Re: Plug gap, timing, and boost, Oh my! (long) - Saab 900 Bulletin Board - Saabnet.com
The banner above is an advertisment - if it asks you to download software, please ignore.
Site News -
4/9 Saab Owners' Convention Day Pass Raffle |
3/26 M Car Covers (by State of Nine)
[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]
[Main C900 Bulletin Board | BBFAQ |
Prev by Date | Next by Date | Post Followup ]
Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos
Re: Plug gap, timing, and boost, Oh my! (long)
Posted by Simon S (more from Simon S) on Fri, 14 Apr 2017 11:09:54
In Reply to: Plug gap, timing, and boost, Oh my! (long), steven W, Fri, 14 Apr 2017 05:24:54
Members do not see ads below this line. - Help Keep This Site Online - Signup
You're learning about ignition compromises and "tuning". It's an interesting exercise in physics IMHO. The basic variables are cylinder pressure and voltage. The wider gap literally raises the spark voltage, makes a later hotter spark, but one thats more delicate: closer to not being able to happen at all. When the pressures raise or the voltage drops, the spark goes out. Higher RPM raises the current requirement proportionally, and thus lowers the spark voltage because the coil can't charge itself fast enough.
Scene 1: Wide gap, factory timing. This is essentially a retarded timing, probably misfiring because of the wide gap, not preigniting.
Scene 2: Wide gap, further retarded timing: makes the more delicate spark stable, but produced heat more than power.
Scene 3: Factory gap, retarded timing: essentially this is a tune for high boost. Again, trend is towards heat not power.
Scene 4: Factory gap, factory timing: APC limits boost to keep engine from pinging. Maximum performance is obtained from the fuel and atmospheric conditions available (within static timing limitations anyway)
Decreasing the gap improves spark quality under high ambient temperatures and high boost and high rpm, because it lowers the minimum-voltage requirement to strike a spark!
The optimal setting for factory hardware really is basically the factory spec, and premium gas, maybe slightly advanced like 18-BTDC instead of 16.
This starts the rabbit hole of tuning old technology - the timing control of this car consists of a vacuum bottle that retards timing a little at slight boost. The next bandaid is the MSD Boost Timing Master, which allows you to retard timing based on boost, so you can run more advanced timing off boost…but pretty soon you’ll realize it’s cheaper to update to Trionic 5. You also have a delicate gearbox, don’t push it, but thats just my .02.
posted by 76.105.241...
Posts in this Thread:
- Plug gap, timing, and boost, Oh my! (long), steven W, Fri, 14 Apr 2017 05:24:54
- Plug gap, timing, and boost, Oh my! (long), SWEDISHDYNAMICS, Fri, 14 Apr 2017 13:27:561
- Re: Plug gap, timing, and boost, Oh my! (long), Simon S, Fri, 14 Apr 2017 11:09:54 <-- Viewing This Message
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.
- Prev by Date:
Plug gap, timing, and boost, Oh my! (long), steven W, Fri, 14 Apr 2017 05:24:54
- Next by Date:
Plug gap, timing, and boost, Oh my! (long), SWEDISHDYNAMICS, Fri, 14 Apr 2017 13:27:56
- Main C900 Bulletin Board
StateOfNine.com
|
SaabClub.com
|
Jak Stoll Performance
|
M Car Covers
|
Ad Available
|
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!