I dont think i explained last post well, i was meaning reduce the diameter immediatly after the split, freeing up volume for larger plenums.

Its definatly a tricky one, the only way i can use a single plenum for all 6 runners would mean the runners are stupid short EG 7" (bellmouth to valve)!

Im enjoying thinking it through, the mulpix plenum is a nice shape, looking back i was thinking of mini versions of the intake you pictured in post #324 however to work i think id have to many turns and kill flow??

As odd as it looks would this work well, kind of Porsche / Mustang combo!

https://www.theturboforums.com/attachment.php?attachmentid=671831&d=1486508850
#ad


https://www.theturboforums.com/attachment.php?attachmentid=671830&d=1486508850
#ad


Using the initial 'T' split may not be necessary as the air hitting the back of the plenum and having to do a 180 should kill velocity, so it could have a nice flowing split instead?

Thanks

Dave

 

I had to look at the design a couple of times to relate to what you are doing.
I would move your impact wall "upward" in the drawing about 3 "arrowheads".
After the air bangs off the wall it still likes to move 'downward" in the drawing.
You want the first two cylinders to have as good of a shot as possible to get air
without the air having to flow backward which is why you need to have the impact
wall close to the bottom of the first two runners by going "sideways" vs backward.

Hope you understand that deal. Like a runner hitting a football front line and moving sideways.
Very difficult for him to run backwards.

Tom V.

 

OK, i suppose the physics of mass also applies to the air charge? (car analogy: when entering a turn the cars forward energy wants to continue straight ahead, even while in the turn).

My thinking for centering the T was so the halves were identical.

Onwards and upwards...

https://www.theturboforums.com/attachment.php?attachmentid=671835
#ad


The nice thing currently about this design is the T pipe is significantly shorter freeing up volume for the plenums.

1: I plan to keep the cross sectional areas of the 70mm pipe, transitional form and slit entry to the plenums all the same.
2: Each plenum is twice the volume of the T pipe, hopefully this will provide sufficient expansion for further velocity reduction.
3: Also to reduce the velocity im thinking the slot should enter immediatly not penetrate into the plenum?

I hope im moving in the right direction with this, i know a straight pipe will flow the most, hoping these directional changes wont impede flow, impacting performance negatively!

 

Looks really good now. I would say that you would be giving it your best shot for air distribution to the intake runners.

Tom V.

 

I'm not sure why it won't let me quote with your photos but this is exactly what I had envisioned doing when I found this thread (linked from corral).

I'm running a Dart 347ci 4.125" with little old AFR185s and an Ed Curtis cam/valvetrain. Right now there is an Edelbrock Super Victor EFI with an elbow used to front mount the throttle body. I am looking to take a Weiand 5988wnd, convert it to EFI with some bungs/rails, flipping a Holley 300-217 configurable top and cutting ports to match the Weiand intake and using a Holley 300-218 92mm top.

Looks like you did already exactly what I had planned.

How did you gasket/o-ring the two upper halves?

I assume that both sections of your upper halves are straight bore mounting holes with no threads, did you drop a heli-coil in the lower?

Do you have any other pictures of the inside of the lower half of your upper plenum?

What I envisioned
#ad


#ad


Underhood now
Underhood now
#ad

 

The Nash Intake us some what similar to what you are doing but the lower intake on mine is set up for a Dual cross-wise Dominator set of carbs.
So it is a Dominator intake like you would have on a Individual runner intake or a Hilborn type set-up.

I had a custom base made for my intake that used a welded in plated that matched the dual Dominator port pattern and mounting pattern.

When we were making the lower "bathtub" I had the upper rail of the bathtub machined for a .060" groove that would be installed and seal the top and bathtub parts when bolted together. The fasteners holes were already threaded studs to hole everything in alignment.

I had thought about modding a Weiand Tunner Ram intake similar to what you show but for a 440 Chrysler engine. The difference in manifold angles and spacing would be corrected with custom plates.

Looks like you have a great start.

My deal will eventually go on a Twin Turbo Pontiac Engine.

Tom V.

 

Thanks. I am planning on using the flange and sidewalls of the "bathtub" section and lowering down as far as I can get it to the fuel rails. It all has to fit under the factory hood for me. Having the lower section channeled for the O-ring should be easy enough on a mill. I looked at the instructions for Holley's replacement o-ring. It is a cut to fit then glue together. Should be a non-issue there.

Now to get parts on order and start cutting.

 

Dave, they had a Forum Upgrade and the links are not vaild any longer until they correct something.
My thought is any reduction in the flow passage increases the velocity again vs fixing the design so that you kill the flow energy and all of the runners see basically the same flow at their entrances.

Tom V.

 

Bump.


I guess I wasn't an idiot, lol

 

Hi Tom, apologies is missed your post and repost!

Ive lost train of thought with you, what part of the intake are you referring to when you say;
"My thought is any reduction in the flow passage increases the velocity again vs fixing the design so that you kill the flow energy and all of the runners see basically the same flow at their entrances."

Hoping to get started on this soon

Out of curiosity do you guys see any negatives in this design other than complexity of fab versus say Zbrown's bottom slit entry #226 or the more conventional Marcella esq hump intake?

I cant help but think the slit entering the plenums at the top is bad versus it entering centrally as the the air could 'ride' around the plenum wall to the bottom of the runner bellmouth.

Best

Dave

 

The problem with that "air hitting the back of the plenum" deal is that is what happens naturally so you have 4 rear cylinders (on a V8) that run "Air Rich" and "Fuel Lean", and 4 front runners that run "Air Leaner" and "Fuel Richer". Not a good deal for tuning or making power. Yes, you can trim each injector to get the correct air/fuel ratio but in reality the power does not "AVERAGE out" on the engine.

