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Gm's new 6.6l gas engine

I don't know much about this, but have a few random thoughts to add:
  • Direct injection can add low-end torque because it lets you add compression. Other than forced induction and displacement, that's all you can do for low-end torque (the "P" below).
Torque = nPV/4Pi
n = efficiency
P = Brake mean effective pressure
V = Swept volume = Piston area A x Stroke L
Click to expand...
  • Efficiency is really easy at 2000RPM. Those factory intakes, exhausts and cams that limit power at 6000RPM work fine down low. It would be interesting to see if the 6.6 ends up undersquare, i.e. a stroker, to help low end torque. In the formula it makes no difference how you "spend" your displacement, but the power band can be lowered and that's where it becomes a more valid truck engine.
  • Granted, all of the technology upgrades could happen at 5.3, 6.0 and 6.2L displacements, but carmakers have been creating new displacements to distinguish different engines for several decades. If it ended up at 6 liters buyers might think it's a marginal change to the LQ4.
  • Towing isn't just about weight, but also wind drag. A 6000lb camper is much harder to tow than a 6000lb truck due to the terrible aerodynamics. When the trailer is sucking 100hp all day at 70MPH, that's 100 less HP you have to pull the grades. No matter how many gears are in the transmission, if it takes 300HP to pull the grade, the engine will run in a gear that allows at least 300HP. Only a lower power band lets you pull it in higher gears.
  • I feel diesel longevity is a myth in modern light-duty trucks. Sure, HD diesels can be fully rebuilt multiple times to hit 1,000,000 miles, but LD diesels can't. The body, chassis and transmission are setting the lifetime of the vehicle for gas and diesel now. Vortecs get 300,000 miles all the time and the trucks are usually pretty worn out by then. With 100,000 mile injector failures the diesels are costing more to keep on the road.
 
Blue85 said:
  • Vortecs get 300,000 miles all the time and the trucks are usually pretty worn out by then. With 100,000 mile injector failures the diesels are costing more to keep on the road.
Click to expand...

I cant agree with this more. And add in modern emissions and I'm not too sad I went with an L96 powered truck instead of a diesel this go round. Sure some farm loads are gonna make it struggle but that's ok, GM built it to handle the abuse.

I like my company truck with a 6.7 Cummins but after its couple recent emissions issues I'm really wishing I could delete. calling a customer saying I can't make it due to emissions issues on a fairly new truck sucks
 
The thing you guys are missing comparing this new 6.6 gen 5 to the l86 6.2 is this engine is designed for a 100 percent duty cycle on REGULAR unleaded. It makes less horsepower than the 6.2 but the 6.2 requires premium with it's 11.5 cr.
Long stoke,iron block,DI and no AFM all add up to a engine that should be as hell and back reliable as the old l96 and absolutely stomp it in every performance metric.
That's not even taking into account the 10 speed. It's a game changer all by itself.
 
From where I am sitting I have towed 10k with my 5.3 and the gappy nv4500 and because in CA I am limited to 55 which I adhere to like religion btw.. makes the gear splits kind of you either slow down or your revving it.. I personally have zero issues with spinning this thing at 4K if I have to all day long.. it’ll prob do that longer than if you lugged it everywhere.. and it doesn’t take but maybe 40% throttle to maintain no less than 45mph... never once have I created a hill slower regardless of what I was towing with the LS and the funny thing is the big block in my wifes burb seems to do pretty much the same thing with less rpm. They pretty much tow the same power wise.. the ls just doesn’t care.. we can argue about power curves all day long but the reality is that does not really take into account all of the factors.. turbo tho that’s where the low end torque is made... if I am wrong then why does every diesel run one??
 
Blue85 said:
I don't know much about this, but have a few random thoughts to add:
  • Direct injection can add low-end torque because it lets you add compression. Other than forced induction and displacement, that's all you can do for low-end torque (the "P" below).

  • Efficiency is really easy at 2000RPM. Those factory intakes, exhausts and cams that limit power at 6000RPM work fine down low. It would be interesting to see if the 6.6 ends up undersquare, i.e. a stroker, to help low end torque. In the formula it makes no difference how you "spend" your displacement, but the power band can be lowered and that's where it becomes a more valid truck engine.
  • Granted, all of the technology upgrades could happen at 5.3, 6.0 and 6.2L displacements, but carmakers have been creating new displacements to distinguish different engines for several decades. If it ended up at 6 liters buyers might think it's a marginal change to the LQ4.
  • Towing isn't just about weight, but also wind drag. A 6000lb camper is much harder to tow than a 6000lb truck due to the terrible aerodynamics. When the trailer is sucking 100hp all day at 70MPH, that's 100 less HP you have to pull the grades. No matter how many gears are in the transmission, if it takes 300HP to pull the grade, the engine will run in a gear that allows at least 300HP. Only a lower power band lets you pull it in higher gears.
  • I feel diesel longevity is a myth in modern light-duty trucks. Sure, HD diesels can be fully rebuilt multiple times to hit 1,000,000 miles, but LD diesels can't. The body, chassis and transmission are setting the lifetime of the vehicle for gas and diesel now. Vortecs get 300,000 miles all the time and the trucks are usually pretty worn out by then. With 100,000 mile injector failures the diesels are costing more to keep on the road.
Click to expand...
In regards to injection failures,

Our Schaeffer rep claims that higher and higher system pressures cause carbon build up inside the injection system itself.

