Well since the introduction of the I-vtec motor it has been harder for you to notice or hear the vtec kick in... unlike other honda motors the ivtec utilizes vtec on only the intake cam. which can account for whyu wouldnt hear it as much

 

OK... some corrections

Every new Honda has i-VTEC, or intelligent VTEC. Basically it's a lower cam profile that allows for higher efficiency at a lower RPM (during acceleration and constant speed cruising), so better fuel economy.

Civic DX/LX/EX sedan or coupe have a R series motor (USDM R18, 140HP, 128 lb-ft), SOHC, 1.8L, 5 speed MT, or 5 speed AT.

Civic Si sedan or coupe have a K series motor (USDM K20Z3, 197HP, 139 lb-ft), DOHC, 2.0L
Other features of the Si, 6 speed manual, Helical LSD.

Think of it as D series of the EX v B series of the Si in the 6th generation

 

Gotchya but to be clear,I had said that I've seen VTEC on various motor photos on line,not side stickers.I figure they were obviously promoting the sale of their vehicles by way of showing off the VTEC motor status.these were NOT Si's.I don't know if they were EX's or what.

 

correction. Only Si have k20 motor and the rest of Honda R Series Engines

 

Theres different size engines, the d series has vtec but its only one cam. The B series has vtec too but it has two cams making it a lot faster