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
Any suggestions





RE: highest reving automobile engine
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
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
RE: highest reving automobile engine
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
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).
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
Stefan Hamminga
EngIT Solutions
CSWP/Mechanical designer
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RE: highest reving automobile engine
Regards
Pat
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RE: highest reving automobile engine
- Steve
RE: highest reving automobile engine
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
RE: highest reving automobile engine
- Steve
RE: highest reving automobile engine
And what about the 1948-on BRM V16 exceding 12,000 rpm?
http:
Bill
RE: highest reving automobile engine
12,000 rpm, but less than a 2" stroke.
Regards
Pat
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RE: highest reving automobile engine
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
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
Regards
Pat
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RE: highest reving automobile engine
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
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
Another is best fuel economy on an automotive engine is ~5-6 m/s.
RE: highest reving automobile engine
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
RE: highest reving automobile engine
MS
RE: highest reving automobile engine
- Steve
RE: highest reving automobile engine
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
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
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
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
here are some experimental results showing the effects of piston speed on piston friction:
http:
RE: highest reving automobile engine
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
I guess you weren`t the only one to notice this.
http://en.wikipedia.org/wiki/Talk:Stroke_ratio
RE: highest reving automobile engine
"Believe only half of what you see and none of what you hear (read?)"---
Rod
RE: highest reving automobile engine
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
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
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RE: highest reving automobile engine
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:
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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
Regards
Pat
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RE: highest reving automobile engine
RE: highest reving automobile engine
- Steve
RE: highest reving automobile engine
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
RE: highest reving automobile engine
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
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:
ht
Have fun with your project.
Terry
RE: highest reving automobile engine
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