rpm vs. displacement
08-28-2005, 07:07 PM
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rpm vs. displacement
i tryed searching. i was reading my d sport mag and they built a b16 to rev to 10+ and put 18 pounds of boost on it and made 480 horse and 270 lbs. of torque. so is it better to build a gsr or ls and only spin to 8-8500 or is there some truth to smaller displacment and spinning higher?
08-28-2005, 07:13 PM
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Re: rpm vs. displacement (sloweredcivic)
gnerally the bigger the displacement the larger the stroke = high mean piston speed = lower rev limit.
mean piston speed should really dictate where the rev limit is set. so what if your setup could still make power, would you rather have a motor that runs or one pull to 5 digit rpm's that results in a destroyed bottom end
mean piston speed should really dictate where the rev limit is set. so what if your setup could still make power, would you rather have a motor that runs or one pull to 5 digit rpm's that results in a destroyed bottom end
08-28-2005, 07:17 PM
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i was assuming the b16 bottom end was built (sleeves rods pistons and bearings with high rpm in mind) as well as the top end springs reatins ...
08-28-2005, 07:18 PM
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Re: (sloweredcivic)
yes, but the mean piston speed on the b16 is very low because of the small stroke. try to turn 10k with an ls or gsr bottom end and watch it exceed 5000fps (feet per second) at that point **** starts to break (pistons, rods, etc) built or not
08-28-2005, 07:27 PM
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Re: rpm vs. displacement (sloweredcivic)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sloweredcivic »</TD></TR><TR><TD CLASS="quote">i tryed searching. i was reading my d sport mag and they built a b16 to rev to 10+ and put 18 pounds of boost on it and made 480 horse and 270 lbs. of torque. so is it better to build a gsr or ls and only spin to 8-8500 or is there some truth to smaller displacment and spinning higher?</TD></TR></TABLE>
The lower reving gsr/ls will make more torque and live longer even though the piston speed will be similar.
Glenn
The lower reving gsr/ls will make more torque and live longer even though the piston speed will be similar.
Glenn
08-28-2005, 07:33 PM
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Re: rpm vs. displacement (NJIN BUILDR)
i realize that read my original post i want to know if wrapping the engine higher has a advantage over more displacement and lower rpm
08-28-2005, 07:49 PM
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Re: rpm vs. displacement (sloweredcivic)
well, not really. the bigger motor has the ability to make more power and torque at a lower rpm therefore it will be more reliable and wont stress the internals as bad... a civic turning to 10k is a timebomb waiting to go off
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08-28-2005, 08:22 PM
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Re: rpm vs. displacement (wantboost)
i have a 2.0l ls/vtec built revin to 9800 making power to redline at 20psi. if it built rev it to where it stops making power. it all comes down to what you want to do though
08-28-2005, 08:25 PM
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Re: rpm vs. displacement (vaporboy12)
just because it makes power to redline doesnt mean ****.
mean piston speed (how fast the piston travels up and down in the bore) is what determines where to stop turning the motor, at that rev limit you are well over 5000fps and in danger or a catastrophic failure... of course i will be turning my motor to 10k but no t that often, mostly on the dyno
mean piston speed (how fast the piston travels up and down in the bore) is what determines where to stop turning the motor, at that rev limit you are well over 5000fps and in danger or a catastrophic failure... of course i will be turning my motor to 10k but no t that often, mostly on the dyno
08-28-2005, 08:40 PM
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Re: (wantboost)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by wantboost »</TD></TR><TR><TD CLASS="quote">yes, but the mean piston speed on the b16 is very low because of the small stroke. try to turn 10k with an ls or gsr bottom end and watch it exceed 5000fps (feet per second) at that point **** starts to break (pistons, rods, etc) built or not</TD></TR></TABLE>
The biggest thing that keeps people from turning 10K++ RPM's is not the strength of the bottom end, but rather the timing. The amount that dizzys are off when you're turning modest RPM's isn't a big problem, but start turning your motor 11K RPM's and that small misque at 6000 becomes a big problem. A good set of rods (pauter, cunningham, crower, etc) with a balanced bottom end is no problem for a modest 3.4-3.5 inch stroke like the LS/GSR's have.
