[rstolz]

This is a collection of information regarding Intake design, that will shed some light for folks on why Nissan is using low volume, long runner intake designs.

The short answer is for low end torque and engine response, improved idle quality and usable power where most folks want it. The reasons are below:

Stock intake manifolds are often a compilation of compromises. Stock manifolds are typically designed to minimize manufacturing cost, to accommodate emissions fittings, to fit a tight engine compartment with limited hood clearance, and to provide good low to mid-range performance, fuel economy and emissions. Most stock engines spend 95 percent of their running time between idle and 3,000 rpm, with rare bursts above 5,000 rpm.

Is Bigger Better?
The plenum in a stock manifold is typically smaller to keep air velocity high. Likewise, the cross-section of the runners is also small to keep the air moving at maximum speed into the cylinder ports. This provides good idle quality and throttle response, but also limits how much air the manifold can flow at higher engine speeds. Eventually the speed is reached at which the engine will try to pull in more air than the stock intake manifold can flow. That’s when the stock intake manifold needs to be upgraded to a performance manifold with a larger plenum and larger runners.

Runner Length
Runner length also affects the rpm range where an engine makes the most power. Longer runner lengths have a “ram” effect that helps keep the air moving forward as the intake valves open and shut. When an intake valve opens, there is a short lag before the cylinder starts to pull air through the runner into the combustion chamber. A longer runner helps maintain the inertia of the air column so it will fill the cylinder faster.

Information above comes from multiple sources (checked and double checked for accuracy), but the 2 paragraphs are directly from:Intake Manifolds: From Mild to Wild - Engine Builder Magazine
I couldn't have written it better, so I just borrowed it.

Also if you're interested in toying around with the numbers and science, this is a pretty cool calculator:
https://www.rbracing-rsr.com/runnertorquecalc.html
It's not all the parameters, but it'd give you a starting point.

 

[jswilson1987]

https://www.youtube.com/watch?v=GIALKZUnAc4

Personally I would rather have an engine with poor idle than have an engine that falls off before redline seems stupid to me to build a rotating assy that can rev higher than the head and intake can flow. Just my two cents. The versa definitely needs more cam and intake as it falls off bad about 5k. Personally I love choppy idle and blower surge

 

[jas32]

Excellent primer Rstolz. Engine design is always a series of compromises dictated by your overall objectives.

It appears in the past few years, active manifold seem to be falling out of favor for most "normal/ordinary" engines since most of these devices were added simply to get a horsepower number that the OEMs can advertise with very little benefit to the customer who rarely goes WOT or above 3500 RPMs (at a significant added cost to the engine).

There is a lot of science just on intake manifold design although you can throw most of it away if you opt to use a turbo/super charger where typically a simple log manifold is as good a solution as any.

 

[07Versa6MT]

https://www.youtube.com/watch?v=GIALKZUnAc4

Personally I would rather have an engine with poor idle than have an engine that falls off before redline seems stupid to me to build a rotating assy that can rev higher than the head and intake can flow. Just my two cents. The versa definitely needs more cam and intake as it falls off bad about 5k. Personally I love choppy idle and blower surge

Thank you! Damn right. What i've been saying forever.

Bottom line, OEM's compromise for a bunch of reasons, we know this. They usually get the balance right.

Jas32 exactly, with forced induction, airflow becomes a smaller issue, technically it is just as important if you want to squeeze as much power as proportions allow, but for the people who just want more power it's all out the window. You no longer need to worry about shape, size, flow, or anything, although it does help if you have a 4 banger with no torque until boost hits, drives like a bag of shit until that.

Deffinitely agree on the active manifolds/variable runners thing, it's just an engineering pissing contest.

Also JSwilson, i know for sure early MR20DE's (07-08) seem to be hotter from the factory, with longer duration cams. Maybe they did this to compensate for displacement, who knows.

There is deffinitely a limit to the driveability of a small engine, if you look at all the low displacement turbo cars everyone has come out with, they are shit buckets until you get the boost. Fine if you want the fuel economy, but i'd rather feel the power strong than have to wait for it. I drove some of the first 1.4T Multi-Air Darts for PDI's (Pre Delivery Inspection)when i worked at a Chrysler dealership a year or so ago, and honestly even the 6 speed manuals felt like slush, just gutless. Not enough power early on. The figures all look fine on paper but until you drive them, you don't know if you'll like where the power is located.

 

[robj80]

I just want a short stubby manifold that sits in front above the alternator. That way I can actually see the engine. I like the old days when you popped a hood and saw an engine and not a plastic cover or plastic intake manifold.

