TQ vs HP :: RPMs
05-02-2007, 04:30 PM
#26
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Re: TQ vs HP :: RPMs (bluedlude)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by bluedlude »</TD></TR><TR><TD CLASS="quote">designing an engine is a bitch ?? 
</TD></TR></TABLE>
yeah i'd say so
im not sure where the original post came to this and im not sure if i really learned anything but it was defiantly a fun topic to talk about
</TD></TR></TABLE>yeah i'd say so
im not sure where the original post came to this and im not sure if i really learned anything but it was defiantly a fun topic to talk about
05-02-2007, 04:41 PM
#28
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Re: TQ vs HP :: RPMs (bluedlude)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by bluedlude »</TD></TR><TR><TD CLASS="quote">these are the threads i live for. ones that make you think. but i have a final tomorrow, so off to control systems i go....</TD></TR></TABLE>
yeah i have spent way too much time on HT and Myspace for one day im off too. (for the day)
yeah i have spent way too much time on HT and Myspace for one day im off too. (for the day)
05-02-2007, 06:12 PM
#29
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Re: TQ vs HP :: RPMs (85)
Pretty much already stated, but I'll say it again as a bump 
An undersquare engine's torque will peak sooner (rpm wise) than than an oversquare motor of the same displacement/configuration. For a given engine size , the the higher up in the rpm range you have your torque peak (peak VE), the more hp you will produce, given the formula
HP= (torque X rpm)/ 5252.
As kind of a side note, increasing displacement , or increasing your rpm limit, are the 2 main ways (only ways? -maybe raising CR could be considered one) to increasing an engines power potential. In this post/question, since displacement is constant, raising your rpm limit is the choice for more hp (potential). so again the undersquare motor seem to me to be the better choice.
Correct me if I'm wrong anywhere DonF - I gleaned a lot of this info from your past posts.
here's a good article I came across recently on his subject (thanks to Mike B's website for the link): (article #53)
http://www.rehermorrison.com/techTalk/
An undersquare engine's torque will peak sooner (rpm wise) than than an oversquare motor of the same displacement/configuration. For a given engine size , the the higher up in the rpm range you have your torque peak (peak VE), the more hp you will produce, given the formula HP= (torque X rpm)/ 5252.
As kind of a side note, increasing displacement , or increasing your rpm limit, are the 2 main ways (only ways? -maybe raising CR could be considered one) to increasing an engines power potential. In this post/question, since displacement is constant, raising your rpm limit is the choice for more hp (potential). so again the undersquare motor seem to me to be the better choice.
Correct me if I'm wrong anywhere DonF - I gleaned a lot of this info from your past posts.
here's a good article I came across recently on his subject (thanks to Mike B's website for the link): (article #53)
http://www.rehermorrison.com/techTalk/
05-02-2007, 06:16 PM
#30
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Thread Starter
Re: TQ vs HP :: RPMs (clarkekent13)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by clarkekent13 »</TD></TR><TR><TD CLASS="quote">Pretty much already stated, but I'll say it again as a bump An undersquare engine's torque will peak sooner (rpm wise) than than an oversquare motor of the same displacement/configuration. For a given engine size , the the higher up in the rpm range you have your torque peak (peak VE), the more hp you will produce, given the formula
HP= (torque X rpm)/ 5252.
As kind of a side note, increasing displacement , or increasing your rpm limit, are the 2 main ways (only ways? -maybe raising CR could be considered one) to increasing an engines power potential. In this post/question, since displacement is constant, raising your rpm limit is the choice for more hp (potential). so again the undersquare motor seem to me to be the better choice.
Correct me if I'm wrong anywhere DonF - I gleaned a lot of this info from your past posts.
here's a good article I came across recently on his subject (thanks to Mike B's website for the link): (article #53)
http://www.rehermorrison.com/techTalk/
</TD></TR></TABLE>
yeah i said i wouldnt be back on tonight but i have no life...
so WHY does higher compression raise power? that i dont know. closer molecules?
