GM 8.1...

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hattaresguy

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In the marine world I love this motor, puts out all kinds of power despite its appetite for fuel!

That yellow Ford with is spark plug launching, cam phaser breaking 5.4 was like what...
 
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I love them in boats, they run like diesels just burn about 40gph doing it! Nothing moves a heavy boat onto plane like a pair of big blocks! Small blocks even the 6.2's fall flat on their faces with enough weight.

Nothing pushes weight like cubic inch's, real world 370hp out of a 6.2 is less than 350 out of an 8.1!
 
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OK?

This is a 300,000Km+ 302 on a set of M/T ET Streets (drag radials)

Big%20Burn-Out.jpg


It is pretty easy to light up the tires as long as you don't have traction control or something in the way.

I don't see the connection between lighting the tires up and the 8.1 being a good engine
21.gif


Maybe a video of a nice craft with a pair of BBC's in it getting up on plane quickly would have been more in-tune with what you are trying to demonstrate?
 
And one is a heavy duty pickup and the other is a sports car.

Can I post a video of an Camaro doing a burnout now?

I see a *little* difference there... apparently not everyone does.

But yes, we know... in every possible situation, even when the comparison is completely wacked... that the Ford is always better.

Thanks.
 
Originally Posted By: mrsilv04
And one is a heavy duty pickup and the other is a sports car.

I see a *little* difference there...


Yeah, it is easier to do the burn-out in the truck, LOL!
wink.gif


Seriously though, I just don't see the relevance of lighting the tires up in relation to how good the engine is
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My old F-250 with the straight-6 would light 'em up too and it was far from a power house.

The 8.1L is a great engine. The BBC family has a long reputation for making good power and fantastic reliability. I just don't see the connection between that and lighting the tires up
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Originally Posted By: mrsilv04


But yes, we know... in every possible situation, even when the comparison is completely wacked... that the Ford is always better.

Thanks.


That wasn't my point at all (though the OP did slag on the 5.4L because he hates them and has mentioned that a few dozen times in the past). I just don't see the connection between a burn-out and an engine being good. It doesn't take much to light the tires up on a pick-up.
 
Originally Posted By: mrsilv04
And one is a heavy duty pickup and the other is a sports car.

Can I post a video of an Camaro doing a burnout now?

I see a *little* difference there... apparently not everyone does.

But yes, we know... in every possible situation, even when the comparison is completely wacked... that the Ford is always better.

Thanks.


any decent powered pickup will do it. Trucks have no weight in the rear end. My ram 5.9 will do that as long as you want it to but why would you want to?
 
Originally Posted By: ram_man
Originally Posted By: mrsilv04
And one is a heavy duty pickup and the other is a sports car.

Can I post a video of an Camaro doing a burnout now?

I see a *little* difference there... apparently not everyone does.

But yes, we know... in every possible situation, even when the comparison is completely wacked... that the Ford is always better.

Thanks.


any decent powered pickup will do it. Trucks have no weight in the rear end. My ram 5.9 will do that as long as you want it to but why would you want to?


EXACTLY
cheers3.gif
 
Ehhh, cut the OP some slack. It was a burnout video from an 8.1. Right, lots of cars can burn up a set of tires, and pickups are pretty light in the back.

I agree Id rather see a boat doing it
smile.gif


I am interested in the 8.1 vs 6.2 comments... No replacement for displacement, but if the power curves are the same, both make the same HP/Tq at the same RPMs, then all there is is driveline inertia, including within the engine. And thats more a transient capability than an acceleration one.

That's a pretty interesting discussion there...
 
Originally Posted By: JHZR2
That's a pretty interesting discussion there...


When we were doing IC stuff, one of the parameters was (for want of a better word), the area under the torque curve...

In theory, you can take a screamer and gear it down to give the same tractive effort, and a lugger and gear it up...but a long flat torque curve, particularly in the absence of gear changes is different...if that makes sense.

To keep on page, here's Big Block Ford...and belts, and gears.
 
Originally Posted By: hattaresguy
Nothing pushes weight like cubic inch's, real world 370hp out of a 6.2 is less than 350 out of an 8.1!
Because real world power is torque. Hp is a mathmatical engineering abstract for comparison purposes. Torque spins tires and get boats up on plane.
 
Originally Posted By: 72te27
Originally Posted By: hattaresguy
Nothing pushes weight like cubic inch's, real world 370hp out of a 6.2 is less than 350 out of an 8.1!
Because real world power is torque. Hp is a mathmatical engineering abstract for comparison purposes. Torque spins tires and get boats up on plane.


horsepower is basically torque at RPM. It is work being performed. You can apply torque and do no work (not move it) but in order to have any measurable horsepower work needs to be performed. The rate at which that work is being performed is RPM and the work itself is torque.

