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Discussion Starter #1
KA24(e) Throttle Body Modification
Short Explanation

Total cost of this mod: ~$50 for the TB, $2 for the gasket, and ~$10 in misc. tools if you don't already have them.

What this mod does? The TB on Nissan cars with the KA24(e) engine (2.4 Liter, 4 Cylinder, DOHC) has a direct bolt-on replacement TB for the stock Z31 TB. Two manufacturer's produced TB's for this engine: Nissan and Hitachi. The Hitachi required some modifications itself...you must replace its linkage (where the cable hook up) with what you already have on the stock TB. The Hitachi linkage only allows about 30 degrees of opening and you need a full 90. You also have to adjust the coolant lines and use a "T" to join two vacuum lines into one. If you're lucky enough to find a Nissan TB you should be able to take of the old and bolt on the new, as the linkage is the same. You can find the KA24(e) engine on 89-91 240SX, Stanza, and pickups. The 240SX's I've seen have never had the Nissan TB...only the Htachi. Stanzas I've seen do have the Nissan, and not the Hitachi. I never saw a truck to see what they sported...but if its a rear wheel drive (like the 240SX) I'd assume it also has the Hitachi.

Gains occur because the TB on the KA24(e) engines have an outlet diameter 10mm larger than on the Z. Both TB's (stock and KA24(e)) have the same size inlet, but the larger outlet allow more air to be sucked in on throttle. The AirFlowMeter and computer compensate for the higher flow of air with more fuel. More air/fuel mixture = more explosion = more HP. This won't give you gains like a turbo. The extra "boost" is small, but it is there. You will get better throttle response and a bit more kick outta your engine. Good mod and worth it.

Labor time depends on your approach. You HAVE to match port the intake collector for this mod to do you any good. The intake collector inlet is ALREADY bigger than the stock Z outlet by about 5-6mm...so you only need to port it out 4-5 mm more (by diameter...not on all sides [radius]). I suggest removing the intake collector to port match. Though it takes a long time, I wouldn't chance getting metal scraps down into your manifold and then down the intake valves into the cylinders. Some say stuffing a towel inside really tight is suffiecient, but I wouldn't chance it. Pull it off, stuff a towel down there, and then thoroughly wash it out before sticking it back on. I also took advantage when I had the intake collector off to paint my driver's side valve cover to match the rest of my newly painted engine parts.

For the full explanation,
Why replace the 300ZX TB? The diameter of the Butterfly Valve is almost 1cm Smaller than the TB's used on the Nissan KA24(e) Engines, which happen to be a direct bolt on replacement on the 300ZX. So replacing the 300ZX TB with the larger diameter TB from an 89-91 240SX, Stanza, or Pickup will allow more air to flow/be sucked into the enigne. Now, you're gonna maintain the same diameters's below the TB (the cylinders/valve ports/intake manifold passages, etc), so this mod isn't gonna give you a whole lot of power, but the larger amount of air flow and slightly higher velocity will allow just enough more air/fuel mixture to be compressed in each stroke that it'll give you a little pep. Your engine will have an easier time breathing at idle and low RPM when the air isn't being sucked/flowing as much. Consider bronchitis...where your bronchial tubes swell up making it hard to breath..the 240SX TB brings down the"swelling" of the enigne's respiratory system. Better Throttle response will make the car feel a bit lighter, easier to control the revs, and smoother idling..and of course a bit of HP.

It would probably be more helpful to change calling this the "240SX TB Conversion" to the "Nissan KA24(e) Engine TB Conversion" (or the "Stanza TB Conversion")...I have yet to see the Nissan TB on a 240SX).
After doing this mod I felt much better low-end response...4th/5th gear runs are a lot more fun now also. I took my car for a good 90 mile trip and hit the throttle several times at 3K in 4th, and the quick response and acceleration is much better. The car feels a lighter than before and don't take this wrong and blow it up into a big discussion, but driving my NA now feels a bit more like when I test drove my Buddy Al's Turbo Z31. I remember an Eclipse and a BMW on the freeway in San Diego come up in my rear view mirror going 100 while I was going 70 (this in the Turbo Z) and it seems as soon as I hit the throttle the car just took off and I was caught up to them in no time...I can feel a bit of that kick now after having done the TB conversion.

