miami993c297

iTrader: (6)

Hi Patrick

What are the last updates on your results?

The way you choose this time seems a little bit different than the previous, just looking at the numbers from the cam which I know are only #.

If I understand, your goal is to obtain equivalent peak torque and power numbers with your new cam with both curves more filled everywhere ??
And you want to add some drivability (closer from the Mamo cam) as well ??

That is suppose to give an ideal coktail, the one I am looking for, really interested to follow your progress on this path...and jump on it !!!!

Is there any down side you can predict for a daily driver use ??

By the way I sent you a pm last week.

Christian

ThirdGenLS1

iTrader: (11)

hope everything is coming along Patrick, i just got my cam in today from thunder. Speced out to be a 228.5/232.9 .638/.640 112 + 2, cant wait to get it in now.

Justin

Spinmonster

I thought that if two cams were identicle except for the LSA the one with the tighter LSA peaks earlier and loses top end.

As for the DCR of the 2 cams listed, my question is what is different about raising the the static compression on the 237 cam to get 8.8 dcr not advancing the cam on install to get an earlier intake valve closing point. In your example, you kept the 11.5 static compression constant which wasn't what I proposed. What I don't understand is why you couldnt just raise the Static cr to 12:1 to get the desired DCR and gain the TQ that way. I'm a bit lost. To illustrate what I was talking about is how would the 237 cam in a 12:1 static motor with 8.8 dcr compare down low to a 224/228 110lsa in a 11.5:1 motor? Lots of the TQ increase you are getting is from the LSK lobes with more lift but DCR is changeable on any cam. Your cam before this one would have benefited greatly by increasing the static CR. yes/no?

Ragtop 99

iTrader: (7)

I think the reason Patrick held the CR constant is that you design the cam to work with the CR you have and your desired operating range. If you raise the CR to 12:1 on the 110 LSA cam, Patrick retards the cam a degree a two and still produces a higher DCR and more power under the curve.

JakeFusion

iTrader: (7)

You do that if you're building the motor from the ground up. But yes, a higher CR engine with a bigger cam will have similar DCR as a smaller cam in a lower compression engine. What Patrick is doing is optimizing for the engine size, a given rpm range, and the headers/intake manifold, all while keeping the overlap at a desired level.

gollum

iTrader: (1)

Yea, I would much rather change cams than shave heads.

Spinmonster

I was refering to raising the compression on the 237 cam to get to the 8.8 dcr on that cam and getting the missing TQ. You can't raise the compression any more on the 110lsa cam as it is just about at the limit for pump gas.

I am simply pointing out that if the engine/car was optimized for the use of the 237 cam, then it wouldnt be as wide a perormance difference. Other variables certainly play a huge role here such as tight lsa, liift, and lsk lobes so its not apples to apples. I think the huge loss in TQ was from a bad cam choice; the 237 on a 111 or 112 wouldnt be a TQ slouch, it would have been higher in DCR.

Patrick G

iTrader: (14)

Ragtop is right. The internal dimensions of my motor are not changing. I already have forged pistons (flat-tops with 2cc reliefs) and my heads are already milled to 59cc. Not going to be changing anything else. In other words, my static compression is fixed until further notice. Since this is true for most enthusiasts as well, I'm trying to illustrate how you can pump up the torque of the motor with cam timing.

The question of whether a narrower LSA cam with the same duration will peak earlier and lose top end compared to a wider LSA cam can be answered this way.

Take two cams:
224/228 110LSA +0
224/228 114LSA +0

The 110LSA cam in an 11.5:1 SCR motor:
IVC 42 degrees ABDC (power peak at 6200 rpm)
EVO 44 degrees BBDC (long power stroke, good for torque)
Overlap biased 1 degree to the intake side of TDC (will carry past peak power very well)
8.86 DCR (very high)

The 114LSA cam in the same 11.5:1 SCR motor:
IVC 46 degrees ABDC (power peak at 6300+ rpm)
EVO 48 degrees BBDC (medium power stroke, good for torque)
Overlap biased 1 degree to the intake side of TDC (will carry past peak power very well)
8.56 DCR (good)

With 0 advance, this shows that the 114 cam will make peak power at a higher rpm, but it gives up 3 tenths of a point in dynamic compression.

Now let's say you want to bring up the DCR of the 114 LSA cam to match that of the 110 LSA cam you advance it 4 degrees. Look at what happens:
IVC 42 degrees ABDC (power peak at 6200 rpm)
EVO 52 degrees BBDC (shorter power stroke, softer on torque)
Overlap biased 3 degree to the exhaust side of TDC (will fall off past peak power much quicker)
8.86 DCR (very high)

So in a nutshell, to get the DCR with the 114LSA cam up to that of the 110LSA, you'll have to advance the cam 4 degrees. When you do that, ugly things happen. The biggest is you open the exhaust valve 8 degrees earlier. That means you're cracking the exhaust valve 8 degrees earlier in the power stroke, bleeding off valuable engine torque. Plus, your overlap is now biased 3 degrees to the exhaust side, which means that even though the 114LSA +4 cam will still peak at 6200 rpm, it will not carry the power as well after that peak. Basically, it will fall off quite a bit faster than the 110LSA +0 cam would.

