Mazdaspeeder

So I'm having a manifold made for my 1.8 EFR6258 setup. Since it's being made by Abe from ARTech, I have a lot of faith in the product, but I was just wondering why one would choose to use Stainless vs Mild or vice versa. Mine is a top mount equal length setup.

I've searched and found tid bits of info, maybe someone can educate me further.

y8s

iTrader: (8)

stainless looks nicer and has lower heat transfer out of the manifold.

mild is cheaper and (anecdotally!) is rumored to not crack as easily. my personal anecdote is in agreement and I've only got 40,000 miles or so on my mild steel long tube...

hustler

iTrader: (6)

I'd go with the one that is known to last longer...where are the enginerds?

Mazdaspeeder

Mine is being made from Mild and I was going to have it either Ceramic or Jet Hot coated. The things some said is if the finish flakes, that area can rust, which I suppose is true. However, I don't know how likely the finishes are to flake off. I wanted to spray it myself, but I hear it's better if the coating is done inside and out, so I might take it to a powdercoater and have them do a more thorough job with the Jet Hot.

This is for a street car, so i doubt I'll be getting the stuff hot hot on a regular basis.

aaronc7

iTrader: (8)

Abe made mine, and he went with mild due to certain bends that were needed, etc., only being available in mild steel. Everything I have heard matches what y8s said... I just got mine ceramic coated locally, and it's been holding up great. I tried the spray on stuff before that- it actually held up quite well against the heat, but it is far less durable than a proper ceramic coating. I'd recommend spend the extra money to get it ceramic coated, and get it done right away, before there's time for any rust to form. If you do go the spray paint route...just follow the directions to a T, and it will work pretty well (bake in oven, etc. etc.)

miatamike203

Stainless steel has a higher coeffincency of thermal exspantion, mild steel is much lower. Witch is the reason stainless manifolds crack easier.

Leafy

iTrader: (1)

Stainless is better than mild in every way for this application, except one small thing. 304 stainless has better high temp mechanical properties, it has a lower heat transfer coef, it has a lower thermal conductivity, it has a higher heat capacity, it doesn't oxidize as bad (but still does). The downside is the coef of thermal expansion. As long as the manifold is either designed strong enough that it wont fatigue fail from the thermal stressing or designed so that there is minimal stress due to the expansion it shouldnt crack. On my manifold I really didnt feel like spending months in the fea software running insane simulation to try to figure out the exact perfect places to put the bracing on my manifold so that I could use 16ga stainless instead of sch40. Mainly because it would have only been a couple pound difference. So I built it with sch40 with the expectation that it would last at least 3 years without cracking.

Mazdaspeeder, pay the extra money and get the swaintech true ceramic, it wont flake off unless you chip it off with a hammer or rocks or something. Its what my manifold and downpipe are going to be coated with, its not terribly expensive.

My current struggle on my manifold is that I'm trying to find 304L sch40 1 1/4 180* returns. If I cant I'll just have to make 3 more welds on the manifold so its not a huge deal, but it would make the manifold look better. Random info the L in 304L means that it has a max of 0.03 carbon and is easier to weld, stuff listed as just 304 has a wider range of allowable carbon.

y8s

iTrader: (8)

If I were doing it all over again, I'd go with mild (again) and swain. my only issue with my manifold is the flaky coating. I don't mind that it wont be shiny silver.

Mazdaspeeder

So basically mild is fine here as long as coated? Some made it seem like I pulled an uber fail, others said that mild+coating=SS in price and I should have gone SS instead. When I said some of the guys here actually prefer mild, I was told you are the minority. This isn't to bash anyone, I'm really just trying to learn.

If you know more, plz chime in as I'm sure this has been asked before and will be asked again

Leafy

iTrader: (1)

I wouldnt leave any manifold uncoated.

Mazdaspeeder

To do the swaintech, does it have to go to them or do you know if other places do it? Timing: manifold is going to be coated before it even goes on the car.

Leafy

iTrader: (1)

Has the go to them.

Mazdaspeeder

Is the swaintech that much better that it's worth the extra cost and hassle of shipping, etc.

Leafy

iTrader: (1)

Yes. Swaintech is an actual ceramic, like like pottery. Jet hott and the like are just a paint with a ceramic additive. Its better than normal paint but it'll still flake off eventually and doesnt keep the heat in as well as the swaintech. Swaintech doesn't give a rating to their exhaust coating but according to the tech, you'll melt the steel out of the manifold before you damage the coating.

This is the specific coating http://swaintech.com/race-coatings/r...aust-coatings/ And supposedly there is another company in the US that does true ceramic coating, not sure if they do car parts though.

Mazdaspeeder

Sucks that it's white but I can paint over it I guess

Just wondering why you would still choose to go mild vs SS? A local guy who used to have a shop that did lots of fabrication said

"$700 is a lot for mild only because a SS version would be in the $800-$1000 range. Not worth the savings in my opinion. Either way it's a lot of work so the price is justified. I've dragged, road raced, and auto-X'd SS tubular manifolds so they've seen very high EGTs / heat cycling and have never faltered. All the top fab shops in the country use SS so i'm not sure why he's going a different route. In the end, it will work, but for $700 plus the cost of ceramic coating, you're in SS manifold $$. Just odd, that's all."

y8s

iTrader: (8)

Ask the race guys in the race section. I just have had good luck in my application.

hustler

iTrader: (6)

You don't race the car so it's certainly more reliable.

Mazdaspeeder

My application is backroad action, for 100 mile highway trips to the shore and such, and maybe some street shenannigans.

Is white lightning inside and out? Dont you need inner coating for moisture and such?

y8s

iTrader: (8)

then my 40k mile proof is your puddin. I did a couple track days but nothing hardcore. you probably won't get into boost for the same length of time as on track so the stresses are much lower anyway.

viperormiata

iTrader: (24)

Mild