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Engine Specific Info and Questions => IDI Engine => Topic started by: Vanagoner on January 03, 2010, 08:46:43 am
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I really want to see how much I can wring out of my N/A vanagon. Turbo for me means a lot more than just slapping a spinner on there and I just can't afford all of the upgrades needed to do it well. So I'm upgrading the breathing on the n/a while I save up for a performance diesel IP.
I already got a dual downpipe exhaust for it and changed to an external cone air filter. Now I'm looking at the intake manifold.
Calculations for optimal runner length for each intake tract (placing 2nd 3rd and 4th harmonics into the 2000-4800 rpm range) comes out to 33 inches!
do you think it would work to use braided stainless hoses instead of hard tubing for this app? If I did, I could run them up into the D pillar, terminate into a box with velocity stacks and have a nice big cone filter there for them. I know it sounds goofy, but do you think it would work, or make a difference?
IIRC 2nd harmonic +10%, 3rd harmonic +7%, 4th harmonic +4%
I know this is no VNT build, but thanks for looking.
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I'm doing as you are, but already have one of Giles wonderful pumps. Thing is that i can feel that my intake and exhaust are restricting higher revs. Next year i'll build up an exhaust with a dual manifold, 2" pipe etc. As for an intake i guess you can go all nuts and fab something up with long runners like you say, but there has to be diminishing returns at some point. I am gonna just use a 1Y or 1X intake and put an air filter box at the bottom of the d pillar and seal it off so the air box is pressurized
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Why get a different pump? Without the extra air of a turbo, the stock pump should be more than capable of giving it all the fuel it can handle.
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Why get a different pump? Without the extra air of a turbo, the stock pump should be more than capable of giving it all the fuel it can handle.
I suggest you read all you can about pump modifications and what is possible to do. I'm sure i have 10-15 more hp than with a stock pump- with more to come.
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I really want to see how much I can wring out of my N/A vanagon. Turbo for me means a lot more than just slapping a spinner on there and I just can't afford all of the upgrades needed to do it well. So I'm upgrading the breathing on the n/a while I save up for a performance diesel IP.
I already got a dual downpipe exhaust for it and changed to an external cone air filter. Now I'm looking at the intake manifold.
Calculations for optimal runner length for each intake tract (placing 2nd 3rd and 4th harmonics into the 2000-4800 rpm range) comes out to 33 inches!
do you think it would work to use braided stainless hoses instead of hard tubing for this app? If I did, I could run them up into the D pillar, terminate into a box with velocity stacks and have a nice big cone filter there for them. I know it sounds goofy, but do you think it would work, or make a difference?
IIRC 2nd harmonic +10%, 3rd harmonic +7%, 4th harmonic +4%
I know this is no VNT build, but thanks for looking.
Wow. How do you calculate that? I think stainless hoses wouldn't be the best but I don't know what you could use.
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I'm not talking about getting a turbo pump, but a performance n/a pump.
Caveman, I notice a real improvement from about 75 Kph on up with an enclosed airbox intake in the D pillar. It helps me hold slight inclines at highway speed much better and willingly keeps pulling 'till I run out of gears, which happens pretty fast with my absurd transaxle.
Ok engineers, do you know any reasons why this choice of material (smooth hose with braided stainless sheath) would be unsuitable as an intake runner?
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33 inch runners? you messed something up. nothing should need 33" runners, added length actually impedes air flow.
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Right on Rabbit, I dropped it. Should be 16 1/2" total, thanks. Question remains the same regarding the tubing. I don't want a lot of weight/stress on my intake manifold and I don't have a lot of room to work with.
TheMan, for calculations I found some links off of vwvortex which I can't find now. There are a lot of them out there.
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16 1/2 inches sounds about right. probably really close to the same length of the runners on the stock manifold.
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16 1/2 inches sounds about right. probably really close to the same length of the runners on the stock manifold.
True for a Rabbit intake, but those don't fit on a vanagon, and the stock intake is stubby-
(pic taken from thesamba classifieds)
(http://images.thesamba.com/vw/classifieds/pix/medium/3000539.jpg)
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Thanks for weighing in, Andrew. I think that the runner length/airbox on the n/a vanagon was selected for convenience of installation, not performance. I think that a shorter intake runner length resonates at a higher rpm, not a lower one.