The biggest thing that keeps people from turning 10K++ RPM's is not the strength of the bottom end, but rather the timing. The amount that dizzys are off when you're turning modest RPM's isn't a big problem, but start turning your motor 11K RPM's and that small misque at 6000 becomes a big problem. A good set of rods (pauter, cunningham, crower, etc) with a balanced bottom end is no problem for a modest 3.4-3.5 inch stroke like the LS/GSR's have.
08-29-2005, 03:14 AM
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Re: rpm vs. displacement (wantboost)
Where you got the 5000 feet per second figure from escapes me completely. An LS with stock stroke at 10,000rpm almost scrapes 100fps (97fps).
08-29-2005, 08:25 AM
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Re: rpm vs. displacement (string)
you are doing your math completely wrong
a motor with an 89mm stroke turning 10k has a mean piston speed of 5,833.33 feet per second
a motor with an 89mm stroke turning 10k has a mean piston speed of 5,833.33 feet per second
08-29-2005, 09:26 AM
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Re: rpm vs. displacement (wantboost)
http://www.csgnetwork.com/pistonspeedcalc.html
Wantboost, you are wrong. You are calculating fpm yet you use the units of fps.
As for the topic:
HP=tq*rpm/5252
So if you have a low torque number based on the fact you have a low stroke and low displacement, in order to make power you need to rev higher. Higher torque based on larger stroke and displacment, you can rev lower and make the same power. It all depends on the engine dynamics and the application. You want the optimal power between shift points regardless of what racing. On a road course this would mean a very broad powerband because you can find yourself shifting and coming out of a corner at low rpms or on the drag strip where you want to make a bulk of your power at the top end and need a minimal powerband.
Wantboost, you are wrong. You are calculating fpm yet you use the units of fps.
As for the topic:
HP=tq*rpm/5252
So if you have a low torque number based on the fact you have a low stroke and low displacement, in order to make power you need to rev higher. Higher torque based on larger stroke and displacment, you can rev lower and make the same power. It all depends on the engine dynamics and the application. You want the optimal power between shift points regardless of what racing. On a road course this would mean a very broad powerband because you can find yourself shifting and coming out of a corner at low rpms or on the drag strip where you want to make a bulk of your power at the top end and need a minimal powerband.
08-29-2005, 12:30 PM
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Re: rpm vs. displacement (non-VTEC)
lol, damn the little conversions. yea i see what i did wrong. i meant to say fpm (the bigger number) all along. oh well, i guess you guys get the point now, lol
08-29-2005, 09:26 PM
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well i was thinking that this would give a lot of top end and i wouldn't have to fight for traction so much through 1st and 2nd with my ys1 tranny
08-29-2005, 11:42 PM
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Re: rpm vs. displacement (wantboost)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by wantboost »</TD></TR><TR><TD CLASS="quote">well, not really. the bigger motor has the ability to make more power and torque at a lower rpm therefore it will be more reliable and wont stress the internals as bad... a civic turning to 10k is a timebomb waiting to go off
</TD></TR></TABLE>
Well a b18c with an 87.2mm stroke @ 9k will have around the same mean piston speed as a b16 with a 77.4mm stroke @ 10k. so if what you are saying is correct... a b18 turning to 9k is also a timebomb waiting to go off?
I guess the b18 would only be more "reliable and wont stress the internals as bad" IF it were to only spin to 8k, but who doesnt take their b18 to 9k these days?
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sloweredcivic »</TD></TR><TR><TD CLASS="quote">so is it better to build a gsr or ls and only spin to 8-8500 or is there some truth to smaller displacment and spinning higher?</TD></TR></TABLE>
im not sure if there is any "truth" to smaller displacement and spinning higher, but a 10k redline is pretty fun if you ask me
</TD></TR></TABLE>
Well a b18c with an 87.2mm stroke @ 9k will have around the same mean piston speed as a b16 with a 77.4mm stroke @ 10k. so if what you are saying is correct... a b18 turning to 9k is also a timebomb waiting to go off?
