I know how you fell.My dads 02 ext.cab shortbed Z71 with the 5.3 only put down 230rwhp and 240rwtq.It pulled those number with a borla exhaust,hypertech power programmer, and a K&N fipk,I dont understand why his were so low either.Anybody know why maybe?When it is 4x4 does it really lose that much through the drivetrain?Does anyone know about how much you lose through a Z71 drivetrain?

 

Well I figured that if a stock GT dynos @ 230rwhp stock and my bro-in-law's was modded and only made that.. then the dyno must be showing about 20rwhp less than the usual. If that is true then I should be seeing 233rwhp and about 276rwtq,,,That sounds more like what I was expecting

That's why I'm not too worried about the numbers. I have a baseline now to see what I gain from my mods.

Anybody wanna guess how much of a difference the Nelson Performance Tune will make?

 

Also, why would I have knock retard on a stock tune? 89 octane should be good enough gas. What causes this?

 

The computer has two timing tables in it. One is the high octane advance table and one is the low octane advance table. IF the computer sees too much knock with the high octane settings it will start using the low octane table. Knock can be caused by too low an octane, too much timing, extremely hot air, and a few other less common things. The computer compensates for pretty much all these conditions so on 89 octane you might not be running as well as you could.

I'd imagine with 89 octane gas your computer is running on the low octane settings. With 93 you may be able to pick up a few horsepower with the higher timing.

Knock retard is basically the computer pulling timing to stop detonation when the knock sensors report detonation.

Without a computer scanner it's hard to say whether you have any detonation or what timing table is being used though.