An undersquare engine's torque will peak sooner (rpm wise) than than an oversquare motor of the same displacement/configuration. For a given engine size , the the higher up in the rpm range you have your torque peak (peak VE), the more hp you will produce, given the formula HP= (torque X rpm)/ 5252.
As kind of a side note, increasing displacement , or increasing your rpm limit, are the 2 main ways (only ways? -maybe raising CR could be considered one) to increasing an engines power potential. In this post/question, since displacement is constant, raising your rpm limit is the choice for more hp (potential). so again the undersquare motor seem to me to be the better choice.
Correct me if I'm wrong anywhere DonF - I gleaned a lot of this info from your past posts.
here's a good article I came across recently on his subject (thanks to Mike B's website for the link): (article #53)
http://www.rehermorrison.com/techTalk/
</TD></TR></TABLE>
yeah i said i wouldnt be back on tonight but i have no life...
so WHY does higher compression raise power? that i dont know. closer molecules?
05-02-2007, 06:31 PM
#31
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Re: TQ vs HP :: RPMs (85)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 85 »</TD></TR><TR><TD CLASS="quote">
yeah i said i wouldnt be back on tonight but i have no life...
so WHY does higher compression raise power? that i dont know. closer molecules? </TD></TR></TABLE>
the higher compression you have, the more air that is being packed into a smaller area, creating a bigger "bang"
All motor - you want highest compression possible keeping it reasonable for street use, depending on what the setup is made for though...
Forced induction - pack more air into the cylinders that the engine can naturally produce which in turn creates more compression.
yeah i said i wouldnt be back on tonight but i have no life...
so WHY does higher compression raise power? that i dont know. closer molecules? </TD></TR></TABLE>
the higher compression you have, the more air that is being packed into a smaller area, creating a bigger "bang"
All motor - you want highest compression possible keeping it reasonable for street use, depending on what the setup is made for though...
Forced induction - pack more air into the cylinders that the engine can naturally produce which in turn creates more compression.
05-02-2007, 06:33 PM
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Re: TQ vs HP :: RPMs (85)
As I understand it, the more you compress an explosive mixture, the more powerful of an explosion it will make. I don't know enough on the subject to attempt to explain it more technically, but closer molecules, promoting a faster burn rate, could have something to do with it. Maybe someone with more knowledge can chime in.
05-02-2007, 07:01 PM
#33
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Re: TQ vs HP :: RPMs (clarkekent13)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by clarkekent13 »</TD></TR><TR><TD CLASS="quote">As I understand it, the more you compress an explosive mixture, the more powerful of an explosion it will make. I don't know enough on the subject to attempt to explain it more technically, but closer molecules, promoting a faster burn rate, could have something to do with it. Maybe someone with more knowledge can chime in.</TD></TR></TABLE>
I guess this is where VOD comes in (velocity of Detonation) or rather VOI (velocity of ignition) which is something i just made up because i dont know what else to call it.
After thinking about it for some time i came up with this...
think of the power stroke in a %age from 1 being the split second when the spark fires and 100% being the end. if it takes the fuel 100 to complete burning then at the beginning of the power stroke you dont have much pressure. on the other hand, you have detonation where all the fuel is ignited at 0% to which you have wayyy too much pressure that can punch hole in pistons and crack sleeves.
If the molecules are closer together its VOI is going to be quicker making pressure sooner which in turn pushed on the piston for a longer period of time.
this is just my thoughts on it, im not saying its right so feel free to correct me if you know the answer.
I guess this is where VOD comes in (velocity of Detonation) or rather VOI (velocity of ignition) which is something i just made up because i dont know what else to call it.
After thinking about it for some time i came up with this...
think of the power stroke in a %age from 1 being the split second when the spark fires and 100% being the end. if it takes the fuel 100 to complete burning then at the beginning of the power stroke you dont have much pressure. on the other hand, you have detonation where all the fuel is ignited at 0% to which you have wayyy too much pressure that can punch hole in pistons and crack sleeves.
