Boost issues... [Archive] - SaabCentral Forums

: Boost issues...


rage
14-12-03, 01:27 PM
Bit of a strange one this...

Fitted a boost gauge yesterday and replaced most of the vacuum hoses with silicon ones. I had to plug my new boost gauge into the system somewhere so i temporarily used the hole for the original boost gauge, where it goes into the inlet manifold, just until i could get a tee piece. Boost has been improved, showing base boost of around 4psi. Maximum boost was 14psi knocking back to 9-10psi after 4krpm. Car felt much quicker than recently until today. I got hold of a tee piece and plugged the original gauge back in so i now have 2 gauges. However, maximum boost is now only 10psi all the time. Vacuum hose leading to original gauge split :-?? Admitedly i haven`t been outside to make sure none have fell off. Any ideas other than that?

What should my base boost be? 4psi seems a little low. The saab board at my ex workplace showed 0.43 bar for base boost on a B202 with performance kit. Not sure how many psi that is? And what should max boost be? If the base boost is not right i am getting a price for a new actuator on monday cos mine is too corroded to adjust.

tandino
14-12-03, 01:30 PM
base boost should be 5.5 - 6 psi,
Aim for the high end of tolerance if poss..

Pete.

rage
14-12-03, 01:43 PM
Cheers for the quick response Pete. Do you think 14psi is too high though for max boost? This is with my apc plugged back in, not the MBC :nono;

I can appreciate this will vary from car to car. I mean you have 17psi ( i think) but thats with a lot of mods.

Johann F
14-12-03, 02:08 PM
Did you disconnect the hose altogether that goes into the bulkhead? - this is needed by the APC to measure boost and if you unplug it you will get strange boost behavior as teh APC is not seeing boost. Actuators are pretty expensive new - have you tried removing it from the turbo and working it free in a vice? As Pete says base boost should be the upper limit - if your base boost is low it will have a direct effect on the maximum boost your APC will allow. As for maximum boost you can run - what mods do you have so far?

tandino
14-12-03, 02:11 PM
14 psi tapering to 10psi or so sounds about right - cold weather right now will help - an uprated actuator will help with spool up/reducing wastegate creep and top end boost by preventing the wastegate from being forced open at high rpms,
Im only running 17-18 psi for a combination of reasons - my Td04 flows alot more air and hence you dont need as much boost to develop power and i want the car to be drivable.
Higher boost is only a tweak of the apc for me but then reliablity (gearbox) and the fact that my big end bearings are starting to complain doesnt help :!

Pete.

rage
14-12-03, 04:21 PM
Did you disconnect the hose altogether that goes into the bulkhead? - this is needed by the APC to measure boost and if you unplug it you will get strange boost behavior as teh APC is not seeing boost.
I disconnected the hose going into the inlet manifold for the original gauge, and put my new one in place of that. Straight swop temporarily. Are you saying the original dash gauge must be working in order for the apc to work properly?

My actuator has been off in a vice but would have sheared off its that bad. Did get my hands on a 9000 one but they are different types.

Johann F
14-12-03, 04:43 PM
Yes - the hose that actuates the dash gauge also supplies the pressure transducer and overpressure switch.

rage
14-12-03, 04:49 PM
I see. Best leave that plugged in then. Shame, it was going quite nicely too... Thanks for that Johann, you learn something new every day. Looks like i will get an actuator and start from scratch then. If only i new what i was doing with the red box :roll:

Taylor
14-12-03, 05:02 PM
No no no ( :

Just by a vacuum tee that has three fittings on it. Run the hose to your new gauge, then one to the stock one. It's a 20 cent and 2 minute fix.

good luck,
Taylor

Johann F
14-12-03, 05:32 PM
Taylor is right - you can run both guages with a T piece - Halfords do em in the windscreen washer accesory dept. Have you got a red box or are you trying to mod a black box? If you are going to buy a new actuator it would be good idea to get an adjustable one - that is one where you can set the spring tension. Fixed actuators are not really adjustable as you are just adjusting the preload rather than the spring force. If you are planning on running more boost -a higher rated actuator will be very useful.

