Personally I disagree with some of your disagreements

The material used in the spacers IS low heat transfer material, this isn't for nothing. less heat from the Upper Plenum to the lower and vise-versa translates to overall lower charge temperatures. Lower charge temps result in more power and greater efficiency, put simply.

This is evident in something you yourself noted, that the differenc between a tiny 5/16" spacer and a much larger 5/8" spacer is little to nil.

I do believe that the flow the to front cylinders is greatly improved by a little more room for air up front of the plenum, but I also believe that the bulk, or at least, the big other half of this is lower intake temps.

This is further evident when you compare the 3.5 in the maxima, which has a completely different IM. The Maxima proves the same gains from these spacers, with the same negligable difference between a 5/16" and 5/8". The maxima doesn't suffer from this apparent 'lack of airflow' to the front 2 cylinders, so none of the spacers benefit can be attributed to that in that configuration (same engine).

Just something to chew on

 

Has anyone had the ignition switch fuse burn out on them before? My 03 gsedan's burnt out and its making me wonder what causes this. My mileage is almost at the 100K mark so is it possible that its one of those things that could just burn out over time or is there a problem that I am not seeing?

 

While the spacer may give your upper plenum slightly lower temps by distancing it from the hot engine block, well, just try it without the Iso Thermal. You still won't be able to rest your hand on the upper plenum after a few dyno runs. I don't think that's cool enough to make a difference. Ask an engineer, better airflow, therefore more fuel throughout is all a spacer does, period.

 

So in order to get a even drop we have to lower the front more on our G sedans? if you lower 1.5“ in the back you need a 2“ in the front? Because of the way the our fenders are higher in the front??

 

That is correct.

 

Really?? Thought it wasnt true, buddy of mine told me but i didn't believe
Him. So i was searching on the suspension and brake thread and it sald that the g35 coupe tien s-techs lower the coupe 1.2“ front .9“ in the rear plus another .5“ on our sedans making it 1.7 front 1.2“ rear seems like this is the best even drop then since the front is higher??

 

Nah Brah!

The spacer doesn't lower temperatures by increasing total distance from the block. That has little to no effect on the reaction here.
The bulk of the upper Intake Manifold temperature is from heat CONDUCTION (transfer of heat via actual contact), as such:

Block heats up >> Lower Intake Manifold heats up >> Upper intake manifold heats up

So by putting a spacer/insulator between the Lower IM and the Upper IM, you slow that heat transfer signifigantly. The result is incoming air being cooler.

Colder air is denser. Colder air helps the combustion flame move more steadily and predictibly, it also allows more advanced timing.
The benefit of cold air is plentiful, the end result everone here cares about is HP, Put simply: Colder air nets higher Output potential.

Any spacer material that doesn't conduct heat well will have this result. ie. Plastic, Cork, rubber. The thicker it is the greater the effect up to a certain point, and depending on the material used.

I lol'd at this.
I don't mean to call you out, just as you didn't to the other dude. Just as you were, I seek to clarify.

There are 2 simple facts at work, that none of us can deny:

1. Isolating materials keep transfer of heat to a minimum, or at the least, perhaps better put, slow heat transfer.
This equates to another fact = Colder air nets more power potential in an engine.

2. Better "airflow" (using term very loosely to symbolize "ideal" flow) characteristics in the intake system allows better air flow into, and out of the engine.
This also equates to another fact = Better "airflow" in an engine nets more power potential

The truth is, none of us have signifigant factual research on which component has the most effect. What we do know is that BOTH factors are certainly being changed with the spacers readily available on the market. To what degree (no pun intended), and to what benefit hasn't really been figured out for the air flow portion, but the difference in temperature is evident and has been measured.

 

We'll just work on the simple concepts first. Most spacer as made of metal, either way, metal still conducts heat. But none of that matters at all because there is no point in using a spacer to cool the upper manifold when you can install an Iso Thermal gasket that significantly lowers temps of both upper and lower manifolds.

 

As for all of this... do your research, search Motordyne and all the research he did. The info is all here somewhere. There is a reason why his products are so good - he actually put the research into designing the parts, and a lot of it was shared here on this forum at the beginning. There were a lot of independent tests of all of this as well.

 

Look... there's a simple solution to all of this.
1. Plastic intake tube, metal is just going to heat-soak.
2. Plastic plenum. Again, heat.
3. What good is a plastic upper plenum if you have a hot lower plenum.... so plastic lower plenum.
4. This of course necessitates: plastic manifold.
5. now obviously, this would be all moot if we didn't go ahead and... yes, you guessed it: plastic heads.
6. This leaves only the block itself, ideally you would also want to get a plastic block.
7...... you now have a Kia.

 

ROFL

 

I'm not debating whether the spacer makes power, just saying there's more than one aspect to it.

Similar gains from the maxima, same type of guy as Motordyne, NWP engineering. Same story just for the FWD version. And the other side of things, focussed on the Temp drop.

http://www.nwpengineering.com/Phenol...rs.html#VQ35DE

IJS, there's more to it than one or the other. It was meant as something to think about, not as an argument.

When you find something that works you roll with it, that's all these guys have done here, they didn't part the red sea. They found the same gains from a spacer. With the EXACT same relation in thickness differential, 5/16" being the largest gain point across the range.

Don't you think there's something to that? Research around on other cars that use spacers, the argument of intake runner length vs. temp drop is not a new one. Gains are usually similar on other engines with Aluminum/steel IMs.

You'll note that cars with Plastic plenums don't normally gain from a spacer, or gain very very little. Let that speak what it will. Again, I personally think both are at work here.

 

I still don't see how the temp drop of the upper plenum from the addition of a spacer helps any bit since the upper manifold still get hot to the touch after the installation of the spacer (I've gone through a few different spacers). Even if the upper plenum is cool enough to touch, the hot lower plenum is still a problem. The best solution is to put a gasket to stop the heat from transferring between the motor itself and the lower plenum. This way you can actually rest your hand comfortably on the upper plenum (and even the lower plenum too if you can reach it), meaning overall temps are actually decreased enough to finally make a difference. Why half-@ss a job with a cool upper plenum while your lower plenum still gets hot as hell?

The thing that makes Motordyne's research significant, well let's put it this way: He found that the front runners were not getting enough air, so he found a way to machine it so air flows through much better. While all of this seems easy, take note that many people have tried to duplicate what he's done, but none have been successful. To him, it's all about the airflow, how every nook and cranny effects the way the air flows inside the manifold, or piping, etc... that's why even his exhausts are such a big deal to the guys on this forum. True, there are plenty of ways to get around this without the engineering know-how this guy has, but that just goes to show what we can learn from him.

I feel the manifold on the G could have been designed a bit better. It seems like they either rushed it out on a schedule, or they cut a lot of corners in production to lower costs. Plastic manifolds are much cheaper to build to the specs that you want, so it makes sense that they were able to make it an efficient piece leaving little room for improvements.

 

Just something to think about...

 

^ All materials have their own natural frequency, aluminum has one and so does Carbon Fiber. You can build two plenums One from Aluminum and one from Carbon Fiber. Carbon Fiber intake will perform better.

Once you go WOT the air is moving pretty quickly, and it only moves faster at higher RPMs. So generally heat soak will not be an issue here.

The Spacer is an interesting piece. Its not only altering the plenums capacity but changing how the wave inside the plenum propagates. It can also explain why different size spacers ie Bigger ones do not perform as well.