find for autometer users

[pdiggitydogg]

Slow Autometer Boost Gauge Fix (http://www.scoobymods.com/forums/showthread.php?threadid=210&highlight=boost+gauge)

Seems like a good fix if they work as slow as I hear...

for the lazy:
http://www.importcars.net/subaru/gauge2.jpg

[thermal]

He he he he...that is awesome dude. I actually did that a while back by accident since my plastic/nylon tubing got smashed.

[pdiggitydogg]

so are they really slow with the standard line?

[thermal]

Honestly, autometer boost gauges are not very realiable. Some reacts quick and some are slow. When I heard about people dogging out the autometer gauges, I conducted an experiment when my gauges got stolen from my car. I needed to get another gauge anyway. This is using the standard tube that came with the gauge. This is what I did with my MBC set at 6 psi:

Autometer Boost gauge #1:
Bought it from Pepboys.
-installed it
-boosted
-observed
-took readings

Findings: After driving my car a few times, I was not happy with the readings. The needle was too slow and reads slighlty above 0 when the motor is not running and displays 5 psi when I was supposed to be boosting 6 psi.

Returned the gauge to Pepboys. The previous boost gauge I had (that got stolen) reacted way quicker. I assumed that the new one was just bad and convinced Pepboys to get me another one.

Autometer Boost gauge #2:
-Repeated the same steps

Findings: With the motor off, the gauge reads slightly above 0 and boosted 7 psi. The gauge reacted quicker than boost gauge #1. Did a few runs to make sure.

I went to a different Pepboys and told them that the gauge does not work properly. They gave me another one

Autometer Boost gauge #3:
-Repeated steps

Findings: Reacted just as quick as boost gauge #2. Boosted reading at around 5 psi and slightly above 0 witht the motor not running.

Conclusion: Being in the Navy has some privileges. My buddy hooked up the gauge to one of our calibration tester. It shows that gauge #3 is off by .5 psi after readings past 12 psi on the plus side. On the negative side, 1 in'hg is off all the way. It's not too bad. That is really almost unrecognizable when monitoring an analog gauge. I think it's just that the bellows material Autometer use is not consistent but will still do it's job. My Teg will not posses this boost gauge tho. I have a GReddy boost gauge and a GReddy A/F ratio gauge for it. Not installed yet tho.

As far as the reaction time of 2 different tubing, I didnt see the difference, I think maybe it was because I was boosting in such as low level. I would think that the stock plastic tubing should react faster with Bernouli's principle of convergent-divergent process. Less tubing diameter means less space/area to fill, so it should increase velocity.........

[pdiggitydogg]

Interesting...well I had heard that they really didnt work too well and I was actually hoping to find a used set of orange HKS's...but no go so far
Looks like I'll shell out for some omori's (my things need to match...)

Good thing my boost is way off

Good write up

[hooohaa2]

I am about to install my boost guage (autometer) and I am going to use this method.

As far as Bernouli's principle is concerned, I don't know... but I do know that it is extremely hard to blow through that thin nylon tubing. It makes sense to me that using wider ID tubing would help out boost guage performance, it breathes with less resistance. If there is a bellows to fill inside the boost guage (if that is how it works) then there would be a delay when using nylon tubing, since a lot of air has to flow through that extremely thin tube.

[AzCivic]

it may be harder to blow through but the air coming out the thin tube is traveling at a greater velocity than the air coming out the wider tube.

[thermal]

^:yes:

[hooohaa2]

I just installed my boost guage with this method, and it is quick responding just like the video in that link.

I don't understand why this nylon tubing would be any different than injector size. With the same pressure behind them, stock 390's will flow less than 550's, just as it would take longer to fill extra volume (such as a bellows in a boost gauge... I have never taken apart a boost gauge so I don't know if there is a large volume to fill inside or not) with a thin nylon tube than it would with a wider ID hose. If there were no volume to fill then yeah, the air would flow at a higher velocity, and the nylon would work just as well as wider ID hose. What I am saying makes sense to me, if I am wrong, then please explain it better for me. Am I misunderstanding the "bellows" of a boost gauge?

[thermal]

Bellows is really just a minute effect to the physics of this. Bernouli's principle is simple. Take a garden hose for instance. Turn the water on. Place your finger on the tip of it. As the area gets smaller, velocity increases. Velocity is really nothing but speed rate of the medium.

Substitute:
Garden Hose= Intake manifold
Tubing= is where your finger is at on the tip of the hose

Apply this process on the basics of engine dynamics. The intake manifold obviously posseses greater area than the tubing. As the air travels (with the IM under the pressure state), it will travel to a smaller area of constriction faster than it will on a larger area, on this case, larger tubing. However, there are still some factors to consider on this smaller area to improve velocity. Here are some:
1) Distance of travel (Length of tubing)
2) Frictional affect (How rough the passages).
3) Directional (Bends of the tubing). Smooth bends are ideal. Avoid sudden turns.

To elaborate on the bellows:
Inside almost any pressure or vacuum gauges is a hollowcoil made of a typical bellows material for sensitivity and some strength. The needle is positioned in the middle of the coil. As pressure is applied to the coil, the reaction is for the coil (bellows) to expand. The needle then moves to the + side. Vice happens under the vacuum state.

But really, these are all getting way too deep for the subject. My final thought on this subject is to simply shortened the length of the tube, whether a bigger tube or not.... and avoid leaks of course. :)

[pdiggitydogg]

woa we got physics goin on 'round here
this is probably one of the most scientifically sound posts ive read in a long time

[thermal]

He he he^