In theory the required volume of air wouldn't change between intake setups, since the amount of air the engine breathes at a given RPM stays constant.

TK

 

I guess the type of air would. Cold vs Hot.

Do you know the effect of hot air compared to cold air on the engine?

Cold is better obviously but is there a huge difference?

 

Lol beats me. I think theres a general rule of thumb where so-and-so many degrees is equal to so-and-so horsepower, but I forget the actual values.

TK

 

you pretty much nailed it - it's been discussed before. nice to know we have another engineer of some sort out there.

 

The cAI question, Ive never taken the front end of my Z apart, but from looking up from under the car and down under the hood, I dont think a true CAI could be made that wouldnt involve so many pipe bends that it would become pointless. Im sure someone could figure out a way to get cold air, but to have it brought to the motor efficiently... i dont think so.

MIke

 

But would the more complex pipe restrict enough flow to not be able to feed the engine enough air? If a standard intake setup, flows more than enough air to feed the engine, a lesser flowing complex cold air intake, would still be beneficial, as long as its flow rate wasn't under the amount of air the engine needs. If it stayed above the theoretical figure for the max CFM the engine needs at redline, the cold air would be somewhat beneficial. Of course we're probably talking about less than 3-5hp, so in the end it really comes down to is it worth the hassle.

TK

 

HR

 

its not the maximum flow that really matter here, but more the restrictions at what the flow is. if the engine is pulling 200cfm, any filter will pose a restriction and any pipe as well. the stocker obviously poses very little restriction at what the engine pulls stock, so its a good idea to keep. the idea of a CAI will always have more bends in it, which usually will cause more restrictions. for the CAI to be effective it would need to have a lower amount of actual surface restriction than the stock tube in order to flow equally as well.

an accepted rule of thumb for cold air gains is 1% of the total HP per 10degrees cooler

 

While I follow your logic, those numbers don't sound right at all. I flowed a Ford SVO head a couple weeks ago and each intake port was flowing ~360cfm, and each exhaust port was flowing ~270cfm. Granted it is a different engine, but there is not way half of our engine flows less than is required by one cylinder of the Ford.

FWIW, I also flowed a K&N filter for laughs & giggles. The flowbench couldn't even flow it. It maxed out at 1600cfm.

Note: The CFM numbers were all flowed at the industry standard 28 inches of water.

 

flowbench numbers dont really relate to this. a head is more about how much you can get through the port in as fast as possible and this calculation is how much air the engine is actually demanding

 

flowbench numbers dont really relate to this. a head is more about how much you can get through the port in as fast as possible and this calculation is how much air the engine is actually demanding

 

Actually it does relate. For example, if a head can flow 300cfm per port and the engine makes 400hp, then you port the head and it flows 350cfm while sustaining the same velocity and the engine makes 450hp, what does that tell you? It tells you the engine is demanding more air. Theoretical numbers are all well and good to get a baseline of where to try and start, or a direction to try and take, but they don't always work out in real life like they do on paper.

Also, something not taken into account in all these equations is velocity. CFM is backup singer to velocity when making power. If you gain cfm but lose velocity, the engine will make less power, guaranteed. This can, to some extent be compensated for by piston speed (rpm). A slight loss in velocity can be overcome by revving the engine higher and will potentially make more power if the mechanics are suitable.

One last note, the dynamics of a running engine are very different than that of static numbers. The HR has a 10.6:1 compression ratio I believe. Do you think that is actually what the compression ratio is while it's running? No. That is merely the static fill capacity comparison of volume at BDC:TDC. If you run 100% VE throughout the entire powerband then that would be true, but you don't. There are too many factors to take into consideration to mathmatically determine why an intake allegedly doesn't make power.

I also stand behind the argument that the dyno is not the proper testing ground for an intake. The track will show much more accurate results. It actually tests the intake while the car is moving.

Anyway, just my observations. Take them for what you will.

*Edit* BTW, if you want to make power on any 4-stroke engine, everything is "about how much you can get through the port in as fast as possible".

 

Volumetric efficiency isn't static across all RPM ranges, porting a head increases VE, over a specific range.

TK

 

no matter how you put it, a head is very different from an intake. you cant just add the flow rates at the head together and expect that to be the engines flow rate. the head need to flow more than what the engine demands because it isnt making a constant flow like the intake does. flow bench testing basically takes the absolute most that a head flows, but as the valves open and close, it only sees that actualy flow rate for an extremely small amount of time and sees most of the time while part open, which obviously flows much less than with max lift.

 

I'm no engineer, but I do understand airflow. Explain how they differ.

 

An intake is not going to flow an absolute volume and speed at all times either. Every engine has reversion. Pulses of air that hit the valve and bounce back into the plenum, some past the throttle plate and into the intake. The better the engine the less of a problem this is, but it does exist. This is going to cause a disruption in flow in the intake tract as well. Granted, this is not a great a variance as the flow of the head.

The head does not need to flow more than what the engine needs. It needs to flow exactly what the engine needs. If it flows more than the engine needs, it's going to lose velocity, thus be less efficient and make less power. Simple as that.

 

I'm just learning myself, so someone with more technical knowledge of it could probably offer a better explanation. The reasoning is beyond my knowledge, and I'm trying to wrap my head around it, I just know its different.

TK

 

I'm going to talk to Technosquare (hopefully tomorrow) and I'm going to see if they can do a flowbench test on one of the intakes.

 

Your logic and comparison is flawed because you stated yourself that the head was tested at 28 psi. Specifying flow numbers in cfm are meaningless without also specifying the pressure (and temperature for that matter). In this thread, since we are talking about a NA engine, we are dealing with atmospheric pressure and vacuum from evacuation of gases from the cylinder chamber. This is nowhere near 28 psi. You put 28 psi across an intake and you'll flow much more than that head, I guarantee you!

 

Fair enough. I just know what I've personally seen and done. I flowed head, dynoed cars and engines that did things that they never should have done on paper. I'm just trying to correlate that to your theory.