equal and unequal manifold differences

[markey b]

apart from the obvious, if i was to have a manifold made, similar to the ktec in design, but unequal length, what are the possible outcomes? will it be

a) worse that the std manifold
b) lose the signature sound (i dont like the sound of the ktec as it sounds like a campus)
c) anything i've more than likely overlooked

a friend has offered to make me one in his spare time at work, so i'm not gonna turn it down, but what could the possible performance gains/losses be?

[Adam 005]

i would think you will lose that gt sound with any type of tubes manifold

[Mudslinger]

without doing back to back tests on the same car with 3 diff types of manifold ie standard, unequal and equal its kinda a hard to know for sure :)

imo ,if your going to the hassle of getting 1 made its got to be an equal length job , id doubt very much that having a tubular manifold will give much benefits on its own, when u think that the fastest q/m time 5 is running a standard manifold .

as for the signature sound being lost , i cant really notice the difference i still think mines sounds the same as it did before i changed the manifold.
maybe some of the peeps that were at the rr day at motoscope may have a diff opinion ??

[Mudslinger]

http://uk.youtube.com/watch?v=F9VPJxU4QUo

make your own mind up :)

[Purple_rob]

Great vid by the way ;)

[Nayls]

pretty sure equal length will defo lose the sound,

unequal will prob still sound different as it might not be the same un-equalness lol

[Rob@Backyardracing]

You may have dif mani pressure in each runner depending what cam/lap you have.....

[markey b]

You may have dif mani pressure in each runner depending what cam/lap you have.....

std cam at the mo, i do have a CTM one but not to sure if it will make my car undrivable and i dont want to loose torque.

manifold is basically gettin made in tubular because its going to cost feck all, and will make it easier to mount my WG. i just looked at the ktec and its the equal bit on cyl one that looks like it gives the most greif when it comes to clearance, and i just want to keep it simple lol

silly as it sounds, i'm not worried about making more power, just dont want to loose any.

[Markey Mark (BD)]

std cam at the mo, i do have a CTM one but not to sure if it will make my car undrivable and i dont want to loose torque.

When you say CTM cam, do you mean the one Mike Spencer use to get them to grind for him? If so i use that cam too and it didn't make it undrivable at all.

[markey b]

When you say CTM cam, do you mean the one Mike Spencer use to get them to grind for him? If so i use that cam too and it didn't make it undrivable at all.

aye, isn't it a modded 285? i have no spec on it whatsoever, so dont know what it does, whats its equivalent to, if i'll need certain springs, vernier etc?!

if you have any info it would be really appreciated :)

[Markey Mark (BD)]

aye, isn't it a modded 285? i have no spec on it whatsoever, so dont know what it does, whats its equivalent to, if i'll need certain springs, vernier etc?!

if you have any info it would be really appreciated :)

I believe he moddifed a 285 cam (not sure what the spec was as standard), it used the piper springs and vernier it can with but i think we had the valve seats machined down alittle bit on the head if i remember, think it was because of the lift and it would of compressed the spring too much.
I had the head and cam here alittle while ago so could of checked but have sold it on now.

[Scoff]

ordinarily If I were building a tube manifold for a high boost c1j I'd keep each runner as short as possible to keep the volume down. likewise you shouldn't be tempted to go over kill on the pipe diamater, keep it the same or not much larger than your exhaust ports. having said all that with a VNT it maybe isn't as important anymore because you are no longer after keeping hold of every last bit of velocity to spool a big turbine. instead equal length runners might be a better option because you may be more concerned with making good peak power instead. as mudslinger rightly says you just won't know what's what until you try it, but rest assured it'll make a gnats cock's worth of difference either way.

[Theros]

I have other information then...

We are building exhaust manifold where tubes are same in lenght. Diameter is only little bit bigger than in original manifold.

I spoke with the guy who building parts to race cars. His opinion was that speed of gas flow and equal lenght is important thing when designing exhaust manifold.

[Scoff]

I have other information then...

We are building exhaust manifold where tubes are same in lenght. Diameter is only little bit bigger than in original manifold.

I spoke with the guy who building parts to race cars. His opinion was that speed of gas flow and equal lenght is important thing when designing exhaust manifold.

I agree but the requirement changes with different applications. making it equal length means that you have to make some runners longer. this means that gas has more time to cool and more material (tube) to sink the heat away. original manufacturers keep manifolds as short as they can to keep turbo responce at a maximum. If you have a big turbine then you probably want to keep it as responsive as you can - making runners longer does not help this. but, if your only goal is to make good horsepower (for a race car) then like I said before you might want to use equal length runners. I'm still sure it won't make much difference though :)

[Scoff]

I should say that I'm only talking about the C1J engine which needs the turbo positioned above the gearbox. If I had an engine that I could fit a turbo directly above or below the exhaust manifold then it would be nice to use an equal length manifold with short runners, that would be about ideal.

