Jump to content

GM has to make another Big Block

yukon25008.1

Recommended Posts

ChevyTech77 Senior Enthusiast

ChevyTech77

Posted
Posted

any engine with a bore of over 4.00" is hard to control HC and detonation in.

 

The 6.0L/6L90 puts more power to the ground than the 8.1L/Allison did

 

 

 

I assume you have facts to back both of these claims up, right, because both are loaded

with B.S. if you ask me. The second quote, for sure and I've never, ever, seen the first one ever proved.

C/K Man Enthusiast

C/K Man

Posted
Posted

any engine with a bore of over 4.00" is hard to control HC and detonation in.

 

The 6.0L/6L90 puts more power to the ground than the 8.1L/Allison did

 

 

 

I assume you have facts to back both of these claims up, right, because both are loaded

with B.S. if you ask me. The second quote, for sure and I've never, ever, seen the first one ever proved.

 

 

The problem with engines that have a bore over 4" is the surface area of the combustion chamber. Fuel will condense on all surfaces in a combustion chamber and will not burn, contributing to HC emissions. In addition, the slot that is formed between the top compression ring and the top of the piston is another area that HC tends to hide in, and of course the greater the bore, the more volume there is in that slot. Manufacturers have limited this area by locating the top ring as far up on the piston as they can, but it is still a significant source of HC emissions. The best way around the problem is going to a more under-square engine design, less bore but more stroke gets you the same displacement but minimizes combustion chamber surface area and upper ring slot.

 

The effects of cylinder bore on detonation are not as great as compression ratio, but the greater the bore the more likely an engine is to detonate. Flame front travel is a big factor, and it can be partially overcome with multiple spark plugs (Ford 6.2L, Dodge Hemi). It gets into the law of diminishing returns, increase the bore for more power, but you reach a point where you have to limit compression ratio and ignition timing to control detonation (you see why 8.1L's only make 330 h.p.?). Sure the BBC is great on 100+ octane or CNG/LNG!

 

Sorry, I can't find the dyno chart I had that compared an 8.1L/Allison to a VVT 6.0L/6L90. The 6.0L beat the 8.1L at nearly every speed. Yes, it's a bit of an apples-to-oranges deal. The VVT helps the 6.0L a lot, and the Allison gear and converter ratios are not optimal for a gas engine (the 6L90 has near perfect ratios for a gas engine, keeps it right in the middle of the power band). The information came from a GM Powertrain engineer.

C/K Man Enthusiast

C/K Man

Posted
Posted

And after all that I forgot to mention what a disaster iron cylinder heads are! Anyway, the 8.1L was a good engine, but you have to keep in mind it is an update on '60's technology, and it has some limitations. I used to really like ther old GMC V-6's, and they were outdated in the early '70's. They, like the BBC's, would get the job done. But, not very efficient.

ChevyTech77 Senior Enthusiast

ChevyTech77

Posted
Posted

any engine with a bore of over 4.00" is hard to control HC and detonation in.

 

The 6.0L/6L90 puts more power to the ground than the 8.1L/Allison did

 

 

 

I assume you have facts to back both of these claims up, right, because both are loaded

with B.S. if you ask me. The second quote, for sure and I've never, ever, seen the first one ever proved.

 

 

The problem with engines that have a bore over 4" is the surface area of the combustion chamber. Fuel will condense on all surfaces in a combustion chamber and will not burn, contributing to HC emissions. In addition, the slot that is formed between the top compression ring and the top of the piston is another area that HC tends to hide in, and of course the greater the bore, the more volume there is in that slot. Manufacturers have limited this area by locating the top ring as far up on the piston as they can, but it is still a significant source of HC emissions. The best way around the problem is going to a more under-square engine design, less bore but more stroke gets you the same displacement but minimizes combustion chamber surface area and upper ring slot.

 

The effects of cylinder bore on detonation are not as great as compression ratio, but the greater the bore the more likely an engine is to detonate. Flame front travel is a big factor, and it can be partially overcome with multiple spark plugs (Ford 6.2L, Dodge Hemi). It gets into the law of diminishing returns, increase the bore for more power, but you reach a point where you have to limit compression ratio and ignition timing to control detonation (you see why 8.1L's only make 330 h.p.?). Sure the BBC is great on 100+ octane or CNG/LNG!

