idi timing

[bigblue85]

does anybody have the steps typed out or have proper procedure to time an injection pump for max efficiency??

 

[86ford69]

I would also like some info on this.

 

[Kevin 007]

If you are going to time it by ear, the pump should be set in a spot that allows the motor to start instantly when hot. There is a very small "sweet spot" that has to be found to achive this.
When the pump is off a bit, it will usually take a few revolutions to get these things to fire.


Thats all I know about the subject....

 

[OLDBULL8]

Read this post. http://www.oilburners.net/forums/showthread.php?t=47355

To properly time an IDI, you should have the proper equipment. A Ferret pickup and digital timing light or a Luminosity probe and pickup.

http://www.oilburners.net/forums/showthread.php?p=482137#post482137

 

[Diesel JD]

I don't like timing by ear. It's trial and error. If you insist, mark where your timing is now. Do not move the timing while the engine is running, it might work but you risk completely ruining the pump or worse...core value of the old pump could be nil. Mark where your timing is now in case you don't like results. If you think it's retarded move the pump toward the passenger side about a dime's width, then take a ride, and observe idle. What you want is easy starts, good fuel economy and no overly harsh clatter on the one hand but no smoke at idle on the other. If you think it's too far advanced move it a dime's width to the driver's side. You might have to do this a few times to get it where you like it. The things to remember are unless you ahve a lot of IDI experience your chances of getting it right are pretty low and more attributable to luck than skill. Second, don't lose your current timing mark just in case you aren't happy with your results. With tools the procedure is much easier. Luminosity is what I am qualified to speak about. Here you pull the glow plug on the cylinder you are timing, carefully install the luminosity probe and magnetic pickup. I prefer to attach them one at a time so I know if one is not giving a correct signal and which one it is, you need two inputs to time a diesel, rpm and degrees. You need to dial in the correct offset for the hole you are using and the cylinder you are using. We could argue a lot about the correct setting but it depends on cetane and BTU content. Values between 0ATDC and -5ATDC are right for different people and different fuels. I'm at around 2-2.5, but with B100 (high cetane, lower BTU) I should probably be close to 0.

 

[OLDBULL8]

Consider this when setting the pop pressure, fuel setting and timing of the IP. Lately, there has been alot of post's/discussion on this.

This is my theory of how a Diesel engine should work... I'm certainly not a Diesel Engineer, and my Math may be off. As the saying goes, For 20 yr I can't say en gin near now I are one.

The 7.3 IDI is basically a square stroker. Bore 4.110" Stroke 4.180" Gasser's are short stroker's. Bore is larger than stroke.

Timing is set at 2000 RPM. At that RPM you have 2000 RPM / 60 Sec. = 33.3 RPS / 8 = 4.1625 / 2 = 2.08 #1 cyl. fires every 2.08 seconds.
I assume its set there because the max torque is between ~1800 and ~2000 RPM.

If the timing is set at 8.5* to 9.5* BTDC. The piston @ (8.5*) is .084 (thousands) from TDC when fuel is injected at the recommended 1850 PSI. The burn starts immediately, the full load of injected fuel is in micro seconds. At 8.5* fuel injection starts at ~.023 (thousands) of a second BTDC, The IP injection curve effects the length of time of injection. Injector nozzle size and IP fuel setting determines fuel quantity injected. When the piston reaches half stroke upward it slows down due to the throw of the crank, and for an instant stops as it goes over TDC, then gains speed Of course the fuel continues to burn until the exhaust valve opens at ~ BDC. The Cam grind profile determines when and how long the valves open and close. Just imagine how fast the valves have to actuate. That leaves ~1 second for power stroke and ~1 second for exhaust stroke.

By setting an increase of fuel from the IP more than can be burned in ~1second, that would produce black smoke.

Black smoke is ignited but not fully burned. Waste of power and fuel.

White smoke is when the fuel does not ignite at all, but just heated close to autoignition point

Diesel fuel flash points vary between 52 °C and 96 °C (126 °F to 204 °F). Diesel is designed for use in a high-compression engine. Air is compressed until it has been heated above the autoignition temperature of diesel; then the fuel is injected as a high-pressure spray, keeping the fuel-air mix within the flammable limits of diesel. There is no ignition source. Therefore, diesel is required to have a high flash point and a low autoignition temperature. Autoignition temperature is ~410*. The cylinder temperature reaches ~840*+, most all this energy is contained in the precup and released thru the small spout opening of the precup.

Diesel fuel doesn't explode like gasoline, it burns, the energy is released by expanding hot gas continually throughout the stroke.

A turbo engine induces more air/pressure to each cylinder, which takes longer to compress and raises the cylinder temperature higher ~980*, hence the one degree more advanced (9.5*) for fuel injection which allows more time for fuel to be injected.

There are six sizes of plungers in th DB2 IP's identified by the 2nd model number, (25) .250 (27) .270 (29) .290 (31) .310 (33) .330 (35) .350

The IP injection curve would effect the length of time for injection, and IP plunger size would determine the amount of fuel along with the injector nozzel size.
All that air and fuel is squeezed/compressed into a very small space approx. 4.110 X .075 thick, plus the precombustion chamber volume, 6.9 is 18.34 CU and 7.3 is 20.42 CU.

Too much fuel or poor atomization would cause a knock.

I guess to sum it all up, at 2000 RPM a power stroke happens in such a short time, all things have to be right for a good running engine.

Am I figuring this right? Comments welcomed.

