Quote from: ribbert on February 14, 2020, 08:35:05 PM
I think you'll find piston speed is the limiting revs factor for a road going FJ engine.
Noel
Here are the specific questions asked of you Noel following your post above.
Randy - RPM
Quote from: racerrad8 on February 15, 2020, 12:31:57 PM
Quote from: Pat Conlon on February 15, 2020, 11:44:45 AM
Yep, I was wondering about that....Questions for Noel:
1) FJ Piston speed: How fast is too fast?
2) If the stroke is 63.8mm at 11k rpm the FJ piston speed is 4605 FPM, is that too fast? Why?
I'm open to learning....
I'll add a couple more questions for Noel:
3) Why is piston speed the limiting factor of a FJ engine?
4) Have you ever observed a FJ engine failure due to excessive piston speed?
a) If yes, what failed due to the excessive piston speed?
5) Valve "bounce" versus valve "float"; which comes first?
6) Why does one come before the other?
I too am churning for learning...
Randy - RPM
I've looked through my reference books and I can't find it, but I seem to recall reading somewhere long ago that an average piston speed of 5000 ft/min should be considered as an upper "practical" limit for a piston engine. The reason escapes me, but I think it had something to do with ring flutter, cylinder wall lubrication failure and other such dastardly events. Obviously, highly-tuned racing engines (which our FJ motors certainly qualify) could be run at higher speeds, but this 5000 ft number was more of a practical design guide, rather than an absolute limit.
I thought for sure that it would be in my copy of "The Design and Tuning of Competition Engines by Philip H. Smith, but I haven't found it yet. Maybe it's in one of my WW2 piston aircraft engine design books. I'll keep looking...
Bill
Kevin Cameron is my favorite technical writer and in this article he mentions 4000-4500 FPM as a traditional limit..
https://www.cycleworld.com/2016/01/25/plight-of-the-modern-motorcycle-piston-kevin-cameron-insights/ (https://www.cycleworld.com/2016/01/25/plight-of-the-modern-motorcycle-piston-kevin-cameron-insights/)
Good article.
Joe
FYI - with the stock 63.75mm stroke - here are the piston speeds at different RPMs (these are average speeds - max speeds will be more, but during mid stroke - not at the critical top of the stroke):
9500 RPM ~ 3,974 fpm
10,500 RPM ~ 4,392 fpm
11,000 RPM ~ 4,601 fpm
That's said, very few FJ/XJR motors have the mods needed to make any useful power at those higher RPMs ....
Chris, on a stock FJ engine, do you think my guess correct, that valve float would be the first power limiter?
I see 3 frontrunners
1) Valve float (loft) or
2) Poor Volumetric Efficiency (head flow limitations) or
3) Durability (piston or rod failure)
I'm curious about the rpm that peak horsepower occurs at?
Joe
How much is a bag of groceries? Depends on what's inside....
For our stock bikes the magazine folks already measured for us..
84/85 https://www.motorcyclespecs.co.za/model/yamaha/yamaha_fj1100%2084.htm (https://www.motorcyclespecs.co.za/model/yamaha/yamaha_fj1100%2084.htm)
86 https://www.motorcyclespecs.co.za/model/yamaha/yamaha_fj1200%20%2086.htm (https://www.motorcyclespecs.co.za/model/yamaha/yamaha_fj1200%20%2086.htm)
87 https://www.motorcyclespecs.co.za/model/yamaha/yamaha_fj1200%20%2087.htm (https://www.motorcyclespecs.co.za/model/yamaha/yamaha_fj1200%20%2087.htm)
89/90 https://www.motorcyclespecs.co.za/model/yamaha/yamaha_fj1200%20%2089.htm (https://www.motorcyclespecs.co.za/model/yamaha/yamaha_fj1200%20%2089.htm)
91/93 https://www.motorcyclespecs.co.za/model/yamaha/yamaha_fj1200%2091.htm (https://www.motorcyclespecs.co.za/model/yamaha/yamaha_fj1200%2091.htm)
Pat, would it be possible to comb through the site and cherry pick the dunk sheets that have been posted along with the mods? Would be a good one-stop thread for general info. Unfortunately not a lot of before and after sheets that I recall, and each dyno on any day will read a bit different, but things like peak power or peak torque rpms, etc would be good info
Quote from: Pat Conlon on March 02, 2020, 12:27:30 PM
How much is a bag of groceries? Depends on what's inside....