We have always had our own tank on site for our fleet of semi trucks and have always used Schaeffer fuel treatment religiously. We have never had a single injection system issue.

This is our 16th year and we started with 1 truck. We are now at 14.

With higher injection system pressures and lubricating properties removed from diesel fuel, there must be additives to make fuel systems live.


In regards to the new 6.6. I want one in a crate for my next project.
 
A brand new gas DI system will likely be less reliable than an existing diesel DI system.
 
sreidmx said:
. turbo tho that’s where the low end torque is made... if I am wrong then why does every diesel run one??
Click to expand...

Roots style blowers make torque down low. But Rob HP numbers in doing so. Turbos make HP and some torque but only after they spool up, usually past 2-2.5k rpm.

Diesels have turbos because they naturally make good low torque but lack in higher rpm hp.
Like the old turboless 7.3idi and the 6.2 diesels in our squares. Good low torque but no hp.
 
shady said:
Roots style blowers make torque down low. But Rob HP numbers in doing so. Turbos make HP and some torque but only after they spool up, usually past 2-2.5k rpm.

Diesels have turbos because they naturally make good low torque but lack in higher rpm hp.
Like the old turboless 7.3idi and the 6.2 diesels in our squares. Good low torque but no hp.
Click to expand...
You beat me to it
 
shady said:
Roots style blowers make torque down low. But Rob HP numbers in doing so. Turbos make HP and some torque but only after they spool up, usually past 2-2.5k rpm.

Diesels have turbos because they naturally make good low torque but lack in higher rpm hp.
Like the old turboless 7.3idi and the 6.2 diesels in our squares. Good low torque but no hp.
Click to expand...
You make many assumptions here, turbos can be sized to spool at any rpm.. hell most of the 2.0t engines out right now are peaking torque around 1800... and have a flat curve and of course fall off..

This is all just a product of the VE of the engine, putting a turbo on like the aftermarket suggest would net you the typical laggy response but the oem typically undersizes the buffer making the low end torque curve much more pronounced, also when you change the load this spools the turbo even faster so the boost threshold is even lower. Me thinks you haven’t spent a ton of time in a gas turbo vehicle??? Surprisingly the VGT stuff hasn’t made it into the turbo gas stuff yet.. that changes quite a bit as well.. the roots stuff is undeniable but so inefficient you can’t consider it as a daily in the real world..
just my opinion.. take it with a grain of salt..
 
Never ridden in a turbo gasser of any kind ever lol. Just going by the hrs of research I've done on line. But that research is pretty much geared towards the aftermarket yes. so there probably is a bias in there.

All I search is how to make low end torque. That's the info that comes up :dunno:
 
Blue85 said:
A brand new gas DI system will likely be less reliable than an existing diesel DI system.
Click to expand...
Gas DI has been around in the GM world since '09. It is well proven and reliable technology at this point.
In my experience much more reliable than the Bosch cp4 used on the 6.7 powerstroke and lml dmax.
 
jake 03 said:
Gas DI has been around in the GM world since '09. It is well proven and reliable technology at this point.
In my experience much more reliable than the Bosch cp4 used on the 6.7 powerstroke and lml dmax.
Click to expand...
I have not had problems with the direct injection on the wife's '11 Acadia in 125K. When compared to the '95 S10 Blazer back in the day, way better for the same age and miles.
 
shady said:
Never ridden in a turbo gasser of any kind ever lol. Just going by the hrs of research I've done on line. But that research is pretty much geared towards the aftermarket yes. so there probably is a bias in there.

All I search is how to make low end torque. That's the info that comes up :dunno:
Click to expand...
There is a huge difference and I am glad you admit that. And I’ve only been in a few boosted v8s but never have I been like it needs more torque down low.. anyway I’m gonna be turbo charging Ethel because I want more low end.. we’ll see if my ideas are BS! Hope not!
 
sreidmx said:
There is a huge difference and I am glad you admit that. And I’ve only been in a few boosted v8s but never have I been like it needs more torque down low.. anyway I’m gonna be turbo charging Ethel because I want more low end.. we’ll see if my ideas are BS! Hope not!
Click to expand...
I have seen some good turbo setup for a v8 using a small 4 banger turbo to spool up just above idle but as you stated above it falls flat once it reaches the top of the Watergate pressure
 
imiceman44 said:
I have seen some good turbo setup for a v8 using a small 4 banger turbo to spool up just above idle but as you stated above it falls flat once it reaches the top of the Watergate pressure
Click to expand...
So we actually tested a single he351cw on a 6.0ls and it managed 400hp and 500lbft to the tire but the back pressure had to be killer.. it died about 3800rpm.

That’s way small for a 6.0 but might be perfect for the 4.8?? Something to try for sure..
 
sreidmx said:
So we actually tested a single he351cw on a 6.0ls and it managed 400hp and 500lbft to the tire but the back pressure had to be killer.. it died about 3800rpm.

That’s way small for a 6.0 but might be perfect for the 4.8?? Something to try for sure..
Click to expand...


It’s not to small for the 6.0 you just need two of them :)
 
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