High revving engines...piston speeds...discussion inside.
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High revving engines...piston speeds...discussion inside.
Yea, its raining again here...and I am bored with nothing to do.
I am getting a b20z block for my b16, and was wondering how far I can rev the thing, and still be safe, assuming high rev valve springs, built bottom end, and crank girdle.
Now this is a simple look at things I guess, since I do not know exactly how stroke inpacts sidwall loading and other things. Is there a formual for these things??
Anyone know what is a maximum safe piston speed for a daily driven street car? I am going to assume 39.7 m/sec, which is the piston speed of an ITR engine at fuel cut(8700 rpms?) This is interesting...cuz if that is a fact, the CRVTEC should be good to about 8500-8600 rpms.
Also, I compared the b18c5 redline piston speeds to that of a b16a engine....the results seem pretty crazy.
Now, I based my figures on piston speed determined by the following formula.
(RPM x stroke length x 3.14) / 60000
That should give me piston speed in meters per second.
Above this chart shows the piston speeds of a b18c5 compared to a b20z...they are very close, but the difference increases as rpms increase.
This chart shows a b16a vs a b18c5 in a smaller rpm range. Now, I'm not sure if the b16 internals are as strong as the b18c5 internals, but if they are, revving to 9500 rpms shouldn't be too much of a problem if the proper modifications are made. ie: valve springs, and other mods to help the motor produce power to this point...I am thinking jun 3 cams, and lots of other stuff. $$$
Seems to me that building a 2.0 honda, and having it rev to 8000 is probably more cost effective then building a 1.6 honda that revs to 9500+ to make around the same power, but less torque.
Ideas, comments, critisism(spelling)??? Anything to add?
I am getting a b20z block for my b16, and was wondering how far I can rev the thing, and still be safe, assuming high rev valve springs, built bottom end, and crank girdle.
Now this is a simple look at things I guess, since I do not know exactly how stroke inpacts sidwall loading and other things. Is there a formual for these things??
Anyone know what is a maximum safe piston speed for a daily driven street car? I am going to assume 39.7 m/sec, which is the piston speed of an ITR engine at fuel cut(8700 rpms?) This is interesting...cuz if that is a fact, the CRVTEC should be good to about 8500-8600 rpms.
Also, I compared the b18c5 redline piston speeds to that of a b16a engine....the results seem pretty crazy.
Now, I based my figures on piston speed determined by the following formula.
(RPM x stroke length x 3.14) / 60000
That should give me piston speed in meters per second.
Above this chart shows the piston speeds of a b18c5 compared to a b20z...they are very close, but the difference increases as rpms increase.
This chart shows a b16a vs a b18c5 in a smaller rpm range. Now, I'm not sure if the b16 internals are as strong as the b18c5 internals, but if they are, revving to 9500 rpms shouldn't be too much of a problem if the proper modifications are made. ie: valve springs, and other mods to help the motor produce power to this point...I am thinking jun 3 cams, and lots of other stuff. $$$
Seems to me that building a 2.0 honda, and having it rev to 8000 is probably more cost effective then building a 1.6 honda that revs to 9500+ to make around the same power, but less torque.
Ideas, comments, critisism(spelling)??? Anything to add?
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Re: High revving engines...piston speeds...discussion inside. (HXMan)
Nice charts.
Remember that engines with low r/s ratios run out of steam at the top end. You probably won't be making much power at 8K with a really low r/s ratio, so why rev that high?
Remember that engines with low r/s ratios run out of steam at the top end. You probably won't be making much power at 8K with a really low r/s ratio, so why rev that high?
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Re: High revving engines...piston speeds...discussion inside. (Inlinefour)
HXman: what are the components of your formula (the 3.14 and 60000)?
That is definitely an interesting discussion.
That is definitely an interesting discussion.
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Re: High revving engines...piston speeds...discussion inside. (Inlinefour)
inlinefour
The R/S ratio does affect power...but look at a b18c5. Now, you know those engines have plenty of top end power. What is their R/S ratio? 1.58
b20z R/S ratio: 1.52
b16a R/S ratio: 1.74
A b20z with the right head(vtec head)can make power to 8000, and with aftermarket cams can make power beyond that. I just wouldn't want to rev much past that because of the extra wear involved.
