I was wondering what the back pressure should be on 7.3l IDI non-turbo?

[Joseph Davis]

Yea I agree, I am saving my money to buy a mini-moose pump and hopefully injector to match but that will be in early June. I am going to tear the heads off soon but got busy with other projects so postponed for a week or two. I will check timing when my meter shows up and post what I find. Thanks for the Help.

 

[Slade]

Mine was smoking and I changed the the CDR, No more smoking.

 

[Joseph Davis]

Hey Guys got my timing meter, I was about 3/4" off, now the truck just has black smoke but all the light gray to bluish smoke is gone. She will roast the tires now but the amount of black smoke is a little on the high side. Now what I am thinking is the person who adjusted the timing went by ear. The truck is way more stable at Idle but when I floor it with a fast stomp to much black smoke. Now can I lean out the injector pump by using the IP chamber screw. I see most people turn it up for more power but is it possible that they turned it to far in and increased it way to much fuel?

 

[Joseph Davis]

Mine was smoking and I changed the the CDR, No more smoking.

Yea that was the first thing I changed and my truck came alive after that. But the light gray to blue is gone because the pump was way out of time. Now the truck runs great but a little on the black side on peddle mashes. thinking about leaning out the IP and see if I can find that sweat spot. Thanks for the input

 

[gnathv]

What does it do at top end? You’ll have black smoke till the air catches up. At higher rpm does it still smoke? If you turn Fuel down too much you’ll run out of Fuel in higher rpm. Stomping on it produces smoke, rolling into the throttle produces power.

 

[Macrobb]

What does it do at top end? You’ll have black smoke till the air catches up. At higher rpm does it still smoke? If you turn Fuel down too much you’ll run out of Fuel in higher rpm. Stomping on it produces smoke, rolling into the throttle produces power.

This only applies to a turbocharged engine. N/A, you always have as much air as you are going to have at any given RPM, and the higher the RPM, the less air(per revolution) is available.
Turn the IP down till you only get a light haze at full throttle, and that will be best for your setup.
Or... install a turbocharger and turn that fuel into power!

 

[gnathv]

When you dump the fuel it smokes until rpms increase. There’s a lot of air at idle, there’s a lot more at full throttle.

 

[Macrobb]

There is /less/ air at full throttle. With a N/A motor. Above about 1600 rpm, the motor is struggling to pull air in and gets less air per cycle than it does off idle. This is why a N/A motor sucks at higher revs.
It's like a N/A gasser, except that the cam is 'tuned' for a low RPM torque peak.

Turbocharging makes things completely different, and you get /more/ air at high RPM, with the turbo spooled.

 

[gnathv]

http://www.asia.donaldson.com/en/exhaust/support/datalibrary/1053747.pdf

According to Donaldson, rpm is related to cfm. Na to turbo is a matter of volume effiency.

 

[Thewespaul]

No increasing boost increases your cfm because it is physically forcing more air into the engine.

 

[gnathv]

I agree with you, the turbo ve is greater which attributes to higher cfm

 

[Joseph Davis]

This only applies to a turbocharged engine. N/A, you always have as much air as you are going to have at any given RPM, and the higher the RPM, the less air(per revolution) is available.
Turn the IP down till you only get a light haze at full throttle, and that will be best for your setup.
Or... install a turbocharger and turn that fuel into power!

Yea I got a free 6.9 with a turbo a month ago, but I will use this 7.3l N/A learn more about the ins and outs before I move into the turbo world.

I agree, My truck has heavy black smoke at low RPM as rpm increases till it catches up, then no smoke. I think someone thought more fuel more power but they did not realize there is a balance to gain power. I really like the torque that this 7.3l N/A motor produces. I will try to lean this monster out when it stop raining on Saturday. Thanks for the great Advice

 

[Joseph Davis]

You may need to advance it quite a bit(you'll have to loosen the injector lines at the pump to keep it from binding), if you still don't have much clatter and still have blue/gray smoke(black smoke is a separate issue, and OK - timing would be 'nominal' to advanced at that point.

Thanks for the Great Advice worked like a charm.

 

[raydav]

How much cold start rattle is normal? I get a lot for a few seconds. Then I get it on acceleration. Then after about a half hour running around town it seems to quit. EGT never seems high during all of this. Timing is about +10 at 2K.

 

[Thewespaul]

How much cold start rattle is normal? I get a lot for a few seconds. Then I get it on acceleration. Then after about a half hour running around town it seems to quit. EGT never seems high during all of this. Timing is about +10 at 2K.

It’s because your timing is two advanced. Take a degree or two out of it