Exploring the possibilities with the AMS fully counterweighted crank
08-07-2007, 06:35 PM
#1
Exploring the possibilities with the AMS fully counterweighted crank
Thought I would start a thread here explaining the new rev possibilities for the KA24de using the AMS fully counterweighted crank shaft. Theres seems to be many skeptics that disagree so I am opening up the realm of possibilities.
Many people seem to misconstrue facts and don't realize the difference between the 2 types of crank shafts available. One being only half weighted which is the KA's stock crank, or a fully counterweighted crank usually used for race applications or in any case a higher revving engine.
So to explore these possibilities I am taking the time to do a bit of research on why the crank can perform better under the circumstances of using fully counterweighted over the half weighted.
First so that people get a better understanding I grabbed this pic from Joel at HRT who did a write up a few years back on his KA-t comparing differences between the KA and the SR20 engines. Don't mind any of the literature in the pic as I was exploring the possibilities of knife edging my own crank a little over a year ago.
As you can see the sr20det crank is fully counterweighted, while the KA crank is only truly weighted at it's ends or end axis (halfweighted).
As you can see in comparison to displacement that the main journals of the KA are in fact lager which does add friction which decreases rev to it's displacement already. But due to it's piston bore and longer rod it can help fight a lot of the friction conditions. Which if you look at a lot of large piston, large stroke short rod engines such as the 2.4 litre srt dodge engine it is limited to it's rev from it's massive 101mm stroke, and not small enough piston diameter with much shorter rod combination.
For further explanation I have decided to take a dyno chart of the srt4 so that people can get a better understanding of where it can rev and redline.
Now the srt 4 has a very short power band due to it's large stroke short rod and large piston combination (large piston determined by it's larger than normal 101mm stroke). The srt4 has a 101mm stroke, and a 87.5mm bore piston (2,429 cc, 2.4liter). This means to make it a 2.4 liter in comparison to the KA it uses a much shorter rod, this allows it to have a very large, and linear torque band with a very limiting yet very high peak HP range, the shorter the rod length the more friction that takes place with a much larger bore. The srt 4 for using a fully counterweighted crank can use a much more linear torque band, unlike the KA's halfweighted crank which drops torque after about 4500RPM. The linear torque band, and high HP ouptut would be due to smoother harmonics since the crank works independently of each piston using each set of weights to it's advantage per piston. This allows less stress reducing harmonic chater that can eat up hp and toprque as it does with the KA's half weighted crank.
As another example I have selected the honda/acura K24a in comparison to a 2.4 liter high revving engine. Now the difference between the srt engine and the honda have very different rod stroke ratio's yet the crankshafts are only 2mm in stroking difference!!!!!
The K24a uses a stroke of 99mm, and a 87mm bore(2354cc's, 2.4liter displacement) this means the rod length of the K24a is much longer, and also allows for less friction between strokes. If I had journal diameter numbers I would of like to have that included as that is important information to it's revving capabilities. But as an example here is a dyno graph of the popular high revving K24a.
Now as you can see the longer rod length and slightly smaller crank shaft does the TSX K24a engine some justice, and using the fully counterweighted crank not only does the power band continue to make it passed 7000RPM rev, but the torque band as well is just as linear as the srt4's dyno was. This is proof that smoother harmonic balance can make a much better linear torque band as well as better achievable high HP numbers.
Now you ask can the KA make high rev as the K24a can, and possibly make just as well as a linear torque band as both the SRT, and TSX engines?? The answer is yes, and heres why..
Back in the early 80's nissan developed the FJ24 engine, we can assume to call this the mother of the KA and Lseries since rod stroke ratio's, and cam durations fall very close in comparison, not to mention the FJ was the first of it's engine type to use bucket style lifters as the KA uses today and as the CA18det did as well. Now I don't have any dyno charts of the FJ24, it wasn't a production model engine as the KA is. From referencing the FJ website you can get the majority of the information you need to know that this was the mother of all 2.4 litre engines. This engine for it's day would be much more rev happier than todays GT3 half weighted KA24 engines. The FJ24 would make roughly 277crank HP at 8000RPM, and make roughly 195ft/lb.s of torque at 6200RPM, this was done with 11.1:1 compression. The advantage that todays KA would have over the FJ24 would be it's much larger stroke allowing for a much larger and linear torque band. The FJ24 had a crank stroke of 88mm, and a 92mm bore, in comparison to a high revving engine you can see that to reduce friction with a 92mm bore the FJ as well used a longer rod combination to make up for it's (2340cc) 2.4liter displacement. Here is a picture of the FJ24's crankshaft (courtesy of Gabe Z).
