Quote:
Originally Posted by arghx7
I spoke to an industry person who is an expert on such matters as this, a person I greatly respect whose knowledge exceeds my own. He in essence agrees with Dimman:
It's not so much a "torque dip" as it is a "torque bump" under 3500rpm. This is caused by aggressive scavenging from high overlap--lots of intake and exhaust cam phasing combined with the characteristics of the manifolds.
it would take, at minimum, changes in the intake and exhaust system to add torque around 4000rpm. Like any other resonance tuning, when you improve one area there's a chance you will hurt another.
It seems unlikely that you could just reflash the ECU on a stock car with merely a catback and "get rid of" that dip without lowering torque somewhere else. There are a lot of engines with conventional port injection and cam phasers that have a similar dip. |
The boost range looks like it is timed to the length of the primaries (at 14-16" via my eyeball) and an effective cam duration of ~200ish degrees. Haven't looked to see if there is something that corresponds on the intake side, but I think the 'sound tube' may actually be playing a role with this too...