Best turbo manifold design

So in your guys opinion which is the best turbo manifold design?

I see on most stock turbo cars the turbo placed as close as posible to the exaust ports with the justification that the closer you are to the original point of the excaping gases the hotter they are and the faster they move so turbo lag is minimised....in this case the design of the tubes is unequal


But i see some aftermarket manifolds that will twist the tubes quite a bit in order to get them to be of equal lenght also I notice them to be of very different design - i guess because of the airflow they are suposed to have or engine bay clearances....

and other companies i see making the tubes quite long and placing the turbo father from the exaust ports


so what are the advantages and disadvantages of the different designs and which do you like the most?

With short exhaust tubes the exhaust will be hotter which means a higher efficiency of the turbine, the higher temperature also means higher enthalpy in the exhaust which means that we can get more power out from the turbine or decrease the exhaust pressure before the turbine and still produce the same power. Since the volume in the tubes are small the turbochargers will also have good response.

For most standard turbo cars the camshafts are too mild to offer any real disadvantage by the non equal length tubes. For hotter camshafts the tubes can be made equal.

Long tubes are sometimes used, this is mainly used on racingengines when exhaust-temperature is a problem. Due to the hotter camshafts the powerloss from non equal tubes will be larger, but there will also be a powerloss from the reduced exhaust temperature. The engine will however work better when not under boost compared with one fitted with short tubes.

To keep the exhaust energy as high as possible the tubes should keep a straight, smooth and simple way to the turbocharger. The tubes should be made of thin material with poor conductivity like inconel or stainless. Mild steel or titanium should not be used.

Heat isolation is a good idea, carboncloth can for example be used.

Peugeot inline 4 racing engine with heat isolated exhaust/turbo, the tubes seems to be quite short:
http://www.mulsannescorner.com/WR-JK5.jpg

Cadillac Northstar V8 with carboncloth/metalfoil heat isolated exhaust/turbo:
http://www.mulsannescorner.com/CadGC-4.jpg

Honda F1 engine with short straight pipes:
http://hem.bredband.net/b132378/annat/honda.jpg

Well put. Also, log style manifolds are subject to more heat stress as the pulses group together and create hot spots in the manifold. This can reduce the life of the manifold, as they are subject to far more thermal expansion than 4 into 1 designs. A 4 into 1 design allows the pulses to stay seperate much longer, creating a low expansion manifold. Shorter manifolds do allow quicker turbine response as the exhaust reaches the turbo much quicker. SaabJohan, I tend to disagree slightly with you on mild steel, while it is not the ideal material, it does have a place in certain applications. Mild steel is cheap, extremely abundant, and easy to work with, although it may require some sort of plating to resist corrosion. I would say mild steel is a good material to practice building ones own manifold with, although stainless is probably the material of choice. Mild steel can be used effectively as long as one takes into account it's high conductivity when designing the manifold. Make sure to cut the flange, separating each runner, to allow for expansion, and drill the flange bolt holes slightly larger than needed. Heat loss will become an issue if you use long, or large diameter, runners (large diameter runners also decrease velocity of the exhaust). This is because the larger the surface area, the easier it will be for heat to escape (heat transfer is related to the surface area of the material...less area, less heat transfer). So in short, keep the runners short, and prepare for expansion if you use mild steel.

In my opinion, a short runner, stainless steel, 4 into 1 manifold is ideal. But that is only my opinion. Again, well said SaabJohan.

Mild steel can not handle the exhaust temperature, it will anneal and give a deposit on the inside of the tubes. This deposit can then follow with the exhaust flow and destroy the turbine. This will soon be noticed if the engine is runned with high temperature for a longer time.

Carmanufacturers had problems with exhaust material (both manifold and turbine house) in the early years of turbocharging, mainly because of cracks. Today they use a cast iron with a high nickel content.

316L (ASTM) is a prefered material choice for tubes if inconel is too expensive.

