go on with the mods you described. Intake, Exhaust,Fuel etc.etc. If you experience boost drops on high rpm (over4500) thatīs just normal and can be cured with other modifications. Might need a degree or two more timing retard under max boost,
time will tell.


_________________
Marko Alatalo
SAAB 900 TurboS
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<font size=-1>[ This Message was edited by: Marko A on May 17, 2002 3:05am ]</font>