Question about VE and IFR table interaction.

[ArKay99]

We have been tuning a 2000 C5 with a lot of mods. AFR 205's, 224/288 XER cam, LSX90, LS2 throttle body, headers, 32lb/hr(@43psi) Racetronics Injectors, etc. in SD mode for a while and have the VE table and AFR's dialed in nicely. After we scaled the IFR table for the injector size (26.2lb/hr @ 58psi) to the Racetronics injectors the VE table has an overall increase in numbers of about 32%. The higher numbers went from around 97.6% to around 128%. I am wondering if the VE table should be scaled back so the highest numbers are just below 100% and then apply that factor to the IFR table to keep the AFR matched. It seems that running the VE table greater than 100% is counter intuitive. Any feedback on this?

[Dirk Diggler]

My 0 vac ifr value for those same injectors are 36.46 and go up from there. My ve values didnt change much.



MAP (kPa) 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
Injector Flow (g/sec) 4.597555664 4.626209025 4.654686005 4.682989822 4.711123596 4.739090356 4.766893041 4.794534506 4.822017523 4.849344786 4.876518914 4.903542453 4.930417878 4.957147598 4.983733959 5.010179242 5.03648567
Injector Flow (lb/hr) 36.4891805 36.71659214 36.94260391 37.16724134 37.39052919 37.61249152 37.83315164 38.05253222 38.27065525 38.48754211 38.7032136 38.91768991 39.13099069 39.34313508 39.55414166 39.76402856 39.97281342
Injector Flow (lb/min) 0.608153008 0.611943202 0.615710065 0.619454022 0.623175487 0.626874859 0.630552527 0.63420887 0.637844254 0.641459035 0.64505356 0.648628165 0.652183178 0.655718918 0.659235694 0.662733809 0.666213557

[joecar]

My 0 vac ifr value for those same injectors are 36.46 and go up from there. My ve values didnt change much.



MAP (kPa) 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
Injector Flow (g/sec) 4.597555664 4.626209025 4.654686005 4.682989822 4.711123596 4.739090356 4.766893041 4.794534506 4.822017523 4.849344786 4.876518914 4.903542453 4.930417878 4.957147598 4.983733959 5.010179242 5.03648567
Injector Flow (lb/hr) 36.4891805 36.71659214 36.94260391 37.16724134 37.39052919 37.61249152 37.83315164 38.05253222 38.27065525 38.48754211 38.7032136 38.91768991 39.13099069 39.34313508 39.55414166 39.76402856 39.97281342
Injector Flow (lb/min) 0.608153008 0.611943202 0.615710065 0.619454022 0.623175487 0.626874859 0.630552527 0.63420887 0.637844254 0.641459035 0.64505356 0.648628165 0.652183178 0.655718918 0.659235694 0.662733809 0.666213557


I think the row labelled "MAP (kPa)" is really "BARO - MAP (kPa)".
Just my $0.02. :D :D

[ArKay99]

My 0 vac ifr value for those same injectors are 36.46 and go up from there. My ve values didnt change much.

Hmmm. My scaleing formula is SQRT(New Pressure / Old Pressure) * Old Flow Rate = New Flow Rate. That gives me 36.95lbs/hr. Then I found the percentage increase of 36.95 from 26.2 which is 41.03% which I then used as the percentage factor to multiply the IFR table. Did I go wrong in my math somewhere?

[Delco]

My 0 vac ifr value for those same injectors are 36.46 and go up from there. My ve values didnt change much.

Hmmm. My scaleing formula is SQRT(New Pressure / Old Pressure) * Old Flow Rate = New Flow Rate. That gives me 36.95lbs/hr. Then I found the percentage increase of 36.95 from 26.2 which is 41.03% which I then used as the percentage factor to multiply the IFR table. Did I go wrong in my math somewhere?

You cant use simple maths to get the IFR scaling right as each injector will have a different flow characteristic at different openings.

Take the 50lb rochsters as a example , even though they are nearl double the size of the std injector at low milliseconds they flow only 12% more than the std injector at high milliseconds they flow 175% of the std injectors.

The best thing to do if you already have a tune running the std injectors with a sorted VE is to scale the IFR initially to suit your ve table as the course adjustment then fine tune on the ve table. they all interact so at the each ill have the same effect.