However, I belive that an engine with a lower stroke would continue to make power to a higher rpm, because its piston speeds would not become faster then the flame front as soon as an engine with a longer stroke
Check out this dyno of a b20b/z with VTEC head. Look at the power that thing is making.....
Oh, and about my formula. I got it off a guy here. 3.14 is an estimation of pie, and dividing by 60000 gets the speed in m/sec.
[Modified by HXMan, 7:38 AM 9/24/2001]
The R/S ratio does affect power...but look at a b18c5. Now, you know those engines have plenty of top end power. What is their R/S ratio? 1.58
b20z R/S ratio: 1.52
b16a R/S ratio: 1.74
A b20z with the right head(vtec head)can make power to 8000, and with aftermarket cams can make power beyond that. I just wouldn't want to rev much past that because of the extra wear involved.
However, I belive that an engine with a lower stroke would continue to make power to a higher rpm, because its piston speeds would not become faster then the flame front as soon as an engine with a longer stroke
Check out this dyno of a b20b/z with VTEC head. Look at the power that thing is making.....
Oh, and about my formula. I got it off a guy here. 3.14 is an estimation of pie, and dividing by 60000 gets the speed in m/sec.
[Modified by HXMan, 7:38 AM 9/24/2001]
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Re: High revving engines...piston speeds...discussion inside. (HXMan)
I have a B20 LS/VTEC with Toda Spec C camshafts... it would rev nicely to 9,000 but between 9,000 and 9,500 there was a 100 hp loss to the wheel (Dynojet). I was told by my tuner that this is because piston acceleration on a stock stroke, stock rod length LS motor starts to match acceleration of the flame front at around 11,000 rpm and is DAMN close at 9,500.
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Re: High revving engines...piston speeds...discussion inside. (optiontoo)
what kind of numbers were you putting down? I am probably going to get my b16 dynoed soon, and then when the b20vtec is all built, I will dyno that.
So, he said on an LS motor the piston speed begins to match the flame front speed at 9500?
So, he said on an LS motor the piston speed begins to match the flame front speed at 9500?
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Re: High revving engines...piston speeds...discussion inside. (HXMan)
Hey Hxman. How did you derive the formula for piston speed. I have used
(RPM x stroke in mm x 2)/60000. The 2 comes from the piston moving up and down in the bore for one stroke. 60000 is to convert from minutes to seconds, and mm to meters.
(RPM x stroke in mm x 2)/60000. The 2 comes from the piston moving up and down in the bore for one stroke. 60000 is to convert from minutes to seconds, and mm to meters.
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Re: High revving engines...piston speeds...discussion inside. (vteg)
Hmmm...I got the formula from a guy off here...he could have been wrong...DOH!!!
However...stroke isn't the up and down movement combined, it would just be how far the piston moves from TDC to BDC, or vise versa.
However...stroke isn't the up and down movement combined, it would just be how far the piston moves from TDC to BDC, or vise versa.
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Re: High revving engines...piston speeds...discussion inside. (HXMan)
stroke isn't the up and down movement combined, it would just be how far the piston moves from TDC to BDC, or vise versa.
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Re: High revving engines...piston speeds...discussion inside. (vteg)
Keep the thoughts going guys, nice topic...
Here's another thought: When building that B20, why not destroke it with a B17A crank with Eagle rods to have a 1.8 liter with the r/s ratio of a b16a...you are already diong the proper buildup with upgraded valvetrain and a block girdle (and ARP bolts all around I assume) so you can have the best of both worlds.. a lower r/s ratio and the benefits that come with it and the higher displacement. Therefore, you could have a 1.8 that you could rev to 9500 if you felt so inclined. Don't forget the cylender wall webbing reinforcement that the B20 has and the B18's do not, allowing a little more stress in the combo.
