True or false a 4stroke has better low end torque

[boater1234]

Re: True or false a 4stroke has better low end torque

Is that with a stock prop?So your boat gets up and goes you say.Why is it so many people have problems with 4strokes getting on plane then?I can't figure this theory out.I see on forums all the time that i visit about planning problems with all kinds of 4strokes from the little 9.9's to the big boys.All they say is i wish i had my 2stroke back.Maybe it's just a case of most people don't know how to prop a 4sstroke or is this just what you get with some 4strokes?I never hear a peep about a 2stroke having problems getting on plane only 4strokes,that is what scares me away from getting one.

 

[QC]

Re: True or false a 4stroke has better low end torque

4 strokes are almost always heavier for the same power output, annnnd, some ratings and models have less torque. Period, it's physics, can't really change it as a general rule.

 

[boater1234]

Re: True or false a 4stroke has better low end torque

Yes you are right but the 4strokes are getting much closer to the weight of some 2strokes.Some of the new yamahas like the 70hp and the new v max sho's are darn near close to etecs weight if not less.For some reason or another no one seems to care about the smaller motors as there is very little to go on as far as performance.Funny to as i have heard from several dealers the 15/20 4strokes of all brands sell more then any other motors in the world,yet you never can get much reasearch on them.It's mostly the bigger motors that get all the publicity.

 

[RRitt]

Re: True or false a 4stroke has better low end torque

Very interesting RRITT.So basically the 4stroke has more of the advantage like you said except when the 2stroke is spinning at the perfect speed.I guess we will never know what that speed is though right.So overall through out the rpm range the 4stroke will fare better.A car seems to have great get up and go when you floor them,so i guess this would be the same concept your saying.One thing i have noticed is almost all the 4stroke motors have way better gear ratios then 2strokes to make up for the power loss.Suzuki is one of those companys that is doing that with almost all their motors.One day they will have these 4strokes a ton lighter and more powerfull then ever.I think they are very close to getting that done.Look at the new 70hp yamaha at like 257lbs compared to their own 75hp 4stroke at 369lbs.The original 70hp 2stroke which i had a few yrs ago was at 238lbs so they are getting real close to weight.Makes you wonder though what are they taking out of these motors to make them over 100lbs lighter,or they are made way cheaper.Alot of plastic on these newer motors.

the perfect speed is designed by the engineers. It is where you get your best gas mileage since the least amount of unburnt fuel is wasted.

Another thing to consider is that a 2 stroke gets power on every rotation while a 4 stroke is every other. On 1 and 2 cylinder engines the 4 strokes are going to have longer gaps between power and will be less responsive to throttle changes.

which - btw - i would guess is why the etec pulled the yammie underwater. It revved faster and prevented the yammie from gaining momentum. Like letting a clutch out in fourth gear. They just bogged the yammie down and never let it get started.

 

[dingbat]

Re: True or false a 4stroke has better low end torque

Wonder if there will be a rematch of the infamous E-tec vs. Yamaha 4 stroke commerical? The Yamaha has since lost 40 lbs and increased its displacement by 25%. Same outcome?

E-Tec

Engine type
V6 90?
Weight
530 lbs
Displacement
3.2L (200 ci)
Horsepower Rating at Propshaft
225 HP (168 kw) @ 5150 RPM
Full Throttle RPM Range
4500 - 5800 RPM
Alternator output
50 Amps

Yamaha OffshoreT

Engine Type
V6 60?
Weight
562 lbs
Displacement
4.2L (254 ci)
Horsepower Rating at Propshaft
225hp at 5500 rpm
Full Throttle RPM Range
5000 ~ 6000
Alternator Output
70 Amp

 

[jbjennings]

Re: True or false a 4stroke has better low end torque

Why is it not a fair test on the yamaha/etec video? It seems pretty simple to me. The etec pulled the thing under. It has better power from the start, or it wouldn't do that.........
All the 4-strokes I ever tried couldn't get my boat to plane nearly as fast as a 2 stroke of equal hp. That said, I haven't tried a lot of 'em. If I have to buy a computer controlled motor, I'd probably buy the etec.
Just my opinion....
JBJ

 

[RRitt]

Re: True or false a 4stroke has better low end torque

Wonder if there will be a rematch of the infamous E-tec vs. Yamaha 4 stroke commerical? The Yamaha has since lost 40 lbs and increased its displacement by 25%. Same outcome?