If the molecules are closer together its VOI is going to be quicker making pressure sooner which in turn pushed on the piston for a longer period of time.
this is just my thoughts on it, im not saying its right so feel free to correct me if you know the answer.
05-02-2007, 07:11 PM
#34
Thats true, lol VOI
When you compress the mixture more, you're making it more volatile, that is why higher cr engines risk detonation. The benefit of this higher volatility is that it explodes harder, ie picking up power with higher CRs.
Its all about torque, horsepower is just a function of the physical quality torque, it tells you how well the engine carries torque into high rpm. When you apply 150lbs of mean torque at 8000rpm you're applying twice as much as 150lbs of torque at 4000rpm. In that light, higher rpm is always better.
The problem with that is that it is tough to make a reliable engine that can displace over 2l and rev to very high rpm all the time. Head porting and cam sizing is also an issue, as that stuff needs to be huge to make torque way up in the rpm band, and coupled with high compression, there is a limit on cam size.
I like this thread
When you compress the mixture more, you're making it more volatile, that is why higher cr engines risk detonation. The benefit of this higher volatility is that it explodes harder, ie picking up power with higher CRs.
Its all about torque, horsepower is just a function of the physical quality torque, it tells you how well the engine carries torque into high rpm. When you apply 150lbs of mean torque at 8000rpm you're applying twice as much as 150lbs of torque at 4000rpm. In that light, higher rpm is always better.
The problem with that is that it is tough to make a reliable engine that can displace over 2l and rev to very high rpm all the time. Head porting and cam sizing is also an issue, as that stuff needs to be huge to make torque way up in the rpm band, and coupled with high compression, there is a limit on cam size.
I like this thread
05-02-2007, 07:35 PM
#35
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Re: (mgags7)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mgags7 »</TD></TR><TR><TD CLASS="quote">Thats true, lol VOI
When you compress the mixture more, you're making it more volatile, that is why higher cr engines risk detonation. The benefit of this higher volatility is that it explodes harder, ie picking up power with higher CRs.
Its all about torque, horsepower is just a function of the physical quality torque, it tells you how well the engine carries torque into high rpm. When you apply 150lbs of mean torque at 8000rpm you're applying twice as much as 150lbs of torque at 4000rpm. In that light, higher rpm is always better.
The problem with that is that it is tough to make a reliable engine that can displace over 2l and rev to very high rpm all the time. Head porting and cam sizing is also an issue, as that stuff needs to be huge to make torque way up in the rpm band, and coupled with high compression, there is a limit on cam size.
I like this thread</TD></TR></TABLE>
i think its also a matter of the VOI and how long it will take for the combustion to complete. the higher the RPMs the less time there is to burn meaning the peak pressure build up occurs later in the power stroke or perhaps doesnt ever finish. look at F1 cars with 3.0L engines reving to 22,000 RPMs. they are V12s. raising the CR could also aid with the higher RPMs as well as larger cams
why do huge race cams require high compression? prob because the VOI needs to be high enough to complete the burn before the exhaust valves open
with over 1500 posts on HT i think this is one of my fav threads!
When you compress the mixture more, you're making it more volatile, that is why higher cr engines risk detonation. The benefit of this higher volatility is that it explodes harder, ie picking up power with higher CRs.
Its all about torque, horsepower is just a function of the physical quality torque, it tells you how well the engine carries torque into high rpm. When you apply 150lbs of mean torque at 8000rpm you're applying twice as much as 150lbs of torque at 4000rpm. In that light, higher rpm is always better.
The problem with that is that it is tough to make a reliable engine that can displace over 2l and rev to very high rpm all the time. Head porting and cam sizing is also an issue, as that stuff needs to be huge to make torque way up in the rpm band, and coupled with high compression, there is a limit on cam size.
