Intake Question

[MANIACura]

I have no idea what performance gains (if any) you can get with aftermarket filters versus stock filters but I can personally tell you one thing to watch out for. When I bought my 91 NSX it always had a searching idle 500-900 rpm. Never stalled just fluxed. Checked the air filter.....it was the flat aftermarket K&N in the stock box. Looked OK. I sent my injectors to RC engineering, changed fuel filter, all seals in fuel system, changed all three rear bank coils, yada....yada. No change. Decided to disassemble the intake/throttle body. Holy Sh*t. The entire inside of the throttle body was coated with black oily muck most probably from the previous owner over oiling the filter.

Point being - in order to get good filtration from a foam filter you have to oil the filter and its really easy to overdue and negate any advantage of air flow you may get. Also, as in my case, the excess oil was sucked into the intake causing the sensors in the throttle body to not be able to function correctly. If you don't oil correctly/enough....dust gets through. Once I cleaned and reassembled the TB the car idles smooth as baby's bottom. Stock filter is back in.

 

[jond]

How does the OEM filter fit on an aftermarket intake?

The aftermarket intake(Cantrell Concepts) uses the OEM filter box. AKA, the filters are the same size.

Holy Sh*t. The entire inside of the throttle body was coated with black oily muck most probably from the previous owner over oiling the filter.

I noticed the inside of the filter box was oily when I took my aftermarket filter out. I drive in rain, so I figured that couldn't be good for water to hit the oil filter which is only a few inches from the TB.

 

[comtec]

I like mine and i haven't had any problems. I was running the Downforce AIS with UNI for about 10 months and now i have a WeaponR Secret Weapon semi connected to the Downforce AIS.

The intake growl is considerably louder than with the AIS and UNI . Also the annoying high pitched hissing sound i had with the AIS and UNI isn't really noticable. Not sure what the sound was but it sounded like a blow off valve when shifting.

 

[4AU4LIFE]

^^^^^^^^^^^^^
IMO, even though you are running the a/m side scoop and Weapon R intake, it isn't sealed off from the rest of the engine compartment. Therefore, I wouldn't think you would get any benefit at all from using the side scoop since the amount of cold air coming into it will be cancelled out almost completely by the hot engine compartment air.

 

[comtec]

^^^^^^^^^^^^^
IMO, even though you are running the a/m side scoop and Weapon R intake, it isn't sealed off from the rest of the engine compartment. Therefore, I wouldn't think you would get any benefit at all from using the side scoop since the amount of cold air coming into it will be cancelled out almost completely by the hot engine compartment air.

Yea i know. The AIS was already on the car so i just mated the end of the WR to it. I am sure it doesn't use the AIS to it's potential but with the amount of sound (air sucking sound and growl) heard from outside the AIS I'm sure it uses it to some extent.

A super tuned FI car maxed for HP might see around a 1% or so drop in power from increased intake air temps but in a stock engine like mine it is probably negligible.

 

[NSXGMS]

The aftermarket intake(Cantrell Concepts) uses the OEM filter box. AKA, the filters are the same size.

That would be an aftermarket intake scoop. The intake itself (airbox assy.) is still stock.

A super tuned FI car maxed for HP might see around a 1% or so drop in power from increased intake air temps but in a stock engine like mine it is probably negligible.

It seems all these AM intakes do is hurt performance if anything. And it seems there is so much resistance to accepting the concept that the OEM intake/filter cannot practically be improved upon.

It's unfortunate that so many people have been propagandized into believing these mods work on an NSX and many thousands of hard-earned dollars are spent on them every year. :frown:

 

[comtec]

That would be an aftermarket intake scoop. The intake itself (airbox assy.) is still stock.



It seems all these AM intakes do is hurt performance if anything. And it seems there is so much resistance to accepting the concept that the OEM intake/filter cannot practically be improved upon.

It's unfortunate that so many people have been propagandized into believing these mods work on an NSX and many thousands of hard-earned dollars are spent on them every year. :frown:

But i didn't expect a power gain so don't think i was propagandized. My reasons were purely cosmetic and acoustic :wink: .

 

[prestonmay]

That would be an aftermarket intake scoop. The intake itself (airbox assy.) is still stock.



It seems all these AM intakes do is hurt performance if anything. And it seems there is so much resistance to accepting the concept that the OEM intake/filter cannot practically be improved upon.

