Technical Timing question

CarMichael Angelo

clearly, I’ve got something going on in that hole
SN Certified Technician
Nov 29, 1999
12,517
13,644
234
62
Birmingham, al
m.imdb.com
Like it says, Does anybody know what the computer adds (if any) to the initial timing at start up? And on a hot restart? All in at whatever RPM total?

I have the ability to build a timing curve w/ the MSD timing computer I use on my carb'd 2V 4.6, and I still get a hot start backfire,... alot.

Currently, I'm running 22* initial at start through idle and a total of 32*, all in by 2000 RPM.
 
  • Sponsors(?)


nyuk98gt

15 Year Member
Oct 10, 2000
1,427
6
79
Chesterfield, MO
madmike1157:

Well, Sir, there are many, many modifiers to spark. Depending on the model year, there could be 3 tables (MBT, borderline knock, and max allowed). Coolant and inlet air are obvious modifiers. There is a maximum spark allowed for start-up, too. I don't know if it is used just for cranking or for the first little while until the engine goes into closed loop. If you can datalog, you can see the final spark commanded. This doesn't answer your question finally but it gives you something to investigate. Do you have access to a datalogger (XCal and a laptop), or equal?

Chris
 

wmburns

SN Certified Technician
Aug 14, 2009
5,807
499
164
Houston Texas
One of the causes of back fire is timing too far advanced. 22 degrees seems like a lot of start up timing.
 

CarMichael Angelo

clearly, I’ve got something going on in that hole
SN Certified Technician
Nov 29, 1999
12,517
13,644
234
62
Birmingham, al
m.imdb.com
Again, I am using an aftermarket MSD computer to handle timing chores. I believe that there isn't enough timing. Every "Race car" I've ever had was set to static timing and the curve was locked. Typically there was anywhere between 32 and 36 degrees at the crank upon start up, and the side effect was a hard crank, NOT a back fire, if there was too much timing on a hot start. ( to which the remedy was to retard it 2-10 degrees to alleviate that)

I just wanted to know if anybody knew what the factory ECU did to the timing as soon as the key was turned, and where the timing typically was on a cold/hot start if different. to include total timing at whatever RPM the computer determined to bring in full advance.
 

midnightdriver

Active Member
Jan 3, 2010
443
1
27
Northern California
Again, I am using an aftermarket MSD computer to handle timing chores. I believe that there isn't enough timing. Every "Race car" I've ever had was set to static timing and the curve was locked. Typically there was anywhere between 32 and 36 degrees at the crank upon start up, and the side effect was a hard crank, NOT a back fire, if there was too much timing on a hot start. ( to which the remedy was to retard it 2-10 degrees to alleviate that)

I just wanted to know if anybody knew what the factory ECU did to the timing as soon as the key was turned, and where the timing typically was on a cold/hot start if different. to include total timing at whatever RPM the computer determined to bring in full advance.

Stock 4.6 ECU base timing is 10* and around 20-24* total IIRC.
 

wmburns

SN Certified Technician
Aug 14, 2009
5,807
499
164
Houston Texas
Ok, I used my ODB2 scanner on my 2003 GT. Key on, engine not runnning, timing 10 degrees. As soon as it is cranked, the timing goes to zero.

Once started and at idle, the timing is between 20-24 degrees (motor hot).

At 2000 RPM's (motor hot), the timing is 40 degrees. I did not rev any higher as my 2003 is an automatic. I was afraid the PCM would sense the "neutral" and exessive RPM's and begin to pull timing.

The outside temperature at the time was 70 degrees.

I did not run the tests with the motor cold.
 

nyuk98gt

15 Year Member
Oct 10, 2000
1,427
6
79
Chesterfield, MO
madmike1157:

In my calibration (SXA2 for a '98 GT with an automatic), there is "maximum allowed spark table cold starts" and the values in the table range from 25 degrees at minus 30 F to 20 degrees at +30 F to 15 degrees at 196 F. I don't know if these are changed by the coolant temperature and air temperature and open loop A/F modifiers at start-up or if the modifiers only apply when the engine exits 'start-up'.

Anyway, I hope this is useful info for you.

