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Low vacuum at idle - normal?
#1

I've worked on engines for a long time, but this one has me stumped.  This is going to get technical - I need some expert help.  First some background.

I just rebuilt my 2.3L Turbo engine.  Bottom end is stock.  I only upgraded the cam and injectors, valves are stock diameter.  EGR is blocked off.  

Cam specs:
.465 valve lift
I & E are 220 deg @.050
116 deg LSA
Cam is currently installed ~ 3 deg retarded (2 deg on gear + 1 deg that I lost having the head milled).


Engine would not idle under 2000 rpm - it would just die.  Then I remembered I changed the stock 35# injectors to 42# Bosch injectors.  Hooked up the AFR gauge - AFR was pig rich (10.5:1) at idle. Once I lowered the base fuel pressure to 30 psi, it now idles at 14.5:1, and it idles smoothly now.

Now it still has low vacuum at idle, but it is a smooth idle at 900-1000 rpm, not like before, and not what you would expect with a vacuum leak.  I have checked the obvious, looked for leaks. Hooked up fuel pressure and vacuum gauges, here is what I measured -


With Base Fuel Pressure set to 30psi on Kirban FPR (hose disconnected),  Engine running parked (no load)
RPM                      1000       2000       3000       3100       5000
Vacuum (in)            5            12           13-14      14           14     
Fuel Press (psi)      27           25           24            23           23      (vacuum hose connected)                                                     
A/F Ratio              14.5        14.5        14.5        12.5        11.5    (linear change 3100-5000 rpm)

MY QUESTIONS ARE:

1) Above 3000 rpm, you can see that the A/F ratio drops smoothly (gets richer) as I increase rpm from 3100 to 5000.  IS THIS NORMAL? 
Do I need a new Adjustable FPR?

2) Why is vacuum so low at idle, and is 5 inches ever considered to be OK?

Thanks for the HELP!
87 Gold TC 5spd, CAI, Bobs log, 3”down->duals, UPR shiftr, CHE/MM/Tokiko susp, Delta custom cam, Racer Walsh valvetrain, BPV, 18psi, all options
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#2

Have you tried moving the cam timing around?
What do u get when u feed booost to a dinosaur???? Booostalotopuss.T for Turbo-S for Supercharged.
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#3

(10-01-2020, 05:34 AM)Fast88 Wrote:  [1] .....is 5 inches (vacuum @ idle) ever considered to be OK?

[2] Cam is currently installed ~ 3 deg retarded (2 deg on gear + 1 deg that I lost having the head milled).
.
[1] NO!

[2] I wuz wrong once B4, BUT......your description sounds as tho you simply bolted the vernier/adjustable cam sprocket onto yer cam and ASSumed that it was 2° retarded because the pointer said so. BTW.....in spite of milling the head, you don't automatically "lose" or retard cam timing unless you're using a stock cam sprocket doesn't provide a way to compensate.

A properly set up adj cam sprocket should first be "zeroed"/base-lined, using either dial indicators or an E-bar.....against a VERIFIED. "true"  TDC mark on the crank. THEN, you can move the cam to a retarded or advanced position - using the vernier markings on the sprocket - and be confident that its' position relative to the crank is what's indicated by the scale/pointer.

IMHO......"zeroing" an adjustable cam sprocket should be done thusly:
  1. Establish "true" TDC on the crank pulley/balancer = LINK
  2. Set the crank at TDC and level an "E-bar" (purchased or homemade) across the noses of the cam on the #1 cylinder. 
  3. Install the t/belt and adjustable cam sprocket with the adjustment set to "zero" (this usually puts the locking bolts midway/centered in their adjustment "slots"). Note that doing so will probably necessitate rotating the cam & sprocket slightly CW or CCW.
  4. Next, loosen the adjustment screws/bolts on the cam sprocket and rotate only the cam & sprocket hub (not the outer sprocket "shell" having the teeth) until the E-bar is once again leveled/zeroed.....then re-tighten/lock the adjustment bolts on the cam sprocket. Note that - depending upon the brand/style of adjustable cam sprocket - moving the inner hub independently from the outer "toothed" shell MAY .require loosening the center sprocket-mounting bolt.
  5. Now, rotate the motor thru two revolutions (CW from the front) until the crank pointer is once again indicating TDC and re-check to make sure the E-bar can be positioned level (ends equidistant from the v/cov rails) across the #1 cam noses. 
  6. If so.......re-mark the pointer/"tick mark" on yer cam sprocket to align with the "zero" on the Vernier scale and you're done. 
Also, don't forget that - altho many adj cam sprockets are marked in "crank .degrees" - if it/they are marked in cam degrees......then 2° is really 4°.  <shrug>
Placerville, California
(former)  '78 2.3T Courier w/blow-thru carb ~ (current)  '87 2.3T Ranger w/PiMP’d EFI
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#4

It should get richer with RPM, yes, especially when boost is present.

I agree that it sounds like cam timing isn't where you think it is. It's also a very common problem (getting cam timing correct, particularly with aftermarket cams and cam gears).
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|->PiMPxs & PiMPx ECU\'s<-| SVOx3, Turbo 06 GT
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#5

what timing differences was built into the cam?
xr,69 SC/Rambler clone,68 Rebel,71 XJ6 302v8powered, 66 Lincoln, Roadglide Turbo,FXR,Tundra SC,66 F100 460/c6
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#6

I'd check the following,

Cam timing
Ignition timing
Firing order
Compression test
Leak down test

Since you went with bigger injectors do you have a Pimp ECU for tuning ?
87 TC 5 speed at 203000 miles, BoPort Stage 3 Head, 2.1 cam, 50 trim Turbo, Stinger Pimp, 3" exhaust, upper and lower ported manifolds, FMIC, 66lb injectors, 255 pump, 20 psi at 4K, 25 psi at 4.5k. Temp is 93c and IAT is 50c. Great freeway flyer on pump 93 gas.
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#7

(10-02-2020, 09:07 AM)TurboRay Wrote:  [2] I wuz wrong once B4, BUT......your description sounds as tho you simply bolted the vernier/adjustable cam sprocket onto yer cam and ASSumed that it was 2° retarded because the pointer said so.

Yes that's what I did.

(10-02-2020, 09:07 AM)TurboRay Wrote:  Also, don't forget that - altho many adj cam sprockets are marked in "crank .degrees" - if it/they are marked in cam degrees......then 2° is really 4°. <shrug>

My sprocket is marked in cam degrees. So when I read that these turbo engines like having the cam retarded 4 deg, is that cam degrees or crank degrees?

Thanks for the ideas, I have not had a lot of time to do much on this yet.
87 Gold TC 5spd, CAI, Bobs log, 3”down->duals, UPR shiftr, CHE/MM/Tokiko susp, Delta custom cam, Racer Walsh valvetrain, BPV, 18psi, all options
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#8

.
What you've probably read is that the late Ford roller .cams (Ranger & Mustang) seem to work best in turboed Lima engines when retarded 4-6 crank degrees. This is done to defeat some of their excessive low-end grunt and extend the power a little higher in the RPM range.

Are you sure that your adj cam sprocket is marked in cam .degrees? If that's the case and you were to extrapolate the degree marks......"only" 360 of 'em would fit around the perimeter of the sprocket. <shrug>
Placerville, California
(former)  '78 2.3T Courier w/blow-thru carb ~ (current)  '87 2.3T Ranger w/PiMP’d EFI
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