 

Sorry, I can't find the dyno chart I had that compared an 8.1L/Allison to a VVT 6.0L/6L90. The 6.0L beat the 8.1L at nearly every speed. Yes, it's a bit of an apples-to-oranges deal. The VVT helps the 6.0L a lot, and the Allison gear and converter ratios are not optimal for a gas engine (the 6L90 has near perfect ratios for a gas engine, keeps it right in the middle of the power band). The information came from a GM Powertrain engineer.

 

 

I know the theory but again, I've seen side by side HC testing done between over square and square engines and they are no where near far enough apart to cause serious issues. They can be cleaned up with other methods and used quite nicely.

 

I can get as much GM Powertrain information as you'd like but on the street, loaded especially, there isn't a 6.0 VVT/6L90 TOUCHING an 8.1 with an Ally, period. That 8.1/Ally combo will pull circles around the 6.0 VVT/6L90 combo all day long and twice on Sunday.

C/K Man Enthusiast

C/K Man

Posted
Posted

any engine with a bore of over 4.00" is hard to control HC and detonation in.

 

The 6.0L/6L90 puts more power to the ground than the 8.1L/Allison did

 

 

 

I assume you have facts to back both of these claims up, right, because both are loaded

with B.S. if you ask me. The second quote, for sure and I've never, ever, seen the first one ever proved.

 

 

The problem with engines that have a bore over 4" is the surface area of the combustion chamber. Fuel will condense on all surfaces in a combustion chamber and will not burn, contributing to HC emissions. In addition, the slot that is formed between the top compression ring and the top of the piston is another area that HC tends to hide in, and of course the greater the bore, the more volume there is in that slot. Manufacturers have limited this area by locating the top ring as far up on the piston as they can, but it is still a significant source of HC emissions. The best way around the problem is going to a more under-square engine design, less bore but more stroke gets you the same displacement but minimizes combustion chamber surface area and upper ring slot.

 

The effects of cylinder bore on detonation are not as great as compression ratio, but the greater the bore the more likely an engine is to detonate. Flame front travel is a big factor, and it can be partially overcome with multiple spark plugs (Ford 6.2L, Dodge Hemi). It gets into the law of diminishing returns, increase the bore for more power, but you reach a point where you have to limit compression ratio and ignition timing to control detonation (you see why 8.1L's only make 330 h.p.?). Sure the BBC is great on 100+ octane or CNG/LNG!

 

Sorry, I can't find the dyno chart I had that compared an 8.1L/Allison to a VVT 6.0L/6L90. The 6.0L beat the 8.1L at nearly every speed. Yes, it's a bit of an apples-to-oranges deal. The VVT helps the 6.0L a lot, and the Allison gear and converter ratios are not optimal for a gas engine (the 6L90 has near perfect ratios for a gas engine, keeps it right in the middle of the power band). The information came from a GM Powertrain engineer.

 

 

I know the theory but again, I've seen side by side HC testing done between over square and square engines and they are no where near far enough apart to cause serious issues. They can be cleaned up with other methods and used quite nicely.

 

I can get as much GM Powertrain information as you'd like but on the street, loaded especially, there isn't a 6.0 VVT/6L90 TOUCHING an 8.1 with an Ally, period. That 8.1/Ally combo will pull circles around the 6.0 VVT/6L90 combo all day long and twice on Sunday.

 

 

GM did clean up the 8.1L enough to pass regulations, but that came at a cost. Terrible volumetric efficiency and poor fuel economy. It was better than the old TBI 7.4's, the head design of the 8.1L helps.

 

Really ashame GM Powertrain didn't go ahead with the V-10 LS. At 7.5L, it killed the 7.4L Vortec. Better emissions characteristics allowed higher compression ratios and more aggressive valve and ignition timing.

ChevyTech77 Senior Enthusiast

ChevyTech77

Posted
Posted

any engine with a bore of over 4.00" is hard to control HC and detonation in.

 

The 6.0L/6L90 puts more power to the ground than the 8.1L/Allison did

 

 

 

I assume you have facts to back both of these claims up, right, because both are loaded

with B.S. if you ask me. The second quote, for sure and I've never, ever, seen the first one ever proved.