The type of exhaust manifold we have discussed is called a impulse system, there is also a system working with constant pressure. With that system there is a chamber before the turbine where the pulses are smoothen out, that system does increase the turbine efficiency but have poor response.

thanks both of you guys for the info this is really informative..its nice to have a FI forum that its only visited by serious people and not have the bitching that goes on in the honda acura FI forum


but anyway....so the general agreement is that on regular engines the closer the turbo is to the exaust ports the more efficient will run and the faster it will spool even if the tubes are inequal lenght....
so this would be the best design for most turbo cars?:
http://www.turbodepot.com/ProductCart/pc/catalog/Hon-B16-TN.jpg


so what is the deal with all those manifold designs that look very convoluted like this:
http://www.full-race.com/products/turbo_products/manifolds/images/004.jpg
what are they trying to acomplish with a design like this? equal lenght? or something else? to me they just seem unecesserally complicated and restrictring airflow with all the bends


and about the materials used what about using ceramic manifolds...todays ceramics are very cheap very strong(heck they use them in tanks) and they can whistand insane temperatures

or another ideea that just came in my mind what about coating the inside if the manifold with carbon carbon

the nice thing about equal length headers (or manifolds, whichever) is that each pulse has the same distance to travel to the turbine. That keeps the turbine fed with a steady flow, although once you start filling the manifold up with gas it really doesn't matter.

IMO, a seperate tube for each cylinder should be used so that overall pressure of the exhaust system isn't fighting the piston or trying to push gas into it as the piston reaches TDC and back down. A twin scroll system can work well too, that way pulses don't run into each other and slow down, they're free to feed the turbine nozzle without being slowed. Equal length doesn't matter so much, just so long as it doesnt effect the pulses.

Another way to help prevent reversion is through the use of "reversion cones" (I think that is what they are called). Reversion cones are built into manifolds, just after the flange, into each runner. These cones slightly increase backpressure, but help reduce reversion.

Please elaborate on mild steel, I hadn't heard of that before, and a friend of mine is currently running a custom mild steel manifold. So far it has worked just fine. Also, a number of authorities on forced induction have recommended mild steel as a material for manifolds.

Neutrino, without knowing what car that manifold came from it is hard to tell what they were trying to accomplish. The doubled over design may have to do with placement. The number one consideration when designing a manifold is "will it fit", because if it doesn't, it wont matter how good the manifold is, you wont be able to use it.

To use carbon-carbon is impossible since the manufacturing process require heating to over 2000 degrees C, which the metal won't handle. It should however be possible to coat the inside of the pipe with a thermal barrier coating (TBC) like the onces used in gasturbines. It have been used in F1 to coat the exhaustport in the cylinderhead.

My guess is that the strange looking exhaust manifold on the picture is just complicating things.

Also, on a I4 engine cylinder #1 and #4, #2 and #3 should be paired together.

Mild steel can't handle the exhaust temperature, but most people building their own systems in this material usually don't notice this. Mainly this is because they aren't using as high exhaust temperatures as one could, or doesn't load the engine under enought time so the heat can be built up. But it has happend that turbochargers have lost their turbineblades, mild steel in the exhaust manifold can be one of the reasons for that.

Is it possible to ceramic-coat or teflon-coat the inside of a mild steel manifold? If so, will it help it to withstand the temperatures?

And could someone comment on this setup?

http://www.nissanperformancemag.com/april02/images/fmax3.jpg

To use carbon-carbon is impossible since the manufacturing process require heating to over 2000 degrees C, which the metal won't handle. It should however be possible to coat the inside of the pipe with a thermal barrier coating (TBC) like the onces used in gasturbines. It have been used in F1 to coat the exhaustport in the cylinderhead.

My guess is that the strange looking exhaust manifold on the picture is just complicating things.

