what is A Vaccum ejector?

[ghandiface]

ok so i posted a thread a while back on my car that was over boosting. and to fix the problem i replaced a "vaccum ejector" with a oneway valve. it seemed to have fixed the problem. i just wanna know what its suposed to do and where i might find one. i wanna put this car back to original then once its running and driving perfectly i wanna do some work to it. btw the line that the ejector was on went from the intack to a diafram in the airbox that seems to be a blow off valve.. problem is its vaccum operated.. and its always open.. how do i fix this problem oh magicians of turbo dodge!!

[NAJ]

I just went thru this on Saturday helping a fellow TDer install a vacuum block on a 91 Daytona T-1.
The "vacuum ejector" as Chrysler calls it is just a vacuum "loop" with numerous outlets to controlled components.
On the Daytona it was loacted down by the turbo.
I am still trying to find out what the purpose of this is/was.
My best guess is that it was to save space and use less seperate vacuum line in the system.
We were unable to delete this section, although we did build a new one and ran the lines for the evap system directly off the TB and eliminated it from the "ejector" setup.
I will be at my Son's house tomorrow.
If he did not throw out the old lines I can take a pic of the "vacuum ejector" setup for you.

The compressor relief valve(BOV) in the airbox gets its vacuum/pressure source directly from the manifold on the backside where the main vacuum source to the brake booster is located.
The BOV is closed by pressure(boost) and opens from vacuum so when you are in boost and release the throttle vacuum opens the valve to relieve manifold pressure.

[CBMDennis]

ghandiface Could you post your vacuum diagram in this thread?

[NAJ]

1989 2.5L T-1



1990 2.5L T-1



1991 2.5L T-1

[CNH320]

The vacuum "ejector" tee is a venturi nozzle that creates vacuum on the "T" leg when in-boost. On our cars its used to create vacuum during boost operation for things like cruise control and canister purge when there is no manifold vacuum available. (For example if you were climbing a long grade into the mountains) If you take the hoses off the ejector tee, you'll notice that there are inserted nozzles on the inlet and outlet.

http://en.wikipedia.org/wiki/Venturi_effect

[bamman]

Here is an actual diagram of the vacuum ejector from a 1992 2.5L Turbo.



Here is what the numbers mean if you are really interested:
1 3580172 1 CAP
2 4549209 1 VALVE, Check
3 4104272 AR HOSE, Rubber 1/4" I.D. (serv. in 50 ft. roll)
4 4458155 1 CONNECTOR 1/4 x 3/16 x 1/4
5 4241846 3 TUBE, Formed
6 4275553 1 CONNECTOR, Y 3/8 x 3/8 x 3/8
7 4443178 AR HOSE, Rubber 3/8" I.D (serv. in 25 ft. spool)
8 4669013 2 EJECTOR, Vacuum ***
9 4275638 1 TEE 3/8 x 3/8 x 3/8
10 4201197 1 CONNECTOR 1/4 x 3/8

[NAJ]

That is what I was trying to find out.
But why is it only used 91/92 and why not just use one way check valves that were used in previous years?

[TheCanadian007]

Weird setup...

[6daytonas]

Quote:

Originally Posted by NAJ That is what I was trying to find out. But why is it only used 91/92 and why not just use one way check valves that were used in previous years?

Never had a Mitsu T-1, but after looking at the vac diagrams, this is very clever engineering by the Chryco folks. The use of check valves would not create an area of pressure differential, which is what is needed for the creation of a Venturi effect.

In a set-up like my TII car, the cruise function recovers in an abrupt, unrefined, manner once the vac system is exposed to boost. Since the cruise servo works off of vacuum only, and the brake booster has a finite ability to store vacuum, the servo can lose the ability to control vehicle speed until vacuum pressure builds back up in the brake booster (the primary vacuum source for most TII cars). Resuming a higher, saved, speed can be sluggish as the car wants to go into boost to do so; but under boost, the cruise servo doesn't see enough vacuum to actuate the throttle as aggressively as your right foot can. One way to alleviate this condition: install a vacuum reservoir downstream of a one-way check valve leading to the brake booster so that you effectively add a back-up vac source inline with the cruise servo.

An easier way is this nifty vacuum ejector arrangement, which effectively eliminates the need for a separate vacuum reservoir. Pretty slick. If you look at my modified diagram, and assuming you understand the Venturi effect which is a result of the Bernoulli Principle, then it is very easy to see how vacuum is created in the line to the cruise servo under boost. The Ejector is actually like a Venturi nozzle - if they labeled it as such in the first place, the concept would be more readily evident.

[NAJ]

So basically what you are saying is that without the vacuum ejector setup the only issue that may arise is no cruise at high mph if in boost for a prolonged period of time.

my RT has one that looks like that.i am not running it right now and the cruise control worked fine on the way back from wisconsin

[NAJ]

I still have his old one incase he wants it back.
He contacted me and told me the cruise worked fine on his way home and they did tell me they were cruising at 75 mph on the N.J. Turnpike on the way to my house so I am guessing they traveling the same going home.

[6daytonas]

Quote:

Originally Posted by NAJ So basically what you are saying is that without the vacuum ejector setup the only issue that may arise is no cruise at high mph if in boost for a prolonged period of time.

Kind of. Cruise will still work, but it will exhibit the typical TD lack of smooth, off-boost throttle tip in, if that makes sense. Coming out of boost, no/little vac in the brake booster leads to a slight delay for vac to build resulting in the unrefined cruise operation that typifies these cars. With the ejector in place, the pressure differential it creates should allow the cruise servo to operate the throttle more aggressively when in boost. This should allow faster and smoother response when resuming a higher set speed, i.e. ~ say you were cruising at 70 mph, hit some traffic, slow to 45 mph and then click resume. The trip back up to 70 mph should occur quicker and with more refinement than a car like my '88 which only uses a check valve to preserve vacuum when in boost.

Certainly not an essential component for cruise operation. Just an improvement in the area of refinement.

[NAJ]

Just so you know, I do not take anything at face value and I am a PITA(according to my family) because I always want to know...WHY?
I understand what you are saying but...
Why did they wait until 91 to add this?
Were they responding to consumer complaints?
If the system was so benificial to smoother cruise operation why was it not incorperated on the T-3?
Also why are they running canister purge and turbo lines off of the ejector?

[TheCanadian007]

Why? Because ChryCo engineers were smoking glue that day