Turbo Intake Plenum

[hughdogz]

i dont know why staged compressor blades would . It seems that staged compressor blades would INCREASE efficiency and not reduce the efficiency?!

 

I totally agree Prox, that was a typo on my part. I knew somone would prove me wrong I found a Wiki that explains pretty much the same thing you mentioned.

 

Sorry Monzter, back on topic...I wonder if it would be worth looking at the swirl pattern having just one (or two) open at a time?

[MONZTER]

I was actually going to look into the opening of the valves in relationship to the cam I will be using. I don’t think only 1 valve is open 100% at one time. There may be 1 valve open at 100% and 1 or 2 more partially open. I will look into it.

 

I have most of the HKS type 2 modeled and have run a quick analysis on it. Looking really very good and even flowing so far. I will post the results soon.

 

MonZter

[RTz]

720 crank degrees divided by 6 cylinders = 120. So... intake duration would have to be 120 degrees or less to avoid 'overlap'.

[MONZTER]

So once again, Thanks Tony D for the loan of his HKS Type 2 intake for testing.

I was really interested in seeing how this plenum would flow given the success of it over the years. My plenum I have been working on has been plagued with a couple of vortices that have been causing the front two cylinders to run with less airflow. I wanted to see how consistent the HKS would be.

So wouldn’t you know it? the HKS plenum looks pretty good. There is still swirling, but this doesn’t seem to be affecting the flow down the runners like my design is doing. The pressure looks to be even down the runners as well as the velocity.

So check out the pictures below and let me know your comments, I know now I have more work to do on my design to even out the runner flow more.

 

I have posted pictures of cut away views so everybody can see the internal baffling at work. I went as far as to model the plenum very accurately, down to the internal casting bumps for threads, to the shape of the runner inlet. It’s as close to the real thing as I could get.

 

The test was run at 20psi boost 793CFM the inlet ID was 62mm so a inlet velocity of 4880in/sec was used.

 

I will be running less boost on the next analysis and post the results soon.

 

One more thanks to TurboBlueStreak for the lessons in the Floworks software by the use of his models from previous test.

 

Click on the picture for a bigger view in my gallery

 

Jeff

 

 

 

 

 

 

 

 

 

 

 

[OlderThanMe]

Amazing!

[Tony D]

How much of the in depth reverse engineering do you and MonZster plan on publishing online? I ask because I am concerned that very detailed measurements and or very detailed pictures of the internals could work to devalue the few HKS plenums here in the US. I'm all for scientific research as long as it does not devalue the pieces a few of us had to search out for years to get a hold of. After all I'm sure it would not be appreciated by other plenum owners if I started making castings of my plenum and dropping them for sale on Ebay. Not that there is any intention of that in your research, But if enough detailed information is published (such as scale pictures/measurements of the internal plenum) there are those outside of HybridZ that would not hesitate to profit from a knock off of it.

 

Hmmmmm, lets see. They originally sold for $1000. They can now routinely be had on E-Bay for around $200-$250. Exactly how much cheaper do you want the part? Do you REALLY think that ANYONE will be able to replicate the box as Monzster has shown it for $250?

 

If they can, MORE POWER TO THEM WHERE CAN I BUY MINE!

 

"Devalue the plenums here in the USA".... I don't know how much you paid for yours, but if you're concerned that a plenum currently selling for $250 is 'expensive' you may want to consider another hobby.

 

It was modeled precisely to determine it's efficacy at the job. Looks like it was very good at what it was designed to do. Curiously, due to the cost in 1987, I MADE MY OWN after spending several hours staring at one in a speed shop display case and making mental notes of placement and sizing and then replicating it as best I could do. Does that make me a bad guy? I doubt I impacted HKS's sales in 1987. Maybe I should give Monzster my homebuilt plenum to see how it compares? That one could be easily replicated by anyone with aluminum welding capabilities.

 

What would that do to their value then? What if my scratchbuilt aluminum plenum performs similarly? Then why buy the HKS? Then again, who's going to make it for as cheap as you can buy one these days (even at half new cost, or 2X what they currently sell for?)

