Would there be any conceiveable gain from coating the inside of a CAI tube with a product like Tropics shield (teflon based car polish).

Their site claims it can reduce wind resistance. I just thought that higher air velocity could be acheived in long CAI tubes if the walls were had less friction.

F/S:G35/350Z/FX35/Altima Grounding Kits

What are you running? Brake Setup Poll -- Plenum/Spacer/Intake Manifold

The real problem inside intakes is the dirt that accumulates along the interior walls. I'd recommend keeping your CAI clean by running a towel through it wetted with alcohol. The polish idea is actually a good idea for stock intakes where the air path crosses part of the car body or hood -- like it does in the A32. People never think about cleaning the space on the hood that sits right above the scoop.

The problem with putting it inside a CAI is how would you lay down a clean, clear coat on the inside surfaces if the polish produces a glaze?

My suggestion is to use only a Spray and Wipe quick wax that leaves no residue using a microfiber rab wrapped around a flexible rod like those used to clean out dryer vents (or toilets)

And as far as wax/oil is concerned. I'm more worried about the K&N oil than the wax. I read the article that K&N put out, but I've always had problems with K&N oil even when it wasn't me applying it.

The air would not speed up as the center mass of air glides over the boundary layer anyways.

My goal was to simply eliminate that variation in velocity.

As many have said, engines are nothing more than integrated air pumps that we leech energy off of.

I will probably test this idea out once I purchase a CAI. ATM my carbon/fiberglass projects are taking presidence.

No, the boundary layer slows due to friction, but acts like a roller bearing to the air traveling over it. Think of it as a piece of ice on a metal plate. The fluid separating the solid ice and solid metal is the boundary layer, as you push the ice forward it glides over the liquid.

If this was such a big deal the exterior of the car traveling at the same speed (approx. 80 MPH) would produce so much drag and separation of the airflow that you'd get 5 MPG. Waxing your car would gain you 20 HP, lol.

This is precisely the logic I'm using. Tropics shield advertises that their teflon based polish actually reduces drag and can improve fuel economy at hwy speeds.

Now there are two realms of thought on this. 1) It's a stupid advertisting ploy.

2) Teflon is the slickest substance available to the public. Even geckos can't stick to it. Reducing surface friction could in theory (very loose theory) improve drag as well.

If teflon based polishes or paints could make even the smallest decrease in Cf it would be used on aircraft. I have never heard of them being used in such an application.

I have seen teflon used in boats where there is a huge loss to friction with the water.

You'd also think that race cars would use teflon lined ports, but they don't.

For an intake you really aren't going to see any gains. Seriously. There are much larger losses involved in the intake system that have cheap solutions.

An excellent exercise is to measure the pressure drop from atmospheric pressure from the beginning to end runners prior to head say where the injectors spray fuel.

Flow benches use ~~ 25" H20 or a total of 25/27.7 = 0.9025 psi of psi LOSS from earth's atmosphere...................how the 0.9 psi loss is allocated across the entire intake system is a good study.

I'm currently doing my lower division work for a BA in Pure mathematics, but engineering keeps pulling me it's way.

Thanks for the direction Q45tech.

The intake air box and filter might be 1.0%
The MAF might be 1.25%
The air duct might be 0.5%
The TB might be 1.25%
Leaving 2% for plenum and runners to the head.

A real expert with unlimited testing and time might achieve a 10-15% [of 6%] improvement over factory engines,

Not sure how significant a 1% loss improvement is - 3 HP out of 300.

Houston 240sx owners click here!

