Newb question: IDI vs. direct injection

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Nov 21, 2008 | 05:37 AM

#16

FORD MEGA CAB!!!

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From: Guymon

And most (if all) the big diesels in semis don't have glowplugs or heating aids.. They seem to start great. some of The older mack engines seem to have a little trouble when it gets below 20 degrees but a little either solves that. The ISX cummins starts geat in very cold weather with no glowplugs, htr grid, either or any other aids. I wonder what the deal is??? And they don't have a compression release...

Nov 21, 2008 | 07:56 AM

#17

smokey98

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From: Sylva NC

Its funny, I was having this conversation yesterday with our mechanic right before quittin time. I was braggin on the new batteries and glow plug setup (beru/motorcraft plugs and push button) that I have now compared to last winter. I told him I went out in 20degs held the plugs on for 10 sec and then 5 sec more and spun it over for 3 sec and it started right up. He has an 02 dodge and in turn bragged on it starting at 20deg temp as well. He said he jumped in and turned the key not thinking to wait on the wait to start light to go out and it fired right up about as well as a gas motor. I beleive him cause I have drove plenty of big trucks that will start like that but have no idea why. I hope this thread continues so maybe I can teach him how it works.

Nov 21, 2008 | 09:34 AM

#18

ghunt

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From: Clarksburg WV

I started my truck this morning, for some reason the block heater didn't come on (my timer said today was saturday for some reason, not sure how that happened), it was probably about 28 degrees. It cranked over a few times and was a little slow getting going (as can be expected) but it started just fine.

Why does it feel like there's something special about firing up a cold diesel and listen to it clatter to life?

Nov 21, 2008 | 10:53 AM

#19

DeepRoots

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From: Douglas, Georgia

i work on 2 stroke detroit and emd diesels...
they are direct injection and extremely easy to fix/work on.

The only real difference between IDI an DI is where the injector is at.

IDI's tend to be able to burn a wider variety of fuels because injection atomization and penetration are not as critical as with a DI. These and many other of the characteristics described in this thread are engine dependent..... certainly not specific to one style or the other.

Drew

Nov 21, 2008 | 02:33 PM

#20

hairyboxnoogle

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My grandpa was tellin me that older heavy diesels have higher compression, thats why they start easier. But i dont see a difference really between 22-1 and 24-1. I know our pete doesnt have the reliefs. and neither does our F-8000. (CAT 1160) and they both will fire right up after sittin for six months or better when its below freezing. Just put your foot in it half way, and crank. They will both start within 10 seconds.

Nov 21, 2008 | 08:56 PM

#21

Dave Sponaugle

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From: Nutter Fort, WV

Compression ratio and cylinder volume have a big affect on how well an engine starts when cold.

In line engines have longer strokes, so the air in the cylinder has longer to heat up on the compression stroke.

Big engines have more air in the cylinder, so even if the cylinder walls are cold, the air in the center of the cylinder will be hotter.
This also works for the inline engine.

5.9 liter divided by 6 has more air per cylinder than a 7.3 divided by 8 does.

We have 2 3406 Cat's and a 270 Cummins in dump trucks.
They all start OK down to about 20 degrees, but if it goes below that if they are not plugged in, no use to waste your time trying to start them.

Nov 21, 2008 | 09:17 PM

#22

catfish101

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From: KY

The DI engines hold the heat generated in the cylinder bore. The heat in the cylinder bore ignites the fuel. An IDI engine doesn't get that benefit, The heat in the piston and cylinder wall doesn't help much because the fuel is ignited in the chamber which is in the head. The air looses to much heat when it leaves the cylinder bore and moves into the head.

The older engines like the Cummins motors had compression releases because they, believe or not, hadn't figured out how to make a starter. It hasn't been that long ago that "we" figured out that electricity moves along the surface of copper not through the core. When they started making starters with smaller diameter wire and were able to use longer pieces for windings did starters get stronger.

Also at around the same time "we" realized electricity moves from positive to negative. It was thought that it moved from neg to pos. hence positive grounds.

We still, to this day, have allot to learn about electricity.

Nov 21, 2008 | 10:24 PM

#23

Dodge/Cummins

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From: Sweet Home, OR

Another anomily is that my Cummins can sit for ANY length of time and any weather conditions and you just BUMP it and it starts.
My Dad's '97 Cummins you have to actually crank about as much as a Power Stroke to get it to start.