Providing more rotational force (torque) to a propeller for example and being able to maintain that rotational force as RPM increases is what gets the boat up on plane quickly (as Shannow mentioned). You can gear down an engine that makes similar HP but less torque but ultimately it likely will not have the same area under the curve.

That said, in modern DOHC setups with the ability to manipulate camshaft timing you can get torque curves that are impressively flat out of engines with less displacement. But that's not really on topic for this thread.

Technically, with appropriate gear ratios (multi-speed gearboxes) you would be able to cut the same ET or plane the same boat with two different engines making the same HP even if one had half the torque. But that's not practical. You see this in race cars with high strung 4-bangers with narrow power bands high in the RPM range. They are geared deeply and the transmission has close ratios to keep the engine in the power band. That isn't how engines are setup in boats and it wouldn't make sense to try it either. There would be zero benefit to doing this over just using an engine that makes lots of low-end grunt with a flatter curve and gearing it in the traditional manner and taking advantage of that.
 
Originally Posted By: Shannow
Originally Posted By: JHZR2
That's a pretty interesting discussion there...


When we were doing IC stuff, one of the parameters was (for want of a better word), the area under the torque curve...

In theory, you can take a screamer and gear it down to give the same tractive effort, and a lugger and gear it up...but a long flat torque curve, particularly in the absence of gear changes is different...if that makes sense.


I here ya, and take a look at the two:

2009_62l_l9h_silverado-ltz.gif


44456d1188512329-graph-8-1l-factory-dyno-l18curve.jpeg


Obviously the 8.1 makes more torque down low and continuously. Its just that max torque is at higher RPM that makes the HP ratings higher on the 6.2. I agree with you completely.

But my point was, if the 6.2 was modified to make similar max torque at similar RPMs as the 8.1 (i.e. similar area under the curve from idle to max RPM for the 8.1, even if the 6.2 could be stretched out to higher RPMs), then the only difference would be reciprocating mass, which relates back to transient capability and not getting torque to a load.
 
Originally Posted By: JHZR2
Originally Posted By: Shannow
Originally Posted By: JHZR2
That's a pretty interesting discussion there...


When we were doing IC stuff, one of the parameters was (for want of a better word), the area under the torque curve...

In theory, you can take a screamer and gear it down to give the same tractive effort, and a lugger and gear it up...but a long flat torque curve, particularly in the absence of gear changes is different...if that makes sense.


I here ya, but take a look at the two:

2009_62l_l9h_silverado-ltz.gif


44456d1188512329-graph-8-1l-factory-dyno-l18curve.jpeg




The 6.2 you posted is VVT. That may have a significant effect on the torque curve FWIW.
 
Originally Posted By: OVERKILL

The 6.2 you posted is VVT. That may have a significant effect on the torque curve FWIW.


It may, but again its not my point.

What I was theorizing about is a 6.2L engine and an 8.1L engine with identical HP/torque ratings and the same "area under the curve" from idle to some higher RPM. Say a modified 6.2 engine.

If power and torque were equal, so the only difference was block and pistons... would it make any difference...

Originally Posted By: JHZR2

I am interested in the 8.1 vs 6.2 comments... No replacement for displacement, but if the power curves are the same, both make the same HP/Tq at the same RPMs, then all there is is driveline inertia, including within the engine. And thats more a transient capability than an acceleration one.

That's a pretty interesting discussion there...
 
Originally Posted By: JHZR2
Originally Posted By: OVERKILL

The 6.2 you posted is VVT. That may have a significant effect on the torque curve FWIW.


It may, but again its not my point.

What I was theorizing about is a 6.2L engine and an 8.1L engine with identical HP/torque ratings and the same "area under the curve" from idle to some higher RPM. Say a modified 6.2 engine.

If power and torque were equal, so the only difference was block and pistons... would it make any difference...


They should perform basically identically. Actually the 6.2L, if having a lighter rotating assembly, should accelerate a bit faster if anything.
 
Originally Posted By: OVERKILL

I don't see the connection between lighting the tires up and the 8.1 being a good engine
21.gif




I'm not seeing it either.
 
Originally Posted By: OVERKILL
Originally Posted By: JHZR2
Originally Posted By: OVERKILL

The 6.2 you posted is VVT. That may have a significant effect on the torque curve FWIW.


It may, but again its not my point.

What I was theorizing about is a 6.2L engine and an 8.1L engine with identical HP/torque ratings and the same "area under the curve" from idle to some higher RPM. Say a modified 6.2 engine.

If power and torque were equal, so the only difference was block and pistons... would it make any difference...


They should perform basically identically. Actually the 6.2L, if having a lighter rotating assembly, should accelerate a bit faster if anything.


Yeah that's what I was getting at. IF (big if I guess) the specs were the same, the smaller engine may have some favorable traits (mass, etc).

Its not an electrical generator, so transient ops arent an issue. Less total and reciprocating mass are benefits...
 
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