Phate
14-12-03, 10:37 PM
I have an 87 Turbo that hasn't been boosting right for a while, even with this cold weather it wont boost right. The current unit is the stock Garrett M14 turbo, and has recently been replaced with another M14. Haven't tuned it yet but even with the previous one it wouldnt boost quite right the whole time, and that one had been tuned. Was curious if it could be my APC messing things up, or a bad intercooler or something of that sort.
Been looking into an 85 SPG and since we're discussing boost I'm looking for ways to increase HP and boost pressure without installing a new turbo.

rage
15-12-03, 12:11 PM
No no no ( :

Just by a vacuum tee that has three fittings on it. Run the hose to your new gauge, then one to the stock one. It's a 20 cent and 2 minute fix.

good luck,
Taylor

Thats what i have done, i had only disconnected the stock gauge temporarily to get the new one up and running. I have 2 gauges running now with a tee piece i bought from halfords yesterday afternoon strangely enough :roll:

I have a red box which i will be trying to adjust sometime in the near future. Is this actuator recommended?--> http://www.forgemotorsport.co.uk/products.asp?cat=TUNACT&product=FMAC900 Or is there anything else you would recommend?

tandino
15-12-03, 01:00 PM
The forge actuator is a nice piece of kit however mounting is a pain in the backside,
You have to cut the old actuator off its mounting plate and this proves rather tedious as its all one piece - after the actuator is removed and the remains of the mounting plate is tidied up from sharp edges you will have to drill two holes for the new actuator bolts - only problem is the hole left by removing the old actuator from the plate coincides where one of the holes wants to go - you will have to make up a plate to clamp the new actuator to the mounting plate.
Ask DaveB as i fitted his at Kodak - what should have been a 10 minute job turned into an hour one involving driving round trying to find a something to clamp it all together :o

Pete.

Johann F
16-12-03, 11:40 AM
My mod on the red box was to max out F to get the maximum boost setting of about 1/2 in the red and then play with the P to get the right rate of boost rise - the P setting is the important one as too much and you get boost overshoot and high torque loading ( bad for gearbox) and too little and the boost does not rise quickly enough to keep up with the revs( limits the total boost to less than set by F). Get the actuator sorted first though and make sure you have enough fueling - stock lucas will handle about 1bar of boost without mods but Bosch LH may need some help from a higher rated pressure regulator.

rage
16-12-03, 11:58 AM
Thanks for the advice guys. Mine has a 3bar fpr, that should be fine i hope. Which actuator are you guys running, seems the forge one is a pain to fit. Any recommendations or are they all the same to fit?

With regards to red box mods, i have heard you can check ohms with a multimeter. Do i go on the back of the pots themselves or is it on a couple of pins? Electrics never really were my thing :roll: Also, engine running or ignition on?

Johann F
16-12-03, 12:20 PM
There is no need if it's already a proper red box to measure anything- turn the F as far as it will go clockwise. Drill a couple of holes in the case above the F and P and you can adjust them on the car ( obviously requires a bit of dismantling in the first place to work out where to drill) Remember to seal the holes as well once you have set it.

Alex
17-12-03, 02:50 AM
I used to remove the top of the APC case, when adjusting the pots. Needs a very short screwdriver though to go between the inner wing panel and the APC.

Johann F
17-12-03, 03:51 AM
For the ultimate control - remove the P and F pots and run wires from the pin mounts through to the dash and fit adjustable pots with rotary knobs that you can set as you drive!

Matthew
17-12-03, 05:52 AM
Isn't that the setup Keith uses?

Alex
17-12-03, 07:41 AM
It is. His F pot is a 1kohm unit which allows the sustained boost to be raised :cheesy:

Dave B
18-12-03, 05:06 PM
Ask DaveB as i fitted his at Kodak - what should have been a 10 minute job turned into an hour one involving driving round trying to find a something to clamp it all together :o

Pete.

And I can't thank Pete enough for his help and determination in completing the job.

Which actuator are you guys running, seems the forge one is a pain to fit. Any recommendations or are they all the same to fit?

