Timing,Advance or Retard.That is the question

[Underdog]

Several members have written about the advantages of

advancing the timing on the CTD. I have been avoiding

changing the timing,partly due to reading these articles.

http://www.dieselinjection.net/articles.html

A couple of sentences from the articles,"TIMING: Retarded

timing will also enable your pistons to live longer. Do not

advance the timing in a Cummins engine. "

Another "Now for horsepower: Engine timing,you must

retard the timing as the horsepower increases. Lower

the compression ratio,increase injector flow,increase fuel

pressure,retard the timing and increase the manifold

pressure. That is the formula for increased horsepower

and must always be followed. "

I hope I'm not violating any copyright laws by using quotes

from the articles but I wanted to show why I'm confused

and why I'm hesitant to advance the timing.

 

[dzlpwr]

This article has alot to do with the larger series Cummins engines. Advancing your timing in excess can and will eventually harm your pistons and other engine components but is also needed to efficiently burn all of the fuel injected. When you increase fueling you should increase timing b/c it takes a longer amount of time to burn the increased volume of fuel. There is a predetermined amount of time after TDC that the fuel must have completed burning. In order to accomplish this, advanced timing is needed. Even a stock diesel straight out of the factory will benifit a small amount from advanced timing due to the way is was set for emissions reasons. If you are going to build an engine from the ground up then there are other factors that must be included and timing can become a problem.

 

[dpuckett]

Underdog,



Also keep in mind that The guys at diesel Injection are out to maximize the bigger Cummins engines' output. I have read what they have said, and it sounds like they are not out to maximize economy per se, but to maximize longevity, and increase CONSERVATIVE driving habits, which increase economy. Some of their tuned Cummins put out upwards of 800 hp. This is in an engine from the factory with less than 450 hp in most cases. It is the same as Nascar Mark's 300 rwhp in his first gen DOdge. Not many guys do it, and it must be done right, or expensive components will be damaged. I think that in our B series engines with stock ot even Lucas injectors, we run little risk of blowing pistons or heads, given the relatively low pressure of the VE pump. As with most things, timing advance CAN be overdone if taken to the extreme. I had the timing on mine a little too far, I believe. I backed it off 1/16 in on the pump flange), it seems to be smoother, and smoking less. I keep saying I am going to see if my neighbor has a dial indicator, but you know how that goes sometimes. It runs good, and seems to be getting about 20 empty (93 C&C, loooong WB, 6500# EW, shrunken manifold. ) If I go with larger injectors, i will have to check the timing to make sure it isnt too far up. Going up to 1. 4-1. 5 mm shouldnt pose any threats. Go a hair more if you live at high altitude.



Daniel

 

[dzlpwr]

I was running 1. 62 mm lift when I first put my injectors in but I got tired of the extra noise and took it down to 1. 5 mm and started to notice a little more smoke at idle. Noise did go down a noticable difference though.

 

[BushWakr - RIP]

I agree with ALL of the above.

When you put in larger injectors they commonly have a higher pop-off pressure... that results in the fuel being released a tad later in the piston stroke OR retards timing.

An increase in timing is well within safe limits if you do it correctly and based on what you're other parameters are...

Our 1st gen trucks seem to like about 15-16 degrees advance.

Particularly when you take a step or two up in injector levels.

If you go too high you can cause extreme cylinder pressures and that will result in piston and valve problems. It also result in head gasket problems too. .

The original 1st Gen truck came with a non-intercooled engine, and the pump timing was set at 1. 35mm,, I'm not sure of the translation in terms of degrees advance, perhaps 12*?

Then a year or two into the series the timing was changed downward (for emissions reasons) to 1. 25mm or about 11*

Now, an original engine with 1. 35mm lift could safely be raised to about 1. 45-1. 5mm or 15* advance.

That is were mine is and I have no problems or signs of problems so far.

Some of the big HP guys are running as much as 35* advance,... now that is nasty...



bob.

 

[Steve Campbell]

So.....ah

What is the factory timing on those "big" engines that they are talking about retarding on the web site? Maybe they start out with 20% and suggest backing off to 15?????



Is the timing half-full or half-empty, kinda,sorta.

 

[BushWakr - RIP]

I think the timing is a "half full" item personally. It makes a valuable difference by helping lower EGT's, improves throttle response, contributes to higher HP, helps reduce smoke, both cold and warm engine, results in a smoother idle, and some other items as well.

Like anything though you can't take it to the extreme edge and still expect zero downside,,, just common sense really.



I was pretty nervous about having mine changed, I'll be honest about that. I felt that the stock recommendation was there for a reason.

After lurking in here and one or two other places, as well as a chat with Joe Donnelly (sp?) I got a bit more comfortable and raised it in two stages. No negative effects that I can speak of with either stage of the increased timing.



Funny you know, I came to realize lately that the jobs that seem tough or risky are to a large extent "tougher" out of nervousness to mess something up. Not to say that you can't hurt things if you're not careful and work you way up to them.



FWIW... .



bob

 

[R.E. Miller]

Re: So.....ah

Originally posted by Steve Campbell

What is the factory timing on those "big" engines that they are talking about retarding on the web site?

FWIW, the timing on big Cummins engines is all over the place depending on Hp and application. It is not a real simple thing to set being that you have to pull off the cam gear and remove the number one injector to get started. You also must have an expensive apparatus and a dummy gear, and a good source of cam keys, and some patience



Russell

 

[Midnite]

Originally posted by BushWakr

Funny you know, I came to realize lately that the jobs that seem tough or risky are to a large extent "tougher" out of nervousness to mess something up.

Bob, that's a great statement. That was exactly what was going through my mind when I replaced my dead injection pump with a Cummins recon pump instead of going with PDR (this was right about the time I joined TDR), and I've been kicking myself ever since. The more we learn, the more doors open.



Regarding stock timing, I think awhile ago it was Power Wagon who posted a list of stock timing settings, sorted by application. If I remember that post correctly, the most advance used in a stock application was 2. 08mm (just a *bit* more than our 1. 5mm ). I'm guessing that given the increased cylinder pressures at that level of timing advance, that application was probably a high rpm, low fuel/power one.



Mike

 

[BushWakr - RIP]

Naaaaaaaa... . it would work fine in our applications so long as we used the RFI component every time...

BTW, I got a picture of a dummy gear on the front of my drivers license too...



bob.











RFI= RUN FOR IT !!!!!!!!

 

[dwalker151]

Most of the larger Cummins engines now days are not static in the timing department. All of the N14 series retard and advance timing with engine RPM. The computer advances timing at idle so that the engine will not smoke when the truck idles. Then when the engine revs up the computer retards the timing to avoid detonation and increase the amount of fuel that can be delivered.

 

[Underdog]

Thank's for the input. One of the main things I like about

this forum is, when someone like me posts a question

that may sound stupid to the more knowledgable members,

you don't put them down in order to show how smart you

are. I,for one,appreciate the help I get.

I went to Harbor Freight and bought some "C" shaped and

"S" wrenches. The "S" shape worked perfectly on the lower

bolt. they cost around $5. 99 for a set of five wrenches.

I would never have found the bottom nut were it not for a

posting by, Formula. Again,thanks for the help, guys.