Here's another thought: When building that B20, why not destroke it with a B17A crank with Eagle rods to have a 1.8 liter with the r/s ratio of a b16a...you are already diong the proper buildup with upgraded valvetrain and a block girdle (and ARP bolts all around I assume) so you can have the best of both worlds.. a lower r/s ratio and the benefits that come with it and the higher displacement. Therefore, you could have a 1.8 that you could rev to 9500 if you felt so inclined. Don't forget the cylender wall webbing reinforcement that the B20 has and the B18's do not, allowing a little more stress in the combo.
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Re: High revving engines...piston speeds...discussion inside. (Sonic)
Sonic
This I have thought of, and thought of alot.
THe problem is with this route b17 cranks are hard to come by, and if I do find one, they carry a very high price. I even thought about a b18c crank, but the difference is just too small there. I would like to have the ideal R/S ratio and the ability to rev to 9000+ rpms...
...but, the b20 crank will give me great torque. I happen to really like torque also. Street driving will be very nice, and when I need to go fast, VTEC will allways be there.
Do you have anymore information about the "cylinder wall webbing reinforcement" the b20b/z has that the b18s do not? I am curious...also, does ARP make bolts for pretty much all the important points on the B series engines?
vteg
About the formula, you may be right. Even if my formula is wrong, the assumptions I made should still be right, the numbers are just wrong, but that won't change the shape of the charts.
Anyone know the speed of a flame front? Assuming normal gas.
[Modified by HXMan, 11:03 PM 9/24/2001]
Here's another thought: When building that B20, why not destroke it with a B17A crank with Eagle rods to have a 1.8 liter with the r/s ratio of a b16a
THe problem is with this route b17 cranks are hard to come by, and if I do find one, they carry a very high price. I even thought about a b18c crank, but the difference is just too small there. I would like to have the ideal R/S ratio and the ability to rev to 9000+ rpms...
...but, the b20 crank will give me great torque. I happen to really like torque also. Street driving will be very nice, and when I need to go fast, VTEC will allways be there.
Do you have anymore information about the "cylinder wall webbing reinforcement" the b20b/z has that the b18s do not? I am curious...also, does ARP make bolts for pretty much all the important points on the B series engines?
vteg
About the formula, you may be right. Even if my formula is wrong, the assumptions I made should still be right, the numbers are just wrong, but that won't change the shape of the charts.
Anyone know the speed of a flame front? Assuming normal gas.
[Modified by HXMan, 11:03 PM 9/24/2001]
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Re: High revving engines...piston speeds...discussion inside. (HXMan)
Oh, if you want to see pics of the b20 block I will most likely be getting check this out: (pics inside)
https://honda-tech.com/zerothread?id=71730
And, feel free to answer the questions too....I never really did work on a block before, I am just learning.
https://honda-tech.com/zerothread?id=71730
And, feel free to answer the questions too....I never really did work on a block before, I am just learning.
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Re: High revving engines...piston speeds...discussion inside. (HXMan)
That is true. Take a look at this link http://www.aros.net/~rbuck/rick/rodstudy.htm
It has some interesting on r/s ratio, and wall loading. I have always wondered how the perfect 1.75 r/s ratio was developed. I am sure it is a compromise between wall loading, cylinder filling and rod weight. Is this still valid with todays material and engines. What is the r/s ratio in the formula engines that rev to 15k+? We need an ME in here.
It has some interesting on r/s ratio, and wall loading. I have always wondered how the perfect 1.75 r/s ratio was developed. I am sure it is a compromise between wall loading, cylinder filling and rod weight. Is this still valid with todays material and engines. What is the r/s ratio in the formula engines that rev to 15k+? We need an ME in here.
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Re: High revving engines...piston speeds...discussion inside. (vteg)
As far as the formula engines....I do know they use a large bore, and short stroke. The large bore allows the intake and exhuast valves to be completly unshrouded, permitting maximum airflow at high rpms. I don't know specifics. I also read they don't have a very high statch compression ratio, but that is made up for by the high rpm air flow.
1.75 is a compromise for those things you listed probably, and it also gives you a good compromise between hp and torque between certain rpms.
I wish I could go into more detail, but I don't know much besides enought to scratch the surface of all this. Although, what I know allways blows away the rest of my friends when we get on the topic of engines!