 

The part is NO LONGER AVAILABLE from HKS. For EVERYONE'S best interest, it's best to have the information available for replication (IMO), and for evaluation against their own designs. It would be one thing if HKS was still producing them, but that hasn't happened for some years now. That someone overpaid with some intent of gouging another L-Owner, such is the RISK you take when you undertake entrepuenrial ventures. Sometimes you eat the bear, sometime the bear eats you. That's the way it goes.

 

Sure, there are guys with fantasy prices on them posted right now (something like $650)---seems to me if someone looks at the flow photos posted they now know FOR SURE the box is WORTH the money, and that's it's most definately NOT (as I was once told) "Just an overpriced cast piece with a big price tag because someone's name is on it... you can build one out of extrusion for a heluva lot less!"

 

Seems that statement has been blown out of the water. Now, anyone got a CARTECH plenum they want to submit to see how it flows? I got a 2X4 Aluminum extrusion surgebox we can model and laugh at...

 

Debunking myths, adding to knowledge. That's what it's all about.

 

And Monzster said it all in his post: "If someone wanted to knock off an HKS Plenum, don't you think they would have done so by now?"

 

Sorry, that got to me. That is so wrongheaded. Sorry.

[Tony D]

Oh, and of course, the aim of helping Monzster out and maybe giving him a direction to go regarding his plenum design---'know where you came from' kind of knowledge. That was another reason. If you can see how HKS addressed the issues, then it may give you an idea how to tackle the same issue. There is no sense reinventing the wheel and wasting all that effort when a good functional example is right there in front of you!

 

Hell, I have two Type 1 Plenums, one Type 2, and an SK Plenum....so I probably have a bit more to loose than most 'speculators' should I choose to sell my plenums after all this knowledge lets me make one that is better....right?

 

The only reason I didn't give him the SK Comp Turbo Box (the second one AZCar 'doesn't know what type it is) was I don't have the baffle for the inside of it.

 

My design was an HKS style external, with the SK Comp Turbo baffle and several diffusers on the bottom, as I couldn't figure out how to segregate the plenum like the HKS was, and because I never actually held it in my hands to look at it, didn't know about the baffling, and could only assume what they did.

 

I mean I got a box, and if he wants to look at the baffling in the post SHO put up, he could probably model it handily and see if there is a flow difference. When we hook up to return the HKS units, I can bring my SK box, as well as my home made versions.

 

Now, I'm curious to see the difference between my design and the simple 2X4 Box Extrusion most people seem happy to use (as well as the CARTECH plenum.)

 

$1500 for a New HKS Type 2 Plenum...that's tasty! Price didn't go up that much since 1989...

[RTz]

...and now we return to our regularly scheduled programming...

[MONZTER]

I ran the test at lower boost on the HKS Plenum. Looks the same, same equal flow distrabusion, so I wont be posting the pics.

 

Can anybody see anything negative about the results above?, If there was room for improvement, what would it be, and how would that be acomplished.

 

I would still like to see less swirling and less bends in the airflow.

[Tony D]

I think the HKS was concerned with straight flow through the carburettor venturis so as to keep them functioning similarly under boost as they would in N/A mode. I can see that the swirling may hinder the flow somewhat, but I think it's the 'unavoidable tradeoff' you get when packaging that much flow in such a small area. On an optimized industrial compressor, the discharge area for that size turbine wheel and that pressure/flow would be probably 10 to 100X what you have in the HKS plenum. And when you have space, you have residence time. The more time you have before making the next process, the more you can do.

 

I suspect with the looks of it, they hit several angles to diffuse the air as much as possible before the main chamber---which is what industrial units do---some add flow straighteners in the channel before next stage of compression when a particularly tight bend/casting is used.

 

As you can see from the links SHO posted, the SK Comp Turbo Box simply has a flat diffuser plate in the box from inlet...don't know how that compares feeding what looks like both ends instead of the three holes the HKS uses, it would seem like the middle carb would be lacking somewhat. My setup was similar but also allowed the air to come in from the bottom of the box, through through many bored holes in the baffle plate acting to diffuse the air somewhat (or so I thought at the time...)

