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To ATT or not part II Technical Discussion Only ?

New tune will help a lot with most everything. Can't comment on the EGT's though as I noted the same thing and haven't found a solution other than throttle control.
 
So I have timed the truck and it was right where it should be but no luck getting my EGT'S down yet. The turbo is making normal boost, 1.5-2 psi cruising on the highway and under throttle I've hit 10 psi only to be limited by EGT'S. I'll have some more info soon.
 
Paveltolz said:
New tune will help a lot with most everything. Can't comment on the EGT's though as I noted the same thing and haven't found a solution other than throttle control.
Click to expand...

My solution is to not watch the gauge! Just kidding, I dont have much of an EGT issue, but it could be because my gauge is wrong, or just not sensitive enough. I can get it up to like 1000F on a long steep hill WOT accelerating to over 100mph. The air around me is normally cool, 60s, 70s, and some fog (natural water mist). Although Ive run this setup through other states just fine too.

It might be from the timing curve. I can see a stock curve with increased fueling causing an issue and then increased fueling with too much advance causing an issue. Its always a battle determining the right amount of timing for a given load. I think about the scenarios you would be in to cause a certain fuel rate, to determine what kind of loading involved and modify the timing curve accordingly to try to keep combustion in the peak torque angles and burning clean. Thats not easy when working with different turbos. Fortunately, if you can get it to run good on a large turbo, it will still run good on the smaller turbo, but the fast spooling turbos can mask other issues you have and not quite right injection timing.

The ATT will probably spool a little better with less advance, but not the advance at idle, I mean the advance at the fuel rate you hit when putting your foot down. But then again, if you can live with a little more smoke a good amount of advance makes the normal engine feel more responsive. Its difficult to make the one tune thats great for all.
 
So let me tell you what my EGT'S are, while cruising on the highway at 70mph with the rpm's at about 2200_2300 I am running 800 degrees, if I go up a slight grade the temp rises to 900 or more depending on how big of a grade it is. If I try to go up any large grade the EGT'S are through the roof, I have to back off the throttle because they hit 1200 really quick.
 
Those are crazy temps, is the gauge accurate? I would try another or maybe an infrared temp gun.
 
Don't mean to denigrate a good turbo yet I'm seeing the similar temps only I'm at 4500'. If I'm rolling in OD around 65mph on a 4%+ grade of a mile or less, EGT's roll up to 900* easy and will continue to rise until I crest or downshift. Even at 65 to 70 mph on a 5-6% grade of two or more miles, 6500' or above, I have to downshift to keep it below 1100* and maintain speed. Otherwise I'm at 1200* in no time with no power and speed falling off. I would have thought it was the summer weather but it was fairly cool across the rocky mountains in Colorado and even over the passes in Nevada and my IATs weren't over 160. Seems one just has to keep the RPM's up without feeding it fuel.
I never saw 1200* before at lower altitudes though (3000' and below) even on the longer grades out of Yakima WA or Pendleton OR.
Acceleration with any type of authority and it shoots to 600-700 right off as well. Same behavior regardless of which tune or air cleaner set up I was running too.
How's the smoke and any issues with slow throttle / acceleration issues around 50-65?
I love the performance once boost comes up, but I'm not driving in what seems to be an optimal range as I'm always at or below 2lbs. Most times the boost gauge is pegged on the bottom.
My opinion, despite how it may sound above, is that the ATT is a Good turbo, just got to learn to adjust to the differences in behavior. I know I had to keep a sense of where the power started in relation to how much throttle I was giving it, find the power curve and ride it up rather than stomp and hope it would catch up to where ever I had placed the peddle. It was actually quicker and produced less smoke that way, which is an issue for me (yeah, I'm old, don't like diesel mosquito fumigators).

Most owners apparently aren't seeing these issues and your results may vary as these are just what I'm seeing with my truck, tires, lift, etc ... purely subjective to my circumstances.