So can the KA be on that competitive edge???? Yes, because if you look at the rod, stroke, and bore ratio's between the K24a, and the FJ24 the KA falls right damn smack in between those 2 ratio's. The K24a with a 99mm stroke and a 87mm piston clearly indicated that it made power into the 7000RPM range, the FJ24 with it's 88mm stroke and it's 92mm bore made power into the 8000RPM range. So what does that mean for KA?? Well if the fully counterweighted crank is weighted well which I don't think AMS has a problem in doing that the KA24de with a 96mm stroke and a 89.5mm bore ( for a rebuild) should in fact make power with this new crank clearly into the 7400RPM range.
So can people speculate that it won't rev that high...Sure theres always skeptics, but basic fundamental engineering states otherwise. Hopefully this will put some of you future engine builders rebuilding the KA24de in the right direction.
Many people seem to misconstrue facts and don't realize the difference between the 2 types of crank shafts available. One being only half weighted which is the KA's stock crank, or a fully counterweighted crank usually used for race applications or in any case a higher revving engine.
So to explore these possibilities I am taking the time to do a bit of research on why the crank can perform better under the circumstances of using fully counterweighted over the half weighted.
First so that people get a better understanding I grabbed this pic from Joel at HRT who did a write up a few years back on his KA-t comparing differences between the KA and the SR20 engines. Don't mind any of the literature in the pic as I was exploring the possibilities of knife edging my own crank a little over a year ago.
As you can see the sr20det crank is fully counterweighted, while the KA crank is only truly weighted at it's ends or end axis (halfweighted).
As you can see in comparison to displacement that the main journals of the KA are in fact lager which does add friction which decreases rev to it's displacement already. But due to it's piston bore and longer rod it can help fight a lot of the friction conditions. Which if you look at a lot of large piston, large stroke short rod engines such as the 2.4 litre srt dodge engine it is limited to it's rev from it's massive 101mm stroke, and not small enough piston diameter with much shorter rod combination.
For further explanation I have decided to take a dyno chart of the srt4 so that people can get a better understanding of where it can rev and redline.
Now the srt 4 has a very short power band due to it's large stroke short rod and large piston combination (large piston determined by it's larger than normal 101mm stroke). The srt4 has a 101mm stroke, and a 87.5mm bore piston (2,429 cc, 2.4liter). This means to make it a 2.4 liter in comparison to the KA it uses a much shorter rod, this allows it to have a very large, and linear torque band with a very limiting yet very high peak HP range, the shorter the rod length the more friction that takes place with a much larger bore. The srt 4 for using a fully counterweighted crank can use a much more linear torque band, unlike the KA's halfweighted crank which drops torque after about 4500RPM. The linear torque band, and high HP ouptut would be due to smoother harmonics since the crank works independently of each piston using each set of weights to it's advantage per piston. This allows less stress reducing harmonic chater that can eat up hp and toprque as it does with the KA's half weighted crank.
As another example I have selected the honda/acura K24a in comparison to a 2.4 liter high revving engine. Now the difference between the srt engine and the honda have very different rod stroke ratio's yet the crankshafts are only 2mm in stroking difference!!!!!
The K24a uses a stroke of 99mm, and a 87mm bore(2354cc's, 2.4liter displacement) this means the rod length of the K24a is much longer, and also allows for less friction between strokes. If I had journal diameter numbers I would of like to have that included as that is important information to it's revving capabilities. But as an example here is a dyno graph of the popular high revving K24a.
Now as you can see the longer rod length and slightly smaller crank shaft does the TSX K24a engine some justice, and using the fully counterweighted crank not only does the power band continue to make it passed 7000RPM rev, but the torque band as well is just as linear as the srt4's dyno was. This is proof that smoother harmonic balance can make a much better linear torque band as well as better achievable high HP numbers.
Now you ask can the KA make high rev as the K24a can, and possibly make just as well as a linear torque band as both the SRT, and TSX engines?? The answer is yes, and heres why..
