Stage 4 drift cam and Bucking

[aalvarez3]

Hey everyone,

Feel like i have been chasing my tail on this one for weeks. I've got a 2005 c6 with a built 408 stroker and a Michigan Motorsports stage 4 drift cam. Specs as follows

Specs: 237/242 .629"/.615" 113 LSA


Issue i'm having i believe is cam surge. When slipping the clutch, all is well until the clutch is all the way out, then it starts bucking uncontrollably/violently- only way to stop it is to clutch in or rev it up higher. Have taken a significant amount of timing out of it, still there. I also have a noticeable surge cruising around 1500 rpm. Have attached latest tune and latest log. Hoping someone can take a look at it and give me some guidance. Thank you in advance!!!

[horsepowerguru427]

High RPM disable.jpgI cant view very many PIDs on your log, so i assume we're running different versions of the scanner. Have you thought about NOT running MAF only? Hard to say without more log info, but youre set to run MAF only from 300RPM up. Meaning youre not referencing your VE table. MAFs have a reversion issue when you have a cam with large overlap and duration. Meaning youre getting air movement back and forth on your MAF. Not just one direction.

Are you still running the stock 42lb injectors?

Get another log with a bunch of timing PIDs in the channel list. See which one is pulling timing. It looks as if something IS pulling timing down low when clutch is engaged.

[GHuggins]

Hate to say it, but seeing who tuned it fail the MAF and dial in your VE. You're going to need to dial in your injection timing, O2's and lower the right hand side of your proportional airflow in the idle section. You'll also want to fine tune your min air. Those should all help. If you have adjustable fuel pressure you might want to lower rail pressure down to something around 43 or 45 psi too. Retard injection to keep fuel in the cylinder. Kill a lot of the O2 swing then go from there.

[GHuggins]

You need to figure out injection timing first. Otherwise it'll just waste time. Just do it how I said in the PM. Pretty easy to do that way.

[GHuggins]

It's either air or fuel. You're giving it more air to fire, but it may actually just be because the VE isn't dialed in correctly and is overly rich or something like that. Cranking air is limited by tb brake air, so if you have a cam sometimes it's required to raise that so the tb will actually open with the commanded cranking air to get it to fire cold. May just require fixing the VE and then fine tuning cranking fuel and cranking air. VE needs to be right first and the lower quadrants of the MAF curve. I've even seen the lower area of the MAF cause this very problem where it's been smoothed out over and over again. Try putting stock in below 1500hz then do the rest. You never know.

[GHuggins]

Either force it to surge, which won't get you the best data but some data nonetheless or bring the idle rpm down as low as you can. Most of the time you can shape the torque models, idle spark and airflow tables to bring it down. If you have a manual you can use the clutch release and engine lugging to bring it down as long as the idle tables are set up to respond and keep it going and not just stall. Your goal is to hit the cells it'll see via rpm dipping or near stalling then you can interpolate from there. As long as your engine braking settings aren't too high then you should be able to use your scanner too and it's rpm controls to go as low as possible. If you can't do that then you can use your wideband errors as the engine is dipping and make adjustments to those areas as a general whole. Lots of ways to address it. Just have to find what's best in your case.