So in this illustration, the 110LSA +0 cam will be a better top-end power than the 114LSA +4 cam, even though they have the same dynamic compression. Make sense?

Patrick G

iTrader: (14)

The problem with using a wide LSA, large duration cam is that most people are only running 10.5-11.5:1 static compression. If that's all you have, it's difficult to get the dynamic compression up into the mid 8s. Funny, lots of people are trying to run cams designed to go into 12.5:1 SCR race motors and expecting them to be torquey with their 11.0:1 motors, LOL. Sure you can raise static compression to bring your DCR to an appropriate level. But for 98% of those on this board, running a 12.0:1+ SCR motor is out of their realm.

Spinmonster

Yes, and I appreciate you taking the time to post all that info for me. I also have a great respect for the experiment.

I am not in favor of advancing the cam for the raising of the dcr. I was suggesting a static compression raise that will not have I/E valve timing issues. When you said the static is a constant for you, my question dies in the water. It is only how the DCR on the 237 being raised from a static compression increase would compare. Stating the limitations on those with 5.7 liter motors looking for a cam swap is putting a qualifier/limitation on the question. Running my 6 liter at 12:1 is easy to get to and for me what is optimum isnt the same. You are saying these facts within the limitations of not swapping anything on the motor. For a guy that is looking for more and doesnt have the fixed scr the question I asked is very different.

On the opinion of cam versus head swaps, I would have opted for thinner gaskets before going cam but I know Parttic has already optimised that with thinner gaskets.

Patrick G

iTrader: (14)

Also, you have to remember, that if you're running an LS6 or a FAST intake, you get very counter-productive when you close the intake valve later than 46 degrees ADBC in a 346 and 50 degrees in a 408. The tuned runner length of those manifolds are going to force a torque peak around 4800 and a power peak around 6300. Closing the intake valve past those points only fight the natural point as to where the motor is wanting to peak. That's why a 237 duration intake lobe on a 114 with no advance is not going to perform well with the plastic intakes: With an IVC of 52.5 degrees, it's going to be forcing a power peak well past what the intake manifold is tuned for.

So even if you got used 13.0:1 SCR to bring the DCR up to 8.8:1, you would still not be working with the manifold...you'd be fighting it. And when you fight the intake manifold, you limit the maximum power production under the curve.

Spinmonster

What is optimum for my 6 liter, FAST manifold, Kooks headers with cats, LS6 ported heads? (Street use) Close to what you came up with? I have .04 gaskets heads not shaved...11.5 or so static? In my case I have a very tq'y set-up with an xer 224/230 on a 114. I thought i hit it right on.

The question is what changes from my bigger bore?

JakeFusion

iTrader: (7)

Since the 6L (364) is only slightly bigger than the 346, looks for a 47 or so IVC. Your cam is just under that (46) and the DCR should be around 8.7:1 if the SCR is 11.5:1. Overall, it should work pretty well.

JakeFusion

iTrader: (7)

One question Patrick... I'm thinking that the IVC of a 447cid should be around 55 or so with a FAST 90. What are your thoughts?

Patrick G

iTrader: (14)

Generally, you want to add 8 degrees of duration for every 50 ci of displacement increase. Since you'd be adding 101 cubic inches, you'd want to add 16 degrees of duration. That would give you a max IVC of 54 degrees ABDC. Anything above that really starts to work against the runner length of the FAST intake manifold. If you're at 55 degrees ABDC, then I would consider that close enough to be within the window that the FAST likes.

Patrick G

iTrader: (14)

Going from a 5.7L to a 6.0L raises your SCR .45 points and your DCR .32 points assuming no other changes to the heads or head gaskets. What is the ICL of your cam?

bmfcamaro

iTrader: (1)

have you dynoed this yet

obZidian

iTrader: (2)

so for my 408ci motor, the window i around 46IV and 52EVO?

Patrick G

iTrader: (14)

On a 408, you get diminishing returns after you close your intake valve after 50 degrees ABDC at .050" when using a FAST intake. A good torquey window is 46-50 degrees ABDC. That's equivalent to 42-46 degrees on a 346.

Optimum EVO depends on its relationship with the intake. Ideally, you want to have your overlap centered over TDC or biased toward the intake side (not the exhaust). Generally that requires running a larger exhaust duration compared to intake and/or limiting the amount of advance ground into the cam.

BriancWS6

iTrader: (18)

I LOVE this thread!