The 3rd type of V8 intake manifold

[bmwhiteman]

The other day I pulled an intake manifold off the M60 in a 1994 740il and didn't notice till today that inside of it there are little trumpets on each of the runners. Neither my old M62tu manifold or my M62 non vanos intake that is on my car have these trumpets on their runners. I just didn't know there were 3 variations and was wondering what the performance differences may be?

M60 manifold


Non Vanos M62 manifold


M62tu manifold


And here is a nice runner size pic

M60 manifold on the left, M62tu on the right

In this pic the M62tu manifold has what seems to be some kind of built in throttle body spacer that is about 10mm wide

[mattmartindrift]

photos?

the only way to definitively tell is to toss them on a flow bench, or swap between all 3 and dyno in one place.

I would assume (based on the 4.4L M62 non-vanos) that computer simulations and testing had been done by BMW or other engineering firm and showed the non-trumpted as superior.

[topaz540i]

the trumpets seem to make left and right sides closer together meaning the air has to turn harder to get around the corner into each port.

i also see that the front left one is missing in your pic. are they removeable?

any idea what that valve is one the side of the m60 manifold near the throttle body?

the trumpets could possibly smooth air flow quieting the intake.

[bmwhiteman]

the trumpets seem to make left and right sides closer together meaning the air has to turn harder to get around the corner into each port.

i also see that the front left one is missing in your pic. are they removeable?

any idea what that valve is one the side of the m60 manifold near the throttle body?

the trumpets could possibly smooth air flow quieting the intake.

Na it's not missing. The intake runners are offset. That's a blank spot.
It's not a valve, it's either a MAP or IAT sensor. Theres a plug where that would be on M62tu manifolds

[AnotherGeezer]

Or they could exist to make "Flight of the Bumblebee" sound better at 6500 rpm....

[topaz540i]

you would think it makes more sense for them to face the throttle body

[Black540Msport]

you would think it makes more sense for them to face the throttle body

The point of the intake runners is not to point at the throttle body to get the most amount of air into them, or we'd see all intake manifolds look more like the old Ford 5.0L intake where the throttle body was on the side and all 8 runners pointed directly at it relying only on vacuum (cylinders pulling down) to fill the cylinders.

Instead, the point of the intake runners being opposite eachother is to have the reflected intake charge (i.e. the air that is racing down the intake runner, gets reflected via the intake valve slammig shut) from lets say cylinder #2, hitting the reflected intake charge from cylinder #1 on its way back up the runner, thus, creating a tuned port setup where the intake charge that was just hit by cylinder #2's reflection is hammered down runner #1 even faster. This stuff all happens at supersonic speeds inside the intake and is really controlled chaos, but the theory works.

Wish I could find the video of how this works still...

Edit: those trumpet shaped things are called velocity stacks intended to smooth out the incoming airflow. I'm unsure of why they'd omit those things as the concept behind them is sound but I'm just a repair technician, not an engineer for BMW so what do I know...

[xatlas0]

Those "trumpets" are called velocity stacks. They are used to smooth the inflow transition into the individual runners, thereby increasing the total flow. They are also used on the S38/M88 manifold. They are sized (along with the runners) to provide peak performance around a particular RPM range. Given that they are short, they are designed to boost high-RPM performance, but it can't be all that high RPM given they are attached to fairly long intake runners. A gross oversimplification boils down to long runners=low RPM torque, short runners=high RPM torque. Given the M6X's relatively small displacement, long runners were used to improve low-end performance at the cost of high-end to improve everyday performance.

The effect Black540Msport is trying to explain is called "Helmholtz resonance", by the by.

Overall, intake manifold design is really tricky due to the fluid mechanics involved and the wide operational range required by a gasoline engine in a car. Fascinating subject if you feel like diving into some multivariable calculus.

[Black540Msport]

xatlas0, yes thats it! I was trying to remember that but couldn't for the life of me since its been probably 8 years since I looked into it.

And I agree, the mechanics of fluid dynamics is really neat to look into!

[topaz540i]

so anyway... do we want trumpets or not. i just bought an m60 manifold that hasnt arrived yet.

[Black540Msport]

[topaz540i] I work with a guy that plays the trumpet, he's pretty good too! [/topaz540i]

Anyway, They've been a part of intake designs for a LONG time, I can't imagine they'll hurt anything.

