Question about black smoke and boost levels

[Diesel Fumes]

The previous owner left the metal guard on the smoke screw on my 86 TD Jetta.  I just removed it and turned it in a few turns.  I have a bit more black smoke now, but no where near much as I would like under WOT.  Problem is that turning the screw in about one turn caused my idle speed to jump to about 1200rpm.  Engine sounds like its racing at idle.  Should I compensate by backing down the idle speed screw?  Is there one other than the threaded rod that controls throttle position?  

Also, previous owner told me he turned up the boost slightly to around 15psi.  I don't know how he determined the boost level, but i'm quite sure its noticeable.  This is OK, but I want to turn it back down to close to stock levels since I don't want to do damage to my engine or turbo.  Will this reduce black smoke or make it easier to obtain black smoke?  I don't even know how to turn the boost back down so if someone knows, please post up how to do it.

I don't want to max out the power on my car because I know what that can do to the pump, rings, valves, etc.  I toasted my NA Golf's pump by getting too turn-happy on the fuel screw.  I just want to it to blow billows of black smoke at WOT.  Why?  I don't know.  Piss off tailgaters?  As it sits now it doesn't really blow much noticeable black smoke at all.

[zukgod1]

The previous owner left the metal guard on the smoke screw on my 86 TD Jetta.  I just removed it and turned it in a few turns.  I have a bit more black smoke now, but no where near much as I would like under WOT.  Problem is that turning the screw in about one turn caused my idle speed to jump to about 1200rpm.  Engine sounds like its racing at idle.  Should I compensate by backing down the idle speed screw?  Is there one other than the threaded rod that controls throttle position?  

Also, previous owner told me he turned up the boost slightly to around 15psi.  I don't know how he determined the boost level, but i'm quite sure its noticeable.  This is OK, but I want to turn it back down to close to stock levels since I don't want to do damage to my engine or turbo.  Will this reduce black smoke or make it easier to obtain black smoke?  I don't even know how to turn the boost back down so if someone knows, please post up how to do it.

I don't want to max out the power on my car because I know what that can do to the pump, rings, valves, etc.  I toasted my NA Golf's pump by getting too turn-happy on the fuel screw.  I just want to it to blow billows of black smoke at WOT.  Why?  I don't know.  Piss off tailgaters?  As it sits now it doesn't really blow much noticeable black smoke at all.

Well lets see here, you can turn the idle screw out to lower the idle after you turn in the Max fuel screw.

You didn't tell us what car we are playing with here so I'm going to go with the Jetta 1.6TD in your sig here, as far as turning up the boost goes all he could have done was either install an adjustable boost knob OR he turned up the max fuel screw OR did nothing and told you it was turned up. GET A GAUGE!!!
If you turn up the fuel you are turning up the boost, it takes fuel to boost period.

Your TD engine isn't going to blow black smoke like your NA engine did with the fuel screw turned in, the more you turn it in the more fuel you give the engine the faster the turbo spools and the more boost you will get.
Again GET A GAUGE!!


I hesitate to give you advice as it seems you just want to pump out black smoke. Don't get me wrong I like it as well but you have to understand that's unburned fuel coming out the tail pipe and the laws are getting more and more strict largely to do with people driving around blowing black smoke..
Just be careful please..

[Diesel Fumes]

The previous owner left the metal guard on the smoke screw on my 86 TD Jetta.  I just removed it and turned it in a few turns.  I have a bit more black smoke now, but no where near much as I would like under WOT.  Problem is that turning the screw in about one turn caused my idle speed to jump to about 1200rpm.  Engine sounds like its racing at idle.  Should I compensate by backing down the idle speed screw?  Is there one other than the threaded rod that controls throttle position?  

Also, previous owner told me he turned up the boost slightly to around 15psi.  I don't know how he determined the boost level, but i'm quite sure its noticeable.  This is OK, but I want to turn it back down to close to stock levels since I don't want to do damage to my engine or turbo.  Will this reduce black smoke or make it easier to obtain black smoke?  I don't even know how to turn the boost back down so if someone knows, please post up how to do it.

