Rod / Stroke Ratio ?????
12-29-2003, 01:32 PM
#101
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Re: (-KangaRod-)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by -KangaRod- »</TD></TR><TR><TD CLASS="quote">stroked and bored B16 (86X89) with a GsR head and extremly low r/r (around 1.45:1)</TD></TR></TABLE>
Why would it be that low?
Ive seen stroked B16's ranging from 1.51-1.58. You can use the LS or GSR rods with the LS or GSR crank along with a custom piston. You can alos us B16 rods and a custom piston for either but with the GSR crank the B16 rods need to be shimmed down a bit on the big end t fit the narow P72 rod journals.
Why would it be that low?
Ive seen stroked B16's ranging from 1.51-1.58. You can use the LS or GSR rods with the LS or GSR crank along with a custom piston. You can alos us B16 rods and a custom piston for either but with the GSR crank the B16 rods need to be shimmed down a bit on the big end t fit the narow P72 rod journals.
12-29-2003, 01:53 PM
#102
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o.k. kangarod this 2 fast2furious gen ****,
who are you implying that to.and the "quote 2fast2furious did not drag race.THEY STREET RACED".
well in drag racing r/r don't mean ****,say you build a motor with a r/r of 1.41.you drive it everyday and you will be lucky to get 20k out it.because it is going to be digging into the side of your cylinder wall,putting more wear on one side than it would the other.but in DRAG RACING that motor will last a while,or untill it comes apart.
in the last couple of posts you have made,you have simply stated efficiency,not you building a drag racing motor.
like i said in my previous posts.i took a h22 added a 3/4 deck plate and a massive custom stroke and the r/r is 1.64,not only do i have a **** load of tq out of the hole,but i also have it to keep on top end with the r/r being the way it is.the total displacement is almost 2.6 liters.
what is wrong with having something like that to drag race and for "EFFICIENCY".
who are you implying that to.and the "quote 2fast2furious did not drag race.THEY STREET RACED".
well in drag racing r/r don't mean ****,say you build a motor with a r/r of 1.41.you drive it everyday and you will be lucky to get 20k out it.because it is going to be digging into the side of your cylinder wall,putting more wear on one side than it would the other.but in DRAG RACING that motor will last a while,or untill it comes apart.
in the last couple of posts you have made,you have simply stated efficiency,not you building a drag racing motor.
like i said in my previous posts.i took a h22 added a 3/4 deck plate and a massive custom stroke and the r/r is 1.64,not only do i have a **** load of tq out of the hole,but i also have it to keep on top end with the r/r being the way it is.the total displacement is almost 2.6 liters.
what is wrong with having something like that to drag race and for "EFFICIENCY".
12-29-2003, 01:56 PM
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Re: (1700anddroping)
If I have such a low rod stroke it will help me bust out of the hole. Plus I can't easily fit an H22 into a EF crx. A b16 with an LS tranny would be nice though....
I'd probably want to start off with something smaller than 86 mm though. Possibly something around 85 mm, so I can hone over for a cupple winters. I'll need new pistons every time though. crud lick. Realistically though - would 50,000 km's be out of the question for a r/r ratio as low as 1.44:1?
I'd probably want to start off with something smaller than 86 mm though. Possibly something around 85 mm, so I can hone over for a cupple winters. I'll need new pistons every time though. crud lick. Realistically though - would 50,000 km's be out of the question for a r/r ratio as low as 1.44:1?
12-29-2003, 02:19 PM
#104
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like i said before that r/r 1.45 for drag racing will last a while,because you are not driving it everyday,plus you are only driving it a quater mile at a time.it just depends on how it is put together.
12-29-2003, 02:35 PM
#106
Senior Member
you could drive it everyday but it's not going to last very long.you'll either have to do 2 things,when it first starts smoking,break it down and change the rings,if not,you will more than likely have to bore it,because it will egg shape the cylinder walls.you could off set the wrist pin that would take some of the pressure off don't know how much.but it would help a little.
12-29-2003, 10:03 PM
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1700 and kanga -
I would like to hear how a lower than 1.75 R/S ratio, causing much more cumbustion energy to be used to push on the sleeves, is a bennifit to lower rpm engines. And lets try to get something a touch more involved then the clasic intake velocity argument that is a clasic and simply dispelled by lower lift on the cam, or a narrowing of ports with putty.
I supose my first question is this. Engines used to generate power in the form of electricity. They burn natural gas. They have development budgets often in the many many million $ of budget area. They also run in the very very low side of engine speeds, around 500-1000 max rpm. They have found over YEARS of development that the R/S ratio of 1.75/1 has given them the highest power outputs for there application.
