What exactly is indirect injection. I was under the impression that all diesels were direct injection. Is one better than the other?

 

Indirect injection "indirectly" mixes the fuel by mixing the air and fuel in a pre combustion chamber (similiar to the mixing chamber on a cuttin torch) before the it gets put into the motor. IDI is quieter than DI, but DI makes more power (Don't know why), but are more expensive to fix, IE injectors for a IDI are $20-$50, while Injectors for DI's run $350-500. IDI's run mechanicaly, so if the alt goes out while your chuggin along on a long trip, no biggie as long as you weren't listenin to the radio, while a DI is dead without electricity.


Others, will chime in but thats what I've learned to this point (hey, I've only been a IDI owner for less than amonth now)

 

IDI is also easier to fix. All injectors and glowplugs out outside of the valve cover where the PS you have to remove the valve cover. The IP is easy to remove as well. IDI requires 1 wire to run, 12V to run (will continue to run on voltages down in the single digits but not sure how far down) Its just to hold the fuel shutoff solonoid open. It requires no sensors to Run. They are there for your guages and glowplug system.
The Powerstrokes a great motor but as for ease of maintanence, less parts, and cheap parts, the IDI is hard to beat.

If you want, go to this link.

Diesel Technician Society

If you go to this link, click on the 93-94 turbo. Its an IDI engine with a turbo on top, otherwise setup almost Identical to the N/A. It also has the hp and torque charts comparing N/A to Turbo IDIs. Its a somewhat a big file and opens in Adobe Acrobat reader. When it opens in the window, click file, save a copy, then you can pull it up quickly nextime. by saving it to your HD.

 

Dean88 is correct about the terminology that Direct injection means the fuel is injected directly in the cylinder by the injector and in in-direct injection, the fuel is injected into a precombustion chamber.

You can have mechanical or electronic direct injection, you could have either of in-direct injection too but I am not aware of any manufacturers doing that because it is just not necessary with higher injection pressure. Direct injection engine injectors are fairly cheap for mechanical injected diesels too it is just the Powerstroke heui injectors that are so expensive. For example Cummins is direct injected , and you can buy a set of 100hp injectors for $450, that doesn't seem too bad.


You can make a lot of power with an IDI but they are not quite as efficient as direct-injected because you loose a little bit of efficiency through the precombustion chamber. Also Direct injected engine tend to be easier to start. I had a 560 with a factory diesel that was IDI (D282) that you had to use the glow plugs to start no matter the temp it seemed, but when I switched that out for a Direct Injected Diesel engine (German Neuss D358) it starts now on the coldest days without much trouble and no glow plugs at all.

Dean88 is also correct about the fuel being mixed in the precombustion chamber, if you will notice the IDI have what looks almost like a Gasoline piston while the DI motors have a combustion cup (looks like a reverse teardrop) in the top of the piston that cause a swirl in the chamber and make the fuel mix with the air better , negating the need for a precombustion chamber. The injection pressure is also higher with direct injection than in indirect injection wich allow the diesel to atomize better and mix with the air more effectively.

The reason that an Indirect Injected Motor is quieter in some case is the same reason that a pilot injected diesel engine is quieter , you have two smaller combustion events as compared to one big one with conventional direct injection. The first event in IDI is in the Precombustion chamber and then the second event is in the actual cylinder. The energy burnt in the precombustion chamber is wasted and the only thing it really accomplished, besides fuel mixing is heating of the coolant and this is why IDI are less efficient.

 

in anuitshell IDI is low buck and low tech
DI is high dollar and complicated

 

This has been discussed before and what the guys are saying is correct.

There are really three different type of designs. Direct Injection, Indirect injection that is broken down into two different designs. Turbulence chamber and pre-combustion chambers. These 6.9's and 7.3's are actually, technically, turbulence chamber engines.

The main reason for the power differential between a DI and IDI engine, mainly a turbulence chamber version, is the compression ratio. These IDI's have quite a bit higher ratio. Remember when an engine is going into it's power stroke and compressing air and fuel that consumes power from the previous stroke. Basically they take more power or energy to maintain themselves and that leaves less to go out to the rear wheels. You can also through other factors in but the main one is the ratios. The ratios may seem close but when applied they are very different.

Let me say this also. You have heard about people changing compression ratios in gas engines when building higher performance engine. It helps up until a point then it gets to a point that what you gain in power on one stroke you loose in the next so you quit getting extra.

 

You all are looking at this wrong, Direct Injected Diesel engines are not any more complicated or expensive then an Indirect Injected Diesel engine. It is soley the fact that the Newer Direct Injected Engines are all Electronically controlled that makes them so expensive and what some would say is complicated and is getting more so with everything new engine made. Mechanical Injected DI engines are very simple and fairly inexpensive to work on like I said the cummins is a DI engine and you can buy 6 sets of 100 hp+ injectors for less than what a set of OEM injectors cost for a powerstroke. It is not the IDI vs DI that makes them expensive or complicated to work on , it is the Mechanical vs Electronic.

Also a mechanical Direct Injection Diesel Engines only requires one wire (if even one in the case of a lot of engines that have a cable) to make it run just like the IDI motors in our fords and once started you can remove all power supplies and as long as there is fuel in the tank it will continue to run. Why do you think most people choose the early cummins pre-98 when doing a cummins swap, it is because of simplicity they only require one wire to run once they are started, these are Direct Injected engine, very simple and relatively inexpensive to work on.

 

i personally prefer the idi's for the simplicity and lack of sensors and various electrical junk and the WAY cheaper parts.ill take a small power loss for durability anyday

 

That sound good to me!

Thanks alot guys. That cleared it up for me.

 

Well, I assume people think of the Powerstroke when they think direct injected (I do), and besides the electronics on the Powerstroke there's also the HEUI injector setup, which is very pricey to do anything with and adds another level of complexity to the engine.

 

91f2504x4 is right, but so is everbody else.

Being on a Ford site I would expect the question was directed (pardon the pun) to the Power Stroke as THE direct injected engine.
Since I'm a Cummins owner I think of Cummins first as the direct injected motor.

Everyone is right in the fact that the computer controlled motors are the complicated ones that are expensive to repair.

The '89-early'98 Cummins (as found in Dodge trucks) have another advantage for simplicity: they have NO glow plugs.
They use an intake air heating grid, kinda like a basket weave of toaster heating elements in the air-intake stream.
It seems to be a more fool-proof set up than glow-plug systems. I've never heard of anyone having any problems with them. Plus they do a good job of helping to heat the motor after it's started with out burning itself out.

 

I'm impressed with the grid heater on the cummins. Seems to work really good.

Our flatbed truck at work has a 12V cummins in it, it does not have a block heater, and we've started it in just about any temperature down to about 10 degrees I think with relatively little problem.

 

Is there anyway to put a cummins grid heater on one of these idis?

 

IMHO, the "toaster" sucks. Gimme glow plugs anyday, w/ good maintenance theyre much more effective. We have the toaster in a GM Topkick>> worthless. The cummins does seems to work a little better tho. On a side note, why do our pickup diesels require heating aids, where say a cummins in a 69 pete' does not?

 

There differant now but the cummins in 69 had compresson releases spun the motor real fast then put the compresson to it and wasn't real good in cold weather.(either)