I don't want to max out the power on my car because I know what that can do to the pump, rings, valves, etc.  I toasted my NA Golf's pump by getting too turn-happy on the fuel screw.  I just want to it to blow billows of black smoke at WOT.  Why?  I don't know.  Piss off tailgaters?  As it sits now it doesn't really blow much noticeable black smoke at all.

Well lets see here, you can turn the idle screw out to lower the idle after you turn in the Max fuel screw.

You didn't tell us what car we are playing with here so I'm going to go with the Jetta 1.6TD in your sig here, as far as turning up the boost goes all he could have done was either install an adjustable boost knob OR he turned up the max fuel screw OR did nothing and told you it was turned up. GET A GAUGE!!!
If you turn up the fuel you are turning up the boost, it takes fuel to boost period.

Your TD engine isn't going to blow black smoke like your NA engine did with the fuel screw turned in, the more you turn it in the more fuel you give the engine the faster the turbo spools and the more boost you will get.
Again GET A GAUGE!!


I hesitate to give you advice as it seems you just want to pump out black smoke. Don't get me wrong I like it as well but you have to understand that's unburned fuel coming out the tail pipe and the laws are getting more and more strict largely to do with people driving around blowing black smoke..
Just be careful please..

Hi, thanks for the reply.

As for what car im playing with... Read the first sentence of my post  :lol:

I'll keep it as is for now and just adjust the idle speed down a bit.  I have seen pictures on here of TD's blowing considerable black smoke.  I was hoping for that.  I don't want it to be a constant smoke stack out the back, just when I want it to be.  

I'll look for the adjustable knob.  The previous owner said something about turning something by the turbo.  I never bothered to have him show me as it was dark and really cold when I picked up the car.

[Diesel Fumes]

High boost levels will not damage your engine, on the other hand, high temps will very quickly.  With a diesel, a higher fuel to air ratio causes higher temps.  LOWER boost levels increase the fuel to air ratio and so cause higher temps and so greater risk of an engine meltdown.  Higher boost levels actually increase the efficiency, increase the power and DECREASE engine melting temps.  It seems like almost everyone has it backwards.  There seems to be a fear of increasing boost, yet people "eff" with the fuel screw without EGT gauge and without concern.  :roll:  By increasing fuel WITHOUT increasing boost you seriously run the risk of melting your engine.  By increasing your fueling and decreasing boost, without a gauge to monitor the temps, you likely won't be driving a VW too much longer...  Also, as mentioned, the black smoke is unburnt fuel, inefficiency, expensive, un-environmental, is a visual clue that your running excessive EGTs, fouls your oil faster, fouls your turbo, et, etc, etc, etc...  There isn't an upside unless you think it's "cool"... While I can wholeheartedly support the desire for more power and can also wholeheartedly support the desire for added fuel economy, the desire to produce more smoke isn't exactly where I'd focus my attention.  YMMV.  Merry Christmas.  

Andrew

OK, this makes sense.  Thanks for clearing it up  

So if I increase the fuel screw, will this also increase boost?  Im in the clear if I do this right?  I want to install a gauge pod with EGT, boost gauge and oil temp gauge.  After I do this, what is the procedure for increasing my engines efficiency.  I have read posts on here that say to turn the screw in, but is it harmful to do it all the way in?  Its sort of natural to think that it wouldn't be.

With my NA 1.6, I turned the screw in all the way and also decreased the idle speed.  When I did this, it must have been overfueling.  The power was good, but the smoke was too excessive.  And it was a constant billowing, not just at WOT.

I want to try this but should I do it before installing gauges?  I have since turned the screw in one more turn and tuned the idle speed down slightly.  It still doesn't blow black smoke.  Just a small amount if I rev it high, although it is not enough to even be seen in my mirrors.  

Anyways, Merry Christmas to all.  And thanks again for your replies.

[jimfoo]

You REALLY want an EGT gauge before you mess with the fuel screw too much. While more fuel can increase boost somewhat, it is mostly regulated by the waste gate, or vanes in the case of a VNT turbo. You also want to install the thermocouple before the turbo.