Well I've babbled on in various intake threads about my theories with intake resonance and the TB>MAF>Filter SRIs not being the best way to go for top end power.

Now I have proof!

I made an intake/MAF that is 3.5" in diameter and 31" long, this gives a resonant frequency of roughly 100hz, which equals around 5500-6000 RPMs. I then tested it against the same exact MAF with the filter right on it instead of the full length. The resonant frequency at this length would be over 7500RPMs.

Super short intake is blue, longer one is red.



This is a picture of the length tuned one.



So long story short... Check out this link for a good formula and get some pipe for your intake... gain some power!
http://www.ftlracing.com/tech/engine/intake.html

 

Glad you posted this now. Had a short SRI in the works.

 

I have to say it Sparks, if that IM gave me 20BHP I still wouldn't put it on my car. I hope you have a cover for that dude.

Sounds freaking awesome though.

 

It is in a very rough state because I didn't want to spend the time prettying it up before testing it.

I will be cleaning up all the welds, extraneous pieces of metal from fab work, and having it thermal dispersant coated (black). Should look pretty slick, even if it is still a big box.

Regardless, for me, function > form.

Also: No covers are getting stuck on this engine

And to add, although it "only" gave 20 peak WHP, it was over 50whp gains at 7000rpms... and this car will soon be revving to around 76-7800.

 

You should contemplate making those for other members

 

It's in consideration. Would be cheaper than Kinetix for sure... Going to work out details and gauge some interest, already have a couple of people "in line".

 

LOL What's it made out of aluminum? Could polish up nice if there's enough material to bevel the edges a bit.

Thanks for posting this too, verifies that shorter is not always better.

Do you have known gains with the custom IM?

 

It's made out of aluminum yes. No need to polish it since I'll be doing the thermal dispersant, but the exterior will all be grinded down and polished to around 400 grit before it is put on, so it looks uniform and smooth.

Gains with custom IM.

 

Consider me "in line" as well.

 

DAMN that's impressive.

I'd take back my comment on not puttin it on my car.... but it wouldn't fit anyways right?

 

Sadly no. That 00VI isn't anything to joke about, though.

 

The intake plumbing with stock(ish) set ups is likely to vary greatly, I think, compared to your custom all the way.
Our tiny stock maf and TB would probably still benefit up top with the filter directly on it.

But there's no way around it that those are great gains without losing tq down low-mid.

Would like an SSIM comparison

 

The theory behind the whole thing is exactly the same... Acoustic resonance does not differentiate between custom or stock. My PB track times were all done with the intake pictured below. I ran WORSE at the track just putting the filter on the MAF.

Notice the stock manifold, stock MAF, and the same total length...

 

I just meant that the achievable air flow may be hindered with the piping. Probably not with 3"+ and a stack, but with the regular ol stuff that a lot of people have.

Not sure, just blabbing

 

The intake I pictured in my last post is just regular 3" exhaust piping. 2.75" ID just like the MAF, and just like any other 3" pipe you can buy. The engine is already pulling through plenty of piping, a few inches more to achieve both laminar flow through the MAF and some acoustic resonance at a usable RPM range doesn't hurt.

Most people use a velocity stack these days... If they don't, then they're missing out even more.

Also just to note, I still have the stock TB.

 

Thats friggin genius.I always like your posts as they are very informative.I am in line as well if this idea can be turned into reality.I think you should really consider it =)

 

Question for you sparks...

I did you ever test the diference between having the intake setup like;

TB>MAF>midpipe>filter

and

TB>midpipe>MAF>filter

I dont recal seing anyone do a direct comparison.

 

Never have, but judging from the difficulty of getting a solid tune the closer the MAF is to the filter, I prefer keeping the maf near the TB.

 

Which kind of engineer are you, again?

I read through that whole cluttered page and am struggling to pick out what the key formulas are. Are you using the one under Acoustic Resonance? I don't understand what you'd fill in for "n." Feed me.

