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HKS Plenum


savageskaterkid

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Yes, avoid #1.

#2&3 are HKS Type 1

#4 Looks like a polished HKS Type 2, with 'HKS Surge Tank' ground off. The BOV is mounted exactly as my Type 2 is, and looks to be the same BOV as well...I would think if they were making a knockoff, they would use what they could find, rather than HKS Application SPecific Hardware.

 

Note the Radiator support work on that Red Car! Ahhh, memories!

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Yes, if you find a cartech manifold, just throw it away like the garbage it is. I'll let you use my trashcan, even. In fact, I'll pay for shipping so I can personally "take care of it" for you, we don't want to run any risk junk like that might make it onto a Z.

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I am familiar with an early HKS plenum that had 2 downward facing intakes. Obviously for twin turbo setups. However the type 2 plenums were all forward facing. The type 2 plenums are the better performing plenums. SKS and early HKS plenums are about the same in price. Type 2 plenums are a little more pricey. All can be found over on yahoo with some regularity. Easiest way to search is L (gata). Have to be able to type the gata part in japanese characters though....

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Like Greenmonster said, Type 1 can be either-or. Many times a forward facing adapter was put to the 'dual inlets' when intercooled. Though again, the pipe coming in from the bottom worked nicely in a 5-10 psi setup unintercooled. It was well over 200HP on a stock L28 in that form.

 

I have seen the Type 1 boxes with over 600 HP (444Kw).

Type 2 Boxes were used in later years and have some advantages in packaging, and slightly different internal airflow.

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Whats makes the cartech piece garbage?

It's not JDM? I guess the people who weren't being sarcastic will have to answer that for you.

 

I'm going to use it. Joel didn't have any problems snapping Z31 CVs like twigs when he was using one on his TWM 6TB setup.

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Yes, if you find a cartech manifold, just throw it away like the garbage it is. I'll let you use my trashcan, even. In fact, I'll pay for shipping so I can personally "take care of it" for you, we don't want to run any risk junk like that might make it onto a Z.

 

I'm going to point out this much, All jesting aside:

 

If the car realy and truly has blowthrough CARBURETTORS, I would throw a Cartech Plenum in the Trash. ITB's and Carburettors are like apples and oranges, and conclusions drawn from one setup in one condition can not be applied to another, and in this case carbs are VERY different than EFI when this particular piece is applied to them. Carbs will have a tip-in transient lean spot that WILL NOT GO AWAY unless you jet your car SO big your mileage gets shot to hell with a Cartech Plenum, or any of the simpler, cheaper, EASIER alternatives like home-made plenums constructed out of 2X4" Extruded Box Tubing. And even, jetted fatter than Oprah, that might not do it mask the transient lean situation. This may have been a combination of things including the flow rates on my compressor... but the Cartech, as well as 'knockoff boxes' and the owners I talked to ALL had the EXACT same problem with a transient tip-in from hikghway cruise that caused bucking, popping, and other ill drivability issues. At WOT, all three of the boxes subjectively felt the same, though above 130 mph, the smaller plenum of the Cartech seemed to be somewhat limiting in the 'punch' when boost came on compared to the HKS unit. Sure, you can make power with them, seen 425 at the rear wheels on some people here in So Cal with that setup...but they all had the same issue as me on transient lean during highway cruise. Your car does not live at WOT. It lives at or near peak torque with miniscule throttle openings most of the time...and the difference between the Cartech setup and the others is like night and day. For racing? Who cares...anybody can make big power, you can use PVC Sewer Pipe for your plenum with epoxied flanges if it holds together. That is not the issue nor the question. Being "JDM" has nothing to do with it. It has to do with the basic engineering behind the airflow into the box under pressure and the resultant issues of fuel metering flow through the main venturis as they transition from idle to main. You CAN use a simple box and pressurize the float bowls and it will "Work"... This is the Cartech Approach. But if you take a more nuanced engineering approach to the issue and want it to 'work' at more than just WOT then something has to be done to improve partial throttle drivability, notably tip-in and light throttle applications. After 30% opening, it works fine. But that transition is a bitch! I never got it right, and countless others had the same buggaboo. They chose to live with it, I'm sure you could too. Should you HAVE to is the real question. With the availability of HKS and SK plenums---the answer is 'no'!

