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Old 06-24-2017, 02:56 PM   #1
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Timing info - where do i find it

Howdy,

im looking into advancing my pump timing for fuel economy and im trying to figure out my starting point.

so i look at quickserve and i see no easy answer. after clicking a number of ghosts chases, i found this -
copied from quickserve.


Advertised HP: 190 @ 2500

RPM

Secondary Adv HP: N/A @ N/A

RPM

Torque Peak (lb-ft): 475 @

1600

Pump Manufacturer/Model:

Bosch P7100

Governor Type: RQVK

Boost Control Provided: Yes

Fuel Pump Type: Inline

High Pressure Fuel Line ID

(mm): 1.8mm (0.07in)

Engine Application:

Automotive

SUPP Emission Test (gms/BHp-

hr BSNOx): 6.0

CPL: 1261

Certification Agency:

EPA,CARB

Mexico Sedesol

TEPA

Certification Year: 1993

Engine Cylinders: 6

Engine Family: B Series

Structure Code: 02 EBM

Manufacturer of Record:

Cummins

Dual Power Rating: No

FP Gear Timing (deg crank):

0 deg retarded

Engine Design Phase: Current

Product

Engine Aspiration: Charge

Air Cooled

High Altitude (>10K feet)

Rating: No

Managed Torque: No

Speed Sensor Location: N/A

Fuel Pump Mounted Angle: 35

degree.


so if thats correct, its at 0? tdc

somewhere i read most 5.9's are around 13.5* BTDC

what am i doing wrong?
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Old 06-24-2017, 03:20 PM   #2
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wow 0 degrees sounds really low... I dont know alot about cummins... the lowest end of the navistar DT-360 (5.9) had a setting of 15, the higher HP rated versions showed the timing at 19-21 degrees.. and appeared that going to that setting wasnt going to push the envelope of the EGT even under load... cummins may be a lot different.

is yours Pre-electronic? like a 6BT? 12 valve?

-Christopher
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Old 06-24-2017, 06:51 PM   #3
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yes, pre electronic, '93 6bta

the other real confusing thing here is the follow chart.

Diesel Timing

My cpl is #1261 that puts it over in the (e) column. and i don;t even know..... that column ends around 13.
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Old 06-24-2017, 09:03 PM   #4
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On a stock 6BT, factory timing was 6-7'degrees before TDC.

Optimal fuel efficiency comes at 12-16 degrees before TDC.

However, in stock form you're only going to see an increase in mpg of around 3 or 4 percent. So it's essentially a negligible difference.

Where you see a difference is once you've done an appreciable amount of power mods. (Not just turning up the fuel, but enough mods to the point where you've had to install larger injectors.) Then you have to change the timing in order for the mods to make maximum power, and in the process you get much better fuel efficiency.

And adjusting the timing is a bit complicated. There's more to it than simply moving the pump gear 7 degrees. From the factory, the timing may be off by as much as 3 degrees in either direction. In stock form, the timing isn't vital enough to be set very exactly. Doing it properly involves using a dial indicator to find TDC on the pump, the flat spot on a crank lobe in two places, using a degree wheel to precisely split the rotation between those two places, then timing the pump off that mark.
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Old 06-24-2017, 10:23 PM   #5
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Advancing timing may only get you a noisier engine and smoke. While timing may be 0 degrees at idle the timing advance in the pump will advance as engine speed increases. Be carefull if you advance too much you can blow a piston apart along with your egt,s skyrocket. It,s really best to talk to a real diesel expert before messing with the timing or you may be buying an engine.
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Old 06-24-2017, 10:52 PM   #6
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thanks for the input everyone!

i found timing number. it was stamped on the engine data on the motor. it says - 12 degrees.

ok

well that chart ends at 13.5 degrees for this CPL. maybe this isn't worth pursuing? its not going to be much of a change if i do it.
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Old 06-24-2017, 10:56 PM   #7
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thanks for the input everyone!

i found timing number. it was stamped on the engine data on the motor. it says - 12 degrees.

ok

well that chart ends at 13.5 degrees for this CPL. maybe this isn't worth pursuing? its not going to be much of a change if i do it.

Nah, just leave it where it's at. It isn't an easy job and if you're already at 12, that's pretty close to optimal.
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Old 06-24-2017, 11:33 PM   #8
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yeah,......... but im only getting about 7 mpg. lots of others are getting 10-11
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Old 06-25-2017, 09:27 AM   #9
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are the others with the same bus geared similar and running the same transmission / RPM / Speed? ive found theres a ton of variance in MPG based on various configurations / driving habits on similar busses..


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Old 06-25-2017, 11:53 AM   #10
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when i read about the benefits of retarding the timing - better economy, cooler eg temps, i got real interested. I'm on the bottom of most of the mpg claims. on my recent trip to Az, i used an an app to track fuel consumption. i've only done the the math a few times, since i'm better off not knowing.

just running, balls to the wall, 70ish, cummins 5.9, 4.7 rear, AT545, 2700ish rpms
7.5 MPG
if i turn on the generator, that drops to 6.5 MPG. i ran the gen overnight and it drank less than a 1/8th tank.

if others jump off a cliff, ya, i probably want to too
is 10mpg unrealistic?

hoping good news with the 1545 swap
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Old 06-25-2017, 12:29 PM   #11
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You're never going to get premium fuel economy running 90% of the way to redline.

The lockup torque converter in the new transmission should help that a bit, but it's not going to get you all the way there. My calculator shows 2,664 rpm at 70 mph with no torque converter slip. (I'm assuming you're running 11R22.5s.)

