jayZo6

2006 C6 ZO6 Went for dyno to get my injector flow rate entered correctly . Tuner did few runs on every run car was falling on face around 52-5300 rpms tuner was saying there is knock and its loosing power . On street I don't feel power loss around 52-5300 rpms it pull good till 6500 + rpms. The dyno was mustang all wheel dyno would that be causing it ? About 7k miles on H/C/I heads not ported . Where do I start before tearing it down ? Thank you .

tektrans

HCI don’t they usually disable the knock sensors?
same shop that’s tuning did the work?

Spaceme1117

Check coils. Could have some failing at high rpm. Happened to my car on a Mustang dyno. Coil would misfire right at about 5000 rpm’s.

jayZo6

Took valve covers off to take a look at springs they were all good . On driver saw one of the coil was broken and check that little piece was stuck inside the coil hoping that was the problem. Will go for dyno again and update. It was different shop where work was done . Thank you all.

FastCarsNMeanGuitars

Try venting your PCV to outside pressure. Remove from feeding the intake. The oil vapors have a higher combustable temperature and can increase knock. I just experienced this on a Coyote Truck engine that uses a fair amount of oil. The nature of this engine allowed us to hear it and it was almost elusive , until we had an engineer point this out.

Next invisible culprit could be a bad harmonic balancer. Again just went through this recently where a dip in power increased with harmonics either on the valvetrain or ignition. This was a stock balancer and replaced while on the dyno. Again, an engineer was present and it was experience that caught it. Hope these long shot insights help someone.

Just a few invisible ones that I can point out.

jayZo6

Can you route pipe from valley cover to clean air port of oil tank and block manifold inlet and outlet front of throttle body ? Or valley cover to catch can (2 way catch can) then to clean air port to oil tank ? And put filter in place of oil cap.

Thank you.

FastCarsNMeanGuitars

Stop or cap crank case inlet at the intake, vent crank case to open air. Just for your test purpose or dyno testing. These engines want to classify the process as ' using ' the oil. However, its getting past the rings, atomising and raising the combustion volitility causing increased knock and being picked up RETARDS your timing. Lowering Power. Aside from rattling your pistons, an off cadence by-product that is not like race gas. Although the flameability is super high. Its like it fools the sensors. What we are talking about here is rampid in racing. Some mayh not even know about this as it is a deal that will fly by the sensors on a run.
Look, your diagnosing a deal, so don't worry about it. Just look at the data, isolate to find the gremlins. Does your stock balancer show signs of cracking or drying out ? Does it wobble ? Lash your valve train and during that process, one lifter fail can darken your world. Stay at it my friend, tanacity wins.

jayZo6

Waiting on tuner to get me in . The balancer looks good no wobble it only got 4-5k miles on it .I will update when on dyno again . Thank you.

jayZo6

Went to get dyno again blocked intake vacuum pipe at manifold and let the pipe open . Today ran to 57-5800 then dropped again making good power upto there was little spinning on dyno . Not sure what's going on . Planning on doing compression leak test next . Anything else you guys think could be wrong with it.

hubes

Could be carbon buildup. Try running some sort of combustion chamber cleaner through it. Techron, redline si-1, etc, something with PEA in it. I'd also recommend installing a catch can to try to cut down on oil getting into the intake, which as stated earlier can cause knock, but can also cause more carbon buildup, which leads to more knock

Purple92

Could be a weak fuel pump or a resticted fuel filter. As the RPM goes up at WOT - so does the amount of fuel required. That causes the engine to run lean - and it can cause knock.

If possible try to hook a fuel pressure gauge to the fuel manifold, and tape it to the windshield when dynoing.

hubes

I assume the tuner is using an AFR gauge. Did he say it's going lean?

BigBlok502

I was having a similar issue with my FBO LS2, only at the 4,400 RPM. I could not feel it on the street, but HP Tuners showed Knock Retard at that RPM and the computer was pulling timing, close to 10 degrees. I went through a process of eliminating all possible false knock:
- Make sure exhaust is not touching the car anywhere
- I had oil puddling in the intake, cleaned oil out of intake and installed catch can. The oil mist can reduce the octane rating.
- Installed cooler heat range spark plugs, NGK TR6.
- Used bore scope to ensure no carbon buildup on pistons.
- Removed X Pipe and used bore scope to ensure cats were not melted, the honeycomb looked like new.
- Softened Knock Retard for each cylinder.
These reduced the Knock Retard some, but did not eliminate it, telling me it was real knock, so I added some Octanium to the gas tank, viola, no more Knock Retard. I returned the tune to allow 100% Knock Retard. Ran that tank to near empty, then filled up with Top Tier 93 octane, I had beep using BP which is not Top Tier. This eliminated my Knock Retard.

Good luck on your Tuning.

T-REV Motorsports

If it’s spinning on the dyno the torque numbers will roll off as the tires loose traction. I’ve had lots of experience with this from tuning shitbox Hondas for the last 13 years. I keep a spray bottle of vht and it makes a world of difference with about 4 sprays per tire and a minute or two rolling to get some heat into it.