PCM Diagnostics & Tuning HP Tuners | Holley | Diablo
Sponsored by:
Sponsored by:

Afterstart enrichment (choke)

Thread Tools
 
Search this Thread
 
Old 07-21-2008, 09:01 PM
  #1  
Launching!
Thread Starter
iTrader: (4)
 
02WS6FREEBIRD's Avatar
 
Join Date: Feb 2007
Location: Central Florida
Posts: 221
Likes: 0
Received 1 Like on 1 Post
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?
Old 07-22-2008, 07:39 AM
  #2  
TECH Fanatic
iTrader: (5)
 
RickyMartinZ28's Avatar
 
Join Date: May 2007
Location: Tyler, Tx
Posts: 1,377
Likes: 0
Received 0 Likes on 0 Posts
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
Old 07-22-2008, 09:11 AM
  #3  
9 Second Club
iTrader: (2)
 
BLK02WS6's Avatar
 
Join Date: Jul 2002
Location: on the dyno tuning in MD
Posts: 2,583
Likes: 0
Received 1 Like on 1 Post

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...
Old 07-22-2008, 11:51 AM
  #4  
FormerVendor
iTrader: (45)
 
Frost's Avatar
 
Join Date: Jul 2005
Location: Richmond VA
Posts: 5,913
Likes: 0
Received 2 Likes on 2 Posts
Default

sometimes a low and weak idle before closed loop can also be a lean spot in the VE table
Old 07-22-2008, 12:57 PM
  #5  
TECH Addict
iTrader: (24)
 
Haans249's Avatar
 
Join Date: May 2005
Location: Fort Worth, TX
Posts: 2,045
Received 4 Likes on 4 Posts

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
Old 07-22-2008, 02:51 PM
  #6  
Moderator
iTrader: (11)
 
jimmyblue's Avatar
 
Join Date: Mar 2002
Location: East Central Florida
Posts: 12,605
Likes: 0
Received 6 Likes on 6 Posts

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.



Quick Reply: Afterstart enrichment (choke)



All times are GMT -5. The time now is 06:06 AM.