Intake manifolds

So, what do you think so far? Gots to be the hardest way to make an intake manifold, right?

The next step is to machine some oring grooves on both sides of the runner legs. I was using Motoseal at those mating surfaces and only 2 bolts to hold it all together. As you can see in the last pictures, each runner leg now has 4 bolts and will use viton material rubber orings for a better fail safe seal.

Orings are also used to seal the throttle body, the poppet valve and the plenum cover to the plenum. You can see the oring groove for the plenum cover in post number 18.
 
DonWG said:
You know me better than that. I wouldn't leave you hanging with one little picture.

Custom 100mm throttle body. Configured to be GM friendly.
Click to expand...

You were just waiting for someone to asks for more weren't you Don. :eek: :smile:
 
I thought I'd explain how I came to some of the decisions I came to with this intake.

The throttle body and the upper plenum cover.
If you study F1 at all, you've noticed how they mounted that large air filter directly over the runner entrances and how the scoop diffuses flow velocity ahead of the filter. What an excellent design! They've found a way to effectively filter the air to save the rings and also use the filter as an excellent diffuser of flow pressure pockets ahead of the intake runners. A beautiful way to make sure one runner isn't getting a higher pressure than the rest. The shape of the air scoop leading to the filter is shaped to decrease flow velocity as it nears the filter. Again, this is used to lessen the chance of high pressure pockets before the filter. The whole system aims to provide equal flow at equal pressure to each runner. I tried to follow that same idea with my upper intake. The larger throttle body allows for a slower flow velocity entering the intake which lessens the chance of building high pressure pockets within the plenum. The upper plenum cover also is shaped to diffuse the flow velocity as it reaches the main plenum body. This alone does not guarantee equal flow and pressures to each runner. During testing it was found that the rear runners received more than a fair share of the flow. I somewhat fixed that by installing a simple spoiler in the plenum cover. The spoiler simply disrupts the flow aimed at the rear section of the plenum and creates a backup of flow or a more chaotic flow directing it more towards the middle of the plenum.
 
The port entry style is an eliptical flare as I stated earlier. Studies showed that this was the best shape to use in terms of total port flow. Even beating out a bellmouth shape!
I dropped the floor of the intake plenum away from the floor of the intake runners to insure that nothing interfered with flow into the port entries, from all directions. This design creates the problem of fluid accumulation in the floor of the plenum.
 
DonWG said:
I thought I'd explain how I came to some of the decisions I came to with this intake.

The throttle body and the upper plenum cover.
If you study F1 at all, you've noticed how they mounted that large air filter directly over the runner entrances and how the scoop diffuses flow velocity ahead of the filter. What an excellent design! They've found a way to effectively filter the air to save the rings and also use the filter as an excellent diffuser of flow pressure pockets ahead of the intake runners. A beautiful way to make sure one runner isn't getting a higher pressure than the rest. The shape of the air scoop leading to the filter is shaped to decrease flow velocity as it nears the filter. Again, this is used to lessen the chance of high pressure pockets before the filter. The whole system aims to provide equal flow at equal pressure to each runner. I tried to follow that same idea with my upper intake. The larger throttle body allows for a slower flow velocity entering the intake which lessens the chance of building high pressure pockets within the plenum. The upper plenum cover also is shaped to diffuse the flow velocity as it reaches the main plenum body. This alone does not guarantee equal flow and pressures to each runner. During testing it was found that the rear runners received more than a fair share of the flow. I somewhat fixed that by installing a simple spoiler in the plenum cover. The spoiler simply disrupts the flow aimed at the rear section of the plenum and creates a backup of flow or a more chaotic flow directing it more towards the middle of the plenum.
Click to expand...

I might add that the filter used in the F1 example is also very effective at dampening any plenum pressure pulsing brought about from the intake runners. Although, there really isn't a plenum to speak of in the F1 example.
 
DonWG said:
The port entry style is an eliptical flare as I stated earlier. Studies showed that this was the best shape to use in terms of total port flow. Even beating out a bellmouth shape!
I dropped the floor of the intake plenum away from the floor of the intake runners to insure that nothing interfered with flow into the port entries, from all directions. This design creates the problem of fluid accumulation in the floor of the plenum.
Click to expand...

Some may not know this, but the manifold that was used for the Indy Buick V6s used tuned intake runners that were enclosed in a large plenum box. The port entries were divorced from the plenum floor and hung out in the middle of the plenum box. This design, especially when used with methanol was very problematic with fluid accumulation. The identical problem that I had to address with my intake system. I was lucky to get some counseling from an engine builder (Murl Bruton) who knew someone else (Smokey) who was somehow involved in the Indy Buick V6 development, and clued me into the problem while I was putting together my intake. So I was able to incorporate a fix into my intake before I ran the engine and found out the hard way.

If you study post #1 you will see a small blue angled AN fitting at the bottom, rear of the plenum. In post #18 you will see a very small orifice in the bottom of the plenum below the large AN fitting. When in the car, a hose is connected to the small AN fitting and leads down to the left front fender well, where it is plugged. Future plans are to make a small collection tank with a drain petcock.
 
Nice work....and thanks for the intake lession....
 
