El Salvador is know for its mild, rounded, smooth tactile mouthfeel. 

Medium body and low to medium acidity. 

The Coffee often range from Bourbon, Catuai, Pacamara or Pacs varieties. 

I will recommend to extract the coffee between 29-31 sec. with a long extraction time highlighting sweetness and smooth aftertaste. 

You can also try to brew it at 27-29 sec. But I find the body is more intense with a longer extraction time. 

Dose 21 g dobb shot
Extraction time 29-3 sec
Liguid mass 38 g.
Extraction rate  21/38= 0,55%

The dose is calculated using a 20g porta filter min. dose 19g/ max. dose 21 g. pr double espresso.