Site News - 6/4: Advertising Position/Commission Available | 5/10: Members: Log In to See Fewer Ads!
[General | Members | C900 | 9000 | NG900 & OG93 | 93 | 95 | NG95 | 99 | Sonett | Vintage Models | Clubs | Other Cars | FAQs | Gifts | Member Photo Galleries | Member Directory | Classifieds | Manuals | *Buddy Registry | *Mileage Registry | Polls | What's New | Raffle | Photo of the Month | Sponsors]

C900 Bulletin Board
1979-1993 & 94 Conv [Subscribe to Daily Digest]
(Search Author's Posts: e.g. Keyword:username)*Members Only

[Main C900 Bulletin Board | BBFAQ | Prev by Date | Post Followup ] Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos
Re: Base Boost @ 9.5 PSI...Is she going to blow????
Like This Post: - Subscribe to Daily Digest for this Bulletin Board
Posted by gorper (more from gorper) on Thu, 14 Aug 2003 22:09:57 Share Post by Email
In Reply to: Base Boost @ 9.5 PSI...Is she going to blow????, scottgf, Thu, 14 Aug 2003 20:22:57
Alert me when someone posts in this thread:
Members do not see ads below this line. - Help Keep This Site Online - Signup

Hello,
I am a Saab newbie and a few days ago I posted a message regarding adjusting the waste gate on my 87 SPG.

-->welcome...

I received some great tips on measuring the "Base Boost", so I connected a vac guage , un plugged the apc soil. and went for a test drive and the vac. guage was reading 9.5 psi while the dash "boost" guage when showing just slightly into the red.
I must say the car seems to be running great for a car with over 100k miles, lots of power, the boost seems to come on really nice, not a neck snapping thing, but pulling pretty hard (BTW I know neck snapping, see sig. below), I dont notice anykind of "fuel shut-off" or anything happening.

-->100k is nearly new for these cars; motors are quite stout.

I suppose you all are going to tell me to back off the boost by making the waste gate rod longer. (say it aint so).

-->the APC is designed to keep the motor from dying of too much knock; base boost is the lowest pressure the APC can drop boost in the event of severe knocking. so if you are at max boost, which is prolly only several psi above 9.5, and the APC detects knock, then opens wastegate to vent psi but continues to detect knock even at 9.5, then the APC can vent no more pressure, at which point you could toast the motor. now, having said that, i have never seen my APC drop boost all the way to base boost. the advantage of running a high base boost is it keeps the wastegate from cracking open and venting some pressure. this makes spool-up quicker. but 9.5psi is overkill; you may as well not have APC.

Also the apc soil. seems to be working, it clicks when i unplug and plug it in and when I turn on the ignition, it also will go "clickety click click while idling sometimes.

Before I started all these adjustments the car just didnt seem to have much pickup and the "boost" guage only went halfway into the yellow.
Am I expecting too much from a 2 (something) liter 4 banger?
Opinions please ...
Cheers,
Scott
87 SPG
94 Viper (neck snapper)
73 Road Runner (kinda neck snapper)
63 VW (not neck snapper)



Here's what I would do if I just purchased a used SPG:

Get a Bentley Publishers Saab 16v manual

Full tune-up:

NGK plugs
Bougicord wires
Bosch cap/rotor
Bosch fuel filter
yer favorite air filter

confirm timing is at 16* btdc with vac. hose to distributor removed/plugged.

clean all ground wires: on top of motor where intake/head meet, down in front by radiator/battery, etc. also clean positive distribution block terminal (pass. side @ fender; black plastic).

Replace all underhood vacuum lines -- these age and crack over time and are a pain to troubleshoot when searching for vacuum leaks. Some advocate silicone; rubber is fine. you need about 15' of 3.5mm ID line (or next SMALLER English ID); skip the APC solenoid lines unless they look beat.

