Talking Opposed Twin Torque Curves

[lynnmor 7,577]

1 hour ago, Achto said:

A quote from Briggs as to why they choose to switch to displaying the torque of an engine instead of the HP.

 

"While horsepower has been traditionally used for these applications to measure engine power, torque values are not new for engines. Gross Torque is the immediate twisting force required to turn a blade or pump at a given moment. Thus, torque is the way to measure the rotational force a machine can produce."

The real reason that Briggs dropped the HP rating and went with torque is that they got their *** in a wringer by giving inflated HP numbers and legal action ensued.  Look it up.  The quote is just spin to throw off the public.

[pfrederi 18,343]

As the ad said a few years ago...Horsepower brings you the beer (Clydesdales) torque twists off the cap...

[sgtsampay 117]

3 hours ago, roadapples said:

...@sgtsampay

I have no problem with bigger engines and more power. I have a 520 strictly for a 2 stage blower. That or a 60" deck is the only reason I would want anything bigger than a single 16.....

All I can say is drool!! Wow it’s so amazing! Such a rare combo. Show how capable our tractors are. 
 

back to topic, so it seems like several people agree the twin is really about marketing? They aren’t really that much better than a single? 

[ebinmaine 70,810]

2 minutes ago, sgtsampay said:

They aren’t really that much better than a single?

Depends on the definition of "better". 

Smoother running?

Yes.  

 

More powerful?

Yes...but... How much... And... as queried, how much does it really matter?

 

 

[adsm08 2,702]

Here is what I know about single vs twin.

 

A single cylinder engine can be started on a bench and held down by hand.

 

A twin will break your wrist.

[roadapples 6,983]

1 hour ago, sgtsampay said:

All I can say is drool!! Wow it’s so amazing! Such a rare combo. Show how capable our tractors are. 
 

back to topic, so it seems like several people agree the twin is really about marketing? They aren’t really that much better than a single? 

@wallfish has basically the same thing, only he built his hoe...

     

     Back to the topic...A good friend of mine who is gone but not forgotten, was an expert on small block chevys. I mean really. There are rules in the NHRA handbook because of him. He never cheated, he just did things that hadn't been tried yet. I asked him one time why the small block, what's wrong with the big block.  He kinda pondered for a moment, then said, "I'm not real partial to red headed women, but that don't mean there's anything wrong with em"....

    True story...

 

[RED-Z06 2,479]

You have to remember, kinetic energy, Onans had huge cranks and a massive heavy flywheel, they were a bit more sluggish but that was because they stored alot of power in the rotating assembly.  This also made them incredibly smooth.  The Kohlers ran a bit lighter flywheel, and briggs Even lighter than that.

 

The modern vanguards are snappier, more responsive, but...they have a much lighter reciprocal mass and rotating assembly, they store less kinetic energy and have to more quickly produce more power to maintain a speed, this is why Onans feel like there is a short delay to governor response, because there is.

 

I had a Deere 316 that the guy blew the 18hp Onan at 2400hrs and put on a 24hp Vanguard, it sounded stronger but in practice the engine spent more time on the governor, which is fine, it lacked the low end grunt the Onan had, the onan you could kick the deck on at idle but the briggs didn't like that.  The Vanguard made more peak horsepower, the Onan made more power under the curve.

 

[RED-Z06 2,479]

13 hours ago, adsm08 said:

Here is what I know about single vs twin.

 

A single cylinder engine can be started on a bench and held down by hand.

 

A twin will break your wrist.

My 18hp Vtwin generator pulls as easy as my 8hp generator, i wouldn't rope start either on a bench not bolted down though.

[kpinnc 13,798]

2 minutes ago, RED-Z06 said:

You have to remember, kinetic energy, Onans had huge cranks and a massive heavy flywheel, they were a bit more sluggish but that was because they stored alot of power in the rotating assembly.  This also made them incredibly smooth.  The Kohlers ran a bit lighter flywheel, and briggs Even lighter than that.

 

The modern vanguards are snappier, more responsive, but...they have a much lighter reciprocal mass and rotating assembly, they store less kinetic energy and have to more quickly produce more power to maintain a speed, this is why Onans feel like there is a short delay to governor response, because there is.

 

I had a Deere 316 that the guy blew the 18hp Onan at 2400hrs and put on a 24hp Vanguard, it sounded stronger but in practice the engine spent more time on the governor, which is fine, it lacked the low end grunt the Onan had, the onan you could kick the deck on at idle but the briggs didn't like that.  The Vanguard made more peak horsepower, the Onan made more power under the curve.

 

Actually makes sense. I've seen what I believe is exactly what you describe.

 

Perhaps some of the drag on my old Onan had some to do with it being relatively low hours but well used. I never checked the compression, but I assume lower compression would compound the effect. 

