TurbopigB4C

iTrader: (5)

Does comp grind LSAs and ICLs using .5 or .25 increments? This would allow the possibility to get valve events a lot closer or exactly the same.

TurbopigB4C

iTrader: (5)

As he points out with a RS the LSA needs to be tighter to gain the same overlap and will lower the window of the powerband. Essentially the 230/224 cam when compared to a traditional 230/234 you would be trying to match overlap and valve events On this example the traditional split on a 112lsa makes 8* overlap while the RS on a 109 LSA would make 9* overlap but would make more torque and power everywhere until 6200-6500 the traditional split would peak at around 7000 and does not make sense to most applications.

redtan

iTrader: (5)

So as I understand it, intake valve timing remains the same given the same intake duration and LSA/ICL...so all that you're doing is closing the exhaust valve sooner.

So what does closing the exhaust valve sooner with the same intake valve opening/closing do to make more low end torque?

TurbopigB4C

iTrader: (5)

The valve events and overlap on a 223 EHI .634 with 219 LSL .607 are the same at a 109LSA as the 223/231 traditional split on a 112 LSA but will not need to worry about evacuating the cylinders below 6500 making the higher exhaust velocity from the short duration allow more torque everywhere along with the tighter LSA being better.

redtan

iTrader: (5)

/So basically it allows you to run a tighter LSA without the increase in overlap?

TurbopigB4C

iTrader: (5)

If you want a practical example with numbers you should read the GM High Tech Performance article where they compared cathedral and rectangular heads as well as using traditional cathedral and very wide rectangular splits on both heads. The super large splits on a cathedral head did make more peak hp than the traditional split even though it was not optimally designed for that head but did lose torque down low. The same concept can be taken even further that the traditional split compared to a uniform split would make more peak hp but lose torque down low and that can be taken even further that a uniform split is giving up some slight torque when compared a reverse split.

This idea only applies correctly though when all the different splits have a very similar overall valve overlap. The smaller the split or larger the reverse split the tighter the LSA must become to match overall valve overlap.

This test even points out that on all pulls the Fast 102 loses torque during a certain window.

TurbopigB4C

iTrader: (5)

Correct. The tighter LSA brings torque lower as well as lowering where the cam will peak. The whole idea with a reverse split is that you want power to peak around 6200 to shift at 6500 and have as much overall hp and torque all the way to that point with no concerns above it. The identical overlap will provide the same kind of pull but on a smaller overall duration making more torque.

TurbopigB4C

iTrader: (5)

Going off of the stickie discussion according to that it states that a 218/218 on a 109 lsa is the same valve events as a tr224 on a 112lsa and would peak at 6200 rpm. Is this statement by 93pony incorrect?

TurbopigB4C

iTrader: (5)

I was just going off of what 93 pony said they did not get into advance but I believe the TR224 is +4 advance ground in.

PREDATOR-Z

I dunno what 93pony said but a 218/218 on a 109 event at straight up has a 38 IVC. That will peak earlier than 6200 rpm with a LS6 intake, more like 5800 or 5900 rpm.
TR 224 112 lsa has a 40 IVC and will peak roughly 200 rpm later at around 6000 to 6100 with LS6 intake.

TurbopigB4C

iTrader: (5)

So IVC plays the biggest part in where a cams power peaks? So the 218/218 would need to be a 109 lsa with 111 icl to peak similar to the TR224? How do you figure out valve events like that?

PREDATOR-Z

Yes, a lot of it has to do with experience on similar setups. Sometimes you get close and tweak by changing lsa or advance /retard etc...
In general a cam with 42 ivc 'should' peak at around 6200 and take 100 rpm off for every IVC degree you close sooner. Peak on a cam is directly relative to the shape and size of the intake used.

TurbopigB4C

iTrader: (5)

Thanks that is probably exactly what I wanted to know from this thread.

TurbopigB4C

iTrader: (5)

So to double check my calculations a 219 intake lobe would want a 113 ICL for a 42.5 IVC.

219/2-113=-3.5
219 - - 3.5 - 180 = 42.5

TurbopigB4C

iTrader: (5)

Am I also to assume that the 42 IVC is for 6200 RPM on a 346. Would it be safe to assume the 42 IVC would increase proportional to the increase in displacement?

For example a 427 is 1.234 times the displacement of a 346 making the IVC increase to 52?

TurbopigB4C

iTrader: (5)

If anyone was interested I did the math now that I understand it on the 218/218 cam with the same IVC and valve overlap as the TR224 on a 112.

The TR224 should be 112+4 while the 218/218 would be 109-2. Both have a 40 IVC and 0* overlap.

TT427

iTrader: (1)

Anyone do an LSL lobed reverse? Was thinking of a 231/227 deal. They also havd a "turbo" grind thats 227/223, thats the eventual direction I am headed. Seems a reverse could pull double duty?

TurbopigB4C

iTrader: (5)

I was considering lsl/lxl lobe reverse to keep noise down. The 2* increments with the LSL lobes allow for lots of different reverse combos. A 229/226 or 225/222 I think would be a nice reverse split.

rubrick1

I'm also considering a RS cam. Just bought a 98 M6 Z28 and I'm planning on staying with the LS1 intake and installing the MAC mids I have lying around. I'm also planning on keeping the 3.42 gears so I'm actually looking for a cam that sounds/runs like stock and also [B]lowers[B] the peak where max HP occurs. I want to shift no higher than 5800-6000 RPM.

I was thinking of something like a 214/210 with .575+ lift on a 110 lsa. Would a cam like that sound and idle like a stocker Mr Predator?

TurbopigB4C

iTrader: (5)

218/214 LXL lobes on a 110 lsa + 0 would be -4* overlap and 39 IVC so should peak around 5900 rpm using Predators formula.