OK, in other posts it has been mentioned that K&N filters claim that their cold air intake kit adds 15% (or 43hp) to a stock 350Z. I doubt that (a lot). I say horsepower is harder-earned than that.

Anybody want to discuss this?

Frank

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1970 240Z

you are not gaining but unlocking horsepower you already have. IMO. the stock air intake setup is very restrictive. switching to tubing that is mandrel bent and with no kinks the air can flow much easier. and most true setups relocate the filter outside the hot engine bay. so sucking in more cold air and much faster do to less restriction could definitely increase hp and help with throttle response. air is reaching the throttle body much faster and at a larger volume. that is how i see it.

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Mike Tubiak
1978 Datsun 280Z - HLS30-438694

EXACTLY.

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John Taddonio
1970 240Z
1977 530Z
1984 300ZXT
zcarnut@hotmail.com
FB: Zccr zcarclubofrochester

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Mike Tubiak
1978 Datsun 280Z - HLS30-438694

Yup. I undrstnd how cold air systems work, and I have no contest that they HELP an engine breathe better.

An engine is nothing more than an "air pump", plain and simple. The capacity of the engine (cubic inches of displacement) determines how much air it can intake/exhaust per revolution. There's seldom a problem getting enough FUEL to an engine (we could devise a mechanical pump which could deliver 5gal of fuel/second if we wanted to). Getting enough AIR into/out of an engine for better combustion is the actual challenge.

So yes, I agree that by sticking the intake out into the 'cold' air (relative term), you make slightly denser air available to the intake, which thereby increases the number/volume of oxygen molecules available for combustion. A supercharger, turbocharger, or Ram Air system serves the same purpose, by accelerating the airflow rate (Turbo or Ram) or compressing the air/fuel mixture entering the combustion chambers (supercharger).

But at the factory, the new engines are tested on Dyno stands, without any accessories or air intakes attached. That gives the engine's true power (Brake Horse Power) at the flywheel before anything is attached to the engine which uses some of that horsepower (belts, pulleys, alternator, fan, air cleaners, exhaust, P/S, A/C, driveline, etc).

Whatever the BHP reading is, that's the MOST POWER you're gonna get from that engine, without modifying it. And that's the horsepower rating you see printed in the sales data. When you attach accessories to the engine, you use little bits of that BHP. The driveline itself takes up a LOT of BHP, so that by the time you measure the Dyno horsepower at the drive wheels, you've lost a lot.

So let's say a certain new engine tests at 300 brake horse power on the factory Dyno stand. That 300BHP figure is posted on the sales data. When you put the engine into the car and add all the accessories (and the driveline), you might get about 250 hp at the rear wheels (estimate for discussion purposes).

OK, you're not happy with that figure, so you buy a K&N cold air intake unit which promises "15% hp increase" and stick it on your car. You are computing from the posted 300bhp figure, expecting a 45 hp increase. That's not gonna happen.

What might happen is a VERY SLIGHT incremental increase toward the original 300bhp the engine is capable of under ideal conditions. If your 300bhp engine measured 250 rwhp on the Dyno, that 50hp loss is attributable to everything you have placed on the engine (including the driveline) once it was removed from the test stand and placed into the car. SO THE COLD AIR SYSTEM CAN ONLY RESTORE THE AMOUNT OF HORSEPOWER THE STOCK AIR INTAKE SYSTEM TOOK AWAY IN THE FIRST PLACE. Even if the restrictive stock air intake system accounted for 15% of that lost 50hp, you might (might) restore about 7 hp with your cold air kit, IF it was completely restriction-free and you installed it correctly.

You're simply not going to ADD 40+ hp to your car by opening the intake system to the atmosphere. You can't create energy.

We had a great Dyno day recently. Some of the hottest-built 350Z cars on the street attended and got measured. One of my favorite "hot" 350Zs, with tons of expensive, professional work done to the engine, managed to produce an estimated 350bhp at the engine (less than 300 at the rear wheels). The owner probably has as much time/money/effort/research/blood/sweat/tears in his ENGINE as I have in my entire car. The car has everything you can name on the engine, including a fancy cold air intake system. It produced an estimated 350 hp at the flywheel, and a little less than 300 at the wheels.