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I'm pretty sure they dropped the max rpm and max hp on the diesel vanagon specifically to increase low-end torque. The max HP rating was dropped from 52HP to 48hp in the vanagon. I imagine that part of that was specifically resizing the runner lengths for lower rpm torque.
That's weird, I'm pretty sure in other cars the 1.5 was 48hp and the 1.6 was 52hp. So your saying they dropped the 1.6 to 48hp? :P I bet they were good drag racers haha, 0-60......hopefully!!!!
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I'm pretty sure they dropped the max rpm and max hp on the diesel vanagon specifically to increase low-end torque. The max HP rating was dropped from 52HP to 48hp in the vanagon. I imagine that part of that was specifically resizing the runner lengths for lower rpm torque.
That's weird, I'm pretty sure in other cars the 1.5 was 48hp and the 1.6 was 52hp. So your saying they dropped the 1.6 to 48hp? :P I bet they were good drag racers haha, 0-60......hopefully!!!!
Yep, they DE-TUNED the 1.6 for the Vanagons!?! When I first got mine in stock trim it was terrifyingly, dangerously slow. It is much better now (kinda keeps up with most traffic up to a point), but still workin' it.
I got the first calculator off of this thread-
http://74.125.47.132/search?q=cache:a9elpcbn4o0J:forums.vwvortex.com/zerothread%3Fid%3D942528+%22velocity+stacks%22+length+calculator+vwvortex&cd=1&hl=en&ct=clnk&gl=us (http://74.125.47.132/search?q=cache:a9elpcbn4o0J:forums.vwvortex.com/zerothread%3Fid%3D942528+%22velocity+stacks%22+length+calculator+vwvortex&cd=1&hl=en&ct=clnk&gl=us)
which is here-
http://www.bgsoflex.com/intakeln.html (http://www.bgsoflex.com/intakeln.html)
which confirms 33 inches, but the other rule-of thumb calcs come in at 16 inches.
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Interesting thread !
I also am debating on whether to continue running
my 1.6D daily as I have an MF and an AAZ at my disposal.
The car drips rustproofing, and I just love it to pieces so
it's a keeper and I would find it kind of neat to hop it up in
N/A version. The relibility and simplicity are appealing to me.
I guess things to do : Exhaust, intake and Giles pump.
Are the ME / MF heads / valves same?
Hugh
PS : Caveman, I am in Laval, would be nice to hook up at one
point, you have a lot of knowledge it seems.
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Hey Laurentian. i work at Pinzgauer Canada on Cure Labelle in Ste Rose if you can pass by there.
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Thanks for weighing in, Andrew. I think that the runner length/airbox on the n/a vanagon was selected for convenience of installation, not performance. I think that a shorter intake runner length resonates at a higher rpm, not a lower one.
AFAIK, the Vanagon intake manifold box is the same as the A2 NA cars, but the cover is different.
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Sorry, need help with "A2", what is that in the U.S. market?
[ and I just noticed you have a Kubvan! what fun. I found one here but haven't tried to buy it yet]
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Ok, apparently the long runner idea is nothing new. Here is an historic 30" setup-
(http://img.photobucket.com/albums/v628/BigBlockMopar/1960ChryslerNewYorker/RamInduction.jpg)
and the explanation that goes with it-
http://www.chrysler300club.com/uniq/allaboutrams/ramtheory.htm (http://www.chrysler300club.com/uniq/allaboutrams/ramtheory.htm)
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and a good overview of "acoustic supercharging" (with equations)-
http://www.team-integra.net/sections/articles/showArticle.asp?ArticleID=466 (http://www.team-integra.net/sections/articles/showArticle.asp?ArticleID=466)
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Sorry, need help with "A2", what is that in the U.S. market?
[ and I just noticed you have a Kubvan! what fun. I found one here but haven't tried to buy it yet]
A2=MkII, 85-92
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most super long runner intakes are meant for SUPER HIGH rpm use. think of a tunnel ram on a gasser? does it make any torque or power down low? dont think so...
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The engine pictured above is tuned for 2800 rpm. It is in this car-
(http://www.vancouverclassiccars.com/images/1960CHRYSLER300f_750.jpg)
which is not the paragon of high rpm engines. :)
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still tho, that intake pulls harder at 6000 then any manifold with shorter runners. generally long runner intakes are meant for high rpm use. and just cause that car is tuned to 2800, that manifold still has way more top end than the non-cross-ram intakes. im not trying to disprove you, im just saying that they are generally for super high rpm use where no torque is needed.
