The 20 - 80 usable RPM rule

[Flyingpony]

So just what is the safe usable RPM range of an engine, this has always puzzled me. Some people say it's safe to go up to the red-line, but personally, the red-line is something I'd like to err on the side of caution and stay away from.

With that in mind, it turns out that keeping the engine between the 20-80% of the full rev range is best for the engine. Straying below the 20% mark can cause the engine to lug and struggle {note: higher gears will require higher percentages} while exceeding the 80% mark is placing it near the red-line zone and expensive damage zone.

Monitored my own riding habit recently, it turns out that when commuting it stays within the percentage band range 35-50%, and when out on the motorway 55-75% percentage range.

Obviously there are exceptions to this rule. Personally the 80% is one that I don't intentionally break but the 20% rule I will when stuck in traffic at snails pace in first or second gear, provided she's not stressed.

So what do you all think about the 20-80% theory?

[jonbuoy]

Depends I the type of engine I guess. No sense in flogging a VTWIN to the red line, in line fours love a good thrashing.

[Swoop]

I think V-Fours like a bit of welly from time to time as well...:whistle: :whistle: :whistle:

[Nutter34]

The red-line is the manufacturers safe thrash limit. When they design engines, they run them to destruction and then add a percentage for reliability and longevity, which is where the red-line comes into play. You'll find that often the last thousand rpm is over-run anyway on most engines, they stop making power by then.... Have a look at most dyno graphs....
Then, most engines have limiters too, so if you do exceed the red-line, it'll cut the engine....
I agree riding lower revs may not be beneficial but thrash it like you stole it....

And when it comes to two-strokes, their power is determined by porting and pipes and a few other things. They operate best within a certain rpm set by the above mentioned parameters. If you change too early, you are actually riding the bike inefficiently and loading the engine more than it would be if you kept it in the power bands...
I suppose that theory applies to fours as well, coming on the cam it was called, I think...

[onearmedbandit]

With rev limiters on most modern bikes the chances of doing damage via high revs is pretty low, unless you drop it down too many gears. On the road I hardly ever see red-line (1st gear is enough to lose your license) but on the track I'll hit it often, even bounced off the limiter once or twice.

[Pwalo]

Horses for courses old chum. Depends on the layout of your motor.

Traditionally singles and twins tend to have a lower rev ceiling than triples and fours. It's all to do with piston speeds, piston stroke vs bore,reciprocating masses, and a few other factors. There are quite a few articles available which outline the different characteristics of differing engine configurations.

A four will always be able to be revved higher than a single or twin of the corresponding engine size, and needs to to produce it's power.

For a single or twin I reckon 40-80 rule sounds pretty reasonable, but with a four you're probably be looking at 60-90. Nothing worse than labouring an engine.

Running your FXR at it's redline probably isn't too flash an idea.

[bungbung]

That will depend on the specific motor and usage. It is pointless running up to redline on some applications. For the FXR you'll need to look at a dyno chart.

Bearing in mind that a) you'll need all of the power from a fxr b) you won't be running at full revs a high percentage of the time, so I wouldn't be so concerned about blowing it up.

Its a sympathy thing, some motors don't sound happy at the upper end of their range. I had a zxr250 that I felt bad about revving past 14k.

[Edbear]

The 20-80% guide is generally a good one for longevity, but my old girl, (bike not wife...), doesn't mind the odd thrashing at all, in fact I find I have to keep an eye on the revs as she just goes hard to the redline and doesn't seem to die away...

It certainly gets more urgency once it gets to 7k and from 9k it's pulling like a...a... shall we say proverbial...? Redline is 12k on mine.

Most posts here are pretty on the money. Some motors are more fragile than others, the air-oil cooled GSX's are almost indestructible. A modern bike is designed to rev and I haven't heard of anyone blowing one up lately, even racing them.

[inlinefour]

The redline is a fun place to be, however it requires a rebuild before the engine dies draMatically. As for the modern sport dunno, I'm usually holding on and watching where I'm going to have any idea A. what revs the motor is dong or B. what speed I'm doing. The DRZ does not have a rev counter, but I think Ive ridden it through the redline a couple of times, happens when you try to keep up with sportsbikes. Have a mx bike that I'm sure is at its best up by the redline. Remember, powerband can make you horney, does it for me, long time...

