What causes surging when slowing down?
What causes surging when slowing down? When I slow down to a stop I get some decent surging. The surging stops as soon as I get below a certain MPH(assuming It changes over to idle characteristics). Any ideas? Is it still the RAF?
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Originally Posted by 99whitews6
When I slow down to a stop I get some decent surging. The surging stops as soon as I get below a certain MPH(assuming It changes over to idle characteristics). Any ideas? Is it still the RAF?
If surge occurs below Throttle cracker Disable MPH and zero mph then maybe RAF (LTIT could be contributing factor also...as Base Idle airflow). Scan it.
Originally Posted by Bink
Idle routines start at zero MPH and after a time delay.
If surge occurs below Throttle cracker Disable MPH and zero mph then maybe RAF (LTIT could be contributing factor also...as Base Idle airflow). Scan it.
If surge occurs below Throttle cracker Disable MPH and zero mph then maybe RAF (LTIT could be contributing factor also...as Base Idle airflow). Scan it.
Try checking all of your throttle cracker and follower airflow and decay tables...those will square you away =D You should set all the multipliers to 1.0, so then you can fine tune the airflow tables easier without having to worry about the stupid multiplier.
Best Regards,
Adrian
Best Regards,
Adrian
Originally Posted by Haans249
Try checking all of your throttle cracker and follower airflow and decay tables...those will square you away =D You should set all the multipliers to 1.0, so then you can fine tune the airflow tables easier without having to worry about the stupid multiplier.
Best Regards,
Adrian
Best Regards,
Adrian
Throttle cracker crap makes my car do it. I tried tuning the throttle cracker, to no avail.
Finally, I just disabled it under 10mph, and decreased it by 10% above 10mph.
It hunts a little now, until I get below 10mph, then it's perfect.
One time, I even disabled it completely under 30mph. Most of the time, it'd find idle perfectly, but some times, the rpms would drop too fast, and it would dip to 400rpm, so that didn't work either.
Honestly, I just gave up after I got it close.
Finally, I just disabled it under 10mph, and decreased it by 10% above 10mph.
It hunts a little now, until I get below 10mph, then it's perfect.
One time, I even disabled it completely under 30mph. Most of the time, it'd find idle perfectly, but some times, the rpms would drop too fast, and it would dip to 400rpm, so that didn't work either.
Honestly, I just gave up after I got it close.
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If your tps is below 1 then you are in the idle in gear spark table. I had a surge after the h/c/i . Like around 45, 35 coasting- I would get a bucking, surging. Logged the spark, tried cracker, follower to no avail. Looking at the idle in gear spark revealed it switching back and forth between cells (.12, .13g) that would not be used with the stock h/c. I just smoothed out the cells in the surging areas.
Originally Posted by Doc
If your tps is below 1 then you are in the idle in gear spark table. I had a surge after the h/c/i . Like around 45, 35 coasting- I would get a bucking, surging. Logged the spark, tried cracker, follower to no avail. Looking at the idle in gear spark revealed it switching back and forth between cells (.12, .13g) that would not be used with the stock h/c. I just smoothed out the cells in the surging areas.
That is a good suggestion, check your base idle spark tables, and adjust your base spark timing (under 2000 rpm range) and see if it needs to go up or down. My particular setup was extremely sensitive to idle spark changes, going from 21-23 made my car stall on start up. So, I would suggest starting with 5 degree increments at first to see if you need to go up or down, then start from where you were before and go +/- by 1 to .5 degree until it settles down.
best Regards,
Adrian
Originally Posted by Haans249
That is a good suggestion, check your base idle spark tables, and adjust your base spark timing (under 2000 rpm range) and see if it needs to go up or down. My particular setup was extremely sensitive to idle spark changes, going from 21-23 made my car stall on start up. So, I would suggest starting with 5 degree increments at first to see if you need to go up or down, then start from where you were before and go +/- by 1 to .5 degree until it settles down.
best Regards,
Adrian
best Regards,
Adrian
Thanks
Log Cylinder air and spark adv. During the deacceleration periods I could see a squiggle spark adv. as the cyl air was "strattling" some rpm vs. cyl air cells. For example at say 12-1300 rpm btw .10-.12 air there are no specific cells for the pcm to go to so it just goes back and forth btwn 12 and 1400 rpm in which the table went from 28* to 35* thus the bucking on deaccle. As soon as you go above 1%tps you go back to the H.O. spark table. Look at those "hard transition" areas and smooth them out. The pcm will only do what it is told.
Originally Posted by Doc
Log Cylinder air and spark adv. During the deacceleration periods I could see a squiggle spark adv. as the cyl air was "strattling" some rpm vs. cyl air cells. For example at say 12-1300 rpm btw .10-.12 air there are no specific cells for the pcm to go to so it just goes back and forth btwn 12 and 1400 rpm in which the table went from 28* to 35* thus the bucking on deaccle. As soon as you go above 1%tps you go back to the H.O. spark table. Look at those "hard transition" areas and smooth them out. The pcm will only do what it is told.
Thanks
Originally Posted by 99whitews6
Sounds good. I am still using same timing values for both high and low octane tables. Will this screw anything up if I leave it this way?
Thanks
Thanks
Originally Posted by GuitsBoy
You wont hurt anything, but you really should be running more timing unless you have a tiny cam in that motor. A bigger cam with more overlap will have a sloppy charge that wont burn as rapidly, so you run a little more timing down low to compensate. I dont know about big cubes, but for my cam and most others in the mid 23x range, they like around 28* timing at idle, and up from there. Your compression also plays a role in this.
Originally Posted by GuitsBoy
You wont hurt anything, but you really should be running more timing unless you have a tiny cam in that motor. A bigger cam with more overlap will have a sloppy charge that wont burn as rapidly, so you run a little more timing down low to compensate. I dont know about big cubes, but for my cam and most others in the mid 23x range, they like around 28* timing at idle, and up from there. Your compression also plays a role in this.
Last edited by SSpdDmon; Apr 26, 2006 at 01:02 PM.
Originally Posted by SSpdDmon
Any chance you can post your high octane, base spark (park/neutral) and base spark (in gear) timing tables? I've got 2 friends that just went with TSP torquers ('99 and '00 f-bodies - so thier spark tables are a little different than what I'm used to seeing) and would like to see where you've got your numbers.
I have to warn you that these tables are very conservative since im tracking down some low rpm KR that might be false. Im also running 10.9:1 compression (8.25 DCR) on 93 octane. Im currently running in open loop - MAF mode. Still not completely away from the low rpm bucking though.
