exhaust dumped at diff.

[LJDB 103]

I recently took the rear section off my TE Cortina and dumped the system at the diff. Its hi tech extractors into 2.5 with 1 cheap looking muffler. Its not overly loud but has a drone. Im thinking of adding a hotdog or changing the muffler. What people thoughts on a muffler and hotdog before the diff or any good mufflers that wont be to loud and still flow well on there own. 

[PRO250 1,506]

I never dumped the pipes in my corty but the drone you can stop by stepping the pipe size down at the back

ive tried hotdogs and ive found they make the drone deeper id be keen to hear anyone elses thorts as well

[Stu5766 394]

I have twin 2.5 inch power flow mufflers. I had to fit a couple of 12" hotdogs to the system to quiten it down some. I found the hotdogs took away a lot of drone & a few Db aswell.

In saying that, it isn't dumped at the diff.

I've. Ever been a fan of exhaust dumped under the car.

It creates the drone & boom that you are suffering from.

[gerg 10,871]

A resonator before the main is what manufacturers use to kill the drone but placement is very important. It's really hard to get right. I have 2 x BA Falcon resonators about a foot after the collector and about 2 feet before the main ones. It drones between 1700 and 2000 and fitting a crossover didn't cure it. It could be fixed by maybe going up in pipe size between the resonators and mufflers (which slows down the flow) but only when I get a chance..

 

Droning can also be a result of a certain volume inside the cabin that resonates like a giant subwoofer enclosure at certain frequencies (rpm). This and the fact that dumping under the car is a sure-fire way of turning it into a giant boom box. The floorpan vibrates from the pulses under the car and becomes a big speaker.

 

Mine is a wagon so has no buffer zone (ie boot) to cancel some of the sound out. Sedans are obviously better but dumping under the back seat has the sound source closer to the cabin and will create sort of the same problem as a wagon or hatch.

[wagoon 2,429]

The angle of the dump also comes into play as a turn down will be different to a straight horizontal exit. I know my xy that was dumped at the diff with turn downs would make rear seat passengers fell sick if cruising at the same speed due to the effect Greg mentioned. To fix it I had a rear section put into the system so can't tell you about adding mufflers to remove the drone

[bear351c 10,270]

Yep, in my Clevo ute, I had to fit 10" hotdogs after the diff, to stop the drone. (Pipes exit @ 45* just under the bumper. Cant be seen from behind.)

[LJDB 103]

I cut the angle that did go over the diff and re welding it upside down as a dump slightly angled towards the rear quarter almost like a side pipe/dump. the hotdog I have is quiet heavy so not sure if I should add it as theres only one hanger in that area. I took the rear section off as it was 2 1/4 over the diff and at the bends it looked tiny and restrictive, Cortina has a weird exhaust route along drivers side up over and along the diff then out the passenger rear . It also sounded like shit at the rear

.

[slydog 7,873]

Give it enough engine so it sounds tuff out the back  Compression takes care of the droning. 

[gerg 10,871]

Yeah my Corty was the same, had a really annoying sound even with the stock 2" pipe and I deleted the rear resonator. When I went to straight gas, I took out the tank and had the pipe run straight out from over the diff outbthebdriver's side into a hotdog before the tip. It was a good system that had presence but was quiet on the highway.