Critique this Intake Manifold
 

A few months ago I had an intake manifold made. Rob at Flipside Customs based it on the one he's currently offering. It has a larger plenum and a custom flange to allow me to use a specific throttle body. I would like to hear some honest feedback on what others think of the manifold itself as well as the logic behind those thoughts. Thanks.

Disclaimer: I am no expert in fluid dynamics, etc.

But, it looks like cyl#1 would be starved for air with most of it going to the cylinders furthest from the throttle body :dunno:. This is just by going with how *I* imagine the air flowing. I think runner#1 is too close to the TB.

I went through the same thing while making my own manifold. That's one of the reasons I had the velocity stack protrude into the 'flow'. But, who knows, yours might be awesome while mine completely sucks...

--Ferdi

It looks good, I have one of the intakes for the 1.6L still have not had the chance to fully install it nor tune it. It looks expensive though lol

Critique it??
I want to make love to it:giggle:

I would have to agree that it has an issue withCyl.#1 not having sufficient airflow.Also the finish of the velocity stacks could be smoother.I dont have pics of mine,The v-stack is a smooth,polished transition all the way to the head.
(G)

I would like to see a fluid dynamics expert on the subject because I will be starting my mani build soon. I would have to go with ftjandra on this one, from all I have read up on the subject and talked to others that make them as well.

I'm curious about the transition between the plenum and the runners. It looks like there's a sharp lip that could be smoothed out.

Friends-ftjandra is one sharp cat,and If I was building a first intakeyou could do alot worse from stealing a design.(G)

I bet this manifold will work better than the stock one for you, but Im sure there are better ones out there.

So more importantly, what do the before and after dyno charts look like?

Without CFD numbers, our opinions are worth about as much as the machining debris. But IMO the runners are way too short.

This.
But FWIW, I also think flow to #1 might be kinda odd..

i'm just curious, how would an intake manifold work if its same design as a twisty exhaust? Perhaps even more it so its pointing up and its in the middle and have the throttle body up there as well?
http://trendgears.com/ebay/TacoTacoN...M4TD05-001.jpg

http://images.gasgoo.com/MiMgIzY2NzE...o-manifold.jpg


i donno just trying to think outside the box on something new..

Im fairly certain the reason behind that manifold is to have fairly equal length runners, with an intake it must have equal length runners to have equal distribution to all cylinders, while this is a good thing on the exhaust side it is a must on the intake side. also exhaust manifolds do not need a plenum, intakes do.

Anybody have access to a flowbench for free/cheap?

--Ferdi

Yeah, not sure you need to introduce that kind of complexity as long as the plenum is comfortably larger than the volume of a single cylinder and flows well. That's why I'd be interested in smoothing out the transition between the plenum and runners.

if thats the case then why not make one with very short runners and a lot of empty space as a plenum?

again i'm not being ignorant or anything of that kind, i'm just trying to think of a way to improve the traditional way.

just dyno it and find out.

as dont forget the air flows in wavezzzzzzzzz

Not trying to shoot it down, symmetry is good if packaging allows.

Toyota does it on some of their corolla engines.

http://www.tercelreference.com/terce...manifold_1.jpg

Edit: Looking at it, this faces the proper direction to have the flange cut off and a b6/bp flange welded on.... Only problem would be clearing the shelf/shock tower.

I'd think there'd be more chance of starvation in a tubular IM design. Plus the runner length would cause major restriction for top-end flow. The ideal of the plenum is to have all the plenty of available airflow on tap within the plenum to feed the runners.

I do, but not all the time. And I'd have to learn how to get flow numbers on it, which wouldn't be hard.

Dyno it. Even CFD numbers are worth little, like brain said flow/pressure in each primary (short!) is in waves. Takes software way beyond what any of us have to even come close to modeling it accurately. Best way is to dyno it and determine for yourself it the gains were worth the cost.

Flow numbers would help give you an idea of if you're completely fucking up or not though. Like someone said in another thread regarding IM design, you could easily melt an engine by messing with this. Not to say the guy making this sucks...but it could help.

True.

I've seen some physiclly very similar intakes do some VERY different things on the same engine. This is with V8 stuff which may have more going. :dunno:

Yep, airflow pretty much has a mind of its own. Does some weird shit...

That manifolds main objective is to increase/optimize low end and midrange torque. The opposite of what big turbo miata guys are trying to do, which is improve airflow up top.