1.75 is a compromise for those things you listed probably, and it also gives you a good compromise between hp and torque between certain rpms.
I wish I could go into more detail, but I don't know much besides enought to scratch the surface of all this. Although, what I know allways blows away the rest of my friends when we get on the topic of engines!
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Re: High revving engines...piston speeds...discussion inside. (HXMan)
Hmmm, intresting stuff. I'm looking into my engine revving up higher. I have an LS motor. I know a tighter top-end(springs and retainers) would a margin 300~400 extra RPM. I"m looking to be able to go to 7500 RPM.
I'm will have a turbo kit on my car within the month.
What benefits are there to adding a block girdle?
I'm will have a turbo kit on my car within the month.
What benefits are there to adding a block girdle?
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Re: High revving engines...piston speeds...discussion inside. (HXMan)
HXMan - Because It's Honda and they tend to do things right, when they wanted to bore out a B18B for more displacement, they realized that they would have to strengthen the walls for maximum durability. Most times when the motor is bored out, the cylender walls get dangerously thin. To combat this, there is a webbing that goes through the cylender walls for support and reinforcement ala S2000 and H22a. I don't have the specifics in front of me now, but I'm sure they can be found fairly easily over at the Endyn BBS. ARP does make most studs for Honda motors, and often times the quality rods will come with the ARP bolts that fit them properly. IF you can't find the ARP's, just use new stock bolts.
SpeedPHreak
If you are going turbo, you'll have no need for the extra few RPM's. As said before, RPM = Ruins Peoples Motors. WIth the indroduction of boost into the system I think that you will quickly forget about reving to 7500 and feel that 7000 is plenty. WIth the extra load your engine is going to have from the boost anyway, why make it worse.
SpeedPHreak
If you are going turbo, you'll have no need for the extra few RPM's. As said before, RPM = Ruins Peoples Motors. WIth the indroduction of boost into the system I think that you will quickly forget about reving to 7500 and feel that 7000 is plenty. WIth the extra load your engine is going to have from the boost anyway, why make it worse.
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Re: High revving engines...piston speeds...discussion inside. (Speed PHreak)
Sonic is right. RPMs puts even more stress on a motor then boost. I guess rods can handle compressional forces better then they can handle tensional forces.
Thanks for the info sonic...I will have to check out the endyn BBS...even though I Really don't like that guy.
Thanks for the info sonic...I will have to check out the endyn BBS...even though I Really don't like that guy.
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Re: High revving engines...piston speeds...discussion inside. (HXMan)
Well the thing we have to remember here is where stress is comming from.
Ignoring heat and what not, boost creates more torque by creating higher cylinder pressures, which makes it have a higher compressive load for the engine.
Higher redlines, and crazy speeds of the pistons will cause inertial loads to increase, since the whole thing does have to stop...so if the piston is moving very very fast, it's going to have to stop very very fast and move the other way fast...Force = mass* accel. So more acceleration means more force....a bad thing
.. Inertial loads work double shifts, they have both compression loads, and tensile loads....so twice the stress for the buck.
If i remember correctly inertial loads are also a function of the square of the speed, so double the speed, four times the load
Good news though, sorta, in a power stroke, the tensile load (pulling) at the TDC is offset by some of the compressive load caused by the expansion of the combustion chamber's inhabitants. So the connecting rod is getting a little extra push so the sum of the forces will be enough, and the stress on the bearing isnt that bad , because it doesnt have to yank it too hard.
However, this assistance does not happen a rotation from now, at the TDC in the exhaust stroke, the con rod has to do all the work and supply all the force for the downward movment of the piston....this is the most stressful part of the 4 cycle for the connecting rod and bearing
RPM = Ruins People's motors.
Boost, well it sorta helps move the piston, but it also CAN ruin's people's motors
[Modified by Ricehornet, 6:44 PM 9/25/2001]
Ignoring heat and what not, boost creates more torque by creating higher cylinder pressures, which makes it have a higher compressive load for the engine.