 

It's almost as if the additional plenum volume gave the air the opportunity to swirl--it seems very linear in the upper plenum chamber where the velocities are higher, even with the two bends entering. I wonder if some horizontal flat bars in the lower plenum (or maybe somewhat 'plus' shaped) about equal to bore's centerline and between cyles 2/3 & 4/5 would assist in breaking up the swirling...

 

It's modeled now, I guess it's 'easy to try it' now! LOL

[Slow_Old_Car]

Thats amazing to see a vintage part like that do so well under modern testing mediums.

[DemonZ]

Now, anyone got a CARTECH plenum they want to submit to see how it flows? I got a 2X4 Aluminum extrusion surgebox we can model and laugh at...

 

 

 

A friend of mine had the original Cartech kit. IIRC the plenum was virtually an empty box inside. Your 2x4 extrusion would practically be identical.

[Tony D]

Wasn't Cartech's more like 4X3 or 4X4? It seems squarish from what I remember, as opposed to the rectangular form of the 2X4 Extrusion.

[SHO-Z]

I would be interested in seeing what a 4"x4"x 24" long box with a 3" inlet would flow like. I think most of us start with this set up and modify from there.

 

This is one of the best posts in a while.

[thehelix112]

I agree. This is a good candidate for sticky.

 

Dave

[MONZTER]

I was looking at the analysis of the pressure on the HKS and realized the pressure range on the chart was pretty wide. So I revised the scale and now look at it.. 20psi was put in, but there is more than that in the inlet neck and a big pressure spike at the inlet bends. Looks to me like this intake cannot flow this much air at this much pressure without backing up. Tony D - I think I remember hearing you say the high HP cars would port or cut away some part of the plenum??

 

[MONZTER]

Here are some shots of a standard 4x4x24 box with a 70mm inlet. Same 20psi boost at 793 cfm. Just as expected runner #1 not looking so good.

 

Again, click on the picture for a bigger view:

 

 

[DemonZ]

Tony D,

 

you're right, the Cartech Plenum is probably closer to 4x3. As I recall it was not square though.

[Tony D]

Yes Jeff, the higher horsepower cars seemed to gravitate towards the Type 1 Box---one of mine has holes that are enlarged. I would think the reason they used the earlier boxes was they were available cheaper once the Type 2 came out, they could easily fabricate the inlet plenum from the 'T Log' the Type 1 used for inlet air, and access to the three diffuser holes was a simple matter of taking the front cover off and having at it with a die grinder.

 

As I mentioned, one of the things they had to do at higher pressures was open the holes up to keep the float bowl from overpressurizing, and basically pushing fuel through the jets---as you can see the kind of pressure differential from upper and lower plenum can indeed cause that kind of problem. But it's a 'good' problem insomuch as you simply run very rich as you over-boost. A broken wastegate would result in you dumping fuel into the engine instead of running lean. Clever, no?

 

For an EFI ITB setup, I'm thinking you could play with the hole size, as you don't really need the big pressure differential, you just want the diffusion at as little pressure drop as possible.

 

On carbs, you would want the pressure to be something more. This is the same issue with Modulator Rings...you have to play with their size to fine tune upper end boost enrichment till you get it right.

 

But hey, 'Carburettors are Easy', right? LOL

 

Oh, and on most High-Horsepower Cars back then, it was TWIN turbos for the flow, so off the intercoolers there likely would have been a pipe to each entry hole, instead of that single entry plenum casting. Times change and you can get that flow from a single now---so the inlet plenum may need some revision to better suit the entry to the box.

 

No matter which way you turn it, a 90 degree bend is going to hurt flow. Especially in the tight confines we have in the engine bay in regards to the strut tower...especially if you want to compensate for engine mount rocking (which is not an issue on your car, granted...but for us mortals with pinned stock rubber mounts...the engine may move a bit!)

[MONZTER]

So I took Monday and Tuesday off and took the family to Palm Springs. We stopped at the WWII airplane museum. Some really beautiful stuff in there. Anyway, I was checking out all of the intakes and air scoops on the planes. One thing they all had in common was the inlets for the radiators. All of them had a deep honeycomb "grill" that acted as flow straightners to the turbulent air. Hmm this gives me an idea.

 

Jeff