Got a customer truck here with 5.3 and a BTR stage 4 cam in it. Everything else is stock. I disable the MAF and tune the VE table. Everything +/- 3. Re-enable the MAF and trims go crazy positive. 20+. I have tuned a bunch of these and never have seen this.
Could they have installed the cam wrong? This thing has NO lower end. In 4th gear at 60 to keep a steady speed the map readings are around 80-90kpa and go to 100 with very little throttle.
Any idea's on what could be wrong?
You want a stage 4 camshaft on small cubic inches with a stock stall to have low end power, that is kinda funny.
Kinda need to post the tune and logs. We need to see how you setup the tune for what you are doing.
2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.
If you don't post your tune and logs when you have questions you aren't helping yourself.
Yeh I know that this isn't going to make any torque with the stock everything else. It's a kid that just wanted a lumpy cam sound that put this together in what I would call a hoopty.
I just have never seen one that after tuning the VE table enabling the MAF makes the trims go majorly positive. I searched and found a few threads that mentioned this but they never said if they fixed it or found anything that would cause this to happen. Being as this is a stock intake, tube, and filter setup the MAF scaling should not be off by much at all. Would be nice if someone has seen and found a fix for this that they would post it so anyone else that runs into this has a direction to go to fix it. I will pull a log later today showing the trims after enableing the MAF.
As stated already. Post a log/tune so we can help
Here are back to back with the only change being MAF enabled or pe mode.
Well the only area I can see that's 20+ is idle areas. I'll leave out my opinion of the rest. A cam with that much overlap will need the injection timing adjusted which looks stock still. Otherwise fuel goes right out the exhaust and the O2's think it's still lean, hence the 20+ trims. Didn't see a wideband in the logs either
Last edited by rabbs88; 09-10-2023 at 11:48 AM.
You have both long term fuel trims and short term fuel trims enabled. If you are trying to use narrowbands to tune the lower RPM range of the ve table, that's fine, but you should turn off LTFT's for that process. The BRAF table shows some pretty sizeable variance in numbers between the GEAR and PARK NEUTRAL table... That can't be right. Typically there is a 3-5% variance between the two lines in the table.. not like what is currently there.
The idle spark tables to include IN PARK and IN GEAR, and the low octane and high octane tables all need to match in the lower rpm ranges up to and including the idle rpm areas.
The VE table is going to need a lot more work before it's time to turn the MAF back on... Look at the 3D view of the table and it will be evident why I'm saying this. Also, in order to properly tune the VE table you are going to need a WIDE BAND O2 sensor! Do not attempt full throttle tuning of the VE table with just the narrow bands as that is a recipe for disaster.
The injectors-show to be stock in the tune-are most likely going to run out of headroom at full throttle. They might work right now, but if he makes any other changes to increase airflow into and out of the engine, those injectors are going to be the bottleneck, and the engine may run lean on full throttle 5000+RPM pulls.
That cam is NOT going to be happy without a stall converter.. Further, that cam is going to need long tube headers, gear swap to something higher numerically in the rear diff, cold air/larger air intake, head work, better intake manifold, and better exhaust, to take advantage of the potential of that cam... I'll bet the vehicle is SLOWER now with the Stage 4 cam, than it was with the factory cam in it... But hey, if it sounds cool at the red light-who cares if any 4 cylinder honda can absolutely mop the floor with his truck... Grandma on her bicycle is going to embarrass him from a dead stop... Sometimes... you just gotta look at the totality of the situation, and just realize that YOU don't want any part of this kind of drama. I'd recommend him to a "pro tuner" and send him on his way.
If you look at the idle MAP readings, he is already at 65KPA, or thereabouts. The over-lap of the cam is causing that low vacuum situation. You can tune around that low vacuum situation, but it's always going to be a compromise. Good luck.
Thanks for the comments guys. Your preaching to the choir. I told him it's too much cam but he did it anyway. He did put long tubes on it but a junk kink bent exhaust after that.
He's not going to be running the snot out of this truck. He's not that guy so I don't think him running out of injector will be an issue.
Yes it is slower now than when he started but it sounds meaner and he's happy? I don't get it either.
I had to add air to the in gear air table probably because he is using a stock converter. I don't plan on tuning the upper end he just wants it to run and idle. That's why I didn't put the wide bands on it.
I still just don't understand why the big swing in trims when I enable the MAF.
Thanks for reminding me about the injector timing. I hadn't thought about that.
Yes this is a get it running the best I can and walk away. He won't do anything else with it after that.
Reply With Quote