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Old 10-02-2016, 12:42 PM   #1
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8.2 governor question.

I've just bought a 1990 Chevy bus with a DD 8.2 Fuel Pincher. On the 500 mile drive home the bus ran fine, pulled well, and maxed out speed at 40 MPH for the entire 15 hour ride home. Foot to the floor the bus pulls hard until it reaches 40 then its like I took my foot off the pedal. The School district I bought the bus from said they disengaged their governor, as a double certainty I physically ripped the linkage from their governor to the throttle linkage off. I'm thinking that they set the engine governor low. I have ordered a shop manual and its on the way, and I will be looking into a tachometer tomorrow when I finally get off work but my question is this: How do you adjust the max RPM governed speed? I saw a tutorial about the 6v71 motor, but there just isn't much out there about the 8.2. I know the dangers and the need for the tach, but I really think that the bus has something that is keeping it from revving high enough to pull itself on the road. On big down hills it would overspeed up to almost 60 mph, but on flat ground or hills, 40 mph is all it would do. I also understand that its probably geared very low, its a school bus and eventually i will be changing out the rear axle, but for the short term I want to make sure i can at least drive this thing on public roads without being a danger to other motorists!

Also, I want to clarify some terms "no load rpm" "low idle" "High idle" these terms confuse me. In my mind Idle speed is what the engine runs at when your foot is off the pedal. A "high idle" would be a switch or other means to bump the idle speed up a couple hundred rpm for some reason (pto, keep the ac working, or spin the alternator to power a load like emergency lights, winch, etc)

this "no load" stuff makes no sense. At what rpm should i cruise on the interstate at, what is the redline, what is the idle speed. Those are terms i Understand.
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Old 10-02-2016, 01:46 PM   #2
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Good afternoon. I to have an 8.2 Detroit 1986 version and I to can only do 45-49 mph without touching my governors.
I have the at-545 which is another speed issue to a point and my biggest speed restraint is my rear end gearing of 6.50.
A little history of mine with the governor is that the head mechanic at the bus barn told me I could adjust or do away with them/it but I would burn the rear gears up and with the governor's as is Is the 8.2 fuel punchers sweet spot for max longevity.
A little more about what I have figured out along the way.
My 8.2 still has the factory build tags on the valve cover and this is a little of what it says.
Min. Idle RPM-700
Max RPM no load 3050
Max output 170 hp at 3000rpm
No load means there is nothing accepting or looking for output from the engine? Kind of like the engine sitting on a stand in a shop running with no tranny/pto or anything connected or for us the tranny in neutral.
My ideas to get my bus at least to 55mph is to change my 9r20 de mountable tubed rims to 10r22.5 tubeless rims and tire which should get me at least to 50-mph until I find my rear gear replacements?(have been trying for awhile) and I just found some 9r22.5 tubed tires that will save me from finding new rims.
For the rear end I have not found anything comparable to mine for either a total swap or just a differential change or just a ring and pinion change but I try looking all the time?
Gearing sizes I have learned?
I have 6.50 and even though hooked to the fuel pincher I can pull a trailer with a car and no changes (done)
If I change the gears into the 5 range then I gain a little more highway speed but
lose some towing/uphill/pull strength.
If I change into the 4 range then I gain a good bit of highway speed but lose all towing strength and any uphill/pull strength.
All of this is keeping the engine and tranny in its sweet spot.
The sweet spot is where the engine was designed to be to give max life for its intended use.
That's where mine was designed at and my calculations were to keep it there cause most get around 500,000-700,000 if taken care of and mine just hit 200,000 so even though it's underpowered I decided to design around my well maintained power plant instead of the money to replace it?
Some 8.2's were designed for 250hp instead of the fuel pincher 170hp?
If you and your resources can prove that's it's he same block and configuration just a blocker plate or smaller injectors or something like that please let me know.
If that's the case then I need to look more into my at-545 tranny. I already know the heat kills them and at one point I had a gear ratio vs RPM chart from this forum on them? But can't seam to put it in front of me?
Good luck and please post your decisions you make cause I am floating in the same slow boat to travel AMERICA.
I live in NC and the bus is one speed or another going to Texas
If it happens at 49 then I grew up and I always loved the back roads and once I cross that Texas line I know I have no backroad problems
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Old 10-03-2016, 02:33 PM   #3
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Originally Posted by Transporter2112 View Post

