smoke test

[Peter J. Bierman]

Hi, it's been a while since my last visit couse of home inprovement issue's but I am stil alive and running the twin turbo engine.

At the last anual check the truck failed the smoke test by 350% !!.
Weird thing is, last year it has 1.25 K value???? some smoke messurement stuf.
This year 5.5 and later on 4, wile 3 being the norm.
Nothing has changed to the engine other then an 4L80E transmission to replace the TH400.

The smoke test is revving the engine up to the governour and keep it there for 1 sec.
The theory is to use the mass of the rotating parts for a constant load so the load is the same for every test on a particular engine.

With the new tranny I run much lower RPM's then before so I figgured old soot comming out, but drive 200 miles in 3rd did help a little from 5.5 to 4 but that is still 3 time more then last year.

So something else is wrong, right?

I think my fuel lift pump is poor and low feed pressure give more advanced timing and moor smoke, had this before a few years back but that was with the stock engine and loss off power.

Maybe someone can confirm my thoughts or have other idea's about this.
Neeles to say that fuel and air fiters are clean, intercoolers won't make a differance when standing stil.

Thanks, Peter

[moondoggie]

Good Day!

Do you pull any kind of big trailer? Can you drive truck & trailer in / through the testing facility? I'd be tempted to go find some big hills, pull the trailer up a few of them, get 'er good & hot & cleaned out, & make sure I arrive at a time when there will be no delay in starting the test. Drop the trailer a block away if necessary; hook back up after the test.

"The smoke test is revving the engine up to the governour and keep it there for 1 sec." If they make you hold it to the floor, I'd also consider a block of wood under the carpet right under your footfeed (accelerator pedal), where they can't see it. I'd put the block of wood in just before arriving at the testing station. I'd make the block a thickness that would barely allow rpms to get close to the governor, if that allows enough power to get in & out of the testing station. (I think I'd smack anyone that told me to do this test to my truck. )

Merry Christmas!

[JeepSJ]

Do they run it on a dyno in high gear, or is the trans in park/neutral when they do this? If they run it on a dyno (like they do here), then have them run it in 3rd gear.

Can you get biodiesel in your area? I have heard that it will significantly reduce smoke compared to running straight diesel. Also, try adding a double-dose of Power Service (or whatever cetane booster you like to use).

[Peter J. Bierman]

You're right, this is the most not proving anything test, but it seems to be some European gouvernement law and you have to let them do the test.
Thing is that other then the hillrace ( Seen any in Holland lately ) the woodblock won't work.
within the range off the throttle there will be more smoke than at the governor, were fuel is cut back to maintain max RPM and the turbo's will put out some boost.

The test gave 1.5 last year and now 4 so there most be something wrong I guess.
How about the feed pressure timing thing, any ideas?

Peter

[Peter J. Bierman]

Tried a fuel additive but seems to help a little from 5.5 to 4 after the cleanout run.

The test is stationairy, full throttle in neutral.
Normaly most diesels pass if in reasonable condition, mine is in better shape than that so it should not be a problem.

For the moment I stick to the timing being to advanced wich will couse more soot than normal, I'll check this weekend.

Peter

[DmaxMaverick]

"Hold my beer and watch this...."

Tee into the vacuum line somewhere and run it straight to the wastegate actuator (or better, wire it shut if you think they won't find it). It will not allow the wastegate to open (much, unless you wire it closed) during the test, giving you the most boost (most O2) during the test. Don't drive it anywhere like this with a heavy foot, load on, or trailering, and don't do any full throttle in gear runs with it (it will overboost, and set a DTC and SES, which will fail the test). The short term WOT burst won't harm the engine while not under load. If the test results don't change, you need to find out why you are pumping in more fuel than there is O2 to burn it.

[arveetek]

I don't think Peter's turbos have wastegates, do they? I know for sure he doesn't have an ECM or any DTC's to set and definitely no SES lights....

I hardly have any smoke when running biodiesel, but when I switch back to #2, the black smoke comes back. So switching to bio might work, if it's available to you.