It's unfortunate that so many people have been propagandized into believing these mods work on an NSX and many thousands of hard-earned dollars are spent on them every year. :frown:

So even a K and N filter in the Oem BOX is a waste? If you buy thinking you will get 1 -6hp increase? I have ctsc and wanted to change the UNI filter with the K and N ---- more for its easier to clean...I do not want a decrease in performance....thats for sure.....................I bought Weapon R----And sold it 3 months later.

 

[NSXGMS]

So even a K and N filter in the Oem BOX is a waste? If you buy thinking you will get 1 -6hp increase? I have ctsc and wanted to change the UNI filter with the K and N ---- more for its easier to clean...I do not want a decrease in performance....thats for sure.....................I bought Weapon R----And sold it 3 months later.

The stock NSX intake system is efficient enough to provide the engine with more air than it can handle (on a naturally aspirated NSX). IOW, it doesn't matter if the OEM inlet snorkel is small because much more air flows through the filter than the engine can use. Sure, some filters flow better but again, it doesn't matter with the NSX as more air enters the throttle body than the engine can use. As it flows from the TB through the intake manifold and into the combustion chamber there is still more air than the engine can use. That's why the big-bore throttle body and intake manifold mods are not recommended for non-forced induction applications. More air already reaches the combustion chamber than can be used. Why make the doorway bigger if all the people can already walk through it at the same time?

So, the answer is that bottlenecks do occur during the NSX air intake process however there is still more than enough air left over at the end for the engine to use and then some. If one were to introduce FI causing air needs to increase then yes, the OEM filter, throttle body and intake manifold might steal enough air to create a deficiency in the combustion chamber. But a stock NSX intake produces a surplus of air for combustion.

Using bogus numbers if the stock NA motor's maximum efficiency is combusting 5L of air every 1 second the stock intake is providing 7 L/1 sec to the combustion chamber--more than enough. Let's assume 12L/1 sec of air enter the intake at speed.

Now, you go FI and the engine wants 10L of air/1 second. Well, the stock intake is stealing 5L/1 sec (12L-5L = 7L). Now if we use a high-flow filter, bore out the TB and IM we free up 3L/1 sec that were being stolen in the stock intake and can now get 10L/1 sec to the combustion chamber when 12L enter the intake through the snorkel.

But what you don't need is 10L/1 sec on a stock NSX. The engine can only use 7L/1 sec. Pumping 10L in does no good. It just dissipates uncombusted.

 

[contactace8]

So over all these aftermarket intake/filters are useless on a stock motor. THE END

 

[NSXGMS]

So over all these aftermarket intake/filters are useless on a stock motor. THE END

Yes.

 

[Mr.OB*GYN_Rhett]

Ive read what you have all said but has anybody tested a BPI velocity stack on an nsx?
very knowledgeable posts btw NSXGMS

 

[NSXGMS]

Ive read what you have all said but has anybody tested a BPI velocity stack on an nsx?
very knowledgeable posts btw NSXGMS

Yes, but not exactly "tested"

Again, you can stuff as much air as you want into the engine but it won't use any more than it already does.

 

[Tanto2]

On a NA car with a less restrictive exhaust, the engine will be trying to flow more cfm at high RPM, so a less restrictive intake will result in an HP gain, not rocket science. Has this been verified by owner dyno results? Yes it has, but there are several contradictory posts out there, however any racer or bullet biker out there knows this from the magazine dyno tests on stock vehicles, let along their own seat of the pants. The cache about the uni-filters is that they actually do filter quite well and still restrict less. Are they worth the slightly less filtration and oil mess? IMO it depends on if you drive in a very dusty environment as the paper filter does filter smaller particles. I have no problem with the uni, but I don't drive daily. The question for us NA folks is if the Mugen unit is an improvement over the comptech/fact box/uni. We need to dyno those two.

 

[NSXGMS]

On a NA car with a less restrictive exhaust, the engine will be trying to flow more cfm at high RPM, so a less restrictive intake will result in an HP gain, not rocket science. Has this been verified by owner dyno results? Yes it has, but there are several contradictory posts out there, however any racer or bullet biker out there knows this from the magazine dyno tests on stock vehicles, let along their own seat of the pants. The cache about the uni-filters is that they actually do filter quite well and still restrict less. Are they worth the slightly less filtration and oil mess? IMO it depends on if you drive in a very dusty environment as the paper filter does filter smaller particles. I have no problem with the uni, but I don't drive daily. The question for us NA folks is if the Mugen unit is an improvement over the comptech/fact box/uni. We need to dyno those two.

Intake and exhausts are two completely different systems operating in two completely different ways.