Also, I want to clarify some terms "no load rpm" "low idle" "High idle" these terms confuse me. In my mind Idle speed is what the engine runs at when your foot is off the pedal. A "high idle" would be a switch or other means to bump the idle speed up a couple hundred rpm for some reason (pto, keep the ac working, or spin the alternator to power a load like emergency lights, winch, etc)

this "no load" stuff makes no sense. At what rpm should i cruise on the interstate at, what is the redline, what is the idle speed. Those are terms i Understand.
No load max rpm= Put your foot to the floor in neutral, AKA redline

Low idle= base idle speed of the engine, anywhere from 600-1000 rpm

High idle= 1.5-2 times as fast as low idle. Used for warm up, faster air build time, to prevent wet stacking, etc.


How fast should your bus run? Depends on what limit you hit first.

1)You could be gear limited, meaning that your final drive ratio is too high and the engine is redlined.

2)You could be governor limited. Meaning there is a speed limiting governor that will kick in keeping you slow.

3)Or you could be power limited. Meaning that the engine isn't making enough power to keep accelerating.

Odds are, it's one of the first two.
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Old 10-04-2016, 05:16 PM   #4
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It is definitely hitting the no load max rpm. The question i have now is: Did the previous owner, Wayne County Schools monkey with the no load max governor. I cannot find the gear ratio of my drive axle so until I get a tachometer I don't know if I'm cruising at 40 mph at 3050 rpm as stated on the valve cover, or if I'm cruising along at 2000 rpm. Either way I am pretty certain that i am running at whatever the max no load rpm is. Any suggestions on tachometers?
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Old 10-04-2016, 09:18 PM   #5
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Update, either the engine governor (no load max) is set low, or there is some other speed governor on the bus. I have used a gearing calculator and come up with some numbers. I know my tire size, transmission final drive ratio and the stated no load max rpm of 3050. Using these numbers if I hit my max speed of 40 mph at 3050 rpm then my rear end ratio is 9.44. I seriously doubt that my bus has a rear end ratio that low. So I need to figure out how to disable any speed governor that the school district installed, or turn the engine governor back to where it belongs. Any thoughts?
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Old 10-04-2016, 09:54 PM   #6
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what I wonder is what transmission you have.. if its an AT545 it should be shifting 3 times... 1-2,2-3,and 3-4 Im wondering if you are never getting into your final gear...

have you looked to find a tag on the transmission?

second thing is to make sure if that transmissio has a shift cable that its not broken, disconnected, or pulled too tight... I know the AT545 doesnt like a broken shift cable.. it will fail to make all of its shifts..

in the worst case you may have a 4th clutch engagement issue... at least i think thats the clutch which needs to grab for 4th gear... someone more versed on the 545 can tell me...

lets play for a moment here..

lets say your calculations came up correct for what you were attemting.. assuming a 545 would be a 1:1 ratio you got 9.44 for a gear ratio..
say that transmission failed to shift to 4th gear and stayed in 3rd.. it has a 1.41 ratio in 3rd..

you would have a 6.69 gear.. still far fetched..

lets say the transmission was really buggered up and stayed in 2nd gear... a 2.25 final ratio..

that gives you a "4.19" gear.. 4.10 maybe?

just throwing ideas out...

-Christopher
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Old 10-05-2016, 12:55 AM   #7
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Good thinking, but I believe my transmission is functioning correctly. I do believe it's the Allison 545 and have counted the shifts. It does indeed shift into 4th gear, no strange noises or slipping noticed. It pulls well until i reach 45 indicated on the speedometer, 40 GPS, then it really feels as if I've let off the throttle. It doesn't slowly loose power like a normal vehicle does when you max it out with a gradual decline of acceleration, it pulls until the governor kicks in. I used to drive over the road tractor trailers for Warner and the trucks were governed at 70 MPH. This feels exactly the same. So either: the school system installed some speed limiting governor that was not properly disconnected when I purchased the bus, or: they turned the mechanical engine governor down to some lower RPM setting and I'm not getting full revs. I've ordered a tach so hopefully it can shed some light.
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Old 10-07-2016, 08:25 AM   #8
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Most likely there is a road speed limiter. It could be attached on the side of the governor, or anywhere where it will intercept your throttle input so it can back it off once it hits 40 mph. Remove the air cleaner and look around. Take some pictures if you have to. Also, check the speed rating on your tires and make sure you don't exceed that.
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Old 10-07-2016, 03:26 PM   #9
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If anyone has a mechanical 8.2 I would love to see a picture of the governor's so that I have a better idea of which one is which and what to adjust/disconnect?
I and my computers still suck at posting pics?
I can takes pics of mine and post in my album but that's about it.
I have several things interconnected with my throttle cable including a homemade plate with a cable extension a couple of springs out to other things and anchor plates but to me it looks like it is mounted on top of an inline butterfly valve for something?
Thanks
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Old 10-23-2016, 11:01 PM   #10
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I have an 8.2 but don't know what a governor looks like.