[kickingzebra]

I've not heard of an FXR blowing its lolly yet. They are pretty basic engine, and pretty bullet proof.
Hence, if it ain't on the redline, you aren't riding it hard enough!!
Mine copped a fair thrashing from just before the end of the run in period, till 30,000 kms later, when it had a run in of a different sort, and I damn near swear it was going better the older it got, and the harder I rode it. Provided services are kept up, and oil is nice and fresh, I doubt redlining it will damage it.

[bobsmith]

Hmmm strange... when I had my fxr... I almost never went below 5000rpm... (so that would be 45%)???

I figure with a small engine like that right up to the red line shouldn't do any damage... besides on open road you're crusing about 9-10k rpm anyway...

[Sketchy_Racer]

I've not heard of an FXR blowing its lolly yet. They are pretty basic engine, and pretty bullet proof.
Hence, if it ain't on the redline, you aren't riding it hard enough!!
Mine copped a fair thrashing from just before the end of the run in period, till 30,000 kms later, when it had a run in of a different sort, and I damn near swear it was going better the older it got, and the harder I rode it. Provided services are kept up, and oil is nice and fresh, I doubt redlining it will damage it.


Haha you think you thrashed you FXR....

My FXR has lived half its life on the rev limiter.....

Has been cart wheeled twice.

Lowsided so many times i cnat remember

Has had one oil change in its life. and the old was replaced with second hand oil.

And it still damn goes and stil goes damn hard for a 150 fourstroke!!

[Ixion]

I prefer the older rule, double 30/70. Keep both rpm and throttle bertwen one and two thirds.

The one third minimum throttle obviously must be bypassed in traffic. But running on a very small throyttle opening is not only inefficient it can be bad for an engine, especially a two smoker.

[Lou Girardin]

The manufacturers give you a redline and a warranty. They're not expecting them to go pop within those limits.
Then you've got proddie race bikes that live at the redline or more for extended periods and still live.

[Ixion]

Well, yes. But some of us do rather want the bike to last rather longer than the warranty. A LOT longer in fact.

EDIT: BTW did I ever tell you about my grandfather's axe?

[imdying]

EDIT: BTW did I ever tell you about my grandfather's axe?Was it too large for a shelf, and spent many years on the floor? Oh wait...



I've a friend with a 1.5L 84 Nissan Sunny. In the 10 years I've known him, he has mercilessly thrashed that thing way way past the red line, from cold, in the most hideous display of mechanical abuse you've ever seen... 180,000kms, still trucking :D

[CM2005]

Hah, speaking of thrashing...
I got an AG175 for $20 last year with no clutch. Spent more on gas than i did on the bike and, with only 4 gears remaining in the box, i out ran an '86 KX125!!:first: Lucky she didnt nip up on me, it didnt have a clutch!!:rockon:

[Edbear]

Was it too large for a shelf, and spent many years on the floor? Oh wait...:D



You're showing your age again...:yes:

[unhingedlizard]

My 2 smoker doesnt make any power unless your bouncing it off the redline.
Maybe thats why it goes bang so often.......

[myvice]

When they go NANANANANANANANA change gear!

[Madness]

I tend to think of my Tachometer as a Fun-O-Meter. Don't worry about it, just thrash the crap out of it occasionally & enjoy!

[Flyingpony]

EDIT: BTW did I ever tell you about my grandfather's axe?
Was it too large for a shelf, and spent many years on the floor? Oh wait...
Doesn't get it :scratch:

[McJim]

EDIT: BTW did I ever tell you about my grandfather's axe?

do you mean the one he got from his grandfather that was handed down by the grandfather before that? The handle was changed many times (coz sometimes they split or wear out) the head has been changed more than once coz they get smaller when they get sharpened - but the axe has been going for a hundred years and still has great balance and a perfect edge......or are we talking about another axe?

I have no axe to grind...if you axe for my opinion I'll gladly give it...