Yes, the stock NSX exhaust is restrictive. The engine can only combust what it can spit out. When the stock exhaust is removed the engine can move more waste consequently combusting more air--air that was already available and plentiful from the stock intake. It was always there but the engine couldn't use it. Even after installing less restrictive headers and exhausts there's still a surplus of air in the combustion chamber.

The fact is that a naturally aspirated stock internals NSX motor cannot use more air than is already provided by the stock intake system. Allowing more air to reach the combustion chamber by installing more efficient filters, scoops or boring out the throttle body or intake manifold is futile. The engine cannot burn it. You would need to increase the amount of fuel the engine could consume and the only way to achieve that is through forced induction or increase the displacement of the engine and use standalone engine management.

I am not in any way disagreeing with the notion that there are more efficient air filters than the stock filter. However flowing more air into the combustion chamber of a stock NSX does absolutely nothing. You could put the NSX in a sterile room and completely remove the intake assy. and you would have virtually zero hp gains. The stock intake system is providing more than enough air for the engine as it is.

And comparing the NSX to any other car or bike is apples & oranges. What works on 90% of other vehicles does not necessarily work on an NSX. The stock intake system of an NSX is designed better than almost every other car or bike intake ever made. Adding high-flow filters and boring out the throttle body might work on a Buick GNX but it won't work on an NSX. I have not seen a body of dynos showing consistent gains on a stock NSX with an aftermarket filter. One or two that were done under questionable conditions, yes, but not a body of dynos showing consistent, reliable gains like you'll see with headers and exhausts.

 

[KSXNSX]

. I drive in rain, so I figured that couldn't be good for water to hit the oil filter which is only a few inches from the TB.

Actually, oil and water don't mix so the water wouldn't have done anything to the oil.

 

[LJSB]

Adding high-flow filters and boring out the throttle body might work on a Buick GNX but it won't work on an NSX.

I agree.

 

[JZ TWINS]

I know for Supra's, the HKS mushroom filter is one of the worst because it doesnt filtrate dust and crap. That is why I havent put the Uni in. Looks the same. Sticking with oem.

 

[Tanto2]

Intake and exhausts are two completely different systems operating in two completely different ways.

Yes, the stock NSX exhaust is restrictive. The engine can only combust what it can spit out. When the stock exhaust is removed the engine can move more waste consequently combusting more air--air that was already available and plentiful from the stock intake. It was always there but the engine couldn't use it. Even after installing less restrictive headers and exhausts there's still a surplus of air in the combustion chamber.

The fact is that a naturally aspirated stock internals NSX motor cannot use more air than is already provided by the stock intake system. Allowing more air to reach the combustion chamber by installing more efficient filters, scoops or boring out the throttle body or intake manifold is futile. The engine cannot burn it. You would need to increase the amount of fuel the engine could consume and the only way to achieve that is through forced induction or increase the displacement of the engine and use standalone engine management.

I am not in any way disagreeing with the notion that there are more efficient air filters than the stock filter. However flowing more air into the combustion chamber of a stock NSX does absolutely nothing. You could put the NSX in a sterile room and completely remove the intake assy. and you would have virtually zero hp gains. The stock intake system is providing more than enough air for the engine as it is.

And comparing the NSX to any other car or bike is apples & oranges. What works on 90% of other vehicles does not necessarily work on an NSX. The stock intake system of an NSX is designed better than almost every other car or bike intake ever made. Adding high-flow filters and boring out the throttle body might work on a Buick GNX but it won't work on an NSX. I have not seen a body of dynos showing consistent gains on a stock NSX with an aftermarket filter. One or two that were done under questionable conditions, yes, but not a body of dynos showing consistent, reliable gains like you'll see with headers and exhausts.

I possibly incorrectly assumed anyone asking about an intake already has a freer exhaust. While I disagree with much of the above, without opening up the exhaust, an intake should not be considered. Technically at top rpm's there still will be be a very small increase in HP, but that will be offset by small low rpm torque losses. If a freer exhaust is in the mix (AS IT SHOULD BE if you want more HP), then reducing ANY pumping losses will free HP. And the fuel will be there to do this on a NA car. Owners have taken vaccuum readings on the intake and they were in line with your average perf car. Yes it was interesting that Honda tried to utilize an intake charge effect to smooth out a down blip I assume, but if you want HP and have to open up, it's meaningless.

 

[Larry Bastanza]

I had secret weapon r....

It showed gains when the car was not warm. After the car got warm, the hp numbers dropped. I put the OEM box back on and retro --- fitted the cone in the box and the but dyno felt some improvement and the Gtech said 6hp peak power increase....

