42NightZ28

I understand that the Thunder Racing and Comp XER Rates are alot more aggresive than the normal XE rates. My question is what are the Lunati Ramp Rates for there Cams. I have the 221/221 112 Lunati that is Sold by Thunder racing and in the description it is described as having "Fast Ramps". Can someone clarify where it falls?

Steve - Race Eng

iTrader: (1)

I don't see anything particularly unusual about the ramp rate on this grind. You did not list the max. lift but I assume it is .558" as listed in the Lunati catalog.

The method to gauge the cam intensity (lobe aggresiveness) is to subtract the duration at .050" in this case 221 degrees, from the advertised duration 283 degrees. Lunati uses the SAE standard .006" valve lift duration (.006/1.7 rocker ratio = .0035" cam lift) as their advertised duration by the way. Therefore 283 - 221 = 62 degrees. This difference is called the Hydraulic intensity of the camshaft. This figure is used to compare camshafts from various manufacturers (with the same advertised or same .050" duration) to determine which has a higher ramp rate. The lower the number the better for performance since the rate of lift is faster.

The biggest problem here is various cam manufacturers use different lift measurements for their advertised number. In order to make an accurate comparison the advertised numbers need to be measured at the same lift - the method Lunati uses is the SAE standard but other manufacturers may list advertised duration at .010" lift or some other figure purely for advertising purposes.

Steve Demirjian
Race Engine Development