best throttle body spacer

[ChandlerXJ]

Hey guys, i'm about to get a TBS but i'm not sure which ones work the best. the rusty's one seems nice , but i know there are better ones out there. my forum searches just popped up the fact that i should get it bored too. any input?

 

[sawhead]

why bother...save your money

 

[Talyn]

What year Xj?

 

[OT]

Hey guys, i'm about to get a TBS but i'm not sure which ones work the best. the rusty's one seems nice , but i know there are better ones out there. my forum searches just popped up the fact that i should get it bored too. any input?

That's like asking which brand toothpicks is best.
The difference with or without a TBS is not noticable enough to warrant a need to compare.

 

[Talyn]

That's like asking which brand toothpicks is best.
The difference with or without a TBS is not noticable enough to warrant a need to compare.

Just don't get one of those helix bore ones.. just get a flat wall one.

 

[balloo93]

Save your cash and have a machine shop bore your TB straight through to match the middle. the stock TB has a lower taper on it and if you get rid of that you will be MUCH happier with the results.

I put a 1" aluminum TBS on mine and noticed no difference at all. I knew it wouldn't, but I had to prove it for myself so that when I said it did nothing I could back it up!

 

[JONNYD]

Bore your TB, screw the spacer. Add it if you feel the need to try something, but I dont think it is worth the $$$. Your $$$ is better spent on an air tube and a cone filter. Realize that with the straight-thru TB you will get a slight whistle at certain throttle positions...sounds like a turbo spooling up.

I have a bored TB (60mm thru), 1.25" TB spacer (homebrew), rusty's air tube, and a 9" K&N. I bet I only got 1-2MPG from all mods. With 3.5" lift and 31's I get 16-17 around town and 18-20 on the highway at 70MPH.

 

[hjeepxj]

search ebay, they have them for HOs for like 20$ shipped.

 

[spyder47]

why bother the spacer were originally made for carbs to swirl the air after the carb to better atomize the fuel just dumped there. putting one on efi is completely unneccesary and often will result in a drop in performance b/c that swirl slows the speed of the aircharge thus lowering the CFM the motor actually gets the idea of swirling on efi is complete non-sense an injector atomizes the fuel better than any carb could hope to.

 

[Talyn]

Not all spacers have the Helix Bore. In that case the spacer is there for greater intake manifold volume.

 

[spyder47]

true i guess i left that out thanks for catchin that

 

[djblade311]

I purchased the PowerAid TBS. Put it on. Didnt feel much different. Did seem to have a slight improvement on torque but then again, I didnt have a dyno machine. I'm ready to sell it...

 

[atx xj]

Not all spacers have the Helix Bore. In that case the spacer is there for greater intake manifold volume.

intake manifold volume doesnt mean jack when ur stock TB is limited by intake capability at 58mm with that weird taper it does

 

[MaXJohnson]

intake manifold volume doesnt mean jack when ur stock TB is limited by intake capability at 58mm with that weird taper it does

that's interesting. I'm not aware of any formula for calculating intake plenum volume that uses throttle body flow rate as a factor. Maybe you could elaborate?

 

[Talyn]

intake manifold volume doesnt mean jack when ur stock TB is limited by intake capability at 58mm with that weird taper it does

If that is true, why did Jeep change the intake plenum to a larger one?

 

[5-90]

I'd be less worried about plenum volume than Helmholtz resonance - which can be used to "tune" your intake to achieve a slight supercharging effect due to the wave action caused by interruption of airflow by intake valve closing.

Considering we're working more for low-end power than anything else, I'd like to do some more research to see what I'd have to do to fit a long-runner manifold under the hood somewhere...

5-90

 

[MaXJohnson]

Helmholtz resonance is based on intake configuration on the atmospheric side of the throttle butterfly, whereas the throttle body spacer adds volume to the engine side of the butterfly.