 

For EFI, it is somewhat more suitable. If you have ITB's then a Cartech box would work somewhat better than if you had carbs on there as you are using programmable EFI and can take out the transient lean issue with accel shot or some other form of precise fueling in the 100-120kpa range. (But I was under the impression that this unit was being spec'd for CARBS and not ITB's...) Mine incessantly popped between a manifold vacuum of "0" to 2psi, after which all was good and it ran like a raped ape. But running at cruise at 60 mph, you tended to use a lot more throttle with the Cartech box to make sure you quickly went onto boost at 3psi so the car wouldn't buck or pop. My final straw was driving up a 22 mile grade of some miniscule rate into a headwind, the car just would not settle on a attitude that didn't have it coughing and popping every few hundred yards. I drove this grade several times with the HKS box and NEVER had this issue. It was this annoying drivability issue that cemented my choice to go programmable EFI once and for all. 99.999% of the time, the car was flawless (other than the combined mileage of 17mpg in daily drive use---equivalent to what the car did with SU's when it was N/A!!!).

 

Putting that smaller plenum on there screwed it all up. There is more to boosting a carb than simply putting a box on the inlet and jetting it fat (Which is what you have to do with the Cartech). At that point I simply wasn't going to get into making modulator rings and doing testing on them. I had had it. I'm sure with modulator rings I could have MADE the box work, and likely I would have needed 32 or 34mm Modulator Rings. But why screw with it when an EFI system won't have that issue at all, and instead of fixing a problem mechanically, I can tune it with the hardware currently on the vehicle. And if I cam it later, I simply click some keyboard keys and I'm done, instead of getting out the Bridgeport and machining aluminum sheets... Curiously, when I boosted mine for the first time using the HKS Style box with the jetting from the car in N/A state, I went REALLY rich under boost. I actually moved down in some of the jet sizes when putting a turbo onto the same carbs on the same car, on the same engine. Anybody who says 'carbs are easy' in reference to jetting under boost hasn't done it, or had the results quantified independently!

 

But I digress...

 

Even for EFI, as MONZSTER is finding out, the plenum selection for an ITB setup is more than simply a box as well, and baffling the inlet to allow for diffusion of incoming airflow makes for a more balanced and equal flow into all cylinders under boost, rather than starving the first two at the expense of overfeeding the rear two...which gives the nod to the HKS and SK plenums even in ITB service as well.

 

You may think you want that Cartech Box....but when you try the alternative and do it over long enough of a timeframe you will see what I mean.

 

A curious historical note, Jim Wolf Technology in the 80's was making blowthrough carburetted setups. He utilized the HKS Type-1 Box, and not the Cartech. With the HKS box ALONE selling for over $1000, why would he use that box over the Cartech system which I'm sure he could have gotten a big discount on as a volume seller? Why did JWT choose the HKS Type-1... Just a note in history that makes you wonder. I didn't know about this till two or so years ago when someone sold an 80's built JWT L-Engine and it was confirmed that was the configuration. I didn't think ANYBODY here in the USA was equipping these engines with HKS Turbo Components.

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Is the SK piece more like the type 1 or type 2 hks? Front mount inlet, or side mount inlet?

 

It is a 'top mount'...add that to the mix.

 

There is an adapter that goes on the inlets (which can be in two different places) that points forward, though, so you have several options.

 

The biggest difference between the SK and the HKS is that both HKS plenums utilize cast-in baffling to diffuse the air, and separate the airflows to give a higher-pressure zone in the float bowls under boost, where the SK has a simple 2mm thick baffle that is secured in with screws after mounting the unit.

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It is a 'top mount'...add that to the mix.

 

There is an adapter that goes on the inlets (which can be in two different places) that points forward, though, so you have several options.

 

The biggest difference between the SK and the HKS is that both HKS plenums utilize cast-in baffling to diffuse the air, and separate the airflows to give a higher-pressure zone in the float bowls under boost, where the SK has a simple 2mm thick baffle that is secured in with screws after mounting the unit.

 

Do you have any pictures of an SK piece?

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