But its not actually a pain to fit, it was difficult because we didn't have the right tools for the job or even realise we were going to come across these problems in the first place! With the right tools it is a fairly easy job, I can talk from experience because I had to remove the actuator and re-fit a couple of times due to the rod being too short in the first place :roll:

Paul, if you go with the Forge actuator, and it is a lovely piece of kit, I will be happy to help you fit it or at least pm you what you will need etc. It is adjustable. Think you need a straight rod measuring 16cm, 10-12 psi actuator.

Dave

Alex
18-12-03, 05:37 PM
It is adjustable. Think you need a straight rod measuring 16cm, 10-12 psi actuator.

Are you sure you want your base boost set at 0.7-0.8bar?

Dave B
20-12-03, 06:41 AM
That was the spec advised by Pete and/or Simon. Is that setting not right then Alex? The car is standard, though I may APC tweak in the new year.

To be honest I haven't properly run the car since fitting but initial tests with a calibrated boost gauge showed it seemed to be about right, going up to just over 10psi on boost after I had the rod length amended by Forge so that it actually fitted correctly. I haven't tinkered yet.

tandino
20-12-03, 08:40 AM
I think youll find i recommended 7-8 psi :o

rage
22-12-03, 12:01 PM
Looks like i will go with the forge one then.

Today my boost has been varing, from 7psi up to 14psi. Is that the actuator playing up or could it be something else :-??

tandino
22-12-03, 12:18 PM
It really is difficult to say without seeeing the vehicle and checking everything over.
It could be 'ghost knock' due to sticky tappets for example due to lower temps and therefore oil taking longer to get to optimum viscosity.
One of my tappets on my engine is 'lazy' and takes anything from 1-15 minutes to shut up completely - sometimes it quitens down qucikly and other times you can occasionally hear it tick - this does have an effect on boost until it quietens down

rage
22-12-03, 01:35 PM
Fair comment Pete, looks like i will get the actuator and see if it does it then. That way it would eliminate it from the equasion. Like you say, could be any number of things.

Dave B
22-12-03, 04:51 PM
I think youll find i recommended 7-8 psi :o

What does that mean for me then if it is set at 10-12psi???

tandino
22-12-03, 04:57 PM
Apc wont be able to drop boost lower than base boost if knock is detected

Dave B
22-12-03, 04:59 PM
Thanks for the quick reply Pete, should I get it re-set to 7-8 psi then? (if that is possible).

And is it safe to drive (and you know what my driving is like!)

Alex
22-12-03, 05:44 PM
It really depends on whether you get a bad tank of petrol or really go for it away from the lights on a hot day after the IC has heat soaked for bit.

A T16 will normally run at 13psi without problems, its only if the APC needs to drop the boost that running the very stiff actuator will have any effect.

Standard base boost is 4-6psi.

john-w
22-12-03, 05:59 PM
If you put an upgraded actuator (say 12psi) on a car with an MBC, how do you set your base boost, as there is no APC to disconnect!

tandino
22-12-03, 11:05 PM
John,

Run the car without the MBC in line - ie run from the compressor outlet to the actuator.

Pete.

john-w
23-12-03, 01:31 AM
John,

Run the car without the MBC in line - ie run from the compressor outlet to the actuator.

Pete.

How will you know it is adjusted correctly(rod length?) I guess you will have to watch it open as you hit the psi rating of the actuator. Is this correct??

rage
17-01-04, 10:01 AM
I managed to get hold of a good standard actuator for a tenner and have fitted that this morning. Had to turn P down a bit cos i hit the fuel cut off. Now its set to 10-12 PSI and thats with normal unleaded. Hopefully it should be better when i fill her up with Optimax, shame its a 50 mile round trip to get some :roll:

Anyway its ready to be put back on the rollers next month. It certainly feels a lot quicker than it did this time yesterday.

pda
17-01-04, 10:59 AM
when i fill her up with Optimax, shame its a 50 mile round trip to get some :roll:

I only travel 1/4 of a mile for Optimax :cheesy: :cheesy:

you will have to take a gerry can for the return trip back home :wink: :wink:

Paul

Jezzadee
17-01-04, 02:50 PM
50 miles :o I thought I had it bad on a 27 mile round trip. There is a Shell on the B1150 (I think) going north just as you leave Norwich, but otherwise I can only think of Loddon. I've just moved house, now 7 miles to the nearest Optimax, and 79p - regular 95 is 82p where I was before :!