Bucking under deceleration

[kyotey1693]

Hey guys, I'm new to the tuning game. I've got a 99 WS6 LS1 heads and cam car that I'm trying to straighten out. It was tuned by a local shop. It runs decent but it has some drivability issues. I'm tired of dealing with local tuners so I'm slowly learning. The biggest issue I'm focused on at the moment is the surging under low speed/low throttle applications and some bucking during deceleration. I realize some of that is going to happen due to the overlap on the cam but I think it can be better.

I know this is one of the harder areas to tune on GM's but I'd like some suggestions on what to look for and what to try. From what I can tell DFCO is disabled. Should it be? That kinda sounds like one of the first things I'd want to experiment with to cut back on the bucking during decel. I also see it's running a little rich in that area and it looks like it's running a lot of spark down low. From what I understand, both of those things could lead to the bucking and surging as well?

I also see some significant jumps in the spark log at times and I don't really understand what's driving the change? Any pointers on that? Is there anything specific I should be logging for?

Here's the tune and a couple logs. I'll have the WB hooked up for the next logs. I was waiting some parts today and just wanted to log some data to see if anything stood out.

These are the cam specs.

227/234 .600"/.600" 111LSA 109 IC

30th JH Tune log1.hpl30th JH Tune log2.hpl1999 30th Anniversary - JH Tune.hpt

[SultanHassanMasTuning]

personally i like going SD on cammed LS1 cars, so much smoother

most of your DFCO is disabled.

disable spark smoothing as test also

[Digital Corvette]

A few things jump out at me:
- main spark tables are disabled at a very low speed (engine, spark, base, max speed). Not sure why you would want this. Suggest setting this value to something high that you will never see.
- idle overspeed and underspeed spark tables are very aggressive. Usually limit these to max 8 degrees. That said it is an effective way to manage idle surging with a cam.
- Fuel default injector pulse is usually set to equal the min injector pulse width.

VE table looks nice and smooth. This is good assuming the values are correct!
MAF table looks smooth.

What injectors are you using? A 46 lb something I am guessing giving the flow rate.

[Digital Corvette]

A few things jump out at me:
- main spark tables are disabled at a very low speed (engine, spark, base, max speed). Not sure why you would want this. Suggest setting this value to something high that you will never see.
- idle overspeed and underspeed spark tables are very aggressive. Usually limit these to max 8 degrees. That said it is an effective way to manage idle surging with a cam.
- Fuel default injector pulse is usually set to equal the min injector pulse width.

VE table looks nice and smooth. This is good assuming the values are correct!
MAF table looks smooth.

What injectors are you using? A 46 lb something I am guessing giving the flow rate.

DFCO is disabled. To enable you need to set the enable temp to something that is achieved (74C is stock) and set the baro entry/exit values to something that the engine achieves under decel. Cammed cars have much less manifold vacuum and will never to to the stock baro values.

[kyotey1693]

The injectors are FIC 365cc (40lb/hr) I believe. The MAF and VE look a little too smooth in my opinion but I haven't had a chance to log it with the wideband connected. I've got it all wired up but the scanner isn't recognizing the wideband.

I'll try some of the things you guys have suggested. Thanks for the help.