Also, on a I4 engine cylinder #1 and #4, #2 and #3 should be paired together.



isn't there any other process that would alow that....like a chemical bonding.....

ans what about certain aloys that can handle 2000 degrees C those paired up with a carbon-carbon coating would whistand insane temperatures....of course this might be redundant since if the gases ever reach that temperature the engine would be melted already

but what about the use of ceramic (not just coating, the entire manifold made of ceramics)



Neutrino, without knowing what car that manifold came from it is hard to tell what they were trying to accomplish. The doubled over design may have to do with placement. The number one consideration when designing a manifold is "will it fit", because if it doesn't, it wont matter how good the manifold is, you wont be able to use it.

both those manifolds in my pics are aftermaket manifolds for hondas...i've gotten them of the web....the first pic is much closer to the standard stock manifold design for I4's and seems better since the turbo is very close to the exaust....the second manifold however is a very common (aftermarket) design i've seen for many cars and i don't think its main purpose its for clearance since it does not acomplish more in the turbo position that the firts design



and ales i know quite a few headers are ceramic coated so i don't see why you could not coat mild steel...how much it will help however i don't know

Polytetrafluoroethylene (Teflon) can only handle temperature up to around 260 degrees C.

Ceramic coating can be used, but it is expensive. Also if the coating is done on mild steel the deposit could build up under the coating causing it fall off. When ceramic coating is used the bonding layer is very important, since it must protect the coated material and even out the differences in thermal elongation.
In any way, to spend money on an expensive coating and then use it on mild steel is just a waste of money, it's much better to spend it on inconel tubing.

Carbon/Carbon is made from carbon fibre and a special polymer matrix. Then the part is heated so only the carbon atoms will be left in the material.

Ceramics are brittle, have poor tensile strengths and are usually sensitive against thermoshock. In other words, to make an exhaust manifold in this material will be difficult.

Ceramics are brittle, have poor tensile strengths and are usually sensitive against thermoshock. In other words, to make an exhaust manifold in this material will be difficult.


latelly the ceramics are getting way better....heck even tanks use ceramics nowadays for armor....the brits have a ceramic tank that is suposed to be tougher even than the depleted uranium M1 Abraham


so something that is designed to take eplosive penetrating missiles is for sure not brittle or sensitive against termoshock.....


also if i'm not wrong there are some ceramic turbos out there right?

so i don't see why not use a material that can be way cheaper but even more resistant than iconel for manifolds

latelly the ceramics are getting way better....heck even tanks use ceramics nowadays for armor....the brits have a ceramic tank that is suposed to be tougher even than the depleted uranium M1 Abraham


so something that is designed to take eplosive penetrating missiles is for sure not brittle or sensitive against termoshock.....


also if i'm not wrong there are some ceramic turbos out there right?

so i don't see why not use a material that can be way cheaper but even more resistant than iconel for manifolds

The tank is using steel reinforced with ceramics (MMC) and tungsten rods (could be tungsten carbide, I'm not sure). Since steel is used it will help against the downsides of the ceramics, also, in a tank the most important properties are hardness and toughness and ceramics have the first.

Ceramics have become better but they are still more or less sensitive against thermoshocks. They are also brittle and have low tensile strengths and toughness. Ceramics have a diffrent atomic structure than metals and this will give them some drawbacks that we can't get rid off.
The low heat conductivity of some ceramics are also one of the reasons to the sensitivity against thermoshocks, but some caramics have a high heat conductivity like SiC and those are suitable as high temp. engineering materials.

Engineering ceramics are not cheap and to manufacture a manifold from ceramics will be very expensive and difficult since we'll have to sintering a very complex shape. The finished result may also weight more than a manifold of inconel.

There are some turbos that use ceramics in the turbine, probably SiC, but as it seems now these have not become a success, the same thing goes with ceramic turbine blades in gasturbines which still use ceramic coated nickel based superalloys. Even tho the superalloys starts to melt at 1300 degrees C, gastemperatures over 1600 degrees C are used.

Ceramics are used as tank armor BECAUSE they are brittle. The ceramic shatters, thus absorbing the energy from a bullet, missile, etc. If the tank was hit repeatedly in the same spot, it would become vulnerable. Likewise, if you made a ceramic egg for yourself, crawled in and rolled off a building, the egg would shatter, absorbing the impact and you would (hopefully) be OK. That said, when that mani got hot, it'd be real delicate. Stick to steel with a ceramic coating.

how good are the thermoshock proterties of zirconia? I've been seeing knives made out of them, but I don't know if they'd be a good material to make a manifold out of.

The thermoshock properties of zirconia are quite good, that's one of the reasons it's used for turbine parts.

