Cold start. Some no problem. Others don't. Why is that?

[BigBlueChevy]

This is one of those questions that always seem to boggle my mind. Perhaps because I'm probably missing a bit of information that's supposed to "join" the two together in my mind.

Here's my question. Cold starts. On a diesel. Obviously since heat and compression are used to combust fuel in the cylinders, if things get to cold they wont start. Then you factor in different compression ratio's. From an engineering standpoint the higher the compression ratio the more mass is being compressed. More mass in a smaller area means more heat and higher pressure.

This is where I start to get confused. Say you have a 6.5 Turbo Diesel, with a 19.5:1 compression ratio. And a 5.9 Cummins, with a 17:1 compression ratio. The 6.5 requires glow plugs to be on for about 7 to 8 seconds at 20*F in order to start. Now, in the same exact location, the 5.9, which has approximately 13% lower compression, can start with no starting aids (This means the key can be turned almost like starting a gasser. No, "wait to start".) The cummins will fire on the first revolution of the starter. Stumble for a second(lose about 200rpms), then be perfectly fine.

Could someone help me "fill in the blank" so to speak? I'm starting to confuse myself lol

 

[bison]

6.5 uses indirect injection,thats where the precups come in.injection happens in the pre cups
the 5.9 has direct injection,injection is directly aimed at the piston.

The 6.5 inj nozzle has a rather course spray pattern trough a single orifice.
Where as the 5.9 has a nozzle with 4 orifices with a far finer and wider spray pattern.

 

[BigBlueChevy]

6.5 uses indirect injection,thats where the precups come in.injection happens in the pre cups
the 5.9 has direct injection,injection is directly aimed at the piston.

The 6.5 inj nozzle has a rather course spray pattern trough a single orifice.
Where as the 5.9 has a nozzle with 4 orifices with a far finer and wider spray pattern.

First part I knew, just didn't think it would effect cold start conditions but I guess if you look at it that way it makes sense. Second I didn't.

But the higher compression ratio does allow for a greater cold start temp right?

 

[THEFERMANATOR]

The early CUMMINS with the single grid heater would start pretty quick, and some of the later 12 valves don't want to start up without fogging out a city block below freezing. Injector design and engine health play a large role in this as well.

 

[BigBlueChevy]

Interesting. So it really depends on the health of the engine, compression ratio, injector spray pattern, and obviously Direct or Indirect injection?

 

[NoDak]

When calculating the compression ration of an IDI, do they add the volume of the pre-combustion chamber to the clearance volume? If not, it would take a higher published compression ratio to get the same effective compression ratio for an IDI. Either way, you can't forget that the IDI has more surface area in the clearance volume (including pre-combustion chamber) for the heat of the ignition to escape as compared to a similar DI arrangement.

 

[6.2 turbo]

Don't forget timing makes a big difference , the more advanced you are the harder it will start cold,I advanced my cummins to 21 degrees, and no intake heater it needs ether if it is to cold,with stock timing it was fine. Same deal with my 6.2, not sure why some people think the opposite.

 

[BigBlueChevy]

Don't forget timing makes a big difference , the more advanced you are the harder it will start cold,I advanced my cummins to 21 degrees, and no intake heater it needs ether if it is to cold,with stock timing it was fine. Same deal with my 6.2, not sure why some people think the opposite.

ether is a big no no my friend:nonod:

 

[6.2 turbo]

Its okay if you don't over do it, the ether I use on the cummins says 50 percent on the can.

 

[NoDak]

Don't forget timing makes a big difference , the more advanced you are the harder it will start cold,I advanced my cummins to 21 degrees, and no intake heater it needs ether if it is to cold,with stock timing it was fine. Same deal with my 6.2, not sure why some people think the opposite.

If advanced timing doesn't improve cold start, why does the 6.5L IP have a cold start advance feature?

 

[NoDak]

Its okay if you don't over do it, the ether I use on the cummins says 50 percent on the can.

I suspect you may be correct with respect to "IF you don't over do it". The problem is, how to accurately measure and or administer a sufficiently small amount. Perhaps even more difficult, instructing someone in the art of not over doing it? Spray, crank speed, temperature, engine condition, yada, yada, yada.

I believe one thing to be certain. You will ever destroy your engine with ether, if you never use ether in your engine.

 

[bison]

John Deere and Case tractors among others came with a factory start fluid set up.
If properly used,ether wont kill an engine.
Glowplugs or intake heater should notbe used together with ether period.

Diesels are historicly harder to start than gassers.over the yrs engine disigners have tried many diff aproaches to overcome this problem with different results.

 

[6.2 turbo]

The cold start advance will do nothing at cranking speeds, also cam advance will be in full retard untill the motor starts and builds enough charge pressure to advance the cam ring,the cold advance just lets it go a little farther. Some inline pumps also have a start mode that retards timing at cranking speeds.

 

[BigBlueChevy]

John Deere and Case tractors among others came with a factory start fluid set up.
If properly used,ether wont kill an engine.
Glowplugs or intake heater should notbe used together with ether period.

Diesels are historicly harder to start than gassers.over the yrs engine disigners have tried many diff aproaches to overcome this problem with different results.

