PCM Diagnostics & Tuning HP Tuners | Holley | Diablo

Afterstart enrichment (choke)

Old Jul 21, 2008 | 09:01 PM
  #1  
02WS6FREEBIRD's Avatar
Thread Starter
Launching!
iTrader: (4)
 
Joined: Feb 2007
Posts: 221
Likes: 1
From: Central Florida
Default Afterstart enrichment (choke)

As a general rule when putting in a bigger cam do you need more or less afterstart enrichment or do the dynamics not change much and you dont really need to mess with that?
Reply
Old Jul 22, 2008 | 07:39 AM
  #2  
RickyMartinZ28's Avatar
TECH Fanatic
iTrader: (5)
 
Joined: May 2007
Posts: 1,374
Likes: 0
From: Tyler, Tx
Default

I'd like to know the same thing, my cold startup is awesome for about 3 seconds and then it idles really low. And warm startup is hesitant but once started its fine...

-Rick
Reply
Old Jul 22, 2008 | 09:11 AM
  #3  
BLK02WS6's Avatar
9 Second Club
iTrader: (2)
 
Joined: Jul 2002
Posts: 2,583
Likes: 1
From: on the dyno tuning in MD
Default

You don't really need to mess with afterstart enrichment...

The key to the dipping idle is to work on the startup airflow correction and startup friction airflow correction tables- add about 2gm/cyl to the correction tables, decrease the decay factors by about 50% and increase the delay by about 50%.

This gives it more air on startup and slows down the drop in air to reach the values in the running airflow tables. The slower transition allows the engine to catch its breath so to speak before dropping down to normal idle.

There are spark tables that can also help out if you are running a really big cam - you can narrow down the idle corrections so they don't swing so much trying to correct a fluctuating idle...
Reply
Old Jul 22, 2008 | 11:51 AM
  #4  
Frost's Avatar
FormerVendor
iTrader: (45)
 
Joined: Jul 2005
Posts: 5,913
Likes: 2
From: Richmond VA
Default

sometimes a low and weak idle before closed loop can also be a lean spot in the VE table
Reply
Old Jul 22, 2008 | 12:57 PM
  #5  
Haans249's Avatar
TECH Addict
iTrader: (24)
 
Joined: May 2005
Posts: 2,045
Likes: 4
From: Fort Worth, TX
Default

Originally Posted by Frost
sometimes a low and weak idle before closed loop can also be a lean spot in the VE table
I second that
Reply
Old Jul 22, 2008 | 02:51 PM
  #6  
jimmyblue's Avatar
Moderator
iTrader: (11)
 
Joined: Mar 2002
Posts: 12,604
Likes: 7
From: East Central Florida
Default

My car ended up way over-enriched after cam swap,
the higher MAP at idle will increase commanded fueling
underlying the afterstart, and low RPM VE always
needs work to not be bogus-high airflow, bogus-rich
fueling. Better to deal with the open loop fueling and
VE first before messing with the afterstart but I did
take a lot out of it, a bit at a time, as well as bumping
out the friction airflow & decay to make it more stable
immediately after catching.
Reply


Thread Tools
Search this Thread

All times are GMT -5. The time now is 03:39 AM.