Rough launch from a standing start

[GoPaul]

Any suggestions for cause are welcome:

If I punch the accelerator from a standing start I always seem to get a bit of a stutter. Best way to explain it is that it feels like the car nose dives before engaging and pulling away from the line. The car runs real strong on the highway but launches suck.

I have been considering a ported throttle body to remedy the flat spot but I figured that with all my other mods I should have overcame this by now and normally wouldnt' notice the difference. Could it be that my ported intake manifold or Vararam has something going on that is preventing good airflow or could it be that I am getting too much air and not enough fuel??..updated tune required maybe?

My list of mods are below:

anyone got any thoughts.

[KMPrenger]

Does the M6 have any kind of "nannies" that could be shutting you down when you spin the wheels? Could that be coming into play?

I'm not sure a ported TB does much of anything for a Vararam user. I have the VR as well. The end of it butts up against the TB and they line up perfectly. Other intakes slide over the end of the TB, creating a ridge the air must pass over. A ported TB makes this air transition much smoother.

In the Vararam, it is already a smooth transition. So that is my theory. Yes I am running a ported TB, but I had it way back when I had my AirRaid intake.

[GoPaul]

there are the 2 nannies on the M6 but regardless of whether they are on or off I have ran into the same issue. The first time I went to the track (with only an injen installed) I nevern noticed the stutter. Last time I went (with the mods listed) my launch was sucky - I have no doubt I'd have been in the 13's if I'd got a good launch but ended up with a 14.1. Below are 3 track slips - it seems the starts have suffered since installation of my ported intake.

My times are on the right on all slips.

The first slip is with Injen only:


The second is with headers and vararam:


The third is with the ported intake added:

[Blade]

The only time I noticed anything like this happen in my LLT was when I was doing some work on the engine, and forgot to slap the intake elbow properly on the TB. The damn elbow came loose and the acceleration was shot to hell.

It's either that, or maybe cylinder misfires?

[KMPrenger]

May want to check your MAF sensor as well. Maybe hit it with some CNC MAF cleaner.

[GoPaul]

Originally Posted by Blade

The only time I noticed anything like this happen in my LLT was when I was doing some work on the engine, and forgot to slap the intake elbow properly on the TB. The damn elbow came loose and the acceleration was shot to hell.

It's either that, or maybe cylinder misfires?

Originally Posted by KMPrenger

May want to check your MAF sensor as well. Maybe hit it with some CNC MAF cleaner.

good calls, I'll check this out.

Don't think I'm misfiring - no CEL's and car generally runs ok, it's just when launching.

[Blade]

I would recheck every connection around the IM and that intake. Something might be loose and causing a leak in turn resulting in crappy conditions within the IM. I see you got the vararam installed, double check the radiator too, from what I remember owners have to mess around with the radiator to install that intake. If it slipped or something, it might be causing a pinch in the elbow from the intake or nudged it loose.

[Nutbutt]

I would clean the MAF. They are not exactly the greatest for the V6. I had a one the was just within spec. Then i had the dealership try two more before finding one well within range. I know that the V8 MAF have identified strong MAF. But supposibly this is not the case for the V6. I just don't think delco wants to admit this for the V6.