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You don't need to cap the TB coolant nipples. its just a simple, enclosed passage through hte TB. Unless you're worried about spiders...
 

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There are two "mods" that people have done on the VQ40DE's throttle body for better performance and...with no offense intended for anybody had done them...I think both of them are a waste of time. I have yet to see any dyno results proving that either of these mods makes any difference at all and those that have said they have felt "big gains" or "improved throttle response" have their butt dyno cranked up way to high in my opinion.
First is the throttle body coolant bypass. The reason for coolant running through the throttle body is to keep the throttle actuator and throttle plate from icing up in cold weather. BTW, for those that are going to do this, the lines are 8MM (5/16") and not 3/8", which is why the guys caps were too big in the YouTube vid. Some people have claimed that running the coolant through the throttle body makes the throttle body hot and it warms the air going into the engine. Let's think about this! Think about how fast the air moves through the small opening of the throttle body...not only at idle, but at high RPM. Now ask yourself: "With the amount of time the intake air actually spends within the confines of the throttle body as it's being sucked into the engine, does it really have time to get heated by the temperature of the throttle body, itself?" Of course not! The other argument I've heard is that it keeps the upper intake cooler because coolant isn't going through it anymore with the TB coolant lines bypassed. If anyone has ever removed the throttle body from the upper plenum knows, there is no coolant that runs through the upper plenum; the coolant runs into and out of the throttle body alone. So, if anyone does this mod and can show me dyno runs proving this mod makes any difference, I would love to see it! The next TB "mod" is removing the screen in front of the throttle body. The fine mesh screen is there to keep things from getting into the engine that have gotten past the air filter somehow. The argument is that it "slows down the air flow going into the engine." Now, there could be technically be a little truth to this. If one was to add up the total area that the fine wire mesh takes up in front of the throttle body by calculating the width and length of all those little wires, sure it is going to slow down a little bit of the air flow being pulled into the engine. But, again, in a vehicle as heavy as a Nissan Frontier, Xterra or Pathfinder, is it really going to make a bit of difference in performance? Just my opinion, but I wouldn't think so. Again, if you can show me actual dyno runs that prove it makes a difference, I'd love to see it! I think both of these have more of a, so to speak, "placebo affect," in that people feel like they are getting better performance, rather than them actually seeing real life gains.
 

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I think a lot of this and many "cheap HP gainz!!" are holdovers from Carbureted engines. An analog charge of air and fuel mix in a metal intake manifold with vacuum advanced ignition is NOT the same as air running through plastic intake piping and plastic manifold with Computer controlled injectors injecting fuel right before each intake valve and fired off by computer controlled spark.
 

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I thought that "rule of thumb" being a cooler intake charge helps atomize the fuel better. In 1973 I drag raced...I ran a SS/IA Dodge Demon with an ice packed "cool can" and iced the intake manifold in between runs. Cooler fuel made a noticable difference in ET's. I'm not saying that this small change in bypassing the throttle body is going to be noticeable, but I live in Florida and I don't really need to "pre-heat" the incoming air. JMHO.
 

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I thought that "rule of thumb" being a cooler intake charge helps atomize the fuel better. In 1973 I drag raced...I ran a SS/IA Dodge Demon with an ice packed "cool can" and iced the intake manifold in between runs. Cooler fuel made a noticable difference in ET's. I'm not saying that this small change in bypassing the throttle body is going to be noticeable, but I live in Florida and I don't really need to "pre-heat" the incoming air. JMHO.
Again, a charge of air and a charge of air fuel mix are two completely different things. The fuel is being injected right above the intake valve on a fuel injected engine where in a carbureted engine, you are trying to keep the fuel properly mixed and suspended in the air as it makes its way down the intake runners. NOT the same.
 

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I like the idea of cleaner less busy engine bay.
its less stuff to worry about for the most part, but i doubt you see any gains at all. feel goods maybe?

but i would like to eliminate all hoses and wires and vac lines ect that i can and still keep a properly functioning vehicle.
 

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I like the idea of cleaner less busy engine bay.
its less stuff to worry about for the most part, but i doubt you see any gains at all. feel goods maybe?

but i would like to eliminate all hoses and wires and vac lines ect that i can and still keep a properly functioning vehicle.
The bypass doesn't eliminate any hoses nor does it make the engine bay look "cleaner." All you're doing it pulling two hoses off of the throttle body and connecting them together.
 

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I thought that "rule of thumb" being a cooler intake charge helps atomize the fuel better. In 1973 I drag raced...I ran a SS/IA Dodge Demon with an ice packed "cool can" and iced the intake manifold in between runs. Cooler fuel made a noticable difference in ET's. I'm not saying that this small change in bypassing the throttle body is going to be noticeable, but I live in Florida and I don't really need to "pre-heat" the incoming air. JMHO.
That's a different scenario because you have a metal intake manifold and in 1973, I'm going to say it's a pretty safe bet that had one or more carburetors, which mixes the fuel before it enters the intake manifold (which is still used on a lot of race engines today). The VQ40DE uses a plastic upper plenum on an aluminum intake and the fuel doesn't start getting mixed with the air (as already mentioned) until it is entering the combustion chamber. The plastic plenum isn't going to heat soak like a metal manifold and there is no coolant running through it, as well. So, just have a little coolant flowing through a passage in the throttle body to warm the throttle actuator isn't going to heat up the air charge to any significant degree.
 

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There is no real reason to do this, and will more than likely be the cause of trouble in climates like mine with a very cold winter. There is a valve that shuts off the coolant flow when the engine reaches temp. Short answer, yes, it's only a feel good mod.

It's your truck, your choice, so whatever.

That guy was flooding the site with pretty much useless vids trying to establish a yootoob channel. When told to stop, hasn't been heard of since. Only joined up to post vids.
 

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Never heard of this till now, I like my perfectly running 4.0 just the way it is. I would like to add a chrome tip to my exhaust though.. ought to be good for a couple horses!😎
 

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I had removed the mesh thing probably a year ago before I knew it was a thing. I wasn’t expecting anything different but I figured it could make turbulence in the air flow. I actually forgot that I did it! And yeah I didn’t notice anything different. The coolant bypass thing is rubbish
 

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ya it does.

also less work to remove the intake.
How does it eliminate hoses if you are just taking them off the throttle body and connecting them together? And how often does one pull the upper plenum off? I can see where one would say to do the spark plugs or coils, but you really don't need to pull the plenum off to do that if you know how to do it...and spark plugs aren't due to 105,000 miles, besides.
 

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How does it eliminate hoses if you are just taking them off the throttle body and connecting them together? And how often does one pull the upper plenum off? I can see where one would say to do the spark plugs or coils, but you really don't need to pull the plenum off to do that if you know how to do it...and spark plugs aren't due to 105,000 miles, besides.

if you connect the hose to keep the coolant system happy and shave down the nipples on the throttle body you are removing some clutter for sure.
yea i mean i agree you probably arent removing your intake often enough to make a difference, unless you were in the developing stages of something or kept removing it for troubleshooting reasons.

i havent done it by the way lolol just being devils advocate.
 
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