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6.2 vs 6.5 RPMs

A

Acesneights1

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So me and Dave were PM'n about why it seems a 6.5 can be comfortable at 2500+rpms and a 6.2 wants to blow something. I'm guessing it has to do with the 6.2's having higher compression ???
Ideas ? Opinions ?
 
I'd say that's about where the 6.2 was and it seems i've killed a lifter, so i'm curious why.

My 6.5's been taken up to just short of redline when driving before and it doesn't care.

I"m curious as well if it's compression or what? I can't think of anything else?
 
It could be fueling or ?. How does the 6.5 get its size, simply an overbore? if so, it could be it likes the additional air flow and its not straining so hard.
 
I think the 6.2 just roars more because there isn't a turbo there to silence the intake. My 91 reved past 3000 rpm when cold before it would shift. Very loud with the cold advance on.
 
bk95td said:
I think the 6.2 just roars more because there isn't a turbo there to silence the intake. My 91 reved past 3000 rpm when cold before it would shift. Very loud with the cold advance on.
Click to expand...

That is true if we are comparing turbo to n/a, turbo's give you a broader powerband.
 
Most 6.2 trucks don't have tachs on them. They do roar moreso than a 6.5td but my governor doesn't kick until 3800rpm or so on my 6.2
 
There should be absoluteluy no reason why a 6.2 and 6.5 "Safe RPM" should be different.

The tiny difference is Comp ratio wont make squat.

The governors are set to about the same upper limits (One is mechanical the other is electronic ????????????? same outcome though.

A little 6.2 should roar along sitting right on the governor and be happy as a clam all day long.

I used to run my 1986 6.2 Burb 4x4 to LA and back from Portland and on the big road at 70 the little 6.2 was howling. (back before the OD trannies in the 2500 trucks

Little creature never had any issues at all.

The 6.5 TD's generally dont run that high RPM because most rigs have the 4L80 boxes or 5 speeds that have the OD.

I would not worry about the RPM as long as its reasonable.

I would not want to listen to one of these screaming along at 3000 RPM all day long.

Sort of like the old days with a 92 silver detroit 2 stroke.


Missy
 
It breaks my heart to know it's sitting in a sand pit right now not running, decaying being used for a storage tank but I can't justify buying it back. If I won the lottery though.......
 
The GM Coach I had was fitted with the 6V 71 and an Allison V drive.

40 feet aft of the driver and the little detroit was very quiet.
Cross mounted up on its side.

Had a Pete 359 with an 8V92 silver with twin stacks. OMG that beast was noisy


Missy
 
8v92T ? or NA ? The T's could crank some seriuos HP if you put the (N45s ??) in and got somene who knew how to tune the racks right. Damn that sucker could fly. I drove a KW short hood with an 8v92T and it was tuned up to about 475HP.The 2 stokes always lacked a little low end but tp end damn it would run.
 
8V 92 TA is what I had in the Pete.
It was set on KILL too. Made a buttload of power.

Fuel hungry as all get out about 3.2 MPG OMG what a HOG

A Buzzzzzin Dozen is a real force to be dealt with.

When I first got into dump trucking back in 91 there was a fellow I used to haul with when we worked for all the pits around here.

He had an 84 Pete long hood with a V12T in it. OMG that beast could run.

I was running an 8V71 (Stocker) and it was OK but that 12 would fly up the hills.

He would give the guys with the big cats a bad time for sure.

My 500 HP Cat has loads of grunt. Need it for sure when your dragging 105,500 up 15% grades at times.

Got on a 21.2% grade a while back, DAMN really got it down into the business gears. Had to make a full stop, hang a hard right turn, make a near U and up this 21.2% grade.

Yes its posted at the top "STEEP DOWNGRADE" do fooling Buckwheat.

I was down in the "Numba one" hole in the 18, still had granny but thats too slow.

Truck has the 18718-B fuller 18 speed and 4.10 Butt gears. Two speed rears with some serious lower ones was on my mind when I ordered the truck but the two speed rears add a lot of weight plus $$$$$$$$$$$$$$$$$$$$$$$$$

Truck weighs #26,300 empty with a loaded limit of #56,500

Oh yesss the Youngins dont have a clue about such "Iron monsters" from the past.

You dont see the V12 much anymore in trucks. Occasionally an old horse will pop up, usually an old dump truck or a vintage hauler thats making a special apearance at a truck show/car show or ???

See them once in a while still used in the older Mom and Pop gravel companies in a big pit truck Old T REX or ???

Too costly to run down the highway. (Coal Rollers)

There is getting to be very few 2 strokers running in commercial stuff anymore.
Some fire dept's still have some 92's in their rigs.
The 60 detroit has pretty well taken over the scene.

Cat will be out of the truck market in the near future due to the ever excalating enviro crap.

Cat decided its just not worth the bother to try and keep up with the idiots at EPA.

Just get a good system working well and its time for more redesign.

The 3406E 600HP was the pinacle of truck engines. Good power with great reliability.

The Detroit 60 is not a bad engine but is a little lighter in structure than I like to see, at least for the power they produce.

Cummins is an OK power plant but I am just not a Cummins fan.

The stuff the Big Dog produces (MACK) I have had zero contact with other than seeing them going down the road.

Local outfit has 4 heavy haul transfers on Mack chassis and they love them.
2 are a few years old and have that huge Mack V8 OMG what a beast.


Later

Missy
 
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Thing I never quite got was turbo charging something that was supercharged. Seems to me the impellors on the blower would limit extra boost from the Turbo but It works. Turbo on my 6v 92T was monsterous.
 
Acesneights1 said:
Thing I never quite got was turbo charging something that was supercharged. Seems to me the impellors on the blower would limit extra boost from the Turbo but It works. Turbo on my 6v 92T was monsterous.
Click to expand...

the two stroke detroits aren't really "supercharged" the displacement from the blower is just enough to fill the cylinders as the compressor acts as the intake valve...the blower moves a fixed volume of air per revolution, when the air is compressed it becomes more dense per that volume, so with the turbo boost you are just moving x volume of compressed air vs x volume of uncompressed air.
 
For quite a few years I drove a turboed-supercharged 318 Detroit 2 stroke dump truck. It was called a 350 horse 318. And I still have hearing problems because of it!
 
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