cast iron? Many years ago when tubular manifolds starting pooping up. I noticed a couple things i didnt like. The engine compartment heat was greatly increased when running a tubular manifold. Some cracked and needed periodic rewelding. And when coated the coating tended to flake off due to high expasion and cool rates of stainless. I had a coversation over the phone with a guy up in new jersey that noticed the same thing. He measured engine compartment temp. with the stock cast manifold and them again with a tubular stainless manifold. The highest he saw on cast was 175. But on the tubular he saw temps at 325. At the time i wasnt at all surprised as i had noticed how much hotter everything in the engine bay was just from taking for a test spin then lifting up the hood. I have no idea where he was measuring temps from or how. i didnt ask.

This led us to the conversation that stainless is a poor material to make a turbo manifold from. In my college days i had a cast iron cooking pan. I used it regularly until one day i decided to buy a new stainless cooking pan. the first time i cooked eggs i was shocked at how much more heat was needed to cook. stainless does not "hold" heat . It passes it easily. cast iron holds heat much better.

So with that why not make manifolds from tubular cast steel pieces instead of SS? Those schedule 10 and schedule 40 pipe sections that many use are available in cast steel and are cheaper to boot. They could be coated with ceramic when done. Since they dont cool as fast as stainless they would be better at keeping heat out of engine compartment and into the turbo where it can make torque.

 

i guess you could look at this both ways.
We've found that on the dyno, if you have a "cold" cast exhaust manifold and do a power run, it will be down on power, about 10 to 15%. And it will spool slower. This is because the heat from the exhaust is partially being absorbed by the cast manifold (same goes for steampipe/steel too). If we do another power run directly afterwards, the results are "normal" with that 10-15% regained.
With the stainless steel manifolds, the power is much more consistant, regardless if the manifold is "cold" or "hot". Obviously this is because the stainless steel doesn't like to absorb the heat as much as the cast or normal steel, and is disperses the heat more quickly.
I guess the same thing could be said for inconel.

Now with that in mind, wouldn't a Thick stainless steel manifold thats correctly heat shielded and coated (with something that doesn't flake) work well?

Does the same topic work for Cast Stainless steel manifolds?

To talk about your question, with cast steel sections to make a manifold, is cast steel hard to weld? because of it's heat absorption properties?

lol you said pooping

 

weight

 

Care to expand?

 

how bout titanium?? then you wont have to worry about it cracking!

 

Mike, there are two ways to tune your car using a dyno. One you can tune car on dyno and then drive on street and see how you did. Or you can tune on street and then put on dyno to see how you did. Not gonna argue which is better but I always use the latter. On the street the cold manifold syndrome lasts one pull. After that the normal driving keeps the heat up.

There are several good posts of people removing cheap stainless manifolds and going back to stock cast and picking up enormous gains. 80tq on 400 hp car. And there are even some posts now of good quality manifolds not doing what they are touted to do. Then in the next post someone will pop in and say the manifold did make HP on their car so the new results should be read as faulty. Much of this discrepancy comes from the heat factor and the parameters within the testing Stainless manifolds that put a lot of heat into the compartment are not so much an issue in 50 and cooler weather. but its a huge problem in 80 and up weather. especially if intake is such that it can suck that hot air into the intake on a pull. here again dyno pulls done 20 minutes apart with the hood up can swing these downfalls to an unseen condition.

There is a huge problem of gathering data using other poeples posts. The whole picture of how data was gathered is rarely seen.

 

I'm waiting till someone makes this manifold that the DSM guys had for years:

http://store.forcedperformance.net/m...de=DSM-Exhaust

The Evo has been out for 7 years now in the US and no one made one yet

 

The heat capacities are very similar, but cast iron has a much better thermal conductivity than SS. That simply means that it will take a bit longer to heat up as it is distributing the heat more throughly throughtout the entire metal piece.

The ability to 'hold' heat as you mentioned also deals with the total heat capacity and the thermal conductivity. The cast iron actually will cool down quicker due to it's higer thermal conductivity, per unit mass, as compared to SS. But, since cast iron pieces are usually much thicker, the overal heat capacity of the cast iron piece is much greater, so it will take longer to cool down and 'hold' the heat better.

But I do agree with your points on wanting a cast exhaust manifold rather than thin walled SS tubing. No need for all of that heat going into the engine bay. A thick cast piece that can conduct the heat efficiently throughout will help keep the engine bay temps down, while still retaining the heat inside. But, it will take a bit longer, as you mentioned (a run or so) for the temps to stabilize.

 

Revhard makes a manifold like that in a t3 flange for the Evo. It's flanged for a 38mm wastegate. Someone need's to make one in a t3 twinscroll.

 

I have a similar manifold design made by FP but mine is not DS5 material, Its SS. The version i have is discontinued though..

 

Dude, the OP's typo's are priceless:

"nayone"
"pooping up"

Anyhow, a few guys I knew back in 2001 had the same thought pattern as the OP. There's a product that was called "Weld-Els" and they welded up a t3 manifold for a GSX out of these Weld-Els. It worked well, it was just heavy as a brick and flowed like junk. But you'd have had to use a jack hammer to crack the thing.

 

Do you mean cast steel and not cast iron? There is a slight difference, as the cast steel has a carbon content under 2% where cast iron can have much more carbon. The carbon content changes the materials strength and likelihood for carbon precipitation at high temps. For this application, the lower the carbon content, the better.

Stainless steel is going to conduct LESS heat into the engine bay then cast iron/cast steel with a similar surface area. The reason the stainless pan took more heat is because stainless is LESS conductive and it was impeding the energy flow from the burner to your egg. This is a good thing for an exhaust manifold as it keeps the heat IN the gasses in the runner.

Cast iron and cast steel will experience carbon precipitation at the temperatures an exhaust manifold reaches. This hardens the metal from the inside out due to the carbon rich exhaust gases in the runner. You are basically carburizing the inside of the runner every time you start the car. Stainless has alloy materials that stabilize the metal at elevated temperatures and help prevent carbon precipitation.

As ugly as the stuff is and "how bad" everybody says it is for metal, the fiberglass wrap does a great job of keeping the temps down. I built a 316L manifold (schedule 10) and wrapped it with the fiberglass insulating tape. That manifold has somewhere around 50k miles on it now without an issue. It has been ran in SLC where the city pours on the salt and sand on the road in the winter. The fiberglass supposedly traps this junk and causes corrosion, but that's also why I went 316L over 304 since it is more corrosion resistant to salt spray.

Many of the ceramics have also been reformulated in the last few years to better deal with the higher coefficient of expansion of stainless steel. Some companies are pickling stainless before applying the coating which insures a better bond. Further, a few companies also use a bond layer that reduces cracking by being an expansion buffer that helps reduce the strain rates in the ceramic material due to the difference in the coefficients of expansion.


Oh, one last thing, 316L and 304L stainless pipe elbows (weld-els) are actually cheaper than their steel counterparts. I would imagine it's because they make a lot more stainless ones then steel since the properties of stainless are so much better for so many industries.

*** Almost every manifold on the market that isn't known to crack like crazy uses weld-els. The thin wall stuff cracks not because of it just being thin, it's because when you go thin wall, you can not rely on the manifold supporting the weight of the turbo and it is critical to isolate the exhaust movement from the turbo system to prevent large stresses. To do this, a GOOD turbo support is needed that allows movement for expansion but carries all the weight of the turbo. The exhaust needs to have a good flex joint located in the correct spot to prevent bending moments from being placed on the exhaust manifold.