Black R

Like the topic says... I'm interested in how an equal length exhaust manifold is good for a turbo setup.....

Thanks.

B00STeD

talk to FFgeoff. He makes them and is very knoweldge-able on them.

boosted hybrid

The general theory of equal length exhaust manifolds in forced induction is to focus the sound/pressure energy of the exhaust gases through piping which directs the flow of said exhaust gases into a collector. The collector area of the exhaust manifold must be a shallow angle merge to enduce a laminar flow to the exhaust gas. The joining of all cylinders at an equal rate, with a non-turbulent flow will focus the maximum amount of exhaust gas energy into the turbine housing. You are essentially tuning the energy waves so that the collection of the waves is addition of each wave into one giant pressure wave. Its basic sound/pressure wave amplitude theory.

If this would not occur, pressure/sound waves would be traveling out of phase with each other and possibly creating almost zero energy to spool up the turbine. This would be the extreme case where the pressure/sound waves from one cylinder would travel with pressure/sound waves from another cylinder, and would follow 90 degree out of phase. The addition of both of these waves would create a net gain of zero, since they cancel each other out.

There is alot more to creating a equal length manifold than just tuning the pressure/sound waves since they are changing with rpm. The length of the runner of the manifold must be taken into consideration as well. The longer runner will enduce a higher pressure to a certain point, but energy will be lost with heat loss. Material selection such as 8 gauge 304 stainless that FFGeoff uses in his manifolds aids in creating a adibatic (no heat transfer) boundary to a certain extent in the runner design. This insulating effect of the thicker gauge steel allows to retain the energy (heat) to aid in spool up time, as well as keeping the medium (exhaust gas) high heat to aid in the pressure/sound wave propagation since the speed of sound is directly related towards temperature (higher heat, faster travel).

There is even more to manifold design including exhaust scaveging effects of a properly designed manifold to a certain extent. This uses the vacuum between pressure waves to clean the residual out of the combustion chamber. A fresher, denser charge mixture is drawn into the combustion chamber allowing for more work/heat transfer to occur. Greater work=Greater efficiency=Greater torque=Greater horsepower.

I'll leave FFGeoff cover the rest, he is much better versed at this subject than I am.

Full-Race Geoff

holy crap -- jeff your explanation kicked ***!!! haha its cool to see you thinking like this jeff, youre damn good at this engineering nonsense.

the thing that really screws everything up and shows the lack of true understandong on behalf of the general public is really that every "longish runner" manifold is considered an "equal length." A log manifold is also an equal length...

i like to refer to our manifolds as long-runner/streamlined, not necessarily equal length. The race manifolds are equal length becuase we are trying to sap up every single last tiny bit of power. I could make an equal length log manifold with equal length runners and all it will do is be turbulent in the area of the turbine nozzle (turbine housing) so the length doesnt matter. What DOES matter is to make a collector at a couple magic angles and pair the appropriate cylinders up with one another to keep insulative effects at a maximim (less heat loss). If you compare an equal length manifold with a poorly developed collector to a proper merge collector manifold, the merge collector manifold will have huge early/midrange power gains over the other non-merge manifold. There is no argument.

Also, laminar flows move air at higher pressures. Keep the flow laminar with the collector and you make power. the tradoff is that you want the pressure high with the higher runner but can lose energy due to heat through the runner. The length here is optimized for that and then optimized for the pulse tuning of the equal length. Always keep the equal lengths a close second to the importance of smooth (NOT SHARP) bends.

*Boostwerks*

So how would say a manifold such as the Revhard tubular stainless design (assuming it has a good flowing collector) compare to that of an equal length manifold with a similar collector?

Is there that much of a difference assuming both manifolds have a very nice collector?

Full-Race Javier

good explanations

also, when the primary/runner lengths are equal length and combined with a well designed merge collector, reversion is more balanced across each cylinder and is supposed to increase the engines VE (volumetric efficiency). basically, tubular/equal length manis with well designed merge collectors optimize heat, pressure, and flow. a log mani on the other hand only optimizes, heat and pressure and they have horrible flow characteristics. with the tubular/equal length manis, less energy is wasted (more energy available to the turbine) which means a faster spooling turbo

Slick GS-R

iTrader: (2)

excellent post guys, very informative

Racergurlie

The Real question I have, is it really necessary in turbo applications to have equal length?...Undoubtedly and unquestionably the two of the fastest and most powerful cars in compact racing run NON equal length manifolds...Shaun Carlsons car has a non equal length manifold and number one and number 4 pipes are probably a solid 6+ inches different in length, yet he is running 8.2 @ 183mph and the ECOTEC motors are making 1000hp and have gone into the sixes(first 4 banger in the sixes with non equal length) So the two of the fastest and most powerful 4 cylinders in existance are running non equal length...