Brittle materials are not good energy absorbers. If you want a material that can absorb energy you should choose one with high toughness. When a brittle material fail of fast fracture it's not because of the material have absorbed energy from an impact, it's because the impact have released the internal energy in the material, just like when popping a baloon with a needle.

Since those ceramic reinforced steels are very hard and have a high youngs module the bullets will not penetrate, they will bounce off instead with almost all their energy intact.

so why are race cars designed to disintegrate on impact? why does bullet proof glass form a shattered cone 2 inches deep when hit with a bullet?? why are bike helmets designed to crack on impact??? Why do cars have crumple zones???? Because as these things break, they absorb the energy. In fact, these applications involve forces that are often beyond the atomic strength of any materials known to man, or like in the case of a bike helmet, the helmet must protect something very soft and delicate, so not only must the helmet aborb an impact, but it must also do it without transmitting any of the force to the skull, making just a very hard shell wont work, so you have look at other things.

Actually, racecars are designed to desintigrate on impact, not because the desintigration absorbs energy, but for a different (but similar reason); during a crash, all peripheral parts are designed to leave the cage, leaving only the cockpit. This is because, as the parts leave, they take kinetic energy with them, making it much easier for the central cockpit to slow down. There is none of the parts absorb energy, they take it with them as they leave the cockpit, it is the wall that he hits that will be absorbing energy. Secondly, bulletproof glass is not brittle, the bulletproof part isn't even glass. Bullet proof glass is a polycarbonate material, sandwiched between two peices of ordinary glass, the glass does nothing to absorb the impact of the bullet. The polycarbonate in the center is not brittle either, illustrated by the fact that it bends to the shape of the bullets trajectory, without shattering. The shattered part of the cone, is the glass, not the polycarbonate. Crumple zones have nothing to do with the impact strength of a brittle material, crumple zones arent made out of glass, they are made out of metal, and the metal is not brittle. The metal is exactly the opposite of brittle, and crumples in order to soften the blow, and aid in slowing the transfer of the cars kinetic energy. If cars had "shatter" zones you might have a case. Also, in bicycle helmets, it isn't the hard, brittle material that absorbs the shock, it's the styrofoam used to line it. The styrofoam does the same thing as a crumple zone, it slows the transfer of kinetic energy, so that instead of a massive shock, you get a smooth energy transfer. And to conclude, your name is Peeface...nuff said.

my second post didnt use the word brittle at all. so I thank you for reinforcing my point. but your post lacks anything remotely scientific. when anything breaks, its because a force is overcoming the electrical energy that is holding its particles together - that is what gives anything its "strength". everything is therefore brittle to an extent, with things like brittleness and strength being a continuum, not a threshold. And yes, the process of breaking a material requires or "absorbs" energy, sorry I like to use proper words, not words like "take away" because you can't "take away" energy, remember? The kinetic energy of a crash, or bullet is either used up "absorbed" breaking the material, then transferred to the material itself as kinetic and heat energy as the pieces fly off, hopefully protecting whatever you want to protect. The point I'm making is that using the destruction of a seemingly weak, brittle, not relatively strong, whatever you want to call it material is far more common (ironic as it sounds) in high impact applications than just using a superstrong material. especially when protecting people (which are quite soft) the relatively weak, brittle, whatever material is sacrificial. so I hope you can understand all this, its a little more complex than your explanation, and I quote, "as the parts leave, they take kinetic energy with them" what is this? grade 6??? how does it feel to get schooled by a guy named peeface???

