How much vacuum do you pull for efi? - Page 2 - Ford Bronco Forum
 8Likes
Reply
 
LinkBack Thread Tools Display Modes
post #21 of 33 (permalink) Old 04-29-2018, 11:54 AM
Registered User
 
fodder's Avatar
 
Join Date: Mar 2017
Location: PNW
Posts: 1,784
Bronco Info: '92 Custom
iTrader: (0)
Garage
Quote:
Originally Posted by AbandonedBronco View Post
75mph is right around 2100 RPMs in OD, which should be quite decent for mileage.
Without OD, you'd be more around 3200, which would definitely never be gas mileage friendly.
For my setup or for stock? 2100 RPM puts me at only ~60 mph.

I did re-verify that the OD button works as far as illumination, but those numbers make me wonder if OD itself is working. I've never had the Bronco up to 75 mph to see if 3200 RPM is in the right ballpark.

Quote:
It's possible, although looking at the tread pattern, they don't look that aggressive. More like the BFG tire, which is what I have, and it does quite well on the open road.
All the more odd that Grabbers have such low inflation specs, being considered pretty comparable to the BFG.

Quote:
If you do drive it that rarely, is gas mileage such an issue? Or are you just wanting to be sure everything's top notch?
Yes to the latter. I added the gauge cluster with factory tach, tranny temp gauge, and vacuum gauge to monitor the health of the system. The highway vacuum readings made me question if everything is running as it should.

I've kept mpg logs off and on for my vehicles for years (I'm always puzzled by people who lack the basic math skills to track that), but don't feel it'll be very useful in this case. I'd just like to not see the needle not drop 1/4 tank in a 70-80 mile highway trip. :) I think it actually drops slower on around-town driving.

'92 Bronco Build Thread - '95 MAF 5.0, H5 axle code, York OBA, 3G alt, custom jump seat console, flomaster steps/sliders.
http://www.supermotors.net/28006
fodder is online now  
Sponsored Links
Advertisement
 
post #22 of 33 (permalink) Old 04-29-2018, 02:34 PM
Big Six
 
AbandonedBronco's Avatar
 
Join Date: Feb 2006
Location: Boise, ID
Posts: 4,365
Bronco Info: 1985 300ci 6cyl. ZF 5 speed manual. 32" tires. DUI ignition. Holley Sniper EFI.
iTrader: (1)
I used this formula with your current setup:

Engine RPM = (Speed * Transmission Gear Ratio * Final Drive * 336) / Tire Diameter

(Assuming E4OD with 0.71:1 overdrive)
Engine RPM = (60 * 0.71 * 4.11 * 336) / 33
Engine RPM = 1782

If your overdrive isn't engaging:

Engine RPM = (60 * 1.00 * 4.11 * 336) / 33
Engine RPM = 2500


However, if you're at 2100 @ 60, then something isn't correct. It sounds like you have 3.55 gears:

Engine RPM = (60 * 1.00 * 3.55 * 336) / 33
Engine RPM = 2170

Are you sure you have 4.11s? It doesn't seem like you do.
Have you confirmed it by jacking it up and counting tire rotations to driveshaft rotations?

If you do have 3.55s, that might explain why your vacuum is low, since it has to work harder to turn your big tires over.
Stevo440 likes this.


May 2019 FOTM
March 2016 FOTM

1985 Eddie Bauer Bronco. High Performance 9.1:1 compression 300 (305) I6. Roller Rockers, DUI ignition, Holley Sniper EFI. ZF5. 32" BFG A/T KO2s. 3.55 8.8" rear.
1981 Bronco Custom (R.I.P.)
Supermotors Pics

Last edited by AbandonedBronco; 05-01-2018 at 08:46 PM.
AbandonedBronco is offline  
post #23 of 33 (permalink) Old 04-29-2018, 09:04 PM
Registered User
 
fodder's Avatar
 
Join Date: Mar 2017
Location: PNW
Posts: 1,784
Bronco Info: '92 Custom
iTrader: (0)
Garage
Quote:
Originally Posted by AbandonedBronco View Post
Are you sure you have 4.11s? It doesn't seem like you do.
Have you confirmed it by jacking it up and counting tire rotations to driveshaft rotations?

If you do have 3.55s, that might explain why your vacuum is low, since it has to work harder to turn your big tires over.
Great, one more thing to check... :) No wonder the H5 axle code is so elusive, even the trucks that have it don't have it!