Higher redlines, and crazy speeds of the pistons will cause inertial loads to increase, since the whole thing does have to stop...so if the piston is moving very very fast, it's going to have to stop very very fast and move the other way fast...Force = mass* accel. So more acceleration means more force....a bad thing
.. Inertial loads work double shifts, they have both compression loads, and tensile loads....so twice the stress for the buck.If i remember correctly inertial loads are also a function of the square of the speed, so double the speed, four times the load
Good news though, sorta, in a power stroke, the tensile load (pulling) at the TDC is offset by some of the compressive load caused by the expansion of the combustion chamber's inhabitants. So the connecting rod is getting a little extra push so the sum of the forces will be enough, and the stress on the bearing isnt that bad , because it doesnt have to yank it too hard.
However, this assistance does not happen a rotation from now, at the TDC in the exhaust stroke, the con rod has to do all the work and supply all the force for the downward movment of the piston....this is the most stressful part of the 4 cycle for the connecting rod and bearing
RPM = Ruins People's motors.
Boost, well it sorta helps move the piston, but it also CAN ruin's people's motors
[Modified by Ricehornet, 6:44 PM 9/25/2001]
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Re: High revving engines...piston speeds...discussion inside. (HXMan)
(RPM x stroke length x 3.14) / 60000
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Re: High revving engines...piston speeds...discussion inside. (Ricehornet)
[QUOTE]
However, this assistance does not happen a rotation from now, at the TDC in the exhaust stroke, the con rod has to do all the work and supply all the force for the downward movment of the piston....this is the most stressful part of the 4 cycle for the connecting rod and bearing
QUOTE]
Yea, I read somewhere that that connecting rods often break on the exhuast stroke...now I finally know why!
Wow, if inertial loads are what you said, the load would increase exponentially.....meaning a small increase in rpms could have a very large impact on the stresses put on the rods and bearings.
Thanks for verifiying my formula too!
However, this assistance does not happen a rotation from now, at the TDC in the exhaust stroke, the con rod has to do all the work and supply all the force for the downward movment of the piston....this is the most stressful part of the 4 cycle for the connecting rod and bearing
QUOTE]
Yea, I read somewhere that that connecting rods often break on the exhuast stroke...now I finally know why!
Wow, if inertial loads are what you said, the load would increase exponentially.....meaning a small increase in rpms could have a very large impact on the stresses put on the rods and bearings.
Thanks for verifiying my formula too!
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Re: High revving engines...piston speeds...discussion inside. (GSRMatt)
from http://www.motorcycle.com/mo/mcrob/rt-fuel2.html
and from http://www.student.lu.se/~imm94pst/glowplug_engine.html
I found other, undocumented references that actual propogation speeds are on the order of 3-4000 cm/s, and that detonation propogation speeds are more like 50,000 cm/s
Basically actual flame front propogation speed depends on port/valve/piston configuration, and is difficult to accurately determine. What is easier measured is combustion time, I'll try to dig up some papers on this and post later.
First, a pressure wave, which is generated during the initial ignition at the plug
tip, races through the unburned air-fuel mix ahead of the flame front. Typical flame front speeds for a gasoline/air mixture are on the order of 40 to 50 cm/s
(centimeters per second), which is very slow
compared to the speed of sound, which is on the
order of 300 m/s. In actuality, the true speed of
the outwards propagating flame front is
considerably higher due to the turbulence of the
mixture. Basically, the "flame" is carried outwards
by all the little eddies, swirls and flow patterns of
the turbulence resident in the air-fuel mix. This
model of combustion is called the "eddy burning
model" (Blizzard & Keck, 1974).
tip, races through the unburned air-fuel mix ahead of the flame front. Typical flame front speeds for a gasoline/air mixture are on the order of 40 to 50 cm/s
(centimeters per second), which is very slow
compared to the speed of sound, which is on the
order of 300 m/s. In actuality, the true speed of
the outwards propagating flame front is
considerably higher due to the turbulence of the
mixture. Basically, the "flame" is carried outwards
by all the little eddies, swirls and flow patterns of
the turbulence resident in the air-fuel mix. This
model of combustion is called the "eddy burning
model" (Blizzard & Keck, 1974).