I think many of you find the choice of R/S to be only relivant as a function of wear on the engine, this could not be more false. It effects the dwell points in a drastic manor causing large effects on burn/position timing, as well as the ablility to acheive VE's over that of 100%. This effects many deep charactoristics of an engine.
I would like to hear the voices of engine designers/engineers on this topic. I dont not say "engine builders" because too often they are folks who follow a pattern of putting together nuts and bolts from a forumla copied by someone who had luck with a setup. There is something to be said for status-quo functionality, but i have little respect of the insight of "engine builders" who simply assemble parts.
unloose the everpresent cannons cannons of HT.
-Luke
I would like to hear how a lower than 1.75 R/S ratio, causing much more cumbustion energy to be used to push on the sleeves, is a bennifit to lower rpm engines. And lets try to get something a touch more involved then the clasic intake velocity argument that is a clasic and simply dispelled by lower lift on the cam, or a narrowing of ports with putty.
I supose my first question is this. Engines used to generate power in the form of electricity. They burn natural gas. They have development budgets often in the many many million $ of budget area. They also run in the very very low side of engine speeds, around 500-1000 max rpm. They have found over YEARS of development that the R/S ratio of 1.75/1 has given them the highest power outputs for there application.
I think many of you find the choice of R/S to be only relivant as a function of wear on the engine, this could not be more false. It effects the dwell points in a drastic manor causing large effects on burn/position timing, as well as the ablility to acheive VE's over that of 100%. This effects many deep charactoristics of an engine.
I would like to hear the voices of engine designers/engineers on this topic. I dont not say "engine builders" because too often they are folks who follow a pattern of putting together nuts and bolts from a forumla copied by someone who had luck with a setup. There is something to be said for status-quo functionality, but i have little respect of the insight of "engine builders" who simply assemble parts.
unloose the everpresent cannons cannons of HT.
-Luke
12-30-2003, 05:01 AM
#108
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Re: (liveforphysics)
but you can't argue with more stroke in a shorter deck....
By stating that their is millions into the electric burner field you are impling that there isn't billions put into the car engine field. This is more appopriate discussion since we are not powering our cars by natural gas. The intake velocities that would benefit each setup will be totally different, as well as all the geometry that will benefit each setup accordingly.
I ask again if what you state is true - then why do people continue to R & D motors with different r/r than 1.75:1?
By stating that their is millions into the electric burner field you are impling that there isn't billions put into the car engine field. This is more appopriate discussion since we are not powering our cars by natural gas. The intake velocities that would benefit each setup will be totally different, as well as all the geometry that will benefit each setup accordingly.
I ask again if what you state is true - then why do people continue to R & D motors with different r/r than 1.75:1?
12-30-2003, 05:56 AM
#109
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Re: (liveforphysics)
here is the #1 reason which auto manfacturers typically use different r/s engines in passenger vehicles: Package Height; to get engines of different displacements, rpm, uses, etc. to fit under the hoods of their vehicles. (true, the chassis, etc. is designed partially around the engine/drivetrain and not entirely vice-versa, but... .)
another thing which many people overlook is that while 1.75 r/s will yield the best leverage on the crank vs. the geometric detriments of lower r/s ratios (friction from sideloading), (regardless of package height) try putting a big deckplate on a stock block, using a good r/s ratio, and making good power with a stock head casting which was designed for a 1.6-1.8L engine at a specific rpm band; build a 2.3+ L B block and see what happens; while the good r/s ratio will reduce sideloading and yield slower piston acceleration, and the longer stroke will produce better torque throughout the low/midrange, at higher rpm the engine will starve for air, since the piston speed will still exceed that of the lower displacement (stock) engine at a given rpm, and the head won't allow for proper cylinder filling. true, you won't need to rev as high to pull hard, but you'll have spent exponentially more $, and with the right gearing, a lower displacement engine may still beat you.
another concern is that while friction from sideloading is especially bad, friction is also increased with piston speed, which at any given rpm is higher with a longer stroke than in an engine with a shorter stroke.
here is the benefit of the DOHC VTEC engine from a design perspective: relatively low displacement and a small package with excellent efficiency/power. the b16a was the first common production engine for a passenger car to reach 100hp (crank) per litre. it's small and gets excellent fuel economy. based on this design, it is possible to make a 2L like SGT's or Omniman's (using mostly stock parts) which gets similar fuel economy and better power, though even in the more cost-efficient (latter) example, it might not pass smog checks, and it's tuned for people who don't do stupid things like accidentally (or intentionally) run low octane fuel to save $1, then run it WOT in immediately after a cold start etc.. these are a few of the conditions which manufacturers have to consider.
