krowtis

I have the tunercat software to program the pcm. Ive done alot of reading on how to's and what not. Does anyone have any advice on how to get the most out of a mostly stock lt1? Its a 1995 z28 with 6 speed

All that has been done so far was a k&n cold air intake and catback exhaust.

Is there anything i can do to get more fuel with stock injectors? Injector constant is at 24.91, would turning it to say 25.3 be a bad idea?

How about spark advance. Would going up 2 degress be good and if it seems good go 2 more until i get spark knock?

Ive never tuned a pcm before so any advice would be awesome. I am expecting alot of trial and error

Injuneer

Do not change the injector constant. The PCM needs the CORRECT number and that is reflected in the 24.91 used in the stock programming. Increase the injector constant, the PCM shortens the injector pulse width because it thinks you installed larger injectors, the engine leans out, and based on O2 sensor feedback, the PCM raises the long term fuel corrections (LTFT) to get the A/F ratio back where it belongs. Net change = 0. All you managed to do is use up some headroom in the limited range (-15% to +25%) of the LTFT's.

You really need to understand the basics before you start randomly making changes.

Ignition timing is highly dependent on the octane of the available premium fuel where you live, and the elevation relative to sea level. Add too much timing and you end up with “knock retard” which will protect the engine, and slow you down. Stock ignition timing is already fairly aggressive, and reflects the benefits of the aluminum heads, the LT1’s reverse flow cooling system, and the reduced spark scatter achieved with the high precision of the optical cam position sensor in the Optispark distributor.

The largest gain would be leaning out the target A/F ratio in Power Enrichment (PE) mode. Under heavy throttle (defined by a table of RPM vs throttle %), the PCM richens the A/F mixture to achieve better power/torque. Normally the PCM is attempting to maintain the stoichiometric A/F ratio of 14.7:1. That's the ratio the engine produces the lowest total emissions of carbon monoxide (CO), unburned hydrocarbons (HC), and oxides of nitrogen (NOx). The cat needs that to work properly, and that A/F ratio produces decent fuel economy.

You will need a richer A/F ratio to make power under load, typically in the range of 12.8-13.2:1. But stock programming typically produces a target A/F ratio of ~11.7:1. That’s too rich. Lean that out to something closer to 13:1 and you can pick up 10-15 HP. There are tables in the PCM that need to be modified.

This guide to tuning is useful, and explains how to modify the PE mode target A/F ratio:

LT1 PCM Tuning - Tips & Tricks for DIY Tuning!

Have you done the throttle body coolant bypass = 6 HP? Have you looked at the dyno results for various modifications on the WS6.com site?

WS6.COM LT1 Trans Am

krowtis

I have not changed anything yet until i finish reading a bunch of stuff. But thanks for the info on the constants. I've read Solomon's tips. That was good info as well. I really dont want to make any changes until i feel confident enough to do so. So im probably gonna ask alot of crazy questions. Im definitely gonna check out that website. I want to learn and know as much as possible before i do anything. Thank you so much for the feed back