Flames and laminar flame speeds
Try to follow this example:
First we start off by having a quiescent fluid. This means a mixture of air and fuel, all in gas phase. Everything in the container is still, no movement of the gases. But
the gas is well mixed.
Then a spark will the shoot off on one side of the container. Now we would see a flame front propagating throu the fluid. What will be seen is a light emitting sheet
traveling thru the fluid concentrically from the spark onwards.
The speed of which the flame propagates in this case is call the laminar flame speed. For methanol it is about 40[cm/s] at room temperature and pressure.
Methanol burn pretty fast, gasoline burns about 10-20% slower. But remember! The laminar flame speed is dependent on air / fuel ratio, pressure and temperature.
All in all if one puts numbers behind combustion duration and the speed that our engine have. we will see that things don't add up. If the gas burned with laminar
flame velocity. The engine would not rev. Example follows:
Say that we run the engine at 15000 rpm. There is 250 combustions per second. We will assume that the combustion duration is 80 ° Crank angle degree (CAD).
That makes the entire combustion time per cycle to 0.8 ms. Say that the flame has to travel 1 cm, this makes the flame velocity of about 1100 cm/s. This is about 30
times to slow compared to he laminar flame velocity. So things must go much faster.
Turbulence
First I will try to explain how turbulence affects our engines. I will not explain in detail what turbulence actually is, because can be a hot hot potato. When a fluid (gas
or liquid) flow slowly, it usually flows with a laminar flow pattern. When the flow speed increased it's flow pattern is turbulent (irregular).
If you look at the smoke coming from a cigarette. The first part of the smoke it smooth, there are smooth flow lines, later on there will be a transition to a more
irregular pattern. This is the transition from laminar to turbulent flow.
The same thing can also be seen when looking at the water flowing out of a fawset.
If a flame is ignited in a turbulent flowing environment, the burn rate increases considerable. It makes the flame go so fast as it will bridge up the gap between the
laminar case to the turbulent case.
Turbulence make the flame go faster. There is also some evidence that strong turbulence will stabilize the combustion. If the mix is uneven, strong turbulence will
stabilize this.
How turbulence is created
It is not very hard to imagine that the flow inside an engine that has 250 cycles per seconds should be turbulent. But there are still mechanisms that controls the burn
rate in the engine.
Squish
You might have heard about the squish area. It is the outer part of the combustion camber. During the last part of the compression stroke the the gas that resides
below the squish area will be forced towards the center of the combustion chamber. This high velocity movement will generate high intensity turbulence during
combustion.
By changing the area of the squish band the amount of gas that is forced is changed and effectively changing the turbulence.
Try to follow this example:
First we start off by having a quiescent fluid. This means a mixture of air and fuel, all in gas phase. Everything in the container is still, no movement of the gases. But
the gas is well mixed.
Then a spark will the shoot off on one side of the container. Now we would see a flame front propagating throu the fluid. What will be seen is a light emitting sheet
traveling thru the fluid concentrically from the spark onwards.
The speed of which the flame propagates in this case is call the laminar flame speed. For methanol it is about 40[cm/s] at room temperature and pressure.
Methanol burn pretty fast, gasoline burns about 10-20% slower. But remember! The laminar flame speed is dependent on air / fuel ratio, pressure and temperature.
All in all if one puts numbers behind combustion duration and the speed that our engine have. we will see that things don't add up. If the gas burned with laminar
flame velocity. The engine would not rev. Example follows:
Say that we run the engine at 15000 rpm. There is 250 combustions per second. We will assume that the combustion duration is 80 ° Crank angle degree (CAD).
That makes the entire combustion time per cycle to 0.8 ms. Say that the flame has to travel 1 cm, this makes the flame velocity of about 1100 cm/s. This is about 30
times to slow compared to he laminar flame velocity. So things must go much faster.
Turbulence
First I will try to explain how turbulence affects our engines. I will not explain in detail what turbulence actually is, because can be a hot hot potato. When a fluid (gas
or liquid) flow slowly, it usually flows with a laminar flow pattern. When the flow speed increased it's flow pattern is turbulent (irregular).