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I don't have all the answers either, still trying to figure this out. I would welcome information that supports the long runner= high rpm thing, but I think both of us can be right on this one. Just as 16 1/2" came up on some formulas as a good equivalent to 33", so too 3000 rpm target is also a 6000 rpm target. Harmonic waveforms occur most strongly in octaves, so we can both be right.
At this point I'm just trying to understand the benefit of using a long runner vs. a short one.
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Fab up both and try them out :) See first hand what it does
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You should make a variable length intake like these. ;)
http://www.autozine.org/technical_school/engine/tech_engine_2.htm (http://www.autozine.org/technical_school/engine/tech_engine_2.htm)
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kinda hard to make a variable intake when we only have one intake port per cylinder. those ones were so good because each cylinder had 2 ports.
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T-saurus, that is cool, never knew about that (I'm stuck in the '80s). Looks like variable intake is for n/a engines what vnt is for turbos.
I figured out why the long tubes (from wiki)-
"When the intake air speed is higher, the dynamic pressure pushing the air (and/or mixture) inside the engine is increased. The dynamic pressure is proportional to the square of the inlet air speed, so by making the passage narrower or longer the speed/dynamic pressure is increased."
So choosing a long tube length over a short tube length with the same rpm target yields more force.
8v, right you are. as soon as cold lets up (have no inside workspace) I'm going to play with a fixed long tube prototype for grins, to see if it makes any difference. Maybe think about variable intakes or learn to play trombone later... :)
Thanks guys, that VIM stuff is mind opening- looks not so hokey after all.
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but one important thing, the fuel and air are not even mixed until its time to fire. so long runners are not going to help mix the fuel/air charge in this case. they may make it a little easier to breathe for the engine tho.
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most super long runner intakes are meant for SUPER HIGH rpm use. think of a tunnel ram on a gasser? does it make any torque or power down low? dont think so...
Have to argue that point, at least as to the causes of crap low rpm performance. Look at the runner diameters sizes on the so-called "tunnel ram" manifolds; they're huge! The low rpm air velocity through those manifolds is terrible (carbs or f.i.), but they don't run RV cams with them either. Race stuff.
My German Ford 2.9L gasser has short/straight runners & smoothly hits its factory redline @ 5800rpm, sounding like it's ready for much higher revs. The same basic 2.9L in Ford Ranger, Bronco II,et. al. had intake runners at least twice as long, a bit more torque from 800-2200 rpm, and sounded like it was all out of useful power and revs at 4200 rpm... typical small truck motor, before electronically-controlled valves, dual intake tracts, etc.
The same runner length differences were evident in the EFI Mustang 302 V8s vs. the EFI 302 V8s in the trucks.
Superchargers and turbos take away part of the low rpm advantage of the longer intake runners vs. shorties, but only when they start to cook up some pressure.
In the 1980s Oldsmobile did some experimental multiple-runner-lengths manifolding for their V6 version of their horrible 350-inch V8 diesel, in hopes of broadening the rpm range over which the V6 produced usable torque. It worked quite well, but GM did not figure the extra expense was worth it, and they made more profits selling buyers up to the POS V8 diesel engine. (Oddly enough, the cast-iron head version of the Olds V6 diesel wasn't generally too bad, just never developed & offered to the public in a version with power to match its weight and displacement, only 85hp from 4.3L!)
J.R.
SoCal
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From Audi of America's website-
Variable Intake Manifold
"Depending on engine speed, intake manifolds of different length are advantageous. These requirements can be met by installing a variable intake manifold: at low engine speeds a longer pipe increases torque and improves responsiveness. At higher speeds the shorter intake manifold is effective for high performance. Variability is the basis for an optimum torque curve over the entire engine-speed range, as well as for good acceleration and elasticity."
I agree Kevin that a long, small diameter pipe doesn't seem like the thing to use because it would be like breathing thru a straw. But apparently if you get it right you turn the intake into a horn, focusing and delivering pressure waves to the engine at the right times, and flow is increased. It is about the energy of sound. A final illustration of length as a function of pitch (rpm) comes from the physics of music-
"The pitch produced by a pipe is a function of its length, the wavelength of the sound produced by an open pipe being approximately twice its length. A pipe half the length of another will sound one octave higher. If the longest pipe, C, is 8 feet (2.4 m) in length, the pipe one octave higher will be 4ft long, and two octaves above (middle C) will be 2ft long. "
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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-
(http://www.theconcertband.com/images/Harmonic%20series.gif)
I am wondering however, Where is the fundamental in the Bowling/Grippo chart?