 

 

The problem with engines that have a bore over 4" is the surface area of the combustion chamber. Fuel will condense on all surfaces in a combustion chamber and will not burn, contributing to HC emissions. In addition, the slot that is formed between the top compression ring and the top of the piston is another area that HC tends to hide in, and of course the greater the bore, the more volume there is in that slot. Manufacturers have limited this area by locating the top ring as far up on the piston as they can, but it is still a significant source of HC emissions. The best way around the problem is going to a more under-square engine design, less bore but more stroke gets you the same displacement but minimizes combustion chamber surface area and upper ring slot.

 

The effects of cylinder bore on detonation are not as great as compression ratio, but the greater the bore the more likely an engine is to detonate. Flame front travel is a big factor, and it can be partially overcome with multiple spark plugs (Ford 6.2L, Dodge Hemi). It gets into the law of diminishing returns, increase the bore for more power, but you reach a point where you have to limit compression ratio and ignition timing to control detonation (you see why 8.1L's only make 330 h.p.?). Sure the BBC is great on 100+ octane or CNG/LNG!

 

Sorry, I can't find the dyno chart I had that compared an 8.1L/Allison to a VVT 6.0L/6L90. The 6.0L beat the 8.1L at nearly every speed. Yes, it's a bit of an apples-to-oranges deal. The VVT helps the 6.0L a lot, and the Allison gear and converter ratios are not optimal for a gas engine (the 6L90 has near perfect ratios for a gas engine, keeps it right in the middle of the power band). The information came from a GM Powertrain engineer.

 

 

I know the theory but again, I've seen side by side HC testing done between over square and square engines and they are no where near far enough apart to cause serious issues. They can be cleaned up with other methods and used quite nicely.

 

I can get as much GM Powertrain information as you'd like but on the street, loaded especially, there isn't a 6.0 VVT/6L90 TOUCHING an 8.1 with an Ally, period. That 8.1/Ally combo will pull circles around the 6.0 VVT/6L90 combo all day long and twice on Sunday.

 

 

GM did clean up the 8.1L enough to pass regulations, but that came at a cost. Terrible volumetric efficiency and poor fuel economy. It was better than the old TBI 7.4's, the head design of the 8.1L helps.

 

Really ashame GM Powertrain didn't go ahead with the V-10 LS. At 7.5L, it killed the 7.4L Vortec. Better emissions characteristics allowed higher compression ratios and more aggressive valve and ignition timing.

 

Agreed on the 10 cyl LS engine but I think the huge spike in LD Diesel sales put that engine on the shelf.

yukon25008.1 Senior Enthusiast

yukon25008.1

Posted
  • Author
Posted

I dont completly undertand all of it..but i get what your trying to explain,

I just dont see why with todays technology thy cant make a 400 hp 600 tq big block, thats effecient like the smaller newer motors..is it because they dont want to put the time into it?

I can understand it from the business point, they just want to stamp them out quick and easy to make money,

If a porsche for instance can make 500 hp with like a 3.0 why cant gm take some time and engineering and make big hp and tq effeciently with a new big block?

Also is it not possible to make a new big block with the engine design that only uses 4 cyl,s until you get into it or the demand is required..This way you have a great effecient mpg getter while cruising..and when you have to pull/tow its there.

 

If there was a new/newer big block offered i would own a new body stlye GMC, and they have to know that..that theres a ton of us out here want more than the 6.0 but dont want a d-max.

It would be great if you could get and HD with a 7.0 that made good TQ..someone said the 7.0 is vettes only??

Dont you guys think they would sell great if there was a new improved 8.1 or even 7.4,escpecially if gm garunteed better mpg,s than previous. They also should realize alot of guys dont care what the gas mileage is when buying a truck to do what they want..I pull/haul alot of crap..campers,firewood,work stuff,stone,etc...but dont need a diesel but want more than a 6.0 for sure. Thanks guys for listening..; )

Daryl LBZ Senior Enthusiast

Daryl LBZ

Posted
Posted

I dont completly undertand all of it..but i get what your trying to explain,

I just dont see why with todays technology thy cant make a 400 hp 600 tq big block, thats effecient like the smaller newer motors..is it because they dont want to put the time into it?

