Box Stock

reving motor with no load questions

I have noticed that lately several people have really not accepted the answers they get on Bobs and want to argue them to death. Why? is that happening.
 
One Fast Kat said:
I have noticed that lately several people have really not accepted the answers they get on Bobs and want to argue them to death. Why? is that happening.
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if this is in reference to my post i was not arguing, only restated the question in a different form perhaps easier to understand incase there was miscommunication, as i felt my questions were unanswered, myself have a hard time understanding and learning new things but this form definitely is helping to expand my knowledge vastly on these small motors
 
spincycle said:
Not trying to be rude or anything, but you seem to want to spend an overly large amount of time trying to dissect something, that as far as I'm concerned, is completely irrelevant to successful racing...if you're trying to tune your motor, you will gain much needed information by finding a motor shop with a dyno, that way you can Rev up the motor when it does have a load on it, and in many instances, can get a detailed computer printout to find out VIP data like peak torque among other things...😉
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i dont compete in any races, or plan too besides maybe private races between buddys, only wanting to expand my engine building knowledge, in the past when i looked up things this forum popped up alot and provided me tons of info, so often that i finally made an account so i can ask my own specific questions to those who care to share there knowledge,

i like to know exactly why not do things, instead of blindly accepting its not to be done, i like to know the reasoning behind it only for personal curiosity/knowledge, i may have worded the question terribly im not certain lol ive gotten some answers but nothing specifically saying no or yes and why it seems,

what ive gathered is there's no issue with snapin the throttle(not holding to revline or near redline) to a high rev without load compared to load aslong as im not redlining motor there's no difference other than the rpm climbs faster due to no load
i did read something about increased vibrations upon reving with no load that can be harmful but not sure if it applies to these small motors or not as it was a Harley forum

thanks everyone for the info
 
Correct . Did you get an answer your comfortable with .?
It boils down to internal stresses are amplified. Its a machine , failure is eminent .
As they say if it can go wrong: It will go wrong .
Yea vibration can be a issue.
Weather a Harley or a single cylinder engine . personally don't think the vibration is related to load or no load .
 
Load from a clutch and drive train on your bike, or load from a load cell on a dyno, dampens harmonic vibrations, yes.
There have been many discussions on single cylinder balancing on this forum over the years - you might use the search bar and read up on some of those as well. Holding your throttle at 6000 rpm under no load is less stressful than 7000, sure, but it is considerably more stressful on your engine than at idle (1800 rpm.) I don't see the vibration as much of a factor as the acceleration rate of the rotating assembly. Of course, that depends at what rpm you are holding the throttle, what rpm the rotating assembly is balanced to, and how long you hold the throttle open. Redlining with no load is
If you are thinking that you can "tune" your engine but revving and holding the throttle at a particular rpm with no load, you are mistaken. An engine under load will always require more fuel than one under no load. I am fairly certain on this from study and personal experience, but I think that anything above an idle and this will be the case.



-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
www.youtube.com
34 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
MasonIsGreat35 said:
i dont compete in any races, or plan too besides maybe private races between buddys, only wanting to expand my engine building knowledge, in the past when i looked up things this forum popped up alot and provided me tons of info, so often that i finally made an account so i can ask my own specific questions to those who care to share there knowledge,

i like to know exactly why not do things, instead of blindly accepting its not to be done, i like to know the reasoning behind it only for personal curiosity/knowledge, i may have worded the question terribly im not certain lol ive gotten some answers but nothing specifically saying no or yes and why it seems,

what ive gathered is there's no issue with snapin the throttle(not holding to revline or near redline) to a high rev without load compared to load aslong as im not redlining motor there's no difference other than the rpm climbs faster due to no load
i did read something about increased vibrations upon reving with no load that can be harmful but not sure if it applies to these small motors or not as it was a Harley forum

thanks everyone for the info
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The other problem no one has mentioned is ring real. Without a load, there is little to no cylinder pressure to push the rings against the cylinder walls. Free revving without a load can wear the rings and cylinder walls, causing it to lose ring seal and power.