It's possible a PO destroyed the original rear end and replaced it with an easier to source 3.55 setup...
Stevo440 likes this.

'92 Bronco Build Thread - '95 MAF 5.0, H5 axle code, York OBA, 3G alt, custom jump seat console, flomaster steps/sliders.
http://www.supermotors.net/28006
fodder is online now  
Sponsored Links
Advertisement
 
post #24 of 33 (permalink) Old 04-30-2018, 10:58 AM
Registered User
 
Stevo440's Avatar
 
Join Date: Feb 2009
Location: Woodstock, GA (Home)/Greensboro, NC (Work)
Posts: 591
Bronco Info: 95 5.8L XLT, Shorties, E4OD, Electric, Manual, KYB Quad Shocks , 31x10.5x15's, 289K miles
iTrader: (1)
Garage
Thanks, "AbandonedBronco", I didn't want to get involved with all the formulas and calculations, this is what I was eluding to, that the RPM's don't seem to match the Numbers presented as in OD of tires and Axle ratio and Overdrive ratio. Also is the Speedo calibrated correctly for the Tire OD and Axle Ratio??? It does not appear things are!!!
AbandonedBronco likes this.
Stevo440 is online now  
post #25 of 33 (permalink) Old 05-01-2018, 07:29 PM
Registered User
 
fodder's Avatar
 
Join Date: Mar 2017
Location: PNW
Posts: 1,784
Bronco Info: '92 Custom
iTrader: (0)
Garage
Okay, I freed up some time to delve into the various checks.

1) front brakes okay ... if there's any extra dragging on right wheel (the one with very uneven pad wear previously), it's pretty minor.

2) rear brakes okay ... both wheels spin freely.

3) open diff not LSD ... other wheel rotates easily in opposite direction (tested forward and back).

4) gear check: 20 spins of [right] rear wheel = exactly 41 spins of driveshaft = 4.1 gears. I followed the directions here.

That's puzzling. With the H5 axle code, I should have the 4.11 LSD. Test #3 gave me the sinking feeling of, "WTF did PO's do?", only to have #4 check out okay.

I picked up gear oil, friction modifier (which may be n/a now that I seem to not have the LSD), and an inspection cover gasket. Thoughts on whether I should go ahead and change the oil or wait until inspecting things further?

'92 Bronco Build Thread - '95 MAF 5.0, H5 axle code, York OBA, 3G alt, custom jump seat console, flomaster steps/sliders.
http://www.supermotors.net/28006
fodder is online now  
post #26 of 33 (permalink) Old 05-01-2018, 08:54 PM
Big Six
 
AbandonedBronco's Avatar
 
Join Date: Feb 2006
Location: Boise, ID
Posts: 4,365
Bronco Info: 1985 300ci 6cyl. ZF 5 speed manual. 32" tires. DUI ignition. Holley Sniper EFI.
iTrader: (1)
Nice going on checking everything over. If nothing else, you know it's in good order.
On the LSD, it's still possible you have one, but your clutches are shot and need replacement. When an LSD "wears out", it'll act like an open diff.

That's bizarre that you do indeed have 4.11s. I'm trying to think how things could be that off. Are you certain your speedometer is correct?
There isn't really any "wiggle room" when it comes to this stuff, since it's direct gear to gear all the way from the tire to the transmission to the engine.

There's always some irregularities like, your tires are never actually 33" exactly. With the weight of the vehicle, their diameter is more like 32 or 32.5, but it's not going to put things off that much.

At 2100 RPMs you really should be at least 70mph in overdrive.

I'm not sure past that.


May 2019 FOTM
March 2016 FOTM

1985 Eddie Bauer Bronco. High Performance 9.1:1 compression 300 (305) I6. Roller Rockers, DUI ignition, Holley Sniper EFI. ZF5. 32" BFG A/T KO2s. 3.55 8.8" rear.
1981 Bronco Custom (R.I.P.)
Supermotors Pics
AbandonedBronco is offline  
post #27 of 33 (permalink) Old 05-01-2018, 09:20 PM
Registered User
 
fodder's Avatar
 
Join Date: Mar 2017
Location: PNW
Posts: 1,784
Bronco Info: '92 Custom
iTrader: (0)
Garage
Quote:
Originally Posted by AbandonedBronco View Post
Nice going on checking everything over. If nothing else, you know it's in good order.
Yep, better to know what I'm dealing with, even if it isn't necessarily good news!

