01 ls1 z28 m6. 232 250 .632 .598 113 plus 6 bucking part throttle

[Mattsv803]

Hey guys I'm new and tuning ve table now mostly .01 .02 off everywhere set fuel for 14.67 as stoich. When taking off with this cam I get a little bucking and at part light throttle like decal or light throttle cruise it will buck. Afr don't jump. What do you guys do to calm big cams from bucking.

[Mattsv803]

Would it be timing related? I'm seeing 20-29 deg from 400 up to 1600 rpm. I believe I read somewhere that too much timing may cause a big cam to buck.

[PST]

Bingo!! Take the timing down some in those areas.

[Mattsv803]

How much do you guys like for big cams. It's like 20 at 400 800 21 22 1200 and so on up to 29

[Russ K]

With 15* overlap, you will get a lot of light throttle/low rpm bucking. Retarding the timing will just cause a loss of torque and make the engine labor. The bucking is caused by exhaust reversion on the intake stroke.

Russ Kemp

[Mattsv803]

It drives like a champ at cruise speed just when I let out and get in. Was a lot better with the fuel trims off almost 0 bucking. But I have a issue w the pe now. Once I got the ve and maf tuned and I'm all .01 .012 errors now. Mostly no error at all whole driving range but I have no power enrichment. It's set to 15kpa. 1500 rpm and 1.14 now to try and have a good afr it's 14.62 12.8 is the cammanded afr. The best I've seen is 13.8 and it scary how long it took to get there.

[Mattsv803]

Damn big cams and all their noisy glory. It sounds great. Just want a little better. Should I disable the short term fuel open loop and just leave the long on.

[POWERZONE]

We could help you better if you posted a file or log.

[Mattsv803]

How do I attach a log?

[LSxpwrdZ]

You wont get a 250 degree lobe on the exhaust to drive like stock, you can crutch it in different areas to help it but it'll never be perfect especially in the limbo mode you speak of letting off throttle and easing back into it. Another huge help is making sure the idle spark transition to main spark is smooth. I don't agree with pulling timing as all that will do is force you to give it more throttle which loads the motor harder to keep it from bucking. If you want it to feel lazy down low then go for it though.

[Mattsv803]

I'm still learning but it's a lot closer now. I'm at 22 to 27 deg in the part throttle range air fuel is solid. Now just getting the pe to come in when I want it too. And where I want. Learning more everyday!

[MikeOD]

When it bucks, look at the cell it's in on the timing table. Make the neighboring cells (2 or more in all directions) have the same number in them, then smooth that into the rest of the table.

Now ADD to that value until the engine smooths out. It's bucking because it's not burning correctly and needs more advance, and it's also bucking because since the timing is so far off, the engine is extremely sensitive to changes so the neighboring cells changing the advance is making a major difference in the burn.

Once you get it smoothed out, you don't need those cells to all be identical...as you approach the correct timing the engine will become less sensitive to minor changes.