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Injector line coating

So I stopped by the shop again and measured the inj lines and they are different lengths so another myth busted. they measured from shortest 22 1/2 to about 24".

Well now, that's interesting.

Must be once the line is primed, the length doesn't have as big an effect (although there's probably some kind of tolerance on the length) on timing as I thought.

I've never seen anything in the programming that accounts for different cylinders/line lengths either....
 
I would think it would only be affected by the compressability of the fuel, which has to be very little if any
 
The fuel is a liquid therefore an 'incompressible fluid'. With such short line lengths, minimal differences in lengths, and low flow rates, I would think that loses are probably negligible if measureable at all.
 
I was also told the injector lines had to be the same length, if one was tuning for best performance, it may make a slight difference. Maybe like a change in resistor size from a #5 to a #9
 
if fuel is really uncompressable the only diff you should see is possibly the friction on the inside from bends etc. even then it would have to be really slight, it's not like it's free flowing or gravity fed
 
As it was explained in Fuel Systems training,
The timing is impacted time build pressure in the system after the delivery valve opens before the injector pop pressure is reached. Because there is always entrapped air, making the fuel compressible.

As it was explained in the class, don't F' up something you don't need to. So take it as a recommendation to not bend lines or make your own injection lines.

Its has been 20 years since I sat in that Fuel systems class. But as luck had it, I never end up working in full time shop.
Life put me in a better jig for the last 20 years, so this Diesel thing is a hobby now.

Regards,
 
Steel lines flex, balloon, with every injection pulse. This is why hold downs are critical to keep them from rubbing a hole in something or cracking. Dodge had an issue with this. So different lengths could have different timing from the balloon effect. The advantage to the IDI is the forgiveness in timing changes like you get from trying to grind the cam ring in the IP perfectly. So even if line length makes a difference it is forgiven; even possibly corrected in the cam ring or elsewhere. I doubt that kind of precision is available in our system though.
 
The only broken inj lines i have seen on diesels beside a interference rub trough leak(can be fixed with carefull brazing) was lines broke/cracked at the fittings.
 
I've always thought not bending the steel injection lines had more to do with fatiguing the metal and subsequent cracking when put under repeated pressure cycles.

Thats true but they are put under tremendous stress just bending them in the factory bender, moving the line a couple inches won't hurt anything
 
Thats true but they are put under tremendous stress just bending them in the factory bender, moving the line a couple inches won't hurt anything

Could be.

I have no idea if they're formed hot or cold, filled or empty, etc....

Most likely just formed and installed from plain stock.

Can't see GM spending any more money than they had too....just not they way they roll.....
 
Steel lines flex, balloon, with every injection pulse. This is why hold downs are critical to keep them from rubbing a hole in something or cracking. Dodge had an issue with this. So different lengths could have different timing from the balloon effect. The advantage to the IDI is the forgiveness in timing changes like you get from trying to grind the cam ring in the IP perfectly. So even if line length makes a difference it is forgiven; even possibly corrected in the cam ring or elsewhere. I doubt that kind of precision is available in our system though.

I would think if the lines really did balloon with every pulse that they would fail regualarly from metal fatigue. The actual dia of the hole in the center is fairly small (as in lots of wall thickness) the hole you see at the inj is actually bigger then the rest of it.
 
Inj lines do tend to pulse some. Some timing tools (line clamps) rely on this pulse to trigger a timing light.
 
so then what keeps the metal from fatigueing?

Every material has a designed fatigue load.

Basically, the amount you can "work" a material and still have it return to it's original shape/spec/form.

TTY head bolts are an example of this.

As long as you don't exceed the yield point, the material should last almost indefinitely.

Assuming the OEM got the specs right for the design loads of the material in the first place....:rolleyes5:
 
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