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Discussion Starter · #1 ·
Help me understand something. It seems to me the only way to get more air into the intake manifold is to decrease the constriction; increase diameter of the TB at the blade-a true bore TB. Ported TB's don't do that nor do TB spacers.
The "venturi effect" in airflow(as opposed to liquids) argues that speeding the air through the TB increases power down low(Airaid TB spacer is 77mmon a stock 80mm TB). However, the venturi effect states there is a pressure drop when speeding air through a constriction on the backside of the constriction(into the intake manifold). This is measured by the MAP(before TB and after TB).
Now, it makes sense that speeding air into the intake and by extension into the cylinders jams more air into the cylinder-a ram air effect. But, doesn't the pressure drop negate the argued venturi effect. I need someone to straiten me out on this.
Also, Janittie Racing demonstrated that a Hellcat TB on a 392 increased down low torque (15 ftlbs) and minor effect on HP(2 hp, which falls within +/-). Am I confusing HP effects with torque effects on my previous statements? know this is very pedantic, but, curious mind wants to know.
 

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I am by no means an expert on this and my curiosity arose after getting actual performance results measured by timed runs of 0 ~ 60, and then studying how and what in the design, gave the improved results to better understand what was actually happening. I do know that the venturi effect pressure drop when seeming to be a bad thing is offset by the velocity increase, which was a negative when applied to a carburated system, but not to an independently fuel injected systems like our 5.7s. Why did a particular brand design of CAI show zero performance gain over another brand that did show performance gain, and it was obvious that the successful designs took advantage of the venturi effect.

Any CAI that takes advantage of the venturi effect is going to aid the throttle body in doing its job of being the engines air door and at idle the gains are totally irrelevant but when the engine accelerates and the airflow increases the venturi effect begins. If a system is optimized to take advantage of the venturi effect from the air filter to the throttle body there can be a substantial velocity increase at the backside side of the throttle body, which is the best a naturally aspirated engine needs to increase performance. As far as throttle bodies are concerned a long taper ported bore seems to be the best results as has been proven by TheFastMan, as he tapers from the most outer opening of the throttle body to the throttle plate opening, which aids in the venturi effect.

My goal in trying to understand this comes from simply trying one thing over the other and if it worked to increase performance keeping it installed on the car, if it didn't, remove and shelve and find what works. So I have obviously wasted money in my endeavors and have shelved parts to prove it, but what works, is on the car now. My 2 cents! Ry
 

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2011 SXT Canadian Built Challenger
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Spacers use to help older Engines how ever on Newer Engines because of the Electronic Control of the Air Metering its not worth the Money Spent.
On the Throttle Bodies that Injected both Air and Fuel it gave a boost to Air create a ram effect to both the Air and Fuel. On a Direct Fuel Injection the Air has further to go
to reach the point of Fuel going into the Engine thus leaning it out and the increased mixture is not equally adding the volume equally. To compensate for that then your
Car needs to be tuned to adjust the Air to Fuel Balance for most efficiency.

Same if your Port your TB just a Ported TB virtually does nothing for increased Air Flow. When you add more air vs fuel in any method your mixture is too lean and
affects the detonation of the Fuel. The PCM aka ECM is regulating the Air / Fuel mixture to a degree how ever its set to regulate the Fuel at a preset volume. So if factory
sets it for 75mm TB it means the Fuel is being fed at a rate for so much volume of fuel to air. Just slapping a new TB say an 80mm on doesn't increase the rate of Fuel from the PCM / ECM to match the increased Air Flow , the PCM / ECM is set to it still will go by stock input that was programmed.

Also since its a Balance of Air / Fuel to the Air Pump / ENGINE to make this all work Larger TB means Higher Volume Injectors, Increased Fuel Pressure to deliver that.
This then me ans to detonate it the Spark also has to be changed Coils and Plugs. Since the Degree of Spark will also have to be Adjusted to Detonate that Fuel. So this is why
many just bolt on things do virtually little to no change and in some cases loss of Power.