 

[07Versa6MT]

There's nothing really wrong with plastic. However, there is a fabrication/performance company here in London called "Re-Speed" that could likely build aluminum intakes similar to what Dynatek was going to do. All i'd need to do is deliver a stock manifold for them to look at. This is going to be another issue of interest though... with all bigger projects towards performance, they all fizzle out because there isn't enough people willing to spend some money on performance.

Dynatek from what i remember got more high end, and kept stock low end numbers, in fact i think the gains came on around mid range. From the pics it looks like what they did was enlarge the runners to a regular round pipe shape (that gradually tapers down to the oval shape of the head, that would be the hardest part of making these), and made the plenum a little larger.

 

[jswilson1987]

this is what any 4 pot needs along with a huge cam in like the .410 lift area

 

[07Versa6MT]

Problem is there's apparently no motivation for people to make their Versa's faster. Every other car has had everything done to it, why not us? I'm not being the guy that throws the thousands into his Versa, it's about a team effort. I can't bring myself to spend thousands on any cheap compact car, that's not the spirit of cheap and cheerful low budget cars that are still fun to drive. IMO that's part of what the import scene is about, cheap and cheerful. It takes more creativity and skill to make a compact import fun to drive and powerful, and clean looking, cheaply. Anyone with money can make any car faster, but frankly IMO it's more fun to do it on the cheap because it takes more research, and more creativity and you have more fun doing it. Spending thousands to turn a cheap import into a "Hellaflush" show car that has had all it's intended practicality removed, for no good reason, is what's wrong with the car scene today.

 

[jas32]

Problem is there's apparently no motivation for people to make their Versa's faster. Every other car has had everything done to it, why not us? I'm not being the guy that throws the thousands into his Versa, it's about a team effort. I can't bring myself to spend thousands on any cheap compact car, that's not the spirit of cheap and cheerful low budget cars that are still fun to drive. IMO that's part of what the import scene is about, cheap and cheerful. It takes more creativity and skill to make a compact import fun to drive and powerful, and clean looking, cheaply. Anyone with money can make any car faster, but frankly IMO it's more fun to do it on the cheap because it takes more research, and more creativity and you have more fun doing it. Spending thousands to turn a cheap import into a "Hellaflush" show car that has had all it's intended practicality removed, for no good reason, is what's wrong with the car scene today.

The Versa may be the best selling sub-compact car in the US for the past few years but it is quite obvious not very many people are interested in making them go faster. When there is a demand, that demand usually gets filled. Obviously that's not happening here.

If I were in the market for a fast subcompact car right now, I'd probably start with a Fiesta ST, simply because by the time I get a Versa to match the performance of an ST, I would have spent more money on a Versa and have to put up with the reliability problems of a one-off project. Sure you may have a unique car with the Versa but sometimes you'd wonder, should you spend more time tweaking the car or enjoy driving it? Personally I'd pick the latter, but to some people "its the journey that matters, not the destination".

 

[Note-ified]

The Versa may be the best selling sub-compact car in the US for the past few years but it is quite obvious not very many people are interested in making them go faster. When there is a demand, that demand usually gets filled. Obviously that's not happening here.

If I were in the market for a fast subcompact car right now, I'd probably start with a Fiesta ST, simply because by the time I get a Versa to match the performance of an ST, I would have spent more money on a Versa and have to put up with the reliability problems of a one-off project. Sure you may have a unique car with the Versa but sometimes you'd wonder, should you spend more time tweaking the car or enjoy driving it? Personally I'd pick the latter, but to some people "its the journey that matters, not the destination".

or you can just work on improving the power to weight ratio, which is always much cheaper than building up the engine, but then with that, there's always the trade off of practicality vs. performance. personally for me if i were to go for all out performance i would go that route and throw on an intake and exhaust and call it a day, but that's only because i have a second car that can fill the roll of the daily driver.

 

[jas32]

or you can just work on improving the power to weight ratio, which is always much cheaper than building up the engine, but then with that, there's always the trade off of practicality vs. performance. personally for me if i were to go for all out performance i would go that route and throw on an intake and exhaust and call it a day, but that's only because i have a second car that can fill the roll of the daily driver.

We're diverging away from the main topic here but unless you want to toss out your whole interior, sound system, A/C and other "non-essentials", making the car weigh less is much more challenging than making more power. I think that is why most people would rather attack the "power" side of the equation. Besides carbon fiber ain't cheap either.

It is amazing how Nissan significantly reduced the weight of the Note (from the previous Versa HB) by a couple hundred pounds and still passes all crash tests. It must be the magic of high strength steel.

 

[07Versa6MT]

The Versa may be the best selling sub-compact car in the US for the past few years but it is quite obvious not very many people are interested in making them go faster. When there is a demand, that demand usually gets filled. Obviously that's not happening here.

