Site News - 7/11: No New News Today | 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]

Performance Bulletin Board
[Subscribe to Daily Digest]
(Search Author's Posts: e.g. Keyword:username)*Members Only

[Main Performance Bulletin Board | BBFAQ | Prev by Date | Next by Date | Post Followup ] Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos
Re: Forge BPV tuning question
Like This Post: - Subscribe to Daily Digest for this Bulletin Board
Posted by Eiron [Email] (more from Eiron) on Thu, 11 Mar 2004 07:18:19 Share Post by Email
In Reply to: Forge BPV tuning question, RobInfo, Thu, 11 Mar 2004 04:00:28
Alert me when someone posts in this thread:
Members do not see ads below this line. - Help Keep This Site Online - Signup

Jeff's on the money, & you're right about what happens when you swap in a stiffer spring. If you look at the comparison data I've linked below, you can see that re-orienting the valve so that pressure comes into the bottom port provides a better seal than with pressure coming in to the side port.

For my '99 9³SE auto (185hp), I get great results with the green spring by simply re-orienting the valve. Jeff's got higher boost going on that I do, so he's got the stronger blue spring. He did the right thing (IMO) by running it in the stock orientation first, & seeing if it met his needs. Since he was still getting some leak, re-orienting solved the problem.

You're correct that there's no direct effect on engine performance. What it does do is impact the turbo's performance, which translates into better or worse response. You want the spring force as light as possible to allow completely free spinning of the impeller between shifts, but you also want it strong enough to eliminate your boost leaks.

As a side note, Forge recommends that all their valves should be run with pressure to the bottom port. When I asked why, they said the piston "prefers" to run in-line with boost pressure rather than perpendicular to it. I was a little skeptical at first, since Saab's engineers obviously wanted the valve in the other position. (Bosch told me to ask Saab, & Saab wouldn't give me any answers.) But with a near-stock engine & the lightest DV spring possible, I get better response from the valve & better protection for the turbo. Jeff's experience shows the stiffer spring is just as safe (another concern of mine, since I couldn't duplicate his output on my engine) with his higher level of performance.

posted by 64.207.44...

DV Comparison Data

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!