Back in the early 80's nissan developed the FJ24 engine, we can assume to call this the mother of the KA and Lseries since rod stroke ratio's, and cam durations fall very close in comparison, not to mention the FJ was the first of it's engine type to use bucket style lifters as the KA uses today and as the CA18det did as well. Now I don't have any dyno charts of the FJ24, it wasn't a production model engine as the KA is. From referencing the FJ website you can get the majority of the information you need to know that this was the mother of all 2.4 litre engines. This engine for it's day would be much more rev happier than todays GT3 half weighted KA24 engines. The FJ24 would make roughly 277crank HP at 8000RPM, and make roughly 195ft/lb.s of torque at 6200RPM, this was done with 11.1:1 compression. The advantage that todays KA would have over the FJ24 would be it's much larger stroke allowing for a much larger and linear torque band. The FJ24 had a crank stroke of 88mm, and a 92mm bore, in comparison to a high revving engine you can see that to reduce friction with a 92mm bore the FJ as well used a longer rod combination to make up for it's (2340cc) 2.4liter displacement. Here is a picture of the FJ24's crankshaft (courtesy of Gabe Z).
So can the KA be on that competitive edge???? Yes, because if you look at the rod, stroke, and bore ratio's between the K24a, and the FJ24 the KA falls right damn smack in between those 2 ratio's. The K24a with a 99mm stroke and a 87mm piston clearly indicated that it made power into the 7000RPM range, the FJ24 with it's 88mm stroke and it's 92mm bore made power into the 8000RPM range. So what does that mean for KA?? Well if the fully counterweighted crank is weighted well which I don't think AMS has a problem in doing that the KA24de with a 96mm stroke and a 89.5mm bore ( for a rebuild) should in fact make power with this new crank clearly into the 7400RPM range.
So can people speculate that it won't rev that high...Sure theres always skeptics, but basic fundamental engineering states otherwise. Hopefully this will put some of you future engine builders rebuilding the KA24de in the right direction.
Last edited by BigVinnie; 08-07-2007 at 06:42 PM.
08-08-2007, 06:01 AM
#3
I would of answered that question if I had enough research on the RB26dett which I don't have much information on it.
So after speaking with several people that have done work on the RB26, the reason why it rev's so high with a halfweighted crank is because it has a 73.7mm stroke!!!!!! This means less stress on the crank and less flexing is being applied, the crank itself is almost 1,1/2" shorter in stroke than the KA24de's crank shaft. The crank also weighs less than a fully counterweighted crank which reduces it's MOI's (moment of inertia), allowing the RB26dett crank to be a peppy rev happy crank for being half weighted!! It's a little peewee crank with a long rod and large bore. In fact there are after market fully counterweighted cranks for the RB26dett that claim up to a 9,000RPM rev and redline, these would be JUN stroker kits much larger stroke and the same achievable rev using a fully counterweighted crank, increasing displacement to 2.7liters and still achieving the same rev and redline. Fully counterweighted cranks work!
BTW the RB25det NEO produces more peak torque than the RB26dett, the RB25det neo uses a fully counter weighted crank shaft.
Last edited by BigVinnie; 08-08-2007 at 01:50 PM.
08-12-2007, 09:48 AM
#4
As of 08/11/2007
Spoke with Brian Crower personally at yesterdays Formula Drift @ infinion raceway. He will too be selling a stock stroke (96mm) fully counterweighted crank for $1800. AMS has a deal I wouldn't pass this up.
I also asked Brian if his stroker kit has been dyno tested, his company doesn't even have an engine ready with that kit yet for results. When I asked about the redline of the stroker kit it should redline somewhere to what the srt 4 engine red lines. SRT 4 stroke is 101mm, the KA24de stroker kit would be 102mm stroke. Just some info directly from the source.
Spoke with Brian Crower personally at yesterdays Formula Drift @ infinion raceway. He will too be selling a stock stroke (96mm) fully counterweighted crank for $1800. AMS has a deal I wouldn't pass this up.
I also asked Brian if his stroker kit has been dyno tested, his company doesn't even have an engine ready with that kit yet for results. When I asked about the redline of the stroker kit it should redline somewhere to what the srt 4 engine red lines. SRT 4 stroke is 101mm, the KA24de stroker kit would be 102mm stroke. Just some info directly from the source.
