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Throttle Body Spacer
Port injection

The TB spacer is meant to keep the throttlebody cooler, by seperating it from the manifold using a phenolic material instead of metal. The misconception is that by adding space behind the TB, you are going to get more torque.


The lowered temperature is fine, and is worthwhile (see TB coolant bypass), but the cost of a spacer and the remaining intake manifold temperature doesn't do a whole lot on its own. The performance myth with this device is that it allows more air in, or that it lengthens the runners, or anything else along these lines.


The torque curve is dependent on a lot of things, but for the TB related part, its actually not even related. The plenum, while connected to the runners, aren't part of the runner equation. You would have to lengthen the runners themselves to do anything. Actually, even this doesn't seem to work from testing on a 3100 with 1" spacers between the lower and upper intake. You would likely have to change the volume of the runners much more than just extending them will do.


Regardless, this has nothing to do with the plenum. The plenum volume is important to performance and the RPM range of the powerband, but the TB spacer isn't going to have any effect on this because its volume is minimal.


The only real value to a Throttle Body spacer is for a NOS setup. You can drill a hold in the spacer for a NOS injector. It is easier to work with a seperate piece for the nitrous injector, and it is easier to return the car to normal later.

TBI, Carb

Unlike the port injected manifolds, a spacer that goes under the carb or throttlebody will help out for performance. The extra space will help the air fuel mixture atomize, which will burn more efficiently. The myth part is for the port injected motors only.


by 2FastChevy on Fri, 11/14/2008 - 14:07
I have a throttle spacer kit from Airaid on my 99 chev lumina and I find it does help with overall throttle responce and contributes to a reduced amount of peddle effort even if it doesnt add alot of boost to the top end hp.

When the intake was bone stock at certain driving speeds I would have to put my foot to the floor to get the tranny to downshift and give me more power, even with a custom ram air which i installed didnt change the pedal effort much but there was a noticable gain in power.

The ram air causes much more of a dramatic responce with the throttle spacer in my experiences. Speeds where it would previously need full throttle to down shift I now only have to use about half the pedal effort to get the same result and instead of having to hold the pedal almost 1/4 of the way down to hold my speed at 120 kph(75 mph approx) i now just need to hold it at a light press as if i was doing city speeds. Not only that the motor honestly pulls noticably harder with the set up i have on it, with a light tap of the pedal the motor revs as if my foot's sunk into the accelerator and prior to the modifications I would need close to a 1/4 pedal depress to get the motor to light up and scream the way it does. My friend has a
02 GT Grand Prix that car has a 3.8 and the past few times we lined our cars up I actually got the better of him and began to pull away..When my motor was bone stock he would have a feild day with me pulling away with ease and since its not been the case and his car is in perfect working order too.

by IsaacHayes on Sat, 11/15/2008 - 00:29
I don't buy it. I bet if you did back to back tests with someone changing it when you came back out to drive to lunch you'd think it was still on... I had to do big mods that changed a drastic amount of the intake manifold design before I felt differences. I'm talking going from small port to almost double size large port, large plenum. Biggest change was 65mm TB at the end, which seemed to unleash more of the intake swap. I bet a 65mm on the stock intake manifolds would have just resulted in maxing out the air flow at 50% throttle.

by SappySE107 on Sat, 11/15/2008 - 00:46
Dyno it or back to back track runs would help. There is no way that ram air and a TB spacer makes it go from full throttle to half throttle as the same power output.

by 2FastChevy on Sat, 11/15/2008 - 15:01
Quote:
Originally Posted by SappySE107 View Post
Dyno it or back to back track runs would help. There is no way that ram air and a TB spacer "makes it go from full throttle to half throttle as the same power output".
What exactly are you trying to say here? Doesnt cooler/ more dense air being injested to the motor make the rpms increase? All I said was my overall pedal effort to get it up to speed is reduced overall and that It feels like the motor is pulling harder compared to the bone stock intake system, which we all know is quite restrictive. With the stock intake on its like the motors breathing through a vacuum attachment for the cracks in couches or the corners of stairs...

by 2FastChevy on Sat, 11/15/2008 - 15:21
Quote:
Originally Posted by IsaacHayes View Post
I don't buy it. I bet if you did back to back tests with someone changing it when you came back out to drive to lunch you'd think it was still on... I had to do big mods that changed a drastic amount of the intake manifold design before I felt differences. I'm talking going from small port to almost double size large port, large plenum. Biggest change was 65mm TB at the end, which seemed to unleash more of the intake swap. I bet a 65mm on the stock intake manifolds would have just resulted in maxing out the air flow at 50% throttle.
I'm not trying to start any arguments here but you put on a larger throttle body so that its greater volume would help it injest more air no? Well wouldn't putting a spacer behind your throttle body increase the overall volume of the unit and have a similar result in helping the motor to take more air in?

by silvergtjrad on Sat, 11/15/2008 - 15:38
A TB spacer is also going to change the volume of the plenum as well, which will move the powerband a bit.

by IsaacHayes on Sat, 11/15/2008 - 23:16
Larger TB = larger diameter for air to come into. A spacer is the same diameter as stock, and I highly doubt the .5 - 1" thickness is adding any measureable amount of plenum space. I swapped to a 3500 plenum which has a TON more space than the stock plenum. You have to do something like that to notice anything. If you really got the gains you think from the spacer, I should have insane gains from the large plenum I put on my car......

by SappySE107 on Sun, 11/16/2008 - 00:27
Exactly, a spacer doesn't increase airflow. Send me your spacer and I will put it on the bench and show you the results. The volume isn't even worth talking about. Plenum spacers give you more and don't do what you are talking about.

by bszopi on Sun, 11/16/2008 - 02:52
Pedal effort may be due to a possible change in the placement of the throttle linkage due to the spacer... But yeah, the difference in volume is going to be negligible. Like said previously, even if the spacer was 1" thick, and it was larger than the TB size (lets say 65mm as an example =>2.56"), the volume you are gaining is 5.14in^3. That is less than the volume of a SINGLE runner on just the plenum (so not including the lower manifold). Split that across all of the cylinders and you are gaining basically insignificant volume in the plenum overall.

by betterthanyou on Mon, 11/17/2008 - 03:20
I tend to agree. Spacers don't work on port injected vehicles. However on Carb and TBI vehicles there are proven gains. Sometimes over 20 horsepower. But in these cases plenum size is very small to begin with. The reason being the manifold is wet and a large plenum volume would allow the fuel to fall out of the air. Also a carb needs a very strong vacuum signal and air velocity to function. An overly large plenum defeats both these things so it really wouldn't work good in low speed operation. So plenum area is always small. Adding a 1" spacer makes a good difference in this case. Also every time a spacer is added the torque curve moves up the RPM range.

 
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