N/A intake idea, OK or hokey beyond belief?

[Vanagoner]

Also, I think I'm getting a handle on the 33" fixed pipe chart-
"Intake Runner Length Computation by Bowling and Grippo
Computation Results:
# Input length is 33 inches
# For 2nd harmonic, RPM range is from 3560 to 4320 with a pulse strength of 10 percent
# For 3rd harmonic, RPM range is from 2675 to 3057 with a pulse strength of 7 percent
# For 4th harmonic, RPM range is from 2085 to 2332 with a pulse strength of 4 percent

Bruce A. Bowling
Al C. Grippo"
Here is a chart of single-octave nodes in the natural harmonic series-


I am wondering however, Where is the fundamental in the Bowling/Grippo chart?

[RadoTD]

I am wondering however, Where is the fundamental in the Bowling/Grippo chart?

The Fundamental tone is below the range where the resonating effect will help you.

Use the picture I have below, it's your second harmonic but only one line. As far as we're concerned, that line represents air intake pressure at the valve.
Between the 1st and 2nd nodes, 1/4 of the way into that graph, the line (pressure) is at it's peak. We want the valve to be open then. But now when you close the valve, the air bounces back away from the valve creating lower pressure at the valve (between 2nd and 3rd nodes, where the line is at the bottom). This low pressure then begins to suck air back towards it and hopefully you're opening the valve again as it brings more air towards the valve.

What the Bowling Grippo chart doesn't say is that your "pulse strength" is actually weaker off those harmonics; you end up opening the valve between the 2nd and 3rd nodes below, reducing the air drawn into the cylinder. The effect can be quite significant at the fundamental.

Each of those harmonics shown equal two revolutions of the engine, so the intake valve opening once. In the fundamental, if the valve opens at the pressure peak, the next time it'll open when the pressure is right at the bottom. Going up to the 4th harmonic, the high pressure wave actually hits the valve twice.

Did that make any sense?

[clbanman]

http://www.bgsoflex.com/intakeln.html

http://dairally.net/daihard/chas/MiscCalculators/DaiPipes.htm

http://www.velocity-of-sound.com/velocity_of_sound/calculator1.htm

http://www.rbracing-rsr.com/runnertorquecalc.html

This link mentions David Vizard's method of calculating intake runner length which was one of my first exposures to the concept:
http://www.team-integra.net/sections/articles/showArticle.asp?ArticleID=471

In my opinion, working on the exhaust first will likely result in more gains than working on the intake without modifying the exhaust.

[Rabbit on Roids]

http://www.bgsoflex.com/intakeln.html

http://dairally.net/daihard/chas/MiscCalculators/DaiPipes.htm

http://www.velocity-of-sound.com/velocity_of_sound/calculator1.htm

http://www.rbracing-rsr.com/runnertorquecalc.html

This link mentions David Vizard's method of calculating intake runner length which was one of my first exposures to the concept:
http://www.team-integra.net/sections/articles/showArticle.asp?ArticleID=471

In my opinion, working on the exhaust first will likely result in more gains than working on the intake without modifying the exhaust.

X2

make it easier for the air to get out before you go making it easier to get in. cause if you can get tons in, but you cant evacuate it, you have back pressure. and you dont really want any back pressure in a diesel.

[87octane]

there's some software called Engine Analyzer from Performance Trends that let's you model different runner cross section and lengths to see how it effects the power curves. For more money, the "Pro" version has an "optimizer" function where you start out with stock dimensions, choose criteria such as "broadest torque curve across specified rpm range" and it will tell you the optimal cross section and length. Also does exhausts, cams, and everything else. It is gasser s/w but  intake runners are about cylinder filling per rpm, not about the fuel used.

[TurboJ]

Turbo. 

[Vanagoner]

I knew someone would say that!
You're right on the exhaust, I have a 2 1/4" magnaflow muff. installed, and a set of dual pipes with a GTI manifold I got off of a tiico conversion.  I'll post pics when I can.
Thanks for the software tip, but I am stuck with freeware.
and thanks Rado and clban for those, great explanation, and links to wade thru.
I don't think that an amplifying system has antinodes that would suck energy though.  Just stronger and weaker subharmonics of amplification.  Not like an exhaust resonator which acts like this, only in reverse.