Quote:
On the LSD, it's still possible you have one, but your clutches are shot and need replacement. When an LSD "wears out", it'll act like an open diff.
That's good to know. That sounds like the likely scenario then. 25 years of unknown wear and tear / maintenance...

Quote:
That's bizarre that you do indeed have 4.11s. I'm trying to think how things could be that off. Are you certain your speedometer is correct?
I was just checking back to report on that, actually. I finished up that test, but haven't taken it out for a drive yet to see the difference.

My speedo was 967CAL (9.67 calibration constant), with "E 03" (English display, software rev 03) on the first screen. (I checked twice, no lockout count displayed as 3rd field). Oddly, toggling down w/ SELECT button jumped from 900 to 1000 and then counted up from there, flipping over to 500 after hitting 1100 I think. The climb from 500 to the 800s was a lot of button presses...

The revolutions per mile for my tires is 633, for a 8.55 calibration constant (as covered here). Despite my speedo not showing the lockout count, it did accept and save the change. The big question now is what speed 2100 RPM corresponds to, and whether there are noticeable driveability differences like some people have reported after the calibration.

'92 Bronco Build Thread - '95 MAF 5.0, H5 axle code, York OBA, 3G alt, custom jump seat console, flomaster steps/sliders.
http://www.supermotors.net/28006
fodder is online now  
post #28 of 33 (permalink) Old 05-02-2018, 10:06 AM
Registered User
 
Stevo440's Avatar
 
Join Date: Feb 2009
Location: Woodstock, GA (Home)/Greensboro, NC (Work)
Posts: 591
Bronco Info: 95 5.8L XLT, Shorties, E4OD, Electric, Manual, KYB Quad Shocks , 31x10.5x15's, 289K miles
iTrader: (1)
Garage
I hope the Speedo Re-calibration gets you in the ball park. So with your now known Rear-end ratio of (4.11) and a tire O.D. of 32.8 (unloaded from Tire Rack's Spec page) these can now be input into the above formula to get your ACTUAL RPM's at each speed in OD and with OD off. Good Luck
AbandonedBronco likes this.
Stevo440 is online now  
post #29 of 33 (permalink) Old 05-02-2018, 10:45 PM
Registered User
 
fodder's Avatar
 
Join Date: Mar 2017
Location: PNW
Posts: 1,784
Bronco Info: '92 Custom
iTrader: (0)
Garage
With the speedo calibration, the numbers do seem much more reasonable now.

55 mph = 1700 RPM, 15-18 " vacuum
60 mph = 1900 RPM, 13-14"
65 mph = 2000 RPM, 12"
70 mph = 2100 RPM, 11"

That was from a couple out-and-back jaunts on a mostly flat stretch of highway, but with too much traffic to be as consistent on the throttle as I would have liked, so it was hard to peg (and remember) super precise.

Observations: 1) The transmission seemed a bit more active in terms of shifting into the appropriate gear. It might just be that I was paying closer attention to it, though. 2) The fuel gauge hardly moved off of Full, whereas I would have expected it to drop by 1/8 of a tank for that amount of driving with multiple stops. Despite others reporting improvements in that area with the speedo calibration, it doesn't really make sense to me, so I'm not getting my hopes up just yet.

'92 Bronco Build Thread - '95 MAF 5.0, H5 axle code, York OBA, 3G alt, custom jump seat console, flomaster steps/sliders.
http://www.supermotors.net/28006
fodder is online now  
post #30 of 33 (permalink) Old 05-03-2018, 10:20 AM
Big Six
 
AbandonedBronco's Avatar
 
Join Date: Feb 2006
Location: Boise, ID
Posts: 4,365
Bronco Info: 1985 300ci 6cyl. ZF 5 speed manual. 32" tires. DUI ignition. Holley Sniper EFI.
iTrader: (1)
Those numbers look WAAAY better! Nice going.
Your transmission also shifts according to the RPMs vs what speed the computer thinks you're going. So, if your speedometer is off, it'll be shifting at the wrong times which'll make it feel sluggish. It also won't be properly staying in its power band.