It is very important to note that this is a CTSC setup. I would expect 0 gain for an NA NSX.

Regards,
LarryB

 

[NSXGMS]

I possibly incorrectly assumed anyone asking about an intake already has a freer exhaust. While I disagree with much of the above, without opening up the exhaust, an intake should not be considered. Technically at top rpm's there still will be be a very small increase in HP, but that will be offset by small low rpm torque losses. If a freer exhaust is in the mix (AS IT SHOULD BE if you want more HP), then reducing ANY pumping losses will free HP. And the fuel will be there to do this on a NA car. Owners have taken vaccuum readings on the intake and they were in line with your average perf car. Yes it was interesting that Honda tried to utilize an intake charge effect to smooth out a down blip I assume, but if you want HP and have to open up, it's meaningless.

I don't really understand your point.

As I said, assuming the maximum efficiency of the exhaust system there is still a surplus of air available to combust delivered by the stock intake. Fuel delivery has nothing to do with it. It's all about air. Fuel can't combust without air, obviously.

One could run an NSX with no exhuast and no intake and it would make no difference. The only way to burn more air than the stock intake supplies would be to introduce forced induction.

 

[greenberet]

However flowing more air into the combustion chamber of a stock NSX does absolutely nothing. You could put the NSX in a sterile room and completely remove the intake assy. and you would have virtually zero hp gains. The stock intake system is providing more than enough air for the engine as it is.

I don't fully agree. The intake system on an N/A car doesn't provide air to the cylinders like on a conveyor belt, rather the pistons suck air through the intake system. The lower the restriction, the more air will come through at a given level of suction. The engine computer will then add enough fuel so that the air/fuel ratio is around 14.7:1 (less at full throttle). None of the air that manages to get into the combustion chamber is unused and the more air you get in there, the more horsepower you can make.

How many horsepower an N/A car will gain from having a lower-restriction air filter depends on how much of a pressure loss you have if you measure before and after the stock air filter. The more air you are sucking through, the higher the pressure loss will be. At the flow rates an N/A engine is capable of achieving, maybe the stock filter does not yet cause a noticeable pressure drop. If that's the case, then a lower-restriction filter won't allow more air to get through and won't get you any additional horsepower.

That seems to be pretty much the case. In this thread, Science of Speed tested the horsepower difference between a stock air filter and a Uni foam filter in a 3.2 with a stock intake system but with headers and an aftermarket muffler. They came up with 4.4 hp gain. On a completely stock 3.0 you'll get less than that. The engine computer in my car was programmed while a Uni foam filter was in place. I asked Comptech if they thought I would have any problems if I switched back to the stock filter and they said no, it should hardly make any difference.

 

[NSXGMS]

I don't fully agree. The intake system on an N/A car doesn't provide air to the cylinders like on a conveyor belt, rather the pistons suck air through the intake system. The lower the restriction, the more air will come through at a given level of suction. The engine computer will then add enough fuel so that the air/fuel ratio is around 14.7:1 (less at full throttle). None of the air that manages to get into the combustion chamber is unused and the more air you get in there, the more horsepower you can make.

How many horsepower an N/A car will gain from having a lower-restriction air filter depends on how much of a pressure loss you have if you measure before and after the stock air filter. The more air you are sucking through, the higher the pressure loss will be. At the flow rates an N/A engine is capable of achieving, maybe the stock filter does not yet cause a noticeable pressure drop. If that's the case, then a lower-restriction filter won't allow more air to get through and won't get you any additional horsepower.

That seems to be pretty much the case. In this thread, Science of Speed tested the horsepower difference between a stock air filter and a Uni foam filter in a 3.2 with a stock intake system but with headers and an aftermarket muffler. They came up with 4.4 hp gain. On a completely stock 3.0 you'll get less than that. The engine computer in my car was programmed while a Uni foam filter was in place. I asked Comptech if they thought I would have any problems if I switched back to the stock filter and they said no, it should hardly make any difference.

You are correct that any air that got into the combustion chamber would not dissipate uncombusted as I suggested. But my point was that the stock intake system is so unrestrictive that the amount of air that would be available for the engine with no intake at all is not much more than the amount of air available with the intake.

The combination of high-flow filters, bigger scoops, bored out throttle bodies and intake manifolds still don't yield significant gains even though they ostensibly create a less restrictive system. The amount of air the pistons will suck is still limited by the amount of air that can flow into the head. That's the final bottleneck. Clearly the amount of air stolen by the intake system is so small that it's very nearly providing all the air that can possibly be sucked through the head with normal aspiration.