To get your rpm down to a point where you might get better fuel mileage, you'll probably need to either slow down some or put a faster rear end in it. Or just accept 7 mpg.
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Old 06-25-2017, 12:42 PM   #12
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That's why i don't do the math very often.

i do like going fast-ish.

i recently move the fuel plate and played with the afc, so this trip was its first shake down. i used to do 67, 62 towing. now it towed easily at 67, and i frequently held 70 and 72, which never happened before.

if i go much faster and im going to get a ticket
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Old 06-25-2017, 03:13 PM   #13
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Don't mess with it.

Unless it's way off, changing the timing isn't going to net you the fuel economy you're looking for.

For starters, do you know if the chart is talking injection or ignition timing? What about the posters listing numbers here? Which event are they talking about?

If you don't know any of that, then you probably shouldn't be messing with it. Too much of a liability for little benefit. This is an area where you should pay someone with the know how and equipment to do it.

As far as EGT's go, retarding the timing will create hotter egt numbers. Slowing down along with your new trans will give you the biggest fuel economy gains.
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Old 06-25-2017, 04:16 PM   #14
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thanks guys.

i won't mess with the timing. i appreciate your wisdoms.

i think that was injection timing, but i'm learning on the fly and it is over my ability. and tools owned.

ok, do injectors wear out? i see lots of replacement ones, would that improve mileage or power?

i probably don't have a problem. i should let it all be.

if i got a 4.4 or 4.1 rear, i'd probably just drive faster.
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Old 06-25-2017, 04:53 PM   #15
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others can comment, but most often when ive seen injectors have issues it seems you get quite a bit of white smoke...

I never realized timing wasnt effective on a Diesel.. when I look at the book for my Mechanical non electronic DT-360.. the differences between the 165 HP and 190 HP versions are injector pump timing and fuel screw settings...

in the case of those though it seems backwards from the consensus here.. the higher HP versions have more ADVANCED Injector pump timing.. not retarded..

-Christopher
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Old 06-25-2017, 11:02 PM   #16
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Quote:
Originally Posted by cadillackid View Post
others can comment, but most often when ive seen injectors have issues it seems you get quite a bit of white smoke...

I never realized timing wasnt effective on a Diesel.. when I look at the book for my Mechanical non electronic DT-360.. the differences between the 165 HP and 190 HP versions are injector pump timing and fuel screw settings...

in the case of those though it seems backwards from the consensus here.. the higher HP versions have more ADVANCED Injector pump timing.. not retarded..

-Christopher

For a given injector size, higher power requires advanced timing. In order to get more fuel into the combustion chamber with the same size injector, the pulse duration will be longer, and thus the injection pulse must start earlier.

Another common difference is pistons. Higher horsepower variants will often have a larger fuel cup. I know Detroit did that with the Series 60 pistons and Cummins did it with the pistons in the 310-400 horsepower ISCs. It's a bit counterintuitive because it actually lowers compression, but with how much air the turbos on those engines are blowing into the cylinders, it works out.
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Old 06-25-2017, 11:30 PM   #17
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Intesting on pistons but then you do have more area of pressure for the explosion to work on.. perhaps that and the additional fuel are two big factors in more power .

I know navistar in the later 7.3 went to a split shot injector. That gives an initial shot to start the fire then pauses then sends another shot into the fire. They claim a more complete and efficient burn..

So does turning the screws or sliding the fuel plate increase injection pressure or increase injection duration?
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Old 06-26-2017, 07:53 AM   #18
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i'm quite sure i misspoke on the advance /retard issue. 12* Before TDC is normal, if i twerked it out to 13.5* BTDC - i called that retarding because its further away from TDC. its probably advancing, fuel sooner, longer.

its my opinion that the fuel screw and plate only allow more flow to the injector. no change in pulse timing. i think to get more fuel, pressure may increase, but more than that, just the obstruction of flow is taken away, maybe a decrease? idk
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Old 06-26-2017, 08:08 AM   #19
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I know on navistar, there is the fuel screw then the "anti-smoke" screw.. from my understanding if you over-fuel too early you black-smoke. (which I think means less efficiency).. I havent played with my fuel screws on that mechanical engine yet..

in the gasoline world valve timing is big factor.. in fact advance or retard ofthe Cam is a big thing.. (alas why EVVT is huge in new cars).. seems i never hear of valve timing at all in the diesel world.. its less of a factor when dealing with a single cam.. but with separate intake and exhaust cams you can affect cylinder pressures and for how loing quite a bit wit hjus ta few degrees of timing either direction.

from everything I tend to read.. diesels run more efficiently when right at that threshold between being Lugged and not.. as opposed to spinning them fast under less load.. I can defimnitely say that my T-444E runs alot hotter at higher RPM even when under light load.. more heat to me = less efficiency.. i'll know alot more about how my 444E performs at various RPM ranges soon with my new transmission.
-Christopher
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Old 06-26-2017, 10:04 AM   #20
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So does turning the screws or sliding the fuel plate increase injection pressure or increase injection duration?
Christopher

My understanding is it's a duration increase (in a mechanical engine.) The fuel screw on an injection pump dictates plunger travel length. Turning the screw up increases plunger travel, which results in more fuel volume. Injectors are basically pressure relief valves. Once a certain fuel pressure is reached in the injector line, the injector starts letting fuel through to relieve pressure. Longer plunger travel equals more fuel equals longer duration of injector opening.

But now that I'm thinking about it, I guess it's possible that the pump is moving the fuel faster than the injector can release it, so maybe pressure does peak higher. Essentially the injector opens and closes at a set psi, but whether or not it can let through enough fuel volume to maintain the same peak fuel pressure probably depends on the size of the injectors.

I might've thought about this too much and confused myself. Haha

I ask some questions today and report back what I find out.
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