I have rebuilt many car engines over the years... I know which end of the screwdriver to hold... but I am a greenhorn around diesels. I'm in the middle of a conversion on a 1990 Ward (AmTran) with an 8.2. I can take a couple of pictures but seriously... I don't know what I'm looking at.

Ross
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Old 10-24-2016, 11:01 AM   #11
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The engine governor which is integral to fuel control, will be located inside the injection pump which on an 8.2 resides in the valley between the two cylinder banks. You won't ever see it because, like I said, it's inside the injection pump.

The governor that transporter should be looking for is a road speed governor, which should be located somewhere on the throttle cable between the injection pump and the pedal.

* Not to be misleading, but 2 cycle detroits, along with a few others, run a unit injector. This style has the pump and injector all in one and the governor would be located elsewhere on the engine, with control rods connecting it to the injector.
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Old 10-26-2016, 05:30 PM   #12
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Quote:
Originally Posted by Booyah45828 View Post
The engine governor which is integral to fuel control, will be located inside the injection pump which on an 8.2 resides in the valley between the two cylinder banks. You won't ever see it because, like I said, it's inside the injection pump.

The governor that transporter should be looking for is a road speed governor, which should be located somewhere on the throttle cable between the injection pump and the pedal.

* Not to be misleading, but 2 cycle detroits, along with a few others, run a unit injector. This style has the pump and injector all in one and the governor would be located elsewhere on the engine, with control rods connecting it to the injector.
8.2 NA
I have two questions?(go figure)
From what I can tell is that my throttle cable goes directly to a fuel block?(it has an electronic fuel solenoid mounted to it) On the front top of my block and connected to a plate on a valve/rod/butterfly type? Also connected to that plate is a cable down to the tranny(545) and two springs to pull back to closed/happy position for idle I assume? The throttle cable does have about 7-threads showing to adjust it but I think that would mess with the idle speed.
1st question? Do I adjust the plate at the rod tighter for more RPM?
2nd question? I just watched a video of a man that added turbo to his natural breathing 8.2 to boost his? but didn't go into a lot of details or everything he had to change or replace? Is that something to look into?
Thanks for any thoughts/ideas good or bad.
I want to do this one time and caddie kid the other day made since when we were talking about rear gears.
I was told when I bought the bus from the old mechanic at the bus barn that if I adjusted the governor's then I needed to change the rear gears or they would burn up and two busses that his church bought one they changed gears the other they didn't and was paying for a rear end? so I have been focused on gear changes but Caddilac kid said in a nut shell/my mind that the gear size does not matter (properly maintained and oil) as long as your engine and tranny can turn them to your required speed. Not trying to put words into anyone's post/mouth?
Still haven't found a tach. So I have to do that before I touch/adjust anything. I was trying to find a plug and play tach. But the only thing I can find for mine gets connected on the outside of the alternator to read RPM and has to be calibrated with a timing light?(how accurate is that?) no electronics to connect to except a test probe in a wire?
Any ideas thoughts good or bad are appreciated
Thank ya
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Old 10-26-2016, 09:42 PM   #13
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Originally Posted by Transporter2112 View Post
It is definitely hitting the no load max rpm. The question i have now is: Did the previous owner, Wayne County Schools monkey with the no load max governor. I cannot find the gear ratio of my drive axle so until I get a tachometer I don't know if I'm cruising at 40 mph at 3050 rpm as stated on the valve cover, or if I'm cruising along at 2000 rpm. Either way I am pretty certain that i am running at whatever the max no load rpm is. Any suggestions on tachometers?

Is this Wayne County Schools, you are talking about, is it in North Carolina? I live in Goldsboro,NC, that in Wayne County. I just bought a 1991 Thomas short bus in August 2016. It has a 8.2 engine.
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Old 10-27-2016, 04:07 PM   #14
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Jollyroger, Pictures are worth a thousand words.