[sgtsampay 117]

19 minutes ago, RED-Z06 said:

You have to remember, kinetic energy, Onans had huge cranks and a massive heavy flywheel, they were a bit more sluggish but that was because they stored alot of power in the rotating assembly.  This also made them incredibly smooth.  The Kohlers ran a bit lighter flywheel, and briggs Even lighter than that.

 

The modern vanguards are snappier, more responsive, but...they have a much lighter reciprocal mass and rotating assembly, they store less kinetic energy and have to more quickly produce more power to maintain a speed, this is why Onans feel like there is a short delay to governor response, because there is.

 

I had a Deere 316 that the guy blew the 18hp Onan at 2400hrs and put on a 24hp Vanguard, it sounded stronger but in practice the engine spent more time on the governor, which is fine, it lacked the low end grunt the Onan had, the onan you could kick the deck on at idle but the briggs didn't like that.  The Vanguard made more peak horsepower, the Onan made more power under the curve.

 

this makes perfect sense! I didn't think that way. Makes sense of why the 13HP predetor engine "seemed" to have as much power as the 12HP kohler or so. Its because it reacted much better and had a higher torque curve. 

 

So again, its all the same power between the machines. Just different ways of accessing that power and putting it into usable work? 

[RED-Z06 2,479]

4 minutes ago, sgtsampay said:

this makes perfect sense! I didn't think that way. Makes sense of why the 13HP predetor engine "seemed" to have as much power as the 12HP kohler or so. Its because it reacted much better and had a higher torque curve. 

 

So again, its all the same power between the machines. Just different ways of accessing that power and putting it into usable work? 

In a sense yeah.  Like..my 10hp Kohler handled a 42" deck...didnt like it but it did it. 18hp briggs single struggled just as much but in a different way, it didnt have any bottom end..it took longer to make it bog but once it fell below the power curve it would just stop.  The kohler would keep chugging.

[sgtsampay 117]

Some more details to confuse people.

 

Edited January 25, 2022 by sgtsampay

[Snoopy11 5,717]

15 hours ago, ebinmaine said:

Depends on the definition of "better". 

Smoother running?

Yes.  

 

More powerful?

Yes...but... How much... And... as queried, how much does it really matter?

 

 

 

Smoother running is the main "plus" ...as horsepower can be accomplished with mere size of the engine... rotating assembly... etc.

 

15 hours ago, adsm08 said:

Here is what I know about single vs twin.

 

A single cylinder engine can be started on a bench and held down by hand.

 

A twin will break your wrist.

 

It would appear... that you have never felt a powerful single cylinder. The compression from my stroked 457... will break your arm. I found out the hard way... you bolt a monster single cylinder down to a work bench... it wants to pick the work bench UP...

 

Don

[RED-Z06 2,479]

I dont put a ton of faith into manufacturers power info and curves, let us not forget the massive industry wide class action suit that every manufacturer got dinged for misleading people on power ratings for decades.

 

Always thought it was odd that a 15, 16, 17 and 18hp briggs shared the same 28ci block, same head part number, same cam, carb, etc.

 

You can make a dyno graph look really good or really bad by tweaking a few variables 

[RED-Z06 2,479]

1 hour ago, Snoopy11 said:

 

Smoother running is the main "plus" ...as horsepower can be accomplished with mere size of the engine... rotating assembly... etc.

 

 

It would appear... that you have never felt a powerful single cylinder. The compression from my stroked 457... will break your arm. I found out the hard way... you bolt a monster single cylinder down to a work bench... it wants to pick the work bench UP...

 

Don

I put a custom Burris cam into a 6hp Kohler XKE, you couldn't recoil start it, just 6hp, compression release is a heck of a concept,  turned out the stock cam was good enough.

[Snoopy11 5,717]

2 minutes ago, RED-Z06 said:

I put a custom Burris cam into a 6hp Kohler XKE, you couldn't recoil start it, just 6hp, compression release is a heck of a concept,  turned out the stock cam was good enough.

Very true. I find that the recoil on my single cylinder builds... can literally rip the recoil out of your hand... or... if you hang on... do more damage to you...

 

Don

[kpinnc 13,798]

1 hour ago, RED-Z06 said:

Always thought it was odd that a 15, 16, 17 and 18hp briggs shared the same 28ci block, same head part number, same cam, carb, etc.

 

You can make a dyno graph look really good or really bad by tweaking a few variables

 

Same with Onan P216, P218, and P220. P224 has many of the same components as well.

[RED-Z06 2,479]

18 minutes ago, kpinnc said:

 

Same with Onan P216, P218, and P220. P224 has many of the same components as well.

The 16hp was 709cc, 18hp was 781cc, 20hp was 781cc, 24hp was 980cc.

 

16-20 shared bores

16 had a smaller stroke and 0.5 lower compression. 

24 had a much larger bore and stroke.

 

18 and 20 are pretty much the same but...darned if 220s don't always sound more aggressively cammed.

