Bigger engine but less horsepower, how?

muzorty · L Plate Warrior Joined: 25 Nov 2020 Karma :

Sorry if my question is silly but I want to learn , I also search similar topics but couldnt find answer..

Benelli 752S
754cc
Bore - Stroke: 88mm x 62mm
Torque 67 Nm 6500 rpm
Power: 77 Horsepower 8500 rpm

and

Triumph Street Triple S
660 cc
Bore - Stroke: 76mm x 48.5mm
Torque 66 Nm at 9250 rpm
Power: 95.2 Horsepower 11250 rpm

Benelli 94CC bigger and has bigger bore & stroke , how can be Triumph has more horsepower?

Riejufixing · World Chat Champion Joined: 24 Jun 2018 Karma :

Engine configuration. "Tuning". It's not just cc.

arry · Super Spammer Joined: 03 Jan 2009 Karma :

pepperami · Super Spammer Joined: 17 Jan 2010 Karma :

Power is equal to how much air/fuel mix you engine can suck in and burn efficiently.
Length of stroke, size and weight of piston, size and shape of your squish area, size of valves, duration of valve opening, number of revs, type of fueling system, cam profile, timing, and a host of other variables can and will affect power.

Lots of revs is usually the way the Orientals increase power??? Sort of???
Compression will affect power outputs.
Forced compression of incoming fuel/air mix will affect power outputs.

I’m sure someone will be along soon and tell how they know EVERYTHING about tuning and how everybody else is talking sh*t.
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wr6133 · World Chat Champion Joined: 31 Dec 2013 Karma :

Triumph has an extra cylinder, it can spin up higher than the twin (look at the RPM the peak figures are made at). That is one way to make more power.

Polarbear · Super Spammer Joined: 24 Feb 2007 Karma :

I don't remember my striple revving up to 11000+ revs. I'm sure it redlined about 9500.

Can any present striple owner confirm revs?
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wr6133 · World Chat Champion Joined: 31 Dec 2013 Karma :

arry · Super Spammer Joined: 03 Jan 2009 Karma :

chickenstrip · Super Spammer Joined: 06 Dec 2013 Karma :

But generally, you're making peak power some way below the redline?
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xX-Alex-Xx · World Chat Champion Joined: 12 Sep 2019 Karma :

Bigger engine doesn't equal more power. Just ask any American car manufacturer how they manage to get so little power from such large engines.....
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Ste · Not Work Safe Joined: 01 Sep 2002 Karma :

Google says 11,250rpm.

https://www.motorcyclenews.com/bike-reviews/triumph/street-triple-s/2020/

wr6133 · World Chat Champion Joined: 31 Dec 2013 Karma :

chickenstrip · Super Spammer Joined: 06 Dec 2013 Karma :

wr6133 · World Chat Champion Joined: 31 Dec 2013 Karma :

chickenstrip · Super Spammer Joined: 06 Dec 2013 Karma :

Easy-X · Super Spammer Joined: 08 Mar 2019 Karma :

Translation of original post:

Why doesn't chalk taste like cheese? Laughing

But even from the posted specs the Triumph has 2750 more rpms so obvious innit Smile

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Ste · Not Work Safe Joined: 01 Sep 2002 Karma :

MCN · Super Spammer Joined: 22 Jul 2015 Karma :

Both examples the rpm is where the Oomph is got.

More distance in less time.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

kolu · Nova Slayer Joined: 29 Sep 2019 Karma :

muzorty · L Plate Warrior Joined: 25 Nov 2020 Karma :

So, if you can get better performance with smaller and lighter engine, (Benelli is 45KG heavier and for sure some of it because of its engine),
what is the point to make it bigger?

I mean there must be reason or advantage of it , right?
In that example, what is advantage of Benelli ? more economic or what else?

Or what is disadvantage of Triumph?

Riejufixing · World Chat Champion Joined: 24 Jun 2018 Karma :

Ah but yes but no but. It's complicated. It's not RPM per se.

Here's a nice little graph concerning the street triple and power. You will note that power is not actually directly related to RPM.

Edit: That's for a different capacity machine, but you get the general idea.

It's complicated. Really quite complicated.

Pete. · Super Spammer Joined: 22 Aug 2006 Karma :

Riejufixing · World Chat Champion Joined: 24 Jun 2018 Karma :

Polarbear · Super Spammer Joined: 24 Feb 2007 Karma :

ThunderGuts · World Chat Champion Joined: 13 Nov 2018 Karma :

Other thing to consider is the power curve and what it means for flexibility. If you look at a dyno plot the shape of the curve is far more important than just the peak power. A very peaky engine (eg race tuned 2 stroke) will have a very steep curve on the plot; this means the power isn’t particularly accessible and requires the rider to keep the engine on the boil all the time. An engine delivering greater power across the curve will mean when you change gear you’ve got more power straight away rather than having to climb back up again. Effectively average power over the rev range of the gears I guess.

Possibly less applicable on bikes perhaps because they’re naturally aspirated but I’ve owned turbo cars where the map is set to deliver a fairly modest power output but it is within 90% of the peak power across 80% of the rev range. Far more accessible than a peaky power delivery with a bigger number where you’re forever chasing the sweet spot.
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