DIY Throttle Body Spacer

[mobilerik]

Thanks, Christ! That was a pretty good description of how ported speakers work. So I'll take some time to think on that helpful analogy and maybe revisit it later.

Meanwhile, though I think I get how the intake acoustics contribute to power, and I see the reasonableness of the argument that "more power with the same amount of fuel equals the same power with less fuel", I get stuck on a counter-argument: If you're getting your power increase by cramming more air in, then you're also cramming more fuel in. So your power-per-unit-fuel efficiency should be the same.

But it's starting to make sense now. This is how I'm explaining it to myself:

The air does double-duty in driving the engine -- 1. chemistry for combustion, and 2. mechanical compliance (spring action). Assuming the same volumes of air, and therefore the same fuel usage, the spring action is the variable that can either add free torque if the intake resonance is in phase with the combust cycle, or subtract torque if it's out of phase. So by tuning your intake to your preferred RPM, you can get free torque on the same amount of fuel.

I guess what was throwing me was the idea of ramming more air into the cylinder, which if I'm understanding right, is a misinterpretation. You're really pressurizing the same mass of air, ie. less volume, not more. So since stoich is mass-to-mass, you use the same amount of fuel to get the torque-bonus (or torque-loss, as the case may be).

[Christ]

You got exactly what I understand to be the principal behind harmonics and intake systems, and exactly what I was trying to convey. With a bonus audiophile analogy. Damn - you really worked me on this one. :P

[Christ]

FastPlastic - You lucky summuna.... here is your throttle body gasket:

[FastPlastic]

Originally Posted by Christ

FastPlastic - You lucky summuna.... here is your throttle body gasket:

Yup. Should be about to knock that out in 15-20min. Probably spend more time looking for longer bolts if I need them.

Coyote X - Did you end up replacing the mounting bolts?

[Christ]

You probably should use longer bolts if you plan on making more than 1mm of spacer. The typical flange is only 1/4 of engagement, and most OEM's use the "correct" length bolt for many things these days.

Also - you should have studs... most do, iirc.

[XVTer]

This is definitely a simple mod that I think I will try.

[FastPlastic]

Anyone know how you measure the intake manifold? Is it just from the throttle body to the engine?

I'm trying to get an idea of how tall this should be. I've seen several on the market for the Jeeps that look like there about 1". I guess another question I have is could you make it too tall? I would imagine the hood would be some what of the limit but when it comes to the harmonics you would just drop down a multiple or two depending on length. Then again I saw 35" was the optimum at 2100rpm. So I'm guessing that would be difficult to even remotely come near that with this spacer.

[getnpsi]

Are you guys only adding a spacer at the throttle body on mpfi, or adding a spacer between the head and the intake plenum? the latter is a part that is offered in the aftermarket on my dodge and other performance oriented cars.

[tkelly27]

Hello everyone, this is my first post. I did this with my 1989 plymouth horizon with a 2.2 TBI 5 speed.

If you want to temporarily try it out, you can go to a junkyard and find gaskets for your car. Stack 5 or 6 together and you'll have a pretty sizable spacer. Thankfully the ones in the dodge 2.2 are 1/8" so i only tried two.

I found it added to the low end. I have no idea what it did for mileage, those were nearing the end of my teenage years so I was more concerned with how many gears I could keep the tires smoking (1st-3rd if you were wondering). I did get it from ~14mpg to just over 30 (still driving like a jerk) with new plugs with a wider gap, oil change, timing advanced 5*, TB spacer, and a better air filter. On a 290k engine, god knows which one of those helped : /

[fud2468]

This discussion reminds me of the Dodge-Plymouth SonoRamic intake setup used in the early 60's on big-block V-8 cars. IIRC, the California Highway Patrol had some of these. The intake runners in racing models were 15" long, in others (CHP) were 30" long, a 4-BBL carb on one side of the engine bay feeding the bank on the opposite side, and vice versa.
The carbs had to be set to run rich through most of the power band to avoid running too lean at the RPMs where the ram effect kicked in--not very good for FE .
Ray Mac