[kpinnc 13,798]

10 minutes ago, RED-Z06 said:

18 and 20 are pretty much the same but...darned if 220s don't always sound more aggressively cammed.

 

And I have no data to support this, but seems like the 20s run hotter too. Maybe nothing more than numbers produced (possibly more 520s than 416 and 518?), but 520s certainly seem to drop the rear valve seat more often than other Onans. 

[RED-Z06 2,479]

39 minutes ago, kpinnc said:

 

And I have no data to support this, but seems like the 20s run hotter too. Maybe nothing more than numbers produced (possibly more 520s than 416 and 518?), but 520s certainly seem to drop the rear valve seat more often than other Onans. 

I keep hearing about this phenomenon on Onans but ive yet to see it first hand and you'd think in the hot south it would be common 

[ebinmaine 70,810]

1 hour ago, kpinnc said:

520s certainly seem to drop the rear valve seat more often than other Onans

 

37 minutes ago, RED-Z06 said:

I keep hearing about this phenomenon on Onans but ive yet to see it first hand and you'd think in the hot south it would be common 

 

I don't own or have any direct experience with a 520. 

From what I'm gathering purely by reading... It seems to ME it's a matter of owner maintenance. 

A LOT of the 520s are used as mowing machines for large areas. I think it's fair to say most folks just don't take the time to properly clean up equipment. 

An engine clogged with grass clippings and dirt isn't going to breathe past the cooling fins. 

 

[Achto 28,806]

7 hours ago, RED-Z06 said:

You have to remember, kinetic energy, Onans had huge cranks and a massive heavy flywheel, they were a bit more sluggish but that was because they stored alot of power in the rotating assembly.  This also made them incredibly smooth.  The Kohlers ran a bit lighter flywheel, and briggs Even lighter than that.

 

Very good point. Although kinetic energy will not effect an engines HP or torque out put, it will effect it's responsiveness. Garden tractor pullers who run modified engines will ditch the 18lb flywheel on a Kohler K model engine and replace it with a 36lb flywheel. They are not concerned with how fast the engine will respond, they just want it to maintain the max RPM once it gets there. (It's kind of weird listening to them wind down from WOT to idle. It takes a good 20 seconds or more) Racers on the other hand will ditch the cast iron flywheel and switch to a billet aluminum one. They want the engine to respond quickly when they step on the peddle. (Response from WOT to idle is very quick on these engines. Less than a couple of seconds) Kinetic energy can make the same engines with virtually the same modifications act completely different. 

Edited January 25, 2022 by Achto

[Achto 28,806]

One large factor in the amount of torque that an engine has is the stroke. When you compare same HP engines from different manufacturers, or same manufacturer different year model you will find that the one with the longer stoke will always have more torque. This makes perfect sense as torque is the unit used to measure the twisting force on the crank shaft. A longer stroke puts the crank pin further away from the center of the crank shaft. Same theory as getting a longer wrench or putting an extension pipe on a wrench to loosen a bolt. Further away from the pivot point allows you to exert more torque.

 

One of the most impressive Harley based engines that I drove was what I call a square engine. It was an S&S 100cu inch engine. The reason that I call it a square engine is because it had a 4" bore and a 4" stroke. On our dyno it put out 102hp and 105lb-ft of torque at the rear wheel. Amazing that the max HP and max torque was so close. BTW it was a blast to drive. 250mm wide tire on the back that you could light up when ever you wanted. Actually had to be a little careful getting on the throttle after shifting so is not to have the back end scoot out from under you.

Edited January 25, 2022 by Achto

[lynnmor 7,577]

3 hours ago, RED-Z06 said:

The 16hp was 709cc, 18hp was 781cc, 20hp was 781cc, 24hp was 980cc.

 

16-20 shared bores

16 had a smaller stroke and 0.5 lower compression. 

24 had a much larger bore and stroke.

 

18 and 20 are pretty much the same but...darned if 220s don't always sound more aggressively cammed.

 

The 20 HP Onans have a higher lift on the intake cam lobe.

[kpinnc 13,798]

1 hour ago, ebinmaine said:

 

I don't own or have any direct experience with a 520. 

From what I'm gathering purely by reading... It seems to ME it's a matter of owner maintenance. 

 

I don't want to open that old discussion here, but there is also the theory that the belt guard impedes some of the airflow at the rear cylinder. That's why you see variations of holes and slots cut into the belt guard. Clippings on the fins is a known issue, but as I said, it's been well discussed before.

 

BUT, my point was that there is some correlation that says P220 equipped Wheel Horses fail due to the valve seat more often than P216 and P218 equipped machines. Since the majority of tractors in this range carry 42 and 48 inch decks, I don't think it can be blamed soley on the higher load of the 60 inch deck that the 520 can carry. It seems that the P220 just runs hotter.