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highest reving automobile engine

highest reving automobile engine

highest reving automobile engine

(OP)
I'm trying to develope a new head design that wont have any rpm limit.  I would like to use an existing long block to lower costs but I'm not sure which would be best. I'm leaning towards a four cylinder HONDA because parts are cheap and available.  This would become the prototype engine with a lot of custom work so any engine would actually be fine as long as the long block could survive 10k+ rpm.  

Any suggestions    

RE: highest reving automobile engine

Try to use a very short stroke so piston speed does not become the limit.

There is no such thing as no limit. There are already several designs where the ports are the size of the bore.

Regards
Pat
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RE: highest reving automobile engine

the first thing that will limit your engine rpm is the phenomena called valve float. Inertia of the relatively heavier intake valves is likely to make it difficult for the valve to return to the seat at high rpm.

If you see blue smoke coming out of F1 cars, that's probably due to the intake valve hitting the piston and broke into pieces.

I've worked on racing engines before, we normally used less aggrasive valve lift for the first few races just to make sure that we move cautiously to define the limit.  

RE: highest reving automobile engine

the Honda s2000 (with taps in the background) had a 9000 rpm limit: 2,157 cc (132 cu in) F22C1 I4 Since this engine is alonger stroke version of the 1,997 cc (122 cu in) F20C I4, I'd look at putting the crank from the F20C in a F22C and use the correct set of piston and rods along with the s22 head.

RE: highest reving automobile engine

there were some ferrari engines which (according to video games I've played) could rev to 14000rpm or higher without grenading.  

Perhaps what you should do is set up the engine so that the performance at higher rpm is miserable enough as to prevent further increases in engine speed.  In other words, for an unloaded engine, make sure that power output at 14000rpm (or whatever) is zero.  For a loaded engine you could probably do with a torque curve that falls off steeply above 50% of max allowable rpm.

a detail to bear in mind is that sometimes the fastest an engine turns is when it is being turned by something else (like by the transmission, when going down a hill).

 

RE: highest reving automobile engine

Ten thousand rpm might have been impressive in 1960 !!!
Definitely not in today's automotive circles.
With NASCAR 358 cu.in. engines running in the mid 9000's for 500 miles and more with no problems...with F-1 engines limited to <20,000 (they would certainly be over that if it were allowed)---I watched a dyno test on a small four stroke Honda motorcycle engine at the R&D facility in Gardena back in the 70's that turned 22,000+.  I have ridden several motorcycles that revved to well over 10,000.
Our ancient little 'A' series BMC 1380cc engine revs to 9500 and our vintage Lotus twincam is safe to over 10,000 (although we do not rev it that high).

Quote:

I'm trying to develope a new head design that wont have any rpm limit.

Sorry, that just does not exist. There will always be some limiting factor, be it mechanical or flow related.

Rod

 

RE: highest reving automobile engine

Go for the gas turbine! Or tell us some of your other restraints (like desired power, usage, lifespan, package size, budget)

Stefan Hamminga
EngIT Solutions
CSWP/Mechanical designer
Searching Eng-Tips forums

RE: highest reving automobile engine

If you want revs, check out any of the 4-cyl 4-stroke 250's that the Japanese makers produced (cbr/gsx-r/zxr/fzr/abc/lmnop).  I will never forget seeing a red line at 19000 on one of them some years ago.

- Steve

RE: highest reving automobile engine

... and don't forget the Ducati motorcycle engines that use cams to both open AND close the valves (desmodromic valve actuation).

But, as others have noted, there's still an RPM limit ... Spin ANYTHING fast enough, and something's eventually gonna go boom.

RE: highest reving automobile engine

I too have thought about building a high revving IC Engine. Desire + no time = no engine. There is so many things to consider as I've read above. Critical load limits on the reciprocating package, induction, exhaust, the perfect port design, valve control.. etc etc. My interest has been to reverse engineer a high revving motorcycle engine and plug all the data into maybe Engine Expert or Dynomation or both and go from there.

RE: highest reving automobile engine

I am sure I saw a V4 50cc (Honda??) engine at Sammy Miller's museum a few years ago.  Anyone got any info?  I bet it was a high revver.

- Steve

RE: highest reving automobile engine

Vrooooom vrooom......

Still a feat in 1948. They must have used a lot of the materials technology from WW2 lessons.

Bill

RE: highest reving automobile engine


SomptinGuy, way back when 50cc bikes were raced for World Champs, Honda had a twin cyl, 4 valves per, which had peak power at 21,000rpm. IIRC, it also had 12 gears. Saw one at Mallory Park and it sounded like an angry wasp!