For our stock bikes the magazine folks already measured for us..
84/85 https://www.motorcyclespecs.co.za/model/yamaha/yamaha_fj1100%2084.htm (https://www.motorcyclespecs.co.za/model/yamaha/yamaha_fj1100%2084.htm)
86 https://www.motorcyclespecs.co.za/model/yamaha/yamaha_fj1200%20%2086.htm (https://www.motorcyclespecs.co.za/model/yamaha/yamaha_fj1200%20%2086.htm)
87 https://www.motorcyclespecs.co.za/model/yamaha/yamaha_fj1200%20%2087.htm (https://www.motorcyclespecs.co.za/model/yamaha/yamaha_fj1200%20%2087.htm)
89/90 https://www.motorcyclespecs.co.za/model/yamaha/yamaha_fj1200%20%2089.htm (https://www.motorcyclespecs.co.za/model/yamaha/yamaha_fj1200%20%2089.htm)
91/93 https://www.motorcyclespecs.co.za/model/yamaha/yamaha_fj1200%2091.htm (https://www.motorcyclespecs.co.za/model/yamaha/yamaha_fj1200%2091.htm)
Thank you Patrick. Seems there is little reason to rev a FJ beyond 9k.
Joe
Quote from: Tuned forks on March 02, 2020, 12:59:09 PM
....Seems there is little reason to rev a *stock* FJ beyond 9k *while riding on the street*
FIFY ^^^
I've learned at my age, it's all about bladder control.... :pardon:
^^^^^
Sphincter control too. :biggrin:
Joe
Thanks guys for doing a good amount of work, but the questions are still there for Noel to answer. He is the one who made the statement that the limiting factor of the FJ engine is piston speed.
Quote from: ribbert on February 14, 2020, 08:35:05 PM
I think you'll find piston speed is the limiting revs factor for a road going FJ engine.
Noel
All of this research is just speculation without Noel's basis for his statement and the answers to all of the questions posed to him as follow-up.
Randy - RPM
Welp, by cunningly adding the words "I think..." it qualifies as non declarative sentence ...
Quote from: ribbert on April 26, 2020, 10:31:39 AM
As for the piston speed discussion, as usual, I'm flattered you seek out and value my views on technical matters, however, in this instance I thought it best to share it with just the few people who asked, with a caveat preventing it being re posted.
Noel
I am sorry to inform the FJ forum membership here, that Noel has decided to be selective with his "view on technical matters" (ie opinion) and share with his selected "few".
I guess, the majority of the FJ forum membership will never know why piston speed
"is the limiting revs factor for a road going FJ engine" as Noel so eloquently pointed out at the very beginning of this topic....
A select few know, but they have accepted the secret code of Noel and must take his opinion bestowed upon them to their grave.
Randy - RPM
Quote from: racerrad8 on April 26, 2020, 12:11:00 PM
I am sorry to inform the FJ forum membership here, that Noel has decided to be selective with his "view on technical matters" (ie opinion) and share with his selected "few".
I guess, the majority of the FJ forum membership will never know why piston speed "is the limiting revs factor for a road going FJ engine" as Noel so eloquently pointed out at the very beginning of this topic....
A select few know, but they have accepted the secret code of Noel and must take his opinion bestowed upon them to their grave.
Randy - RPM
Good to see you joining in the spirit of my post. A bit of not taking ourselves too seriously and lightening the mood in these trying times is good for the soul. :good:
Noel
Quote from: ribbert on April 27, 2020, 05:26:32 AM
Quote from: racerrad8 on April 26, 2020, 12:11:00 PM
I am sorry to inform the FJ forum membership here, that Noel has decided to be selective with his "view on technical matters" (ie opinion) and share with his selected "few".
I guess, the majority of the FJ forum membership will never know why piston speed "is the limiting revs factor for a road going FJ engine" as Noel so eloquently pointed out at the very beginning of this topic....
