I like that analogy, easy to understand.

 

ah i have not explained myself very well i think , what i meant was , with my plenum , as we can see , the air hits the back wall, spins left and right ,and they come round in a circle and the 2 streams impact on each other in front of the plenum inlet point ..

so my baffle , stopping the streams hitting the back wall directly ,halted this cycle ,and so the inlet flow actually increased .

on rons plenum , i wondered , will the airflow ,seeing as its a much larger engine , still go across the plenum ,and again hit the wall and then have to turn left or right ,and come round in a circle like mine did ?

i thought that, maybe ,pulling the inlet to the plenum away from it ,towards the wing ,then , after the throttle body ,splaying the walls left and right to go right out to the ends of the plenum ,would drop the air velocity ,and stop the problem .

a nice gentle curved wall splaying out from the feed to the plenum could look good ,and be functional (under bonnet room allowing).


its very hard to describe this sort of thing without a sketch !


robert.

 

Robert, I think that you are missing the concept that we are discussing here.

Even distribution to all of the runners.

It is a known fact that when you have a sudden expansion of the air from a pipe that you will have colume of air that continues to travel in a straight line for the most part.
(Think fire hose spraying into a room. The water hit a big room, why did it not expand immediately to the size of the room?)

So the idea is if you have a high velocity column of air and you hit a volume that is not very deep that you will have two swirls created (that rotate in opposite directions).
See the video provided by a member.

So if you design the back wall correctly the air will loose a given amount of velocity traveling across the room and even more velocity when it hits the back wall and will therefore
flow in a large number of directions thereby supplying more even air to each runner inlet.

So there is a bit of an "Art" in getting the airflow to travel evenly to all of the runner openings vs blowing by some of them and packing up air at other locations.

Tom V.

 

Gents,

I'm doing some research on building my own intake much like everyone else on this thread. I'm trying to find out how to calculate the intake tuning effects (if any) caused by having fuel vapor in the manifold or at least early in the runners. With that will also be calculating optimal injector positioning based on said effects. I've read the thread a couple times but don't remember seeing any actual math dealing with this subject. If I've missed it, forgive me, however, kindly point me in the right direction.

Thanks!

 

I do not think that you missed it. I do not ever remember seeing it either.

A intake manifold fabrication shop run by a guy named Marcella did some dyno testing a year or so ago and had injectors in three different locations in the intake. This info was posted on a different internet forum. I do not believe that he reported any difference in the horsepower from any of the intake testing with the different locations.

Not an ad but maybe you could phone him at his shop and discuss.



If you look you can find his contact info.

Tom V.

 

Good progress here, I enjoy checking back.

And to the guy totally disregarding the blowers, doesn't get it. Yes it isnt like an operating engine, we get it

But it certainly shows what is going on with air speed and air mass, as Tom shared

What do you think is happening? There is a pressure delta with the blower just the same. Air mass is moving from high pressure to low pressure

Side note my machinist wanted to take my engine to a show, cleaned the intake up really nice for me haha.

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Also on the thickness question, I used 1/8 on the bent top, and 3/16 end walls and never saw a problem up to 25lbs of boost. But all going to depend on the shape too

 

With your "Bent Plate" design, the end caps will probably blow off a bit before the "Bent Material" section fails.

Flat surfaces have the most likely chance of bending and later cracking/failing (like the sides of some intercooler tanks).

Tom V.

 

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a little update on how the intake is going. I put as much injector angle on this intake without hitting the plenum. and I wish I could weld like a professional but I'm doing the best I can these round injector bungs are hard to weld. anything rounded is hard to weld because you constantly have to keep changing the angle of the TIG torch. I'm not sure why the pictures ended up sideways I was holding the camera straight up and down. sorry tom i did not see posting #34.

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come on zac i totally understand there is intake valves opening and closing so the air is going to go somewhere. im wondering if the air is going to swirl when it hits the side wall or entering the ports. by the way. im your friend on facebook. lol.

 

Swirl and Tumble are interesting to visualize but "very hard guys to make happy" all the time.

Swirl up to a given point seems to help with mixing of the fuel and air, but at some point you get too much of it and then
you get a air/fuel hole in the center of the chamber and fuel is leaving the mixture and collecting on the walls of the chamber.

So the golf ball divits, to me are a fix for a bit too much swirl at some point. If you put a swirl device into the port design at some point
that same swirl device starts to hurt you. Same applies to the "tumble toys". For dyno work we have tried a lot of good concepts and
some worked better vs others at some rpm points. It seems that for Emissions and Fuel Economy there is a benefit at times if you can
keep the parts working correctly for the life of the vehicle. For racing, especially with high boost levels, playing around with injector
boss angles and such might be worth something but a guy named Steve Grebeck (before he died a horrible death drag racing) told me
just weld the things on as best as you can and worry about other things. He is the guy who welded the bungs on my EFI manifold runners
in the pictures I posted for the forum. Steve was going really fast for his point in time in door car racing.