If you look at the smoke coming from a cigarette. The first part of the smoke it smooth, there are smooth flow lines, later on there will be a transition to a more
irregular pattern. This is the transition from laminar to turbulent flow.
The same thing can also be seen when looking at the water flowing out of a fawset.
If a flame is ignited in a turbulent flowing environment, the burn rate increases considerable. It makes the flame go so fast as it will bridge up the gap between the
laminar case to the turbulent case.
Turbulence make the flame go faster. There is also some evidence that strong turbulence will stabilize the combustion. If the mix is uneven, strong turbulence will
stabilize this.
How turbulence is created
It is not very hard to imagine that the flow inside an engine that has 250 cycles per seconds should be turbulent. But there are still mechanisms that controls the burn
rate in the engine.
Squish
You might have heard about the squish area. It is the outer part of the combustion camber. During the last part of the compression stroke the the gas that resides
below the squish area will be forced towards the center of the combustion chamber. This high velocity movement will generate high intensity turbulence during
combustion.
By changing the area of the squish band the amount of gas that is forced is changed and effectively changing the turbulence.
Basically actual flame front propogation speed depends on port/valve/piston configuration, and is difficult to accurately determine. What is easier measured is combustion time, I'll try to dig up some papers on this and post later.
New User
Joined: Apr 2001
Posts: 3,129
Likes: 0
From: Los Angeles, CA, USA
Re: High revving engines...piston speeds...discussion inside. (GSRMatt)
You answer intrigued me so I did a little research. The accepted formulas are as follows:
Formulas for piston speed
piston speed in fpm = stroke in inches x rpm / 6
rpm = piston speed in fpm x 6 / stroke in inches
These are in inches and feet though. But when you solve these algebraically with units, and then apply them to the metric system, my formula is correct. Just for a quicky, my bone stock gsr with 87mm stroke at 8100.
fpm = 87/25.4 * 8100/6 = 4624.01
m/s = fpm * .3408/60 = 23.49
My formula will give you the same result.
I understand at this point in this post this is more like nitpicking, but I would rather see correct information being passed on here. I am the first to admit when I am wrong. Thinking about the formula you posted, I think it should give calculation of crankshaft speed. Why else would you use pi in speed except for circular motion.
Sources:
http://www.nightrider.com/biketech/c...mulas_page.htm
http://www.angelfire.com/sd/BSP/formula.html
http://www.mustangsandmore.com/ubb/S...stonspeed.html
Formulas for piston speed
piston speed in fpm = stroke in inches x rpm / 6
rpm = piston speed in fpm x 6 / stroke in inches
These are in inches and feet though. But when you solve these algebraically with units, and then apply them to the metric system, my formula is correct. Just for a quicky, my bone stock gsr with 87mm stroke at 8100.
fpm = 87/25.4 * 8100/6 = 4624.01
m/s = fpm * .3408/60 = 23.49
My formula will give you the same result.
I understand at this point in this post this is more like nitpicking, but I would rather see correct information being passed on here. I am the first to admit when I am wrong. Thinking about the formula you posted, I think it should give calculation of crankshaft speed. Why else would you use pi in speed except for circular motion.
Sources:
http://www.nightrider.com/biketech/c...mulas_page.htm
http://www.angelfire.com/sd/BSP/formula.html
http://www.mustangsandmore.com/ubb/S...stonspeed.html
Honda-Tech Member
Joined: Jan 2000
Posts: 1,771
Likes: 1
From: Charlotte, NC, USA
Re: High revving engines...piston speeds...discussion inside. (HXMan)
Does anyone know of a site that would explain this and other engine (mechanical) characteristics?
I'm actually studying to be an ME but I won't be doing anything but math and physics for 2 more years.
I'm actually studying to be an ME but I won't be doing anything but math and physics for 2 more years.
New User
Joined: Apr 2001
Posts: 3,129
Likes: 0
From: Los Angeles, CA, USA
Re: High revving engines...piston speeds...discussion inside. (GSpeedR)
I would suggest an engine building book. Unfortunately, I don't have one to recommend, since the only one I own I bought over 5 years ago when I owned my mustang