oil temp with twins

duratothemax

duratothemax

<--- slippery roads
Aug 28, 2006
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coker6303 said:
I didn't realize that with the lml.

The lmm is a high flow low pressure pump while the older ones are lower flow but higher pressure right?
Click to expand...

the LML pump flows ~15-20% more.

You cant just make a pump "high flow low pressure" or "high pressure low flow". Thats not the way pumps work. Fluid pumps in general dont "produce" "pressure"...Pressure is just a matter of how much the flow is restricted.
 
coker6303

coker6303

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duratothemax said:
the LML pump flows ~15-20% more.

You cant just make a pump "high flow low pressure" or "high pressure low flow". Thats not the way pumps work. Fluid pumps in general dont "produce" "pressure"...Pressure is just a matter of how much the flow is restricted.
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I'm impressed! You are exactly right! Pumps create flow, pressure is simply the resistance to flow. The high pressure/low flow or vice versa would be based on the circuit. I should have re-worded my question before. I don't know much about the dmax itself but I do know hydraulics.

Does the LMM oil pump flow more/less than the LB7, LLY, LBZ? The reason I ask is the wierd way the pressure gauge shows the extremely low oil pressure at low RPM's but picks up quickly in mid-top rpms. I was told this is normal but unlike the other models. Maybe this was GM's way of slowing the oil down in the oil cooler to help with temps?? or am I wrong all together?
 
sweetdiesel

sweetdiesel

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coker6303 said:
if the second turbo is your added heat source causing the problem, then you would need the cooler as close to the return oil from that turbo as possible for max system temp drop. Like the reservoir where it drains.



if you put a cooler just before the turbo, it would cool the oil for about a foot before it is heated right back up by the second turbo and that hot oil will then pass through all of your engine bearings at the high temp. You gain nothing. It would be like putting an intercooler before the turbo.

imo the oil is going in x amount cooler its going to come out of the turbo x amount cooler.

also, if you mount the cooler in the engine bay then you have a small temp differential to allow the cooler to pull heat.

on a dd i would install it at the front of the truck.

what cooler and lube pump did you go with to circulate the oil in your pan on abby? The pan is going to be the best place to draw the oil to cool if that's where the second turbo drains and plus that's where the engine oil pump draws.

i use a 2gpm pump 1/2" in to the cooler and 1/4" line going out. This increases the pressure but slows down how fast it goes thru a small trans cooler with fan.
its mounted on the back of the truck. On a dd this would not be a big enough cooler but for race applications, i can sit in the pits with a bag of ice and a bottle of nos:thumb:


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jmho:)
 
duratothemax

duratothemax

<--- slippery roads
Aug 28, 2006
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Wyoming
coker6303 said:
Does the LMM oil pump flow more/less than the LB7, LLY, LBZ?
Click to expand...

same. the only difference between the 01-05 pumps and the 06-10 pumps is that the 06-10 pumps had a reverse-thread nut on the pump shaft to keep the nut from backing itself off.

coker6303 said:
The reason I ask is the wierd way the pressure gauge shows the extremely low oil pressure at low RPM's but picks up quickly in mid-top rpms. I was told this is normal but unlike the other models. Maybe this was GM's way of slowing the oil down in the oil cooler to help with temps?? or am I wrong all together?
Click to expand...

Normal. All duramax's do that. The oil pressure gauge is actually accurate. If you monitor pressure with a scan tool, you'll see that it shows pretty much what the gauge on the cluster shows.

Its not like the coolant temp gauge that is "buffered" and not really all that accurate. 20psi hot at idle is about the norm. 14psi hot at idle is the minimum allowable spec per GM. And 42psi minimum hot at 1800rpm.
 
coker6303

coker6303

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sweetdiesel said:
if the second turbo is your added heat source causing the problem, then you would need the cooler as close to the return oil from that turbo as possible for max system temp drop. Like the reservoir where it drains.



if you put a cooler just before the turbo, it would cool the oil for about a foot before it is heated right back up by the second turbo and that hot oil will then pass through all of your engine bearings at the high temp. You gain nothing. It would be like putting an intercooler before the turbo.

imo the oil is going in x amount cooler its going to come out of the turbo x amount cooler.

Theoretically yes, but realistically no. And you would still have 90% of the circuit at the higher temp so it would really only benefit the second turbo itself and nothing else.

also, if you mount the cooler in the engine bay then you have a small temp differential to allow the cooler to pull heat.

on a dd i would install it at the front of the truck.

