Why explain something so basic......
If you increase "plentum" ( your spelling ) volume then by definition it increases air quantity or amount.
So let's define the words....isn't volume the amount of space occupied by a three dimensional object such as a plenum ? And doesn't "amount equate to "quantity" ?
You may be confused with air flow or CFM which isn't altered and I didn't mention.

TB spacer increases the plenum volume of the intake manifold.
This gives the engine a larger plenum to draw its air from at each firing cycle, so velocity in the intake manifold is increased, because it no longer has to rely as heavily on the throttle body for air at each given firing cycle.

What do I know, unlike you I'm new at this, so don't believe me, just read a few SAE papers on the subject.


Once again you're correct, forgive me for being simplistic in a world that is so complex...

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http://i19.photobucket.com/albums/b1...c/GOWIDE-1.jpg
1971 280SL ROADSTER
1988 300CE TWIN TURBO WIDEBODY
1994 E320 CABRIOLET
1999 C43 AMG
2005 G55K AMG
2008 CLK63 AMG BLACK SERIES

Never seen someone get so unprofessionally defensive so quickly, especially someone who so sarcastically attempts to be as old, seasoned, and well adjusted as yourself.

First, I did not dispute that it increased plenum volume; I also didn't say that it had any positive or negative effects on power (though it's discussed later).

To start, you said that a spacer increases:
Which in the purest sense, it does not. A throttle body that has X diameter, will only flow a certain amount of air at a certain velocity, increasing until the air goes supersonic, and then a whole set of rules applies. You already knew this. If an engine requires 100Mol of air, a spacer after the throttle body isn't going to make that same throttle body now pass 105Mol of ambient air through it. The only thing it will do is reduce the % of the plenum that is reduced at each individual intake event. That just means that there is more time per intake stroke to replenish the lost air. Given that during one revolution of an engine, the amount of volume removed from a plenum stays constant independent of plenum volume. This also means that the amount of air the throttle body has to flow is also independent of plenum volume.

Since you were very quick to tell me to go look in peer reviewed journals, but were so slow to post one yourself, here:
http://muhserv.atauni.edu.tr/makine/akifceviz/pdf_files/A/e.pdf

Now if you'll investigate Figure 8, you'll find that this manifests itself as a decrease in pressure drop as the plenum volume increases.


You said:
Now given that the published paper states that the engine has a higher manifold pressure (less pressure drop), Bernoulli's principle states (from wiki):
Now that means that an increased plenum volume will actually decrease velocity of the air flow. Either that, or a whole bunch of airplanes have been flying on voodoo and prayers for a century now.

This means that it does nothing to increase the flow of the throttle body. What it does mean is that given a lower intake velocity, there is more time to replenish the air in the plenum. It still has to flow the exact same amount of air. Call it Mol, Kg, lbs, what ever else floats your boat.

Let's recap:

Correct
Incorrect
Not sure what you mean by this one. It still relies on the throttle body, but the rate changes. I'll go halfsies?

Edit: let's even do some maths:
On your example, an LS2, the throttle body is 90mm in diameter. Given that the spacers appears to be 1" in length, you've achieved a 161.59 cm^3 increase in plenum volume, or approximately 2.7% of total swept volume.

To achieve results, the test engine was a FSAE 600cc engine (see sources 11,12) and they used either a 90cc or 180cc (cm^3) increase in plenum volume which equates to either 15% or 30% of the swept volume, respectively. How much effectiveness would you see on a spacer that is between 5 and 10 times smaller? Now this does not take into account the overall change in volume of the plenum as a percent of the original. Though on page 3 (963) he does state that:
Which means, past a certain point, increasing plenum size is detrimental to performance. Bigger =/= better.

As far as the carb comment, you said:
In reference to using a throttle body spacer. I'm sure you're well aware of the fact that carb spacers are just as much to do with getting equal mixture distribution as it is plenum size (no really, I'm sure you do now that). So if you're saying that the throttle body and the throttle plate on carbs function similarly, than yes. However if you're saying that the spacers serve equal function, the point I thought it sounded like you were attempting to make, than no.

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1993 190E 2.6 Sportline

Anyone care to comment on silicone joiners & their risk of "sucking in" (collapsing) & therefore hindering air flow? This is concerning too much silicone joiner length allowing too much flex. Reason I am asking is I have heard that this occurs with intercooler joiners & results in "boost creap" due to unwanted change in air volume.

You wouldn't want a huge sucking in/collapsing @ the tb join

I know of some using very limited joiner length for piping joins to overcome this.

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um.....why have men got nipples

Most long couplers, at least on big trucks, have springs on the inside so they keep their shape under vacuum. More importantly, how the hell can it cause boost creep? You cant have a body implode under positive pressure.

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1993 190E 2.6 Sportline

I was merely pointing out the silicone joiners used for cars & they don't have springs as far as I'm aware. Intercooler hoses can collapse with age or perhaps cheaper, thinner ones? Maybe that was the issue I had read? Was just keen for others experience, that's all.....