As Brian has said, an engine with a load will require more fuel to make power. At idle and low speed, fuel can wash down the cylinder, leaving little to no oil on the walls. Without oil the rings don't seal and you'll increase blow-by. Fuel then contaminants your oil, which is bad, and oil can blow by the rings into the combustion chamber also bad. These engines also have a low rod ratio of around 1.5, so you have a fair amount of side load on the piston skirts. If you lose oil on cylinder walls, it will cause the skirts to wear prematurely.

I think what everyone has tried to communicate is the stress the engine is under, but it is sometimes difficult to visualize that stress. At 7000rpms, the engine is rotating 116.5 times a second, and the piston is moving around 42ft/s while changing direction each cycle. The engine has to rev up but also come down how long does it take for the engine to come back to idle?

All of the reasons given should tell you not to free-rev your engine. If you are pursuing more knowledge on the subject it can be answered more in-depth by studying engine building and tuning principles in general. You'll find more reasons why it hurts your engine.
 
CarlsonMotorsports said:
Load from a clutch and drive train on your bike, or load from a load cell on a dyno, dampens harmonic vibrations, yes.
There have been many discussions on single cylinder balancing on this forum over the years - you might use the search bar and read up on some of those as well. Holding your throttle at 6000 rpm under no load is less stressful than 7000, sure, but it is considerably more stressful on your engine than at idle (1800 rpm.) I don't see the vibration as much of a factor as the acceleration rate of the rotating assembly. Of course, that depends at what rpm you are holding the throttle, what rpm the rotating assembly is balanced to, and how long you hold the throttle open. Redlining with no load is
If you are thinking that you can "tune" your engine but revving and holding the throttle at a particular rpm with no load, you are mistaken. An engine under load will always require more fuel than one under no load. I am fairly certain on this from study and personal experience, but I think that anything above an idle and this will be the case.



-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
www.youtube.com
34 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
Click to expand...
this is the information i was asking for, specifics on why it is harmful and what happens, no i do not think i can tune the bike that way just wondering what the differences in reving without load compared to load are, and why it is said not to rev without load for long periods, as i never thought about it before and decided to seek information about it, im new to building motors and slowly trying to learn as much as i can,

originally my question was about giving the throttle a snap without load not holding the throttle at a certain rpm, as i read free reving can blow ur motor, i assumed free reving was jus few revs without load, not to redline but fairly high rpm, and not holding it there either, say snap the throttle to 6k and letoff, not holding for like 10-30seconds, only holding till reaching say 6k rpm for maybe a second nothing more,
i may have worded my question wrong/confusingly Aswell as misunderstood what i read in another post

thanks for the info carlson and mark
ill try find those posts and check them out regarding balancing sounds interesting
 
MasonIsGreat35 said:
this is the information i was asking for, specifics on why it is harmful and what happens, no i do not think i can tune the bike that way just wondering what the differences in reving without load compared to load are, and why it is said not to rev without load for long periods, as i never thought about it before and decided to seek information about it, im new to building motors and slowly trying to learn as much as i can,

originally my question was about giving the throttle a snap without load not holding the throttle at a certain rpm, as i read free reving can blow ur motor, i assumed free reving was jus few revs without load, not to redline but fairly high rpm, and not holding it there either, say snap the throttle to 6k and letoff, not holding for like 10-30seconds, only holding till reaching say 6k rpm for maybe a second nothing more,
i may have worded my question wrong/confusingly Aswell as misunderstood what i read in another post

thanks for the info carlson and mark
ill try find those posts and check them out regarding balancing sounds interesting
Click to expand...
If you're just getting started, you can make a very inexpensive hydraulic dyno that will put adequate load on your engines for breaking them in and for making basic power pulls. I regularly see cheap used dynos for sale -- I think Chip Gronastalski (forgive the spelling) on here has a nice small water brake dyno available right now. That's all you really need to get started, then either upgrade or replace when you are ready. There's no sense in ever revving an engine above idle without load in my opinion.
 
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