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Re: Thank you Dan

November 17 2011 at 9:48 AM
Dan Jones  (Login 74Pantera)
from IP address

Response to Thank you Dan

> lift was less on the exhaust than the intake. Is that a typo or intentional?

Intentional. The exhaust blows down early in the lift cycle. Vizard suggested
that many engines work better with a shorter rocker on the exhaust side and I
tested it on the dyno 351C. Peak power was about the same but mid-range increased
with a shorter exhaust ratio. A couple of years back, the Engine Masters magazine
had a listing of all the EMC contestant engine secs, complete with cam specs.
These were engines that were trying to maximize average power between 2500 and
6500 RPM. Most of them had more exhaust duration but less exhaust lift. When
I do a cam optimization, I check shorter, even and longer lift using a coarse
grid. In most cases, the more aggressive the cam, the bigger the effect but
it also depends upon the cylinder head intake to exhaust ratio. For mild cams
like yours, the difference isn't large. Also, the higher lift of the Bullet cam
by itself isn't a huge effect. The higher ramp rate of those specific lobes is
the more important effect. The high lift is a by product as it sometimes makes
it easier to control the lobe motion.

> Do you have the valve opening/closing events?

For the Bullet, installed at 108 degrees:
IVO 23.5 deg
IVC 59.5 deg
EVO 73.0 deg
EVC 21.0 deg

IVO -2.0 deg
IVC 34.0 deg
EVO 47.0 deg
EVC -5.0 deg

Remind me by email and I'll send you the full simulation report. It has
all the modelling detail (inputs and outputs).


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