You never did use the word brittle, but by drawing a comparison between strength and brittle materials you implied it. Energy is never merely "absorbed", it is transformed into another form, or transferred to another object. Braking a car tranforms kinetic energy into heat energy. If a material "absorbs" energy as you say...what happens to it? it just dissapears? You ridicule the way I explained energy transfer, yet it was exactly correct. The extraneous peices leaving the cockpit DO take kinetic energy with them. So that peices with high amounts of kinetic energy (engine, and other heavy parts) are removed, leaving a cockpit with a far lower net kinetic energy, leaving less energy to be transferred when the cockpit hits a wall. This way the cockpit may survive an impact at a far faster speed than the whole racecar as there is less energy to be transferred upon impact. I don't see what is subpar about that explaination. The fact of the matter is, all of your analogies were fundamentally flawed, the key to protecting a person from a high impact situation is to slow the transfer of kinetic energy by cushioning it. It is obvious that it is the rate of tranfer, not the means by which it is done, that is harmful to a human being. This becomes obvious when one examines a simple analogy, a car decellerating from 100 kmh to 0 kmh in 10 seconds will exert the same net force on the operator as a car decellerating from the same speed, to the same speed in 1 second. It is only the speed at which the driver transfers his kinetic energy that is harmful (if he transfers his kinetic energy in 10 seconds, the transfer of energy will be much less violent than in 1 second). Tell me, if the use of brittle materials is so prevalent in impact protection scenarios, why do stunt men use air bags in free fall stunts? Wouldn't the use of a brittle material be better, as it would "absorb" the energy of his free fall? In your theory a plate of glass would be safer than an airbag, as breaking it would "absorb" his kinetic energy. Please provide a valid example of a brittle material being used to soften an impact.

*sigh* well where to start? I'll go over the whole energy thing first. My use of the word "absorb" is not wrong, maybe simplistic, but not wrong. I used it only for brevity and did not suggest in any way that the energy just dissappeared, like you tried to suggest:

"If a material "absorbs" energy as you say...what happens to it? it just dissapears?"

if anything, your explanation in your first post was much too vague:

"as the parts leave, they take kinetic energy with them"

This statement could easily be taken to mean that energy was simply dissapearing, which we both agree can't happen. But even still, I made provisions to further explain my use of the word "absorb" by saying:

"breaking the material, then transferred to the material itself as kinetic and heat energy as the pieces fly off"

...which is perfectly sound scientifically. To this you replied:

"Braking a car tranforms kinetic energy into heat energy."

Thats the exact same thing I said. So, in a weak attempt to discredit me you paraphrased everything I said in slightly different terms. But yet I'll tip my hat to your debate skills, you'd be surprised how often that technique works, but it won't work on me.

Second, I still dont know where you got this fixation on the word "brittle". If you read my first post, you'd see I was only illustrating how a brittle ceramic could be used effectively as armour, more so than a superstong material. that was one specific example. The overall theme of my posts, and I hate to repeat myself, is simply this and I quote, "The point I'm making is that using the destruction of a seemingly weak, brittle, not relatively strong, whatever you want to call it material is far more common (ironic as it sounds) in high impact applications than just using a superstrong material. especially when protecting people." Now, that statement does not only include brittle materials, but materials that might be considered weak, (in a car crash, even steel is weak when faced with the massive forces, as evidenced by wreckage after a crash). So, what I'm saying, and I'm going to say this plainly because you seem to always miss this, is: Properly engineered, a system that is designed to gradually absorb an impact but break in the process, is in many cases favorable to a system that is made of superstong materials that are designed not to break at all. brittle is only part of it! Because, under some circumstances a brittle material would work quite well. thats it!

So, in reference to the post that started it all, I HIGHLY doubt that a tank could take a missile blow and not show any damage. In reality, any damage to its armour is evidence of its protection of the main chassis/occupants. The comparison was between materials that are destroyed as a means of protection and superstong materials, because destructive protection is much more practical for ALL the examples BOTH of us gave. The fact that the original example of the tank used a brittle ceramic has little bearing on the main point which I stated many times now.

Finally, in your last attempt to find a flaw in my arguement, you say some stuff about slowly absorbing and impact is favorable to quickly stopping it. hoo boy. you serious??? HELLO MCFLY!!! Thats what I've been saying all along! The stuff breaks, it slows down gradually, your chest/skull/balls survive. If you stopped instantly, like if you were surrounded by somethng designed NOT to break, you'd have a lesser chance of survival. but that goes without saying. So, welcome to the winning team! Where've you been?? So, once again, and I swear to god this is the last time I'll say it, my comparison was between the merits of destructive protection and non-destructive protection, not some wacky alter-dimension where glass and pottery is king.