E-Tec

I don't think its a fair fight. What you are really testing is which engine can rev fastest in the first 1/10th of a second. Whichever engine can do that will move forward while pulling the other engines propellor backward. That will create even more bog-down making it even harder for the other engine to rev up into its power curve.

Its like when the guys on TV saw through a tin can to show you how their $5 stamped steel serrated edge knife is way better than the $150 carbide steel flat blade knife. It is an intentionally deceptive test. The serrated knife will always cut tin cans better.

 

[boater1234]

Re: True or false a 4stroke has better low end torque

JB and dingbat why won't etec do a video of 2 equal direct injected motors,because they will not have the same outcome so in all said it is a unfair test.Like i said get the new v max sho 150 or 175 or yamahas HPDI outboard and then lets do some testing.It will never happen as the outcome will be far different.How can you say it's a fair test.They are 2 totally different engines on the same boat.Do a 2stroke vs a 2stroke and that is how you you will be able to see how much power each engine really has.Like i also said i'm not doubting for a minute that the etec is a great motor but there dvd is very misleading.

 

[QC]

Re: True or false a 4stroke has better low end torque

Who said that business was fair? Get over that. The comparison was their 2 stroke (ETEC) aginst the other guy's 4 stroke. Of course they knew they'd win, and of course they know when they might not and of course they publish the one they like. It is up to independent organizations to make "fair" tests. If you have to sell X against Y that's what you do, sell it . . .

 

[RRitt]

Re: True or false a 4stroke has better low end torque

FWIW,
seems like a moot argument to me. E-tecs weigh too much. If I want a 2stroke it is because i like the way my boat sits with a lighter engine. Otherwise I'll take the four stroke and burn cheap gas as I idle through all the manatee zones.

 

[jay_merrill]

Re: True or false a 4stroke has better low end torque

The ETEC video is very clear. There is no gimmickry. Same boat, same weight, same everything. ETEC 150 on one, Yamaha 4-stroke 150 on the other. The ETEC didn't just out-power the Yammy by a little - it sank the other boat!

As for comparisons to newer Yammies, there are two key issues. The HPDI is a two-stroke and the point of this discussion is two-stroke v. four-stroke. Secondly, the Yamaha SHO engines are of greater displacement for a given horsepower/torque rating. In other words, they are less efficient engines, because it takes more litres/cubic inches to develop as much power as their smaller competitors. In fact, you could go as far as to say that the Yamaha SHO engines are "derated."

If you were to look at Yamaha's promotional materials, you would also notice that while they compare the SHO engines to both Evinrude and Mercury on all other issues, they don't in regard to fuel consumption. Given that the SHO 250hp model is .8 litres larger in displacement than the ETEC 250 and 1.2 litres larger then the Mercury Optimax, this is not surprising.

My point is not to say that the Yamahas are bad engines. In fact, they are great engines and the efforts to reduce weight are great. Still, the relationship between torque and number of power strokes is pretty clear. Without increased displacement, supercharging, etc., more power pulses is going to provide more torque.

 

[fishrdan]

Re: True or false a 4stroke has better low end torque

the ETEC literally pulled the stern of the boat with the Yamaha under water and sank it.

I've seen that in the past and looked at it again, paying real close attention to the "test" In the test;

- the Etec is taken WOT a second or 2 before the Yamaha is taken WOT
- the Etec's prop wash is almost to the Yamaha before the Yamaha begins to "churn" the water.
- The Etec's boat is moving forward before the Yamaha is taken WOT

Pay lose attention at :50 and beyond....

http://www.youtube.com/watch?v=_-7I00cZUE0

I really don't see how the Yamaha failed, Evinrude just figured out a clever way to sink a boat

 

[dingbat]

Re: True or false a 4stroke has better low end torque

Without increased displacement, supercharging, etc., more power pulses is going to provide more torque.

That's my question. What does a 25% displacement advantage (4.3L vs. 3.2L) in favor of the new 4 stroke bring to the table?

 

[QC]

Re: True or false a 4stroke has better low end torque

That's my question. What does a 25% displacement advantage (4.3L vs. 3.2L) in favor of the new 4 stroke bring to the table?

Typically 25% more air, so the ability to burn 25% more fuel, so theoretically 25% more torque per firing event, so at the same RPM 25% more horsepower. Automatic? No; it depends on what they are trying to achieve. If it was automatic then there would never be any difference between engines of the same displacement . . .

