Bob ,hoffman900 wrote: ↑Fri Mar 16, 2018 5:54 pmLarry, Jay, or anyone,maxracesoftware wrote: ↑Fri Mar 16, 2018 2:56 pm the Dyno Air Turbine ( if they have one ?? )
will immediately tell you if its really Valve Float issue
What metric would you be looking for to distinguish timing vs. say valve float?
with the Air Turbine , you would look at these readings for evidence of Valve Float :
[1]= easy ... TQ and HP fall-off quickly the higher the RPM , and BSFC's climb very rapidly in that same RPM Band
[2]= Air Turbine CFM readings--> as RPMs climb, CFM levels off or can also fall-off rapidly
or can level-off somewhat before Peak HP RPM, then climb a little more, then really level-off once again, then higher RPM drop off quickly
[3]= Air Turbine CFM readings--> Look for the "CFM Rate of Change" .... basically like #[2] above, but the 'Rate" slows down quickly with Valve Float
at mid to high RPM
[4]= Air Turbine CFM readings--> Look for the "Volumetric Eff % Rate of Change" .. this is just same thing as #[3] above
i've seen the Air Turbine CFM level-out maybe drop slightly , then as RPM climbs, the CFM starts climbing again,
then a little higher in RPM, it levels off again, and going even higher RPM, the CFM and VE% drop very quickly .
....it would appear the Springs are doing a 'dance" at a lower RPM , then a little higher RPM, the springs are back in control,
then even higher RPM, severe Valve Float comes back .
air up the Cylinders and change to higher pressure Valve Springs ,
gain something like 25+HP at 7000 RPM on a 550 HP Engine
and now Air Turbine shows a steady "Rate of CFM increasing" as RPMs climb to 7000 RPM and above
this is just simple examples, you can loose a bunch more than 25 HP on higher RPM , higher HP engines
and just one more Note :
i only will make a few Pulls with the Air Turbine on,
just to see CFM and VE and check for Float ,
after that i remove the Air Turbine and do the rest of the Dyno testing without it .
reason--> the Air Turbine has length and can effect Total Induction Length Tunning
and the other reason is that most all Carbs will breathe a bunch of Air from around the sides of the Top of the Carb,
and the Air Turbine body is restricting AirFlow coming into or turning into the Carb at its top sides of Venturi Entries .