Throttle Body Spacers? - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 08-01-2006, 12:44 PM   #11
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Quote:
Originally Posted by Jack
Been wondering about this myself, more fo rmy Jeep since they're all over the pages of my Jeep catologs.
I've heard good things about them for Jeeps, especially the 4 bangers... if you haven't already gone here, check out www.jeepsunlimited.com for some more info. lots of good jeep guys there!

as far as for our cars, i'm not so sure it would make a big difference... only because we are 6 cyl and not 4cyl... 4 bangers need all the help they can get.
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Old 08-01-2006, 02:23 PM   #12
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I have done some reading about these, after seeing them questioned on JeepsUnlimited quite a bit without any good explinations other than they are useless on V8'*. I found the following on a local 4x4 forum:

Quote:
There are two types of TB spacers marketed; a straight-through spacer that is the same diameter of the intake manifold / TB and the “airraid” TB spacer that has little spirals cast in it to increase swirl.
The swirl-style spacer in stock form is junk – it is only worthwhile if those silly spirals are ground out before you use it. The swirl crap is useless on modern FI systems and robs power.
Now, a plain spacer can be a good thing to move your power down a little earlier in the RPM range – this is due to Heimholtz resonation. (I know all kinds of fancy words) Let me give you a simple (?) explanation of Heimholtz resonation:

Heimholtz resonation uses rarefaction waves to increase intake charge base on intake manifold geometry. Simple, eh? Think of it like this:
1. Intake valve closes and sends a “pressure wave” back towards the throttle body.
2. The wave bounces off the TB and comes rushing back towards the intake valve.
3. If the intake valve starts to open while this pressure wave is returning, the current intake charge is given a little help entering the cylinder. Think of it as “mini-supercharging” as the intake air gets a boost from this pressure wave.
Now, you can design your intake system to favor certain RPM ranges, but the rule of thumb is that longer intake runners with smaller diameters favor low-rpm power and short intake runners with larger diameter favor high RPM power.
So, a small TB spacer effectively lengthens your intake system, moving power a little bit lower in the RPM range. IMHO, for a 4.0L, this is a benefit.
From http://www.greatlakes4x4.com/showthread.php?t=1363
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Old 08-01-2006, 03:04 PM   #13
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Quote:
Originally Posted by Chinski
I have done some reading about these, after seeing them questioned on JeepsUnlimited quite a bit without any good explinations other than they are useless on V8'*. I found the following on a local 4x4 forum:

Quote:
There are two types of TB spacers marketed; a straight-through spacer that is the same diameter of the intake manifold / TB and the “airraid” TB spacer that has little spirals cast in it to increase swirl.
The swirl-style spacer in stock form is junk – it is only worthwhile if those silly spirals are ground out before you use it. The swirl crap is useless on modern FI systems and robs power.
Now, a plain spacer can be a good thing to move your power down a little earlier in the RPM range – this is due to Heimholtz resonation. (I know all kinds of fancy words) Let me give you a simple (?) explanation of Heimholtz resonation:

Heimholtz resonation uses rarefaction waves to increase intake charge base on intake manifold geometry. Simple, eh? Think of it like this:
1. Intake valve closes and sends a “pressure wave” back towards the throttle body.
2. The wave bounces off the TB and comes rushing back towards the intake valve.
3. If the intake valve starts to open while this pressure wave is returning, the current intake charge is given a little help entering the cylinder. Think of it as “mini-supercharging” as the intake air gets a boost from this pressure wave.
Now, you can design your intake system to favor certain RPM ranges, but the rule of thumb is that longer intake runners with smaller diameters favor low-rpm power and short intake runners with larger diameter favor high RPM power.
So, a small TB spacer effectively lengthens your intake system, moving power a little bit lower in the RPM range. IMHO, for a 4.0L, this is a benefit.
From http://www.greatlakes4x4.com/showthread.php?t=1363
A little bit of knowledge is dangerous..
The guy doesn't even know how to spell Helmholtz..
His #2 is very wrong
The pulse generated from either the piston stopping at BDC or
the intake valve closing is NOT reflected at the TB. It is
reflected at the mouth of the intake runner.
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Old 08-01-2006, 03:49 PM   #14
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<edit>

ignore this here post... realized after posting that this situation was a lot simpler than I was thinking...
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Old 08-01-2006, 04:16 PM   #15
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Quote:
Originally Posted by 95naSTA
A little bit of knowledge is dangerous..
The guy doesn't even know how to spell Helmholtz..
His #2 is very wrong
The pulse generated from either the piston stopping at BDC or
the intake valve closing is NOT reflected at the TB. It is
reflected at the mouth of the intake runner.
Now I don't know much about the specific workings here...It was just the most complete explination I have come across so far. The guy has 10 yrs powertrain calibration experience so I figured it might be worth someting.

Anyway, to help me understand, why would the wave reflect off the mouth of the intake runner and not travel back to the TB and then be reflected? I guess I don't understand what is at the mouth of the runner to reflect the wave.
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Old 08-02-2006, 12:25 AM   #16
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Quote:
Originally Posted by Chinski
Quote:
Originally Posted by 95naSTA
A little bit of knowledge is dangerous..
The guy doesn't even know how to spell Helmholtz..
His #2 is very wrong
The pulse generated from either the piston stopping at BDC or
the intake valve closing is NOT reflected at the TB. It is
reflected at the mouth of the intake runner.
Now I don't know much about the specific workings here...It was just the most complete explination I have come across so far. The guy has 10 yrs powertrain calibration experience so I figured it might be worth someting.

Anyway, to help me understand, why would the wave reflect off the mouth of the intake runner and not travel back to the TB and then be reflected? I guess I don't understand what is at the mouth of the runner to reflect the wave.
Well first, why would the wave reflect off an open throttle body? That would be the same as saying the air reflects off that little air splitter in the entrance to the UIM.
And as for how resonance tuning works, a quick and dirty way of explaining it is here:
http://auto.howstuffworks.com/question517.htm
But if you're looking for a good SAE paper talking about the various methods of predicting runner lengths, read "Development and Validation of an Impedance Transfer Model for High Speed Engines."
Resonance effect on intake tuning is a huge topic. There are many methods/attempts at predicting when resonance will occur but none are extremely accurate. Generally people calculate to get close, then modify on a dyno.
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Old 08-02-2006, 09:34 AM   #17
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Thanks for the link. I get the concept, its sort of like tuning a (competition) sub box and the way short vs long tube headers work. I just might have to check that paper out. I knew I should have taken that ICE class...
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Old 08-02-2006, 11:02 AM   #18
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I thought that Helmholtz only pertained to intake runners.
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Old 08-02-2006, 05:31 PM   #19
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Quote:
Originally Posted by ChaseSmith
I thought that Helmholtz only pertained to intake runners.
IIRC you can also tune the intake pipe to resonate at a particular frequency.
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Old 08-03-2006, 09:41 AM   #20
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Quote:
Originally Posted by Chinski
Thanks for the link. I get the concept, its sort of like tuning a (competition) sub box and the way short vs long tube headers work. I just might have to check that paper out. I knew I should have taken that ICE class...
get the right book and dig in... my ICE class wasn't worth the time/money spent because of a lousy prof... which was a shame, as I was looking forward to the class... it had such potential. The first day of class we tore down an LN3 to get everyone familiar with the components in an engine...

But it went downhill from there awfully quick.

On the plus side, the book is awesome, and I've learned more from just reading through that than just about anything else. Lemme see if I can remember what book we used...

<edit> I think this is the book we used... not sure if there'* a more updated version available or not...

http://www.amazon.com/gp/product/007...e=UTF8&*=books
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