Is there a reason exhausts arent solid mounted?

Jack91 · 04-09-2014, 10:05 PM

Hi all,
In a couple of weeks I will be attempting to make a twin 2.5inch exhaust from the extractors, dumped at the diff, for the fairlane. Reason being is that I'm comfortable welding it myself, and I cant justify the ridiculous price of buying one premade, when all it will take is 2 bends and a slight mitre or two. Now, seeing as this is a very budget build, for time and money, its going to be a lot easier for me to solid mount the exhaust off rails/bars rather than buying and bending rod and rubber hangers. I figure I will have a flange at the extractors, and another before the curve over the diff.

Unsure at this time whether I will use stainless or mild steel, it will depend on the price difference. Obviously stainless is going to be a little trickier to weld, and should withstand heat better without distorting as much as mild steel. However, I'm doing it on the car while its on stands, so getting the torch into the tight areas to tack could be tricky.

Any advice greatly appreciated

**cs123** · 04-09-2014, 10:08 PM

For a start the engine vibrates and moves. This will break the welds if solid mounted.

Jack91 · 04-09-2014, 10:10 PM

God, Im an idiot.
Thank you! Answered it in one.

zilo · 04-09-2014, 10:15 PM

You can buy a flexible coupling which is inserted around the firewall area if you are determined to make it solid.

You could flange it, most front wheel drives have one as the motor rolls forward and backward with torque.

EA2BA · 04-09-2014, 10:17 PM

Just put in solid engine mounts as well ......

FPV+fteT3 · 04-09-2014, 10:18 PM

Solid mount would transfer a lot of heat into the floor area and noise and vibration would enter the cabin area.

esppwr · 04-09-2014, 10:30 PM

Google thermal expansion and you will understand why not to

Bossxr8 · 04-09-2014, 10:30 PM

It would resonate into the body quite badly you'd imagine, and everything would probably buzz.

**Polyal** · 04-09-2014, 10:39 PM

And they bottom out alot too..so that wouldnt be great.

Jack91 · 04-09-2014, 10:39 PM

Thanks everyone. Ive just discovered I can get the rubber things for around $10 each off the internet machine, so its not as bad as I thought anyway. But if anyone has any tips on the actual forming of the exhaust, feel free to share.

2011G6E · 04-09-2014, 11:14 PM

Why not?

This is why not...you wouldn't believe the vibrations this hillbilly-made exhaust "system" made in our old WB ute when I was driving it home all the way from Wondai to Bluff. It was pressed up hard between the frame and the springs at the back, and solidly and tightly chained to the floor in a couple of other places...no movement at all, and even though the engine is a sweet and smooth running little 253, it ran like it was bolted to a tractor engine with something badly wrong with it.

And yes...you will notice there's no mufflers either...quality workmanship!!

Jack91 · 04-09-2014, 11:40 PM

That does look pretty crapola, I reckon I can get my bends and my parallelism of the pipe better than that.
Whats wrong with no mufflers?
Issue with no back pressure? Or you just mean the amount of noise?
Im going to run without them first, but I'll leave enough straight section to fit a couple of hotdogs if required.

2011G6E · 05-09-2014, 12:17 AM

Quote:

Originally Posted by Jack91

That does look pretty crapola, I reckon I can get my bends and my parallelism of the pipe better than that.
Whats wrong with no mufflers?
Issue with no back pressure? Or you just mean the amount of noise?
Im going to run without them first, but I'll leave enough straight section to fit a couple of hotdogs if required.

Mainly the amount of noise...have you ever been in a car with no mufflers? Really? I notice you said "dumped at the diff"...just be prepared for a brain numbing drone as you drive along and a staggering amount of fines while attracting the attention of every cop within a kilometer...

Mufflers actually make your engine run better, surprisingly...

Franco Cozzo · 05-09-2014, 01:59 AM

I heard my Falcon drive into the exhaust shop with just the pacies on it.

Most annoying LOUD farting noise ever.

LoudPipes · 05-09-2014, 02:02 AM

Is it legal to dump an exhaust on a 4 door at the diff?

2011G6E · 05-09-2014, 02:09 AM

Quote:

Originally Posted by Big Damo

I heard my Falcon drive into the exhaust shop with just the pacies on it.

Most annoying LOUD farting noise ever.

Yes, a car with no mufflers at all is not a pretty sound is it.