[macka]

Have you opened up the intake and exhaust ports on the head? This will free up flow quite a bit. A proper port and polish will make a difference, and allow your aftermarket upgrades to work better. As I see it right now, that is where you are the most flow restricted.

[Vanagoner]

No, I haven't done that yet.  I have a nice German casting on my spare engine and will do that over time, but that is not the most restrictive thing so far.  The Vanagons had the most miserable of all exhaust manifolds/ mufflers ever made, restrictive intakes and de-tuned pumps.  I'm trying to clear that away gradually.  Adding a stock mkII pump, cone air filter and exhaust made a huge difference (relatively speaking).  After I get a good intake plumbed I'll be ready for a port and polish, and performance pump.  I don't know anybody else doing a "performance" n/a on a vanagon, most go straight to turbo.  If I get 75-80 engine HP out of it I'll be happy.  I found an air cooled 5-speed transaxle for it and that combo will be good enough for me.

[the caveman]

I'm sure i already have 75-80 hp already with the Giles pump and basically stock intake and exhaust.  It's almost as fast as a stock 1.6 TD .With better flow maybe another 10-15 ? Is that even possible? No dyno yet, but once i get the exact weight i will test it with my G-force dash analyser thingy.
As for the intake i really believe you are over thinking it. unless you have a very easy way to build up an intake you will see very small gains for time spent.

[Rabbit on Roids]

I'm sure i already have 75-80 hp already with the Giles pump and basically stock intake and exhaust.  It's almost as fast as a stock 1.6 TD .With better flow maybe another 10-15 ? Is that even possible? No dyno yet, but once i get the exact weight i will test it with my G-force dash analyser thingy.
As for the intake i really believe you are over thinking it. unless you have a very easy way to build up an intake you will see very small gains for time spent.

x2 on that.

if you want to build something out of tubes, build yourself a cool header. that would be worth your time. we know that a header will *for sure* add power. a different intake *might* or *might not* make a difference. the stock n/a intakes are actually a pretty good setup.

[macka]

would a regular 1.6 N/A intake be an upgrade? It seems like this would be a quick fix by the way you are talking. You could also take a gasser approach and do a "crackpipe" style intake, but if this style of setup would work is anybody's guess.

[Rabbit on Roids]

i would use a G60 or mk2 intake. the runners are significantly bigger than the mk1 unit. also, the intake runners are tapered on the mk2 and g60 intakes. makes them really work great when you decide to bolt a turbo on under it. but honestly the only way it will be better than a n/a intake is if you supply it with nice big intake tubing. i would have it atleast 2.5 inch going into the mani. and atleast 3" if not a little bigger going from there to the air box or cone filter. so basically, if you arent going to build a good intake for the gasser intake, dont bother using it.

[the caveman]

would a regular 1.6 N/A intake be an upgrade? It seems like this would be a quick fix by the way you are talking. You could also take a gasser approach and do a "crackpipe" style intake, but if this style of setup would work is anybody's guess.

That's what i have now. I welded and shaped the face of the manifold to match the "D" shaped ports of the head. Problem is that i don't think the rest of the runners have the same cross section all the way through and i think they could use more length . That's why i'm just gonna  find a 1Y intake and a pressurized air box. Problem with that manifold on a vanagon is that it's a VERY tight fit. may have to slice an edge off it.

[Vanagoner]

Breathing...
I could make a cool header but this one will do for now-

8v 6 bolt dual mani, looks nice for flow (don't know what it is off of originally).  The pipes are solid, so I'm going to use 'em.  The magnaflow I got for $20 off of a young Honda owner who said it wasn't LOUD ENOUGH for him.  I have it hooked to my single pipe mani now and it is kind of loud, so maybe I'll add a resonator when I can find one (but I love the tone ).  I just have to hoist my engine up a little this weekend to pull the motor mount to get the header/ pipe on, and weld a bracket to the end of the pipe so it doesn't wag itself to death.
Maybe I am overthinking the intake.  I am still interested in harmonic intake design principles though.  And most stock intake manifolds, while good, and some are very good, don't fit on vanagons.  I don't mind cutting on my bus if it helps, but it should be worthwhile.
Caveman, I'll get some pics of my D pillar airbox "prototype" up this weekend.