 

[Agnem]

That's an excellent assesment, and I'm sure it was painfull trying to compute all that, so I will accept it as fact. I lack the energy to double check you! There was only one point which requires affirmation, and that is that the timing is performed at 2000 RPM, because at that speed there is a reasonable assumption that no part of the slow speed timing cam can come into play, and consequently the timing of the IP is completely free floating, meaning that the internal fuel presure and advance piston control circuit has complete control over the advance cam. This is one of the reasons also why calibration is so important to an IP and the performance it delivers. This is also one of the problems with the luminosity method of timing, in that it encroaches on the range in which the low speed cam operates, however at 1400 RPM, it is at about the maximum speed at which the optical system employed by the meter can operate. Timing by ear is just not accurate enough. Yes, it can be better than nothing, but I consider myself good at it, and I can still be off by 2 degrees. 2 degrees is ALOT.

 

[Diesel JD]

I still really want to do comparative timing between luminosity and pulse with a sample of at least a few engines. If we could agree on a value to convert pulse to luminosity timing we could compare the means with a t-test and see if there exist any statistically significant difference in timing between the methods.

 

[romulus]

i guess i just got lucky then. i just put a new IP in my factory turbo, timed it by ear/smoke/knock/trial/error method and info i gathered here.

i wasn't sure i did it right since it was the first IP replacement i've ever done.........so i took down to an expert that has all the equipment....... 150 bucks later he said it was timed perfectly. i looked at my timing marks and they were exactly as they were. he said he moved it in both directions and ended up coming right back to where it was.

he asked me how i did that, i explained, and he said i got lucky.

good enough i reckon. sure am glad i got rid of that leaky old IP. best 350 bucks i ever spent on that truck.

 

[Agnem]

That would be OK with the same tank of fuel, but the other fundamentally difficult task with the luminosity method, is your actuall timing target is arrived at by checking the Cetane value of the fuel. I don't think anyone checks their cetane value, or has the equipment to test it. The chart you would need to reference is below.

You must be registered for see images

 

[mrmatthewhenning]

So I’m a bit lost. Trying to set the timing on 7.3 idi. Have a ferret and timing light. My digital snap on timing light is adjustable from 0-90. If I’m supposed to set timing to 7 BTDC should I set my timing light to -7? Or am I just looking at this wrong. I tried today to set it to 7 because my timing light dose not go negative. Running a ounds close. I just think that that is advanced 7 degrees and that would put my timing out by 14 degrees.

 

[Big Bart]

I replied in your other post, so take a look there. Not sure they ever answered the question posed of the best place to set timing. If one really wanted to optimize their HP a dyno at the wheels would be the meter of choice. Then play with fuel ratios, injector pop pressure, IP parts, and lastly timing of the IP.

For you and I getting 4-8hp more hp is not worth the time, money, and hassle. So in the other thread I explained what you need to do.

 

[ih8minimumwage]

So I’m a bit lost. Trying to set the timing on 7.3 idi. Have a ferret and timing light. My digital snap on timing light is adjustable from 0-90. If I’m supposed to set timing to 7 BTDC should I set my timing light to -7? Or am I just looking at this wrong. I tried today to set it to 7 because my timing light dose not go negative. Running a ounds close. I just think that that is advanced 7 degrees and that would put my timing out by 14 degrees.

If you set your timing light to 7 or 8 degrees the 0 mark on the pulley will be correct. If you set your timing light to 0 advance you'll line it up with the 7-8 degree mark on the pulley.

I just paint pen the 0 line on the pulley and set the timing light to the 8 degree advance. A Lisle pedal holder is great for getting to the correct RPM, and DON'T FORGET EARPLUGS.

 

[IDIBRONCO]

The paint pen on the timing marks is something that I've done for years. Both to IDIs and to my own gas engines. I use a White Out pen since it has a narrow tip.

 

[GerryL]

I'm fairly new to the IDI having bought a 1994 F250 7.3 IDI N.A. early this past summer. Nearly mint body and frame out of NC (extended cab, 8' bed), but it wasn't running quite right. Since the engine sounded ok mechanically and it had a low 128k miles, I bought it. I've been learning a lot. First I replaced the tach sensor; tach was dropping to zero at less than 1200 rpm or so. It still seemed down on power, and smoked grey/black under load. I was assuming someone had turned up the fuel. Backed off fuel 1 flat, then two and it really didn't change much other than having less power (still smoked). I ended up biting the bullet and buying a Tech-Time unit from eBay. I found my timing was 20 degrees advanced at idle! 8-( About this time an injector line snapped off the injector (someone removed line clamps). I put a new set of lines on (with clamps to deal with vibration) and while they were off I rotated the pump a bit to get timing closer to where it should be. I was then able to dial it in to 9 degrees advanced at 2000rpm with the instrument. Now it runs much better and the smoking issue is gone. Certainly not good to run that far advanced. The PO had glow plugs recently replaced and they all tested good, so I was happy with that anyway. Since then I've put on the complete Sidewinder package and have been very happy with it. Next up is to add pillar gauges and change the seat. We're planning on a cross country trip next year with a motorcycle in the back and a camper on the hitch.
I guess my bottom line is to suggest finding someone with a timing instrument or get one and learn to use it. Although I see your request was for max efficiency. Hmmm, I don't know about that, but I want reliable long term running. My truck got 16mpg unloaded after this work; I'm happy with that for what it is.
Edit; I see now that the original post is 10 years old , but Matt is looking for current info so I'll leave this up.