Tom V.

 

i remember steve grebeck and a picture of him and his mustang when he died on race pages.

 

Yes, Steve Grebeck worked for a company called Watson Engineering for a while then went off on his own.

He was building engines and chassis for Detroit 'Street outlaws' running on 12th street long before the 401 Street Outlaws were famous.

He worked out of a shop west of the Bloomfield Hills area of Metro Detroit. Worked hard, Raced hard, Died hard.

But he brought a lot of knowledge to the guys running the Fastest Street Cars group running out of the Detroit area. RIP Steve.

He was a really easy guy to talk to about racing stuff in person or on the phone.

Tom V.

 

i live about 45 min from there. watson racing is pretty big now with there mustangs. have you heard of skinny kid race cars?

 

Yes, and admire his work.

He kind of stepped in when Grebeck was killed as the premium Chassis Guy for the area.

Chuck Sr and Chuck jr and I go back to the days when Chuck Sr was running the little T-Bird with the
prototype Eaton 180 Supercharger on it and Chuck jr was running the early Vortech superchargers.

This was many years before their current Cobra Jet cars today.

Tom V.

 

hey tom v, I finally started on my tunnel ram project...... My project is to build a bottom feed inlet on a 540" big chief with twin 94's for a drag week style build. My initial plan was to run 4" tubing for a bottom fed inlet but I really needed more plenum volume so encased the lower section of the intake and I also added a "basement plenum" for more volume as well as more open area around the radius bell.... The radius bell connects the lower plenum to the upper plenum and the other end of the bell is just a pipe that terminates approx. 2" (or approx. 50%)into the upper plenum. The top of the intake will be a flat plate for the boosted air to bang off of and hopefully give me even distribution to all of the intake ports. My goal is to have an intake with great distribution with enough plenum volume to keep the motor happy and in a relatively short package (9.2" from the china rail). I also built an aluminum valley tray (not pictured) to keep the hot oil off of the lower intake. Before I weld the lower plenum on, I will be running an air flow distribution test with a huge lawn blower and an anemometer, lol.... not so scientific but it should give me an idea of how well it distributes the air. Excuse my tig welding.... i'll clean the welds up before it all goes together, lol. Hopefully I attached the pics correctly.... Tom, feel free to critique or make recommendations as I still have time to modify. Thanks! Tracy
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Hello, I looked at your intake again and like the fabrication work and the clean thought process for your efforts.

My opinion is that the vertical tube between the two plenums will act somewhat like a flow bench orifice between two large plenums or
an inter-cooler core between the turbochargers and the engine. A restriction to flow but maybe not a bad restriction.

It becomes the choke point for the air flow only if it is too small to pass the cfm requirement of the engine. I know that some rear facing
throttle body engines are using 125 mm throttle bore set-ups before the plenum. Think you said your deal was a 4" tube.

So I think the 4" tube with a couple of good radius openings will move a lot of air.

Keep up the good work!

Tom V.

 

hey tom, thanks for responding! The ID of the vertical tube is 4" and i'll be using a 105mm throttle body. I'm hoping that will be large enough but if not, I will go larger, lol. I really appreciate your opinion, thanks tom v! I'll update once I test the intake. BTW, the guy in the pic is my buddy who spun the radius for me.

Think you will be fine.

When you are under boost the radiused 4" tube can pass a lot of air mass. Guys who run the 125mm stuff: Throttle body and plumbing FROM the intercooler are really trying to slow down the air and reduce the velocity effect into the typical LS style plenum shape and runner distribution.

John Mahovitz had really good air distribution with his bottom feed intake. Good luck and keep the board informed as you progress.

 

One of the guys at work had too much taper on his 427 SB Chebby engine.

He thought he needed the taper for the 7500 rpm numbers he wanted to run.

Engine was not happy at all on the lower RPM ranges (5000 and below).

He eventually had custom inserts made up that "made the walls thicker" and changed the taper angle.

Engine was now much more responsive and made a bunch more power across the power band.

So my comments were based on real world dyno data after discussions with the person and a later fix of the taper angle.

Tom V.

 

hey tom v, little update for you. I have everything welded up except for the bottom plenum (so I can adjust the bell mouth and play with things while testing). Testing involves nothing more than a lawn blower taped to the throttle body flange (lol) and me checking flow with my anemometer/wind gauge. One thing I noticed early on is port variance is not very close. My question for you is how close, port to port, is good? 10%, 20%, 30% variance? In any given test I'll have about half of the ports within 10%..... but the other ports are all over the place. I'll keep playing with things to get the ports closer and update later. p.s... I tested without the lower plenum (just put a flat plate) and it killed distribution big time.... one port went into vacuum.