As title. I always thought mild steel was stronger and could handle heat etc etc better without cracking. That right?

So if so, why are all these tubular manifolds made from stainless that always crack, are a bit dodgy to use with ALS, etc etc?

If they can handle the heat better some fairly thick wall mild steel would be idea for manifolds wouldnt it?

2wd Cossie manifold can handle tons of abuse, though it has inconel in it IIRC so its not the best example, granted...

 

Stainless looks more Bling of course... God thought you knew your stuff

 

Thats the only reason i can think of, but im hoping (or not) there more to it than that.

Id MUCH rather have mental ALS and just no cracking manifolds in general than some blingy bollocks!

And besides, i bet mild is loads cheaper

 

MUST be a good reason mate....

 

Remember, this is the car tuning world tho mate, itd not suprise me if it was just for bling reasons!

Race jobs are inconel, which is deffo better, but stainless, hmm.

 

...surely having a car that runs and drives is better?

 

phil, who bought yours/rhys old saph?

pretty sure it was on track at combe on sat... didnt look that quick either... must be the home built engine

 

...its got his own engine in mate not mine...the DIVA has my diy engine

 

I got 3 cars like that at mo.

Anyone have a clue about this question? The way nobody knows makes me think it is just for blingy "buy this as its pretty" reasons...

 

Stavros, the answer is simple. You CAN have a mild steel but no-one bothers as the cost of making a manifold is all in the labour. And Stainless is supposed to last longer etc...

To make one from mild would be about £100 less in materials...

Hope that helps mate

 

Oh right. Thought mild could take the heat better etc. Well there you go.

 

This is from Burns Stainless (who make pro racing exhausts) They don't even mention or sell Mild but do have 2 different Stainless Steel tubing.

304 stainless steel tubing combines excellent physical properties with a remarkable resistance to corrosive agents found in automotive exhaust emissions.
304 tube is the most cost-effective grade of nonmagnetic stainless steel for general applications, but some professional racing teams use the higher heat-resistant properties of aircraft grade 321 stainless steel.


321 stainless steel tubing is one of the most desirable materials for exhaust systems because of its excellent resistance to fatigue and cracking at elevated temperatures.
It is usually the material of choice for high temperature turbo applications, unless extreme requirements indicate the use of Inconel.


625 Inconel, containing approximately 60% Nickel and 22% Chromium, was developed to cope with the extreme heat and strength demands of jet engines.
Molybdenum and Niobium elements also contribute to 625’s strength at temperatures greater than 1800º F, where 321 SS is unsuitable.
Inconel 625 excels in applications such as Rotary engines and extreme duty turbocharger exhausts.

 

nothing wrong with mild steel

 

mines made from 321 according to the stamp on it.

certainly not shiney, looks brown

then again it is rather old

 

Is it any better at not cracking than stainless tho?

Just looked at melting points, stainless is a little lower but thats still over 1400degC, so that side of it isnt the major issue i guess.

 

oh yes steve,,,, the stresses dont build up so much in mild steel

 

So some nice thick gauge mild steel would be a pretty good call.

Or is there other disadvantages with the stuff?

Passionford- Makes learning fun

 

it conducted heat well,,, which we dont really want

but this can be sorted with coatings

 

some grades of stainless resist stress cracks alot better than others aswell

 

Mild steel is stronger than stainless but it's also heavier, i think it rusts too but im not 100% sure.

 

Conducting heat well- you mean mild?

Ceramic coating- can this be used on the inside of manifolds, and does it last hard use ok?

 

yes its done on the inside, and regards hard use, i reckon about every 6-12 months you need to recoat it. Look at the rally cross cars.

A few people on here have had ceramic coating done and been suprised how short it lasted, and that was with mild heat, not ALS or hard hard use.

 

yes i mean mild steel conducts heat well,,, remember we want to keep all the energy we can for our turbine

ive go no person experience of coating on manifolds,,, but genrally they are great

of cause there downside to mild is,,, RUST,, but coatings will sort this aswell

 

thats the thing see ryan, 12months hard use with frequent clicks of the ALS switch would be ok for most modded car owners if it could last that, but sounds like it cant.

 

if the coating is done right,, it should last for aslong as the manifold

BTW have you ever had a car ON THE ROAD for longer than 12 months? i know my cossie havent

 

well everyone seems to do it wrong then. know anyone who can do it right?

 

Yep Coating will help loads!
no longer than 12 months? isn't that when the rust sets in

Actually, my first year ownership of my 3dr I drove it just about everyday for 12months.. that includes the snow (even drove it to Canada from NYC and back without fault )