Stainless v Mild Exhaust Systems

[one_and_only2004]

Do you really need a 3inch exhaust for a cammed car?? or is 2.5ich with good set of extractors and high flow cats enough?? wether it be S/S or M/S

i no this isnt the perfect thread for this question but while there is people looking at this who know what there talking bout, im gonna ask.

So cheers in advance for those who give me there two cents
Chris

One of my friends has the same car as me 100% identical bar colour PLUS I have a 2.5" twin exhaust and he has a 3" twin exhaust. I'm going to get the same cam and tune done by the same mob of people on mine, So I'll let you know at the end of the week if there's a difference.

 

[Vt_vic]

twin 2.5 is good upto 400rwkw or so ive heard but itd go the twin 3 for the sound and ive never seen a stainless exhaust that needed rewelding even burnout cars

 

[Reaper]

stainless steel is the same thickness as Mild steel on exhuasts!

to the person saying their mates are endlessly welding their cracks. have they attached their exhuast system with steel hangers instead of the rubber hangers?
i have not heard of any top brand name exhuast with stainless cracking, even mine...

@VS.5L different people will have different answers to that, but i reackon twin 3" is better myself.

The problem is with the welding. Welding stainless steel draws the carbon in the tube to the heat source where it deposits like a fault line next to the weld. This makes a brittle spot in the tube. Add some work hardening due to exhaust movement and you find cracks appear next to the edge of the weld in a lot of cases.

Welding stainless is easy. The trick is to do it with minimal heat which keeps the chances of cracking to a minimum. I presume the more expensive professionally built systems are fabricated with higher class welders who do a better job in heat management.

Also, you may find the mufflers are of thinner material with the input pipes being the same as m/s. Mismatched thicknesses also make welding difficult when it comes to thin gauge materials.

Reaper

 

[Not_An_Abba_Fan]

Stainless exhaust tube is thinner than mild.

Stainless may not convect heat as well as mild but it retains it making it hotter and better flowing. We did a temperature test on both mild and stainless on the same car, I can't remember what the exact difference was, but it was substantial.

 

[Reaper]

Stainless exhaust tube is thinner than mild.

Stainless may not convect heat as well as mild but it retains it making it hotter and better flowing. We did a temperature test on both mild and stainless on the same car, I can't remember what the exact difference was, but it was substantial.

However when it comes down to actual hp gain/loss over the other option???

Are the larger stainless tubes also thinner??? By that I mean 2.5 - 3"??? I'd be very surprised if they were as (particularly the 3") it gets very difficult to mandrel bend without ongoing quality dramas.

Reaper

 

[VN_Luke]

However when it comes down to actual hp gain/loss over the other option???

Are the larger stainless tubes also thinner??? By that I mean 2.5 - 3"??? I'd be very surprised if they were as (particularly the 3") it gets very difficult to mandrel bend without ongoing quality dramas.

Reaper

I'm pretty sure most people that use 304/316 stainless for exhaust will be running #16 pipe - which is roughly 1.6mm wall thickness... I dunno what they use for mild, I suppose the same? If they use thicker walls, then it could give a sound difference, and a weight difference.

 

[Reaper]

I'm pretty sure most people that use 304/316 stainless for exhaust will be running #16 pipe - which is roughly 1.6mm wall thickness... I dunno what they use for mild, I suppose the same? If they use thicker walls, then it could give a sound difference, and a weight difference.

Back 10 years ago when I was in the industry it was all 1.6 for both mild and stainless. Most of the s/s was 304 although some went for 316 for that extra wank appeal. No idea what is in the mufflers though. Getting the 3" in particular to bend nicely was a challenge as a lot of the imported stainless tube varied in ductility even within it's own length. The Australian made STM tube was pretty reliable though. I have no idea if things have changed or not. Good luck getting #18 (1.2mm wall) 3" stainless to bend with any sort of reliability.

Reaper

 

[VN_Luke]

Are you talking press or mandrel bends? I just buy all my mandrels Pre bent and glue them together I've press bent some stainless and it came out nice and crinkle tastic!

 

[Reaper]

Are you talking press or mandrel bends? I just buy all my mandrels Pre bent and glue them together I've press bent some stainless and it came out nice and crinkle tastic!

Mandrel. You can press bend anything really . Weather you buy individual bends or a complete system - 90deg + s/s at 3" can be a right bitch if the tube is crap.

Reaper

 

[Boonz]

heyyyyyyy reaper, when i did my exhaust on the ute, ended up going with stainless full fibreglass packed mufflers, the thickness of the steel was 2.1mm according to the boxes they came in, and the 2.5 inch 316 stainless tube was 1.8mm.

is there usually a set thickness for stainless exhaust tubing or can thicknesses vary depending what manufacturer makes it?