Replace the rubber grommets in the intake manifold that hold the vac. line nipples in place; they age and leak boost. also replace the grommet on the valve cover breather. clean the one-way valve (white, plastic). Replace if cracked or nasty looking. for good measure, strap some zipties around all of these nipples to keep them in place under boost. your manifold should be *dry* on the outside; no petroleum goop on it, which indicates leaks.

next, carefully inspect the turbo plumbing for cracks. remove the intercooler and clean it out with a solvent; oil from valve cover breather fills up in there. rinse out 'til clean. be responsible with disposal :-). refit everything, taking care to ensure that the clamps are seated properly and are good & tight.

find the turbo bypass valve (up front, hidden beneath some plumbing; see bentley). this bit is prone to giving out and leaking boost. remove vac. line to the valve, blow hard into it (should not leak) and then suck hard on it (should hold vacuum). if not, replace it.

okay, now you should have a good, tight motor. Set your base boost for 7 psi (this is higher than stock). Go for a ride and see how she does.

other stuff:

for better off-boost performance, remove vacuum/advance capsule, bend small round for more total timing. search "brad's aid" on the performance board.

tweak your APC; search "tweak" on the performance board. or, here's the specs:

Bypass R42 - Replace R138 with 40Kohm
Replace R40 with 1,3Kohm OR Replace F-pot with 1Kohm linear pot OR Install 300 ohm resistor in parallel with pressure transducer.
Adjust F & P to taste, P for boost rise rate, F for high RPM boost pressure

search "pots" on performance board for more info.

this should get you started...

posted by 63.225.176...
Posts in this Thread:
Alert me when someone posts in this thread:
Members do not see ads below this line. - Help Keep This Site Online - Signup
Post a Followup

No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.

Name: Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos
E-Mail: (Optional)
Re-Enter E-Mail: (Confidential & Secure - Not revealed to other users!)
Note: Please check your spam folder for BB responses.

Subject:

Posting rules are simple - No for sale/wanted ads may be posted here - use the site classifieds.
You may not cross-post your message to multiple BBs.
Not permitted: political/religious topics and being disrespectful (personal attacks, insults, etc...).
 Site Members do not see any red text, inline ad links, bottom of page anchor ads, box ads, or anti-spam check.

Message: (please no for sale/wanted classifieds - post those in the Saabnet.com Classifieds)
Links are now automatically made active, no need for any special code (or use the Option Link field below) - don't put links in () or end with a '.'
To add inline images to your post, use [img]http://www.domain.com/img.jpg[endimg] (or use the Optional Image Link field below).

Links are now automatically made active, no need for any special code (or use the Option Link field below) - don't put links in () or end with a '.'
To add inline images to your post above, use [img]http://www.domain.com/img.jpg[endimg] (or use the Optional Image Link field below).
Optional Link: (e.g. http://www.saabnet.com/)
Link Title: (Optional)
Optional Photo/Image Link: (e.g. http://www.saabnet.com/img.jpg)
Photo/Image to Upload: (Please be patient while file uploads)



StateOfNine.com
SaabClub.com
Jak Stoll Performance
M Car Covers
Ad Available

The content on this site may not be republished without permission. Copyright © 1988-2025 - The Saab Network - saabnet.com.
For usage guidelines, see the Mission & Privacy Notice.
[Contact | Site Map | Saabnet.com on Facebook | Saabnet.com on Twitter | Shop Amazon via TSN | Site Donations]

Random Saabnet.com Member Gallery Photos (Click Image)
This is a moderated bulletin board - Posting is a privilege, not a right. Unsolicited commercial postings are not allowed (no spam). Please, no For Sale or Wanted postings, SERIOUSLY. Classifieds are to be listed in The Saab Network Classifieds pages. This is a problem solving forum for over 250,000 Saab owners, so expect to see problems discussed here even though our cars are generally very reliable. This is not an anything goes type of forum. Saabnet.com has been a moderated forum since 1988. For usage guidelines, see the Saabnet.com Mission and Purpose Page. Please remember that you are not anonymous. Site Contact | Site Donations | Other Sites by SP - Poverty2Prosperity.org | Run Club Menlo Park | ScreenBot


Site Members do not see red text instructions, bottom of the page anchor ads, or box ads.
Click here to see all the Site Membership Benefits!