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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?
(http://www.csounds.com/ezine/winter1999/beginner/sine.gif)
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http://www.bgsoflex.com/intakeln.html (http://www.bgsoflex.com/intakeln.html)
http://dairally.net/daihard/chas/MiscCalculators/DaiPipes.htm (http://dairally.net/daihard/chas/MiscCalculators/DaiPipes.htm)
http://www.velocity-of-sound.com/velocity_of_sound/calculator1.htm (http://www.velocity-of-sound.com/velocity_of_sound/calculator1.htm)
http://www.rbracing-rsr.com/runnertorquecalc.html (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 (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.
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http://www.bgsoflex.com/intakeln.html (http://www.bgsoflex.com/intakeln.html)
http://dairally.net/daihard/chas/MiscCalculators/DaiPipes.htm (http://dairally.net/daihard/chas/MiscCalculators/DaiPipes.htm)
http://www.velocity-of-sound.com/velocity_of_sound/calculator1.htm (http://www.velocity-of-sound.com/velocity_of_sound/calculator1.htm)
http://www.rbracing-rsr.com/runnertorquecalc.html (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 (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.
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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.
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Turbo. ;)
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I knew someone would say that! :P
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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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Breathing...
I could make a cool header but this one will do for now-
(http://lh3.ggpht.com/_Go_LAm7t3go/Sy1OpK8hxVI/AAAAAAAAAEw/_Z3NOBRz-9g/Exaust%20assembly%2009%27.jpg)
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 :D ). 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.
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A Can on a Vanagon I LOVE IT!
It will look right, as opposed to on a honda or a cavalier... it will be proportionate in size at least.
That whole setup of exhaust doesn't look the least bit restrictive, it shall do well!
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Sorry to derail this somewhat, although he seems to have come to his conclusion already.
Before I begin, everything below is just my thinking... no sources or data behind it, just interested to see what some of you guys think about it.
I'm thinking that a long runner intake might be a bad idea on a diesel.
On a gasser, they measure airflow and air/fuel mixture and inject the right amount of gas to use up all the air you're pumping through the engine. However, on a diesel, there is no air measurement needed; it's completely linear to your rpm; ignoring boost pins etc for now.
I made a graph to help describe what I'm thinking.
X axis - RPM
Y axis - Air pushed into each cylinder or fuel for the green line
Green - Fuel
Purple - Long Runner Intake
Black - Short Runner Intake
A long runner intake will have bigger fluxuations occurring more frequently. The fluxuations will be more severe at lower rpm's and flatten out as you increase in rpm's (something I couldn't figure out how to manipulate the graph to show).
A short runner intake will have smaller fluxuations and a lower frequency, as shown by the blue line... in theory as you approach zero, the line will become straight.
Any time the Red/Blue lines are above the Green line, you have extra oxygen you're pushing through that's not being burnt. And, when the Red/Blue lines are below the green line, you've got black smoke. If you turn the fuel up so it cuts through the tips of the waves, you'll be puffing black smoke 90% of the time, but if you turn it down to the bottom, you'll be giving up precious air.
While across the whole rev range, the long runner intake might give you more air; particularly at your desired RPM ranges, given this theory, the short runner intake is the *more efficient* design. That is obviously exaggerated and over simplified, but I'm more questioning the theory.
What do you guys think of that? I'm not a fan at all of the intake on my AAZ, but I think the key to a good intake is keeping it free flowing and getting even air to all cylinders. I've got a few ideas for the latter, but my car is a LONG way from getting a custom intake manifold made ;)
(http://xs.to/image-817E_4B495B1E.jpg)
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Hi Rado,
not done just taking a break ;)
Is your AAZ a turbo? If so, you are right and this doesn't apply to you. As you said, you just want something free flowing that will distribute air to all cyls evenly.
This thread ponders the most effective way to create harmonic or acoustic supercharging on an N/A by tuning the pipes. I agree, long pipes would be a waste of time on a TD.
P.S. Sorry Caveman, I missed my window for getting pics up this weekend
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That's okay NO PRESSURE ! ;D. I was trying to find photos on the Club 80-90 forums but with no luck, just so you can see what it looks like and how tight it is. My contention of using a 1Y intake is that we think we know better, but VW did pay engineers money to figure this all out .