I still have an AutoSalon magazine from several years back that had a "street car of the year" issue where contestants in modified imports had to pass a long series of tests. They included a roadworthy, a brake test (from cold, not allowed to warm up your special racing compound brakes first, to replicate real world situations on the street like driving away from your house in the morning and having someone back out of a driveway in front of you...some of the cars with huge competition brakes and special pads were shocking...they simply wouldn't stop unless the brakes were hot first), some other reliability tests (such as not overheating in traffic), and a noise test where they had to pass a standard noise meter check as you would have done if pulled over.

The winner was an R32 Skyline, putting out a reliable 700hp. Amazingly through a cleverly designed exhaust system it was actually quieter than the regulation decibels that a testing mob would demand.

It is possible to have a nice note and a free flowing system...loud doesn't equal powerful...despite what Harley riders sometimes think...

Quote:

Originally Posted by LoudPipes

Is it legal to dump an exhaust on a 4 door at the diff?

I think we all know the answer to that...

LoudPipes · 05-09-2014, 02:19 AM

Quote:

Originally Posted by 2011G6E

...loud doesn't equal powerful...despite what Harley riders sometimes think...

It just sounds awesome
351 Cleveland

Al_Zhiemer · 05-09-2014, 10:39 AM

Quote:

Originally Posted by 2011G6E

Yes, a car with no mufflers at all is not a pretty sound is it.

I still have an AutoSalon magazine from several years back that had a "street car of the year" issue where contestants in modified imports had to pass a long series of tests. They included a roadworthy, a brake test (from cold, not allowed to warm up your special racing compound brakes first, to replicate real world situations on the street like driving away from your house in the morning and having someone back out of a driveway in front of you...some of the cars with huge competition brakes and special pads were shocking...they simply wouldn't stop unless the brakes were hot first), some other reliability tests (such as not overheating in traffic), and a noise test where they had to pass a standard noise meter check as you would have done if pulled over.

The winner was an R32 Skyline, putting out a reliable 700hp. Amazingly through a cleverly designed exhaust system it was actually quieter than the regulation decibels that a testing mob would demand.

It is possible to have a nice note and a free flowing system...loud doesn't equal powerful...despite what Harley riders sometimes think...

I think we all know the answer to that...

WOW... I still have that very same magazine in my collection somewhere, by memory it was a burgandy coloured R32?? I use to refer mates of mine regularly to this article right after they got defect notices to prove my point that you don't need to be illegal to be fast...

People seem to think that if its not making a lot of noise, then it can't possibly be fast or making horsepower... Commodore mentality, stock pieces of crap with straight through noisy exhaust but its the fastest thing around...

Exhaust pipes must exit the vehicle past the rear most opening windows, so no, dumping them at the diff is not legal...

And as stated, the NOISE!!! My good, many years ago when I first fired up the XW with the new 351 Clevo in it, we never worried about bolting on the rear tail pipe section and went for a 45 min blast down the highway... Couldn't hear a thing from the noise and the drone, started getting carbon monoxide poisoning... We had to pull up at a servo, buy a box of panadol and sit it out for an hour before we were up to the challenge of driving it home

Regards

Crazy Dazz · 05-09-2014, 04:39 PM

What we perceive as noise from an exhaust is pressure waves created by the discontinuity of the gas flow. There are many complex actions at work in an exhaust, including resonance, however the primary purpose of a muffler is to smooth out those pressure waves.
In theory, if you had enough space, you could almost nullify the exhaust sound without creating back-pressure. In practice, it is a compromise.
A straight-through muffler will arguably give you better flow and therefore marginally better performance over a straight-pipe. Probably 3/5's of SFA, but it will be significantly quieter.

I don't know how it works in other states, but in WA, provided you have the requisite components the car will pass roadworthy unless those components are RADICALLY different to factory standard. Even though my rear muffler has been replaced with an after-market (and it sounds like a lawn-mower) my Terry still passed because it HAS a muffler.

Point is, equipping your car with NO mufflers is going to be intolerably loud, and you can forget about taking it anywhere near a public road. I reckon we could run a pool on how long you can keep it on the road before it gets stickered.

Recently I have had to start and move my old AU which has nothing from the CAT back. It wasn't just loud, it was hold my head and moan LOUD, like somebody banging on my head with a hammer.

XB GS 351 Coupe · 05-09-2014, 10:40 PM

Quote:

Originally Posted by Jack91

Any advice greatly appreciated

Take it to exhaust shop.

Fit mufflers.

Don't dump at diff.