That is why you fix the air before the air sees the runners, with either a Top configuration like this:
#ad
or a configuration like this: #ad


Tom V.

 

Sat all night reading this thread! Has given me just the info I needed to get cracking

Mega commitment Tom thanks for all the informative posts...

 

Thanks M3RNG, there have been a lot of great posts on this thread.

Since you just read the whole thread, in a couple of posts I mentioned that we had built a Pontiac vehicle with Twin Turbos in the 1996 timeframe with a custom intake. It worked very well for a very small 406 cid engine.

That car was sold a while back to a guy in Oklahoma and it is now his car on a program called Street Outlaws.
He crashed the old car and then bought a different car that did now work out for him. On a recent show he ran a 1.02 60 ft time
which is where we were in 1996 with the same chassis. Big Chief is the guys name on the show.
The Butlers out of Tennessee Built his 482 cid Twin Turbo Engine for the show in the beginning.
So basically the car is a older but well designed steel race car. The original owners kept the custom Twin Turbo Intake we did the first time with the car. So I have been helping people with their intakes for about 20 years now and all of them went fast.

So GET CRACKING, post up your designs for all to learn from and we can keep the thread going and help others.

Tom Vaught

 

Sorry fat finger. TV

 

Hi Tom thanks for the welcome... So still in the design faze but will give you where I am at...

I did see and read post #127 about the pontiac with the Straight plenums and also see the pics wantabe posted up on #129 when he was using itb's

It was a design I was quite keen to use, Orginaly I was only looking for a volume calculation when I found this thread

160% minimum for FI is what you stated Tom, so with my 4.0 that would give 6.2L of plenum volume from throttle body to start of the runners?

Fortunately I now know distribution is pretty important and perhaps straight cylinder are not the best and possibly a Wilson style is a better design?

I was originally wanting to run twin TB's and would still like to rather than one large single, I have used large single TB's in the past and found you loose some midrange and low throttle finesse! The trade off would be some losses due to an extra blade and shaft blocking airflow but I can live with that as outright power isn't priority

moving the TB forward and angling it down slightly will stop throttle blade influence and as long as the overall plenum volume is taken into consideration this shouldnt have any affect on the throttle responsiveness should it Tom?

I am a little undecided on design but leaning more towards single camel back plenum with elongated twin throttle body feeds

What's your thoughts Tom?

Appreciate your input.

Ben.

 

1) In basic terms, you want the individual runner stacks to think they are in a large dyno room.
No starving of one runner by another runner, so large plenum volume is good.

2) I did some serious testing on Blade Angle at McLaren Engines on a Special flow rig they did for me.
Blade angle if too close to the plenum expansion can cause the air to be directed to the rear of the intake.
Marcella Manifolds does a "Hunp-Back" design on some of his intakes to gain even more volume close to the front runners and remove some of the blade angle effects. The first image in this link: http://marcellamanifoldsinc.com/ shows a way to do two
TBs on a Tunnel ram Intake. Deal is John Mahovitz has run in the 5s with a 281 cid Ford
with ONE Throttle Body and the bottom feed design.

3) Agree that the very large 100-110-125mm throttle bodies are not for street set-ups, more like "on-off" switches.
The 2885 HP engine used one large T/B but it was a drag only deal with dropping cylinders helping the turbos to spool.

Hope I answered the questions above. Sounds like you are on the same path as several Intake Experts.

Tom V.

 

Thanks for the reply Tom,

In regards to plenum volume is 6.2L a correct calculation for my 4.0L engine? I have plenty of clearance to go as big as I like but the main gaol is to get the flow as even as possible and keep spool time to a minimum...

Speaking of mclaren, the twin throttle bodies the MP4-12c use are 60mm I was thinking about using the exact same tb's for this plenum

Again the hump back design is the exact one I was looking at but I didn't see the twin design one you linked! "Very nice"

We are aiming for a maximum power of 800hp and the car is only used as a circuit car mainly at the Nurburgring in Germany and also some uk tracks... Realistically if we can have a solid powerband drivability is more crucial than power but we are just guessing at what power we could actually make...

Would there be any more advantages dropping the throttle bodies a few more inches away from the front of the plenum than say the marcel one? Still making sure to keep within the volume amount stated above.

As for being on the path of intake experts my knowledge has only come from reading this thread and what you have wrote so thank you sir.

All the best
Ben

 

I have seen several intakes with 200% of displacement but these were Drag Cars, not a circuit car at the Nurburgring. You are probably ok with 155% but if you added volume behind the throttle bodies then you could get closer to say 175%of engine displacement. The farther away the T/B is from the beginning of the plenum the less effect that the blade angle has.
Tom V.

 

Great Tom thanks for the confirmation

On the first page you stated "I am not a big fan of "Large Taper" Intake Manifold Runners. I have recommended "stuffing blocks" in a couple of intakes to reduce the taper due to the large taper angles and the engines ran better with the "stuffer blocks" installed vs with the as made large taper intake runners"

Do you have a generic taper ratio off the top of your head you would like to see?

Also a runner length from the valve seat to the plenum its self?

From research and reading I was going to start with a 12 inch runner including the port length from the valve seat to the plenum

So if the the port
Length is 4 inches I would have a 8 inch runner from the head face to the plenum making a total plenum to cylinder length of 12 inches

The engine revs to 8000rpm

This is the last part of the puzzle before I start work I have ordered some materials and have had the base plates to head laser cut to commence building

#ad