Scaling for head flow

[mock_glh]

Could a relative head flow ratio (ported/stock) be used for scaling the fuel curve the same way injector flow is? If so, is anyone out there doing this successfully?

[Aries_Turbo]

i wouldnt think so due to the fact that the headflow increase will probably not be linear throughout the rev range. the mechanical equivalent of what you suggest is like turning up the fuel pressure and that cant account for how the porting is going to effect the power delivery... ie something like softer on the bottom end and needing more fuel up top due to the increase in volumetric efficiency in the higher revs.

If you do your own cals (i cant remember if you do) you should only have to touch the pumping efficiency table. the FuelFullThrottle, FuelNoThrottle, and FuelPartThrottle pressure referenced curves assume 100% volumetric efficiency (or pumping efficiency as the cal calls it) so that pumping efficiency table adjusts for the differences that a blast through the RPM's brings.

I set my Pressure curves (Full, No, and Part) up with ChEM2 to a calculated AFR value (what a nice feature... it does take into account the pumping efficiency of the RPM value you input into the settings box though so keep that in mind) and then do some pulls at different boost levels to adjust the pumping efficiency table... if you are good in the lower boost you should be good in the upper boost levels for the most part but if you arent for some reason (fuel pump flow, turbo efficiencies at higher boost, intercooler efficiency at higher boost) then you can tweak the FuelFullThrottle or FuelPartThrottle tables at that boost level to account for this.

Brian

[mock_glh]

Excellent! I was going to ask if pumping efficiency would be involved (duh!). I am doing my own cals but I'm still learning a few things about stuff like the relationship of rpm and duty cycle, among other things. By the way, ChEM2 is great!

[ShelGame]

Also, a hi-flow ported head usually will lose flow at lower rpms. The net effect is that the PumpEff table appears to "rotate" about some point. If you just scale it linearly, then you end up really rich on the bottom end.

[Aries_Turbo]

i find for myself that once the cal is scaled for +40's and a 3-bar map, you really dont have to change a whole lot of things to get it to run well and correct.

you need to ramp down the ignition advance vs boost above 15psi, work with the pumping efficiency table to get it dialed in to your combo (cyl head work, intake and cam work, headers, larger exhaust housings and turbines, ie flow mods etc), and sometimes the pressure vs fuel PW tables like I said above, and the boost control stuff which im just getting into.

Brian