Without a PCM / ECM that allows compensation Tuning meaning Locked VS Unlocked your not gaining a thing how ever like a placebo if you believe the claims just based on
what it is or label says you will believe its the Magic Snake Oil it is. Yet a Chassis Dyno will tell you another story.

The Claims well its more responsive is it because of the Larger TB no its because its Electronics doesn't have the Lag in its circuitry.
 

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The Venturi Effect works in Carburetors because the venturis cause a drop in pressure where the fuel is squirted in and helps the fuel atomize in the airstream (due to the lower pressure). If you look at a Carb. the venturi is located in the center of the throttle bore air flows around them and through them at the same time. The Venturi is where the fuel is introduced into the the center of the air stream in the venturi (Not counting the Accelerator Squirters that help in transition from part to full throttle). I do not think the same principle applies to a minor taper in a throttle body.
 

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I dyno tested the fastman 84 mm TB on my 6.4 with stock tune. Results were +7 HP and zero TQ over stock. Both stock and TB runs had Hellcat lower air box installed.
That could have just been a "hiccup" or variant on the dyno. 1 run to the next with the car with no changes could do that.
 

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didn't see it, but wouldn't a tb spacer be better than a larger tb? unless there is no such thing as a tb spacer. oooh, a billion dollar idea.
 
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Very few things actually improve the 5.7s performance, unless it is tuned for them. I'm not talking about a canned tune either, but a refined tune through multiple data log runs.

didn't see it, but wouldn't a tb spacer be better than a larger tb? unless there is no such thing as a tb spacer. oooh, a billion dollar idea.
When I first started my upgrades I bought a throttle body spacer and never even installed it I'm looking at the box it came in on the shelf above my desk right now. :)

I guess it would make a nice paperweight.
 

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see, thats why i am a chef and not a mechanic. ha!
 
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You can’t look at venturi‘s and spacers the same way you could on older cars. They just don’t work the same. Mopar or No Car has it right in his post. Chrysler probably sized the TB for a lot of things, emissions, mpg, drive ability, and performance but bigger isn’t always better. If you do other work, ported heads and intake, headers, cam, better exhaust, then a bigger throttle body would help.
 

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Discussion Starter · #14 ·
Much appreciated, all.
 

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didn't see it, but wouldn't a tb spacer be better than a larger tb? unless there is no such thing as a tb spacer. oooh, a billion dollar idea.
The only use I know of for a TB spacer is to create a location for nitrous injection from a NOS system.
 

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From what I've seen and been told, a throttle body spacer isn't much more than snake oil. Made on the principle of a carb spacer, but not applied in the same way, it is therefore not generating the desired or anticipated effect. I've never purchased and tested one, but I couldn't imagine it doing anything.
 

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From what I've seen and been told, a throttle body spacer isn't much more than snake oil. Made on the principle of a carb spacer, but not applied in the same way, it is therefore not generating the desired or anticipated effect. I've never purchased and tested one, but I couldn't imagine it doing anything.
Yep but sure looks purty don't it... :) lol
 

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From what I've seen and been told, a throttle body spacer isn't much more than snake oil. Made on the principle of a carb spacer, but not applied in the same way, it is therefore not generating the desired or anticipated effect. I've never purchased and tested one, but I couldn't imagine it doing anything.
a Carb spacer works because they were wood or composite and insulated the carb from engine heat which would cause fuel in the bowls to percolate. There is no fuel in your throttle body so absolutely no reason to get one unless you think you will pick up .01 on your E.T. due to the the lighter wallet you will have, and you only get the weight savings if you buy it and do not install it.
 

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thanks, it makes better sense now. knew what they did for carbs, was just curious if it was the same for tb.
 

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In theory a carb spacer increases the plenum area also, they make some pretty tall ones. On my 70 Challenger it was suppose to have a carb spacer, kind of a rubber gasket like material. It was long gone when I bought it. I had a heck of a time with hot starts, the heat soak would boil the gas in the carb, I even had a carb fire once. When I found a factory spacer in a junk yard it helped a lot, and amazingly all the linkage fit better. So yes, the insulating qualities was a big part.
 
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