If I were in the market for a fast subcompact car right now, I'd probably start with a Fiesta ST, simply because by the time I get a Versa to match the performance of an ST, I would have spent more money on a Versa and have to put up with the reliability problems of a one-off project. Sure you may have a unique car with the Versa but sometimes you'd wonder, should you spend more time tweaking the car or enjoy driving it? Personally I'd pick the latter, but to some people "its the journey that matters, not the destination".

Yeah.. no, on my personal vehicles, money is no question. Whether it's financially worth it to spend money on go fast parts is of no importance to me... This is a little easier to swallow though if you only buy used. I don't care that if i wanted a car like the Versa except faster, i could pick up a used Mazdaspeed 3 for a decent price, but i don't care. It's the experience and journey for me, and the satisfaction that you did all the work.

I've never really been much for weight reduction. Sure, i'll toss out the heavy stuff like the spare tire (and put the battery back there just because it's the perfect space, and already has a factory grommet to run wires under the car). I like to have an interior that is the same as or better than factory. I've HushMatted my doors and did the entire rear floor pan/chassis when i ripped the rear seats out and all the wheel well trim, after most of the rear part of the car was done, i really noticed a huge difference. Just makes the car feel more cozy, cocoon like, and overall pleasing. Big difference in road noise generated by the rear wheels.

 

[rstolz]

Cool, actually getting some buzz.

I think a good cheap compromise would be to take your stock intake, split and enlarge the plenum.

This will increase the available pool of air to the runners, but leave the high velocity runners in place. Basically as the cylinders demand more and more air, it will be easier for the engine to pull it from an enlarged plenum.

It should also be almost a negligible difference to the low end unless you get ridiculous with the plenum. Modifying and tapering the runners would improve that effect further, but at significant $$ cost.

The long runners also negate or minimize backflow waveform. This is somewhat like the waveform seen in a 2-stroke exhaust. As the valves close, all the air rushing forward slams to a halt and rebounds backwards, the long runner diminishes the waveform, and isolates it to only the one cylinder at a time, so airflow is kept as smooth as possible. A short intake would see that waveform extend into the plenum, creating a massive amount of turbulence.

As mentioned earlier, boosted motors negate this with pressurization.

All OEMs will opt for low end smoothness in mass produced passenger cars.

Spot on with the comments about variable intakes; not worth the cost for OEMs.

Putting a car on a diet is a wonderful way to get performance and handling. strip out simple stuff, then start replacing parts with lightweight alternatives.

all cars taper off on power as you near the redline, the goal is to manage your powerband. Staying within the powerband is always more important than simply revving to redline. Accelerate to just past peak, then shift, as long as your quick enough, and the band is wide enough, you should get back on power shortly below peak torque, then climb to peak HP, and shift again before falling off the cliff (or hitting redline), and start all over again. easier said than done; when you're in a position to to use that strategy there are generally more pressing matters to keeping you occupied.

Of course that all changes with the CVT, when all you need to do is modulate throttle as speed climbs to keep the engine either at peak torque or peak HP, depending on the purpose.

 

[07Versa6MT]

As far as reducing rotating mass, i have Bob's lightweight flywheel waiting to go on, just need to get my MR20 motor, i have his OEM Exedy clutch kit too. Has anyone here at all put it on? I'm looking for feedback on how it drives after that, so i know what to (or not to) expect. My mind says it'll be a considerable difference in revving and getting to the powerband quicker, mainly since the stock flywheel is heavy (30 some odd pounds vs 11.4 for Bobs). He's told me through emails that mine was the 7th one sold, and most of the ones he sold went to Europe. He hasn't even put the flywheel on his own car, waiting till the MR20 swap like me.

 

[rstolz]

I'm waiting until I have to replace the clutch to get one, but get one I definitely will.

If it's anything like my project car, you'll notice it mostly on deceleration. Revs won't hang anymore before dropping, and they'll drop a whole lot faster.

You may notice more chatter and vibration, and some mild gains in low end response.

paired with that clutch, you're going to get much more aggressive and harsh shift points, will likely take a little getting used to, and a little practice to smooth it out. Nothing unbearable, but it will be immediately noticeable that the clutch setup is now for sport, not comfort.

Oh, and the pedal effort should increase a bit with the stiffer PP (pressure plate)

 

[07Versa6MT]

Not a clutch upgrade.. simply an Exedy (OEM) stock clutch, due to the mileage (337 000KM) it's a WYIT (while you're in there), and should make the swap faster with less unknowns, reusing parts is never fun, rather not have to think about it and just bolt a new flywheel and clutch on.

 

[rstolz]

Assumed the Exedy was an aftermarket unit. nevermind on the pedal feel then, but everything else should still apply.