exhaust causing knock?

[truwarrior]

I have a EVOIII turbo at 20psi. Stock timing, 10.5:1 air fuel, HAHN FMIC.

At 6000 rpms I'm getting knock which is pulling 2 degrees of timing.

I'm wondering if my exhaust is the reason for this. I have a 2G manny, slightly ported housing on the EVOIII (took out the ridge for the fire ring), and a SBR 02 2G housing which was bridge ported. I'm wondering if I dump the o2 housing for a o2 dump if that might get rid of that knock.

 

[blackGSX2g]

The way I see it, the only way an exhaust will 'cause' knock is if it is loose and banging against the block getting picked up by the knock sensor.

A higher flowing exhaust system and poor wastegate flow can cause boost creep which will raise boost pressure to dangerous levels depending on your set-up.

I see you have a fuel pump and aftermarket injectors. Running those fuel mods you NEED something to control them (your profile doesn't say so, but update if you do). If you don't have any control, then you are dumping way too much fuel causing rich knock.

(hoping you have a wideband) I think an A/F of 10.5:1 is a on the rich side for your set-up unless you have high timing values or really crappy gas.

 

[truwarrior]

The way I see it, the only way an exhaust will 'cause' knock is if it is loose and banging against the block getting picked up by the knock sensor.

A higher flowing exhaust system and poor wastegate flow can cause boost creep which will raise boost pressure to dangerous levels depending on your set-up.

I see you have a fuel pump and aftermarket injectors. Running those fuel mods you NEED something to control them (your profile doesn't say so, but update if you do). If you don't have any control, then you are dumping way too much fuel causing rich knock.

(hoping you have a wideband) I think an A/F of 10.5:1 is a on the rich side for your set-up unless you have high timing values or really crappy gas.

Ya I have DSMLink. I guess I don't get why I'm knocking unless it's related to the bridged 02 housing. The two exhaust are just colliding togeather. Doesn't that hurt turbo efficiency?

Even though airflow per rev is dropping before the knock, total exhaust volume is more in the higher rpms then before the knock and drop in airflow per rev.

 

[Thomas91169]

thats not much knock. most guys will say anything over 3* of retard is bad.

but i used to have consistent 5*+ of knock across the whole board, and picked up a gm3bar map sensor to help me get my airflow tables good and dandy. that almost cured it, and knock wasnt any more than .5* and that was only for very quick bursts. maybe you should add that to your car as well.


maybe see about 5 points of airflow starting at 1600hz on up to 2400. see what that does.