Texas 240sx owners click here!

the solution? learn to lay composites. take stick of PVC of largest size you can fit, up to ~4". larger is probably still better, but it starts getting impractical. by all means try 6" or 8" if you like. cap one end, *fill* it with sand, pack, then cap other end. use light heat to bend to right shape. use carbon fiber (or fiberglass on the cheap, but big PVC pipe isn't that cheap either) sock/sleeve, slide it over the shaped part. lay it up, bag, etc. when dry, cut whole thing in half lengthwise to remove first layer of carbon from PVC. then slide second layer of sock over first, use zip-ties at ends to hold it together, and maybe a couple in between. lay up again, add third layer if desired. make sure you used a gel coat agent between the first layer and the PVC.
end product: super smooth intake surface with no imperfections or flow impediments in it, and also happens to weigh next to nothing. total cost <$100, also.

What's the purpose of filling it with sand? I got lost there.

I have done several experiments with modding the stock intake, using a manometer with the high pressure end routed to the top half of the air box, and the low pressure end at the mouth of the intake. What I'm looking to find is a drop in "negative boost."

The stock air intake for the 4th Gen A32 produces -12 inches of water (standard measurement) at WOT when hitting 60mph. That's my baseline.

Removing the elbow going to the resonator and blocking off the opening in the intake "tube" (essentially, everything after the scoop and before the air box) will drop the negative pressure by about 3" H20. Removing the hour-glass splitter in the mouth of the scoop (I explained that on my CarDoman page) and covering up the holes drops it an additional 3"

So, doing two basic mods will yield a significant increase in air flow.

I'm going to create a post explaining all of the mods I've tried and tested out.

I'm a math major, we take our double negatives very seriously

That is that MOST, if not all, fluid dynamics theories apply to movement in a straight line. Airflow in an automotive application NEVER flows in a straight line however. In simple layman's terms, air does NOT like to turn. When it's direction is altered, it tends to pile up, as it loses velocity, just like a car does when following a high-speed curve. That pile-up of air becomes an obstruction to further air flow. The more volume and velocity, the worse the condition becomes. The air intake system on modern cars is LOADED with right-angle bends, all of which are detrimental to air flow.

Another factor is that flow increases exponentially, not linearly as diameter of the conduit increases. Accordingly, for example, a 4" pipe doesn't flow 1/3 more fluid/air than a 3", but considerably more (I forgot the formula).

So, improving airflow by smoothing intake walls will help, but not necessarily in a great amount. Straightening airflow would produce much greater improvements, but that's not easy in the modern intake systems. So would increasing the size of the system. Now, with older systems, turbulence of the intake charge was important, but with modern fuel injection systems and combustion chamber design, it's not that critical, so enlarging intake size has become more relevent to efficiency.

Polish and coat your intake systems all you like. While it will give you some improvement, that improvement will be moderate at best. Enlarging your piping and straightening it will do far more. So will placing the mouth of the intake in a high-pressure area that is not plagued with turbulence, which can negate the benefits.

So, engineers, tell me where I'm wrong.

3" diameter= 7.07 sq. in. cross section

4" diameter= 12.57 sq. in. cross section

78% volumetric increase.

The issue with widening the intake is creating more turbulence (at least that's what I see).

A slight increase may assist in allowing the main flow to be maximized to the size of the throttle inlet, but venturing too large will make the air "tumble" on itself as the core travels faster than the contact layer.

I think we need intakes that vary in size depending on throttle position

That being said, the old hot-rodding techniques were only good because of the inherently restricted intake and exhaust paths common in stock engine of their day. Manufacturers' engineers nowadays have addressed these faults in modern designs and eliminated many and much of the problems solved by backyard mechaincs of years ago. Now gains are few and hard to come by. Witness for example the many efforts to increase horsepower in Q45s, wherein intake mods and straight-through exhaust systems produce tiny gains if any, never commensurate with costs.

In real life, I seriously doubt much can be done to increase horsepower in modern Q45s absent forced induction. Current designs are really state of the art, and leave little room for improvement. The engineers at Nissan have done a yeoman job, and given us a small displacement V8 engine that produces power considerably out of proportion to its displacement.

