Exhaust(ed)… the drone persists

thanks for the link. I’m gonna do something like that. Found a pic of some adjustable ones I want to build.

 

No Larry, it’s all controlled by the Holley ECU and I can tell it what I want and map it however but I’ve been trying to figure out what to set it to.

If you’ve got recommendations for timing settings for a stock 350 for start/idle/cruise/WOT I can go put those in and see what happens.

 

Correct. It’s entirely dependent on the control unit. I can connect my laptop and map it however I want for given RPM ranges.

 

I think the Holley Sniper EFI has sensors that measure flow of fuel and air, throttle position, and so on.

 

Timing, I agree with Larry, except all in about 3000RPM. Crappy gas nowadays.

 

I went out to the garage and updated the timing settings. Maybe I’m just imagining it, but I think it did make the drone less intense. Tomorrow I will put the dynomax 17749s back on because these Walkers sound crappy to me in comparison. I’m going to also go through all the connections and mounts to make sure it’s all snug and isolated. The dynomax race bullets don’t take much room or impact flow so I’ll put them back up front while I’m at it.

also, I put the 45° elbows back on the tails and aimed them down and to the sides and that actually cut drone somewhat.

 

I didn't get to the timing feature of the sniper on my old car but did do some research. The settings in the sniper software will get you in the ballpark. The cruise setting is like light load with mechanical and vacuum advance. Idle the same as the distributor initial timing and the vacuum advance. Idle timing will fluctuate to maintain idle speed. There is also a cranking timing adjustment that's like the distributor timing before vacuum an mechanical advance come into play. there's also an rpm parameter to control when it switches from cranking to idle timing control. EFIsystempros have a lot of info on setting up timing as well as the Holley forum. The best way to do it is through the software and build a custom table. I've read that using the Xflow software has some tables you can copy and just paste to the sniper software table then tweak them to suit your needs, but I've yet to look into this.

 

I must say I appreciate all the input.

I put the 17749s back on. They sound a lot better. The bullets are up front. Some stuff is touching other stuff so I need to do a better install. I couldn’t get the pipes inserted the way they should be. The muffler inlet and outlet are a little out of round and crimped from the clamps I’d used the first time so I bought a Horrible Fright pipe expander. I hope I can get this one use out of it before it self-destructs. I’ve got band clamps on all the connections now.

this week I’ll get to it.

 

I ordered an H-pipe kit that comes with two tees and two lengths of pipe.

After I adjust what’s there now to make sure there’s no place that the exhaust is touching anything I’ll use some band clamps and install it up front and see what it does for the drone, if anything, since it’s not likely to involve any cutting. If it doesn’t make a difference there I’ll use the parts to make j-pipes, which is what I’ll probably end up doing.

My back is out, wasn’t great before, but the other day I was under the car and twisted the wrong way and ouch.

 

I would look for room near the rear end/gas tank. Point them both in-board and clamp the 2 sides together.

 

I was thinking that as well, either at the leading edge or back edge of the tank. Ahead of the tank, if it could clear the rear end, it’d mean a cut to the tailpipes, probably where they head down before they head back. At the rear I could probably piece together what I have and bridge the tailpipes behind the tank, which means the tees and cross pipes would be attached where I already cut the tailpipes. Depending on where I put it, maybe the cross pipes would be 6-8” or so inches before the exits on the tailpipes. I’ll need to get under there and look.

I was thinking I could bridge them together but cap them off from each other so the sounds bounce back in reverse phase and re-enter the flow before the exits. That might leave more pipe resonance than I want, or… it just might work.

 

I say call the muffler manufacturer of all the mufflers you've tried and bitch them out.
Tell them abt the drone you're experiencing and ask them wtf...

 

Since my back is still out of whack I went out to the garage just to scope out the possibility of putting the quarter-wave resonator pipes in the back. It looks totally possible.

I hope my back gets better soon so I can get under the car and mess it up again. The car? The back? Both?

Next steps are to use the pipe expander to remove the crimps in the muffler outlet so I can get the tailpipe into it better. Then drive the car with the sound analysis app running so I can get the frequencies. Then plug that into the calculator to determine the right length for the pipe. Then see if I have the distance side to side to get them in there and meet in the middle for support. If not, I’ll offset them so they run next to each other I guess.

 

I would think side by side offset is going to be necessary to get the length you need.

 

The auto manufacturers go to great lengths to assure a quiet exhaust ESPECIALLY in their V8 powered trucks.
Copy what the manufacturers are doing on the new vehicles.
You’re jacking around with aftermarket mufflers/pipes.
I SERIOUSLY doubt you’ll be able to totally get rid of the drone, even aftermarket “direct replacement” exhaust components are louder than the OEM parts.
Most car guys don’t mind the sound of their V8 engine running and cruising down the highway