another thing which many people overlook is that while 1.75 r/s will yield the best leverage on the crank vs. the geometric detriments of lower r/s ratios (friction from sideloading), (regardless of package height) try putting a big deckplate on a stock block, using a good r/s ratio, and making good power with a stock head casting which was designed for a 1.6-1.8L engine at a specific rpm band; build a 2.3+ L B block and see what happens; while the good r/s ratio will reduce sideloading and yield slower piston acceleration, and the longer stroke will produce better torque throughout the low/midrange, at higher rpm the engine will starve for air, since the piston speed will still exceed that of the lower displacement (stock) engine at a given rpm, and the head won't allow for proper cylinder filling. true, you won't need to rev as high to pull hard, but you'll have spent exponentially more $, and with the right gearing, a lower displacement engine may still beat you.
another concern is that while friction from sideloading is especially bad, friction is also increased with piston speed, which at any given rpm is higher with a longer stroke than in an engine with a shorter stroke.
here is the benefit of the DOHC VTEC engine from a design perspective: relatively low displacement and a small package with excellent efficiency/power. the b16a was the first common production engine for a passenger car to reach 100hp (crank) per litre. it's small and gets excellent fuel economy. based on this design, it is possible to make a 2L like SGT's or Omniman's (using mostly stock parts) which gets similar fuel economy and better power, though even in the more cost-efficient (latter) example, it might not pass smog checks, and it's tuned for people who don't do stupid things like accidentally (or intentionally) run low octane fuel to save $1, then run it WOT in immediately after a cold start etc.. these are a few of the conditions which manufacturers have to consider.
12-30-2003, 06:26 PM
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Re: (-KangaRod-)
__
__
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As you can clearly see, the total difference (or displacement) doesn't change if you alter the length of the connecting rod (by changing the length of the rod and keeping the stroke
the same we will alter the rod:stroke ratio), however, at 90 degrees something intresting happens. The shorter rod has moved more. Since the amount of power you make is totally
dependant upon how hard your motor will pull air through (for arguments sake) the one with the shorter rod will pull the air in harder (all else being the same), and will be contained
in a smaller package (look at how much bigger the red picture is). There needs to be a happy medium however, if the rod gets too short, too much of the force will be pushing left or right, instead of down (where we want it to go) and can warp the cylinder walls. This risk of long term damage increases exponentially with RPM (and was the source of the LsVtec and B20Vtec conspiracy of the last three years). Since the shorter rod pulls so much harder on the air in the intake manifold, and pulls so much more air through, the only way to allow the longer rod to compete is to increase the air velocity by forcing it through a smaller hole (smaller port size than the short rod). Changing valve and port sizes is not a very practical method of going about building our motors - and for the most part, actually defeats the purpose of building a motor (after all - more air, more fuel, more power!), but running a milder cam is a lot more practical than running a smaller valve and can serve close to the same purpose. That is why most people make more power with a stage one or a type r cam on a B16. They need a lot more RPM before they see the gains that the 1.8 crowd sees from the stage B+ larger cams. Dwell time is the time that the piston is hanging around near the top (longer = good for high rpm, shorter = good for just about everywhere else), piston speed is the instantanious measurment of how fast the piston is going at an exact moment ( piston speed=(.166)(stroke)(rpm) ), where as piston acceleration is the measurment of the change in piston speed over a given time (Piston acceleration=[(rpm^2)/(2189)][1+1/{(2)(ratio)}] ).
There are also other benefits to a lower rod:stroke - this include a wider powerband and increased throttle responce. Don't be fooled - R/R is very important - but Honda's not dumb, they wouldn't sell an engine with an terribly low Rod: Stroke ratio. R/R is measured as a ratio of the connecting rod length versus the stroke length. Some of the more common motors:
D15B2 - 1.59:1
D16A1/A6 - 1.52:1
B16A - 1.74:1
B17A1 - 1.68:1
B18A/B - 1.54:1
B18C - 1.58:1
B20B/Z - 1.54:1
H22A - 1.58:1
If anyone has the Rod: Stroke ratios for any other motors (K20, F20C, C30, C32) let me know. I'd like to post them here aswell.