A select few know, but they have accepted the secret code of Noel and must take his opinion bestowed upon them to their grave.
Randy - RPM
Good to see you joining in the spirit of my post. A bit of not taking ourselves too seriously and lightening the mood in these trying times is good for the soul. :good:
Noel
Interesting discussion - before it winds down, how about another angle in regards to the FJ & technical matters.
Noel, you mention how you use your FJ in a robust manner in different situations and apparently on a frequent basis - so although absolute power may be limited (or not) for a particular reason & top speeds of particular models have already been discussed etc.
However based on your experience, what is the maximum SUSTAINED power output of the FJ engine? It appears to be a strong engine by design, but other than a top end run, what can the FJ withstand on a continuous, high speed run. Also, any limitations on how many high speed sustained excursions, again based on your personal experience, can be expected (from a mechanical aspect)?
Hopefully, you can lend your expertise to the masses as enquiring minds would like to know...!
Ride safe,
Midget
What is the maximum continuous power output of an FJ engine? Oooo, what a good question!
Most vehicles do not have cooling systems large enough to deal with continuous full-throttle operation. (Your truck slowly pulling a heavy trailer up a very long hill, for instance.) But let's just say we fill an FJ with the very best synthetic oil made, and we add a bigger oil cooler so that the temperature is kept under control. And we will also assume we are running this bike on one of those huge paved oval tracks that the tire companies use for testing. And it's a cold day so the aluminum engine isn't melting. So the bike is running full-throttle with no let up, continuously, and not overheating. Will the engine stay together? And how long will it stay together? Will the connecting rod bolts go past their endurance limit and break? At what RPM will those rod bolts stay below their endurance limit and therefore last forever?
What a great question... :unknown:
Bill
Quote from: CutterBill on May 07, 2020, 04:08:08 PM
What is the maximum continuous power output of an FJ engine? Oooo, what a good question!
Most vehicles do not have cooling systems large enough to deal with continuous full-throttle operation. (Your truck slowly pulling a heavy trailer up a very long hill, for instance.) But let's just say we fill an FJ with the very best synthetic oil made, and we add a bigger oil cooler so that the temperature is kept under control. And we will also assume we are running this bike on one of those huge paved oval tracks that the tire companies use for testing. And it's a cold day so the aluminum engine isn't melting. So the bike is running full-throttle with no let up, continuously, and not overheating. Will the engine stay together? And how long will it stay together? Will the connecting rod bolts go past their endurance limit and break? At what RPM will those rod bolts stay below their endurance limit and therefore last forever?
What a great question... :unknown:
Bill
I'll bet you'd have catastrophic tire failure from heat before the engine would give up!
Other than putting a FJ engine on a dyno are running it to a point of failure, a close second are the FJ engines in those legend cars. Running WFO lap after lap pushing a 1250 lb. race car is about as stressful as you can get. The sideway mounted engines get so hot they twist, breaking the camshafts.....
At least 25 hours straight confirmed https://www.motorsport.com/roadracing/photos/18-rpm-legends-mark-bailey-randy-raduechel-mike-david-robert-1/131219/ (https://www.motorsport.com/roadracing/photos/18-rpm-legends-mark-bailey-randy-raduechel-mike-david-robert-1/131219/)
Quote from: Mike Ramos on May 07, 2020, 03:12:32 PM
However based on your experience, what is the maximum SUSTAINED power output of the FJ engine? It appears to be a strong engine by design, but other than a top end run, what can the FJ withstand on a continuous, high speed run. Also, any limitations on how many high speed sustained excursions, again based on your personal experience, can be expected (from a mechanical aspect)?
Midget
Mike, I know you're just stirring the pot and having a bit of fun and were not expecting a reply but there are members too new to realise that and Randy's no doubt itchin' for ammo so you have me in a corner. I wouldn't want anyone to think I'm ignoring you.
#1 Question: "what is the maximum SUSTAINED power output of the FJ engine? "The maximum sustained power output is the exactly the same as the minimum sustained power output. Duration does not affect power output, power doesn't continue to build the longer you run it.