Don't solid mount.

mik · 05-09-2014, 11:11 PM

stainless is not bad to weld, but its not as much fun to work with, stainless also has a different sound to it, i have had mine for about 9 years, its good not worrying about the exhaust rusting out.

Crazy Dazz · 06-09-2014, 01:11 AM

Quote:

Originally Posted by mik

stainless is not bad to weld, but its not as much fun to work with, stainless also has a different sound to it, i have had mine for about 9 years, its good not worrying about the exhaust rusting out.

Depends on the quality of the stainless. I recently worked on the construction of a desal plant which used a lot of stainless. Unfortunately it was apparently "cheap stainless from China" and it was rubbish. Way too soft (kept splitting) and difficult to weld.
I previously thought that provided it had the correct ingredients all stainless would be similar, but apparently it also has something to do with the way it is annealed, rolled, and tempered.

Crazy Dazz · 06-09-2014, 01:15 AM

Quote:

Originally Posted by Crazy Dazz

It wasn't just loud, it was hold my head and moan LOUD, like somebody banging on my head with a hammer.

And yeah, it wasn't like "Rock On" loud, it was more like "WTF is wrong with your engine?" loud.

pottery beige · 06-09-2014, 09:17 AM

diff dumpers are cool on first start up under carport

first drive

you will hate it

dudes in back will hate it

you will hate it

and all that louds and no pipes out the back is gimme for po po

NTF6 · 06-09-2014, 02:10 PM

Quote:

Originally Posted by Crazy Dazz

Depends on the quality of the stainless. I recently worked on the construction of a desal plant which used a lot of stainless. Unfortunately it was apparently "cheap stainless from China" and it was rubbish. Way too soft (kept splitting) and difficult to weld.
I previously thought that provided it had the correct ingredients all stainless would be similar, but apparently it also has something to do with the way it is annealed, rolled, and tempered.

I find stainless steel a dream to weld if using the correct rods for the type of stainless:

304 general purpose everyday stainless (kitchen equipment, bench or counter tops etc)

316 resistance to acids and alkalies (acid manufacturing)

309L for high temperature (kilns and furnaces) doesn't stay shiny and turns dark brown to blackish after exposure to heat and water.

Plus heaps of others. I like the way a good weld on stainless and the slag just curls up and falls off by itself.

Crazy Dazz · 07-09-2014, 09:16 PM

Quote:

Originally Posted by NTF6

I find stainless steel a dream to weld if using the correct rods for the type of stainless:

304 general purpose everyday stainless (kitchen equipment, bench or counter tops etc)

316 resistance to acids and alkalies (acid manufacturing)

309L for high temperature (kilns and furnaces) doesn't stay shiny and turns dark brown to blackish after exposure to heat and water.

Plus heaps of others. I like the way a good weld on stainless and the slag just curls up and falls off by itself.

It depends on purpose and Yeah to be honest it probably doesn't matter for an exhaust.
In the project I was on the pipes had to hold phenomenal pressure, and the welds all had to be x-rayed and signed-off.

**Mesa** · 08-09-2014, 10:14 AM

Quote:

Originally Posted by 2011G6E

It is possible to have a nice note and a free flowing system...loud doesn't equal powerful...despite what Harley riders sometimes think...

I think we all know the answer to that...

Apparently it's a safety feature. You can buy Harley Davidson tops now that claim that 'Loud pipes save lives'.

2011G6E · 08-09-2014, 10:44 PM

Quote:

Originally Posted by BluFGXR6

Apparently it's a safety feature. You can buy Harley Davidson tops now that claim that 'Loud pipes save lives'.

Not from the factory they're not...they're like any other modern bike, as quiet as mouse flatulence.
Those shirts are old as the hills. I somewhat agree with the sentiment, but as I said, there's a huge difference between a nice note and an annoying noise...but many people are really interested as to how Harleys are the only vehicle on the road which can remove it's muffling system completely and run straight pipes and face literally no legal problems from the Plod...very puzzling...

Franco Cozzo · 08-09-2014, 11:24 PM

Also rotary engined cars, when they've got huge ports they sound like a whipper snipper from HELL at like 130db.

mik · 09-09-2014, 03:45 PM

Quote:

Originally Posted by pottery beige

diff dumpers are cool on first start up under carport

first drive

you will hate it

dudes in back will hate it

you will hate it

and all that louds and no pipes out the back is gimme for po po

never heard that term before( i dont get out much), is that because the pipes stop at the diff ? i used to have stag pipes on my 67 xr, they jumped the diff and did a sharp turn coming out behind the back wheels, same or different ?