I can understand it from the business point, they just want to stamp them out quick and easy to make money,

If a porsche for instance can make 500 hp with like a 3.0 why cant gm take some time and engineering and make big hp and tq effeciently with a new big block?

Also is it not possible to make a new big block with the engine design that only uses 4 cyl,s until you get into it or the demand is required..This way you have a great effecient mpg getter while cruising..and when you have to pull/tow its there.

 

If there was a new/newer big block offered i would own a new body stlye GMC, and they have to know that..that theres a ton of us out here want more than the 6.0 but dont want a d-max.

It would be great if you could get and HD with a 7.0 that made good TQ..someone said the 7.0 is vettes only??

Dont you guys think they would sell great if there was a new improved 8.1 or even 7.4,escpecially if gm garunteed better mpg,s than previous. They also should realize alot of guys dont care what the gas mileage is when buying a truck to do what they want..I pull/haul alot of crap..campers,firewood,work stuff,stone,etc...but dont need a diesel but want more than a 6.0 for sure. Thanks guys for listening..; )

 

 

 

This^

fajitas21 Enthusiast

fajitas21

Posted
Posted

To be honest with you, there are really not many who want larger than a 6.2L engine, that's why they aren't making them. GM spends a sizable amount of money on market trending to see where people will put their wallets...and while there's a bunch of us on HERE that agree with you, we aren't even 1% of all GM owners unfortunately.

 

Also, with CAFE coming up, GM isn't really able to listen to us, because if they don't make a truck that gets 25 MPGs in a few years, they have to stop selling it...

 

At this point, I completely believe you might be able to get a high-ranking GM guy to side with us on a 7.0L engine or something and STILL nothing would come of it, because at this point the CAFE regs are putting so much pressure on the auto industry to improve MPGs that a core staple of GM's business...truck sales...is in jeopardy.

 

Until the bleeding is stopped...expect AFM / lower gear ratios / Hybrids / better aerodymanics / Transmission efficiency improvements / Weight reductions to take precedence over any power gains.

 

One side note will likely be the introduction of Direct Injection, but that's typically a power gain AND MPG gain...and that's how GM will market it (as they should).

 

If a porsche for instance can make 500 hp with like a 3.0 why cant gm take some time and engineering and make big hp and tq effeciently with a new big block?

 

High HP and High Torque are quite different. Also, I don't want to pay $15000.00 for a premium engine option :(

yukon25008.1 Senior Enthusiast

yukon25008.1

Posted
  • Author
Posted

What is direct injection actually?

Just aking because im not sure. If every cylinder now has its own plug,injector,and coil..What could be more direct then that?

  • 2 months later...
C/K Man Enthusiast

C/K Man

Posted
Posted

Why cant they make a version of the corvette 7.0L for the HD trucks

 

 

I don't know the official reason, but I would imagine the siamesed cylinder walls might be part of it. If GM was going to make a larger displacement LS, my guess is they would use a longer stroke crank in a tall deck (LSX style) block. They could go to 6.6L with the same bore as the current 6.0L.. Hard to say what's coming right now since even the HD pickups will be subject to fuel economy standards. Also, GM was always against using aluminum blocks in HD pickups, but now that policy appears to be changing, as by most reports all the gasoline powered K2XX's (Gen. 5's) will feature aluminum blocks. In other news, there is considerable work being done right now to the old Big Block Chevy for use in medium duty trucks, as a CNG/LNG engine. Origin Engines and Power Solutions International are both working on CNG BBC's for highway use, some are up to 10.4L!

bagger97 Enthusiast

bagger97

Posted
Posted

The big block is dead, unless someone figures out a way to make gasoline from water :) How many semis are rolling with a gas motor? I could see a big block CNG motor to replace diesel, but not anytime soon.

 

 

They are still using Ford V10 and GM 496 cu in big block in large motor home chassis to keep the cost down. Also, the marine industry still offers the 496 GM big block.

 

2011 was the last year for the GM/Allison in motorhomes. Only the Ford V10 is left in gas.

