ATT Rolling Coal at 6,750'

[Big T]

Big Bear Lake, altitude of 6,750'. Standing start, no boosted launch, but stepping on it (click pick and it will link to video):



Going the other direction up a small hill:

 

[gnel]

Steve why are you making so much smoke? Are your boost # normal. We were up at our place in San Miguel de Allende (6400 ft) over Easter and mine wasn´t smoking at all.

 

[buddy]

Thats not a lot of smoke really. I can put out more than that at sea level if I wanted to. The ATT is a lot larger than the GM turbo so it will smoke off the line until its spooled up. Thats about what mine was like when in Colorado Springs without trying. My 3.42 gears and smaller precups probably have something to do with that.

 

[Big T]

That's a downside of the larger ATT turbo. It spools up slower, leaving you dumping fuel with no boost at start-up. It's more pronounced at altitude. I've had it parked on a steep incline while offroad. Went to take off with wheels turned sharply to get back on the trail and basically it just blew tons of smoke and barely budged because it was not developing power until the turbo boost kicked in. This happened at 8,000'.

It develops up to 17 psi boost when not towing. I've seen 18 when towing up a hill.

 

[Edzzed]

I used to get smoke like that but it was due to a leak on the drivers side donut gasket. I get a little smoke now, but nowhere near that. I am pretty close to sea level.

 

[Jorge6.5]

Well thats a waste of fuel. I just cant see my self running another non gated turbo. They dont work good in my area, i need boost/power sooner then that. My truck blows next to no smoke even under heavy throttle

 

[buddy]

Once it spools its doesnt smoke anymore, typically, mine doesnt running around empty on grades. Guys with 4.10 gears and L65 precups seem to have the most sucess with the larger turbos, because the RPMs climb faster and the larger precups (at least up to diamonds) seem to help get fuel burnt faster. There are not a lot of people that drive around above a mile elevation where air is less dense, so smokes easier. Its fine on passes and what not on highways at speed, just stop and go that it smokes.

 

[Big T]

My son's '95 has the stock turbo on it. When I had it up at altitude barreling up a steep grade, it blew black smoke almost throughout the rpm range. Still remember the switchbacks up to Cottonwood Lakes in the Southern Sierras. You go from 3000' to 9000' in a matter of a few miles. The '95 blew black the whole way and heated up badly.

I did a mileage test topping the tank off brimming at the fill spout and at 350 miles I'm right at 1/2 tank. That's about 16.66 mpg and that included a steep climb up the back route 18 to Big Bear Lake. So it's hardly wasting fuel. If I don't get into the pedal, it doesn't smoke even at altitude. A wastegate Would do you no good. They dump air at high rpm/boost levels. You need the boost and air at low rpms and no turbo does that. Only a mechanically driven supercharger could provide the needed boost at low rpm. Given the ATT's attributes at the rest of the rpm range, I'd take it over the stock turbo any day. Just the engine cooling effect from lower back pressure alone justifies the AT&T.

 

[Big T]

In the first video, note where the engine sound gets throaty towards the end of the run. That is the point where the ATT really starts to kick in and you can feel it taking off.

 

[gnel]

OK now I understand.

 

[WarWagon]

My 1993 GM3 would smoke on launch like that. Would clear up faster except at altitude. I had to turn the fuel down for altitude on the GM3. This is with the 4.10's. The 1995 3.73's do make a difference, but, it is harder to tell as the 3.73's also have the smaller precups.

 

[buddy]

My 94 with GM4 never smoked even at altitude, had it at Big Bear once, about the only high altitude it saw before putting ATT on.

BigT, did the 95 mostly smoke at low speed, crawling up a hill or something like that? With low boost off an on?

 

[Big T]

My 94 with GM4 never smoked even at altitude, had it at Big Bear once, about the only high altitude it saw before putting ATT on.

BigT, did the 95 mostly smoke at low speed, crawling up a hill or something like that? With low boost off an on?

Buddy, the 95 smoked on acceleration while climbing at altitude, thus my description of "pretty constant" as you're constantly accelerating out of turns. So yes, low boost combined with acceleration. Colby has it now with your programmable chip and I'm sure he'd tell you the same, probably more so on level 4.

BTW, my wife loves the '99 Burb. Just don't mess with her in traffic at altitude. I'm told she'll smoke you out at the next light. Just saying.:hihi::hihi::hihi::hihi::hihi::hihi:

 

[Slim Shady]

Smoke question

I have been talking (actually asking questions) with some people that do some professional (factory tuners) tunning for diesel trucks, They have a lot of experience with tunning for power and they tell me that just dumping fuel to a diesel doesn't constitute tunning, however they did say that unless you had some type of altitude compensation and fuel feed back system to let your PCM know that you are over fueling all diesels will smoke with the fuel turned up. Also told me that the smaller turbos tend to mask the smoke. I don't really know but seems that without some type of feedback from the intake and exhaust stream we are not much better off with a DS4 pump and probably a little better off with a manual pump.