In saying that, your airbag analogy beautifully descibes the benefits of a gradual slowdown, but nothing is broken. I wont comment because it falls into a different, but very important catergory of impact stoppers. We have, I have anyway, compared materials that crush and shatter to absorb with materials that that do not at all and survive by sheer strength. The airbag is neither, it changes shape, but is not destroyed by the impact. so I wont comment on it much, except to say the airbag sounds perfect because it absorbs gradually, but is not destroyed (sounds perfect) however application of such a device is limited because it takes a very large airbag to stop a body safely, there isnt much chance of building a car that could bounce off walls and drive away (of course you know this, I'm just saying it to make a point), but the airbag has proven useful for stopping skulls from smashing into steering wheels. The bumper is faced is far greater forces and a simple airbag wont work (not yet anyway) yeah.

Polycarbonate (Lexan) as well as aramide fibers (kevlar) are good on absorbing energy, not by being brittle but the opposite. Polycarbonate is also quite impressive since if we increase the velocity of the impact the greater its impact strength will be.

A crash structure of a car is based on two things, energy absorbating structure and a protecting structure. The protecting structure is strong and stiff and its job is not to deform. The energy absorbing structures job is to deform and therefore absorb the kinetic energy (by converting it to heat). In a race car the protecting structure can be carbon fibre or a high strength steel roll cage. The absorbing material can be aluminum honeycomb and and a polymer like nomex.

If you test a few materials how the can resist a fast impact, for example diffrent steel types, you will find that the harder the steel is the less energy will be absorbed when it breaks. Some very tough steels may not even break, they will resist the impact.

In armour you want the materials to be hard and tough since that will make them most resistant against impacts. Steel will provide toughness and ceramics will provide hardness.

Most of this basic information can be found in a good book in engineering materials.

When it comes to impacts where humans are involved you usually talk about "three collisions". The collission itself, the collision between human and interior and the collissions of the human organs. It have been found that the g-forces can be seriusly reduced if we doesn't have any collission into the interior of the car, that's why a seat belt and airbag will help.

There are many ceramics now that have excellent thermal shock resistance: boron nitride, fused silica (not useful in this application), mullite, sialon, silicon nitride, silicon carbide, zirconia, etc.

Plus, I can't wait until they make thermal wrap out of silica aerogel.

Second, I still dont know where you got this fixation on the word "brittle". If you read my first post, you'd see I was only illustrating how a brittle ceramic could be used effectively as armour, more so than a superstong material. that was one specific example. The overall theme of my posts, and I hate to repeat myself, is simply this and I quote, "The point I'm making is that using the destruction of a seemingly weak, brittle, not relatively strong,


one way to protect humans from impacts is trough the spread of the impact over a larger surface.....this is why helmets shatter.....the shattering effect is not just to absorb the energy but to spread the energy over a larger surface....this is how you survive a bullet with a vest....you still absorb the entire energy of the bullet but its over a larger surface(or course in this case the kevlar wont shatter like in the case of a helmet but the same principle aplies)


so the point is that those materials are not meant to be britle or weak but to spread the energy....those materials are meant to be strong and part of their strenght is the fact that instead of facing all the impact energy in the colission point it dissipates it along its structure




oh and btw 454catsul there is a temal wrap made out of aerogel but its meant for humans (its a winter jacket) made by some designer in italy and cost something like 4 grand :naughty:

one way to protect humans from impacts is trough the spread of the impact over a larger surface.....this is why helmets shatter.....the shattering effect is not just to absorb the energy but to spread the energy over a larger surface....this is how you survive a bullet with a vest....you still absorb the entire energy of the bullet but its over a larger surface(or course in this case the kevlar wont shatter like in the case of a helmet but the same principle aplies)


so the point is that those materials are not meant to be britle or weak but to spread the energy....those materials are meant to be strong and part of their strenght is the fact that instead of facing all the impact energy in the colission point it dissipates it along its structure




oh and btw 454catsul there is a temal wrap made out of aerogel but its meant for humans (its a winter jacket) made by some designer in italy and cost something like 4 grand :naughty:
Yes, I'm aware of that jacket. But it has not yet been adapted to higher temperatures as of yet; pity, because I'm sure it can handle the temperatures of an exhaust manifold.

Oh, and Kevlar helmets don't shatter.