2023 GM Duramax Diesel 3.0L I6 - Test Drive Impression

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HEMIMANN

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I'd guess the diesel option won't be the high percentage engine choice by customers. At least those that don't know that GM's gassers are oil-pumpers (after 40-70k miles).
 

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Just want to add that, other than being made by Bosch, the CP4 is not any version or adaptation of a CP3. They are totally different architcture and construction. Not even close.
And to add to this, CP4.1 and CP4.2 are 2 different pump displacements. A CP4.1 is a single (1) bore & piston used on smaller engines like BMW diesels. The CP4.2 is the pump Ford continues to use and Cummins "tried out" for '19 & '20 on the 6.7 before going back to a CP3 design.
 

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So, what HPFP is used on the GM 3.0?

I believe it uses a Denso pump similar to the HP3. It is a v-twin bore like the Bosch unit 4.2.
It is a chain drive unit on the back of the engine, driver side. The chain requires to be changed around 100k which requires pulling the transmission and rear cover.
 

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I believe it uses a Denso pump similar to the HP3. It is a v-twin bore like the Bosch unit 4.2.
It is a chain drive unit on the back of the engine, driver side. The chain requires to be changed around 100k which requires pulling the transmission and rear cover.

Just a minor nit pick, it's belt drive not chain. The belt is bathed constantly in oil and is designed to "get wet", and its a 200k mile change not a 100k mile. Which means you probably only have to change it once in the lifetime of the truck. People freak out about this fact but its a minor inconvenience as far as I'm concerned. It's easy to plan and budget for, just the cost of doing business. If the rest of the truck/engine holds up its well worth the change at 180k (just to be safe).
 

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Just a minor nit pick, it's belt drive not chain. The belt is bathed constantly in oil and is designed to "get wet", and its a 200k mile change not a 100k mile. Which means you probably only have to change it once in the lifetime of the truck. People freak out about this fact but its a minor inconvenience as far as I'm concerned. It's easy to plan and budget for, just the cost of doing business. If the rest of the truck/engine holds up its well worth the change at 180k (just to be safe).
The lube oil pump is belt driven but the fuel pump is chain driven, from what I have read.
 

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Just a minor nit pick, it's belt drive not chain. The belt is bathed constantly in oil and is designed to "get wet", and its a 200k mile change not a 100k mile. Which means you probably only have to change it once in the lifetime of the truck. People freak out about this fact but its a minor inconvenience as far as I'm concerned. It's easy to plan and budget for, just the cost of doing business. If the rest of the truck/engine holds up its well worth the change at 180k (just to be safe).

You're referring to the variable OIL pump which is belt drive and has a service life of 150k miles.
The high pressure fuel pump I pictured above is CHAIN driven. The same chain that drives the camshaft through plastic guides and held tight by a tensioner. There's been failures around 120k and less. Typical fashion, just outside warranty.
It starts with a cam/crank sync code.
P0016 -- camshaft / crankshaft position correlation
I'll attach a picture so you can better understand. The belt is the lower one for the oil pump. The chain like I said drives the rest.

Screenshot_20230830_100045_Chrome.jpg
 

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Yep - I read about the history and fixes on new LZO variant. Sounds good to me, except that dumb belt driven oil pump in the rear. Whatever.

I'm more interested in the reliability and durability of the exhaust science fair system. Specifically if they've improved this system so it's not exclusively high load high mile application exclusively. I read GM put a lot of work into this for this smaller diesel, knowing the half tons don't get used hard very much (unlike the heavy duty trucks). I'd be willing to test that. These systems have been around for a decade and a half, plenty of time to get bugs fixed.

I looked under the truck, the packaging is very well done, now. No more kluging stuff together, very integrated. I haven't head too many issues with Fiat's EcoDiesel exhaust system, just the engine blowing up. ha ha (yes I know that was 1st generation, but to get fundamental crank bearing loading wrong is just incompetence).
 

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Yep - I read about the history and fixes on new LZO variant. Sounds good to me, except that dumb belt driven oil pump in the rear. Whatever.

I'm more interested in the reliability and durability of the exhaust science fair system. Specifically if they've improved this system so it's not exclusively high load high mile application exclusively. I read GM put a lot of work into this for this smaller diesel, knowing the half tons don't get used hard very much (unlike the heavy duty trucks). I'd be willing to test that. These systems have been around for a decade and a half, plenty of time to get bugs fixed.

I looked under the truck, the packaging is very well done, now. No more kluging stuff together, very integrated. I haven't head too many issues with Fiat's EcoDiesel exhaust system, just the engine blowing up. ha ha (yes I know that was 1st generation, but to get fundamental crank bearing loading wrong is just incompetence).
Remember, the Ecodiesel started life as a stillborn GM design...
 
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You're referring to the variable OIL pump which is belt drive and has a service life of 150k miles.
The high pressure fuel pump I pictured above is CHAIN driven. The same chain that drives the camshaft through plastic guides and held tight by a tensioner. There's been failures around 120k and less. Typical fashion, just outside warranty.
It starts with a cam/crank sync code.
P0016 -- camshaft / crankshaft position correlation
I'll attach a picture so you can better understand. The belt is the lower one for the oil pump. The chain like I said drives the rest.

View attachment 527477

Ok - that I did not know about....common chain to cams and high pressure fuel pump. Has anyone hear of an overhead cam diesel before?
 
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Here's pics of the RAM 1500 compared to the GM 1500 HPFP.
GM 3.0
View attachment 527454
View attachment 527451

RAM 3.0
View attachment 527452

"The 3.0L Duramax features a high pressure common rail injection system capable of fuel pressures in excess of 36,000 psi (36,260 psi, 2,500 bar). A Denso HP5 injection pump is utilized in conjunction with Denso solenoid actuated fuel injectors. This combination allows for up to 10 injection events per combustion cycle under compatible operating conditions. Like other Duramax engines, the fuel injection pump is chain driven. The HP5 injection pump is a twin cylinder, vee configuration similar to that of the Bosch CP4. An in-tank electric fuel lift pump supplies fuel to the injection pump."
 
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Remember, the Ecodiesel started life as a stillborn GM design...

Yes - both Duramax's were joint ventures until GM bought out Isuzu. Notably, the little engine uses Japanese fuel system - not Bosch.
 
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Uh-oh........did not know GM made a science fair out of the cooling system. This is what wasn't hooked up right on my test drive truck from the factory, causing it to overheat. Dealer fixed it later. Anything this convoluted is bound to fail sooner rather than later -

Cooling System​

3.0L Duramax engines utilize a unique, highly complex active thermal management system. The engine coolant control valve, an assembly of 3 independently operated electrically actuated valves, manages engine coolant distribution through the engine block, cylinder head, heater core, transmission cooler, and engine oil cooler. The primary goal of the system is to distribute engine coolant where and when it is needed in order to provide rapid engine warm-up and maintain combustion chamber temperatures (note that combustion efficiency is closely related to operating temperature). To protect the cooling system from overheating, coolant flow through the EGR cooler is continuous.

To facilitate the operation of this system, 7 engine coolant temperature sensors are strategically mounted throughout the system. While a standard engine driven water pump is employed for primary engine cooling needs, a variable speed electric water pump supplies coolant through the charge-air-cooler circuit. Additionally, a second electric water pump is used in low ambient temperatures (< 59° F) to keep hot engine coolant circulating through the heater core during start-stop operation. The sole purpose of this device is to maintain cabin heater functions during cold weather operation when the engine is stopped; function of this electric water pump is disabled while the engine is running.
 
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