I like this thread
</TD></TR></TABLE>i think its also a matter of the VOI and how long it will take for the combustion to complete. the higher the RPMs the less time there is to burn meaning the peak pressure build up occurs later in the power stroke or perhaps doesnt ever finish. look at F1 cars with 3.0L engines reving to 22,000 RPMs. they are V12s. raising the CR could also aid with the higher RPMs as well as larger cams
why do huge race cams require high compression? prob because the VOI needs to be high enough to complete the burn before the exhaust valves open
with over 1500 posts on HT i think this is one of my fav threads!
05-02-2007, 10:16 PM
#36
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Re: (85)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 85 »</TD></TR><TR><TD CLASS="quote">
the higher the RPMs the less time there is to burn meaning the peak pressure build up occurs later in the power stroke or perhaps doesnt ever finish. </TD></TR></TABLE>
couldnt you fix that problem by using a longer rod since the piston will spend more time at tdc?
the higher the RPMs the less time there is to burn meaning the peak pressure build up occurs later in the power stroke or perhaps doesnt ever finish. </TD></TR></TABLE>
couldnt you fix that problem by using a longer rod since the piston will spend more time at tdc?
05-03-2007, 04:29 AM
#38
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Re: (85)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 85 »</TD></TR><TR><TD CLASS="quote">
why do huge race cams require high compression? prob because the VOI needs to be high enough to complete the burn before the exhaust valves open </TD></TR></TABLE>
we are talking static compression here. dynamic compression is different. huge cams bleed huge amounts of dynamic compression so there is need for more static compression to cure the loss of dynamic compression.
on pump gas someone can run 13:1 cr on b16a cams and detonate, and run PRO2's or m24xx and be fine.
and as for the time the explosion has to put it's force on the piston at high rpms. that's why low R/S ratio motors have trouble up top, the piston outruns the flame front. the engine that do run lo R/S ratio motors up high (9K plus) are often running insane C/R's. high R/S ratio means that the pistons spends relativly more time around tdc, so the explosion has more time to put force on the piston. so that complements the statements made.
but it calls for a new question, the longer the piston compresses the mixture, does it increase the change of detonation. if yes, is a high R/S ratio engine more prone to detonation at a high C/R then a low R/S ratio engine at the same c/r?
me like a not very often seen informational and technical discussion
feel free to correct me if i'm wrong at any point
why do huge race cams require high compression? prob because the VOI needs to be high enough to complete the burn before the exhaust valves open </TD></TR></TABLE>
we are talking static compression here. dynamic compression is different. huge cams bleed huge amounts of dynamic compression so there is need for more static compression to cure the loss of dynamic compression.
on pump gas someone can run 13:1 cr on b16a cams and detonate, and run PRO2's or m24xx and be fine.
and as for the time the explosion has to put it's force on the piston at high rpms. that's why low R/S ratio motors have trouble up top, the piston outruns the flame front. the engine that do run lo R/S ratio motors up high (9K plus) are often running insane C/R's. high R/S ratio means that the pistons spends relativly more time around tdc, so the explosion has more time to put force on the piston. so that complements the statements made.
but it calls for a new question, the longer the piston compresses the mixture, does it increase the change of detonation. if yes, is a high R/S ratio engine more prone to detonation at a high C/R then a low R/S ratio engine at the same c/r?
me like a not very often seen informational and technical discussionfeel free to correct me if i'm wrong at any point
05-03-2007, 05:30 AM
#39
I would think that having the piston at tdc longer definitely increases the risk of detonation, so I would suppose that the high R/S engines are at a higher risk, but that should be able to be controlled firstly by the gas used and secondly by the tuner.
This brings consideration of the shape of the piston dome into mind for me. Since detonation can be caused by hot spots on the piston, wouldn't it make sense to have a flat piston, forcing all the heat to spread out, unlike the huge domed pistons where all the heat gets trapped on the edges.
