Tuning for a quicker start?

[elementaltoad]

I've always had one big gripe about the LS motors on start up: All of them seem to start slowly.

I have had 3 LS cars and 2 LS trucks. The common issue with all of them is that especially on a warm start, they just grumble to life. It's a hard thing to describe but cold starts generally have a quicker rev (up to around 1200-1500 RPM) at start and then settle down to idle. However after running the car and letting it sit, if I start the car it barely gains RPM (800-900RPM) and then settles back to idle. Cold starts almost remind me of a cammed car with a spot on tune, and warm start are almost like a carbureted and boiled fuel on a hot start.

I also have a 300C SRT8. On start the SRT fires almost instantly with a rev to around 2k RPM and then settles down confidently to idle, even with a hot start.

Is this simply typical of the LS motors or can it be tuned to produce a more quality start, and what would I be looking at to modify this in the tune?

I can get videos if needed of the difference between a dead cold start and a warm start if needed, but as many LS cars as I've had, I get the feeling this is common among the bunch.

[blownbluez06]

The startup flare you describe in the 300C isn't desirable in any way. The car should start and hit its target and stay there, not flare and settle down. There are things in the tune to stop that from happening that you can discover and play with to make it do that if you desire. Startup is the same as everything else, throttle/IAC, fuel, ignition. Just learn to evaluate which it needs and give it to it. Startup & friction airflow, prime pulse and all the associated modifiers, cranking fuel and associated modifiers and your spark tables.

[mowton]

There is also a table tjat is called startup idle rpm in the Idle>rpm tab. it sets the idle rpm at startup and ove its time axis returns it to the the final idle desired rpm.

Can play with that...

Ed M

[gofastwclass]

I agree with blownbluez06, if what you are describing is what we think you are. One of the benefits of fuel injection is tuning out little annoyances like that. Just to be sure I would like to see a video of what you are referring to but most people want to eliminate the part you like and spend a great deal working on it. Your car shouldn't rev to the moon on a cold start like an antique carb with a mechanical choke.

[Higgs Boson]

If my car revved up to 2K RPM when I started it I would drive it off a cliff. I highly prefer my startup to be a "begin running" rather than an "explosion to life."

[elementaltoad]

If my car revved up to 2K RPM when I started it I would drive it off a cliff. I highly prefer my startup to be a "begin running" rather than an "explosion to life."

I'm likely giving the wrong impression, but there is a confidence that an engine should start with. Generally on start up, the revs hit ~1500 or so, and immediately drop to desired cold idle RPM, gradually reducing to desired warm idle as the car meet closed loop.

My Z28 doesn't do this, it just grumbles to life and drags the RPM up to normal idle. I'll get a video of it when I leave work, but it just feels "lazy" when it starts.

This is what I expect from a well tuned car, right or wrong I just want to make sure the LS1 is behaving as intended:

https://youtu.be/mbauqD4Q49k?t=92