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A military rebuilt 6.5

n8in8or said:
Oh and yes, I did notice a discrepancy between the dash gauge and the ECMs ECT reading. As much as 15*F sometimes. I'm not sure which is more important though to be honest.....since I'm assuming the temp in the crossover is the ECM temp and the temp in the cylinder head is the gauge temp. Is that right?
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I get a swing of 20+ degs f (194 deg f) in ECT at speed 70 mph it quickly drops down to 174 at slow speed and idle. I run one 180 deg f and one 195 deg f stats.
 
n8in8or said:
Oh and yes, I did notice a discrepancy between the dash gauge and the ECMs ECT reading. As much as 15*F sometimes. I'm not sure which is more important though to be honest.....
Click to expand...

Am sensing that the ECM's sending unit is higher on the importance list as I am noticing that cooler ECT temperatures effect the sound signature of the motor. At 55 - 60 mph with outside air up to the mid 80's F, the ECT's will drop to the mid 160's and I can hear the motor make more of a diesel clatter until ECT rises back to 170F.
 
Oh yeah good point. So absolutely the ECM coolant reading would determine how it's going to run. I was just thinking about monitoring one instead of the other all the time. What if the coolant temp in the crossover is 195, but the gauge is reading 210 because that's what it's reading in the cylinder head? Then it seems that would be something important to keep track of if towing heavy up a hill. I'm not sure if that would actually happen, just an example. It's interesting all the info we can gather on these if we really try. Hmmm...
 
JayTheCPA said:
Am sensing that the ECM's sending unit is higher on the importance list as I am noticing that cooler ECT temperatures effect the sound signature of the motor. At 55 - 60 mph with outside air up to the mid 80's F, the ECT's will drop to the mid 160's and I can hear the motor make more of a diesel clatter until ECT rises back to 170F.
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And using more fuel when it drops below 170 deg f.
 
JayTheCPA said:
Same here.



Suspect that it is also leading to wet stacking, but will need better experts to chime-in as to whether this is possible / likely to occur.
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I did note when I converted to EVANS too much bypass led to a too cool running diesel under 170 deg f at lower speeds only got warm at constant 45 mph.

I guess FERM can chime in on this wet stacking resulting from too cool thermal issues, my next step is dual 195 stats or maybe one 195 & one 205 stat to keep the heat up @ lower rpms. I'm not convinced running the 6.5 hotter is a bad thing providing it is in good shape and enhanced or newer design. "What the layout of your cooling system do you have the bypass restricted, med truck fan clutch, stat temp, etc or?"

I see you have a timing gear drive and that has a 2 dge advance built into it so recommended TDCO is less than w/o that drive this maybe relevant.
 
Jay, I did some digging into wet stacking on other than genset diesels and find excessive idling, no load will cool cylinder temps to point of not burning all the fuel even though the ECT maybe normal with EGT is under 400 deg f. this about average so I suspect running a little warmer on ECT on an otherwise good running 6.5 maybe the fix........and 2 stroke in the diesel will help lube the cylinder walls and rings to reduce or maybe prevent wet stacking damage.
 
I was on the highway for maybe 3 miles last night, so not really long enough to come to a firm conclusion, but both my dash gauge and OBDII scanner were staying rock-steady at 190 degrees. That was at 75mph and it was only about 65 degrees ambient.
 
n8in8or said:
I was on the highway for maybe 3 miles last night, so not really long enough to come to a firm conclusion, but both my dash gauge and OBDII scanner were staying rock-steady at 190 degrees. That was at 75mph and it was only about 65 degrees ambient.
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Sounds good.

I forgot to mention my logging was at 95 deg f ambient.
 
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n8in8or said:
I was on the highway for maybe 3 miles last night, so not really long enough to come to a firm conclusion, but both my dash gauge and OBDII scanner were staying rock-steady at 190 degrees. That was at 75mph and it was only about 65 degrees ambient.
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Glad to see the temps are consistent. Even though the run was short, that was enough for any divergence to occur. This was with the bypass restricted, correct?


FellowTraveler said:
"What the layout of your cooling system do you have the bypass restricted, med truck fan clutch, stat temp, etc or?"