Wouldn't a flat top piston be optimal anyway, because when the flame pushes down it has an even flat surface to push on at a perfect right angle to rotation, rather than pushing on a domed piston at say 45 degrees angle to vertical??
This brings consideration of the shape of the piston dome into mind for me. Since detonation can be caused by hot spots on the piston, wouldn't it make sense to have a flat piston, forcing all the heat to spread out, unlike the huge domed pistons where all the heat gets trapped on the edges.
Wouldn't a flat top piston be optimal anyway, because when the flame pushes down it has an even flat surface to push on at a perfect right angle to rotation, rather than pushing on a domed piston at say 45 degrees angle to vertical??
05-03-2007, 06:03 AM
#40
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Re: (mgags7)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mgags7 »</TD></TR><TR><TD CLASS="quote">I would think that having the piston at tdc longer definitely increases the risk of detonation, so I would suppose that the high R/S engines are at a higher risk, but that should be able to be controlled firstly by the gas used and secondly by the tuner.
This brings consideration of the shape of the piston dome into mind for me. Since detonation can be caused by hot spots on the piston, wouldn't it make sense to have a flat piston, forcing all the heat to spread out, unlike the huge domed pistons where all the heat gets trapped on the edges.
Wouldn't a flat top piston be optimal anyway, because when the flame pushes down it has an even flat surface to push on at a perfect right angle to rotation, rather than pushing on a domed piston at say 45 degrees angle to vertical??</TD></TR></TABLE>
I think flat top piston efficiency has more to do with thermal efficiency and less to do with the angle of gas pressure.
looking my into the thermal dynamics of compressing gas (holing it longer at TDC) i dont think is would make a difference. when you compress a gas, it confines its original heat energy making it hotter in a smaller area but does not continue to heat up after it stops compressing. the only reason i could see a higher R:S would aid in detonation would be due to added heat energy to the combustion chamber from the walls of the chamber (head, piston, sleeves). BUT, higher rpms would give it less time to absorb the heat and in turn help prevent detonation in that way. on the other hand the combustion chamber surfaces would end up being hotter with more fuel burning in less time. lower thermostat temp?
its nice talking to people that know what octane rating actually means.
This brings consideration of the shape of the piston dome into mind for me. Since detonation can be caused by hot spots on the piston, wouldn't it make sense to have a flat piston, forcing all the heat to spread out, unlike the huge domed pistons where all the heat gets trapped on the edges.
Wouldn't a flat top piston be optimal anyway, because when the flame pushes down it has an even flat surface to push on at a perfect right angle to rotation, rather than pushing on a domed piston at say 45 degrees angle to vertical??</TD></TR></TABLE>
I think flat top piston efficiency has more to do with thermal efficiency and less to do with the angle of gas pressure.
looking my into the thermal dynamics of compressing gas (holing it longer at TDC) i dont think is would make a difference. when you compress a gas, it confines its original heat energy making it hotter in a smaller area but does not continue to heat up after it stops compressing. the only reason i could see a higher R:S would aid in detonation would be due to added heat energy to the combustion chamber from the walls of the chamber (head, piston, sleeves). BUT, higher rpms would give it less time to absorb the heat and in turn help prevent detonation in that way. on the other hand the combustion chamber surfaces would end up being hotter with more fuel burning in less time. lower thermostat temp?
its nice talking to people that know what octane rating actually means.
05-03-2007, 08:23 AM
#41
Re: (85)
I always though that a higher r/s ratio in a given motor will move the powerband higher, but at the same time making it narrower (requiring more gears like F-1). This was the reason that engine builders use the golden rule of 1.72:1 r/s ratio when designing a new high performance engine (like the b16a)...
Do you guys agree that you wouldn't want too tall of a r/s ratio because you will be left zero low end, no drive-ability and a ridiculously peaky engine...
Do you guys agree that you wouldn't want too tall of a r/s ratio because you will be left zero low end, no drive-ability and a ridiculously peaky engine...
