DIY Throttle Body Spacer

[FastPlastic]

Ok, so it's starting to warm up and I've been planning on making one of these. One question I have is would ABS plastic be safe to use? The melting point is much lower then nylon 221F as opposed to the nylons 420F. I ask because I have a bunch of left over 3/8" sheets that would work great for this if it won't melt.

I know engine temp in the Jeep sits around 209F. What kind of temps does the throttle body see?

[Smoove]

Originally Posted by FastPlastic

Ok, so it's starting to warm up and I've been planning on making one of these. One question I have is would ABS plastic be safe to use? The melting point is much lower then nylon 221F as opposed to the nylons 420F. I ask because I have a bunch of left over 3/8" sheets that would work great for this if it won't melt.

I know engine temp in the Jeep sits around 209F. What kind of temps does the throttle body see?

Sorry to dig up an old thread, but the spacer on my 96 old 4.0 ZJ made a slightly noticeable increase in horsepower (mostly getting on the highway or up hills). I also gained 1.2mpg lifetime (roughly 140k) after the installation over the baseline of the previous 65k. Mine was made out of aluminum, I took the gasket to a local machine shop and told them to make me one a little over 1" thick (no hood clearance beyond that). I needed longer bolts for the TB and the throttle cables, but I got those from a fellow jeeper.

After my success, a buddy with a 92 XJ made one out of wood, he saw very limited gains (and drove like an ass). He hasn't had any problems with burning in the last five years.

And I believe the intake manifold gets much hotter than 209*, simply because the exhaust header is directly underneath it.

[hansj3]

speaking of variable compression
The SVC Engine
Variable Compression Engine
as much as i hate them...saab... for personal reasons, they have always been decent with innovations. why it hasn't resurfaced is beyond me though.

oh and FastPlastic the 4.0 had a cool mod involving th intake manifold out of the 99+ wj's.
Swapping to a 2000 Inlet Manifold

[Smoove]

Originally Posted by hansj3

oh and FastPlastic the 4.0 had a cool mod involving th intake manifold out of the 99+ wj's.
Swapping to a 2000 Inlet Manifold

I swapped out the manifold and injectors on my ZJ from a 00 XJ, and I wouldn't recommend it. It wasn't a significant expenditure of time, becuase wrenching with friends allowed me to swap exhaust manifolds in under three hours, and the cash outlay wasn't bad ($150), but the gains were simply not there. It increased my 0-60 by .01s, my mpg by.2mpg (measured at 0, 500, 1000, 5000 miles) and no seat of the pants gain. The manifold was designed to use airflow more efficiently under 2000rpm's, and is suspected that it needs the matching head and internals to see the "15hp) gain.

YMMV

[hansj3]

should have left the stock injectors in there. unless you bumped the fuel rail pressure up to 49 lbs you are running the injectors with not enough pressure. 96-97 had the highest fuel flow rate in the 43.5lb range 23.5lbs the 93-95 had 22's and the wj's had 22.5. you end up with a 21lbs/hr injector that doesn't atomize as well

[Smoove]

A friend that owns a local shop suggested that, so I swapped them back out with the stockers for a few hundred miles (I think 350, it was eight years ago so I am not 100% on that) and my numbers went down a bit more than stock. I then swapped out to a new set of stock Ford 5.0l injectors. Same crappy numbers, but a nice, smooth idle.

Then I had the XJ injectors cleaned, reinstalled them and saw a slight performance bump with a slightly smoother idle.

Yet, when I helped another local jeeper out and installed one on his 95 XJ he saw some decent gains. He was also on 35's and running 4.11's with a manual trans, so who knows.

[hansj3]

thanks for your input. its nice to talk to someone who actually did the swap. i guess i will move that down on my list.
sorry for the tangent

[Koots]

Originally Posted by SlowMo

But there must be an optimum length, probably related to engine displacement and desired rpm. This sounds more complex than 'slap a 1/2" spacer in it and go!'... come to think of it, probably related to cam timing too b/c the valve opening and closing would set up the pressure pulses. Kind of like expansion pipes on 2-stroke motorcycles, no? (just on the intake side, and with valves...)

I'm also confused by the claims of lower RPM gains because this article Best Carb Spacer Cheap Horse Power - Popular Hot Rodding Magazine emphasizes the gains in the upper rev range (although there are some mid-range gains too) like Christ states, but I'm not an engine builder and I'm more than a bit rusty at all of this.