An Evo tuner who said "fuckin" ever 3-words told me that a huge chamber with long runners and 360* horns that portrude deep into the plenum will make the most torque...and to shorten them to add horsepower.

Free? And, is/has the setup to test Miata intake manifolds? I wouldn't mind sending you my manifold to get tested. My car is down right now anyways.

Mine is for the BP4W head, but with the throttle body on the opposite side (Protege).

--Ferdi

Shorter and wider, or just shorter? As far as I know, and I may be wrong, longer smaller runners increase velocity for low end power at the expense of overall flow and wider, shorter runners would increase flow at the top end. Making them just shorter seems like it wouldn't do anything.

Free, but we don't have a specific set up for a Miata intake manifold. I'm not an airflow tester expert, but couldn't you just bolt it up to a Miata head and test it that way?

so in other words you want pretty much 0 runners with a lot of empty space as a plenum?

i agree that the runners look super short. i did alot of research on dynamic flow effect, creating the optimum runner length to catch the intake pulses and actualy create power off them. i have raise velocity stacks in my manifold, that also helps alot with the air flow. from what i read you want the stacks to be about 1"-1.5" off the plenum floor. i cant say much about cyliner 1 being starved for air. the only way to fix this is to change the plenum shape, and make the throttle body entrance as far away from cyl one as possible.

this is my manifold
Attachment 202239
Attachment 202240
Attachment 202241

how about mounting the throttle body up top or the side and making both ends same shape?

As discussed in previous thread: that opens up a can of fitment worms

if you make the runners quite short, whats the problem?

up top won't work because of hood.
to the side the piping coming in from the front would have to make a big ass loop or sharp bend. Not to mention some other problems.

Just my .02 but I think if there was any merit to that idea some aftermarket manifolds would already have been made that way. I don't see any like that. Even on other cars.

I'm curious what effect having the air inlets raised off the surface off the plenum has. It would seem like you'd want the inlets of the runners to be flush with the surface to allow the full volume of the plenum to flow smoothly into the runner, but maybe the length of the runners supercedes that concern?

I'm very curious about the same thing.

I noticed that expensive supercars such as ferrari and audi and others have it this way too:
http://www.familycar.com/RoadTests/A...ineCutaway.jpg

http://articles.motortoday.com/featu...ake-plenum.jpg

the effective rpm of the manifold is sky high, it wouldnt be optimum for the engine. the way it works is when the intake valve opens the engine sucks in a big gulp of air, when the valve shuts, the incoming air slams into the back of it and bounces off. creating a pulse, now this pulse bounces back and forth in the intake track loosing momentum evey time it changes directions until the valve opens again. it is possible to tune the runner length to time the the pulse so that it bounces once or twice and hits the valve as it opens again creating a ram air effect know as "dynamic flow effect" this increases the engines VE, making more power for a given rpm range.

interesting

the point of a velocity stack is to speed up the air entering it. you want the air to flow around it to pick up speed. that why they are designed to not have a constant radius entry

i would think that if it was for a turbo application, flaws in design would be hid a little due to the forced air, but it would be crucial to a NA engine to have a proper plenum design to supply equal air to all cyl. that is why most NA cars tend not to use a plenum on ITB setus

Okay, so as long as the plenum is large enough to supply an adequate volume of air, the velocity stack increases air speed kind of like the top of an airplane wing (ie, longer surface to flow over)?

I know I'm reaching here but this is a philosophy major trying to understand this.

im not physics major but i think your on the right track. i took alot of ideas from the honda guys when i built my mani, honda-tech has an awsome fabrication form and you can learn alot from those guys. also i had the handbook from our superflow flowbench too, there is alot of good info on airflow in there, thats how i was able to calculate my runner lengths

He only said shorter. I'm a bureaucrat though, not an engineer.

wait wtf?

http://www.mototuneusa.com/SuperglueTrick.gif

tapering the runners makes the engine think that the runner are longer. some taper is good for runners. the problem is to buy them its very expensive. like $100 per runner. and so make them..... with the correct taper...... to the correct port shape.... to the correct length, is a major pain in the ass.

pretty good find, it confirmed my length was right atleast. to merge the runner to the port shape, i used cylinder head epoxy from ramracing. so my runners have some tapper to them.