05-03-2007, 08:44 AM
#42
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Re: (94eg!)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 94eg! »</TD></TR><TR><TD CLASS="quote">I always though that a higher r/s ratio in a given motor will move the powerband higher, but at the same time making it narrower (requiring more gears like F-1). This was the reason that engine builders use the golden rule of 1.72:1 r/s ratio when designing a new high performance engine (like the b16a)...
Do you guys agree that you wouldn't want too tall of a r/s ratio because you will be left zero low end, no drive-ability and a ridiculously peaky engine...</TD></TR></TABLE>
isnt that the point? i would never build a car do do 6th gear pulls at 3000 RPMs. I dont care what anyone says, a B16 is not a race motor. yes its hagher performance then most street engines but its still designed for nothing more then driving around on the street. if your building a motor to have 350whp N/A its going to have huge cams. those cams which will require high compression so why no have every part of the engine tuned to the same RPM range? if you wanted an engine with good mid range would you tune half of the cylinders for top end and half for bottom end?
as for the golden rule, ive always herd that number but times change, engine technology is better now then it ever was before. we have lighter stronger parts now, and as stated before, TQ X RPMs = HP so if your going to make maximum HP you need every possible part of the engine tuned with higher RPMs in mind. I do understand what you are saying though. a power band thats only 500rpms wide is almost pointless but i think its safe to say, that the 1.72 R:S can go up. The Nissan SE-R (2.5L) has a 1.74 and its got a nice wide power band. it would be cool if someone could find what F1 cars old or new were running just as a comparison. I wonder what bikes are running?
Do you guys agree that you wouldn't want too tall of a r/s ratio because you will be left zero low end, no drive-ability and a ridiculously peaky engine...</TD></TR></TABLE>
isnt that the point? i would never build a car do do 6th gear pulls at 3000 RPMs. I dont care what anyone says, a B16 is not a race motor. yes its hagher performance then most street engines but its still designed for nothing more then driving around on the street. if your building a motor to have 350whp N/A its going to have huge cams. those cams which will require high compression so why no have every part of the engine tuned to the same RPM range? if you wanted an engine with good mid range would you tune half of the cylinders for top end and half for bottom end?
as for the golden rule, ive always herd that number but times change, engine technology is better now then it ever was before. we have lighter stronger parts now, and as stated before, TQ X RPMs = HP so if your going to make maximum HP you need every possible part of the engine tuned with higher RPMs in mind. I do understand what you are saying though. a power band thats only 500rpms wide is almost pointless but i think its safe to say, that the 1.72 R:S can go up. The Nissan SE-R (2.5L) has a 1.74 and its got a nice wide power band. it would be cool if someone could find what F1 cars old or new were running just as a comparison. I wonder what bikes are running?
05-03-2007, 09:48 AM
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Re: (wolve)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by wolve »</TD></TR><TR><TD CLASS="quote">
we are talking static compression here. dynamic compression is different. huge cams bleed huge amounts of dynamic compression so there is need for more static compression to cure the loss of dynamic compression.
on pump gas someone can run 13:1 cr on b16a cams and detonate, and run PRO2's or m24xx and be fine.
</TD></TR></TABLE>
I would like you to re-think this a little bit, I thought the same until a little schooling. What happens when the VE goes over 100%? That rule would be ok for an inefficient motor but does not work with what were trying to achieve in this post.
FYI: This is Natural Aspirations not 80884
we are talking static compression here. dynamic compression is different. huge cams bleed huge amounts of dynamic compression so there is need for more static compression to cure the loss of dynamic compression.
on pump gas someone can run 13:1 cr on b16a cams and detonate, and run PRO2's or m24xx and be fine.
</TD></TR></TABLE>
I would like you to re-think this a little bit, I thought the same until a little schooling. What happens when the VE goes over 100%? That rule would be ok for an inefficient motor but does not work with what were trying to achieve in this post.