After a year of tunes and turbo swaps, the ATT just doesn't seem to suit my driving style. I've got a new tune and have run 14 tanks across the US with the ATT so it is time to go back to the GM-5 to see how well they play together. Last time it didn't go so well mileage wise for the GM5. With the ATT I was starting to hit 19.5 on longer 70mph highway runs though and that was across OR, ID and UT. With the AC on across the mid-west in the heat wave I was seeing 16.8 to 17.5.
 
First thing I had my tuner do was drop the shift points to make the engine more rev happy. This made a difference. Specifically at a hill we have here that is 6-8% at 45 MPH the tune wanted to hold OD and smoke. Downshifting reduced the smoke. I am not worried about EGT's till 1250 and I have run 1400 for extended times on my 1993 pulling hills. Cooling system and timing determine if that EGT reading is a problem more than the EGT number alone.

The EGT rise you are seeing means the engine is being lugged and specifically lugged below the RPM the A-Team is useful at. I agree rev happy is a different driving style.

My 1995 with the factory tune peaks at 1100 EGT no matter what I do to it. I am in another thread working on the smoke issue I have.

Low boost while cruising is where having a bigger turbo is better for MPG - it isn't an exhaust restriction at the light throttle. The downside is you have to rev the engine to get boost. In contrast at 65 my GM 3 will produce 6 PSI of boost with no throttle. Sure the TM is a little tight, but, it needs to be to get 14 PSI of boost.
 
WW also got a pretty hot tune, although it shouldnt result in as much smoke as he has. That is being worked on too, a little less advance at loaded fuel rates should help spool it a little better.
 
I made a couple of videos the other day of how the truck runs on the highway. Here's one for now. [video=youtube;38QLoWeodlw]http://www.youtube.com/watch?v=38QLoWeodlw&feature=youtube_gdata_player[/video]
 
I've re-read the thread and didn't see that you've had the ECM re-tuned yet. Do that most skosh.
From the video's I see you held RPMs up there with gear selection and yes, those temps look too high for running down the highway and maintaining speed. I didn't see those temps with my ATT running the basic GLE, nor with the P series tuned for ATT or the economy tune I have now. Not even running up to 95mph on the flats, or ascending hills with the P tune. At least, not until I hammered it up to 95 holding high RPMs, High Load and boost up to 13lbs and then I would adjust to keep the temps below 1100. Only when I got to higher altitudes, low boost and RPM climbing in OD, as War Wagon stated would I see 1150, 1200+.
IMHO, you're being at or near sea level, depending on how Irene treats you this weekend, you shouldn't be getting those numbers. For me, running 70 mph in OD on the flats at 2200rpm I'd see 600-700 EGT and 1-3 lbs boost. Your boost looks right for that speed and RPM but the 800 EGT seems high.
Call and talk to Bill to get your tune updated.
 
The strange thing is that a N/A unit wouldnt likely run that high of EGTs, so you have to figure whats going on. Is the gauge wrong, or is the timing that far off optimal? Is there an air flow restriction? If its really that high, then you have unburnt fuel, so its injecting more than you need and may be working against you or wasting it. The only way the PCM can be causing it is timing, nothing else will come into play while cruising, and in that case likely needs to back off the advance. Too much advance and combustion before TDC works against your momentum and the combustion of other cylinders, and increases cylinder pressures. Maybe an animal crawled into the tail pipe.
 
Any smoke while doing this? I didn't see you romp it to wind things up and that would be interesting to see but unrelated to the question.
 
We have spoken on the phone but for the forum sake. What gear were you in with the NV4500? At the time , I can smoke mine and get those egts while lugging it in fifth gear or fourth gear at that rpm, what tire size? did you have the 255 85 tires? and gear set was 4.10 ?

Those egts are way more than I see with my truck Cruising or otherwise and I have pre cups modified (BIG TIME) (another thread) and a pretty (real nice) good fuel rate (ask Buddy). Now the boost also looks real low and not very responsive (never changes) for that rpm 2400 and speed or any other speed. Something isn;t making sense or isn't right.

