03-16-2010, 04:41 AM
Join Date: Aug 2008
The TB spacer works on our Jeeps about as much as huge STP stickers on your doors will. In fact, the stickers may even give better performance.
Just to explain "Why."
The spacer's principle is to swirl the fuel/air mixture mist after the fuel has been added to the intake stream. The added length also gives it more time to mix - at higher speeds. At lower speeds it can even do the opposite, allowing the fuel to precipitate back to larger droplets. Some spacer mfgr's even tell you it creates a "ram" effect - or it lengthens the plenum chamber like a hi-rise manifold (carbs.) If it did, the spacer would need to be at least 3 feet thick!
They do work slightly on carbs and Throttle Bodies that inject the fuel in the TB - they atomize the fuel a little better.
But - our Jeeps don't have fuel up there in the TB, it's injected right at the intake valve. By the time the swirling air gets down the intake past the bends it's no longer swirling. Nothing is gained. It's the same thing with the "Tornado" insert in the air inlet - they do nothing.
Now think about it - the bigger bore of the 4.0 on a 2.5, or even a bigger bore on a 4.0 TB will let in more air - but of course only when it needs it. The only time the stock TB does any restricting is at very high speeds - maybe. They could help a little at Wide Open Throttle but it also needs more fuel. Larger injectors may help that - maybe.
If you really want to spend your money shop around for matched injectors. Using those insures that all cylinders are giving the same amount of fuel. You wont have some cylinders slightly rich and others slightly lean. The increase may be measurable on a drag strip, but you still won't feel it.
But even then, the psychological placebo effect gives the best performance - along with those stickers.
The most effective way to gain "seat of the pants feel" is gearing. Lower gears will cause the engine to run a little faster into the higher power curve. But - there goes mileage.
Through the years Jeep has done lots of small things to increase HP - a little at a time.
It's a Jeep, if you want a race car buy something else.
It's no wonder the country is falling apart - stupidity abounds!