Chris
 
Thread starter Similar threads Forum Replies Date
L Need Technical advice Fox 5.0 Mustang Tech 34
Bronx_whiskey_inNC Technical question about engine temp 1996 - 2004 SN95 Mustang -General/Talk- 3
CobraVert01 I’m not technically new.. but The Welcome Wagon 13
M Welp, One Of My Spark Plugs Hole Is Stripped.anybody Had A Similar Situation That Could Help? 2005 - 2009 Specific Tech 5
D Antenna Base Threads 2005 - 2014 S-197 Mustang -General/Talk- 2
Robert Arco Technical Question On 2008 4.6l 3v Heads 2005 - 2009 Specific Tech 8
Noobz347 Administrative Questions Requiring An "opinion" Are Not Technical Questions Fox 5.0 Mustang Tech 1
A Whistling/ Kettle Noise SN95 4.6L Mustang Tech 2
rustange Technical Help Needed SN95 4.6L Mustang Tech 3
stangmaster22 SOLD Not Technically A Mustang, But Close. Show Driver 68 Cougar V8 Manual Trans Classic Mustangs For Sale 2
FastDriver Progress Thread Technical Thread/how-to Index Fox 5.0 Mustang Tech 11
Tartar22 Location of Technical Service Bulletins 2005 - 2009 Specific Tech 3
VibrantRedGT Technical Thread / How To's 1994 - 1995 Specific Tech 0
FoMoCo17 Fusible Link Wire - Technical help please! Fox 5.0 Mustang Tech 9
C New! Not technically a mustang... The Welcome Wagon 4
Mr. Rustypwnz technical debate 1996 - 2004 SN95 Mustang -General/Talk- 14
MRaburn 1996-2004 Ford Mustang Technical Service Bulletins StangNet Site News 0
P Random Technical Questions Thread Classic Mustang Specific Tech 2
MRaburn Ford technical evolution sparks Revolution StangNet Site News 0
T I have a few technical questions..... 2010 - 2014 Specific Tech 7
MyEarsHurt PI Swap AND Forced Induction - Need legitimate technical advice SN95 4.6L Mustang Tech 12
vladasap some technical head re-install q's 1994 - 1995 Specific Tech 14
jtfairlane Rocker Arm Technical Help Fox 5.0 Mustang Tech 6
FoxRod87 Need technical wiring help! 96 GT SN95 4.6L Mustang Tech 6
BlownFiveLiter Technical Thread/How-To Index 1994 - 1995 Specific Tech 0
SpartaPerformance C&L Intake manifold. Technical article but VERY informative. 2005 - 2009 Specific Tech 8
fastgtfairlane technical difficulties posting pics 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 6
sohcman Technical Details For 7.5" T-LOK Install 2005 - 2014 Specific V6 Tech 8
forum155pl 3 very technical websites 1996 - 2004 SN95 Mustang -General/Talk- 4
T Technical Comment on Spark Plugs SN95 4.6L Mustang Tech 11
Y Roush Technical Question: Series I Plenum.. port or junk? Special Production 2
C Need some opinions (of the technical type) on my setup and options Fox 5.0 Mustang Tech 5
timeless2 1996 through 2004 Technical Service Bulletins SN95 4.6L Mustang Tech 11
Sanctus Dyno Consistency Technical Question 2005 - 2009 Specific Tech 7
bigcat S197 Technical Service Bulletins 2005 - 2014 Specific V6 Tech 7
bigcat S197 Technical Service Bulletins (TSBs) 2005 - 2009 Specific Tech 21
V When would i technically need to switch to 3" exhaust...please help? Fox 5.0 Mustang Tech 8
S Need help with technical terms?? SN95 4.6L Mustang Tech 8
D Technical Thread Index Fox 5.0 Mustang Tech 2
reenmachine Want a laugh? "Expert" technical engine article... Classic Mustang Specific Tech 33
Cupid Good Technical Manual Classic Mustang Specific Tech 7
bigwingsaleen Roush technical question... Special Production 4
RedDaemon technicalities regarding plugs... SN95 4.6L Mustang Tech 11
03REDFIRE TECHNICAL ELECTRICAL 1994 - 1995 Specific Tech 3
tylers65 Technical Write Ups 2005 - 2014 Specific V6 Tech 19
F Technical Assistance Needed SN95 4.6L Mustang Tech 2
menasci Technical Serivce Bulletins (TSP's) !!! SN95 4.6L Mustang Tech 9
balderman Technical Question 1994 - 1995 Specific Tech 0
M A few technical questions SN95 V6 Mustang Tech 2
UnderPressureGT Dyno numbers are in.. Technical help needed!! Fox 5.0 Mustang Tech 20
Similar threads