P7100 Timing

[supergas]

I am putting together a engine for a friend for his 95 auto truck, What is a safe pump timing? Also is there any info online I could study, I left the manual at the shop. Thanks in advance for any help.

 

[Joe G.]

Get yourself a beer, get comfortable, search this forum archives for timeing, and read until you pass out.

 

[Jim Fulmer]

Supergas I'm with you, from what I hear and read 15. 5-16 is about right but some have had troubles when mixed with propane at that timing level, I want to go with 15. 5 but that is mod number. . 4... . 5... . 6 that's it! Any takers



Jim

 

[Joe G.]

The timing is dependant on which pump you have. This is by CPL number. There is a chart about the timing vs CPL number on Fritz's site. It's not a one size fits all. The chart is here: http://www.dodgeram.org/tech/dsl/FAQ/timing.htm



The CPL is on the tag on the gear case in front of the injection pump.

 

[Reddog1]

Joe,



I am a little confused. It’s my understanding the CPL number is not on the pump. Does this mean the P7100 pumps are not interchangeable? Which determines the timing, engine or pump?





Wayne

 

[HoleshotHolset]

The pumps are 100% interchangable... . even with the C8. 3L series engines... . same old P7100.

The CPL just determines what settings/parts and so forth are goin' on inside the pump.....

The relationship between the pump and the engine via some gears and shafts determines the timing..... you gotta take a gear off, shake it all around, sprinkle fairy dust on it and put it back on in the right position and you have adjusted the timing.



Hope this helps,

Matt

 

[supergas]

I guess I am going with 15. 5 seems everbody thinks that will work, going to learn on this engine then tackle my '96. Found the instructions to read on last night at http://www.dodgeram.org/tech/tsb/1994/18-10-94/18-10-94a.htm After looking at the manual today looks correct. Thanks again for the info and wish me luck.

 

[Joe G.]

Wayne,



The delivery valves are different sizes. The plungers may also be different. We need Joe Donnelly to chime in here about that. The size of the injectors has a big affect on how much fuel can be delivered. This also affects the proper timing to get the most out of the engine. The CPL (Construction Parts List) is the number that determines what combination of parts was used to assemble your engine and the initial setup that was used. As far as I know you can put any P7100 pump you want on any of these engines. That does not mean that all the pumps are the same.

 

[Reddog1]

Ok Joe Donnelly, where are you? I count on Joe G. and a few others to educate me on this stuff. Joe G. says we need you to chime in, so where are the chimes?



Like supergas, in his original post of this thread, I too wonder what is safe pump timing? I am sure the factory settings would be safe, but I cannot help but think they are very conservative.



I am still trying to understand the data at http://www.dodgeram.org/tech/dsl/FAQ/timing.htm.



If we ignore the smog issue, do we set the timing as many degrees BTDC as we can to stay just below melt down on the EGT?



Wayne

 

[Don M]

an auto truck like you have is best set around 14 to 15 degrees and manuals generally do best maybe one degree higher.

I have mine at 16 or 5. 6mm for CPL 2175. Mine is a 5 speed.



The higher HP guys around here even with the auto pumps are running no more than 16.

It starts to hammer alot louder after about 16.

The trucks with higher rpm capabilities via gov springs can go maybe 16. 5. Raising pump timing will increase fuel mileage too.





Don~

 

[shendren]

jessup (cummins) set mine at 15. 5. i have an auto trans.

 

[cumminsgetme]

Best efficiency will be around 15-16 deg timing. More timing will increase cylinder pressures and decrease egt's (but not much!!). How much are the cylinder pressures increased???... I don't know, but hope to test the different scenarios in a few months. I have found that with more timing the truck seems to have a little stronger top end, however don't take this to heart. I have not dyno'd the different timing specs,..... I'm only going by seat of the pants. I'm not concerned with my timing being at 19deg, however I will not advance it any more and definately would not use propane at 19deg. The difference in the smaller pumps vs. 215 pumps are cam profile, plungers, and delivery valves. There may be other minor differences that I'm not aware of, but these are the major differences.

 

[Joseph Donnelly]

Not much more to say. As you increase timing the torque at 1500 rpm and thereabouts decreases and the top end power increases. Too much timing means the cylinder pressure just got high before the crank turned to an angle where the pressure will push the piston down and rotate the crank. The pressure tries to hamer the piston rod and crank out through the main caps because they are still too much in a straight line. For about 2000 rpm cruising I like 15-15. 5 deg. with the 215 hp pump that has some advance in the design of the plungers.



The pump part number determines the plunger lift vs. timing. The cpl (critical parts list) will give you the stock timing setting and help you if the stock pump is still on the engine.

 

[Reddog1]

I am stuck on????????



1. If it is the cam profile, plungers, and delivery valves are the difference in the pumps, why is it the engine determines the timing?



2. Is there a difference between the engine cam for auto and manuals transmissions?



3. If there is a difference between the engine cams, what problems would you encounter if you mismatch the pumps?



4. If we set all auto trans timing to 15 degrees and the manuals at 16 degrees, can we throw away the charts?



5. Do we only get the charts out for smog purposes?



6. How can I recognize if I have set the timing too far advanced or retarded?





So far I’m thinking; Rods bent, too much advance . Pistons melted, too retarded .



I really appreciate you guys input, ya might learn me somthin yet.



Wayne

 

[pwknapp]

Anyone know of a good shop in the Lousiana are that will time the pump other than spec?

 

[WBerry]

shendren,where did you get the timing done at?what did they charge app. ? bill

 

[Joe G.]

The Charts

Wayne,



The thing to notice from the charts is that different plunger lifts are required for a specific timing. This, of course, assumes that your pump is the one that came with your truck. For example, 13. 4 degrees advanced varies from 4. 28 mm to 5. 9 mm of plunger lift. So you can't just throw the charts away.

 

[Don M]

Wayne,



I guess the first thing to do would be to define where you want your truck to be as far as HP, smoke levels, fuel economy, longevity, and for some, the levels of NOX you blow out of your pipe.



The injection pump fires the fuel load via the injectors at a certain crank position depending on the timing you set, same as a gasser fires the plugs.



Now, that being said, if a governor spring kit is in your plans for modifications you will be increasing the total rpm of the engine and more advanced timing can beneficial for high rpm power.



Back to the longevity part... if you advance the timing past about 16 the fuel load is delivered earlier at the crank position or the position of the rods is at an angle on the crank that it hammers on the bearings harder. I feel the hammering has a long term effect on bearing life.

Some guys are running about 24 degrees on the auto trucks and some are running about 19 plus on the 5 speeds. This is helping in the high rpm band. I personally feel it is too high for long term durability and they hammer hard at low speeds.



I would use the factory spec as a guide and determine through testing what lift is best for you and your needs based on the goal you want to be at.

Like Joe G. said, the differing lifts in MM's can be totally different for each CPL or engine number.

Mine calls for 5. 6MM for a CPL #2175 to get 16 degrees timing advance.

The other CPL numbers use different (in total MM's of lif) to get the same advance.





Don~

 

[Joe G.]

Don,



The cam shaft being referred to by Joe D. and cumminsgetme is the cam shaft INSIDE the pump. The pump is gear driven. The pump gear is the upper most gear in the following picture. The camshaft gear is the other gear that is the same size as the pump gear.

 

[Don M]

oops!



Oh boy, can you say foot in mouth? Holly cow, I got alot to learn.

I thought they were one in the same.

Geesh... .



Now I get it.



thanks Joe.



Geesh again.



Don~