Wife wanted her car to pop on decel like her old 1968 Chevelle. I changed the dfco values in the enable VSS to 45 and the disable VSS to 40 and got some results, but she wants more. Not sure what else is safe to change. Any help??
Wife wanted her car to pop on decel like her old 1968 Chevelle. I changed the dfco values in the enable VSS to 45 and the disable VSS to 40 and got some results, but she wants more. Not sure what else is safe to change. Any help??
While I have never purposely tried to achieve that, in tuning DFCO to try and Eliminate that during activation and deactivation these are some directional tips that you might try:
- If there is no fuel, there is nothing to create a "burble" - so first would probably leave DFCO disabled.
- Very low timing advance typically causes low combustion chamber pressure and late combustion in the exahust ports/headers/etc; maybe try to pull the timing very low during decel
- May have to play with the right combination of timing retard and fuel mixture - if youre closed loop that won't really be on the table, but in an open loop decel mode thats another parameter to fine-tune it with.
DISCLAIMER: Trying to achieve that sound is probably going to be directionally incorrect for engine durability - not sure to what extent, but if youre constantly driving around lifting off to make that happen things like the exhaust valves and catalytic converters (if there still present) may not be happy about it. Just be careful and make sure you are ONLY affecting things at very light/negative engine load and not too high of RPM - if youve never seen what happens to a car on a chassis dyno when the spark blows out at WOT and high RPM and the fuel finally ignites in the exhaust..... oval mufflers turn round
Thanks..I guess my question is what parameter in this control affects the adding of a wee bit more fuel at low loads. I know how to trim most of the fuel in spark in the later Ford stuff, but the 1999 to 2004 parameters are new territory for me. I am cautious by nature so I was hoping get some advice on specific areas to add fuel.Originally Posted by CaudleDynamicsLLC
While I have never purposely tried to achieve that, in tuning DFCO to try and Eliminate that during activation and deactivation these are some directional tips that you might try:
- If there is no fuel, there is nothing to create a "burble" - so first would probably leave DFCO disabled.
- Very low timing advance typically causes low combustion chamber pressure and late combustion in the exahust ports/headers/etc; maybe try to pull the timing very low during decel
- May have to play with the right combination of timing retard and fuel mixture - if youre closed loop that won't really be on the table, but in an open loop decel mode thats another parameter to fine-tune it with.
DISCLAIMER: Trying to achieve that sound is probably going to be directionally incorrect for engine durability - not sure to what extent, but if youre constantly driving around lifting off to make that happen things like the exhaust valves and catalytic converters (if there still present) may not be happy about it. Just be careful and make sure you are ONLY affecting things at very light/negative engine load and not too high of RPM - if you've never seen what happens to a car on a chassis dyno when the spark blows out at WOT and high RPM and the fuel finally ignites in the exhaust..... oval mufflers turn round
This vehicle is not her daily driver so a little the tuning is in play should not be a huge concern...But I totally understand your concern in the Disclaimer statement. Thanks again and let me know if you having any input on fuel paramiters.
I would first try to reduce the ignition timing significantly during coastdown - even with "normal" fuel mixtures, that will likely initiate the exhaust popping and by nature of much less efficient combustion, act richer anyway.
The number I see around tossed around is -10 at 2000 RPM and up blend vertically and horizontally in the very lowest load areas. I can try that and go in the plus direction if it is too much. Thanks for the hint....and your time!
I looked at the Open Loop decel load table...all the values are 0.00. To add a bit of fuel which way would you go, plus or minus. I just want a small change. Maybe suggest a baseline guess would be of great help...I can work from there.
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