I agree. That would be the best place for the cooler. Up there there would be no need for a 12v fan on a DD. Only thing is the added restriction/heat to the rest of the stuff already up there. why can't it be simple!!! lol

what cooler and lube pump did you go with to circulate the oil in your pan on abby? The pan is going to be the best place to draw the oil to cool if that's where the second turbo drains and plus that's where the engine oil pump draws.

i use a 2gpm pump 1/2" in to the cooler and 1/4" line going out. This increases the pressure but slows down how fast it goes thru a small trans cooler with fan.
its mounted on the back of the truck. On a dd this would not be a big enough cooler but for race applications, i can sit in the pits with a bag of ice and a bottle of nos
Click to expand...

nice!!! functionality is key!!

If the oil temp really is a big deal, i'm all for trying to figure out a cost effective way to drop temps efficiently. I'm going to try to put together a circuit in the next couple of weeks and try it out. Its just not no the priority list right now!
 
coker6303

coker6303

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Aug 6, 2009
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duratothemax said:
same. the only difference between the 01-05 pumps and the 06-10 pumps is that the 06-10 pumps had a reverse-thread nut on the pump shaft to keep the nut from backing itself off.



Normal. All duramax's do that. The oil pressure gauge is actually accurate. If you monitor pressure with a scan tool, you'll see that it shows pretty much what the gauge on the cluster shows.

Its not like the coolant temp gauge that is "buffered" and not really all that accurate. 20psi hot at idle is about the norm. 14psi hot at idle is the minimum allowable spec per GM. And 42psi minimum hot at 1800rpm.
Click to expand...

Thanks for the clarification. I'll hook the scan tool up in a second when I leave out so I can see what is going on.

Also, you can change at what pressure the "low oil pressure" warning comes on in table B1402. Has anyone increased this up closer to operating pressure to decrease the buffer It is set at 6psi stock
 
duratothemax

duratothemax

<--- slippery roads
Aug 28, 2006
7,139
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Wyoming
coker6303 said:
Also, you can change at what pressure the "low oil pressure" warning comes on in table B1402. Has anyone increased this up closer to operating pressure to decrease the buffer It is set at 6psi stock
Click to expand...

yes. I set mine at 14psi. Because thats what GM says is minimum allowable spec at idle.
 
hondarider552

hondarider552

Getting faster
May 28, 2008
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Highest oil temp pre cooler I have seen is 252*, oil pressure fluctuates from 36-55psi at 2100rpm. Investing in a engine oil cooler. :thumb:
 
J

joshde67

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Hey guys. im looking for a green boost pressure guage and a green exhaust temp guage. can you guys help me? I really appreciate it. Thanks.
 
hondarider552

hondarider552

Getting faster
May 28, 2008
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After a few weeks of testing, here are my results..

I bought a "new used" Killerbee cooler from a member local in AZ. Before I had the cooler, on the hills my oil pressure would flucuate between 35 and 65psi. I knew it was because of the oil heat from the twins. I didnt put a oil temp gauge in till it cooled down some ( was 115* outside air temp). My gooseneck is 4500 lbs or so, not a heavy load, but puts some weight behind the truck for a good test. Anyone who lives in AZ knows the hills between PHX and Flagstaff, the highest oil temp I saw going 60-65mph mph up the grades pre OEM oil cooler was 274*, at this time the oil pressure gauge was doing the :dancenana:

Around town was a different story; coolant temps follow the oil temps, untill I get on the freeway, then the oil temps start to climb; unloaded. Normal oil temps at cruise @ 65 were about 195-215. Coolant would remain at 187-190.

I decided it was time to invest in a cooler. If my oil temps are out of control towing a unloaded trailer what happens if I load 12k behind it...:confused:


Cooler installtion was cake, mount the huge cooler, and plumb the cooler lines form the oil filter assembly. New cooler took a little over 3.5 qts, so I throw in 14qts on a oil change and call it good. Took me 2 hours. Cooler measurements are 28" long, 7" tall and just over 4" thick, it's a huge cooler...

Retested the route I took a month earlier, outside temps did drop about 15* or so, but the same hills at the same speed, here is the oil temp crusing up the hill at 60mph, pulling the same trailer.. Sorry camera is a bit out of focus.

I have regained control of my oil temps and oil pressures. Ive gained back a few PSI at hot idle, and I would say 5-8psi at 2000rpm cruise. This lower oil temp allowed my to run a max gauge of 250* instead of 300*

Coolant temp is more stable, since the OEM oil cooler isnt working so hard offloading the oil heat into the coolant. Oil temp comes up slower, as well as the coolant. I do not have any mor eoil pressure and flucuation issues, which was my main concern. I think any sort of engine oil cooler should be on every twin'd duramax, simply because of this issue. We only have 10 qts of oil to cool a lot of the engine, and a undersized cooler to deal with it. If you dont have a oil temp gauge with twins, I would higly suggest putting one in. Takes 20 mins to install one using the hex plugs in the oil filter assembly.
 
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