the other day, i met with one of the members from this board to check out his Z tube and Pop charger. well it all looks good and all but it raised a few questions.

--What is the diameter on the Z tube?
--Those who using a POP charger.. why is the MASS AIR FLOW sensor pipe porting is smaller then the Z tube. To me it seems like it bottle necks a bit at the mass flow sensor.

ANyone know if we can use 350Z sensor tube portion since i think it might be same diameter as the Z tube?

2003 G35C -soon to be moded-
2001 BB6 -moded-

TRACK TIME ... THERE IS NO SUBSTITUTE!

 

Typical Nissan MAF have a 7-8" water column restriction at the highest flow rate. This 7/27.7=~~1/4 of a psi, 6.8%/4= 1.7% less external air pressure on the other side of MAF.

The heads and valve diameter [lift curtain area] are always the bottleneck respresenting 3-4 times more restriction than the MAF.

WOT restriction [amount of air pressure drop from atmosphere to cylinder [for filling calculations] is usually a total of 25-28" WC or roughly a single psi for the entire intake system. Instead of 14.7 psi [whatever barometer reads] the cylinder sees 13.7 psi at WOT near readline.
At the torque peak rpm the pressure drop is roughly 1/4 psi or 14.45 psi vs 14.7 psi.

The pressure drop is so small relatively, that improvements are hard to accomplish.........why you gain so little from intake mods.

Having a larger than necessary diameter in things - SLOWS the air flow down.......creating problems in filling at low rpms, affect low rpm torque production.

MAF accuracy [measuring grams per second flow] is critical to maintain an optimum fuel economy and driveability.

http://www.allfordmustangs.com/techa...tion_sheet.doc

As seen above the typical restriction is 7" WC at redline and the accurracy is within 3-4% at all flows........kind of a standard specification for MAFs.

If the air flow is halved the restriction drops by 3/4!

 

well i understand about thing being too big or too small. But if you look at the Z tube like i said its much larger then the MAF sensor tube.

To me at least if you gonna put a larger tube like the Z might as well get everything the same size, otherwise its not really worth it.
You can velocity stack it... put a smaller one right before the TB but not the other way around.

2003 G35C -soon to be moded-
2001 BB6 -moded-

TRACK TIME ... THERE IS NO SUBSTITUTE!

 

The Z-tubes outside diameter (sorry I'm not popping it off the car to measure inside diameter) is 82mm or 3 3/16"

The MAF housing's outside diameter is 76.3mm or 3"

The diameter of K&N's upper intake tube on any of their CAI's is 76.3.

I find this post interesting because I purposely did not use the upper tube that came with my 350Z K&N typhon intake. I created a way to use a Z-tube instead. I wanted to avoid heat soak from the metal tube (lord know's the system has a huge metal box housing the filter inside) at lower air volumes. And I felt that the larger Z-tube diameter was a plus. Now, thinking about intake air volocity factor's, maybe I should just wrap the metal tube and use it. No corrugated section too, hmmm.

"All that's necessary for the forces of evil to win in the world is for enough good men to do nothing.”
Edmund Burke

G35 6mt

 

this is the main reason why this thread was started. Because a lot of people ... think ... HMMmmmm let me buy an intake... but nobody really knows anything about them. They just go by what someone else did, and dont even know what they are doing on their own. People just automatically think intake=HP but its not always true. some will take away some will give. Especially when diameter on tubes is different.

its beneficial if you have velocity stack to an extent... but never the other way around.

2003 G35C -soon to be moded-
2001 BB6 -moded-

TRACK TIME ... THERE IS NO SUBSTITUTE!

 

Understand that the volume of the engine cylinders is fixed.

214/6=35.66 cubic inches EACH
Under the best of conditions that is ALL the air that can flow into a cylinder. By definition the torque peak rpm is the point of absolute flow efficiency. At WOT and this rpm, more air is flowing into cylinder than at any other rpm.
ABOVE this rpm [4600] the air flow declines at roughly a linear rate, due to the build up of frictional resistance to the air flow and the effects of the cam duration.
The intake valves are open [duration] say 240 degrees. That 240 degrees is longer than the 180 degrees for the piston to move from top to bottom because air takes some time to start flowing [getting up to speed] and once flowing [interia] it can still flow even though the piston is starting to move back up the bore.
You can think of this as a very mild supercharging. But because of the slow start and everything else the cylinder still doesn't get more than 34-36 cubic inches of air at best before the intake valve has to close to keep the upward motion from starting to squeeze air out.

Everything is a FINE LINE between too small [and too much time] and too large a diameter [and too little time] to get the most air at each rpm.

Unfortunately on a street engine which must idle at a low rpm to conserve fuel, cruise at a low rpm to conserve fuel yet still make enough power to pull a tiny hill with AC on and not lugg or need a down shift, and provide power at high rpms, EVERYTHING is a compromise!

The HP part is easy for engineers, it's the smooth idle and good fuel mileage at less than WOT during transistions that is difficult.

Anyway a tiny step up in size slows the air flow speed down and a tiny step down speeds the air up.....over a narrow range the weight of the flow stays the same [self compensating].
Smooth tapers and large radius cuves bends are better but it depends on packaging constants.

What is important is to break eack component down and measure its individual restriction, then bolt everything up together and see how [IF] the restrictions are algebriacally additive.