Sorry ~ You're NOT gonna get 300hp from a stock 350Z engine simply by adding a cold air intake system.

F

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1970 240Z

i agree but still what i said rings true. his 350 pushes 287bhp. so ok maybe his numbers are more close to that now. it was probably 270 in the car and by adding the cold air intake it bumped it up closer to it's max stock hp. either way adding a cold air intake does add hp. if they didn't why would we buy them. if you make an engine breather better not only do you get more power but heck better gas mileage.

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Mike Tubiak
1978 Datsun 280Z - HLS30-438694

and technically now if more air is pushed in a simple chip could let the computer know this and increase the hp. i would imagine that the motors are dynoed at the factory using the same ecu that would be in the car. so by changing that you are unlocking the engines ability. i am sure that these engines are detuned at the factory to meet requirements.

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Mike Tubiak
1978 Datsun 280Z - HLS30-438694

I agree with your theory.
But the 350s we saw at Dyno Day had trick cams, big injectors, racing exhaust, fancy intakes, increased compression, tweaked timing, and still "only" approached 300hp at the wheels (about 350 at the engine).
There's no possible way a cold air intake alone can 'make' a 3.5L engine produce 100% of it's potential. You might (MIGHT) bump it back up by maybe 5-7hp.

A better way to say it might be: a cold air intake kit might GIVE BACK about 5 of the lost horsepower the stock intake robs from your engine.

Horsepower is expensive, and hard-earned. Each horse costs lots of cash. If a simple cold-air intake could give us 300hp, every kid on the block would have one.

F

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1970 240Z

They do Frank....

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Phil
1981 280zxt - Now in the care my son!
2014 370Z Sports Touring Roadster

More (better) arguments, please....?!

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1970 240Z

Phil is right they do. and a cold air intake will like i said unlock or put back lost hp. i am sure there are dyno numbers online somewhere before and after cold air intake. RDZ where are you?

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Mike Tubiak
1978 Datsun 280Z - HLS30-438694

I am talking CRANK HP. "At the wheels" will most definitely be significantly lower and takes into consideration all of those power robbing items that Frank mentions.

The 350Z ECU will correctly compensate for air/fuel mixture, including increase or decrease. For example, the car is recommended to run on premium fuel, but if I were to put in 87 octane regular, the computer will compensate and adjust timing/fuel mixture for optimum running, albeit with less power. No knocking or pinging because the computer recalculates the intake mixture. It will do the SAME for a cooler,denser, higher volume air intake with a device such as the K&N intake.

So while I do not think a 15% HP gain is accurate with a CAI, I do think that a 3-5% gain AT THE CRANK is true.

In any event, the car has MORE with a CAI than with the restrictive stock air box.

Frank, this is no longer a 240Z with finicky carbs and air pressure determining the air/fuel mixture and no ECU monitoring such at thousands of times per minute. All the more reason to be amazed that the 240Z produced the power that it did!

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John Taddonio
1970 240Z
1977 530Z
1984 300ZXT
zcarnut@hotmail.com
FB: Zccr zcarclubofrochester

exactly John. modern motors can do amazing things now with even as small of a thing as just upgrading the air box.

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Mike Tubiak
1978 Datsun 280Z - HLS30-438694

Oh, I hope Phil and Mike are responding to "every kid on the block would have one" with "they do" ~ NOT responding to "if a cold air intake could give us 300hp" with "they do".

"Crank" HORSEpower is what I'm calling Brake Horse Power, measured at the flywheel with a restrictive brake applied, measuring the engine's ability to overcome resistance. Abbreviated BHP.

And no way, guyz, no way. You ain't gonna get 300bhp out of any engine just by adding a cold air intake kit, unless the engine was already producing 295bhp before you started.

F

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1970 240Z

but that isn't the question you asked Frank. you wanted to know if adding the CAI increased hp. and it does. maybe not what they say it does but bottom line is you will gain/unlock/free up/regain/get back/go up/reinstate/give back/etc etc etc lost hp.

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Mike Tubiak
1978 Datsun 280Z - HLS30-438694