Throttle Body Spacer

This may sound like a stupid question, but, how does a throttle body spacer add more power? Does it let more air in the engine? Does it speed up the air going in?

Has anybody made their own spacer? What did you make it out of and how did you make it? How thick did you make it?

Thanks,
William Crawley

reson46 said:

This may sound like a stupid question, but, how does a throttle body spacer add more power? Does it let more air in the engine? Does it speed up the air going in?

Has anybody made their own spacer? What did you make it out of and how did you make it? How thick did you make it?

Thanks,
William Crawley

Click to expand...

Do they add more power? Depends on who you talk to. It doesn't let more air in but can help to increase the velocity.
There are several threads that have addressed this topic, as well as throttle body boring to increase volume of air delivered. Used in tandem, you may see some gains in power. Try a search. Beware...... snake oil comes in many different packages.
If you want a real power increase, try a cam and header.
YOMV

It doesn't "add" power. It moves the peak of your HP/Torque curve down a bit in the RPM range by increasing plenum volume.

Not really noticeable, aside from a bit better throttle response.

I noticed an increase in power after putting mine in. Nothing scientific, but it felt slightly more powerful. I also calculate my mileage every time I gas up by subtracting the mileage from the previous fillup from the current mileage and then dividing by the # of gallons I just put in, and my gas mileage increased by .5 to 1 mpg after putting it on also.

Like Toz said, and I also saw a similar mpg increase as xj92 with the TB spacer. Definitely worthwhile considering it's a cheap and easy mod.
I had mine bored out to 62mm to match my bored TB and intake manifold inlet.
The helix "spinning the air" is a marketing gimmick. The spacer works by increasing plenum volume and adding length to the intake tract, thereby moving the HP/TQ peaks to slightly lower rpm and adding a little more torque at low/medium rpm. I estimate something like a 2hp/3lbft gain, with up to 5lbft gained in the 1000-2500rpm range. That's just about enough to be felt in the SOTP in 5th gear on the highway if you have the AX15. I also saw a 0.8mpg gain.
Throttle response is also slightly improved because of the added plenum volume.
_____________________________________________________________

Modified 1992 4.0 XJ Laredo UpCountry, 169k miles, AX15, NP231, D35c rear, D30 front
Estimated 240hp@5250rpm/280lbft@3500-4000rpm
1/[email protected], race weight 3490lb
Future mods: 4.6L stroker
Website: Jeep 4.0 performance
Webpages: Electric fan, IAT sensor relocation, Intake manifold heatshield, Oil temp. gauge install, Jeep 4.0 cam specs, Jeep engine dyno graphs, Automotive formulae, CTS resistor trick, MAP adjuster[/QUOTE]

I've got one... didn't notice any "seat of the pants" difference at all... mpg stayed lousy as usual...

Done a Cat Back too... felt a very minor "umph" increase... milage still sucks... 14mpg highway... 11mpg city... single digits off roading... :roll:

Thanks, that is exactly what I was looking for.

As for making a spacer, I thought I had heard someone mention that they had made their own. Has anyone done this, or am I just remembering wrong?

Thanks,
William Crawley

http://www.go.jeep-xj.info/HowtoTBspacer.htm

When I tried to find aluminum to do it myself they wanted $40 for the smallest piece that was 1" thick. I'm not experienced with buying metal different places so maybe they were just expensive, but I said forget it and paid $50 and just bought one online.