Do IDI engines require gp's by design?
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Do IDI engines require gp's by design?
I'm kinda new to diesel engine repair but have learned a lot since acquiring my Ford 1986 6.9, 1988 and 1989 7.3 trucks all of which use glow plugs as a starting aid. I also have a John Deere 4100 compact tractor and John Deere 332 and 430 garden tractors that have Yanmar IDI engines with glow plugs. I also have two John Deere farm tractors that are direct injection that do not have glow plugs.
Do all IDI engines require a glow plug system to start properly? What is the advantage of an IDI engine over that of a direct injection engine?
Do all IDI engines require a glow plug system to start properly? What is the advantage of an IDI engine over that of a direct injection engine?
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Joined: Jan 2005
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From: Huntington Indiana
Most diesels in this size engine and smaller require glow plugs. Yes I have farm tractors which do not require glow plugs. Just a block heater for winter and sometimes a touch of ether.
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General answers to your questions........there may be exceptions...............
IDI's usually have glow plugs..............(all most a basic requirement in colder climates)
DI usually have intake air heaters.........(all most a basic requirement in colder climates)
advantages of IDI (usually)
can run on a lower cetane fuel than a DI much easier..........
lower emissions
much easier to build smaller CID engines
wider range of torque band...
just a little bit quieter (diesel knock)
if turbo, requires less boost to get equal cylinder pressure as DI
can be much farther out of tune and still run ok.............
advantages of DI (usually)
easier and Much cheaper to build in larger CID engines
lower compression ratio, makes for easier cold starts....
it is claimed to get better fuel mileage (rare case indeed)
crossbones
IDI's usually have glow plugs..............(all most a basic requirement in colder climates)
DI usually have intake air heaters.........(all most a basic requirement in colder climates)
advantages of IDI (usually)
can run on a lower cetane fuel than a DI much easier..........
lower emissions
much easier to build smaller CID engines
wider range of torque band...
just a little bit quieter (diesel knock)
if turbo, requires less boost to get equal cylinder pressure as DI
can be much farther out of tune and still run ok.............
advantages of DI (usually)
easier and Much cheaper to build in larger CID engines
lower compression ratio, makes for easier cold starts....
it is claimed to get better fuel mileage (rare case indeed)
crossbones
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From: KY
Yes and no. There are two types of IDI motors. Some have precombustion chambers and some have turbulance chambers. I haven't ever seen a turbulance chamber engine that didn't have glow plugs. There are precombustion chamber engines that do not.
There is a big design difference between a precombustion chamber and a turbulance chamber. Precombustion engines only send about about 30 to 40% of the compressed air fuel into the chamber and turbulance chamber engines send pretty much all of the air fuel into the chamber.
The glowplugs are a must on a turbulance chamber engine for cold starts. The reason is that to get diesel to light the air has to be between 1000 and 1100 deg. That number can vary some because of different types of fuel but that is the accepted number by most diesel motor manufactures. The reason that they need them is because the heat generated by compression in the cylinder area doesn't transfer to the turbulance chamber to start when cold. The cylinder area and the chamber aren't in the same piece of iron and they are seperated by a gasket. That is the key. The air looses it's ignition temp fast.
6.9's and 7.3's have turbulance chambers not precombustion chambers. The pistons are flat in them just like a gas motor where as the precumbustion engine and a DI motors will have a combustion chamber built in the piston.
They have added glow plugs to later DI engines to try to eliminate white smoke at start up and to help start on cold days.
Yes, we use the wrong terminology on the forum but it really doesn't matter. That is actually how it is but unless you are going on Jepardy it may not matter much.
One other thing to note. These engines, if they are in good shape, don't have to have the glowplugs cycle at every start up. My truck has been on a manual switch for 8 years and I don't cycle them everytime I start it up. During the summer I can go into work in the morning and go out at dinner time and it will start right up without cycling the plugs. I just know my motor. I guess that is why have had the same plugs in it for 8 years and they still are fine. They are AC 8G's.
There is a big design difference between a precombustion chamber and a turbulance chamber. Precombustion engines only send about about 30 to 40% of the compressed air fuel into the chamber and turbulance chamber engines send pretty much all of the air fuel into the chamber.
The glowplugs are a must on a turbulance chamber engine for cold starts. The reason is that to get diesel to light the air has to be between 1000 and 1100 deg. That number can vary some because of different types of fuel but that is the accepted number by most diesel motor manufactures. The reason that they need them is because the heat generated by compression in the cylinder area doesn't transfer to the turbulance chamber to start when cold. The cylinder area and the chamber aren't in the same piece of iron and they are seperated by a gasket. That is the key. The air looses it's ignition temp fast.
6.9's and 7.3's have turbulance chambers not precombustion chambers. The pistons are flat in them just like a gas motor where as the precumbustion engine and a DI motors will have a combustion chamber built in the piston.
They have added glow plugs to later DI engines to try to eliminate white smoke at start up and to help start on cold days.
Yes, we use the wrong terminology on the forum but it really doesn't matter. That is actually how it is but unless you are going on Jepardy it may not matter much.
One other thing to note. These engines, if they are in good shape, don't have to have the glowplugs cycle at every start up. My truck has been on a manual switch for 8 years and I don't cycle them everytime I start it up. During the summer I can go into work in the morning and go out at dinner time and it will start right up without cycling the plugs. I just know my motor. I guess that is why have had the same plugs in it for 8 years and they still are fine. They are AC 8G's.
Last edited by catfish101; Apr 24, 2007 at 11:23 PM.
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Manual plugs rock
I did the same manual glow thing on my 84 Mercedes 300SD using a lawnmower relay and homemade loom, same plugs (beru) for last five years.
The guys over on the Mercedes board gave me a snotty reception for this mod, funny thing is on that board EVERY winter there are dozens of posts about bad starting and glowplugs. That conroler costs about $270!
Steve
The guys over on the Mercedes board gave me a snotty reception for this mod, funny thing is on that board EVERY winter there are dozens of posts about bad starting and glowplugs. That conroler costs about $270!
Steve