Jury is still out in my mind. I was discussing it with Dave and his thoughts were similar, though he felt proper diameter tubing for the application and a smooth transition in the collector area minimizing velocity loss were probably much more important then equal length is, which seems to be supported by two of the most powerful and fastest 4 cylinders in sport compact racing running non equal length manifolds but both have 4 into 1 merge collectors. I'll try to find some pictures of their headers and post them up.

Alyssa Kay
Super T Motorsports

Full-Race Geoff

a lot of people dont know how to do fluid velocity calculations, and just stick the the "as small as possible is better" theory.

Racergurlie

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by FFgeoff &raquo;</TD></TR><TR><TD CLASS="quote">a lot of people dont know how to do fluid velocity calculations, and just stick the the "as small as possible is better" theory.</TD></TR></TABLE>

Raises Hand...lol... I never did do too well in Mathematics...

Heres a picture of the Carlson Mopar...those first two runners just go straight in and are about 6" shorter then the outers ...

Alyssa Kay



Modified by Racergurlie at 6:28 PM 6/17/2003


Modified by Racergurlie at 6:39 PM 6/17/2003

Charlie Moua

iTrader: (3)

damn that a good *** explanation bro. Both of you. I would love to see a turbo manifold shoot-out with different manifolds (Full-Race, Revhard tubular(non-ac) SFP, SuperT, MaxRev, ect)

keep the good info coming.

SuperTeg95

Would it matter if say 1 and 3 were the same length and 2 and 4 were the same length or overall is there no matter as to length, or just a good collector?

Full-Race Geoff

matching the appropriately paired cylinders runners in length is a very important thing. It gets you to about 90% of the pulse tune from that alone.

symmetry is found everywhere in nature for a reason

SuperTeg95

So should 1 and 4 be same length and 2 and 3 be same length?

Full-Race Geoff

if they arent all the same length, then yes this is just as good.

boosted hybrid

The reason that Shaun Carlson, or other pro import drag racers dont use a true equal length manifold is because they dont have a mechanical engineer versed in heat transfer, fluid dynamics and thermodynamics to be able to design something effective. Just because they dont use a true equal length, shallow angle merge collector manifold doesnt mean that they cannot squeeze even more power from their set-up. Truth be told that they arent many engineers in the import drag scene, FFGeoff is probably one of the only one i know of. There is a find distinction between a fabricator and an engineer in terms of design.

newspeedR

Those sound like some strong words... would you call up Burns Stainless and tell them that there Engineers dont know what they are doing...

Obvioulsy Burns knows whats going on since they built that mani, along with Kubos new mani, Carlsons as pictured, Bergonholtz, and the old Papadakis coupe header. If you look at the design, they all have the same layout since the motor runs longitudal. Burns has a special program in which they input all the motor parmaters to get the pipe lenghts. i would bet if each runner lenght was measure, they would be in the range of 20"-30" in lenght and within +/- 1" of each other...

I would almost make a bet as if the Burns design compaired to Geoffs design, if done properly, with all the correct elements selected in a FEA fluid flow and heat transient test, the results would be very similar.

I could also say that there not alot of Engineers in the industry, but there are alot more than you would imagine. And you can talk to most Engineers and they will agree, that sometimes hands on experience is more important than paper knowledge because what you want to work in theory, doesnt always prove out to be the best method or setup...

Soon_2b_evil

Whoa this thread is good. You learn something everyday. I did

Full-Race Geoff

the "special program" burns has is a Microsoft Excel Spreadsheet with a few formulas inputted for runner length, diameter and collector angle. Full Race has a very similar spreadsheet, and its no black magic, just a couple of formulas.

You are dead on right about the fact that experience has a ton to do with the design work, however experience with little understanding of the physics that is actually occuring makes for some serious guess work, and while you may still get to the same point it takes MUCH more time.

Burns didnt design papadakis's old header, HyTech did. I am also not 100% sure of the claim about the Kubo or carlson's but you could be totally right. Dont forget however, that they have to clear the shock tower...

hpfsi

Hmm.... that is a divided turbine housing no?

newspeedR

i know that HyTech had soemthing to do with 1 of papadakis's old header, but done remember which 1 it was... in the burns catalog i have here, there is a pic of his h22 coupe and says it was theres...

Full-Race Geoff

two things i dont understand about burns's stuff

1) they sell and recommend thinwall 304 for use on street cars. everyone who uses it knows it cracks... not sure how they can do this

2) they dont weld the outside of their collectors. Its mostly becuase it requires very delicate/difficult welding to do this, but cmon...

one more chance

there u go people educate yourseves...
so basicly tune edual length aid spooling and holds the pressure better...?

SiRkid

you are my hero

ffgeon

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by FFgeoff &raquo;</TD></TR><TR><TD CLASS="quote">

2) they dont weld the outside of their collectors. Its mostly becuase it requires very delicate/difficult welding to do this, but cmon... </TD></TR></TABLE> do you mean inside?