When I first started messing with cars in 1955, a 272 c.i. motor that produced 340 HP would only have been possible with supercharging and nitromethane. Today, we get it from a naturally aspirated motor that runs on 91 octane fuel!

Now watch the engineers at Nissan make a liar out of me and increase displacement by a nominal 10% to 5.0 liters and bump HP by 20% or more to around 425 or even 450 HP. They are incredibly intelligent and innovative, and trying to outsmart them is a fool's errand.

Doncha just love it?

The plenum starves the front two cylinders. The intake tube has sound dampening and a water collection tank.

The exhaust is 20lbs too heavy and reduces power by 10-20 hp.

As for too much weight in your exhaust sytem, that may be true. It was designed to produce acceptible noise limits and still live for a long time. A lighter exhaust system will help improve overall performance if only by virtues of weight reduction, but I'm not sure how much actual horsepower gain you'll get from an aftermarket exhaust, and it will have a shorter life unless made of titanium, expensive to say the least. 306 HP from current G35s and 330 HP from a 3.7 liter V6 in the latest G37 coupe is impressive by any standards. Updating earlier G35 versions to these levels is cost prohibitive, so maybe a new G37 is in your future?

FWIW, I've driven the new G37 coupe, and it's F-F-F-F-FAST! Get one and blame it on me.

Only from the 5 or so manufacturers that make plenum spacers for our G35s, add that to the 3 or so manufacturers that make replacement or modified plenums. It's a well known fact in our neck of the woods. With the proper plenum spacers, owners have seen 15-20 hp increases in the mid-range with 5-7 peak HP.

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As for too much weight in your exhaust sytem, that may be true. It was designed to produce acceptible noise limits and still live for a long time. A lighter exhaust system will help improve overall performance if only by virtues of weight reduction, but I'm not sure how much actual horsepower gain you'll get from an aftermarket exhaust, and it will have a shorter life unless made of titanium, expensive to say the least.

I think all of the catback exhausts increase performance by AT LEAST 10 hp and some torque.

They are all fairly expensive with the least expensive being $800 on discount.

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306 HP from current G35s and 330 HP from a 3.7 liter V6 in the latest G37 coupe is impressive by any standards. Updating earlier G35 versions to these levels is cost prohibitive, so maybe a new G37 is in your future? FWIW, I've driven the new G37 coupe, and it's F-F-F-F-FAST! Get one and blame it on me.

I have the 298 hp 6MT. Other than the fuel efficiency gains, I don't see the reason to buy a car that has 302 more hp and weight 400lbs more lol.

My next project is going to be a CF intake for the G35 just to help it breate better. I'm not sure I'll go through the trouble of testing and redesigning for efficiency, but the weight loss and a smoother path should yield some positive results.

My suggestion is to modify the stock intake. Get a manometer and start testing stuff. I think you'll find there is little restriction (maybe 10" H2O at most, which equates to a "massive"... 0.36 PSI).

The Q45 is not that superior of a design. The engine has it's good points, and the aftermarket is non-existent. There simply is no exhaust tuning that has been done to the car, and it's market is full of simple bolt-ons of the day.

Very few factory engines out there have little to gain. Look at engines like the F20C (S2000), and B18C5 (Integra Type-R) which are MUCH more efficient. If you could match the efficiency of an F20C in a VQ45DE it would output 540 HP. That's what actual tuning can produce.

One of the new members in our forum added a plenum spacer and intake and got a 10 HP peak improvement and an average of 20 HP throughout the power band (dynoed before and after).

Based on that, I'd say there is much to be improved. I have heard that the true CAI intakes for the G35 lower power, but I'm just talking about removing turbulence and straightening out the intake.

Yes, I want to decrease negative boost, or to put it another way, increase air flow enough to decrease the negative air pressure of -12" H2O.

BTW, I can confirm that air intakes larger than 3" in diameter are counter-productive to my 4th Gen. The square stock intake is smaller in area than an equivalent 3" tube.