 

In the case of our cars, N would just be one. What that means is the hamonics of the resonance point. On a high RPM engine, like 9000+ rpms... You can design an intake that resonates at say 4500RPMs, then at 9000RPMs which is a harmonic of 9000. That person would input 2 if they want to see what the second harmonic is. To build an intake that has multiple harmonics at the low RPMs that we turn, it would need to be ridiculously long and certainly acquire pumping losses. (I'm just a former radar/electronics technician that likes math, nothing more)

 

+1 for Interest in this manifold should you decide too produce them.

 

Me too, amazed me on that 280 to the wheels...are you running Cams Sparks or are they some where down the line also....

 

That is with stock cams.

I have some BC S2s sitting on my shelf waiting for valvesprings, rod bolts, and some other stuff to be installed along with them.

 

Great thread and info Sparks! I'll be going to a different intake setup soon when I'm tuning, but put me down as interested for a manifold as well. Is there a thread you created regarding that or is this the debut? Props to the work put in for that + the intake research.

 

http://forums.maxima.org/all-motor/6...yno-gains.html

There's a link to the dyno thread from there.

 

I would like one in blue or red jk. Looks real sporty, I like the whole setup, will the engine cover still be able to fit and can the battery and other parts you modified stay stock and in there stock positions?

 

This thread is purely about the merits of a very short vs proper length intake piping. As to your questions... Take your time, think it over. The answers are already there.

 

 

How about stock intake performance?

I am running the stock 4th gen intake (complete intake) with a fairly new panel filter on my 3.5 swap, it pulls pretty hard.

 

think you speak for yourself on that bruh...

 

I am sure that the nissan techs designed it for optimal acoustic performance. With boltons, however, you would most certainly see gains going to a real intake. I even gained going from a free flowing 3" intake and stock maf to a 3.5" intake and maf.

 

A little OT Sparks but what are your opinions/findings with intake set-up on the DE-K ?

PM if you prefer

 

The whole acoustic resonance thing does not differentiate between engines or intake manifolds. When determining the length you want, just make sure to add the length of the elbow and TB to the MAF and pipe.

 

The Fontana guys know what's up... Looks like this thing is tuned to resonate somewhere in midrange and again at the next harmonic in the high RPMs.

 

PM'd cause you lost me completely

I love the zip tied reservoir cap on the right side of the Z bay LOL.
That just looks fast.

Have you tried a CAI set up with that IM?

 

So is It intake,Midpipe,MAF,TB or intake, MAF, midpipe TB ? I'm lost just list order of parts if not already plz

 

A CAI would not get the length I need, and I am already getting cold air through the giant CAI hole in my fender right below the filter.

Just to share my response with others...

The length I am talking about is the full length of the air intake into the plenum. This includes the elbow, TB, MAF, and pipe. The formula to determine resonant frequency is pretty simple.

F=V/4(L+(.6D))

F=Frequency. Multiply this by 60 to get RPM
V=Velocity of air. 330-340 is pretty normal
L=Length of intake pipe, in meters. 39inches=1 meter
D=Diameter ofintake pipe, in meters.

So if you want it to resonate at 6000 RPMs with a 3 inch pipe, you do this:

6000/60=100hz
3"/39=.077meters

100=340/4(X+(.6x.077))
100=85/(X+.0462)
100(X+.0462)=85
100X+4.62=85
100X=80.38
X=0.804
L=0.804 meters
.804x39=31.3 inches

So if you want a (roughly) 6000 RPM setup, take length of elbow + TB (use string to measure curves), then subtract that from 31. The remainder is the length that your MAF and intake pipe needs to be.

It completely depends on your setup. Look at the pictures, look at what you have and what you need, and figure it out.

(hint: if you need PCV, then it can't be before the MAF)

 

Also, that's a 470bhp engine... one of the highest HP NA VQ35DEs out there.

 

Is the red tubing between the TB and filter 3.5" or 4"?

 

3.5". The whole intake/TB/elbow on that is 90MM.