Casey

[Peter J. Bierman]

Well, I do have two wastegates but since I took off the control tubes, they don't do much....
The only computer is the transmission controller, wich will not light any lights I guess.

Before switching to alternative fuel, I'll check the timing issue I mentioned before, funny you need more fuel to get less smoke

[moondoggie]

Good Day!

In the name of keeping me reputation for stupid suggestions (see above), how's your air filter situation?

"...funny you need more fuel to get less smoke..." Maybe someday you could explain this one to me - I've always found it to be the opposite.


Blessings!

(signature in previous post)

[Peter J. Bierman]

Moondoggy,

First the filter thing, as I stated before all the filters are clean/new, it was the first thing I looked.
This said, I have to admit that I overlooked one, inside the electrical prime pump there is another filter wich I checked today and guess what? Full with dirty stuff.
I replaced the filter and the feed pressure came up again and is now stable at 12 PSI.

Now for the more fuel to get less smoke:

If the feed pressure is far to low like 2 or 3 psi, the internal hydraulic timing divice of the injectionpump can't do it's job properly and the timing get's more advanced then normal.
More advanced timing gives more black smoke, so that's why.
My pump is pretty advanced as it is, so more advance and I'll get in the erea of not passing the smoke test and even the danger area of hurting the engine.
I got to this couse the engine hardly reacted to powering the HPCA soleniod so there was hardly a pressure drop when powered.
( the soleniod is not used on cold starts but on a manual switch.)

Hope this answers your question.

I try the smoke test again tomorrow.

Peter

[moondoggie]

Thanks! I'll get it some day...

[Peter J. Bierman]

Moondoggy,
nevermind if you get it or not, remember that it works.
Passed the test today with 2.7K with 3.0 being the limit, came from 4.0 so thats what your timing does.

Peter

[6.5NOVA]

sooo.. an almost smoke-les twinturbo chevy blazer.....

[Peter J. Bierman]

It still smokes a little, butt nothing a pair off good headlights can't penetrate.....
I have the feeling it runs better to.

Peter

[john8662]

How much boost does the TTD run currently under load and WOT?

Just curious.

I'd hate to have to pass that kind of test, full throttle in netural one some engines isn't going to be smoke less. Especially those with the 4974 injection pump or tweaked 4911 pumps.

Glad that the test has now been passed, fuel pressure, or a lacking will cause timing issues. I'm also wondering good ways to diagnosing possible fuel return issues, increased pressures, how much restriction gets us into trouble.

I gotta get a Fuel PSI gauge installed.

[JohnC]

... full throttle in netural one some engines isn't going to be smoke less. Especially those with the 4974 injection pump or tweaked 4911 pumps...

Why not? It's running under no load against the governor. How much fuel is it going to be delivering?

[john8662]

Why not? It's running under no load against the governor. How much fuel is it going to be delivering?

I guess I'm thinking more of stabbing the throttle until it gets to the governor, flogging it. You're right that if the operator just gradually takes the throttle up to the where the engine revving at the governor, it shouldn't smoke.

[JohnC]

Right, big puff of smoke until it hits the governor.

Don't do that!

Besides, I'm always nervous the governor won't catch it in time...

[Peter J. Bierman]

The whole idea is that the engine's own mass and the converter/flywheel is the load, they messure the from stationairy to the governor so more or less "under load".
Point is the test equipment is not realy made for big engines, biggest thing around for passenger cars is 3.5L I hve allmost double, so the messuring chamber is not happy whem I come along

Anyway I passed so the engine can have a rest till next year....

I have $2 fuelpressure gauge at the filters, it was wobling up an down between 3 and 10 PSI, now it's stable at 12.

Peter

PS: boost at wot underload is about 18 PSI, I cant really tell, gauge stops at 15, it goes a little furter.

[john8662]

PS: boost at wot underload is about 18 PSI, I cant really tell, gauge stops at 15, it goes a little furter.

Rock on! Same problem too, but gauge goes to 30