Yes I am running a maf because it is a 1 bar tune and no I don't think I have messed with the burst knock.

Thanks BlackGMC. I will do that and I will log those other 2 parameters when I scan again.

 

I completely reworked my part throttle timing and PE, and slightly desensitized my knock sensors as a precaution, and I STILL get this shuddering in overdrive at 60-70mph when I'm around 40% throttle and 11* timing. Sometimes there is no KR with it, so I know it's not that. Could it be bad plugs? Even though it runs fine in all other situations... Any other ideas guys?

 

What is your fuel ratio when this shuttering occurs? Are you in boost when this happens? If so how much? What RPM are you at when this happens? My tune doesn't have any less then 15 degrees timing and during normal driving WO etc. I never see less then like 16 period. However I will say when I was running MAF it was a PITA to tune transitional areas like what you are speaking of. I also found that letting the converter unlock a bit sooner in OD would help what you are speaking of. If the converter stays locked in OD and you are building allot of boost at low RPM you will get some KR pretty easy. High load, high boost, low rpm, slow accel makes for some KR from what I have seen.

 

Fuel was still in 14s. I have adjusted the PE to kick in at lower TPS now.

Yes, this is a high load, low RPM situation, with about 4 psi of boost. I like being able to go up steep hills or pass cars without having to unlock the converter. 45% throttle in OD is right on the threshold of unlocking the converter, and I really don't want to have to change it if I don't have to.

It worked fine until I swapped my TR220 with this GT2-3 cam. I am a newbie tuner, but I'm stubborn and want to tune it myself, with help from you guys of course. I will try again later with my tweaked power enrichment. Here's a copy of the log for you to look at. It is toward the end of the log. I would let off immediately when the shuddering began.

The wideband reads about .5 leaner than it actually is for some reason. The gauge in my truck is correct so I go by it.

The shudder can be seen as RPMs actually drop from frame 3580 to 3581.

 

Are you talking about that 2 rpm drop..? It's difficult to diagnose a physical symptom with a log like this... Not sure if I missed it, but can you explain the shudder in detail? What does it feel like, where does it feel like its coming from, frequency ie engine speed, valvetrain speed, or drivetrain speed, etc...

 

I would be willing to bet the reason its happening now is the high cyl. pressures you are getting in that area from the GT2-3. The 220 had more overlap and therefore your cyl. pressures would have been lower. If you are in boost you should not be in the 14's for fuel ratio...

 

It's just a hard vibration and loss of power. Like a really bad miss. Easy to feel in the cab.

Thanks 03sierra. I think you are exactly right about the higher cylinder pressures causing this. How would I tune around it?

For a high load, low RPM situation, would you recommend full PE, or just partial? My full PE is 11.4.

 

Cant see your tune and haven't looked at any logs, but just going off of what you are speaking of. Personally I would ramp in PE a bit sooner ( you need more fueling when you are in boost, shouldn't be at 4lb and 14 anything air fuel) also I would let your TC unlock a tad bit sooner. Build your PE enrichment table based off of some logs so you can see at various RPM's and loads when you are in boost. Or go 2barSD. Personally I love SD, to me its much easier to tune and fueling is wherever you put it. You just have to know what you are doing because there are less fail safes.

 

As he said, increase the ramp rate for PE. At the lowest RPM, you shouldn't even be in the 13s when you tip into PE.

Is this vibration strictly speed related or does it happen in any gear under that similar amount of load? After I installed my new driveshaft, if I would just creep into boost at like 80mph, I'd get a vibration. It was because of a bad pinion angle though. Added a shim and it went away.

 

It only happens when the converter is locked up. It runs great in every other situation.

I might lurk through the tune repository and compare some stuff.