 

[5-90]

Are you sure? As I understand it, Helmholtz resonance has to do with soundwave/pressure wave reflections between the intake valve and a tangible obstruction. This obstruction may be a plenum wall or the throttle valve, but as long as any bends in the intake runners are smooth, you can keep adding length until you get what you need to time your return pulses (as I recall, usually the third harmonic is used to minimise runner length and maximise "resonance boosting," for lack of a better term.)

Careful tuning of Helmholtz length can result in a VE approaching - or slightly over - 100%. Helmholtz resonance tuning ceases to be a factor with true forced induction (turbocharging/supercharging,) but there's no physical reason why it can't be applied then if you choose - probably with greater effect since you're working with greater fluid density (I may have to play with this idea someday...)

Honestly, I can't see why resonance tuning on the atmospheric side would have anything to do with VE increases - especially when you're working with reflected pressure waves. There isn't much of anything to create a useful pressure wave, and Helmholtz resonance is typically most effective at part throttle (at or near the torque peak of the engine combination - which is also where peak VE occurs.)

Or am I missing something?

5-90

 

[OT]

Are you sure? As I understand it, Helmholtz resonance has to do with soundwave/pressure wave reflections between the intake valve and a tangible obstruction. This obstruction may be a plenum wall or the throttle valve, but as long as any bends in the intake runners are smooth, you can keep adding length until you get what you need to time your return pulses (as I recall, usually the third harmonic is used to minimise runner length and maximise "resonance boosting," for lack of a better term.)

Careful tuning of Helmholtz length can result in a VE approaching - or slightly over - 100%. Helmholtz resonance tuning ceases to be a factor with true forced induction (turbocharging/supercharging,) but there's no physical reason why it can't be applied then if you choose - probably with greater effect since you're working with greater fluid density (I may have to play with this idea someday...)

Honestly, I can't see why resonance tuning on the atmospheric side would have anything to do with VE increases - especially when you're working with reflected pressure waves. There isn't much of anything to create a useful pressure wave, and Helmholtz resonance is typically most effective at part throttle (at or near the torque peak of the engine combination - which is also where peak VE occurs.)

Or am I missing something?

5-90

Okay, now I'm ready.
Continue........

 

[MaXJohnson]

Are you sure? As I understand it, Helmholtz resonance has to do with soundwave/pressure wave reflections between the intake valve and a tangible obstruction. This obstruction may be a plenum wall or the throttle valve, but as long as any bends in the intake runners are smooth, you can keep adding length until you get what you need to time your return pulses (as I recall, usually the third harmonic is used to minimise runner length and maximise "resonance boosting," for lack of a better term.)

Careful tuning of Helmholtz length can result in a VE approaching - or slightly over - 100%. Helmholtz resonance tuning ceases to be a factor with true forced induction (turbocharging/supercharging,) but there's no physical reason why it can't be applied then if you choose - probably with greater effect since you're working with greater fluid density (I may have to play with this idea someday...)

Honestly, I can't see why resonance tuning on the atmospheric side would have anything to do with VE increases - especially when you're working with reflected pressure waves. There isn't much of anything to create a useful pressure wave, and Helmholtz resonance is typically most effective at part throttle (at or near the torque peak of the engine combination - which is also where peak VE occurs.)

Or am I missing something?

5-90

Helmholtz theory can be applied to the intake runners in which case the reflective wave inverts at the point where the intake runner dumps into the plenum. Assuming the plenum is large enough (2 to 2 1/2 litres when applied to the Jeep 4.0), each runner can be considered on an individual basis. The plenum draws air through the throttle body and air tube. Helmholtz theory is separately applied to the length of this passage with the pressure wave inverting at the entry to the air box or the cone filter in the case of an aftermarket intake system.

Consider that factory engineers designed the cam, ports, intake runners, plenum, throttle body, air tube and air box as a tuned system to be most efficient in the heart of the power band. Changing a single component is this system is likely to do more harm than good.

In the 2500 to 3500 RPM band typical of the Jeep 4.0, don't expect Helmholtz tuning to achieve anywhere near 100% VE.