If I had to guess. What you're talking about is the adjustment for the cable in order to take out any slop. Have someone sit in the bus and hold the throttle pedal to the floor. If you don't have a road speed governor, then the only way to get more rpm/higher top speed is through changes to the injection pump.

As far as burning up rear gears. It's possible to turn them too fast under too much of a load that you'll have a lube failure. You'll see that occasionally in semi trucks when they try to pull up the mountain in Jellico tn at 80 mph. But I can't make any statements like "taking a 6:34 gear over 60 mph will burn it up" type thing. Certain gear sets will have a max power/max speed spec but you have to know the specific axle in order to even find the literature that will state that.

It's one of those things where you gear the rear end for it's intended usage. My preference for gearing is as follows. For an over the road skoolie I'd choose a rear axle ratio so that you can cruise at 55mph when in direct drive at 80% of the engine's goverened rpm. That usually seems to give about the most desirable characteristics of acceleration and cruising speed. If you need to go faster, get an od or double od trans, or a brownie box.

Alternator tach drives will vary based off of belt slip. They can be both right and wrong depending on the setup. You also might have a threaded hole in the flywheel housing in order for a sensor to read the teeth off the flywheel.
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Old 10-27-2016, 04:18 PM   #15
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I ran my DEV up jellico foot to the floor with an AT545... lol I slowed down.. the radiator fan is blasting.. but I dont shut off the A/C and nothing has ever broken..

I ran up Monteagle the same way..

the onbly thing that was every said to me about short gears.. was that the smaller the pinion gear the less amount of tooth-area contact you have on the ring.. so that too much torque and you can break things... nothing was ever said about speed.. jyst running high torque...
-Christopher
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Old 10-27-2016, 04:30 PM   #16
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Thanks for the reply and info. It looks like the cable adjustment to me also.
I still suck at trying to post pics? But I will add a few of the throttle assembly and engine to my album in a few minutes.
Thanks for the advice.
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Old 10-27-2016, 05:13 PM   #17
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Ok I stuck some pics in my album of my throttle body.
Does the cable from there down to the tranny tell the tranny when to shift?
I still have a blocker plate on my shifter from the school system and have been wanting to remove it to do a little manual shifting cause my tranny shifts through the gears and I am in drive by 25-mph and have to get up to 49 in drive from there so I was thinking I would remove the blocker plate and manual shift to stretch the gears out a little more? Any thoughts on that?
Thanks for any advice.
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Old 10-31-2016, 01:21 PM   #18
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Does the cable from there down to the tranny tell the tranny when to shift?
Yes, that is the tv cable. That being out of adjustment will cause early shifts, low line pressure, and the trans to overheat.

Quote:
Originally Posted by Jolly Roger View Post
I still have a blocker plate on my shifter from the school system and have been wanting to remove it to do a little manual shifting cause my tranny shifts through the gears and I am in drive by 25-mph and have to get up to 49 in drive from there so I was thinking I would remove the blocker plate and manual shift to stretch the gears out a little more? Any thoughts on that?
Thanks for any advice.
I wouldn't make it a habit doing that. Adjust the tv cable and you shouldn't have to touch it, unless you want to hold a specific gear going up or down hill.
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Old 10-31-2016, 03:37 PM   #19
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misadjusted TV cable makes your shifts too early also... and low line pressure not only overheats transmissions, if you have enough torque behind it then you slip clutches and damage things
-Christopher
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Old 10-31-2016, 03:56 PM   #20
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I don't have a tach yet but my 545 is in 4/D around 25mph and I get to 45mph from there?
We shift from 1-2 at 10mph 2-3 around 17-18mph.
I think the lower gear shift points are to close together?
I am in drive/4 before I really even get going good?
Do I adjust the cable in or out for stretching the shift points?
Please look in my album at the pics I just added.
With nothing governing the throttle cable does that Meen I have an engine speed governor only? It is a fuel pincher? It runs like a well oiled sowing machine and it sounds like it is doing what it can.
But I wanted to push it a little more to see what it felt and sounded like? I have no feel of anything pulling or throttling power? When I know I am hitting a strait stretch I have a stick for cruise control and the engine doesn't change tune from flat lands to mild hills or down hill? It's steady and the actual speed is all that changes. Normal 45mph up my worst hill 43mph and downhill strolling 49mph.
Would like to do 55?
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