[topaz540i]

i mean if we had a choice. the m60 manifold is a performance swap and it seems this guy discovered there are two versions to pick from.

[sfgearhead]

I'd like to see dyno results for the different manifolds. Personally unless I was racing and/or at WOT and high RPM regularly I'd prefer the extra torque of the standard manifold. But that's just me.

Overall, intake manifold design is really tricky due to the fluid mechanics involved and the wide operational range required by a gasoline engine in a car. Fascinating subject if you feel like diving into some multivariable calculus.

Fascinating yes. Easy to understand? No. I had to take fluid dynamics twice, as it just didn't click fast enough the first time. At least I got an A the second time.

[sfgearhead]

Overall, intake manifold design is really tricky due to the fluid mechanics involved and the wide operational range required by a gasoline engine in a car. Fascinating subject if you feel like diving into some multivariable calculus.

Fascinating yes. Easy to understand? No. I had to take fluid dynamics twice, as it just didn't click fast enough the first time. At least I got an A the second time.

[CBi]

can you post the part number on the manifold?

[E39 Prototype]

Go big or go home.

[JimLev]

Topaz, I'd have to guess that the trumpets were removed because they were a restruction on getting equal air flow to the rear ports.
I'd use the one without trumpets.
The sensor you asked about is the air temp sensor, the 740 had them there, the early E39 moved them to the air filter box and the M62tu had them built into the MAF's. You probably knew that.

[AK_5eries]

I'd like to see dyno results for the different manifolds. Personally unless I was racing and/or at WOT and high RPM regularly I'd prefer the extra torque of the standard manifold. But that's just me.



Fascinating yes. Easy to understand? No. I had to take fluid dynamics twice, as it just didn't click fast enough the first time. At least I got an A the second time.

A more restrictive manifold produces higher torque? How so? Does it have to do something with the speed of the air coming into the engine?

[topaz540i]

If the air travels thru a bigger diameter it much move slower to achieve the same volume.
If the air moves thru a smaller diameter it must move faster to achieve the same volume.

Somehow the difference in speed of this equal volume affects precombustion fuel atomization. I dont have any more than that because for some reason they stopped beaming messages into my brain halfway thru the thought.

Topaz,
The sensor you asked about is the air temp sensor, the 740 had them there, the early E39 moved them to the air filter box and the M62tu had them built into the MAF's. You probably knew that.

Yes i did, i already know everything worth knowing plus alot that isnt.
I was testing you and you did well my son.

[AK_5eries]

Sounds like the more restrictive one is better. Why is everyone (including Dinan) trying to get the bigger runners?

[topaz540i]

More top end.
You might lose a little torque with only this mod but when pared with a c.a.i., exhaust, and software it should really rip.

[sfgearhead]

A more restrictive manifold produces higher torque? How so? Does it have to do something with the speed of the air coming into the engine?

Smaller diameter will help the air move faster and help fill the cylinders at low speeds.

At least that's what I remember, it's been 20 years since I took fluids. Never mind all the lying and drinking that has clouded my judgement since moving into marketing.

[bmwhiteman]

More top end.
You might lose a little torque with only this mod but when pared with a c.a.i., exhaust, and software it should really rip.

Yup I have all 3 of those and it really rips. Really weird that no one noticed this before. I have the non vanos manifold without the velocity stacks (trumpets)

[xatlas0]

Topaz, I'd have to guess that the trumpets were removed because they were a restruction on getting equal air flow to the rear ports.
I'd use the one without trumpets.
The sensor you asked about is the air temp sensor, the 740 had them there, the early E39 moved them to the air filter box and the M62tu had them built into the MAF's. You probably knew that.

Nah, they were removed due to cost. The M62 is the beancounter-cut version of the M60, hence the timing hardware changes, the intake manifold changes, the exhaust manifold changes, FI system changes, auto trans changes, etc. All those items were reduced in quality on the M62 compared to the M60 parts.

Let me put it this way: every M-engine uses velocity stacks, from the M88 to the S85. They are an important part of advanced intake manifold design, as they help prevent flow necking down the runner, which helps keep the flow profile steady, reducing flow friction losses. They are very much a good thing.

The intake manifold set is not new information, at least among the E34 guys. It has been known for quite some time that the performance goes in this sequence: M60>M62>M62TU.

[E39 Prototype]

You want the stacks, and this info isnt "new"... just search the e38 section.