You can find out more about Rod: Stroke ratios and its affects on internal geometry here:
http://m24x.zeroforum.com/zerothread?id=138
Modified by -KangaRod- at 8:18 PM 1/8/2004
01-02-2004, 07:46 AM
#112
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Re: Rod / Stroke Ratio ????? (Screamer)
BEST LINE EVER!!! "reliable, cheap & fast - Pick One"
We used to say pick two at the bike shop. Oh well, guess we just have that southern hospitallity.
We used to say pick two at the bike shop. Oh well, guess we just have that southern hospitallity.
01-03-2004, 02:18 AM
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1700 and kanga -
I would like to hear how a lower than 1.75 R/S ratio, causing much more cumbustion energy to be used to push on the sleeves, is a bennifit to lower rpm engines. And lets try to get something a touch more involved then the clasic intake velocity argument that is a clasic and simply dispelled by lower lift on the cam, or a narrowing of ports with putty.
I supose my first question is this. Engines used to generate power in the form of electricity. They burn natural gas. They have development budgets often in the many many million $ of budget area. They also run in the very very low side of engine speeds, around 500-1000 max rpm. They have found over YEARS of development that the R/S ratio of 1.75/1 has given them the highest power outputs for there application.
I think many of you find the choice of R/S to be only relivant as a function of wear on the engine, this could not be more false. It effects the dwell points in a drastic manor causing large effects on burn/position timing, as well as the ablility to acheive VE's over that of 100%. This effects many deep charactoristics of an engine.
I would like to hear the voices of engine designers/engineers on this topic. I dont not say "engine builders" because too often they are folks who follow a pattern of putting together nuts and bolts from a forumla copied by someone who had luck with a setup. There is something to be said for status-quo functionality, but i have little respect of the insight of "engine builders" who simply assemble parts.
unloose the everpresent cannons cannons of HT.
-Luke
I would like to hear how a lower than 1.75 R/S ratio, causing much more cumbustion energy to be used to push on the sleeves, is a bennifit to lower rpm engines. And lets try to get something a touch more involved then the clasic intake velocity argument that is a clasic and simply dispelled by lower lift on the cam, or a narrowing of ports with putty.
I supose my first question is this. Engines used to generate power in the form of electricity. They burn natural gas. They have development budgets often in the many many million $ of budget area. They also run in the very very low side of engine speeds, around 500-1000 max rpm. They have found over YEARS of development that the R/S ratio of 1.75/1 has given them the highest power outputs for there application.
I think many of you find the choice of R/S to be only relivant as a function of wear on the engine, this could not be more false. It effects the dwell points in a drastic manor causing large effects on burn/position timing, as well as the ablility to acheive VE's over that of 100%. This effects many deep charactoristics of an engine.
I would like to hear the voices of engine designers/engineers on this topic. I dont not say "engine builders" because too often they are folks who follow a pattern of putting together nuts and bolts from a forumla copied by someone who had luck with a setup. There is something to be said for status-quo functionality, but i have little respect of the insight of "engine builders" who simply assemble parts.
unloose the everpresent cannons cannons of HT.
-Luke
01-14-2004, 07:39 AM
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I am not saying there is not advantages, their clearly is, but untill you explain to me how this perfect geometry is so perfect it is going to make 10% more power at almost all rpm's (because of the additional displacement), than the lower Rod:stroke will be better. Perhaps the fact that these natural gas motors are burning an entirly different type of fuel (which my instinct is telling me is a much slower burn), or maybe the fact that they arn't varing their rpm's as much (and are under more constant load) has something to do with it? If your argument is correct than clearly every car on the market should be sold with a 1.75 rod:stroke ratio on the market, yet it is not? How do you explain that one?
-edit-
you are looking at this from an engineering standpoint, wait untill your are told the block needs to be 'this' high and needs to make ____ amount of power, and needs to be this efficient etc and you will quickly realize that your 100mm x 56 mm motor with a 1.75 rod:stroke ratio will not fit in the engine bay. Not only that, but it will get horrible fuel mileage, and will lack the torque to allow even the most skilled of drivers comfortable daily driving. Nevermind the emissions the car will make. The transmission will have to be so close that you will shift 4 times before you've even reached highway speeds. The clutch will wear much sooner, the list goes on.
The fact remains that engineers around the world (the exact same people you just called out, yet maybe arn't on this board) continue to design motors with rod:strokes in the 1.6:1 area. Are you saying they don't know what they are doing?
Ask any prof and they will tell you the first rule of engineering is forget everything they've taught you, cause in the field it doesn't mean anything.