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Latest Articles

  • Posts

    • Grumpy Bear
      Some Assembly is Required

      By Grumpy Bear · Posted

      Can it still be Assembled I?    Stribeck says that we need a certain amount of viscosity under conditions of load and velocity to prevent two surfaces of a know roughness from tearing each other asunder. And we have marketing trying to tell the masses that those two surfaced require less of that commodity due to more exact limits being placed on the same old clearances. We also know that there are limits to how hard something can before it becomes to brittle to be viable and to smooth to 'wet' the surface and that both of those conditions have been known and met since about the Second World War.    That viscosity value shook out at 10 centistokes at 212 F just under a hundred years ago.  Give this a look: [Anton Parr]     What is advertised is the Kinematic viscosity (mm2/s) or that which has been density adjusted but the value we are after is the dynamic viscosity (mPa.s) or true viscosity. You can see that this number is dependent on density thus base stock and temperature. You can also see that an SAE 30 doesn't reach that value in this example. However an SAE 30 that is at the upper end of the SAE 30 range; 12.5 cSt (mm2/s), might. 12.5 * .83 = 10.375 (mm2/s). If you could find an SAE 30 at the upper end these days.   Then there is the complication of viscosity modifiers or VII or VM, whatever you wish to call them. Polymers added to very thin base oils, perhaps 3 to 6 cP oils, that will meet the SAE *W30 spec at 'tested' shear rates and 100 C/212F  target temperature. So a polymer fortified base that is a fraction of the 10 cP requirement Stribeck insist upon.   This could be all well and good if those polymers didn't have two very problematic 'features'. They shear or loose viscosity both 1.) permanently and 2.) temporality. And they do both omitted in the advertised data with the distinct  purpose of deceiving the consumer of the actual operating state of the fluid. I've shown the example of Warren Oils COSTCO 10.91 cSt 5W30 formuation several times where the 100 C HTHS value is 6.9 cP!! That's the temporary shear down and with and SSI or shear stability index of 9.4 cSt. Note the intentional deception in using mixed units?    After a short while that 9.4 cSt oil has a viscosity corrected dynamic value of 7.8 cP. But as the SSI is still within the range of an SAE *W30 whose lower value is 9.3 cSt.    This allows them to continue to call this SAE 16 weight oil a 30 weight, the cake, and still meet the API requirements for fuel efficiency IMPROVEMENT mandated by the EPA. The eating of the cake. By the time you've worn out your motor doing the responsible thing by adhering to the warranty requirements, (the stick), you get deprived of the carrot, wear control. So sad, to bad.   So what can be done? Do I need actually say? [Anton Parr]       Even this must be monitored if the oil is on the low side and the VII an organic or you opt for a 0W40 with an even lighter base oil and more / higher MW VII. (Note the lower density of the 40 weight versus the SAE 30 mono-weight?)    There is another workaround. Temperature. An SAE *W30 run at a bulk temperature of between 180 and 195 F.    Being the belt and suspenders sort I am I do both. Run it cook and run it heavy.    In Part II I'll work the AW package. 
    • Atlas
      Wow I'm in a pickle. (Broke down truck) and a story.

      By Atlas · Posted

      So, do I go elbow-deep on this thing or list it for sale and play dumb? Seems to "runs good."   I'm about $1200 away from having: -a rebuilt injector ($300) -a new cat ($250) -a new cat back exhaust (OE style) ($300) -a new AC compressor ($200) -AC refrigerant charge ($150)   In theory, this should rectify the obvious detracting issues from its value and operability. Cold AC with a non-squeaking AC pulley both sounds and feels good. An exhaust that isn't cut/hacked in 17 different places and doesn't vibrate on a crossmember would make it sound and feel less janky. A working cat would help the stink, and will save the earth, but *if and only if* the fuel system is working properly, which would also address the intermittent "rich" CEL.   Heard a good one... CEL for "Rich condition" means you haven't spent enough money on the truck lately, and it's letting you know.   Rebuilding the injector would seem to be the most important part. Replacing the cat would be secondary. I don't think mine is plugged or overly restricted, but it might be a little restricted? I have no good way to tell other than seat of the pants feel. I hate the smell.   The current theory is I have a rich idle problem: A bad fuel pressure regulator, or a leaking injector(s) being the highest probabilities. I already replaced the FPR but that doesn't mean its replacement isn't also bad. It was a new part from Dorman, but the packaging looked like it had been sitting on a shelf for 20 years.   This is the (single) upstream O2 sensor shown at idle. I'm getting a lot of "rich" it seems. Sometimes it stays high like that and doesn't drop down. That makes me think it's processing injector leaks or a partially stuck open injector.     Other times it looks like this. Nice oscillations between rich and lean, which is what I think it should be. Under load and at speed, the oscillations are nice and tight and uniform looking, high and low.     Fuel trims suggest the PCM is compensating pretty hard at idle to pull fuel out. But it's not enough to trip a CEL. Something about slowing to a stop: brake vaccum booster, EGR, or the EVAP purge is delayed, or there's pooled fuel in the intake again that's draining into a cylinder is enough to set the CEL. Of course, in two days of driving, it hasn't set. I was hoping to actually look at the freeze-frame data when it sets. IAT is high because it's idling on an 83 degree day here.  
    • Another JR
      Gasser Subforum Has Been Quiet - - So, Regenerative Braking and Using L10

