i have been using the vafc hack for months already. i haven't experience part throttle detonation nor the jerking problem yet.

i'm fully aware that the hack advances the ignition timing so my question is, does the advancing of ignition timing also applies during IDLING?

i'm asking this question because whenever i accelerate from 1st gear, whether the A/C is ON or not, i could hear the engine knocking. this sometimes happen in 2nd gear also at low speed. i had to ease up on the gas pedal whenever i hear the knock then step on it again hence i can't do quick acceleration from a stop. this knocking is more severe when the A/C is turned ON. could it be the hack? or is it the weather? or clutch? it's annoying already.

thanks for any help.

 

did you lower your base timing?? at idle yur fine but you need to lower your base timing so that when you do go in boost its not advancing so much....or get something to pull timing as you go into boost...other than that you have some problems because knock you can hear is baaaad!!! I had partial throttle knock but i use ecu program to pull timing when in boost and use afc for fuel....works wonderfully

 

before getting it dyno tuned, i used a jacobs boost master to lower timing without boost and timing with boost. when i had it dyno tuned, the tuner turn the timing without boost to zero but i don't know if he lowered my base timing.

now, i lower the timing again with the boost master but still experiencing knock during acceleration from stop when the car is moving already up to it reaches boost i don't hear any knock anymore.

 

what kind of fuel setup are you using?? not enough fuel plays a big time roll....or maybe your not pulling enough timing, i pull about 1 degree per lb. of boost.....you dont have to lower your base timing if your using something to pull timing, i actually run about 20-22 base timing and im not knocking at 10psi

 

i'm just using the vafc and 450cc injectors. for fuel i use the highest octane from where i live which is 96RON.


the timing is retarded 1deg per psi of boost already and i'm just boosting 7psi. if it were fuel related, wouldn't it knock/detonate at higher rpm? mine only knocks during acceleration from stop, once the car move or in boost there's no knock anymore nor detonation. i'm confused.

 

yea that is weird....your absolutly right, you sure its coming internally from the motor...not something that is vibrating under the hood that sounds like it, i had a heat shield i made for my hood and it vibrated at low rpms and rattled like detonation I took it off and it went away....maybe something is loose and vibrating?

 

Most likely something vibrating.

Anyways, IÂ’ve noticed motors like to detonate more at lower rpm's. I will typically knock more with 20 psi at 3000rpm's than 25 psi at 6000rpm's. The reason is that the longer the a/f charge spends in the cylinder the more time it has to absorb heat and thus "detonate" or if its a really bad day for you preignite. When the a/f charge burns shortly after entering the cylinder it has almost no time to endothermically take on heat and thus never truly reaches the self-combustibility temperature before the spark plug starts the party. And even when the spark plug does start the party, the charge isn't so hot that it becomes volatile. When a charge burns smooth its a great thing. When a charge explodes uncontrollably (detonation) stuff breaks. When the charge explodes when the piston is still on the compression stroke (preignition) you break stuff and your motor gets really pissed.

Now if I could only find a cost effective way to limit boost to something below 20 psi I'd easily be able to make more power. Damm MHI internal gates!