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I am probably the worst one to ask, but here is for the answer to your question;
I bought the "C6M" Cams and springs a couple of weeks ago.
The springs are single springs. I spoke to JWT and the only information was that they are designed to be used stand alone and are good to 8,000rpm, do not use the OEM inner spring I was told.
Do not know, could not find out, the spring rates or spring seat pressures.
Without having it in front of me right now, I would think that the springs are quite strong (high rate, linear wound) and have a higher seat pressure than the OEMs and the dual valve spring sets from other manufacturers. This is the only way I can see them coping with 8,000rpm without developing crazy harmonics.
Most of the other dual spring systems are designed as such to give sufficient intermediate load but not unduly load the valve seats and valve stem when closed.
I would not use these springs without the titanium valve retainers because of this. The weight saving will reduce the inertia loads of the valve assembly and assist with reducing valve bounce loads if you float the valve train.
I plan on running the "C6Ms" with my TOMEI dual valve springs, along with CROWER titanium retainers (none in stock at JWT when I bought the stuff), which I know are good for 8,500rpm.
o.k. I asked them the same and they say me the springs are singles and work fine with C series. Also they donīt have titanium retanires and say I can use OEM retainers. But I believe the C6M work 9000 r.p.m. Did you ask JWT how many H:P. can you obtain with C6M cams?
Here is the deal. JWT claim the cams are good for up to 9000rpm. They also say the springs are only good to 8000rpm. Sounds like a mismatch to me, but if you read the threads "JWT C6M" thread in the All Motor Forum you can get some more information.
Anyway, please let's just have that go dead.
JWT say the cams can support around 220whp. I think it much depends on the setup. I am hoping these cams can allow the engine to develop somewhere around 220 to 230.
Again, I reccomend the titanium retainers if you use those springs with the C Series Cams. CROWER have them for $180something, in stock.
If you like take a look at the "How much power from quad throttle bodies" there ae some photos of my motor in my B12 race car.
I am probably the worst one to ask, but here is for the answer to your question;
I bought the "C6M" Cams and springs a couple of weeks ago.
The springs are single springs. I spoke to JWT and the only information was that they are designed to be used stand alone and are good to 8,000rpm, do not use the OEM inner spring I was told.
Do not know, could not find out, the spring rates or spring seat pressures.
Without having it in front of me right now, I would think that the springs are quite strong (high rate, linear wound) and have a higher seat pressure than the OEMs and the dual valve spring sets from other manufacturers. This is the only way I can see them coping with 8,000rpm without developing crazy harmonics.
Most of the other dual spring systems are designed as such to give sufficient intermediate load but not unduly load the valve seats and valve stem when closed.
I would not use these springs without the titanium valve retainers because of this. The weight saving will reduce the inertia loads of the valve assembly and assist with reducing valve bounce loads if you float the valve train.
I plan on running the "C6Ms" with my TOMEI dual valve springs, along with CROWER titanium retainers (none in stock at JWT when I bought the stuff), which I know are good for 8,500rpm.
Don't do this, you are inviting failure of springs, rocker arms ect. The natural frequency of the JWT springs match the valvetrains and the cam profile is designed around this. Mixing and matching is inviting surge.
The seat pressure is not that great with these springs, they work because the system is tuned to reduce surge.
Appreciate the advise, but can you say why the cams are supposedly good to 9 and the springs only to 8.
I have read elsewhere on here the JWT C-series springs tend to fail......quite a bold statement but one made anyway???
If the natural frequency of the spring becomes a multiple of the working frequency of the valve assembly then you will develop harmonics at some order, bad enough and held for long enough then something will fail. The spring rate is primarily to follow the lobe within the designed rpm band......again one of the tricks being to use twin springs.
I tend not to believe that you can mismatch and destroy with cams like these within rev ranges like this. Spring technology has come a long way since the good old days.
Once there is no bind etc. I should think things would be ok.
Do you know of anyone or do you have any experience with mismatching the cams and springs and failure being the result? Would be interesting to find out.
Do you know of any other single spring for this kind of lift and duration and rev range?
What do you mean by "Surge".
Thanks again.
SPRING SURGE: The factor which causes unpredictable valve spring behavior at high reciprocating frequencies. It's caused by the inertia effect of the individual coils of the valve spring. At certain critical engine speeds, the vibrations caused by the cam movement excite the natural frequency characteristics of the valve spring and this surge effect substantially reduces the available static spring load. In other words, these inertia forces oppose the valve spring tension at critical speeds.
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I have work on some "L" series and read some Nissan modification catalogs for Nissan including valves and springs titanium set up, also was running with full modified "A" series and all recommend double springs and I never saw cam profiles with the duration and lift of C6 using single springs that was my doubt.
SPRING SURGE: The factor which causes unpredictable valve spring behavior at high reciprocating frequencies. It's caused by the inertia effect of the individual coils of the valve spring. At certain critical engine speeds, the vibrations caused by the cam movement excite the natural frequency characteristics of the valve spring and this surge effect substantially reduces the available static spring load. In other words, these inertia forces oppose the valve spring tension at critical speeds.
Actualy its a very predictable behavior if you know how to model it. JWT is one of the only aftermarket companies that does.
