Early '91 now intercooled

[dshockley]

I just got done installing the banks intercooler in my 1991. I was very impressed with the way that everything went together. It is a really nice kit. Unfortunately, Banks sent me the wrong inlet tube so I had to cut about 2. 5" off of the brand new part. I will be calling Banks Monday and I am sure they will take care of me.



Anyway, to the question. . My truck is now stock with the exception of a K@N filter, a Banks intercooler and gauges. I have not made any adjustments to the pump. After driving the truck with the intercooler, in addition to a noticable power difference, it now smokes significantly more. Just a heavy black hazy. The addition of the intercooler and the new air filter dropped the WOT boost 5 psi (to 14. 5) and the WOT EGT 200* (to 800). I thought that the smoke was due to a rich condition. I also thought that the intercooler would have increased the charge density leading to a leaner condition. I have read all the posts in addition to the webpage that Genos has put together and I understand what each adjustment does individually, but do not understand all of their interactions. Banks recommends 120* CW on the power screw to "take full advantage of the intercooler". I am planning to add a 16cm^2 exhaust housing and the RR exhaust and plan to tune the pump after that so I don't want to change anything too much at this point, but would like to get rid of the smoke. Does the 120 CW sound like a good place to start? Any thoughts??



Thanks

Dan

 

[dshockley]

Well,



I followed Bank's advice and turned the power screw as far as I could (about 90 degrees CW). The smoke is gone. Why? I thought that increasing the fuel would increase smoke. Apparently the more I read and study, the less I know.



Thanks for any input,

Dan

 

[dshockley]

Surely someone can answer some of these pump related questions.



Dan

 

[J DeMaio]

Well, I'd say that you're more efficient now and producing more power cleaner with that intercooler. It cools the air and makes it so you can get more air into the cylinders which in turn, more fuel can be added to creat an equal amount of air and fuel, so it sounds as if you could use a little more fuel. That's the reasoning behind the intercooler, to supposedly give more power and create a cleaner running engine. Do you have gauges, what are they reading at?



Hope this helps,



John

 

[dshockley]

Yep, I understand how the inetercooler is supposed to work, I am more confused about how the smoke "works". The intercooler leads to more air in the charge, which in turn should produce a leaner condition. I thought that I should be seeing smoke when it is too rich? So I turn the fueling up and this reduces the smoke?



The temps and stuff made sense. 1000 f at WOT before ic. 800 F at WOT after ic. 900 F after ic and 90* on power screw. The boost started at 20, it then went down to 14. 5 and then back up to 15.



I am just trying to understand the interactions between the different pump adjustments better. My thought was that the lower boost probably resulted in a different fueling rate which lead to the smoke. That does not explain why the smoke went away when I turned the power screw cw.



Thanks

Dan

 

[McGivern]

Dan,

I'm no expert, but as I understand it you're not really gettting more air by adding the intercooler, you're just increasing the density of the air by cooling it.



From chemistry PV = nRT



Since the amount of air the turbo is pumping is the same (V), then a decrease in T means a decrease in pressure (P).



By adding more fuel and adjusting the pump, you can now make the turbo do more work, thus increasing V. This will add some T (even tough you're below what you were before), and therefore increase P some.



Depending on what exhaust housing you're running, that may be your next move. You'll want to consider running a 16cm housing. That should take your max boost back to 20 or so. You can also go to a 12cm wastegate, but to get the best performance there you'll want to switch to an HX35 turbo - the compressor side of that turbo is much better suited for that setup. It all depends on how much power you want and how much money you can spend.



Piers is a great resource on the turbo setups.



Hope this helps,



Mark

 

[JLEONARD]

It is not surprising that you have less boost after adding the intercooler. Cooling the air will decrease pressure.

Per a Cummins shop manual I have for a 6bta marine version, they say to expect a 4 to 5 psi drop across the intercooler.

 

[formula]

Just following up on the IDEAL gas equation. PV=nRT.

P - pressure

V - volume

n - number of moles of gas

R - universal gas constant

T - temperature



Here is my take on the smoke after intercooler situation. The purpose of the intercooler is to increase the air charge density. It accomplishes this by cooling the charge air that passes through it. Note that for a fixed volume of air, as the density increases, the number of molecules of air in that volume also increases. (as T decreases, n must increase to maintain a constant PV) Since air is 21% oxygen this means that the oxygen will also increase. So, increased oxygen means that you can run more fuel and still achieve a good burn with low temps and low smoke. This does not take into account the pressure drop accross the intercooler due to internal resistance to air flow. If your max boost after adding the intercooler is 5psi less than before, you're probably getting less air to the engine than without the intercooler. Less air, same fuel, smoke. Now when you upped your fuel it probably made the turbo spool up enough to overcome the pressure drop of the intercooler and now you get a clean burn. Suggestion... ... get a smaller turbine housing, you'll like it a lot

 

[glhs]

Just a thought

I did bypass my intercooler once w/some custom bent exhaust pipe. I gained 4# of boost but the truck made more smoke and was a DOG. Not only heat but also the fact you are asking the same size turbo to fill more area (intercooler and piping) at the same rpm may be why we loose boost when adding an intercooler.

Any thoughts?



I think it is strange that you made more smoke after the install. I've never heard of anyone getting more smoke after installing a Banks intercooler. I am also curious why that would happen.



Kurt

 

[formula]

The added volume of the intercooler is very small compared to the volume of air that the turbo forces through it. The pressure drop accross the intercooler is due to the air being forced through lots of small tubes and being cooled at the same time.



Still, the smoke increase business is a bit perplexing.



Dirty injectors?

AFC diaphragm?

Smoke screw?

Air intake blockage?

Lead foot?



Just a few ideas... .

 

[JLEONARD]

asking the same size turbo... ... ...



Not necessarily the same size turbo.

I say this because I just recently replaced my turbo with a new one.

The first one I got was mistakenly for an intercooled 91. At least that was what I was told and the following is based on that premise.

The intake fitting on the wrong turbo was much larger than mine.

Just to see if I could put my old intake casting on the new turbo and use it (saving me having to wait for shipment of the correct turbo), I discovered that the intake turbine was quite a bit larger and my casting would not fit.

So I think the intercooled turbo is designed to deliver more volume..... with the same exhaust impeller size.

(Perhaps I should have adapted the it to fit my truck??????)

 

[BCaldwell]

To get answers to your question try piersdeisel.com Peirs or Al can probably clear the smoke from this up bill