      By Another JR · Posted

      Have considered installing a DC to DC charger in your camper to replace your isolator?  
    • newdude
      Gas fill door

      By newdude · Posted

      Common failure.  You need to replace the fuel door housing.   The painted cover transfers over to the new housing.  To remove the old one there is 4 spots where you poke the plastic to release it.  
    • newdude
      Gasser Subforum Has Been Quiet - - So, Regenerative Braking and Using L10

      By newdude · Posted

      No such thing as regenerative braking on a pure ICE vehicle.     Regenerative braking is the re-capture of energy from electric motors and stores it in the battery pack.  So hybrids, PHEV and EVs have regenerative braking.     What you are seeing is the charging system changing modes is all.  Its likely entering charge mode for some sort of reason is all.  All of the charging modes will be listed below.   As for L10 vs D.  L10 turns off automatic grade braking.  L10 puts you in control of grade downshifts where in D it will automatically do it based on brake pedal position and other factors.  Otherwise L10 and D drive exactly the same aside from that one aspect.    Battery Sulfation Mode The BCM will enter this mode when the interpreted Generator output voltage is less than 13.2 V for 45 minutes. When this condition exists the BCM will enter Charge Mode for 2–3 minutes. The BCM will then determine which mode to enter depending on voltage requirements.   Charge Mode The BCM will enter Charge Mode when ever one of the following conditions are met:   Windshield wipers are ON for more than 3 s. Climate Control Voltage Boost Mode Request is true, as sensed by the HVAC control module via serial data. High speed cooling fan, rear defogger, and HVAC high speed blower operation can cause the BCM to enter the Charge Mode. The estimated battery temperature is less than 0°C (32°F). Battery State of Charge is less than 80%. Vehicle speed is greater than 145 km/h (90 mph) A current sensor malfunction exists. System voltage is determined to be below 12.56 V When any one of these conditions is met, the system will set targeted generator output voltage to a charging voltage between 13.9–15.5 V, depending on the battery state of charge and estimated battery temperature.   Fuel Economy Mode The BCM will enter Fuel Economy Mode when the estimated battery temperature is at least 0°C (32°F) but less than or equal to 80°C (176°F), the calculated battery current is less than 15 A and greater than −8 A, and the battery state-of-charge is greater than or equal to 80%. Its targeted generator output voltage is the open circuit voltage of the battery and can be between 12.5–13.1 V. When fuel economy mode is active, the generator is not charging, only maintaining open circuit battery voltage. The BCM will exit this mode and enter Charge Mode when any of the conditions described above are present.   Headlamp Mode The BCM will enter Headlamp Mode when ever the head lamps are ON (high or low beams). Voltage will be regulated between 13.9–14.5 V.   Start Up Mode When the engine is started the BCM sets a targeted generator output voltage of 14.5 V for 30 s.   Tow/Haul Mode (if applicable) Pressing the Tow/Haul Mode button located on the center stack, the vehicle system voltage is raised and the remote (non-vehicle) battery will be charged. Having the headlamps on will raise the system voltage and if the Tow/Haul button is applied it will not serve any purpose. The voltage is regulated between 13.9-14.5 V.      

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...