2xLS1

iTrader: (25)

Anyone know for sure how important it is for this parameter to match the actual size of the engine? I'm looking at the file from car with a 408 ci engine tuned by someone else that this parameter was never changed to reflect the new size. What all would this effect in the tune? I'm guessing maybe the values in VE table.

RedHardSupra

iTrader: (1)

every fuel calculation gets multiplied by it (read the 've cracked' thread) so it's a universal multiplier. if you keep it fixed even though your displacement did go up, your engine's VE is gonna suddenly be proportionally high to make up for the difference. think of it this way:
3*2 or 2*3. they both come out to the same thing. except that VE can be meaningful and helpful when it's calculated from/reflecting numbers true to the hardware.

gameover

not very important, it is used in a very minor way in the airflow calcs predominantly in the cranking airflow calcs. It is also in the misfire VE (load) calcs. It has no effect on the main airflow calculations when running in SD mode.

As an example, GM set it to 5.7L for many of the first released LS2 6.0L engines

gameover

this is incorrect.

RedHardSupra

iTrader: (1)

so is there an update to the 've cracked' formula? did i miss a memo?

gameover

i dunno, i haven't read that thread for ages. We use the cylinder volume to display the VE table in % as a convenience, however, the PCM doesn't do the calculation that way.

2xLS1

iTrader: (25)

Thanks for the clarification. Why don't you HPTuners owners add these little tidbits of knowlege you all have to the help file? Is there a reason you give us access to parameters that don't effect much or are not very important?

gameover

This one is mostly historic reasons, ie. LS1edit had it and if we didn't include it tunershops would have complained we were missing something important. It IS correct to set this to the right value, just that if you don't the main fueling will not be out.