That's I'm aware of. My New Holland project motor has ether spray start, and so does the International with the DT466. From everything I've learned here its really hard to say. You get two distinct groups:

A: Ether is bad. Ether on a Cummins will turn the intake system into a flamethrower as the highly explosive fluid hits the Grid heater. Glow plugs will cause pre-detonation in the cylinder the moment they pass the intake valve. And disabling the glow plugs or grid heater wont stop damage because for every time you use ether it bends the connecting rods and push rods just a hair, thus dropping compression ratio and requiring MORE ether each time till eventually the engine cannot start without it. Its also bad due to the ether having a significantly higher flash point than diesel and the method its injected via air stream. Naturally, the ether will combust before the piston completes its compression stroke, which will impede starting.

B: Ether is ok if used properly. Its when you have intake heaters or glow plugs that are attached that will cause the damage. Ether combusts before the piston completes it compression stroke which, though slightly impeded starting, will provide a sufficient heat source to allow the diesel fuel to ignite, thus aiding in starting. And if ether is so bad, they why do the larger engines use it like the CAT's and DT series?

Personally, I'd jump on it in a heartbeat to take two identical engines, measure the connecting rods, push rods and internals, and start one with ether, and the other normal. Twice a day, at different temperatures for a week. Then disassemble both motors and re-measure everything and record any changes, just to see if there really is damage caused. This is a job for, the Mythbusters!

 

[BigBlueChevy]

http://www.youtube.com/watch?v=8t_Lnf5nQtE&feature=related

Look at Double Overtime, watch how much ether this guy uses to crank this thing up.

 

[NoDak]

Notice how that fella is carefully metering the ether in that video. He is a seasoned ether starter, don't you think?

I suspect the one thing most everyone in the whole ether debate "can agree upon" is that one must not mix ether and glow plugs (or grid heaters).

As far as damaging the engine? Wouldn't that be a function of how robust the design of engine, compression ratio, how crazy you get with the ether trigger and luck?

Typically, IDI's have high compression. In the case of the 6.5L, relatively small rods and bearing areas.

Most DI's are lower compression and typically bigger, more robust like the tractors mentioned earlier.

Don't get me wrong, I've squirted my fair share of ether in tractors, combines and trucks in my day. I am very certain though, never into an IDI. I can't recall the number of kits I installed on Allis tractors as a kid.

 

[bison]

That's I'm aware of. My New Holland project motor has ether spray start, and so does the International with the DT466. From everything I've learned here its really hard to say. You get two distinct groups:

A: Ether is bad. Ether on a Cummins will turn the intake system into a flamethrower as the highly explosive fluid hits the Grid heater. Glow plugs will cause pre-detonation in the cylinder the moment they pass the intake valve. And disabling the glow plugs or grid heater wont stop damage because for every time you use ether it bends the connecting rods and push rods just a hair, thus dropping compression ratio and requiring MORE ether each time till eventually the engine cannot start without it. Its also bad due to the ether having a significantly higher flash point than diesel and the method its injected via air stream. Naturally, the ether will combust before the piston completes its compression stroke, which will impede starting.

B: Ether is ok if used properly. Its when you have intake heaters or glow plugs that are attached that will cause the damage. Ether combusts before the piston completes it compression stroke which, though slightly impeded starting, will provide a sufficient heat source to allow the diesel fuel to ignite, thus aiding in starting. And if ether is so bad, they why do the larger engines use it like the CAT's and DT series?

Personally, I'd jump on it in a heartbeat to take two identical engines, measure the connecting rods, push rods and internals, and start one with ether, and the other normal. Twice a day, at different temperatures for a week. Then disassemble both motors and re-measure everything and record any changes, just to see if there really is damage caused. This is a job for, the Mythbusters!

Most if not all factory ether set ups uses a nozzle in the intake to limit the amount of ether that that can by injected per sec to prevent engine damage.

bend con rods are the result of using to much ether that pre ignites before TDC,driving the crank shaft back against the starter.

The 6.2 in my Waldon(see sig) gets a sniff of ether every time i start the thing for the 10 yrs since i swapped it in with no problems.
The glowers are manually controlled and still work too,but the single batt i use drains to much for both glow and cranking with a cold engine.

 

[tammlyn]

ether

i was a mecanic in the rental industrie and used ether quite a bit and installed many kits on engines,detroits cummins,cats,john deere,deutz, used properly i never had issues,i have seen equip. returned were customers used ether and they had done serious engine damage,hatz diesel engines with 30:1 compression would blow the cylindre head right off the engine and in some cases customers were injured by flying engine parts,be careful thanks

 

[bison]

i was a mecanic in the rental industrie and used ether quite a bit and installed many kits on engines,detroits cummins,cats,john deere,deutz, used properly i never had issues,i have seen equip. returned were customers used ether and they had done serious engine damage,hatz diesel engines with 30:1 compression would blow the cylindre head right off the engine and in some cases customers were injured by flying engine parts,be careful thanks

Did'nt these 1 cyl Hatz diesels use a start wick(or whatever they where called) in a holder in the head.
I used to use a burning cig butt to start them when ran out of wicks.

 

[tammlyn]

yes your corect they used a wick it looked like the candy cigarette but out of material but in the rental ind. you get a lot of yahous that claim they know everything,but after blowing the head off the engine and they got the repair bill they were more careful