[Theros]

I should say that I'm only talking about the C1J engine which needs the turbo positioned above the gearbox. If I had an engine that I could fit a turbo directly above or below the exhaust manifold then it would be nice to use an equal length manifold with short runners, that would be about ideal.

Yes...I am speaking about C1J engine too. We made all tubes equal in lenght. We changed "collection" pipe a little bit. To fit same lenght tubes we moved turbo little bit forward and to right.

I try to add torque for low rpm. Problem that we might meet is pressure at exhaust side of turbo. It might grow too much (of course high boost is one reason to that too).

I remember that in Renault 5 Turbo 2 is very thin exhaust manifold tubes, but those pretty long and same in lenght. That surprise for me...according to owner that exhaust manifold was original...

[Scoff]

It's only my belief, ofourse I may be wrong but with the C1J I really think equal length is a waste of time. the maxi's nice crossflow engine had a lot more horsepower, 300hp +, it was more important to get everything right. the maxi ran a big T3/T4 which even considering its high boost pressure it probably had less exhaust manifold pressure than a gtturbo running 25psi from a T25.

remember it also has a lot to do with the camshaft design. the gtt turbo (even with its peformance camshafts) typically has very little overlap meaning that exhaust design isn't that important. the maxi had a much wilder camshaft with a lot more overlap. it was tuned more like a powerfull NA engine because it had such a big turbine. with a wild camshaft you might need to think more about exhaust manifold design and so equal length becomes a lot more important.

[Theros]

It's only my belief, ofourse I may be wrong but with the C1J I really think equal length is a waste of time. the maxi's nice crossflow engine had a lot more horsepower, 300hp +, it was more important to get everything right. the maxi ran a big T3/T4 which even considering its high boost pressure it probably had less exhaust manifold pressure than a gtturbo running 25psi from a T25.

remember it also has a lot to do with the camshaft design. the gtt turbo (even with its peformance camshafts) typically has very little overlap meaning that exhaust design isn't that important. the maxi had a much wilder camshaft with a lot more overlap. it was tuned more like a powerfull NA engine because it had such a big turbine. with a wild camshaft you might need to think more about exhaust manifold design and so equal length becomes a lot more important.

That is truth too.

Equal lenght don't affect to power that much in turbo engines as it does in non-turbo engines. Also type of engine is one major reason.

I have T25, 285, adjustable vernier pulley, uprated valve springs, max size valves, twin choke weber and so on... so I think that it will help in my case more than usually. Downpipe is only 2,5", but it made differently than original...because of space...

[Scoff]

sounds like a good setup :)

[Os8472]

So end of the day what ya saying is, with an N/A engine you need an equal length manifold, on turbo'd engines with high overlap you need equal length jobs but in the case of a C1J that doesn't have much overlap, the fact that the standard manifold is unequal and with a VNT on the end of it then an unequal would be ok, have I got that right?

[Theros]

So end of the day what ya saying is, with an N/A engine you need an equal length manifold, on turbo'd engines with high overlap you need equal length jobs but in the case of a C1J that doesn't have much overlap, the fact that the standard manifold is unequal and with a VNT on the end of it then an unequal would be ok, have I got that right?

Yes you have got it right.

I almost forgot. That might minor thing, but it is important to keep in mind that cylinder #4 won't work most efficient way, when there are standard exhaust manifold. Reason to that is only lenght.

Equal lenght will add some power, but not 20 bhp or so. Standard manifold is compromise between power / torque area and max power / max torque. If you want to increase maximum (and gain little bit extra power), then you should change exhaust manifold.

About noise (as someone asked about it earlier). Turbo will definitely damp noise, so changing turbo might affect to noise too.

[Theros]

sounds like a good setup :)

Thanks. I think that I will get over 200 bhp.

[Os8472]

Just spoke with the chap whos building the unequal job and had a look at some pics, gotta say it looks great, its only tacked together at the mo so the positioning can be made perfect but its well on the way:D

[Theros]

Just spoke with the chap whos building the unequal job and had a look at some pics, gotta say it looks great, its only tacked together at the mo so the positioning can be made perfect but its well on the way:D

Send me some pics? tero.oksala(at)gmail.com

I will post pictures from my exhaust manifold (equal lenght) when it is ready :)

[markey b]

pics in projects under my 'winter jobs' thread