The boost creap may have come about from the use of the crap non-layered silicone vacuum lines sold on EBay, not the intercooler type so I may have mislead you on that one.......

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um.....why have men got nipples

your scaring me,I just ordered my nitrous kit

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1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt

yeah your both as bad as each other, its really not that complicated

smaller plenum increases throttle response (throttle closer to valve's/ports)
larger plenum better for top end but sacrifices throttle response

personally i prefer throttle response

oh and please would neither of you argue with me, because i just dont care...

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'85 190, unrego'd (prospect track car)
'87 190e, manual (kinda rare in australia)
'89 260e

This is my tb in action. Car is AMG c36 1995 hfm
Mercedes M104 electronic throttle actuator - YouTube

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Jay,
-----------------
-1995 Blue W202 C36 AMG (M) SOLD ;(
-1995 Black W140 S500 (Lady)
-1992 Black W124 E300 (Dima) (Ex-Mosselman
Twin turbo Kit).
-1988 Black W124 300 E 4-Matic.(Nadeen)
-1983 Brown W126 500SEL.(Old Lady)(Sold)
-1981 Gold W123 280CE.(Dareen)(Sold)
http://www.youtube.com/user/jayrasheed

My TB with key in run posistion only moves halfway,with someone pressing pedal

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1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt

I love that some how an engine breaking means that you do not know what you are doing. I guess every time a top fuel motor blows or an f1 engine fails. That must be because some dumb kid was working on it. I have broken a few engines in my life some because I was dumb and some because it was time. The only time I really care is if I did not learn from it. Then it is just an inconvenience.

As far as the throttle body issue that this thread is about. The m104 has an abundance of throttle body diameter for its size. The intake is an odd one. I would love to see a computer simulated flow of the setup. The plenum in reality is the barrel of the plastic upper manifold. Although you do have to fill the lower section from a full vacuum. Initial throttle response is probably hurt a little from this. But my understanding is that this is probably a resonance design on the lower half also. If you were to measure out the total length down to the y.
It would be interesting to see the power graph of the engine if you put dual throttle bodies on at the upper plenum.
Anyways as far as the throttle opening all the way with the key on and the engine off I would not worry. Depending on the setup it may or may not. I think asr cars do not. 1999 is me injection and I know they do not. Me opens the throttle by a torque calculation. On most cars it does not open all the way until higher engine speeds were it is necessary.

Thanks Whipple.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran, deutschland deutschland uber alles uber alles in der welt

Bigger throttle body increses throttle response (more air for less foot movement) but reduces control (you go from 0 to 100% air needed with less pedal travel). Bigger TB does not necessarily mean more power. A bigger TB can reach 100% of needed air at only 80% aperture for example.

The way to know is by measuring pressure in the manifold. On a NA engine, at WOT and redline rpm, pressure should be close to atmosphere (like 98 or 99%, the figure is somewhere on the net). If you are below that then the TB, or air filter, or air filter housing is a restriction. If not, fitting a bigger TB will increase throttle response, decrease control, and do nothing to max power.

My car is equippped with megasquirt so monitoring manifold air pressure is quite easy. This is a 5.0 euro M117 stock long block with a 4.5 intake manifold and a 65mm TB and AMG camshafts and solid lifters. Exhaust are tri-Ys and a reasonably good flowing exhaust line. Dyno result is 254 rwhp, which is equivalent to 300 hp at the crank according to a formula I found on the net.

I initially thought that the TB was going to be a restriction given that the 300 hp 5.6 M117s are equipped with a 70mm TB. But it is not, as MAP tells me I fill 99% at WOT and 6500 rpm. Something to consider is that smaller means more velocity which also helps filling the cylinders. I don't know the formulas, but there must be a relation between velocity vs TB diameter for max filling at play here.

I did read that the other day, which was opposite of what has been suggested, but I didn't understand how? I have noted both increasing & decreasing throttle response from a larger tb, was confusing.

This is why I'm not worried about AFR's with my build. I was just interested in how a larger tb would benefit boosting.

Um, this was one point I shoulda made earlier but didn't see reason for it. If folk are counting the runners as part of the plenum, this will be confusing. I always counted the plenum volume, minus the runners.

With the M103 intake manifold, it is a weird looking beast but I'm sure, has it's engineering purpose, knowing the German's. It has long runners to increase mid-torque & I guess it suffers down low range? It follows downwards from head quite markedly till' it reaches the plenum. Plenum itself is a weird bull-horn shape that dips up sharply each side.

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um.....why have men got nipples

Would it be possible with how the linkages are on the m103 to put a custom throttle body spacer in? I was wanting to do this with my two additional injectors tapped into it. Then run SS like RBYCC!
Kinda like (IIRC) some kits they make for Dodges. I think Kennebell does this. But is it a good idea for my m103 turbo?

Mabe give Ed (RBYCC) a pm

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um.....why have men got nipples