3.0L - how I did 4" stacks on Webers
 

I've been wanting to run 4 inch stacks on my webered 3.0. I finally figured a way to make them ( sort-of ) fit. I got some 3/16 redi-rod, washers and lock-nuts. I cut 8 pieces of rod to 6 inches which gives me a little over 1 inch on top of the stacks. used the rods to support the K&N rainhats by fixing them to the baseplate. I've got some oilable filter foam to fit between the top of the stacks and the rainhat to use on the street. the RH hat stuck out too far so I sacrificed a plastic engine lid grill. if this sounds confusing maybe the pics will make more sense. Don.

http://forums.pelicanparts.com/uploa...1283886045.jpg


http://forums.pelicanparts.com/uploa...1283886062.jpg


http://forums.pelicanparts.com/uploa...1283886083.jpg


http://forums.pelicanparts.com/uploa...1283886110.jpg

Maybe use an expanded metal screen....a la 911R or such....and not have the sacrificial plastic screen be so obviuous?. The expanded metal may either be able to sit higher (itself being shallower in profile depth)... or allow a shallow bulge that won't be so noticable?

Also....ditch the cool-collar .... :)

Don,

I have the same stacks on my TWM EFI ITBs. I just use oiled UNI filters rather than rain-hats. The #4 cylinder will squish down against the decklid. I have not had any issues with water getting in (or other FOD).

I do not think that filter material sandwhiched between the watersheild and the top of the stack will stay in place. Most likely this will be ingested through the motor at WOT. There is A LOT of air moving through there.

I'm looking for some screen already. the cool collar is there for chuckles more than anything.

Jamie, can you post a pic of your set-up?

Jamie. a little math tells me that at 6000 rpm the engine flows about 300 liters of air per second! does that sound right? it doesn't seem possible for the engine grill to flow that much.

Let's see here

2994cc at 6,000 revolutions per minute, but it takes 2 revolutions to fire all six cylinders, and you have air flowing through the intake only 1 of the four cycles.

In 6000 revolutions, a single cylinder will have 1,500 intake events.

A single cylinder in a 95 x 70.4mm engine displaces 499cc.

The firing order is 162435, which is also the intake event order, so you have alternating intake pulses that start at the front of the left bank and work backward, and the back of the right bank and work forward (in direction of travel). So you never have two cylinders on the intake stroke on the same bank at the same time.

So, you have 499cc of air being sucked in 750 times per minute per bank, that's 374 liters of air.

I realized afterward my math wasn't taking the 4 stroke into account. but, is the above math by 304065 right?

each cylinder still draws it's displacement of air each second revolution of the engine. so my figure was twice as large as it should be.

so a 3.0 liter is drawing 9000 liters/minute at 6000rpm. which makes it 150 liters per second.

or, each cylinder draws .5 liters each second revolution. at 6000 rpm each cylinder draws 3000 times .5 liters. that makes 1500 liters per minute per cylinder. times 6 cylinders divided by 60 seconds in a minute makes it 150 liters per second.

still seems like a lot of air to get thru the engine grill. I having trouble imagining 7-1/2 five-gallon pails of anything going thru the grill every second. yet, it's happening.

has anyone done a dyno test with the lid open and closed and compared?

What's the purpose, for more power @ WOT? What are your engine specs? Seems like a good way to ruin a nice engine grill.

Sherwood

engine details here-

http://forums.pelicanparts.com/porsche-911-technical-forum/502996-3-0-dyno-day-pleasant-surprise.html

it's my understanding, very limited admittedly, that a longer intake run helps lower end torque. no?

Yes, your new longer intake tract should help low end torque. Take a test drive with the short stacks and note how the engine seems to have a strong "cam effect" increase in torque around 5000 RPM. Now install the longer stacks and the "cam effect" with drop 500 or more RPM. My stock 3.0 with carbs had the torque step at 5500 RPM with short intake manifolds, 5000 RPM with tall intake manifolds and 4500 RPM with 1.5 inch spacers and tall manifolds. Just had to cut the intake grill like you did.

-Andy

OEM's have longish intake manifolds for just that purpose, but without having to extend pieces beyond the body lines. How about curving the intake stacks toward the middle into a single ITG-type filter (sideways orientation)? That would look neat as well as accomplish your objective.

OTOH, short intake paths provide more power at the high end. Thus, various OEM's have their versions of a manifold with variable length intake paths.

Sherwood

A cylinder fires every two revolutions. That would be 3000 intake events. Correct me if I am wrong here.

An ignition event occurs at the end of every other revolution. An intake stroke is half the revolution. Therefore, at 6000 rpm, half your strokes are on the power and exhaust, the other half are on intake and compression. Half of intake and compression is intake. So you have 3000 ignition events but only 1500 intake strokes.

These two statements contradict each other and seem to be causing confusion.

Perhaps there is confusion here with degrees of rotation per individual cycle.

From above, 1500/6000 or 25% equates only to the quatity of time (or degrees - 180) during two rotations (720 degrees) which is spent on any one specific cycle. Since each of the four cycles is completed within 180 degrees of crank rotation it takes two crank rotations to complete all four cycles, and therefore one intake/cylinder fill for every second rotation. Though only 25% of the time/degrees of a complete cycle is consumed by the intake stroke.

How I was told it works:

A pressure wave is created when the intake valve closes. This wave travels at the speed of sound from the intake valve, to open atmosphere, and then bounces back to the intake valve. When this wave hits just before the intake valve closes, it pushes extra air into the combustion chamber, improving volumetric efficiency.

The longer the intake, the longer it takes the pressure wave to hit the valve, helping low RPMs.

The shorter the intake, the shorter time it takes. High RPMs.

I think you have confused yourself. An intake stroke may only happen for half of the time of every other revolution, but it still happens once per every other revolution, regarless of how long. You cannot reduce the ammount of instances is occurs just because it doesnt take the full revolution to do it.

There is an intake for every 2 revolutions so there are 3000 intake strokes for every 6000 revolutions. Your logic would make sense if you said there are 1500 intake strokes for every 6000 strokes (not revolutions). But 6000 strokes is only 3000 revolutions.

Would larger bellmouths help?

Engine & fuel engineering - Fuel stand-off - intake reversion - what are the causes?
http://members.cox.net/dwynne7/Spitback.jpg