At higher RPM I don't feel a difference. I suspected that I would so I was a bit dissapointed, but the low-end gain and smoother throttle response and idle make this MOD worth it.

*not written by me...but a very good read*
 

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And completely wrong about the gains that will be made. The air flow will not be increased becuase the it will still bottle neck at the upper intake manifold, lower intake manifold, and heads. It's already been discused a lot that this mod does nothing for hp gains or 1/4 mile unless you have an Engloid plenum or pathy manifold. Even then full advantage of the larger TB won't be had until the heads are ported. All the larger TB will do is give a better tip in or throttle response but people confuse that with wide open throttle. Tip in is how much you have to press the gas pedal down to open the butterfly in the TB to get acceleration. With the larger TB the butterfly is larger so you have to press the gas pedal less to get the same throttle repsonse than with the stock unit. This gives you that feel that you accel faster having to press the gas pedal less. However under a racing application where you are having the pedal all the way down and the butterfly all the way open, wide open throttle, the air will flow in at the same rate as the stock unit becuase it will bottle neck at the intake manifold. Sure you can port the opening of the manifold to the same 60mm but you can't port the insides of the manifold which is where Engloids plenum comes in handy. It's a good write up for confusing people is all.
 

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is there a site to show you how to port them?? WHere can i get the Engloid plenum??
 

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I'm not exactly sure how Engloid does it. It's my understanding that he cuts the top of the manifold off, gutts the inside as well as polishes it, then welds the cover back on. Then again that sounds way too simple. I'm sure it's more involved than that. The only advice I can give is to email him or call him out over at z31.com and see if he will share his secrets with you. I do know that you have to know a good bit about welding and have some knowledge of air flow for these engines if you want to do a proper job. As for the path manifold upgrade, in my opinion it's not worth it. Amoung the procedure to make the conversion work you need to cut a hole in your hood for manifold clearance or add some sort of custom hood scoop, you need to custom make a lower intake manifold to mate betten the pathy manifold and heads, and you need to redirect the intake plumbing as the pathy TB is faced a different dircetion. There is more but just those three issues are enough to discourage me. Also for those wondering just how much there is to be gained from intake manifold work, it isn't much if you have a non turbo. For the non turbo it would be 5 or less hp that includes if you have the 60mm tb. I think Engloid was selling his for about 600 bucks so it's up to you to decide if 600 is worth 5hp. For a turbo it's obviously more, as with everything else, but it honestly isn't needed to make good power. You can get plenty of power with the stock manifold. Basicly do it if you are at the point where you have run out of things to do.
 

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Discussion Starter #8
A while ago, Engloid was selling the plenums for less than $400...the only reason it got up to $661 or whatever, is because he put one up on Ebay.

Another easier way to make the pathy intake fit, is to make some custom engine mounts that drop the whole engine enough to make it fit.

<http://mywebpages.comcast.net/engloid/index.html>
 

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with the larger throttle body and a k&n cone filter I have gained a slight amount of top end power (approx. above 3800rpm) but have lost a slight amount on the bottom end. I have had my tb for two years and will not change back but the bottom line is there is not much change with this mod. F.Y.I an engine doesnt suck air in,----the air is pushed in by atmospheric pressure 14.7 psi at sea level.
 

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Discussion Starter #10
um...nope sorry, you're wrong. Of course the engine pulls the air in, that's why it creates a vacuum, durh?