Ridden by very small Japanese racers.

Harry

www.tynevalleyplastics.co.uk

RE: highest reving automobile engine

Yep, Harry. That's the one I saw at the Honda R&D facility.  Noisy little bugger, too.

Didn't BRM or some F-1 team do some experiments with an H-32?  Seems like I read something a long time ago.

Yes 12k was quite a fete in '48...So was my drive in a Honda S 600 in the 60's...Buzzing around Forrest Lawn at two AM shifting at ~10,000---fun, fun, fun.  Especially coming from a Vette owner (at the time).

Rod

RE: highest reving automobile engine

"I seem to remember a BRM H32. I think it never made it to a race."

There was a 3litre H16, effectively two flat 8s stacked on top of each other. I can't recall if it ever raced.

The BRM 1.5litre V16 makes an utterly astonishing sound, there are some recordings of it floating around on the net. It's well worth having a listen to this engine, but to really get the full sonic impact copy to a CD and play loud on a big stereo (be warned, tape down the hairs on the back of your neck...).  

RE: highest reving automobile engine

Hello 86corolla,

While valve train dynamics may dictate engine speed capability, mean piston speed is also a factor.  I use two seat-of-the-pants limits:  10 meters per second mean piston speed for constant speed service (such as aircraft piston engines) and 25 meters per second for engines that hit peak rpm for very short durations (such as many motorsport applications).  Thus a 100 mm stroke engine should be limited to about 3000 rpm for continuous speed service and maybe about 7500 rpm for highly variable speed service.

RE: highest reving automobile engine

Good rule of thumb, the industrial engines I work with run ~8.5-8.7 m/s continuously for ~4 years without a bottom-end overhaul.

Another is best fuel economy on an automotive engine is ~5-6 m/s.

RE: highest reving automobile engine

"Another is best fuel economy on an automotive engine is ~5-6 m/s."

I have never heard of any function that relates piston speed to best fuel economy!?! How on earth does that work then?

MS

RE: highest reving automobile engine

it puts you in the speed range of 1500-2200 rpm for nearly all car/light truck engines.  
 

RE: highest reving automobile engine

And how does this have any bearing on fuel economy???

MS

RE: highest reving automobile engine

How does mean piston speed affect economy?  By what mechanism?

- Steve

RE: highest reving automobile engine

um, last I checked the BSFC curve for engines varies with rpm, and cars tend to get better fuel economy in about that rpm range.  

regarding direct effects of piston speed vs economy, you do have lower friction losses at lower piston speeds (to a point).

Search for "gear fast run slow" for more info.
Example result: A truck spec'ed for optimum fuel economy will typically be geared to run at a very low engine rpm while at cruise speed, the so-called "Gear Fast Run Slow" concept.
 

RE: highest reving automobile engine

"um, last I checked the BSFC curve for engines varies with rpm"

Come on Mike, I'm sure there is no requirement for sarcasm?

"and cars tend to get better fuel economy in about that rpm range"

A truly nebulous statement if ever I heard one!


That is quite possibly the biggest piece of generalisation I have ever come across - but I guess it was put forwards as a 'rule of thumb'.

MS

RE: highest reving automobile engine

Sorry, your questions came across as being either very naive or "bait," either of which justify sarcasm in my book.  Go ahead, launch your flame war now.
  
I'm pretty sure that I've even seen an old engine design reference with a plot of BSFC vs mean piston speed for a large sampling of engines.  

Steve, I think that such a graph may be available from a designosaur at your company.

 

RE: highest reving automobile engine

I'm used to Isaac's sarcasm

My question was unrelated to rpm.  I was wondering if there was a DIRECT effect of piston speed on economy (a cause) or whether it was indirect (a correlation).  If it's purely down to friction, why is there an optimum?

Obviously there are sweet spots on BSFC maps that tend to be in a certain common rpm range.  But take a massively over-square engine.  Does its BSFC sweet spot move because the rpm/piston speed ratio changes or for other reasons?

- Steve

RE: highest reving automobile engine

FMEP correlates strongly to rpm, which correlates strongly to piston speed (for obvious reasons).  The combustion side of the efficiency gets worse below a certain point.

here are some experimental results showing the effects of piston speed on piston friction:
http://me.engin.umich.edu/autolab/Publications/Adobe/P2005_09.PDF

 

RE: highest reving automobile engine

I just had a browse through what wikipedia has to say about stroke ratios:

http://en.wikipedia.org/wiki/Oversquare

It was when I read the old chestnut: "...torque tends to be lower since torque is relative to crank throw..." that I decided to look elsewhere.
 

