Stainless piping diameter question eg plenum

[Norbie]

Lots of people here saying stainless is no good and alloy is the way to go. Is there any reasoning behind this, or is it just a case of "that's how it's done"?

[LeeRoy]

Stainless retains heat - thats just how stainless is, however stainless is better for exhausts as it looks pretty and doesnt rust compared to mild steel. Alloy will melt as an exhaust, and is generally unsuitable.
Alloy dissipates heat - heat and alloy like to stay away from each other.
Mind you, one benefit of stainless its its non rusting characteristics, alloy can corrode. This corosion can be prevented with either laquering or spraying clear over the alloy in question or polishing it as the wax/polish will protect it.

Plus, stock manifolds are alloy - and they invest lots of $ into R+D so if they do it im sure its for a good reason

- LeeRoy

[myne]

Assuming mandrel bent, are you interested in selling a bunch of 1.25"/1.5" bends?
I'm making a turbo manifold and this would be awesome

[ReQuieM]

Just check the thinkness on the piping fist before you grab it. You dont wanna go to thin! But if its good i might be interested in some smaller bent stuff for an exhuast manifold too.

LeeRoy, Thanx for that. Looks pretty good. Do you have any results yet? I've heard alot about short Vs long. the best fact so far has been short is good for top end, long for bottom. I just wanna find a way to work out a happy medium, with a bias to low end!

[LeeRoy]

Haven't started the car yet its a project. I should have it running sometime this year i just need some time off uni and a little more money. As for results the guy who made it has made ones for lots of different cars and made one like mine for an SR20 and it actually made the guy more power than the GReddy ones. I should see some good results esp compared to stock

- LeeRoy

[Draven]

Despite what everyone says, thin-walled stainless should be fine. sure, it might weigh like 500grams more than alloy (OH NOES!), but who cares? as for heat retention.. I'd be curious to know how much of a difference that actually makes - the block/head will be radiating arseloads of heat regardless, and the alloy manifolds I've touched after an evening of heavy boosting have been far from cool anyhow.

[LeeRoy]

That is true, but another point is that alloy is easier to work as well in regards to cutting, welding, and die grinding.

[Draven]

and to accidentally punch holes in while welding

[LeeRoy]

Speed holes Draven, Speed holes...

[willwal98]

what about mis-matching intercooler pipe sizes? I've been told to use different diameter piping on one side of the intercooler to the other (don't remember what way). Couldn't really understand why. If you had bigger on the hot side and smaller on the cold side it would theoretically flow at similar rates, if they were the same the hot would get to the cooler faster but leave slower?

Any theories?

[Mr Multivalve]

Assuming mandrel bent, are you interested in selling a bunch of 1.25"/1.5" bends?
I'm making a turbo manifold and this would be awesome

I did not manage to grab any stuff that small, smallest I could get with mandrel bends would be 2". Today was my last day at the factory, so I grabbed what I could and not sure if I could get anymore now. The smaller stuff was in long straight pieces too

I would think that postage would not be too cheap sending a bunch of stainless either, plus you might get ASIO on your door step quizing you about building pipe bombs

Factories are not a bad place to check into as they always have stuff lying around that they can sell off cheap, even better when they are closing down.

[Mr Multivalve]

Just check the thinkness on the piping fist before you grab it. You dont wanna go to thin! But if its good i might be interested in some smaller bent stuff for an exhuast manifold too.

As above there was not any of the thin stuff with mandrel bends..

I think the piping was about 1mm to 1.25mm thick, it is rated to withstand 1000psi anyhow, I would love to see a turbo crank out that much boost

[ReQuieM]

draven, I was thinking the same thing. Even tho it disperses quicker, it also absorbs quicker! Well its seems like it on my IC piping and when I weld the the whole piece super heats not just the weld zone. On the flip side it cools quicker too!

Having said all tha I'm going aluminum.

Mr Multivalve thanx any way!

[Norbie]

I think you'll find manufacturers use aluminium because it's easy to cast, which means cheaper for mass production. Welding up a stainless plenum simply wouldn't be cost effective on a large scale.

Contrast this with the home enthusiast, you use whatever skills and materials you have available. If that means stainless steel, there's no real reason not to use it. As mentioned above heat transfer means SFA since it's bolted to a great lump of hot metal, so whatever it's made out of is going to get hot.