Progress Thread My 79 Coupe Is Alive.

[General karthief]

I have a theory about the dreaded drone in our cars
It's the back pressure

 

[BMW Rider]

I don't know enough about exhaust noise dynamics to say for sure if the muffler location will lessen the drone. Hopefully your right. I will have to see what the decibel levels are from the car for competition requirements, if they are higher than acceptable, I may cut in some resonators in the original muffler locations to help.

 

[02 281 GT]

I did some internet "research" a while back and found that drone isn't really a function of muffler placement so much as exhaust system design itself. Stock mufflers are usually so large because they have resonating chambers which cancel out the troublesome sound waves which cause drones. They're specifically tuned to each application by manufacturers. Universal mufflers obviously have not had this taken into consideration.

One means of dealing with this in custom applications would be the installation of quarter wave resonators to cancel out the sound waves that cause drone. Various things have to be taken into account in order to determine the correct length of pipe you should use and where in the exhaust system.

Some light reading:
Problem - Exhaust drone: Solution side branch, aka 1/4 wave resonator, or Helmholtz resonator
The Quarter Wavelength Rule And Why It’s Important To You
Killing exhaust drone with 1/4-Wave Resonator Tubes
Exhaust Drone is Completely Gone
How to build an exhaust resonator tube to eliminate drone

 

[BMW Rider]

Made the new panel for the passenger door successfully today.

Yesterday I decided to make a handle for the park brake to match the shift knob I made some time ago.

And lastly, a cover panel in the trunk to block off the quarter panel pocket. The other side is all ready blocked by the battery.

I think that's it for the aluminum work now.

 

[Noobz347]

I did some internet "research" a while back and found that drone isn't really a function of muffler placement so much as exhaust system design itself. Stock mufflers are usually so large because they have resonating chambers which cancel out the troublesome sound waves which cause drones. They're specifically tuned to each application by manufacturers. Universal mufflers obviously have not had this taken into consideration.

One means of dealing with this in custom applications would be the installation of quarter wave resonators to cancel out the sound waves that cause drone. Various things have to be taken into account in order to determine the correct length of pipe you should use and where in the exhaust system.

Some light reading:
Problem - Exhaust drone: Solution side branch, aka 1/4 wave resonator, or Helmholtz resonator
The Quarter Wavelength Rule And Why It’s Important To You
Killing exhaust drone with 1/4-Wave Resonator Tubes
Exhaust Drone is Completely Gone
How to build an exhaust resonator tube to eliminate drone

Those are good ones. On our cars, chambered mufflers are the biggest culprit. Changing the length of one side of the exhaust, or other, can often help (referring back to the first item in your reading list).

You can move the drone up or down the rpm range by changing the exhaust length (or even the length of the muffler chambers).

This brings a question to mind:

How many folks have really bad drone with long tubes?

 

[General karthief]

No drone at all

 

[95BlueStallion]

My theory on less drone because the mufflers are in the back is that generally the mufflers are what cause the drone. Having them way in the back helps keep that noise out of the car by letting it be muffled by the trunk, back seat, etc.

 

[95BlueStallion]

Made the new panel for the passenger door successfully today.

Yesterday I decided to make a handle for the park brake to match the shift knob I made some time ago.

And lastly, a cover panel in the trunk to block off the quarter panel pocket. The other side is all ready blocked by the battery.

I think that's it for the aluminum work now.

Love the work youve done with the aluminum. May not be the most ideal for a daily driver, but its not a daily driver. Party on Wayne

 

[BMW Rider]

The next item on my hit list of tasks was to deal with a couple of annoying oil leaks. The first was easy, just a rear axle seal. The differential I got had a small ding in the end of the tube, and although I worked it out, it was enough of a deformity still to allow the oil to get past the outside of the seal. I pulled the axle and seal and used a coat of sealer to fill the gap with a new seal. Since I had the cover off, I added a new TrickFlow aluminum cover with support studs for the bearings. And of course I prettied it up with a bit of paint.

Next oil leak was a persistent one from the back of the oil pan. I had changed the gasket once all ready trying to stop it with no luck. I had jacked the engine up and dropped the pan to do it, but it was still way too tight to work at and see what was going on. This time I decided to pull the transmission out so I could see just what the heck was the problem. I was using the one piece pan gaskets and it was obvious that the pan just was not sealing around the bearing cap. I had decided to go with the old style four piece gasket this time. I used a light smear of RTV all along the two end rubbers as an additional measure. Got it all back together today and so far no sign of any leaking.

With the transmission back in, I was now able to finish up putting in the shifter boot and the console. Last task was to fabricate a transition piece from the dash to the console.

All that's left to do inside now is mount the fire extinguisher.

 

[95BlueStallion]

Not to nit pick, but did you make the center of your dash raised on purpose?

 

[BMW Rider]

Not to nit pick, but did you make the center of your dash raised on purpose?

Yes, it was to follow the line at the windshield and to allow for the defroster ducts.

 

[eighty5fox]

im loving the theme of this car very clean and well put together

 

[RaggedGT]

No radio?
Love the aluminum interior

 

[BMW Rider]

No radio?

Nope, sound system is under the hood.

 

[BMW Rider]

Last couple weeks I've been picking away at some minor detail items. Installed a Longacre rear view mirror and made up a small Plexiglas visor and put the roll bar padding on.

I had some rings to use for the visor, but did not like how they fitted up for that, so after making the rod to mount the visor to the mirror arm, I used the rings to mount the fire extinguisher instead.

I spent a few days building some tools for doing the alignment too; caster/camber gauge, bump-steer gauge and some turn plates. I need to move the car off the lift and into the other bay of my garage to do the rest of the setup but winter keeps happening and making it impossible to move the car outside to make the switch.

 

[BMW Rider]

A couple other items that I finished up.

Exhaust tips welded on

Windshield banner applied.

 

[General karthief]

Ok, so where is your stangnet sticker?

 

[95BlueStallion]

Its coming along. Have you started it up and sat in it running since youve finished the interior? Curious of the rattle situation?

 

[BMW Rider]

Ok, so where is your stangnet sticker?

I guess I need one, but I'd be adding it to the collection on my tool box, I will be keeping the car clean of decals (though I did add a small Ford oval decal on the top of the rear window too). The window banner was mainly to fill in the black out band at the top of the Optic Armor windshield.

I have had the car running a little, no rattles that have be detected thus far, but some driving time would do better at revealing any.

 

[stanglx2002]

Last couple weeks I've been picking away at some minor detail items. Installed a Longacre rear view mirror and made up a small Plexiglas visor and put the roll bar padding on.

I had some rings to use for the visor, but did not like how they fitted up for that, so after making the rod to mount the visor to the mirror arm, I used the rings to mount the fire extinguisher instead.

I spent a few days building some tools for doing the alignment too; caster/camber gauge, bump-steer gauge and some turn plates. I need to move the car off the lift and into the other bay of my garage to do the rest of the setup but winter keeps happening and making it impossible to move the car outside to make the switch.

Can you please post the plans for the alignment tools you built please....

I can't trust these guys at the shop with my car and have always wanted to do it myself. With my OCD I would have to make it perfect. I am tired of the outside part of the tread of the tires getting worn out so quickly.