08-12-2007, 11:11 AM
#6
my brother has a SRT4 it redlines around 6500rpm it has alot of power but when i drove it to me the redline just comes up too quick its like i feel like it has more "Go" but i hit the rev limiter i dont like that feels like its powerband is longer but the computer cuts it short lol
08-12-2007, 11:28 AM
#7
i don't doubt or question the possibility of what you have in mind vinnie. the problem i see is not the engine integrity but the possibility that some may see this a safeguard against damage caused but abuse.
too many rev happy honda guys (that i personally know) found themselves dumping too much money into their car only to later have the engine die on them.
too many rev happy honda guys (that i personally know) found themselves dumping too much money into their car only to later have the engine die on them.
08-12-2007, 01:40 PM
#9
i don't doubt or question the possibility of what you have in mind vinnie. the problem i see is not the engine integrity but the possibility that some may see this a safeguard against damage caused but abuse.
too many rev happy honda guys (that i personally know) found themselves dumping too much money into their car only to later have the engine die on them.
too many rev happy honda guys (that i personally know) found themselves dumping too much money into their car only to later have the engine die on them.
I always warrant caution, on anyone who high revs. In most cases Formula D cars can use up to 2 engine swaps for one event.
I've spent years talking to professionals from chatting with Paul St Clair, to Rob at SCAT, an even Brian Crower. Really a fully counterweighted stock stroke crank will make the KA one of the better more powerful high rev engines on the market.
I myself would not take it to 8000RPM extremes, I myself would baby the engine, because I would understand it's limitations in making power. As long as I could get an additional 1000RPM's in peak HP I would be one happy S.O.B...
08-12-2007, 01:48 PM
#10
well vinnie all i can say is keep us posted if this does go through. my car is my daily driver and don't ever rev it past 4k so a fully counterweighted crank is not something that i'd ever buy.
however i am very interested in seeing the results. good luck and sorry to hear what happened with your thread on zilvia.
however i am very interested in seeing the results. good luck and sorry to hear what happened with your thread on zilvia.
08-12-2007, 01:53 PM
#11
All I am bringing about is options to consumers in quality products for the community.
Last edited by BigVinnie; 08-12-2007 at 01:55 PM.
08-13-2007, 10:06 AM
#12
Registered User
Join Date: Sep 2006
Location: Santa Rosa CA
Posts: 33
I had a feeling that I would have seen you if I hung around the BC tent long enough, but my girlfriend wanted to check out the Enjuku chicks.
Is your coupe white? Where you the guy drifting down the dirt road to the exit?
So, to really see a benefit of the new crank we should also upgrade our valvetrain? What kind of gains would you expect without reving past our current redline?
Is your coupe white? Where you the guy drifting down the dirt road to the exit?
So, to really see a benefit of the new crank we should also upgrade our valvetrain? What kind of gains would you expect without reving past our current redline?
08-13-2007, 04:14 PM
#13
I had a feeling that I would have seen you if I hung around the BC tent long enough, but my girlfriend wanted to check out the Enjuku chicks.
Is your coupe white? Where you the guy drifting down the dirt road to the exit?
So, to really see a benefit of the new crank we should also upgrade our valvetrain? What kind of gains would you expect without reving past our current redline?
Is your coupe white? Where you the guy drifting down the dirt road to the exit?
So, to really see a benefit of the new crank we should also upgrade our valvetrain? What kind of gains would you expect without reving past our current redline?
Heres the situation with the valve train.. Better is always better for higher revving conditions. Would you want to trust the stock springs and retainers to do the job?
The KA can handle redline to 7000RPM already as it is with the half weighted crank. So can it make power to 7000 using the fully counterweighted crank? Sure it can.
The KA stock bottom only makes peak power to about 5500RPM then the power begins to drop significantly because of the harmonic stress and possibly what some people say is the cam durations, or there position and placement for overlap preventing power from being made any further. Personally I don't agree and think it's not cam placement at all since the CA16 and CA18det use the similar rod stroke ratio's of the KA24de's as well as similar cam durations and overlap. CA's were very rev happy and made peak power above 6500RPM.
IMO the KA would probably keep the HP it makes already as the stock crank would, and with the new limitations with harmonics, and less stress to the bottom end we could quite possibly see over 200WHP street legal NA KA's with nothing but bolt on's with minor ignition timing, and SAFC tuning.
The valve train would only help to extend redline further which if the crank is balanced correctly it could continue to make power through redline as the F20c honda engines do.