If you mash the pedal on the gm obd 1 and obd 2 do you get fuel fuel the max the pump will put out the minute the APP sees full throttle.? Is there a way to tune the truck to not smoke? I suggest that the tuners can make any truck smoke and that just giving it more fuel does not make power, hence some tuners that don't know or never have run a set up can make the truck run poorly just by tunning it improperly, from not knowing or make the truck run poorly just because they may not recommend a set up. I know KOJO has obd 1 and obd 2 tunes that smoke less and have power because he has run and tested the truck and made adjustments to the tune while driving the truck for a particular set up. There are others that tune well also but some tuner's tunes seem to smoke more than others, is this a tuner issue?

Speaking with a tuner for GM regarding the 6.5 diesel he stated that data logging over many months and then running computer simulations with that data is how they get a good starting point for a tune. One that gives drive-ability and fuel economy with good emissions. I know for a fact the fuel delivery systems on these systems are not just a progressive linear fuel line, they have hills valleys and peaks that make the fuel curve. Any programmer thoughts on this?

Sorry Big T don't mean to derail your thread but if there was tunning that limited fuel to just enough to make power but not smoke wouldn't that be the way to tune? I guess the Dodge guys didn't get the note because I see them laying down big smoke a lot. Most of them don't find it offensive, at least I don't think so.

 

[buddy]

There is some altitude fuel derating, although GM didnt use it at all in L65 programs. The table is used in L56 programs. Was able to locate it from a disassembly of the code, since that PCM specialist helping me also doesnt like much smoke.

Smoke is typically based on the amount of pedal you give it. More pedal, more fuel, more smoke, so the user is in some control of it. The stock fuel curve for DS4 is heavily weighted to early in the fuel pedal, and it has a lot of fuel available early in the RPMs. I lower fueling at early pedal and also decrease the max available at early RPMs to try to prevent too much smoke from most common reasons. More advance at idle and low RPMs helps make power before boost is there, but at high elevation and with larger turbos could also spool the turbo slower.

 

[Slim Shady]

I know advance gives more power at lower rpm but is there a fine balance between to much advance and to little power. Example, generator set 6.2 diesel rpm regulated electronically to 1800 rpm no matter what the load is. Fuel is given to manual pump by electronic solenoid that cycles faster than the eye can see. So rpm is regulated by fuel only. now at 0 degrees TDC the engine had plenty of power and any load applied did not make much of a change in the rpm. same load same fuel setting advancing the timing to 2 degree BTDC gave better response and fuel economy. Same settings advance now at 4 degree and fuel economy went up slightly but any big load and the engine labored more and smoked. Advance to 6 degree and any big load made the motor slow and labor noticeably. So best setting for power and fuel ended up being three degree before TDC. The timing was measured with a MT 480 luminosity probe.

Also finding that what is called timing on the DS$ pump is not necessarily what is being seen correspondingly with a Luminosity probe.

 

[Big T]

There is some altitude fuel derating, although GM didnt use it at all in L65 programs. The table is used in L56 programs. Was able to locate it from a disassembly of the code, since that PCM specialist helping me also doesnt like much smoke.

Smoke is typically based on the amount of pedal you give it. More pedal, more fuel, more smoke, so the user is in some control of it. The stock fuel curve for DS4 is heavily weighted to early in the fuel pedal, and it has a lot of fuel available early in the RPMs. I lower fueling at early pedal and also decrease the max available at early RPMs to try to prevent too much smoke from most common reasons. More advance at idle and low RPMs helps make power before boost is there, but at high elevation and with larger turbos could also spool the turbo slower.

I'm with Buddy, as I can do a smokeless start at altitude.......if I wanted too.

 

[Slim Shady]

Looks like that beast can move though. And you know a woman with the power to make other motorist eat diesel smoke is a dangerous person.

 

[Big T]

Looks like that beast can move though. And you know a woman with the power to make other motorist eat diesel smoke is a dangerous person.

When she came home and told me that she smoked some MF who tried to take her from the right, I smiled big time. That's my girl.

 

[Slim Shady]

Yes you have to love that, More than one way to get even, I bet she laughs every time knowing she is going to choke someone out and stain the inside of their vehicle. I respect your wife already and don't even know her.