Appreciate the advise, but can you say why the cams are supposedly good to 9 and the springs only to 8.
I have read elsewhere on here the JWT C-series springs tend to fail......quite a bold statement but one made anyway???
If the natural frequency of the spring becomes a multiple of the working frequency of the valve assembly then you will develop harmonics at some order, bad enough and held for long enough then something will fail. The spring rate is primarily to follow the lobe within the designed rpm band......again one of the tricks being to use twin springs.
I tend not to believe that you can mismatch and destroy with cams like these within rev ranges like this. Spring technology has come a long way since the good old days.
Once there is no bind etc. I should think things would be ok.
Do you know of anyone or do you have any experience with mismatching the cams and springs and failure being the result? Would be interesting to find out.
Do you know of any other single spring for this kind of lift and duration and rev range?
What do you mean by "Surge".
Thanks again.
JWT uses Kobe vacume degassed chrome vanadiam spring steel which is recognized as the best spring material in the world by top level engine builders, way beyond the performance aftermarket. It is very expensive. They did however, have one bad batch of this steel which resulted in exactly 4 springs breaking in one batch. This was the extent of the spring failure. The rev problem in SR's is because of the hydralic valvetrain, not so much the springs in this case.
Surge is when the springs stop following the cam due to mostly 5th order harmonics. It is affected by the natural freqency of the spring, the effects of the mass distribution of the rest of the valvetrain and the cam profile. I have seen people doing real racing like you, not screwing around on the street, suffer from rocker breakage when running Tomei or JUN valvesprings with other brands of cams.
I know for sure that JWT cams and springs are tuned around the surge limits so I suspect other good companies like Tomei and JUN may do this as well. This mixing and matching is not a good idea. It may work but why do expensive experimenting.
Thanks for the feedback guys. Sounds like "surge" is just the word used to describe the spring behavior at the critical frequencies.
On another topic, crank dynamics, this behavior can be described by "transmissibility", and is relative to the crank's Nf and the crank pulley/damper/absorber, which ever you have. There are some very interesting articles from the aircraft industry that describe these behaviors and they have actually done tests on Nissan 4 cylinders, Chevy V8's and straight 6's (with dyno charts and various order excitation graphs). Interesting that the "opposing" forces effecting the dynamic spring rate in the valve train, also has been proven to REDUCE crank hp with too light or out of "tuned" crank appendages. In other words, through a straight pull in one gear where the crank is constantly accelerating the hp gain from reduced weight is real, however hold it in a steady state condition and the transmissibility factor reduces the hp delivered from the crank. Important to note however that on a stiff 4cyl crank the losses are less and the effect on the crank in terms of cyclic stress failure is significantly longer in terms of MTBF when compared to say a straight 6 or V8. They actually broke a 350cid chevy crank at it's critical frequencies (within the normal rev range) in under 200hrs.
Either way we'll see soon enough. I'm collecting parts for another motor with near completely different base geometry than the standard SR. It's going to be one big expensive experiment. Boom or Vroom, we'll see.
Enjoy the chat. Keep it comming, there's nothing like a smoke between intense motor tech chats.
Thanks for the feedback guys. Sounds like "surge" is just the word used to describe the spring behavior at the critical frequencies.
On another topic, crank dynamics, this behavior can be described by "transmissibility", and is relative to the crank's Nf and the crank pulley/damper/absorber, which ever you have. There are some very interesting articles from the aircraft industry that describe these behaviors and they have actually done tests on Nissan 4 cylinders, Chevy V8's and straight 6's (with dyno charts and various order excitation graphs). Interesting that the "opposing" forces effecting the dynamic spring rate in the valve train, also has been proven to REDUCE crank hp with too light or out of "tuned" crank appendages. In other words, through a straight pull in one gear where the crank is constantly accelerating the hp gain from reduced weight is real, however hold it in a steady state condition and the transmissibility factor reduces the hp delivered from the crank. Important to note however that on a stiff 4cyl crank the losses are less and the effect on the crank in terms of cyclic stress failure is significantly longer in terms of MTBF when compared to say a straight 6 or V8. They actually broke a 350cid chevy crank at it's critical frequencies (within the normal rev range) in under 200hrs.
Either way we'll see soon enough. I'm collecting parts for another motor with near completely different base geometry than the standard SR. It's going to be one big expensive experiment. Boom or Vroom, we'll see.
Enjoy the chat. Keep it comming, there's nothing like a smoke between intense motor tech chats.
Do you have link to the crank information? I would like to read that.
"Vees for Victory" is the history of the Allison V-1710 V-12 aircraft engine of WWII vintage. It has a graph or two showing that engine's harmonics. One of the reasons it had a mere 3,000 rpm redline.
Also interesting is an energy balance; only 30% of the available BTUs were turned into motive work.
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Bruce in Houston
1990 Acura Legend LS, stock (so far)
1994 Nissan Sentra SE-R (original owner) w/ $tuff, converting to ITA (even more $tuff)
1998 Suzuki Bandit1200S w/ $tuff, W.W.B.O.C. #101
2002 Dodge Dakota tow beast, stock! RIP swwwinger