I see you have a timing gear drive and that has a 2 dge advance built into it so recommended TDCO is less than w/o that drive this maybe relevant.
Click to expand...

Cooling system is re-used radiator (mechanic felt it was still good-to-go), new spin-on pump, dual 195F t-stats, and DMax fan. Do not know whether I have a restricted bypass and will find that out soon.

For the timing, IIRC the timing gear was part of the discussion when I got the current tune.
 
JayTheCPA said:
Glad to see the temps are consistent. Even though the run was short, that was enough for any divergence to occur. This was with the bypass restricted, correct?




Cooling system is re-used radiator (mechanic felt it was still good-to-go), new spin-on pump, dual 195F t-stats, and DMax fan. Do not know whether I have a restricted bypass and will find that out soon.

For the timing, IIRC the timing gear was part of the discussion when I got the current tune.
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I made my own restricter by drilling out a pipe plug, threading the inside of the bypass fitting and then threading the plug into it. I don't have the Dmax fan but I do have the heavy duty spin-on fan clutch. image.jpgimage.jpg
 
JayTheCPA said:
Glad to see the temps are consistent. Even though the run was short, that was enough for any divergence to occur. This was with the bypass restricted, correct?




Cooling system is re-used radiator (mechanic felt it was still good-to-go), new spin-on pump, dual 195F t-stats, and DMax fan. Do not know whether I have a restricted bypass and will find that out soon.

For the timing, IIRC the timing gear was part of the discussion when I got the current tune.
Click to expand...
What I found w/EVANS is that the stock cooling system for 1999 GMT400 6.5td will keep the coolant too cool and below 170 deg f. most of the time the fix is a restrictor in the coolant bypass that's what worked for me.
 
JayTheCPA said:
Am sensing that the ECM's sending unit is higher on the importance list as I am noticing that cooler ECT temperatures effect the sound signature of the motor. At 55 - 60 mph with outside air up to the mid 80's F, the ECT's will drop to the mid 160's and I can hear the motor make more of a diesel clatter until ECT rises back to 170F.
Click to expand...
You ever fix this low temp @ speed issue, or?
 
Not yet. Am digging into it now.

Plan is to check for whether the bypass has a restriction in it and for grins replace the AC Delco thermostats with Mr Gaskets'.
 
FellowTraveler said:
Any update on that great build, or?
Click to expand...
I just swapped the transmission mount for an Energy Suspension unit. It's smoother inside the truck at most RPMs, but harsher at others. I'm growing more and more convinced that I don't like this camshaft, but I'll keep it for a while. Since I had to have the camshaft from the Optimizer ground, and apparently the camshaft is different from either 2000 or 2002 and up I need to find another stock camshaft before I can swap it out. It will stay in at least for this year though. I may even throw it on the dyno first so I can compare it with a stock camshaft.

My next thing to do is datalog to figure out why I have less power at full throttle than I do at 3/4 throttle. Other projects have been keeping me busy, but I hope to be doing that very soon. Oh and the rebuild and installation of a 14 bolt SF rear end is happening soon too.
 
The bump stick provider should be able to tell you what rpm range the grind is for.

Your loss of power up top is because you have run out of fuel as the VE climbs with boost beyond available fuel data log will evidence this, then there is the IAT to consider if it is too high, a mechanical DB2 bull moose pump can supply the needed fuel. At pressure ratio of 2.0 you are looking @ 14/15 lbs boost on gauge however it's 29.4+- lbs boost actual w/HX40w you are stuffing almost 40+- lbs of air into that diesel @ 2.0 pressure ratio then consider 40lbs of air supply's enough air to feed a 400 hp engine "so you need more fuel."

As dyno's go they can't tell you as much as they could when calibrated for automatic slippage across the rpm range then there is the issue with most dyno rollers there is not enough air flow across cooling stack to give accurate reads after the first run another words the blower needed to provide such airflow would be able to simulate airflow across stack at upper double digit and lower triple digit speeds............ I did a post on this awhile back but can't remember where that old timers has a grip on me right now..........
 
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