Getting closer

[olsonjus]

GET ER DONE:


Larger Pic here: http://forum.vwsport.com/pics/showph...ig&ppuser=2208

And the runner material:

[Billman]

will you also built other manifolds in the future? Also with Dual plenum??

[olsonjus]

I will sell complete manifolds minus the plenum if people would like to fabricate a dual plenum to fit there car.

Regards,
Justin

[Jon441cc]

When Audi introduced the 20V motor. The car was homologated with a unique special cast intake manifold with a dual plenum. One drawback of using a single intake plenum is that after the charge air passes through the throttle body, the pressurized air isn't going to hit the runners going to the head equally. Runners closer to the front near the throttle body could very easily get more air than the cylinder furthest away. The Air velocity could play a factor in this as well. Its a very different concept when compared against a normally aspirated car where each cylinder's vacuum draws air into the cylinder so a vacuous single plenum with velocity stacks makes alot of sense. Also on a normally aspirated car, its very common to see individual throttle bodies for each cylinder to get maximum airflow with the least pressure resistance. So how does one actually design an intake manifold that allows or at least attempts to provide equal airflow to each cylinder? Well why would one even want to? If modern electronics allows a different fuel injector pulse to each cylinder, we could just adjust the fuel flow to compensate for the difference in airflow. We could do that, but does that actually give us the most efficient use of the engine's potential? Surely if one cylinder is drawing in 50 cfm of air and another is drawing in 40 cfm, the ideal thing is to get each cylinder to take 50 cfm of air. More air means more fuel and that means more power. So in a perfect engine each cylinder gets an equal amount of air. Having one cylinder running rich or lean from unequal airflow could lead to premature engine failure. So simply put. Dual plenum intake manifolds are turbocharged version of individual throttle bodies.


The homologated intake casting for the 20V motor originated with the Sport Quattro street car and the S1 "Shorty" rally car in 1984. This intake manifold is recognized by the forward facing throttle body which works perfectly with a front mounted intercooler. This manifold also have built in mounting points for single or double injectors as well as mounting points for the fuel rail. Its also characterized by its large 2nd plenum which sits over the primary plenum underneath. The primary lower plenum with connects to the throttlebody is gradually tapered like a cone with a continuous single vent slot that allows gas to pass into the 2nd plenum. The 2nd plenum acts as a collector which then feeds the runners to the head. Pressure in the 2nd plenum is equallized since its not effected by gas velocity and inertia or the pressure variation from front to back of the 1st plenum. Since flow equals velocity times area. The reduction in flow which is released through the side slot is equal to the reduction in area of the plenum assuming velocity is constant. So a smooth conical taper with establish equal pressure and air distribution into the 2nd plenum.

Here is a picture of the early S1 Evo1 of 1984. Note that the car is running dual injectors mounted high on the intake manifold. Pressure readings are taken from the 2nd plenum which is on the top. The air ducting is simlar to a 10V car with a cut down firewall and airbox similar to the A2 Long wheel base. Notice the clever location of the power steering pump being driven off the exhaust cam.

I have this same intake manifold on my car. You can clearly see the flat spots just above my fuel rail which is for dual injectors. You can also see the mounting points for the high fuel rail when using two injectors. I am running single injectors which are closer to the head. Unlike some stock intake manifolds Audi carefully made sure the mounting bolts don't pass through the runners!

Here is the underside of the early S1 intake manifold. This manifold is commonly called a Lehmann cast intake manifold since its a modification of the Sport quattro sans Water manifold. To be clear, this is not a sport quattro intake manifold. It resembles it from the top, but a Sport Quattro has the water manifold integral to the intake casting. In this picture the conical tapered plenum is to the top and you can see its shape in the casting. The 2nd plenum is equal sized and very much like any other normal single plenum intake.

Did Audi use a tapered double plenum on their 10V car? Sure they did. The Trans Am! This photo shows a welded up custom intake manifold for a 10V head with a clear dual plenum with a prominent taper to the 1st plenum. A sinple cone with a continuous slot vent feeding the 2nd plenum.

Notice the consistency in where the pressure taps are taken. On the 2nd plenum towards the rear away from the throttlebody. This manifold which was fabbed by Lehmann Motoren in Liechtenstein is a great example of custom intake manifold fabrication.

Now the S1 Evo 2. This manifold is a great piece, but obviously mean the radiator had to be moved to the rear. This is a top to bottom design with the conical taper on the topside. Obviously there were some issues with the Cast manifold. Perhaps too restrictive, too small, or perhaps the throttle body location prevented the use of large intercoolers. Either way, this manifold came to be in 1985 and was used on the Pike's Peak cars as well as the Audi Group B S1 Evo 2.


A fabricator in Norway is making this custom intake manifold, but it shows very clearly the dual plenums and the taper and slot of the first plenum. I think the trumpet intakes are excessive in this application. The taper on my cast manifold is more pronounced and reduces to the size of a nickel by the end. This taper appears to still be about quarter size.

Why change things? A giant radiator of course. Here is the IMSA 90 20V intake. A flipped over dual plenum design. This is a VERY rare car. So its probably the rarest of all the manifolds we've seen here to date. This design is more compact with the tapered plenum tucked under the runners and the 2nd plenum. Its very much an enlarged version of the original Lehmann casting with obviously better flow properties.



Courtesy of James bufkin.

[90quattrocoupe]

Nice write up, with the pictures and the explanations. D**n this forum is a great knowledge base.

Greg W.

[zlobo]

Good

[Jon441cc]

Nice write up, with the pictures and the explanations. D**n this forum is a great knowledge base.

Greg W.

http://www.bufkinengineering.com/intake%20manifolds.htm

[Jon441cc]

any updates ?

[s2dude]

http://www.bufkinengineering.com/intake%20manifolds.htm

I knew Id read it somewhere before

[AndersS2]

@ Justin:

Awesome work!
This oozes of quality me thinks, and i want one, real bad!

Questions:
*dont know how this works, but will it be optional with a double set of injectors (example: 2 x 5, 520ccm)?

*Is relocating of the rad/aux-rad nessecary?

This looks mighty promesing, and please let me know when one complete manifold is finnished.

cheers,
Anders

[olsonjus]

I'm not sure about the auxilary radiator at this point. Does the wagner cast manifold clear the auxilary radiator? I have been thinking of making some staged injector manifolds. This will be later on this summer, but on my personal manifold I'm going to be running a second set of injectors on the underside of the runners. I'm doing a custom water manifold setup on the cylinder head to accomidate the secondary fuel rail and injectors as otherwise there just isn't clearance.

Regards,
Justin

[Jon441cc]

Any updates Justin ?

[olsonjus]

I have a shipment of flanges on there way to me finally. That will fill the orders of those that I've already taken. I'm finding a machinist that can keep up with the demand and schedule for this product as the current guy is great, but slower then crap.

[AndersS2]

any news?

[breitling]

Interesting..
Best looking intake i`ve seen.