Easy to measure the restrictions as you have a built in flow bench the engine.
A manometer is an ultra sensitive barometer with a port to connect a air hose and the other side exposed to air pressure in real time........so the manometer reads the drop in air pressure at the hose. Barometers read in inches of mercury [29.92" HG], Manometer can be calkibrated in inches of water, a much finer resolution. 29.92" HG= 14.7 psi= 407" of water column.
I use 3 manometer zero> 3", zero > 20", and a rugged zero > 30" [this unit is robust enough to connect to plenum and survive the idle vacuum of [20" HG= ~~ 275" of water column].

When you measure the plenum vacuum the WOT goes to almost zero, then progressively rises as the air flow restrictions increase as the rpm increases.

We know that the Internation standard for measuring engine air flow restriction is 28" of water column. What is used on SAE flow benches to measure CFM flow of engine heads.

So I can see what all the restrictions add up to prior to the measurement point at what ever rpm I measure the restriction.

The MAF tells me CFM [in grams per second] flowing into engine and the Manometer tells me what the restriction of the flow is.
If you want to convert from one flow restriction to another you take the square root of the the ratio. for example.
Say the mods decrease restriction from 28" to 27" [28/27=1.037 square root is 1.01835 so in theory the air flow has increased by 1.835% and the ability to make power has increased by that amount beacuse the BMEP has increased by that amount.

We cannot measure inside the cylinders with engine running [why they take heads off and put them and the entire intake on a flowbench]. By measuring at the plenum we are halving the problem. Sure we cannot see what an individual cylinder is flowing but we see an AVERAGE of all the cylinders.
Any changes prior to the plenum will be reflected on the manometer. The only errors are how do the two restrictions add [everything after the plenum with everything before the plenum]...........for simplicity sake we assume they just add equally......[and that is essentially true].

The point is it is easy to measure restrictions and what if anything mods do in the way of reducing air flow restrictions.
This method is as least as accurate [really more accurate] than a chassis dyno becauase it is auto calibrating.......NO FUDGE FACTORS NO OPERATOR ERROR no need to correct for temperature variations nor barometric flucuations.

Assuming your Manometer is within its 1% of full scale specified accuracy [30"WC= 0.3" WC........why I have a 20" WC to narrow the number down to 0.2" WC measuring a 17" plenum restriction at WOT and 6600 rpms.

If I measure air filter restriction I use a zero to 3" WC manometer giving me a resolution of 0.03" WC].

After market manufacturers try to confuse buyers into thinking their products are better than they really are, hoping they won't understand how to test them accurately.

The farther away from the heads[valves] a product is the less affect it has on the total restriction.......60% of the restriction is after the throttle body, so you only have 40% to play with and to improve. So far the TB and MAF are off limits and they represent 27-30% of the remainder..........leaving just 8-10% for the hoses, air filter [1-1.5%], and air filter box.

 

Oh I agree, 99% of what is said about this intake and that intake, all intakes for that matter is opinion.

1. What are the temp readings at the MAF against ambiant, taken at 60mph and after 20 minutes of stop and go? 2. Does it pressurerise at speed just like the oem system does? 3. How does said intake factually change the power band if at all, as shown in a dyno comparison? Which as we all have to admit, has never been done. Until you get all the above answered, opinion's and lip service is all that you will have, nothing will be settled except who is the best talker.

I created a system that addresses what I saw as limited oem short comings. 1.Air inlets are not high presure, grill and hood lip are in the way, so I pressurerise from a high pressure zone 100% unobstructed. 2. Filtration ( I've read what's been said debatable add nazism) But it's been in the back of my mind, is the Z-tube the way to go, less heat soak, but 3/16" fatter then the MAF or do I run the metal upper tube that is the same diameter as the MAF and figure out how to avoid heat soak, that is my dilemma.

"All that's necessary for the forces of evil to win in the world is for enough good men to do nothing.”
Edmund Burke

G35 6mt

 

"1.Air inlets are not high presure, grill and hood lip are in the way, so I pressurerise from a high pressure zone 100% unobstructed. "
Please provide wind tunnel or other data proving that the oem is not at a high [HIGHEST] pressure point. What does unobstructed view have to do with pressure points.

Again a simple test with a manometer which can be reversed to measure tiny increments of pressure 1" WC= 0.0361 psi.

I'll give you an example: The obsolete 90-96 Q45 has a convoluted sound surpressing intake system. The air inlet was 2 feet of varing sized plastic piping from the air box, thru an oval hole in metal to a well hidden point in front of radiator/condenser flareing out to a trumpet shape..........at 90 mph the gosh awful looking contraption created a positive boost of almost 0.2 psi in front of air filter panel.

http://www.sw.nec.co.jp/hpc/sx-e/sx-...8/example.html

 

Oh hey, my bad, the grill isn't part of the intake flow path, but it does limit the size of the opening to the intake to just 1/3" tall The opening below the grill is 1 5/8" tall and does not have any rises or lips in it's path. One can catch more air down their then is possible on the oem system.


Now since you'd like me to provide wind tunnel data, how about you doing same for the below comment, SAE data, not ASE.

"The G35 comes already equipt with a CAI whose inlet is mounted at the highest pressure point.......the oem filter is fully exposed to the air pressure and viewable."





"All that's necessary for the forces of evil to win in the world is for enough good men to do nothing.”
Edmund Burke

G35 6mt