Lastly, if before it said 2100 RPMs @ 60mph, and now it's 2100 @ 70mph, your tripometer was tacking up less miles than you were actually travelling. It was off by about 15%.

So, if your tripometer said you went 200 miles before, you actually went 233 miles. That'll throw your gas mileage calculations off, too.
If you used 16 gallons of gas, 200 / 16 = 12.5mpg whereas you really got 233 / 16 = 14.6mpg.

Keep track of a couple hundred miles and how your mileage is and let us know.
Stevo440 likes this.


May 2019 FOTM
March 2016 FOTM

1985 Eddie Bauer Bronco. High Performance 9.1:1 compression 300 (305) I6. Roller Rockers, DUI ignition, Holley Sniper EFI. ZF5. 32" BFG A/T KO2s. 3.55 8.8" rear.
1981 Bronco Custom (R.I.P.)
Supermotors Pics
AbandonedBronco is offline  
post #31 of 33 (permalink) Old 05-03-2018, 10:39 AM
Registered User
 
Stevo440's Avatar
 
Join Date: Feb 2009
Location: Woodstock, GA (Home)/Greensboro, NC (Work)
Posts: 591
Bronco Info: 95 5.8L XLT, Shorties, E4OD, Electric, Manual, KYB Quad Shocks , 31x10.5x15's, 289K miles
iTrader: (1)
Garage
"AbandonedBronco", I Concur most Absolutely!!!! Or in Udder Woids, Ditto!!!!

"fodder", You are now in a much better place. Keep checking the mileage you should definitely see a change (a more accurate mpg calculation) because you are now reading a more correct/accurate Speed vs Rpm and a more accurate number of miles traveled on your Odometer. As for the Vacuum reading that is another story that you can look into now having everything else straightened out. Good Luck!!!
AbandonedBronco likes this.
Stevo440 is online now  
post #32 of 33 (permalink) Old 05-03-2018, 12:39 PM
Registered User
 
fodder's Avatar
 
Join Date: Mar 2017
Location: PNW
Posts: 1,784
Bronco Info: '92 Custom
iTrader: (0)
Garage
It's odd the vacuum readings look so much better now, but that may be a byproduct of improved weather (perfect vs lousy) and road (interstate vs highway) conditions. If nothing else, this thread is now a good resource for anyone else wondering what sort of vacuum they should pull at highway speeds!

As for MPG's, keep in mind, I was going by the fuel gauge not by the odometer, so the non-calibrated speedo had no effect in that department. My fuel gauge appears to be pretty accurate... It dropped very close to 1/4 tank (7-8 gallons) over a known route of 70-80 miles, and was subsequently filled up at ~1/2 tank to the tune of 16 or 17 gallons. That was my first time taking the Bronco on that long of a trip. I hadn't really had a chance to observe the sustained rate of drop previously. My regular use will make it too difficult to make much of a calculated average, so I'll have to fill up before and after another long-ish drive to know if it has improved.

Some of the speedo calibration threads have reports of less fuel consumption, less fumes coming in the back window, etc. That sounds like a placebo effect to me -- I can't think why the calibration of the speedo would affect anything the engine is doing, unless there's some sort of 2-way communication at play -- but there's a slim possibility there of it having affected my MPG's.

'92 Bronco Build Thread - '95 MAF 5.0, H5 axle code, York OBA, 3G alt, custom jump seat console, flomaster steps/sliders.
http://www.supermotors.net/28006
fodder is online now  
post #33 of 33 (permalink) Old 05-03-2018, 01:18 PM
Registered User
 
Join Date: Oct 2015
Location: Dunwoody, GA
Posts: 212
Bronco Info: 1993 Bronco XLT, 5.8L, E4OD, Manual 4x4, Auto Hubs, Magnaflow 93312 Y-Pipe & 12636 Muffler, Soft Top
iTrader: (0)
If it helps, I did a good bit of highway driving on my '93 5.8L and was right at 2000 rpm at 75 mph on the highway. I have 32x11.50r15 BFG AT TA/KO2 on my truck and I have done the recalibration.
csilvestri is offline  
Sponsored Links
Advertisement
 
Reply

  Ford Bronco Forum > Bronco Discussions > 1980-'96 Bronco Tech

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Ford Bronco Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself. DO NOT USE Gmail.com accounts. If you only have a Gmail.com email please contact the administrator here

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome