I wiped out my old tune for my 355 completely and used a stock tune file from a 95 Z28 because I converted my 97 SS to OBD1. I am now a 383 Stroker and I installed a set of racetronix 42# injectors...how important is it to update the Injector Offset vs Battery Voltage from the stock parameters to the parameters for my new injectors? What does this do exactly?

Also, since I am now a 383 instead of a 350, how important is it to change the engine size in the tune and what does this do?

Finally, i heard about changing my pulse width in my tune for my new injectors...how?

My car has been dyno tuned by a good tuner here, and managed 458 RWHP and 410 RWTQ, but he did not change any of the above parameters from the stock ones....necessary or no?

 

Yes it makes a difference. Injector offset will effect when your injector fires in relation to when the ECM commands it to. Different brands have different offsets, sometimes models within a brand too.

Your injector base pulse width will change when you adjust injector flow rate.

Changing displacement is also a necessity, this is important for SD (MAF failure) mode.

I've seen tuners adjust the tune to make the car run good, but they do it wrong (my dyno tuner did this too).

Read this link a bunch of times, then this one a bunch of times.

If you don't already have an ALDL cable, get one along with Tuner Pro RT (free), then go to LS1LT1.com look for Steveo and download his XDF file in his signature (it has most perimeters explained if you hover over them with your mouse).

 

Much more to the voltage offset table than injector flow rate. Same flow rate, but different brands use different offsets. As in: Lucus injectors use much less offset than Bosch.

 

Z28, sure sounds like a nice upgrade you have there and good advice given above.

Also hope you don't mind me post-bombing your thread with a little shoutout to my old buddy Ed Wright