Straight through exhaust ? and no leaks intake or exhaust, I know My boost gage is way more responsive than that. I can top my EGT's out at some pretty good numbers, but I can also get past 24 Lbs of boost and have got 26 an a few occasions. But I was also hitting some wicked egts at 3500 rpm with 26 psi boost (lost my cool with the speed as well)
 
So I put the GM5 back on and I see a definite decrease in EGT'S, I think they are still high for the GM5 but they are a lot better than with the ATT. I got a quick video of it this morning I will try to do better with it tomorrow. Sorry I haven't posted on this in a couple of days, I've been real busy working on the truck, I wanted to make sure everything was ok with it and whatnot.

http://youtu.be/BTmMrriSytc

http://youtu.be/FgaSlXGBMPA
 
is the max e tork program the hp or tow tune. I have the hp4 tune and an ATT and I don't see high egt's until I tow uphills. Empty I can boot on it and I run out of fuel before the egt's would be an issue.
 
Tazz....Just watched your first video. Havent read the entire thread but.... My 96' is the exact same configuration as yours. 5spd, turbomaster, 4inch exhaust, but i have the stock programing and stock gm5 turbo.

Couple things i noticed, coolant temp runs a bit higher than mine, but your EGTs are waaay higher. With my truck cruising on the highway or even around town, my max numbers are usually in the 500-800 range. Only time I ever see higher is when towing or pulling a really long hill at speed.

That being said your boost numbers are really low. Dont know if thats an att thing or what, but low boost (with the GMx) goes hand in hand with the high egts. But then again those numbers could be alot higher just with the tune alone. Im running at 11psi max and very happy with the resulting numbers.

Dont know if any of this helps but i thought id share as there arent too many 6.5 manual trans trucks to gather infomation from

-Nick
 
I didn't see a lot of difference, first video was about 5 mph faster. It would have to be on cruise in the exact same spot to make a good comparison as a slight change in APP pressure or speed can change the results.
 
Definately need to verify the pyrometer is accurate.

You should definately be able to get more than 7psi at WOT, although I would never WOT from a stand still with the ATT, maybe in 2nd gear. To only get 7psi, must have some issue, that the GM turbo will mask. The GM turbo can spool to 20 psi with a 3" exhaust with a catalytic converter and baffled muffler, with the same exhaust a large turbo would struggle to hit 5psi. So knowing for sure that the exhaust is clear helps. A large turbo will not run well with a Cat/soot trap, and need to make sure the exhaust crossover is not a stock type that may be collapsed inside.

2-3psi of boost while cruising is ideal, 6-8psi while cruising is a waste of energy and efficiency. This should not cause high EGTs, unless you are not getting good combustion. Poor fuel atomization from injectors, injectors not popping high enough, too advanced, ect....
 
Just want to give everyone an update and get you up to speed. I have since returned the ATT and have gotten a full refund from Walking J. After making sure that my truck was in proper running order I could not get the egt's to come down to a drivable level. I also had another member drive the truck with the ATT and with the GM-5 to get a second opinion and to make sure that I wasn't missing anything. I have made sure that my gauges were correct, there were no restrictions in my exhaust, my crossover was not leaking, my intake was sealed properly (had to do valve cover gaskets anyways), my pump was timed correctly and that there was no issues with fuel delivery. As a matter of fact the truck runs pretty darn good other than the GM-5 has worn seals and it is blowing some oil and the loose/worn waste gate shaft. The ATT may work well for others but it definitely would not work on mine. I have conferred with several different specialist on the 6.5 about this and they all came to the same conclusion that this turbo would not be a good match for my truck due to it being to big for what it is, to keep it simple. I will not name these people as they are not members here but they are reputable business owners that deal with these and many different types of diesels. As it sits right now I'll be putting on a stock GM-8. As I don't have the vacuum system on the truck anymore I'll have to fab up turbo master type controller for it.
 
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