Engine/Transmission (1994 - 1998) How much smoke to expect?

[CStansbury]

I returned yesterday evening from the maiden voyage in my new truck. I drove 400 miles to and from WV. It was a good trip to check my trucks performance unloaded and lightly loaded on the way back. I had a strong headwind for a lot of the trip to WV as a front was coming through and then for part of the trip back to VA. The truck averaged 16mpg hand calculated with a 65-75 mph speed. The right foot was a 7 on the heaviness scale. I was very pleased with the power on the big grades. It passed and accellerated with ease. I am curious about the smoke levels I should expect. The truck is stock except for a BHAF, stock sized straight pipe and what I believe are 215 injectors. Under mild to medium throttle, there is a little haze. Under heavy throttle it starts to smoke pretty good around 2200 rpm and with the throttle matted at around 2300-2500 rpm it will really roll the smoke. I was passing a tractor trailer in a hurry and in the lights it looked like I about blanked out the highway. Is this what would I should expect with a 175 pump and 215 injectors? I don't mind the smoke, but I just want to make sure I am not wasting too much fuel. Any suggestions on AFC adjustment or fuel plate location? Thanks for any tips!

Chris

 

[Johnstra]

My 98 behaves exactly the same way. From what I gather it's normal. Seems a little more air is needed at higher RPM WOT if you want to get rid of the smoke. The AFC only controls fueling before boost kicks in so it won't effect the top end smoke you're seeing. I guess you could pull your plate back a little but you might lose more power than you like.

-john

 

[CStansbury]

Thanks John. Definitely don't want to lose power so I'll leave everything as is for now and enjoy the smoke show After my gauges go in, I am planning on a 3K GSK, a #5 plate, and a 4" RipRook straight pipe kit. I'm guessing this will increase my smoke even more at certain throttle positions. I need to meet up with a few other 12v folks to see what "normal" looks and feels like. I am looking forward to meeting up with the guy that bought my stock 3rd gen to see if I can outrun him after I do some BOMBing

 

[K5IP]

If you have a boost pressure gauge, it would help to know what boost you are seeing under these smoke conditions. As you already suspect, Lots of smoke means not enough air to burn the fuel you are delivering.

If you are only running stock boost levels, a boost elbow may be a good fix.

I also run a 95 with 215 injectors on a 175 pump and it is very clean under full load. With the boost elbow, my boost has increased from 16 psi to about 20. The addition of a 3KGSK allows the boost to increase to about 25 PSI due to the added rpm.

These conditions exist using the stock plate.

Rog

Rog

 

[Matthug]

I don't think you have 215 injectors, unless you have fuel plate mods anyway. My 94' barely smoked at all until I ground the stock plate. When I had the stock plate slid foward (before I ground it) it would let out a light little puff but only if I floored it and only at low RPM's. 215 injectors wouldn't make that much of a difference in smoke, they are still stock style injectors. You either have larger injectors than you think or else plate modifications.

I would start by pulling an injector and checking the part number, find out exactly what you have. From what you describe it sounds like they are 370's. The smoke pretty much doesn't clear up whenever the throttle is held, the fuel is not fully atomizing because of the wrong spray angle of the injector. I have the same problem with my 300 injectors, even with running 38 PSI boost it doesn't' clear. But if they are 215's, I'd next take off the AFC housing and check out what plate is in there.

 

[CStansbury]

K5IP, I haven't got my gauges in yet. I am going to order a boost and EGT today, so hopefully I'll have them in the truck next week. That is interesting that your 95 with 215 injectors seems to run clean.



Matthug, you may be right. They might be larger than 215s. The PO just said that they were larger than stock and that he thought they were from a later truck. His PO actually had the injectors put in by a Cummins mechanic friend of his. I really need to pull an injector this weekend to get the numbers. That would help a lot. The truck does seem to have the cold start smoke Like I have seen others mention. Starting the truck without the heater plugged in and without any throttle produces just a small puff of smoke and a decent idle. If I try to take off before it evens out, it will fill the parking lot with smoke. Even after I can take off, it will roll the smoke at around 2000 rpm for the first few miles. After a couple of miles, it will be smooth and strong, only smoking at higher RPM/boost levels.



I looked over the pump. Everything seems undisturbed. The breakoff screw is in place. Of course someone may have been in there, replaced the screw, and then shot some paint on it. Won't know for sure until I pull it apart. Hopefully I can get a look at an injector this weekend and go from there.



Thanks guys,

Chris