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Is black smoke due to restrictive exhaust manifold?

5819 Views 48 Replies 7 Participants Last post by  Tickford
First post on here, and I dont like jumping in just for info. So here is a bit of background.
I was working in Bougainville as a Stock Inspector back in the 70,s when I found this Forward Control Land Rover down the bottom end near Buin.
My wife and I rescued it for a slab of SP beer and towed it back to Kieta on an A frame behind my old diesel wagon.

We got the 6 cyl going and used it for work then when I finished my contract in 1980 we took it to NZ. NZ did not work out so we moved to the Sunshine Coast in Qld
Australia. There I fitted a Perkins 6-247 and used it towing a skidsteer on a semi trailer.
In the 90,s I gave it a refit with a 4BD1 and an LT95 gearbox. I also fitted Salisbury axles front and back with Maxidrive difflocks. and a camper back.

Tried for pics but I cant on first post. So more later.
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What have you done to the injection pump since fitting the turbo? The 4BD1 (non turbo) doesn't have a boost compensator to limit fuel until the turbo spools up, so black smoke before spoolup is tricky to avoid. The A pumps we have run a fuel plate inside the governor which sets fuel based on rpm. This can be modified to reduce fuel at lower rpm to limit smoke but I haven't tried doing that.

I would look for air intake restriction as the source of your high EGT and black smoke while still in the shed.

For your exhaust manifold. The size is fine, the shapes are awkward as the Isuzu ports are rectangular and the pipes are round. A better design if you keep using pipe fittings is to use elbows exiting each port and trim them into the manifold tube so all the pulses are pointed in the exit direction. Sort of like a row of r's. rrrrr

Are you the same Keith from AULRO who once lived in my home town?
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Came home early today to have another play.
Took off the pipe from inlet manifold to outlet of IC.
Started up and revved to 2500 odd EGT went up to 500C odd and still black smoke. I cant see any obstruction in inlet and its got good suck when holding hand over the pipe.
However, revving up and holding my palm over the IC outlet its easy to block it off and the wastegate rod does not move.
I would have thought 10 pounds or so would be harder to stop and if it was getting 10 pounds would not the wastegate rod start to move. I am still thinking manifold or something wrong with the turbo.
Does sound like something is up in the exhaust side. Time for some exploratory surgery I think.
Went for another run after removing both engine covers. I put a bottle and hose onto the WTA coolant overflow and the coolant is not coming from there.Still investigating.
Put my hand held electronic temp gauge on the inlet and outlet to the WTA radiator and both were the same temp at 33.6 C.
I thought it would have been hotter.
Terrible screech coming from somewhere from 8 PSI boost getting louder to about 15 then stops as boost continues up to 20.
Slowing down as boost drops there is a quick squeel as it goes down past 10 PSI then nothing to zero.
Is this what is called turbo whistle?
It really is awfull.
I had loose nut holding the turbo to the exhaust manifold that sounded like my turbo was going to explode. So check exhaust side too.

Turbo whistle climbs in pitch as the turbo boosts more and flows more.
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I am finding more and more references to drive pressure but not much info on how to measure it. As seen in the photos my custom manifold is made of stainless T,s with the turbo at the back of the engine. Then the exhaust from the turbo is a mandrel bent U then a 90 then straight 3 inch all the way back. No muffler.
Should I be concerned about drive pressure? If so how do I measure it?
To measure drive pressure you need a metal line off the exhaust manifold getting far enough away to lose conducted heat. Then you need something in the line to damp out the pressure pulses. A small restriction can work.
A boost gauge can work well as long as it's got enough range.

You'll want a gauge that can measure double your expected boost. It should also be possible to run an electrical gauge (oil pressure gauge etc) to avoid running exhaust lines into the cabin.
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Would an oil pressure gauge with the thin copper tube from the manifold to gauge work?
Then I am not sure what I am looking for. Some posts I found have higher drive pressure than boost and some lower. What is normal and what might I see if my manifold / exhaust is restrictive?
Yes and that's what I've done in the past. I coiled the line to absorb vibration better.

Turbos feed off heat and it's completely dynamic. When your exhaust and turbo is cold you'll see the highest drive pressure, as they warm up they get more efficient and drive pressure drops for the same boost.
My 4BD1T last time I measured it (about 10 years ago and I've had a lot of changes since).
Accelerating cold, up to 40psi drive for 20psi boost.
Sustained load at 2000rpm with EGT above 650C, 18psi drive for 20psi boost.
Flat road cruising 2000rpm, EGT 420C, 12-13psi drive for 8psi boost.

As rpms climb and wastegates open the drive pressure climbs to maintain boost. This is completely normal and why bigger turbines deliver more top-end power.
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Well I am 77 now and the truck is still going, however I read somewhere I should have re torqued the head. This I did not do. Should I do it now and if so what is the process?
How many km since your install? Is everything still behaving?
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