<http://www.howstuffworks.com>
 

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Also fire105 the power increase you felt comes only from the k&n filter. I gaurantee that if you went back to your stock TB you would not see any difference in performance. Of course there will be the chance of a physcological affect but do a before and after dyno or before and after track test and you will see there is no difference. Also I'm not sure why you lost low end power. Most people, including myself, noticed a good bit of pick up in the higher rpm band from the k&n filter like you did but at the same time we didn't lose any low end power. In fact with all the mods I have on my 300zx I never lost any low end power. Then again you don't say if you have a turbo or non turbo.
 

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yeah pressure at sea level is 1.01 x 10^5 Pascals. Thats a physics thing for ya. An engine sucks air in, hence the air"INTAKE" and such. Air induction. anyway the atmospheric pressure would hinder that at most since it is pushing down and not pulling up. nice try. a high school physics student just told yo ass.

hey farva i love you

gimme a kiss :()
 

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atmospheric pressure pushes the air into the intake thats thats why they call it the intake. without atmospeheric pressure when the piston travels down no air would go into the cylinder. also thats why blowers and turbos make more power is because they push more air into the motor than what the atmosphere can. You dont know anything Punk!!
 

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Discussion Starter #14
are you retarded????

The pressure that forces the air into the cylinder comes from the cylinder creating a low pressure area which the outside air (higher pressure) fills. This is called a vacuum. Why does my boost gauge read negative pressure at idle? have you ever put your hand over a cone air filter with the car running....it is just like a vacuum. Do you understand how engine braking works? ARE YOU EVEN TALKING!!!!!

SERIOUSLY!!!
 

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It's a fine distinction.
If atmospheric pressure has no bearing on the process, then why does performance drop with alititude?



Post Edited (May 10, 2:43am)
 

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Discussion Starter #16
Becuase air is less dense at higher altitudes....less dense means less Oxygen, less Oxygen means less fuel, less fuel means less power.
 

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You have one part right---there is a low pressure (negetive pressure in the cylinder)---but that is not what creates the pressure entering the cylinder, atmospheric pressure forces the air into the cylinder. when you suck on a straw how does the liquid go up the straw---you create a low pressure in your mouth and the atmopheric pressure pushes the liquid up the straw. why does your cheeks colapse inwards when you are doing the sucking? because of the same thing--when you are creating the low pressure in your mouth (by the initial muscle action) the atmospheric pressure is what actually forces your cheeks in. suction or vacume is just a description of low presssure, without atmospheric pressure there wouldnt be any suction. when you put a suction cup on a wall what holds it to the wall?--you colapse the suction cup creating a low pressure inside which then allows the atmospheric pressure to hold it against the wall, so why is it sometimes hard to remove that suction cup? because there is 14.7 pounds of presssure pushing on the cup, when you remove the cup you get the popping sound because the low pressure inside is being replaced with high pressure(atmospheric). If you put a piece of paper on your air cleaner while engine is running what is holding the paper to the filter? there is a low pressure at the intake and the higher atmospheric pressure is holding it down. WITHOUT THE ATMOSPHERIC PRESSURE NO AIR WOULD BE GOING INTO THE CYLINDER.
 

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Air at altitude is also happens to be at lower absolute pressure, which naturally implies lower density.
 

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ONE LAST THOUGHT, we grow up thinking that vacume or suction is its own thing or an action-- and it is sometimes hard to accept that it is not an action but only a result of an action---Positive pressure or in this case atmospheric pressure applied to an area of lower pressure. by providing a void of lower pressure (cylinder) the atmospheric pressure (action) is allowed to have its way. Regarding the original question and 280z/300zz comments. I installed my TB before the K&N filter and did have slight power gains at full throttle and slightly lower bottom end, the K&N didnt help much more. Ususally when you open up an engine intake or exhaust (and depending on how much) you will have a slight power loss and/or torque at the bottom end. when I use the word slight Im talking about very little. The bottom line still is the TB is not worth doing the mod on a stock n/a engine.
 
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