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Discussion Starter · #1 ·
I can summarize my oppinion of cold air intakes on a stock Versa motor as follows:

"The marginal gain at top end is not worth the complete loss of low end, period."

and

"Only when your engine CFM and volume demand exceeds what the stock intake can provide will an aftermarket/custom intake be essential to good performance and driveability, even then, the stock manifold with their thin runners will be a restriction long before the inlet/intake system becomes one"


Shoot off your oppinions. Butt dyno isn't accurate. I straight piped mine and it's still a slow POS, but the butt dyno says different.
 

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Looks like a pretty solid gain across the entire board. No loss at all with that intake according to that dyno.
 

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..... even then, the stock manifold with their thin runners will be a restriction long before the inlet/intake system becomes one"....
Sorry I beg to disagree... Generally speaking, it is highly unlikely that the intake manifold would be more restrictive than the inlet air/air cleaner assembly since the intake manifold is mainly optimized for performance. Typically the inlet/air cleaner assembly is compromised since it is the part that is designed/tuned for intake noise/NVH and to prevent any form of water ingestion.

I think this is the reason why almost all CAI products usually show a modest gain in HP and torque over the whole speed range, assuming you as a customer buy off on an increase in noise and an increased risk of water ingestion damage.

BTW, based on personal experience, on V6/V8 engines, unless you have an increase of approx 20 HP/20 lb-ft Torque, it is very difficult to notice the difference based on seat-of-pants feel. I don't have an opinion on small displacement engines since I do not have much experience on those. Most likely it would be proportional.
 

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Discussion Starter · #7 ·
Wanna put money on that? Look at how tiny those runners are, that intake runs out of steam pretty low comparatively.
 

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Wanna put money on that?....
Sure I'd like to, but unless you have access to actual (or computer simulated) performance data on your engine or at least CFD data on the whole intake system, it would be impossible to conclude who is right. In the case of airflow, you'll be surprised that at a certain point, bigger is not necessarily better. And this doesn't mean just on the intake side, but on the exhaust side as well.

Nowadays, with so much technology on modern IC engines, no accurate conclusions can be made by simply looking at the parts. I'm sure you've heard about the saying " In God we trust, everyone else bring data".
 

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Discussion Starter · #9 ·
The technology on modern engines is easy to understand, it's all simply tacked on to the fundamentals of 4 stroke passenger car engines, which have essentially remained unchanged forever, all it is is tacking on something that uses a physics principle or principles to either increase efficiency, reducing emissions of your unwanted substances while improving performance.

The intake still works the same, and matter of fact the MR motor was in a generation of engines that had IMO the best balance of technology use. Not too much to make diagnosis and understanding a nightmare. They don't even have variable intake runners, a principle that has been around forever. The EFI system is basically the same as any other EFI system before it, the valvetrain is a dead simple solid lifter setup, with a simple phaser on the intake cam for VVT, with associated inputs required for actuation, a simple and easily implemented concept.

I'll admit i don't have any primary data to suggest the intake is inadequate, but i do know for sure it's inadequate for operation in a higher RPM band, or leaves alot of HP on the table. If you can make an engine rev higher, you can get more HP out, no question. Honda 4 bangers are a perfect example of this. They build them and rev them to 9000.

The intake Dynatek made had a 15HP or so actual gain, and curve remained the same, the gains started at 3000RPM if i remember correctly.

Matter of fact, i may be able to rehash that little project. There is a place called Re Speed here in London that could make intakes for us, i'm talking to them. It would be the same as before though, you need a group of people who are going to buy it to make it worth their time, and make it more affordable. This should be easier now since they're older and the market for serious mods is bigger now that they're racking up the mileage. I will give them a plastic intake and see what they can do. Probably just a matter of enlarging the plenum, and runners (not too much for the latter).
 

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Sorry in advance for the length:

If the mani were so restrictive, as people seem to be suggesting (without data), then that would be the choke point. no change to the intake would make a lick of difference.

With equal length long runners that are already port matched from factory, you are left with a few options:
1. increase runner diameter which will necessitate port matching to net gains
2. increase plenum to increase the pool of air available for the runners to pull from (will also increase air velocity)
3. increase the amount of air available to the plenum (modified/cold air intake).

Drawbacks of CAI:
1. incoming air velocity decrease.
2. turbulence when using a short ram
3. lag when using a long ram.

balance is key. A modified intake WILL provide benefit WHEN the manifold is able to pull more air than the stock intake can supply.

If the manifold is so restrictive that it can't pull any more air than it is already pulling, you won't see any increase by adding a CAI. But, if the mani is efficient enough, AND the engine can evacuate the exhaust efficiently enough, then adding a CAI can increase the volume of air available to the mani., and by extension, the cylinder.

Adding ONLY a CAI AND seeing a gain is proof that the manifold is efficient enough that it can flow more than the stock intake can supply.

Adding an exhaust works the same way, by efficiently removing the exhaust gas, the engine can pull more air in. It will do so until another choke point presents itself.

In my experience I have always netted the most progressive gains by addressing the the exhaust first. get the engine to evacuate air as efficiently as possible, then address supply. Usually the intake, then the manifold, head/cam, throttle body. then start force-feeding.

I read through some of the Old Dynatek discussion and saw the plots. I also saw that the car was equipped with header, exhaust and CAI. They say the biggest gain was from the manifold, but there's no support for that. My guess is the mani only starts to help AFTER exhaust mods. and the plot has speed instead of RPM, which is also a bit strange.
 

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...balance is key.....
Well put Rstolz.
To achieve this balance on production engines, for the past 15-20 years or so, OEMs and engine centric companies (Ricardo, FEV, AVL, etc.) have totally depended on computer simulation software (e.g. GT Power and others) as the base for their engine development programs with final tuning on a handful of actual hardware.
 

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Discussion Starter · #12 · (Edited)
As far as i remember the dyno was done on a stock car, it has to be a scale of wheel speed because of the CVT, charting it to RPM would look weird to people.

Me saying the manifold becomes restrictive, well, i was talking about higher RPM's, for a 4 banger the redline is low, and HP usually drops before redline anyways. My theory is that the manifold can't supply enough air at high end, otherwise you could squeeze more peak HP out of it.
 

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it has to be a scale of wheel speed because of the CVT, charting it to RPM would look weird to people.
aye, good point there, my mind automatically assumes a manual trans.
 
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