In your calc. you use
"314.5 = Air velocity in Feet per Second " how is that measured, on the flow bench or engine?
Can you please explain L/D ratios
Larry, If a head/port doesn't flow better, or has very small gains past .35 or .36 L/D will opening the valve further gain power if the disch coef. is dropping rapidly up there? --Rick
One thing I don't see in the above formulas is a consideration of mach numbers as realated to air pressure (Mach 1 varies with regard to air density,- temp, humidity and pressure)
With a 9:1 CR engine, you'll have a lot of Clearance Volume that can act more as a Dampner, reducing the "Hit" on the Intake and Exhaust Systems...and creating a greater volume where exhaust gas residuals can
be if you get the Header Pipe dimensions and Wave tuning wrong.
you can loose a lot more Torque/HP with low CR than with high CR if
things are wrong, especially at lower RPM range like under 4500 RPM when there's more Time and slower velocities
we had found 30 HP. That is a HUGE number for our type of racing (Nascar Elite touring series).
Anonymous wrote:Back in the mid eighties some one ( heddman I think) came out with an Anti-reversion cone mounted to the header flange against the heads, that was good for 200HP at rpm that the motor wouldn't pull down to with standard headers ( it wouldn't run WOT that low RPM but with new headers would make 200 hp@WOT at same rpm. Would have probably made a great start on road race exhaust. Didnt seem to change peak #'s.
Our 30 hp was over what we were running in the car before. We had Dynatech and McCabe headers and collectors, pretty stuff!! but apparently more suited for unrestricted applications. Spent several days on the dyno trying almost all of the combinations, plus it had to pass a Db rule.
We had a hard time believing 30 hp, so we took the engine back over to the rental dyno, just to make sure that the output hadn't somehow changed. Apparently it was all in the exhaust. As a sidebar this team has LOTS of victories in Nascar's touring series.
We haven't raced in two years but we have rented out the car and motor, and it was second fast qualifier for a SWS race. At this point I am trying to get ideas, and maybe put another enginge together.
I saw something in jeg's EMC about enclosing the cam journals and lifter bores to control windage, has anyone tested this?? would you be willing to speak on this forum about what gains were found??
Would the 390 cfm carb be the choke point or would it be the valve opening?? Brodix 10X WT
The cross section area next to the pushrod is very narrow (1.2") and is the smallest CA. CA is only 2.33" here.
Engine is dynoed with 6400 peak hp.
LPV= 0.00353x6400x4.25x(4.5x4.5)/ 2.33= 834fps
I calculated the max rpm given with 660fps.
I can switch intake rockers to Indy 440-1 to get more offset and make the port much wider, a guess would be to have new CA in the 3.0 sq inch range.
I might have to switch to offset lifters also to get there.
This area increase will make the LVP in the 660-670fps.
What can I expect to gain by doing this ??
CA Area after this choke is significant larger and valve is 2.20" right now but will soon be 2.25" with 89% throat area.
Greatful for any advice.
Tom J, Sweden
usually you will start to loose the very bottom end Tq/HP numbers
and by 3500 to 4500 rpm you will be pretty close to same numbers as you were before , and 4500 rpm and higher you should be picking up HP
if your LPV was as high as 834 fps
usually its pretty safe to go ahead and enlarge that Choke Area if your
LPV was 600 or higher fps, but different heads have different shapes with higher or lower localized spots of velocities...so this should be double-checked with a Pitot Probe
Users browsing this forum: 69top502, C & F Race, Cubic_Cleveland, donc, Google [Bot], gowest, gramps, KRYPTINITE RACE ENGINES, Orr89rocz, pmann, Rallyace, sneukam, The_Countdown, WeingartnerRacing and 16 guests