MWatson17

Hello all! I'm working on getting my new Thunder Racing Raptr cam tuned. It's still pretty fresh and I haven't had a lot of time with it yet, but I finally got to make a few clean passes at the track on Sunday. On a few of my passes I noticed that the car would make a popping sound from the exhaust. Some pops would come with a power loss, others would not. I have a video and datalog of one of the runs. The datalog shows two instances of knock retard on launch (which I plan on tuning out before the next outing) but the popping happens all through first and the bottom of second gear. AFRs are pretty stable after launch in the mid 12s. Timing was pretty retarded due to KR and conservative tune (around 20-25).

Here's a link to the video:
Like I said, the popping noise is throughout first gear and the beginning of second.

I can post mods and other info if needed. If anyone wants a screenshot of the log I can post that also. Just want to figure out why it's popping and address that before I continue with more WOT tuning.

Old Geezer

iTrader: (3)

And, the fuel psi is, when this happens??
Post the tune and data log[s].

MWatson17

No fuel pressure gauge in the car, so I don't know what the PSI is during the noise. I'll post the raw log and tune files, if anyone doesn't have HPtuners I can take a screenshot of the log.

Alvin@PCMofNC

What type of plugs are you running and what gap?

2xLS1

iTrader: (25)

It could be misfiring on bank 2 but with that bank's O2 inoperable (stuck at 450mv) it can not show up in the log. Misfires will show up as lean spikes on the narrow bands at WOT.

MWatson17

Plugs are NGK TR55. Can't remember the gap but I will check tomorrow. And if it were a bank 2 misfire, wouldn't it still show up in the wideband signal? I have that hooked into the bank 2 bung, that's why that narrowband signal doesn't read.

ctd

iTrader: (1)

I wonder if it is a fuel cutoff, looks like the same thing going on in second in that 6400-6500rpm area. Where my cursor is the injector's look to flat line in 1st & then in second. Quickly looking @ the tune I only see that ETC cut off @ 6200rpm which is suppose to be disabled. Might be worthwhile to bump that rpm just to be sure. Sometimes there cutoff tables hiding on us

The MAF is very lean from commanded, maybe get the MAF closer that will help the KR a lot. Then watch the Dynamic cylinder air & see if it improves, maybe load dynamic air pid to watch the top end air flow.

MWatson17

Lots of good tips in here, I'll check those cut off tables. As per my MAF being leaner than commanded, I had yet to spend much time on my VE and MAF tables, so I just set them to give a good AFR under steady conditions. I will be tuning those tables and PE hopefully in the next few days.

MWatson17

I have a potential development in my problem. I pulled the plugs, and #1 and #4 appear to have very fine hairline traces or cracks in the insulator. It's hard to tell so I'm including pictures to see what you guys think.

On my first track pass I made an error in my MAF calibration table which caused it to run momentarily lean, I have a feeling that it may have caused enough knock to damage the spark plugs.

Take a look at the pictures and let me know if you think it would be enough to cause this noise! I think I'm on to something here! (note the spark plugs are orange, because I put a can of octane boost in to help keep knock at a minimum during initial fuel tuning)

MWatson17

If I made it seem as though the car is untuned, I'm sorry. I did some tuning on it before taking it to the track, but it was just a basic MAF tune. Unfortunately I made an error in typing some numbers in the table when I flashed the tune, hence the lean condition.

BLK02WS6

iTrader: (2)

Cracked plugs will cause a misfire for sure. I would replace them and see how it is.

MWatson17

I'll do that tomorrow and do some work on the tune to try to get it a little better dialed in. I'll post back with the results.

MWatson17

Replaced the spark plugs and the popping noise is gone! Thanks for all your help, guys!

MMWS6

Id be really curious to see one of these new plugs pulled to have a look at if possible. I'm seeing a couple of things on those pictured above that you might want to be sure it is the plug and not fueling/timing that my be a little off too. The base ring carbon is pretty thick there, little rich at idle. Cannot see where the heat on the threads ends and also would like to see a pic of where the heat is on the strap of the plug.
What gap did you use for your plugs? Any increase in compression on this engine or just a cam in it?