Can't figure out this noise
 

I've made some significant modifications to the car, running direct fire and EFI now. I thought for sure this was some sort of ground loop but I've swapped around the coil grounds a few times and the noise isn't going away. It's definitely inside the cabin as I cannot hear it outside in the engine bay. Might be behind the HVAC or possibly the gauge cluster, really not sure. Any suggestions would be helpful.


Coils are IGN-1A. They have 3 ground pins. One goes to the ECU, one goes to the front motor housing, the 3rd (marked high current) goes to the battery but I also tried this on the frame and the motor housing. The ECU and wideband are grounded to the front motor housing. I've replaced the starter power cable and ground. I verified it isn't the wideband by pulling its fuse. It's not coming from the radio speakers.

Next thing I'm going to try is pulling various fuses from the main fuse panel to see if I can isolate it to a particular circuit.

Sorry if this comes off as a rant, but it is really bugging me!

Try disconnecting the speedo cable at the trains and see if it goes away.

But that's not spinning when I'm parked. I tried turning off the tacho output on the ECU but that wasn't it either.

I just slapped on some headphones to hear better This noise is not the same one I was talking about that I heard in your driving video.

This almost sounds like really noisy fuel injectors.

Yah man, put some headphones on and listen to the video I sent you. Exact same noise. Id1050's are noisy.

Feel relieved?

Somewhat relieved? I mean, for it to be knock or detonation, I wouldn't be seeing such rich mixtures. I've felt the bucking that goes along with low RPM knock and there isn't any roughness.

If it was a ground loop, I'd most likely also hear noise through the stereo too but it's crystal clear.

I'm surprised I didn't hear it the first few startups, but then again I was worried about not stalling it and stuff. I'll listen closely to the injectors next startup, that could very well be it. My first thought was that it was the fuel pressure regulator which is attached to the firewall. It still could be related to that if the injectors are pulsing and causing a reverberation through the fuel lines. Maybe I can isolate the regulator with a rubber mount.

I think you’re right. It’s gotta be the injectors or the fuel lines reverberating through the firewall, which is why I can’t quite pin point the source.

I’m not running a FPD (fuel pulse damper), but should I be? Maybe i’ll try isolating the fuel pressure regulator and hard lines from the firewall and see how that goes.

I don't run a damper. If you Google around you'll see other people talking about loud id1050s, I noticed it right away when I went from some 46lb green tops to the Id injectors. Just get used to it as a normal sound.

As for the driving video You can still detonate when rich. It usually won't happen on an na till nearly 30 degrees at wot.
The 20 degree split seems really odd to me, depending on your leading you could be igniting the incoming mixture. You can do that at the engine will still appear to run normally.
Im only knowledgeable enough to know to start double checking my coil and case wiring and make sure I'm properly zerod out. The car will still run usually when things are wrong, but not as good as yours seems to. Just be aware.

Post that driving video here, hopefully I'm wrong and your good to go.

Didn't get a video, but a screw driver held to the injectors, then the fuel rail, then the fuel pressure regulator confirmed the sound is just the injector pulses using the firewall as a drum. Some of the videos I found on YouTube, people were swapping braided lines for rubber with push fit style fittings in an attempt to isolate the sound from the other components. I'm not going to worry about that right now, bigger fish to fry.

Thanks for reading!

You could also stick foam in there like some newer cars do under the intake manifold to try and "absorb" the sound. Don't know what type of foam it is but I'm sure it's heat/fire resistant.

I have a few of those rubber stand offs from the A/C system. When I get time I'll try to use one to mount the FPR and any place the fuel lines contact the firewall.

Do you have a mechanical oil pressure gauge with a hard line going to it? I just recently replaced the oil pressure line going to the oil pressure gauge with ss tubing. The plastic tube broke and made a big mess. Now i have a similar noise inside my car from the ss hard line going to my gauge.

I don't have an aftermarket oil pressure gauge, I'm just using the factory sender for oil pressure, but I could see how that might cause the same issue.