Because it's that hard to replace the resonator with a straight pipe...

Huh?

The Z pipe just removes the helmholtz resonation box. You could do the same thing with a 3" section of pipe and a can of black spray paint.

I guess I'm lost. I'm arguing that there are significant gains to be had (in efficiency, not HP).

I know that the resonator/water catch is removed.

What counts is how much your TB, tube, MAF, air box and filter improvements actually boost the plenum pressure at WOT.

It is reallly really difficult to increase the WOT plenum pressure above 14.0 psi [387 inches of water] with a 14.7 psi [101.3kPa, 406.9 " H2O] ambient.

Just like all after market parts you CANNOT SUM the individual gains.

I think every thinks I'm looking for amazing HP gains, I'm just looking to reduce unnecessary drag and twist/turns in the intake.

You are over complicating the entire setup... OEM's don't even fully understand intake design. There is tons of testing done to find a happy medium that is cost effective and easy to put on the car.

Point is, you can think about it and theorize until you are blue in the face and you will still be where you started. When the entire process is very complex, as in this case, engineers resort to testing. You start with possibilities, narrow it down to what looks logical, and start testing. Whatever works the best might stick, or you might try to tweak it.

So if you want an answer to your question... no one knows. Go spend a bunch of money on a whim and see what happens. I personally think it's pointless and illogical.

Keep it simple...

I just have two other carbon fiber projects and a grounding kit before this one. Plus my wife wants to move 100 miles South and I need to find a new job.

My post here is for ideas.

What I've summed up:

A manometer will greatly assist in finding areas of high resistance, but will not guarantee higher flow into the plenum.

A +1" increase in intake diameter will more than likely complicate intake flow more than help it due to the smaller TB inlet.

Most people think Nissan/Infiniti spent a lot of time making each part efficient, which is so obviously false (intake, exhaust, interior material mass).

If you eliminate the resistance you will have higher mass flow. No matter how you cut it, greater deltaP = greater mass flow. It's far from supersonic or other odd areas of flow, so it's simplified.

Quote, originally posted by Sentientbydesign »

A +1" increase in intake diameter will more than likely complicate intake flow more than help it due to the smaller TB inlet.

BMW guys go from 3.0" to 3.5" intakes using ~65mm throttle bodies. They don't see anything in terms of actual gains. The gains are from the reduction of flow losses due to the slower average velocity and larger area in the MAF (they go to a 3.5" MAF). It's pretty pointless, especially when you can just address the OEM intake and get 90% of the gain for hundreds less.

Quote, originally posted by Sentientbydesign »

Most people think Nissan/Infiniti spent a lot of time making each part efficient, which is so obviously false (intake, exhaust, interior material mass).

They do, but the term efficient is derived from the complete picture. The G35 has the resonator box in the intake because they assumed that Infiniti owners want mouse quiet engines rather than loud intake resonance like the Z33 tube produces.

It's more cost effective for them to use the existing Z33 pipe, but they made a judgment call that you'd want something quiet. It appeases 80% of the owners, so it is actually efficient in design. It's just not suited to what you want.

Exhaust is a toss up between cost, weight, performance, noise, fitment, and note. It has to be a miracle solution to the market base, and cost effective for Nissan to boot.

Done.

The inefficiency in the intake extends beyond just the resonator. I'm well aware of why they put it there, but the piping itself is far from smooth with lots of seams that don't line up and weird indentations.

To me, it looks last minute/half assed, though I doubt that's anywhere close to the truth.

The one problem I have with the z-tube is the rubber flex pipe. I understand it's purpose since the engine and plenum will move slightly independent of the chassis, but that just adds turbulence and restriction to the whole setup.

My goal is to design smooth piping from the TB to the filter element, then build a custom scoop similar to the existing one, but a little smoother and larger.

If the process doesn't irritate the hell out of me, I might also test out a graduated intake that tapers to it's final minimum diameter at the TB.