#2 Question: "what can the FJ withstand on a continuous, high speed run." The answer depends on your definition of "high speed" - compared to what....a car, a plane, a cyclist, a sloth.......? Speed is relative, and to your definition of "withstand" – what are we talking about here, unkind words, rider flatulence, sneers from Honda riders, one of your critiques.... What?
#3 Question: "Also, any limitations on how many high speed sustained excursions"Well, the the number of excursions, at any speed and of any duration, are limited by factors such as work, weather, family obligations, social engagements, availability......
As for "sustained excursions" how could a singular excursion not be sustained, if it wasn't sustained it would become multiple excursions.
Mike I'm suspicious of your authorship of this, even by your own admission, mechanical aptitude is not your forte but you do pride yourself on your writing and language skills. The clumsy writing above is not up to your standard and on both counts, just plain doesn't sound like you.
Does this (below) sound like someone who'd ask a techy question or be remotely interested in the answer? You have never before displayed any such interest or participated in such discussions.
Quote from: Mike Ramos on September 28, 2016, 02:50:06 PM
However after several mishaps (e.g. I did not realize the airgun was in tighten mode and broke off a couple of case bolts (thank goodness for those EZ-OUT tools!) dropping the cams on the ground and braking a few fins off of the head - I may have stripped a spark plug as well; never use an air tool on the spark plugs!
...... Finally Randy said, "Little man, stay away from the mechanics" and had me take pictures....
Most of all though, even in your most critical posts the one thing we could rely on was that they'd be beautifully written and grammatically correct. In this regard, the above question is not something I can imagine flowing from your pen, not unless Capt Morgan co-authored it in the wee hours.
Good to see you back on the forum Mike, I have missed your regular and unique input as I'm sure many others have.
Noel
Nice post Noel, but the question still remains:
*Why* do you think piston speed is the limiting factor in the power output of a FJ engine?
Quote from: ribbert on May 08, 2020, 09:59:17 AM
...and Randy's no doubt itchin' for ammo so you have me in a corner. I wouldn't want anyone to think I'm ignoring you.
Noel
Mike, you should feel special as Noel actually took the time to respond in the post when you asked a question. Up to this point, he has ignored me and everyone else.
Quote from: Pat Conlon on May 08, 2020, 10:55:55 AM
Nice post Noel, but the question still remains:
*Why* do you think piston speed is the limiting factor in the power output of a FJ engine?
Pat, his post is just deflection from the original statement he posted, pure deflection by asking Mike questions and then telling him is doesn't have the "mechanical aptitude" and then questions if he authored the post.
Now, Noel can determine who wrote the post just by the content. So the next question for Noel, since he is diverting from answering the original question...
Noel, who wrote Mike's post from Mike's account?I doubt he will answer either question about piston speed or who wrote Mike's post.
Maybe Mike's account was hacked by Klav or you, Pat or me or someone else on Noel's blocked PM list...
Maybe Noel's answer will help narrow down the culprit. :diablo:
Randy - RPM
Guys. Really?
This is borderline childish, petty, and somewhat embarrassing.
Agree to disagree or please take it off line.
Yea, no reason to kick the dead horse....
Quote from: FJ_Hooligan on May 08, 2020, 11:20:52 AM
Guys. Really?
This is borderline childish, petty, and somewhat embarrassing.
Agree to disagree or please take it off line.
David,
So far there is nothing to disagree with, Noel hasn't responded to his original stated position. We are just asking for the reason he made the statement he made for all to see.
Now, as far as taking to to PM, that won't work either... We are blocked by Noel.
Quote from: racerrad8 on May 01, 2020, 11:10:42 AM
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Klavdy
Pat Conlon
racerrad8
Mike Ramos
ZOA NOM
copper
As far as embarrassment, you are correct. Myself, Pat, Mike and any anyone else who has responded in the topic for Noel's opinion based on his statement, I am sorry we are not part of Noel's chosen few to be able to learn from his expansive knowledge.
So, effective today I will be locking this topic since there is nothing else to see or learn from Noel's original statement.
Any further comment or statement from Noel regarding piston speed will be deleted.
If you have any questions, concerns or feel this topic should not be locked, please PM me directly.
Now you guys, stop acting childish and embarrassing David. :dash1:
Randy - RPM