[Motu]

I rode my 1971 XS1 at 4,000 to 5,000rpm,that's all - change up at 5.000,down at 4,000rpm.Of course it would rev higher,but came at the price of vibration and a lot of hard work handling wise.5,000rpm was good for 70mph,which is about as fast as I go on any bike,I've just never been a speed freak...all the corners I do are lower than that speed.But I maintained a pace at those revs,coming out of every corner hard and on the pegs,cruising on the straights,waiting for the next set of corners to demolish.There are a few who will understand it....but not many.....

[Flyingpony]

Then, most engines have limiters too, so if you do exceed the red-line, it'll cut the engine....
I agree riding lower revs may not be beneficial but thrash it like you stole it....
Over 10k there's no power surge so I find it pointless to use those last few thousand rpm. Biggest surge is between 8k & 9.5k. Don't know if this bike has a rev limiter, maybe someone who's hit it can post where it kicks in.


(1st gear is enough to lose your license)
My bike can get over-taken by a cyclist in 1st gear :nya:
Think license is safe.
While commuting I've ridden behind a Mini couple times, can easily sync the FXR gear changes to the Mini's.


I've not heard of an FXR blowing its lolly yet. They are pretty basic engine, and pretty bullet proof.
Ditto: I've only heard of FXR's expiring due to crashes. Their engines are simple compared to many car engines and their VVT.

Wonder what the highest km a FXR has done is?


The manufacturers give you a redline and a warranty. They're not expecting them to go pop within those limits.
Still got the redline but warranty expired years ago. 12 months is a bit short, even though it was an unlimited km one, but I did use it three times and have been trouble free since it expired.


Well, yes. But some of us do rather want the bike to last rather longer than the warranty. A LOT longer in fact.
Definitely.

[cowpoos]

this sounds like a load of crock....how is reving the shit outta a engine gunna kill it faster than pissing around on it and pretending it will run for ever....I'ld be more worried about it falling to pieces before the engine dies....your not going to own it for ever are you?
and besides if you are....your engine will start to die faster with age....metal fatiges over time....

[JeremyW]

and besides if you are....your engine will start to die faster with age....metal fatiges over time....

Yes but metal fatige is predomainantly due to stress, generated by temperature and forces :)

But I do wholeheartedly agree, ride it like you stole it because bike engines are made to do that and will generally throw a fit and shit themselves when they feel the need to do so.... irrelevant of how they have been treated.... kinda like females when you think if it....

[Pathos]

I have only redlined the fxr once, doing ...fast.. down the bombay hills in sixth.

there just isn't any push over 11.5 thousand rpm.

I keep an eye on the oil, it seems to go through a bit for me ... 3L in the last year with +6k on the clock? I ride it reasonably hard all the time. Is that far too much ?

[bobsmith]

strange I never lost any oil on my fxr... I think I did about 5000km on it... have you checked your washer and sump nut?

[Flyingpony]

I keep an eye on the oil, it seems to go through a bit for me ... 3L in the last year with +6k on the clock? I ride it reasonably hard all the time. Is that far too much ?
Strange, mine doesn't burn or leak any oil.

Considering they only hold about 1.3litres, misplacing 3l in 12 months makes me wonder if yours is leaking somewhere, or does it blow blue smoke like a 2-stroke bike?

Some places to check for oil leaks:

Sump bolt - maybe loose, washer gone or cracked sump casing
Loose oil filter cap or missing/broken o-ring seal
Problem with oil coolant system - hoses and radiator
Loose oil filler cap or missing/broken o-ring seal
Other: i.e. front sprocket gearbox seal

Given the volume of oil lost, the oil leak should be easy to find because the engine will be tremendously dirty there.

[imdying]

I beat the absolute crap out of an FXR, red lined it in every gear all day every day, never managed to kill it though.

[Dodger]

I have a 50cc scooter here with a Tachometer, why?! The thing wont do 60kph without it sitting at the high end of the redline.
I think it's more for show :scooter:

[thehollowmen]

I thought "whoa I must be labouring the engine" because of shuddering, but I worked it out by riding today. I'm doing about 40-80% because of a factory installed flat spot between 3-4k RPM for emissions.

I'd like to go lower, then I'd gear it up, better sort out that flat spot then.