FYI: This is Natural Aspirations not 80884
05-03-2007, 12:45 PM
#45
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Re: (80884)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 80884 »</TD></TR><TR><TD CLASS="quote">
I would like you to re-think this a little bit, I thought the same until a little schooling. What happens when the VE goes over 100%? That rule would be ok for an inefficient motor but does not work with what were trying to achieve in this post.
FYI: This is Natural Aspirations not 80884</TD></TR></TABLE>
80884?
I would like you to re-think this a little bit, I thought the same until a little schooling. What happens when the VE goes over 100%? That rule would be ok for an inefficient motor but does not work with what were trying to achieve in this post.
FYI: This is Natural Aspirations not 80884</TD></TR></TABLE>
80884?
05-03-2007, 12:56 PM
#46
Re: (85)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 85 »</TD></TR><TR><TD CLASS="quote">
80884?</TD></TR></TABLE>
He's saying he's using someone else's screen name (he's logged in as 80884)...
80884?</TD></TR></TABLE>
He's saying he's using someone else's screen name (he's logged in as 80884)...
05-03-2007, 01:23 PM
#47
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Re: (94eg!)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 94eg! »</TD></TR><TR><TD CLASS="quote">
He's saying he's using someone else's screen name (he's logged in as 80884)...</TD></TR></TABLE>
oh, ha!
He's saying he's using someone else's screen name (he's logged in as 80884)...</TD></TR></TABLE>
oh, ha!
05-03-2007, 05:16 PM
#48
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Re: (85)
Dammit, whos posting under my name in the all motor forum? Natural Aspirations, I'm gonna have to send some boost your way to straighten you up if you keep posting under my name!
05-03-2007, 05:51 PM
#49
Honda-Tech Member
Join Date: Sep 2003
Location: Austin, Republic of Texas
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great but. . .
Misc. ramblings:
The early comment about R/S being everything when it comes to reving out is just wrong. It is important, but the actual length of the stroke is just as (or more) important. If you have a very long stroke, you can not wind the motor out without the pistons speeds getting unsafe, no matter how long your rods are. Thats is just an artifact of the basic engine geometry.
Second, there were a bunch of posts about torque, but that is not all that matters. I don't want to get into the millionth tq vs hp debate, but power (the ability to do work) is what moves the car. You can have all the tq in the world, but if it is a narrow range, as it often is in long-stroke motors, you will spend all of your time changing gears. Motors that can wind out may not make the same peak tq but can often make it accross a much broader range (thank you Honda for vairable valve timing) and gearing becomes much easier. The dinky little motor in the nsx does not make a lot of peak tq, but the curve is flat as a table from about 2300 - 7500 rpm. That is very useful in the real world and lets you do some very advantageous things with gearing. Take a look at this dyno of one of my old nsx's with a CT blower. The tq curve is unlike anything you would see in a motor with long-stroke geometry.
The early comment about R/S being everything when it comes to reving out is just wrong. It is important, but the actual length of the stroke is just as (or more) important. If you have a very long stroke, you can not wind the motor out without the pistons speeds getting unsafe, no matter how long your rods are. Thats is just an artifact of the basic engine geometry.
Second, there were a bunch of posts about torque, but that is not all that matters. I don't want to get into the millionth tq vs hp debate, but power (the ability to do work) is what moves the car. You can have all the tq in the world, but if it is a narrow range, as it often is in long-stroke motors, you will spend all of your time changing gears. Motors that can wind out may not make the same peak tq but can often make it accross a much broader range (thank you Honda for vairable valve timing) and gearing becomes much easier. The dinky little motor in the nsx does not make a lot of peak tq, but the curve is flat as a table from about 2300 - 7500 rpm. That is very useful in the real world and lets you do some very advantageous things with gearing. Take a look at this dyno of one of my old nsx's with a CT blower. The tq curve is unlike anything you would see in a motor with long-stroke geometry.