DonWG said:
Some may not know this, but the manifold that was used for the Indy Buick V6s used tuned intake runners that were enclosed in a large plenum box. The port entries were divorced from the plenum floor and hung out in the middle of the plenum box. This design, especially when used with methanol was very problematic with fluid accumulation. The identical problem that I had to address with my intake system. I was lucky to get some counseling from an engine builder (Murl Bruton) who knew someone else (Smokey) who was somehow involved in the Indy Buick V6 development, and clued me into the problem while I was putting together my intake. So I was able to incorporate a fix into my intake before I ran the engine and found out the hard way.

If you study post #1 you will see a small blue angled AN fitting at the bottom, rear of the plenum. In post #18 you will see a very small orifice in the bottom of the plenum below the large AN fitting. When in the car, a hose is connected to the small AN fitting and leads down to the left front fender well, where it is plugged. Future plans are to make a small collection tank with a drain petcock.
Click to expand...
With alcohol fuel, you will have a lot of ice buildup in the plenum during a cold startup. A blizzard is occurring in there. As the engine warms the ice melts and will run into the back cylinders with a normal plenum design. With my design it would accumulate in the plenum along with a small amount of fuel that would back spray out of the intake runners, and gasoline that I use to prime the engine during a cold startup. After the engine has warmed, and before the first run of the day, I would drain the plenum using the hose and for the rest of the day I would be OK. Throughout the rest of the day, there would be enough heat in the manifold to help evaporate anything that accumulated. What's interesting is when you drain the plenum and put your finger in the flow of liquid. You can tell when you have methanol or water by the temperature of your finger. The fluid is luke warm when it's water, then switches to cool when it changes to methanol. Then the color would change and that's the fuels.
The drain is actually a very good tool for detecting whether or not the liquid intercooler is leaking. Yes, I've found that out personally.
 
DonWG said:
You know me better than that. I wouldn't leave you hanging with one little picture.

Custom 100mm throttle body. Configured to be GM friendly.
Click to expand...

Holy cow Don. That thing looks like a piece of a rocket launcher. Wow that thing is really big.
 
GNBRETT said:
Holy cow Don. That thing looks like a piece of a rocket launcher. Wow that thing is really big.
Click to expand...
When you do the math for optimum flow speed through a tube for 1200 hp, this is what you need if you're trying to keep intake restriction to a minimum. We'll ignore the size of my intercooler for now. :rolleyes:

If I can remember, I'll post a picture of the special throttle linkage attachment I developed to slow the throttle opening at light throttle positions for better control during burnouts, but increase throttle opening speed to normal at the higher throttle opening percentages. With a big throttle plate diameter, you end up having a very sensitive throttle. With normal throttle arm lengths, just a slight increase of throttle off idle can mean a lot of air intake for the engine, making careful control of the engine speed at light throttle openings impossible.
 
DonWG said:
Why do you sometimes see these large plenum volumes?

Buick Indy Engine
Click to expand...

You have 3 choices when it comes to picking a volume for the intake plenum.

1) Make it any size you want with absolutely no consideration for tuning consequences.

2) Design it in a manner to try and take advantage of intake side pressure pulse tuning.

3) Design it in a manner to try and dampen, as much as possible, any pressure pulsing occurring inside the intake plenum.

What are the advantages and disadvantages of each of these choices?

Right now I'm concentrating on the intake plenum only. Intake runner dimensions are another story. Although, if you choose to size the plenum to take advantage of pressure pulse tuning, the intake runner dimensions must be calculated along with the plenum volume and configuration (single or split plenum) to arrive at a whole package that works together to optimized intake side tuning. The Helmholtz intake system is probably the most extreme example of intake side pressure pulse or resonance tuning.
 
As you can obviously see for yourself, I decided on a large single plenum. I'll try to figure out the exact volume for everyone.

The idea behind going with the large plenum was to dampen, as much as possible, the pressure pulsations occurring inside the intake plenum. I wanted the intake runners to feel like they were open to the atmosphere. This is an attempt to simulate an 'Independant Runner' type of intake system. IR intake systems, when used with the proper length intake runner have always been well known for providing a broad, flat torque curve. IR intake systems may not provide the highest torque or hp figures, but they do provide a broader, flatter, smoother usable torque curve.

Intakes that are designed to take advantage of pressure pulsations, when tuned correctly can give higher tq/hp figures, but the overall powerband tends to be more peaky and where the power may be up in some spots, tends to be down in others as the pressure pulse tuning, as far as the intake side goes, only works to help a narrow portion of the powerband.
 
Thanks Mac.

And to think, most of this manifold was made on a simple small Chinese made, table top mounted, combination milling/drilling machine.
 
You must log in or register to reply here.

Similar threads

M
A/C O-Rings
Replies
0
Views
213
Metacom
M
P
Supercharged 3800 Series II (L67) Question
Replies
2
Views
201
87GraNasty
8
1
1986 1987 Exhaust Manifolds for Turbo Buick
Replies
1
Views
352
1987 Six Shooter
1
T
Looking for Headers and intake
Replies
3
Views
283
turbo6man
T
T
Intake Manifold?
Replies
6
Views
360
TURBO2
T
Top