- Steve

RE: highest reving automobile engine

Goes back to my old tag line, paraphrased....

"Believe only half of what you see and none of what you hear (read?)"---winky smile

Rod

RE: highest reving automobile engine

It's obviously a rough estimate that won't hold true for every automotive engine but that's why it's a rule of thumb.  I think it's more of an empirical observation than anything and 5-6 m/s is 5.5 m/s +/- 10%.  

Obviously, lower piston speeds means less friction but at some point you start to lose efficiency due to the amount of time available to transfer useful heat out of the combustion gases and into the cylinder, head and piston where it's wasted.

RE: highest reving automobile engine

I have trouble with the amount of time argument.

If you do 1000 rpm for 1 minute or 6000 rpm for one minute you still spend 1/4 min on the power stroke, you just have 6 times as many events for 1/6th the time each.

Obviously higher speeds lose more to inertia in the reciprocating parts.

Rate of heat build up vs piston speed reduces the useful work that can be extracted as speed increases.

Rate of burn increases as turbulence increases from quench effect as rpm increases.

Higher rpm allows the same power from a smaller engine which weighs less and may fit in a lighter more aerodynamic chassis.  
 

Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
 

RE: highest reving automobile engine

regardless of the reason for it, it is apparent from a BSFC plot that there is a minimum value which occurs well above idle rpm, and well below maximum rpm.  Friction continues to drop as speed is reduced from the peak BSFC point, so that's not the reason for the increase in fuel consumption.  

here's a bit of engineering course material from GA Tech which suggests that heat lost to the cylinder wall drops with increased engine speed:
http://www.me.gatech.edu/energy/ICEngines/11_HeatTransfer.pdf

I expect that Steve (Somptingguy) could get us a very authoritative answer from another member of his organization...  but it might take more effort than it's worth.  

Anyway, someone who's familiar with Woschni's heat transfer work might be able to shed some light on this.  Not me!
 

RE: highest reving automobile engine

lmao.
 

RE: highest reving automobile engine

Very good.  I wonder if implied person reads here?

- Steve

RE: highest reving automobile engine

Hmm, time for some handwaving...

High stoke ratio (for same displacement and rpm) means:

- Lower side loads (more acute rod angle) - less friction
- Higher contact area (bigger piston) - more friction
- Shorter stroke (Integral of force*displacement lower) - less friction

So I've argued myself round in circles.  Unfortunately I don't have access to the Chen Flynn paper at home and I'm not in work 'till Monday.

- Steve

RE: highest reving automobile engine

Use an electric motor, it will be easier, and less emissions.

RE: highest reving automobile engine

Convert a 4 stroke to a 2 stroke that way you have more firings for a given number of revs.  A super charger/ turbo charger set up will be needed since you probably don't want to do all the work to make it a crankcase charged setup.
Just an idea!!  Check out the old big 2 stroke diesel trucks using the 6-71 I love the sound of those big straight 6 2 stroke diesels, especially when run on straight pipes!! Of course they aren't high revving but just an example of what could be done.
Then of course for high revs on a oem available motor would be a Wankel. There's is no other feeling then bringing that puppy up to 7 grand without fear of grenading.  With a bit of work you could probably make it go higher, It all depends on the dependability factor you are looking for.
 

RE: highest reving automobile engine

86corolla,

The killer with recip piston engines are the inertia loads in the piston/conrod assembly due to the acceleration/deceleration experienced during each piston stroke, and the inertia loads and vibratory dynamics experienced in the sprung poppet valve and cam system of the valvetrain.  These inertia loads, due to the kinematic linear accelerations of the system's mechanism, can be minimized by limiting the linear travel of the piston or valve.  That is how recent F1 racing engines could achieve crank speeds in excess of 20,000 RPM.  They used very short piston strokes and very low valve lifts with pneumatic closing springs.

The Honda NR500 race engine ran to 20,000 rpm and the Honda NR750 production motorcycle engine ran to 14,000 rpm:

http://upload.wikimedia.org/wikipedia/commons/thumb/1/18/Ovalpiston.jpg/800px-Ovalpiston.jpg

Have fun with your project.
Terry

RE: highest reving automobile engine

Hey 86corolla,

I am a little curious as to why you feel the cylinder head is the limiting factor for the RPM potential of a IC engine?  What sustainable RPM range are you looking for?  I notice that your original post was dated 02/14.  Since it is now close to the end of March, have you not found anything interesting enough to warrant a response?  Have you not found anything interesting enough to comment on or have you lost interest in your project?

Larry

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