[General | Members | C900 | 9000 | NG900 & OG93 | 92X | 93 | 95 | NG95 | 97X | 99 | Sonett | Vintage Models | Performance | Detail | Clubs & SOC | Other Cars | Books Movies & Music | Chat | FAQs | Gifts | Photos | Classifieds | Polls | Raffle | Sponsors]

Saab Model 99 Bulletin Board
1969-1984
Search:

[Main Saab Model 99 Bulletin Board | Post Followup | FAQ ] [ Prev by Date ] [ Next by Date ] Member Login / Signup [Most Recently Edited Saabnet.com Photo Galleries]
4 things needed for good performance
Posted by Gary Stottler (more from Gary Stottler) on Mon, 18 Jun 2012 10:32:44
In Reply to: Re: 1978 99T Performance Issues, Pat, Sun, 17 Jun 2012 17:54:24
Pat,

Some good advice so far, here's another 2 cents (4, actually). Keep in mind that the 99T in US trim was rated at 135hp/160lb-ft torque. So, consider what you're comparing it to, what is "poor performance"? When new, the 99T was good for 9.5-10 second 0-60 time at best. A lot of 99Ts got "blow up" by folks trying to crank up the boost - the engine and fuel system have some limits beyond which expensive stuff starts breaking....

1) Base engine hardware: Since you have to pull the valve cover off to check the valve clearances anyway, check to make sure all the timing marks line up. Then check/set the valve clearance. Do a cylinder leakdown test preferrably, but at least a compression test. 20% leakdown likely means exhaust valve seat(s) worn.

2) Ignition timing: Check to make sure that both vacuum advance and centrifugal advance are working correctly. The distributors tend to sieze up over time which gives you "fixed advance" - you can set it perfectly and the engine will still run poorly because the timing's not varying when it should.

3) Fuel: Use a dwell tach hooked to the lamda service connector by the fuse panel to make sure that at a warm idle the lambda duty cycle is fluctuating between 30-70% or 40-60%. You should hear the idle "hunt" ever so slightly in tune with the fluctuating pulsewidth. Adjust the mixture using this measure and you don't need a CO meter. Then, make sure (as was pointed out) that the pulsewidth goes up to 80% and stays there when the throttle microswitch is closed (don't need to open the throttle, just reach over and click the switch). With the engine off you can make sure that the switch is being activated when the throttle actually gets near open.

4) Boost: The US cars were set to run 8 psi max on 87 octane fuel. (about the mark between red and yellow on the gauge - 3600 rpm steady wide open throttle in 3rd gear - ride the brake until it stabilizes). If your cooling system is real good and you run 93 octane fuel you can go 10 psi, but I would not go above that on a stock 99T motor unless you love doing valve jobs.

As was already suggested, you can get some additional power by running richer, but you would need to use an air/fuel ratio sensor to "tune" that along with the trick warm-up regulator, etc. 11.5:1 Air:Fuel ratio is plenty rich, more than that you are just spraying money in there and turning it to smoke.

If you decide to pull of the catalyst (which I don't recommend unless it's clogged) and find that it's physically intact, I'd be interested in having it. I have a used test pipe I'll trade if you want. But, assuming the catalyst is good, that is going to be a small performance change (probably take a stopwatch to tell the difference) compared to getting the rest of the system sorted.

Good Luck!

Gary


posted by 198.208.15...
Posts in this Thread:
Members can receive an alert when someone posts in this thread.
Post a Followup

Name:
E-Mail: (Confidential & Secure - Not revealed to other users!)
Send me email when someone posts in this thread: (available to Members)

Subject:

Posting rules are simple - No for sale/wanted ads or live auctions may be here - use the classifieds.
You may not cross-post your message to multiple BBs.
Personal attacks, insults, or flaming are not allowed.
Posting any of this will result in an immediate loss of posting privileges on this site.
Site Members do not see any warning (red) text.

Message:

Optional Link URL: (e.g. http://www.saabnet.com/)
To promote your own Saab site here, you must have a link back to The Saab Network.
Link Title:
Optional Image URL: (e.g. http://www.saabnet.com/img.jpg)


The content on this site may not be republished without permission. Copyright © 1988-2012 - The Saab Network - saabnet.com.
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 Donations
Your address is: 50.16.17.90 - Using CCBot/2.0 - Logged.
Site Members do not see red text instructions, green links, and bottom of the page banners.
Click here to see all the Site Membership Benefits!