INFINITI Reinvents The Gasoline Engine — VC-Turbo
 

they've put it in to production? that's good. Now we can see what kind of longevity they will have.

Uh, an exhaust turbo-charger with controllable waste gate is likewise a 'variable compression ratio' combustion engine...and far less dynamically complicated.

I don't believe they have released any efficiency numbers yet? Bold claims without data at this point. It may very well be more efficient, but at what cost, literally.

Personally I think car manufacturers should be spending MORE money on their engines/powertrains and less on "features". Things like variable length intake runners used to be commonplace, but now are usually cut out because it isn't "necessary". Screw that! Just think of how much BETTER it would be! I would gladly pay a few hundred dollars extra for variable length intake runners.

Fo you have any specs for these variable intake runners for the diy’er?

The expansion ratio is much higher at low load this way. A normal turbocharged engine cannot have both high power and high mechanical compression ratio.

When the engine is at low load and not developing boost, the low compression ratio really really hurts efficiency because the combustion temperature is low and the expansion ratio is low.

It seems really really complicated but if it doesn't cost them much to build then I suppose there isn't a problem. I personally feel like a better solution is to rev an engine higher when you need power and rely on the transmission to do the downshifting to make that happen, instead of trying to maximize specific torque at considerable expense. Electric motors are the future and electric motors have great instantaneous response so you don't need that low end grunt.

Making your own set of variable intake runners is not really in the scale of the DIY'er, thus why it would be awesome for manufacturers to fit them to engines to begin with! It would be more involved than making a set of headers, so if you haven't done that yet, don't even consider it.

My accord V6 has a variable length intake :thumbup:. It changes the sound enough that it sounds like I have two VTEC transitions, one at 4000 rpm, one at 4900 rpm.

Do you know the input parameters? I.e lengths and rpm ranges etc?

I am pretty handy sometimes :)

Could you snap a photo of your intake?

Is it just the intake length after the air filter?

I don't know for sure, but I am going to go out on a limb and say that with variable valve lift and cam phasing, variable intake length may not make a big difference anymore and not be cost effective.

Are we talking about this:

https://encrypted-tbn0.gstatic.com/i...tDkKGz7CsPgQ5Q



Or this :

https://encrypted-tbn2.gstatic.com/i...hEIoyC55XK_3Ig


The first one is very foable, the second one is also doable (for me) but the mnf will take a long time and if it doesnt work it i do not think that i can invest the time to do it again.

My variable intake doesn't use another set of runners, rather it has a chamber connecting either sides of the runners with a flap in the middle that opens at 4000, or 4900 RPM(don't know for sure which one. On the J25 it opens AFTER VTEC. I think on my J30 it opens before VTEC.). I don't know if it has any variable rpm/throttle position logic. Either way, the first transition is quieter than the second, if that helps you figure it out.

Here is a drawing. You can see the firing order listed, so when cylinder 1 is charged, it sucks all the air coming in down into cylinder 1. Cylinder 1 fires and the next cylinder is cylinder 4. With the flap closed, the air has to reverse and go all the way back around the loop and into cylinder 4. With the flap open, the air has to reverse and can go through the center of the intake manifold, shortening the path.
Attachment 23430

The older V6 accords did not have the variable intake manifold(the J30 didn't at least, don't know about C27), and here is what their intake manifolds look like.
Attachment 23431

My generation looks like this.
Attachment 23432

This is what my manifold looks like on the inside.
Attachment 23433

Probably true, most likely won't make a big difference, but it should still make a difference. It would be nice if they would develop these parts and make it an option to have them, or you can get the el-cheapo engine. I know which one i'm picking.

Variable intake is primarily useful on NA engines, whereas the trend is to go turbo. But yea they can be very effective. The 911 GT3 and Lexus LFA engines are NA, non-switchable cam profile 9000+rpm, but they have pretty good low end torque thanks to 3 switchable intake runner lengths.

I sure wish my CBR 250R had a variable intake... :( 17,000 RPM+, BIG headers, very oversquare, carburetors... It is not a recipe for good low or midrange torque. I still operate it at 3,000 RPM or below frequently though. It doesn't help that 45 mph in 6th gear puts it at 5,600 RPM(AFTER dropping 3 teeth on the rear sprocket), but I try.

Pre air filter length doesn’t count right.

I was thinking of doing the same with a hot air intake.

I’m pretty sure it’s pre throttle body that you are thinking about, but even then I have heard about pre throttle body intake piping that can be important.

Here is a Toyota version from a performance 4 cylinder (5E-FHE).

http://tercelreference.com/tercel_in...old_acis_2.jpg

http://tercelreference.com/tercel_in...old_acis_3.jpg

http://tercelreference.com/tercel_in...old_acis_4.jpg

http://tercelreference.com/tercel_in...old_acis_5.jpg

Lengthwise...it's from atmosphere to intake valve (actually to mid-point inside cylinder between cylinder head and piston top).

Ditto with the Mazda KL engine in one of my cars...very flat(read: maximum), very wide power band. Zoom-zoom!

that's a crazy complicated over weight system
I can think of three different ways to do that
with less part and weight

Though I agree that investing in efficiency increases to the ICE would be worth the investment, you know, most new car buyers won't even care about it. Unless they think it would give them some "bragging rights" :D