Frost...spark related question

**0rion** · 08-13-2009, 02:37 PM

I went back to CLSD a week or so ago and actually like how the car runs vs running the MAF. I'm not sure if it'll be as consistent due to the weather variable but overall it idles better and has better throttle response.

What I would like to know is how to dial in the cruise spark tables. My spark table in the cruise region needs work and I'm not sure how to tell when you're at optimum in that area. WOT is good to go but I'd like to work on those cruise areas.

**Frost** · 08-13-2009, 04:21 PM

Without a load dyno there is no real way to do it. All you can do is advance to knock and back off some if you feel like you want to run it up. Also be aware that CL will be swinging the fuel around.

**0rion** · 08-13-2009, 04:36 PM

Originally Posted by Frost

Without a load dyno there is no real way to do it. All you can do is advance to knock and back off some if you feel like you want to run it up. Also be aware that CL will be swinging the fuel around.

I can always put the car back in open loop.....the ve is already tuned. The whole reason I want to do this is I have a slight bucking issue that I'm pretty sure is timing related ( just from the way my spark tables look). I can take another log and make sure my fueling is squared away but the last time I logged it the fueling was pretty damn close. The only other thing I can think it would be is spark. It's a slight buck at steady throttle after the stall locks up.

**Frost** · 08-13-2009, 04:59 PM

Bucking is most commonly too much airflow though it can be high spark...

Try this, make a note of the MPH that you get bucking, goto the TC, zero everything in the MPH region that you get bucking except the 400RPM column. Give this a try firstly.

**0rion** · 08-13-2009, 05:19 PM

Originally Posted by Frost

Bucking is most commonly too much airflow though it can be high spark...

Try this, make a note of the MPH that you get bucking, goto the TC, zero everything in the MPH region that you get bucking except the 400RPM column. Give this a try firstly.

you know....you may be on to something. I never even thought to address the airflow. Thanks. I'll try that first and see what happens. I'm assuming if the bucking goes away then I can lower that table in the problem area until the bucking stops correct? At least that's what makes sense to me. It's really a very subtle buck and I've just lived with it because it's really something minor but if I can get rid of it I will. It was worse when I had my stall locking up sooner. If I can stop it here I may lower that lock speed down and try to get rid of it down low too.

**Frost** · 08-13-2009, 05:24 PM

The exact approach depends on the nature of the buck. Ist it all light throttle, all decel, or all immediately following throttle release? The problem is the cumulative result of all of your airflow adders is giving you a value that is too high. If your base/idle airflow is too high, if you have too much throttle cracker, if you have too much throttle follower, etc. I suggest the throttle cracker as the beginning of the investigation because it is an easy place to pull by MPH, and as I noted, it is a problem of sums. Even if it's too much throttle follower, having the TC reduction still limits effective airflow, so it's an easy start.

**0rion** · 08-13-2009, 05:34 PM

I follow you. I think I might have to take a good look at all those airflow tables really. Airflow was the first thing I tuned on it and at the time I knew considerably less in general than I do now. I need to revisit those I think and see what I can come up with. Tell me what this sounds like to you.
When I was running my MAF I noticed my idle rpm was always a tad higher than I commanded, especially sitting at traffic lights in gear, and going back to SD I notice my idle rpm's track much closer to commanded. When I say they were higher they were 100-150 rpm higher and now they're much closer in SD with no other changes. I kinda always thought that was an airflow issue but again it was such a small thing I just lived with it.

I'll start messing with this stuff this weekend a little and update the thread in case it might help someone else down the road. Thanks for the info.

**V8MUSCLE** · 08-13-2009, 07:27 PM

my car will buck in first gear just barley above idle, no tune, just a slp cat back. its done this since i got it at 100k miles, ive put 30k. after i get do everything i want to it im gonna probably get you to tune it, full exhaust, 228r cam, and of course a ram air hood/intake.