Edit: Actually I think that would be 12.5% more horsepower as we still have the 4 stroke every other rev thing. Need to noodle on that for a few.

Edit 2: OK, to clarify, 25% more air per intake stroke = 25% more fuel burn per firing event, which is 25% more torque (work) per firing event, so 12.5% more torque sustained, so 12.5% more horsepower (power) at any given RPM. All POTENTIAL or THEORETICAL for a 4 stroke.

For a 2 stroke it would be theoretically 25% more air = 25% more fuel per firing event which is 25% more torque which is 25% more power (add RPM). Which points out the THEORETICAL benefit of a 2 cycle for power density (power for a given size at the same RPM)

 

[RRitt]

Re: True or false a 4stroke has better low end torque

The ETEC video is very clear. There is no gimmickry. Same boat, same weight, same everything. ETEC 150 on one, Yamaha 4-stroke 150 on the other. The ETEC didn't just out-power the Yammy by a little - it sank the other boat!

So Evan challenges a Yami to a shootout. In classic old school western style Evan has a horse, a rifle, and a six-shooter. Yami, on the other hand, is all modern with a computerized M1A1 Abrams tank with full armor, infra-red, and night-vision capabilities. As Yami is climbing into the tank Evan pulls out his pistol and shoots him. Thus it is conclusively proven that a pistol has more firepower than an M1A1 tank.

 

[cajuncook1]

Re: True or false a 4stroke has better low end torque

Wow, alot of discussion here!!! To me, I'm just happy with a motor (4 or 2 stroke) that will consistently run good and get me on the lake to do some fishing Also a motor that is easy on the pocket book and will last me with proper maintenance.

Lord, I lay me down to sleep. I am going fishing so please let my motor start up quick and never quit, so I can catch some fish to keep!!!

AMEN!!!

 

[Cannondale]

Re: True or false a 4stroke has better low end torque

Working from the numbers in that graph, the "225" HP E-Tec puts out a peak of 240 HP at 5500 rpms, while the Yamaha puts out a peak of only 217 HP at 6000 rpm - and that's IF the numbers on the graph are to be believed. The source of that graph - salesmen.

You seem not to understand that the chart presented is showing peak TORQUE, not horsepower.

 

[QC]

Re: True or false a 4stroke has better low end torque

You seem not to understand that torque x RPM / 5252 = horsepower, so a graph with both torque and RPM always indicates horsepower whether it wants to or not. In fact, if torque does not include RPM it is pretty much useless and if it does include RPM then, again, horsepower is what you get. That's what our metric friend (should use nm and kW) is 'splaining . . .

 

[jay_merrill]

Re: True or false a 4stroke has better low end torque

I've seen that in the past and looked at it again, paying real close attention to the "test" In the test;

- the Etec is taken WOT a second or 2 before the Yamaha is taken WOT
- the Etec's prop wash is almost to the Yamaha before the Yamaha begins to "churn" the water.
- The Etec's boat is moving forward before the Yamaha is taken WOT

Pay lose attention at :50 and beyond....

http://www.youtube.com/watch?v=_-7I00cZUE0

I really don't see how the Yamaha failed, Evinrude just figured out a clever way to sink a boat

I think you better look at the video again. The operators push to WOT on the count of three and the Yamaha powered boat actually moves before the ETEC powered boat, which is a clear indication that the Yammy oeprator actually pushed the power on, before the ETEC operator.

The difference in propwash is simple - the ETEC produces more torque and produces it faster, so the ETEC is able to spin the prop up quicker. The video doesn't lie - it is what it is.

 

[jbjennings]

Re: True or false a 4stroke has better low end torque

It's like the ghosts in the movie "6th sense"......

I thought the OP wanted to compare 2 stroke and 4 stroke torque. Isn't that what's happening in this goofy test? Why do you want to compare a 2 stroke to 2 stroke now? I don't see how anyone could make the statement that the 4-strokes make more low end torque.
They have to put different pitch props and gear ratios on the 4 strokes just to give them any resemblance to a 2 stroke's low end power.
The 2-stroke has to have more torque---after all, it's a 2-stroke!
Wouldn't the 4-stroke also wear out faster, just like the 4-stroke automotive type engines in a stern drive, since they're always running high rpm's under a high load????? I was thinking that the motors in an inboard/outboard only last a small percentage of hours vs. an engine in a car for that reason. Shouldn't this result in a similar problem with 4-stroke outboards?
JMO,
JBJ