I've been looking at fabricating a manifold for my 5.4L Navi headed turbo engine. This thread is full of knowledge. Thanks for sharing guys.

 

Progress on the intake runner design. The design will incorporate injector mounting bosses on both the outer and inner surfaces (not shown in these layouts). Each mounting boss will be able to mount 2 E injectors.

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Looking Good. We put injector bosses on the upper and lower side of the intake runner (based on a SB Chevy TR Runner), in 1995 on a 406 cid Pontiac Engine that went into the high 6s (6.96) at 206 mph in a Pro Mod chassis. We were running alcohol and needed a lot of volume flow. The concept works well.

We used a simulation program called MANDY (at the time) that said that we should have a lot of plenum volume. It worked too. Car would 60 ft in the 1.02 -1.06 range.

Tom Vaught

still working on trying to get a photo of the V-6 intake with the scallop divider (between the runners and the t/b).

 

Do you remember the plenum volume to engine cid ratio? I was thinking of going with at least a 3:1 ratio, plenum volume to cid. I'm figuring the larger the ratio, the best chance to get the intake to act like a true IR system, which I believe translates into a broader torque curve.

 

We were at 2.3 to 1 Plenum Volume to CID.

Could not package any more due to 406 cid size of the engine.

Agree on the True IR effect

Tom Vaught

 

I love this discussion and have learned a lot so far. Here are a few things I'm curious about.

With regards to overall volume, is there an ideal number (or range) for the percentage of open plenum volume vs volume in the runner? Or with a boosted engine does it not matter as much? On that Indy engine, it looks like those runners are pretty long. Is that more to help straighten out the airflow as it enters the cylinder, to fit that nice big plenum on the under side, or something completely different?

 

From my research, I've found that there are optimum plenum volumes to use. I feel there is an advantage optimizing the plenum volume even with a blown application. In a blown application, there is still pressure pulsing occurring. Just at larger pressure thresholds. The optimum volumes to use are also different depending on the number of cylinders.
Do a search on the helmholtz resonator.
The thing about fine tuning for peak performance with the intake manifold is that you will optimize at one particular short rpm range, but may cause a drop in another rpm range. For instance, if the manifolding is optimized for top end performance, bottom and mid-range may suffer for it.
Sizing the plenum in an attempt to cancel out pulse tuning using the plenum tends to smooth out the total torque curve, resulting in a good compromise through most of the engines complete rpm range. It tends to have the engine operate as if it were running an IR (independent runner) type of intake manifolding. IR manifolding is known for giving an engine a broad, flatter torque curve.
To accomplish the later effect requires using plenum volumes in the range of 200-300 percent of engine cid. Again, depending on how many cylinders the plenum is feeding. The lesser number of cylinders requiring the larger plenum volume.

 

so has anyone here done any research or experimentation with the split plenum intake similar to the older audi race intakes. which basically serperates the main plenum and the intake runners from the throttle body and a smaller plenum, by using a long slot to distribute the air evenly to the cylinders. similar to thesehttp://uploads.turbosport.co.uk/getrempic3.php?url=http://www.dahlbackracing.se/images/Parts/insug/797.jpg
would make a lot of sense to me, to set it up like this on the plenum floor similar to some of the previous posts

 

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

http://forums.hybridz.org/index.php/topic/61549-turbo-intake-plenum/

 

^^^^ thanks for posting that. was trying to find it earlier but couldn't. i really like the idea just wish i could find some math behind it or top secret pictures of the insides of those intakes.

 

Facinating information.

 

Without giving away any research secrets, I will tell you that the production Audi "split plenum" manifold is "smoke and mirrors". It does not distribute the air to the individual cylinders any better vs a normal intake manifold. The "slot" is too big and the air still packs up at the back of the plenum and back runners get more air with the front runners getting less air.

Possibly with more tuning on the slot you might achieve more even distribution to the runners but you would also choke up the total airflow to the runners.

That being said every engine is different and the amount of airflow going through the specific engine would change and the manifold would have to change too.

There are other ways to get the airflow even to the individual cylinders but package may be an issue. The Audi intake does package very well and has a LARGE throttle body inlet flange, it just doesn't actually work.

Tom Vaught

 

So how about this:
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The only manifold that I ever saw that did a decent job of getting the air to all cylinders pretty evenly was this design (excluding Tunnel-Rams and IR systems)

http://www.ebay.com/itm/GT40-93-Cob...Parts_Accessories&hash=item4165adf6bb&vxp=mtr

The air goes into the inlet of the manifold, has a nice straight section to uniformly fill the feed passage (after the throttle body blade flow disruptions) and then the air "bangs off the wall" of the intake plenum. At that point it evenly goes to both runner groups at a much lower velocity and then enters the specific port as required.

I have seen "dividers" that forced air to go EXACTLY where the designer did not want it to go. That being said, a good CFD program could answer a bunch of your questions. I might have access to a bit of CFD "free time" where I could get you into the general ballpark. I am always personally interested in how to make airflow go where I want it to go.

Tom Vaught

 

smackery thats what i was thinking i wish i had a form of solid works but its easier for me to build it in cardboard templates or hand draw a blue print.
boost engineer, thanks for the response i wish i had access to a cfd program. so it seemed logical to me that, by making the slot tapered between the plenums, you could still make the slot large enough to not be a restriction. by damning it up towards the back it would even the flow to the tb side where there's less restriction then the back of the slot. granted i think you will definatley need a large plenum to help insure the runners are drawing from less disturbed air.
i know i'm a little diffrent than most because the intake i'm trying to build right now is for a 4 banger but i believe the concepts are still very relevant. i will also be building a sbc intake soon aswell

 

If you look at the different pictures in the links there were a bunch of similar but different attempts to get something out of the Audi Design. That being said, just because the Audi production 5 cylinder part did not work as expected does not mean that there is not merit in the basic design. Go for it.

Tom Vaught

 

I don't remember the who/what/when/why/how on this, but it's...."interesting." It looks like the front cylinders would get shortchanged, but if there's one thing I learned fluid behavior, it's that it often is not intuitive. :scratch:
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Here's another variation on the dual plenum design on something that's not an Audi.
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Last photo of the "non Audi" intake is interesting.

Thought came to mind that if you did a CNC "clam shell" of a Audi Design intake
you could possibly get the slot dimensions right for best power and possibly a design with multiple slots of different slot widths in different parts of the intake length might have merit.

Tom Vaught

 

i was actually thinking of building it as two seperate bolt together plenums, that i could sandwhich a plate between with the slot. this way it could be easily changed, to try and find the best shape.

 

buggered if i can find it but theres some intake manifold stuff on speedtalk with some CFD images, assuming im understanding the thoughts in this thread, the stuff im thinking i saw had basically 2 plenums with the throttle body in the bottom plenum, and a series of holes for air to pass through from primary to secondary plenum (which fed the runners)

The holes showed a much better result for distribution than a long slot.

If i can find the thread and find time to re-read it to make sure i didnt make the whole thing up ill link it here for your amusement.