This leads me back to the use of a TB spacer as a thermal break rather than as a method of tuning the resonant frequency in the intake tract.

I know i'm late, but i did want to say that the pressure waves and intake pulses do play an important factor in power production. I'm not sure that a TB spacer would make much of a difference to it's acoustic frequency. Whether it's for better or worse. The true power comes from tuning the individual runners.

A TB spacer adds more plenum length, which has some noticeable benefit with the correct fuel injection setup (i mean the process by which fuel is added with the air, not the typical "fuel injection").

A TBI engine or any carb engine will see a benefit due to the location in which fuel is added. These have what are called a wet manifold design. It's because the fuel is added prior to the intake manifold and then to the heads. Combine a short travel, with a near 45 degree angle it hits when into the manifold itself, makes it less than ideal for fuel atomization.

Adding extra height gives the fuel more space and time to atomize and mix better with the air. It means that you get an efficient mixture for combustion and less issues with fuel puddling on the bottom of the intake. Using materials that absorb less heat adds to the benefit as well, keeping the fuel just a tad cooler helps with the efficiency as well.

Those vehicles with MPFI or any other sort of port fuel injection (dry manifold designs) will see little to no benefit with a spacer. Effectively just adding a few extra cubic centimeters of volume for air to occupy. If you see any gain at all, it will be minimal. It's basically like adding adding a large diameter fancy tailpipe to your exhaust. Basically just makes it a little longer, it won't do anything at all to aid in exhaust flow

If there is any gain to be had with dry manifold engines, it's either due to lower temps, terrible manifold runner angles, original TB gaskets were showing their age or miniscule plenum volume.

[Koots]

Originally Posted by Smoove

I swapped out the manifold and injectors on my ZJ from a 00 XJ, and I wouldn't recommend it. It wasn't a significant expenditure of time, becuase wrenching with friends allowed me to swap exhaust manifolds in under three hours, and the cash outlay wasn't bad ($150), but the gains were simply not there. It increased my 0-60 by .01s, my mpg by.2mpg (measured at 0, 500, 1000, 5000 miles) and no seat of the pants gain. The manifold was designed to use airflow more efficiently under 2000rpm's, and is suspected that it needs the matching head and internals to see the "15hp) gain.

YMMV

One thing that will help incredibly is additional plenum volume. Not sure what kind of options there are for jeeps though.

I had the worlds biggest POS manifold on my 97 Civic. It was so small, had the plenum volume of a hacky sack and tiny runners. I swapped the manifold out for one from a SOHC Vtec engine (D16Y8 96-2000 EX engine) which had short, wide runners and a huge plenum. It was cleaned up with a little bit of porting (don't worry, never ported too much) and with no other mods or changes.

The off the line power was more robust (still a little 1.6L 4cyl though) but the extra capacity in the manifold allowed a much deserved increase in the top end. Best thing to do is have a well matched system. A high flow exhaust won't do much, if the engine is still straining to suck air in through a straw. Keeping things within the same desired and tuned range (exhaust, intake, heads, etc.) allows maximum velocity, maximum scavenging effectiveness which increases the VE and efficciency of the engine.

Now isn't that what this site is all about

[ksa8907]

old thread, i know, but i ran across this and decided to add it here for people to see.

this is from another forum i used to visit often, nearly dead now.

Originally Posted by shadowvox6 View Post
Group,
Friday we had our Dyno Session with Axcelerated Motorsports...
I was impressed with what the Special did on the dyno.
The only significant changes were:
-Going back to a K&N FIPK from the JoeKD
-Intake Spacer

We picked up a phenomonal amounf ot torque...32 ft-lbs.
Went from a max of 184.26 ft/lbs in 2008...
...to 215.03 ft-lbs in 2009. (This is an all time record number here FWIW)
Horsepower was virtually unchanged...staying at 186 whp.

The torque curve is also flatter than without it.
The power band is also shifted downward at bit, much as we have seen in the Intake Spacer 1.0

This validates the Intake Spacer as a definete worth while mod to do.
I will post the dyno chart later.

full thread can be found here 2009 Dyno Pulls from Carlisle - DodgeIntrepid.Net Forums - Dodge Intrepid, Concorde, 300m and Eagle Vision chat