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
MBCs and MBC+A etc
Like This Post: - Subscribe to Daily Digest for this Bulletin Board
Posted by Dean (more from Dean) on Fri, 16 Jan 2004 09:45:05 Share Post by Email
In Reply to: H20 injection results and MBC questions..., Tyler, Fri, 16 Jan 2004 09:03:51
Alert me when someone posts in this thread:
Members do not see ads below this line. - Help Keep This Site Online - Signup

It sounds like you have a ball-spring type MBC. If so...

These will over shoot. Thats part of the design. But there is a boost droop issue with some methods of connection that is not the fault of the MBC at all.

The boost overhsoot with this type of MBC is because the design opens late and cannot then flow fast enougth to pressurize the WGA and then open it. That can be overcome extremely well by connecting a air pressure regulator in parallel to the MBC to act as an anticipator. This termed a MBC+A. The anticipator applies a small regulated amount of pressure to the WGA before the MBC opens and starts to flow. When the MBC is ready to go it finds the WGA prepresurized and that makes the WGA respond without delay.

An boost regulator that is pressurized at the turbo compressor housing hose barb will create boost droop at the intake manifold or TB. It is regulating the pressure at the turbo. As the CFMs increase, the pressure drops across the IC and plumbing reduce the pressure at the TB. That can be overcome by moving the pressure tap for the MBC to the TB or intake manifold. That moves the control point. Now as the CFMs increase, the MBC will make the turbo work harder to overcome the pressure losses in the system. A MBC-A in this config will have greater overshoots as the length of the hose will induce time delays.

If you hook up a MBC+A, tapped at the TB or intake manifold, you will not have overhshoots and you will not have boost droop until you reach the flow limits of the turbo and IC.

Doing all of that will yield a very good result. There will still be some torque droop that you will see on the dyno. The IC gets heat soaked and you get hot air and less power. The water injection will help with that to some extent. And this is worse on a dyno as the vehicle has zip relative wind speed. The fans setup at a dyno do not compare speed on the road. So your power on the road will be greater than a dyno will show.

You need a 'non relief type' APR which regulates acturately at very low pressures. These APRs are easy to find and cheap, but their springs are too stiff. Jeff (Atl GA) swapped in a softer spring and it works very well for him. Search for anticipator and MBC+A on this and the 9-3BB.

posted by 66.139.123...
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!