I guess the b18 would only be more "reliable and wont stress the internals as bad" IF it were to only spin to 8k, but who doesnt take their b18 to 9k these days?
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sloweredcivic »</TD></TR><TR><TD CLASS="quote">so is it better to build a gsr or ls and only spin to 8-8500 or is there some truth to smaller displacment and spinning higher?</TD></TR></TABLE>
im not sure if there is any "truth" to smaller displacement and spinning higher, but a 10k redline is pretty fun if you ask me
08-30-2005, 07:32 AM
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08-30-2005, 08:30 AM
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Re: rpm vs. displacement (wantboost)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by wantboost »</TD></TR><TR><TD CLASS="quote">a few hundred fpm can mean the difference between having a motor and not having a motor anymore</TD></TR></TABLE>
b16 (77.4mm stroke) @ 10,000rpm has a mean piston speed of 5079 fpm.
b18c (87.2mm stroke) @ 9,000rpm has a mean piston speed of 5150 fpm.
a b16 @ 10k seems safe enough for me.
b16 (77.4mm stroke) @ 10,000rpm has a mean piston speed of 5079 fpm.
b18c (87.2mm stroke) @ 9,000rpm has a mean piston speed of 5150 fpm.
a b16 @ 10k seems safe enough for me.
08-30-2005, 09:12 AM
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Re: rpm vs. displacement (STD ONEpointSIX)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by STD ONEpointSIX »</TD></TR><TR><TD CLASS="quote">
b16 (77.4mm stroke) @ 10,000rpm has a mean piston speed of 5079 fpm.
b18c (87.2mm stroke) @ 9,000rpm has a mean piston speed of 5150 fpm.
a b16 @ 10k seems safe enough for me.</TD></TR></TABLE>
There's nothing outrageous about a B18C or B18B at 10K RPM's either. Corvette Z06 motors have a 7200 fuel shutoff from the factory, we're talking about a factory motor designed for atleast some longevity that sees 4800 FPM of piston speed.
b16 (77.4mm stroke) @ 10,000rpm has a mean piston speed of 5079 fpm.
b18c (87.2mm stroke) @ 9,000rpm has a mean piston speed of 5150 fpm.
a b16 @ 10k seems safe enough for me.</TD></TR></TABLE>
There's nothing outrageous about a B18C or B18B at 10K RPM's either. Corvette Z06 motors have a 7200 fuel shutoff from the factory, we're talking about a factory motor designed for atleast some longevity that sees 4800 FPM of piston speed.
08-30-2005, 09:58 AM
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Re: rpm vs. displacement (DarkKnight1)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DarkKnight1 »</TD></TR><TR><TD CLASS="quote">want to really get crazy?
H22 90.7mm stroke @ 9,000rpm = 5,356 fpm
</TD></TR></TABLE>
H22 90.7mm stroke @ 9,000rpm = 5,356 fpm
</TD></TR></TABLE>
08-30-2005, 10:48 AM
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Re: (sloweredcivic)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sloweredcivic »</TD></TR><TR><TD CLASS="quote">so it could be just as beneficial to pick up a b16 block dirt cheap sleeve it a rev it to 10k</TD></TR></TABLE>
Well you also have to look @ powerband as well as other things. It's not as simple as rpm vs. displacement.
Well you also have to look @ powerband as well as other things. It's not as simple as rpm vs. displacement.
08-30-2005, 10:49 AM
#25
Re: (sloweredcivic)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sloweredcivic »</TD></TR><TR><TD CLASS="quote">so it could be just as beneficial to pick up a b16 block dirt cheap sleeve it a rev it to 10k</TD></TR></TABLE>
No.
Torque, Quicker spool > Less torque, slower spool
You're still going to have traction problems no matter how you make the power if you're making 400+ WHP in a FWD honda. You might as well get as quick of spool as you can so that when you run it on lower boost it doesn't feel like a dog till 7000.
No.
Torque, Quicker spool > Less torque, slower spool
You're still going to have traction problems no matter how you make the power if you're making 400+ WHP in a FWD honda. You might as well get as quick of spool as you can so that when you run it on lower boost it doesn't feel like a dog till 7000.