05-04-2007, 01:42 AM
#50
Honda-Tech Member
Re: great but. . . (Top Ramen)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 80884 »</TD></TR><TR><TD CLASS="quote">I would like you to re-think this a little bit, I thought the same until a little schooling. What happens when the VE goes over 100%? That rule would be ok for an inefficient motor but does not work with what were trying to achieve in this post.</TD></TR></TABLE>
i'm just adding fuel to the fire, i'm just about getting to the point of learning of VE. in the netherlands there are not many thougths about engine design in any way. so all my learning has to be done in a foreign language, that's my handicap.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 85 »</TD></TR><TR><TD CLASS="quote">looking my into the thermal dynamics of compressing gas (holing it longer at TDC) i dont think is would make a difference. when you compress a gas, it confines its original heat energy making it hotter in a smaller area but does not continue to heat up after it stops compressing. the only reason i could see a higher R:S would aid in detonation would be due to added heat energy to the combustion chamber from the walls of the chamber (head, piston, sleeves). BUT, higher rpms would give it less time to absorb the heat and in turn help prevent detonation in that way. on the other hand the combustion chamber surfaces would end up being hotter with more fuel burning in less time. lower thermostat temp? </TD></TR></TABLE>
but given the time of detonation, a low R/S ratio engine with an given fuel/cr/point of detonation(in the cycle ofcompressing the gas). the change of possible detonation occuring after ignition is higher then a high R/S ratio engine (i think).
let me try to explain. ignition timing happens somewhat before TDC so the mixture has time to ignite and provides maximum pressure at the desired crankangle in the combustion stroke (you know what i mean). let's say for simplicity, that the timing of the spark is the same. the high R/S ratio engine will have compressed the gas more at time of ignition then the low R/S ratio engine. because at a given crankangle near TDC (point of ingition) the high R/S ratio engines piston will be higher then the low R/S engine.
2 engines with a 100mm stroke.
1 with a 150mm rod
1 with a 300mm rod
at 15 degrees before TDC ("point of ignition") the short rod engine will be 5.6 mm from the top of his stroke and the long rod engine will be 4.5 mm.
get my point? this is without the extra time to let exterior problems heat the mixture
sorry for the long story
i'm just adding fuel to the fire, i'm just about getting to the point of learning of VE. in the netherlands there are not many thougths about engine design in any way. so all my learning has to be done in a foreign language, that's my handicap.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 85 »</TD></TR><TR><TD CLASS="quote">looking my into the thermal dynamics of compressing gas (holing it longer at TDC) i dont think is would make a difference. when you compress a gas, it confines its original heat energy making it hotter in a smaller area but does not continue to heat up after it stops compressing. the only reason i could see a higher R:S would aid in detonation would be due to added heat energy to the combustion chamber from the walls of the chamber (head, piston, sleeves). BUT, higher rpms would give it less time to absorb the heat and in turn help prevent detonation in that way. on the other hand the combustion chamber surfaces would end up being hotter with more fuel burning in less time. lower thermostat temp? </TD></TR></TABLE>
but given the time of detonation, a low R/S ratio engine with an given fuel/cr/point of detonation(in the cycle ofcompressing the gas). the change of possible detonation occuring after ignition is higher then a high R/S ratio engine (i think
).let me try to explain. ignition timing happens somewhat before TDC so the mixture has time to ignite and provides maximum pressure at the desired crankangle in the combustion stroke (you know what i mean). let's say for simplicity, that the timing of the spark is the same. the high R/S ratio engine will have compressed the gas more at time of ignition then the low R/S ratio engine. because at a given crankangle near TDC (point of ingition) the high R/S ratio engines piston will be higher then the low R/S engine.
2 engines with a 100mm stroke.
1 with a 150mm rod
1 with a 300mm rod
at 15 degrees before TDC ("point of ignition") the short rod engine will be 5.6 mm from the top of his stroke and the long rod engine will be 4.5 mm.
get my point? this is without the extra time to let exterior problems heat the mixture
sorry for the long story