I would put the stacks angled forwards and have the intake around 35-40 degrees from the front. I think this would provide the most air everywhere more efficient than having all the air rammed into the back of the plenum and then it starts to fill. imo

right that was my thinking behind using exhaust manifold style piping

It is a shame I'm not at all motivated to compare mine to a stock manifold.
http://i295.photobucket.com/albums/m...s/IMG_0518.jpg
http://i295.photobucket.com/albums/m...s/IMG_0497.jpg
http://i295.photobucket.com/albums/m...s/IMG_0520.jpg
Plate being cut on a large table cnc... designed to do decorate wood door/panel work :p
http://i295.photobucket.com/albums/m...s/IMG_0478.jpg

I can say one thing. If the air isn't going in evenly with mine... I haven't blown up in the last two seasons due to some random lean condition. Sadly the only dyno plot I have is with a damaged turbine wheel and a borrowed ignition map... and simple fuel tune.

And thats about all the tech I have. Runner length was gathered a few years ago from a few different sources... the details of which I've forgotten. But I think 5-6" was the spot we aimed for. Short for high rpm power.... longer for low/mid.... so i sat in the middle.

I'm not an expert on this stuff but I just read about it on the net for an hour. My research finds:

Yes, you will have no ram air bonus with those runners unless you rev like a sport bike. When tuning your runners you need to keep in mind that you are supposed to measure from the intake valve inlet to the (intake not engine end) runner radius. This gives you what looks like 6 inches which gives you a ram tuning effect somewhere around 14,000 RPM. The ram air effect is not negligible but as has been mentioned earlier in the thread, since you are boosted, runner tuning is not critical.

As previously stated, fixed runner length only tunes for a specific RPM (and it's harmonics). Mazda and other OEMs actually are pretty cool with their variable intake length manifolds. For super coolness though, check out this patent:

Continuously variable intake manifold - Patent 5687684

It's for a continuously variable length intake manifold.

To tune your runners you or your IM manufacturer could experiment with lengthening/shortening the runners on the dyno. I guess they could rig up a manifold with bolt-on runners.

Blah blah blah though. When boosted, plenum size is apparently much more important. I can't find any formulas on plenum sizing other than 1.5 * total runner volume. If your runner radius is 1" and length is 6" then according to that formula you need 108 cubic inches of plenum. That's 1.78 liters.

Throttle body also is important. Edelbrock says large plenums should have small throttle bodies and small plenums should have large throttle bodies. This kind of makes sense to me. I can't find much data about this on the net though. A real book will have to be read.

And also what those guys said ^^^ about transition between plenum and runner is important as well.

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If I were your situation, and I hope to be soon (if I can find a good intake mani to buy :)), I'd do this. Save your current map. Put new mani on, retune your maps ASAPPPP (hopefully just injector scaling will get you to your AFR targets), dyno, save map. Take new mani off and put factory mani on, load original map, dyno and see how they compare. Not many people do back to backs like this and this is the only way to know if your part swaps are really making a difference.

It's also been mentioned before in other threads that air velocity and pressure will affect the performance of the manifold. Splittime or you might see very different results at different psi levels. I think that at high boost the plenum size becomes much more important. Apparently these plenums are a big deal in megapower Supra land.


Onnnneee other thing to mention-- if you look at rally engine bays like this:

http://image.importtuner.com/f/24359...engine_bay.jpg

You'll see bigass manis to compensate for the tiny pee hole sized restrictor plate.

Hustler seems to have lots of pics of hot engine bays-- maybe him or someone else can post some pics of "pro" turboed engine bays so we can take a look at the manifolds.

That looks GREAT to me. #1 starvation issue seems to be fixed or helped with that tb positioning

its not as much as it sounds like.
also i got 113ci not 108

pi x R^2

3.14159 * 1 * 1

3.14159 * 6

18.84955 * 4

75.39822 * 1.5

113.09734 needed

113.09734 + area taken up by the runners = 3.14159 x r^2 x L

for the example lets make the runners flush.

36 = L x r ^ 2

L and R can be anything that adds up to 36

for example 10" long and 1.897366 radius.

1.897366 * 1.897366 * 3.14159 * 10 = 113...

from what i read the plenum volume should be 1.5 - 2 times the displacment of the engine, not the runners.

Marco?

I read the following also:

70% of the displacement
1.5 * total runner volume

This guessing sucks. I want to know how OEMs and pro race teams size their turbo plenums. It probably takes a lot more math than we are using.

I suppose that a lot of aftermarket people leave power on the table or are peak torquing where they don't want to be. Probably their airflow to all runners may not be best as well. But, I think boost may conquer all.