Modified by -KangaRod- at 10:50 AM 1/14/2004
-edit-
you are looking at this from an engineering standpoint, wait untill your are told the block needs to be 'this' high and needs to make ____ amount of power, and needs to be this efficient etc and you will quickly realize that your 100mm x 56 mm motor with a 1.75 rod:stroke ratio will not fit in the engine bay. Not only that, but it will get horrible fuel mileage, and will lack the torque to allow even the most skilled of drivers comfortable daily driving. Nevermind the emissions the car will make. The transmission will have to be so close that you will shift 4 times before you've even reached highway speeds. The clutch will wear much sooner, the list goes on.
The fact remains that engineers around the world (the exact same people you just called out, yet maybe arn't on this board) continue to design motors with rod:strokes in the 1.6:1 area. Are you saying they don't know what they are doing?
Ask any prof and they will tell you the first rule of engineering is forget everything they've taught you, cause in the field it doesn't mean anything.
Modified by -KangaRod- at 10:50 AM 1/14/2004
01-14-2004, 09:19 AM
#116
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Re: (-KangaRod-)
Goodness, you guys sure talk alot. Have you guys actually tried any of this knowledge to make a more powerful reliable engine....
What I did was use a 89mm crank in a stock height B18 engine, moved the piston pin hieght higher, allowing me to use higher compression pistons, as well as longer rods. Allowing me a more optimum R/S for my application. Which was a flatter more usable power curve.
A longer rod reduces the maximum rod angle to the cylinder bore centerline. Less rod angle will reduce piston side loading; there will be less friction and less bore wear. Less rod angle also gives better average leverage on the crank for a longer period of time.
A higher pin height will reduce piston rock and aid ring seal. Please do not email me arguing anything about a tighter ring pack, I am talking about pin height and pin height only. Moving the pin closer the the center of gravity of the pistons makes the piston more stable.
A longer rod decelerates toward TDC and accelerates away from TDC slower than a shorter rod, so piston-to-valve clearances are tighter with a longer rod. This may require deeper valve relief's in the piston (but probably not). A short rod is just the opposite, there is more clearance because the piston decelerates toward and accelerated away for TDC faster.
Due to the fact that the longer rod moves past TDC slower, it gives the charge a longer time to burn. So you need less timing for peak power. Using less timing also reduces the chance of detonation; so higher compression ratios can be used.
What I did was use a 89mm crank in a stock height B18 engine, moved the piston pin hieght higher, allowing me to use higher compression pistons, as well as longer rods. Allowing me a more optimum R/S for my application. Which was a flatter more usable power curve.
A longer rod reduces the maximum rod angle to the cylinder bore centerline. Less rod angle will reduce piston side loading; there will be less friction and less bore wear. Less rod angle also gives better average leverage on the crank for a longer period of time.
A higher pin height will reduce piston rock and aid ring seal. Please do not email me arguing anything about a tighter ring pack, I am talking about pin height and pin height only. Moving the pin closer the the center of gravity of the pistons makes the piston more stable.
A longer rod decelerates toward TDC and accelerates away from TDC slower than a shorter rod, so piston-to-valve clearances are tighter with a longer rod. This may require deeper valve relief's in the piston (but probably not). A short rod is just the opposite, there is more clearance because the piston decelerates toward and accelerated away for TDC faster.
Due to the fact that the longer rod moves past TDC slower, it gives the charge a longer time to burn. So you need less timing for peak power. Using less timing also reduces the chance of detonation; so higher compression ratios can be used.
02-14-2004, 09:34 PM
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Re: (Christian)
really good thread.
i usually hang in the FI forum but this is good information for me as well. I am glad to see this discussion going in a mature fashion without senseless/immature trolling
Mark
PS Christian nice copy and paste. go to http://www.grapeaperacing.com/...h.cfm
for the complete writeup
Modified by psileepR at 10:48 PM 2/14/2004
i usually hang in the FI forum but this is good information for me as well. I am glad to see this discussion going in a mature fashion without senseless/immature trolling
Mark
PS Christian nice copy and paste. go to http://www.grapeaperacing.com/...h.cfm
for the complete writeup
Modified by psileepR at 10:48 PM 2/14/2004
05-06-2004, 06:14 AM
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Re: (Christian)
Question....directed towards Omniman or Christian..
Choice: 1.75 rod ratio vs. 2.0. Your thoughts on drawbacks vs. benefits...
Cam profiles? Rod weights? Infinite deck height.
Choice: 1.75 rod ratio vs. 2.0. Your thoughts on drawbacks vs. benefits...
Cam profiles? Rod weights? Infinite deck height.
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