Hey all, I have tried searching for this topic but haven't had any luck. My question is simply this. I have an 08 Nismo Z, btw, so it has the dual intakes. Really, how do aftermarket intakes lose horsepower?? Like, I can't see how that its possible, when all we are really doing is changing the type of tubing we have and adding a higher-flow filter. I have the fujita intakes, and I didn't want to spend 500 bucks for a intake system, or pay too cheaply for one. For the price, it seemed great. Lose power? Um, I can't say I have. Sounds better? Yes alot. Slower...most likely not? But thats besides the point...how do other intakes lose power...youd think the stock one is so restrictive cause the surface area around the filters are so closed off, that I don't understand how other intakes don't perform as well. I'm not ranting at all, I am just trying to get a clearer insight on this because I constantly see people bickering about these threads about "how they lost sooo much rwph or how they gained horsepower". Really, please help me out. Thanks!

 

Biggest souce of power loss usually is drawing in warmer air. The factory setup is perfectly fine unless you are moving a LOT more air than a stock motor can. It is a good cold-air design, has plenty of filter area for minimal restriction, and is in general just a good system. Even if you don't lose power, there isn't that much power to be gained improving on an already good system.

 

^Italianjoe1 summed it up perfectly.

 

I can think of several reason why an intake can cost you power:

1. Poorly located entry point. You're sucking hot air vs. cold air. Hot air is thinner than cold air which means less oxygen which means less fuel added for every injector cycle which means less power.

2. Incorrect MAF sensor placement. MAF needs consistent, laminar flow of air past the electrode in order to produce accurate readings. Poorly placed sensor will produce erratic readings which will lead to poor fueling which will cost you power.

3. Poorly sized intake tubing. MAF sensor reading lets the ECU determine amount of air drawn in, which dictates fueling. A constant used in those calculations is the size of the intake tube. If you significantly change the size, you alter the outcome of the calculation which will lead to inaccurate fueling that forces the ECU into corrective more based on the O2 sensor feedback, in closed loop. Not exactly optimal. The ECU should be able to correct to some extent over time but it's not optimal.

4. Poor resonance. By altering the geometry of an intake, you change the resonance frequencies that the car was tuned to by the engineers that designed the system. Resonance is very important when trying to optimize the flow. Poor resonance frequencies will cost you power vs. an intake that resonates optimally with the intake valves.

I think most people underestimate just how much design goes into intakes on a car like 350Z. There's a lot more to intakes than just swapping a filter, slapping a shiny tube in to make it look good.

 

3. As long as the diameter at the MAF location is identical to OEM, this isn't really an issue. What could cause a problem is the change in flow characteristic if it tapers down just before this point and then diverges again. Aside from a potential flow disruption at or around the MAF sensor, it measures the mass of air, so further downstream if the pipe enlarged, it's still the same mass of air metered. The main issue with piping diameter changes is flow velocity. Larger will flow more, at the cost of flow velocity. Small diameter and large diameter both serve purposes, one just might be out of the rev range of an OEM VQ.

4. It just shifts the resonance frequency to a different RPM, which may or may not be in the powerband.

TK

 

Difficult to support a false premise.

 

Agreed. I assumed that the diameter remains constant throughout the pipe. If a design decides to taper down or up the diameter at any point, that may or may not have adverse effects.

Yes, the resonance is really the optimal range shift and how it relates to practical driving situations most will experience. If an intake has an optimal frequency at 6200 RPMS, I'd say that's probably not optimal.

Glad someone else is taking this intake stuff seriously. Thanks for throwing in more details

 

Thanks for the VERY mature responses..makes me happier. Thanks to everyone! This thread wasnt written as a rant, disclaimer, or a biased-statement. I just wanted further understanding from the more experiences people out there. But thanks again for the responses. Im very happy wth my intake system, it sounds great, looks great, and I know based on my butt dyno, that the power is STILL there. Have a safe memorial day weekend.

Mike

 

Even if the Fujita brand intakes are sacrificing low-mid range power in exchange for peak numbers, it's really hard to prove beyond a doubt on a dyno, unless you put the dyno in a wind tunnel. When standing still without airflow, intakes that place the filter ahead of the radiator might be drawing in air that is significantly cooler than inside the engine bay. Once the car is moving the gap in temperature differences might become pretty small.

TK

 

Even on a dyno, if there is a fan set up in front of the car like there should be, you will get pretty good airflow to the nose. I know it's splitting hairs to try and figure it out without an actual test, but i'd say well run dyno testing should be fairly accurate. The fact that none of the HR guys have gained any power with the short intakes, versus a general gain (however slight it may be) with the long tube Injens, tells me that there must be some superiority in thier function, whether it's the length, filter placement, tubing size, filters themselves or whatever, those intakes usually gain power in the upper rpms.

 

Aftermarket also used stainless steel pipe, while OEM used hard plastic. It is easier for stainless steel to soak up the heat from engine bay and retains heat longer compared to OEM plastic pipe. Try driving for 30 min or 1 hr in a hot summer day, pop the hood and touch your intake pipe, stainless steel intake pipe will be really hot to touch while OEM one is much cooler.

 

Most aftermarket ones are aluminum for cost reasons, not stainless. It has the advantage of being lighter and slightly less heat soak prone, but no metal pipe will resist heat soak as much as the OEM plastic tubes. Thats one reason why K&N offers some applications with a metal or plastic tube. Sometimes the plastic one is acutally rated with a slightly higher HP gain.

Also, most of the heat that the pipes absorb stays in the pipe material itself, just because the pipe is warm doesn't mean it heats the air up that hot.

 

So if i would tune my car with the intake it will obviously gain power!

Not just as much MAYBE as the Injens do at high RPM's!!

RIght?

 

Aluminum, that's what I meant sorry. Are you sure that the heat only stay in the material itself? It doesn't makes sense to me - the air will have some sort of contact to the pipe when it travels. Even though it's quite a quick contact, but if the pipe is hot then it should increase the temp of the air that contain inside. I think it's just a simple logic

 

Last weekend I installed a Nismo dual intake on my '07 Touring 6 speed. From a stop the low end power seems much better than with my stock intake, and the sound on WOT is great. I think the MPG has gone up at least sone, but I'll have to wait for a long trip to determine that. I'm happy with my intake. BTW the heat shields long like they should work pretty good the way they're made and placed in the compartment.

 

might want to get your butt recalibrated

 

Thanks for the suggestion. Next time I pass a Butt Recalibration Shop Ill be sure to stop in.

 

Great info

Posted this up the other day https://my350z.com/forum/tuning/435792-help-needed.html just wondering if running my typhoon with no airbox could be giving me some heat issues... Also running with the chrome K+N pipe... think it may be time to heat wrap the airbox and heat wrap the tube and refit based on the above info... Or try and get me an 06 airbox and give that a go.. Any advice would be appriciated!