Bink

J-Rod - do you have the lobe profiles on these cams? I 'm not following on your decreasing the exhaust duration. Great post. <img border="0" title="" alt="[Cool]" src="gr_images/icons/cool.gif" /> <img border="0" title="" alt="[Cool]" src="gr_images/icons/cool.gif" /> <img border="0" title="" alt="[Cool]" src="gr_images/icons/cool.gif" />

J-Rod

Not decreasing, increasing. Increasing the exhaust profile like the stock Z06 cam, aftermarket cams have less exhaust profile. I am talking about more exhaust lift and duration for stock exhaust cars (like my Z06, which I used as an example)...

<small>[ December 20, 2002, 01:31 PM: Message edited by: J-Rod ]</small>

Serial Thriller

Is there a way to calculate for fast ramp rates (compared to stock) such as XE-R lobes?

Ragtop 99

iTrader: (7)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Serial Thriller:
<strong>Is there a way to calculate for fast ramp rates (compared to stock) such as XE-R lobes?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Yes. Its an area under the curve issue and its non-linear so your math needs to be dusted off. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

Ragtop 99

iTrader: (7)

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"> So what do you think about a cam that spec out as follows.
230/245 .591/.595 112
</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I think it would suck on the street in terms of drivability.

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif"> So, to mimic a stock Z06 camshaft it would be 214/228 .600/604 115 LSA -2 degrees ground in.
</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I don't know that the -2 theory works with a 14 degree split. Even, w/o headers, I doubt the gains over a 214/222 or 214/224 would be worth the loss of drivability from a 228 exhaust. I'd bet a 218/224 would out perform it and have similar drivability.

J-Rod

I have been wondering about a few things related to camshaft design. So, since I had a few spare cycles today I decided to play around with some spreadsheet numbers. Keep in mind this is based simply on numbers, and may have no bearing to what is going on in the real world. But I invite your comments. I have been wondering what to do with a car with stock exhaust (I will use my Z06 as an example), and an otherwise stock motor. I.E., a cam only change.
Stock LS6 heads have an average I to E flow % of .769.
.050 I E %
.100 61.6 56.7 0.920455
.150 93.6 85.8 0.916667
.200 126.1 107.8 0.854877
.250 155.9 127.8 0.819756
.300 183.9 142.5 0.774878
.350 205.9 153.7 0.746479
.400 224.4 162.5 0.724153
.450 239.1 170.1 0.711418
.500 250.7 175.7 0.700838
.525 - -
.550 256 180.0 0.703125
.575 - -
.600 257.2 183.2 0.712286
.625 - -
.650 260.7 185.2 0.710395
.700 263.6 186.8 0.708649

AVG 0.769537
The CNC LS6 heads compare with a .721,
.050 I E %
.100 67 50 0.746269
.150
.200 142 104 0.732394
.250
.300 210 150 0.714286
.350
.400 254 185 0.728346
.450
.500 290 203 0.7
.525
.550 304 210 0.690789
.575
.600 286 212 0.741259
.625 -
.650 -
.700 -

AVG 0.721906

The ARE "new port" comes in with .735
.050 I E %
.100 - -
.150 - -
.200 138 114 0.826087
.250 -
.300 205 157 0.765854
.350 - -
.400 262 194 0.740458
.450 - -
.500 297 210 0.707071
.525 - -
.550 314 216 0.687898
.575 - -
.600 321 220 0.685358
.625 - -
.650 - -
.700 - -

AVG 0.735454

The LPE Stage I's compare with .745.
.050 I E %
.100 - -
.150 - -
.200 153 120 0.784314
.250 - -
.300 228 171 0.75
.350 - -
.400 276 205 0.742754
.450 288 -
.500 294 220 0.748299
.525 - -
.550 307 224 0.729642
.575 - -
.600 314 225 0.716561
.625 - -
.650 - -
.700 - -

AVG 0.745261

As we can see, the stock 02 cam has more exhaust duration. My suspicion is that this has to do with the stock exhaust being a bit restrictive, and to help evacuate the cylinder to reduce intake charge dilution.. Now I have seen folks changing cams in stock headed Z06s and making good power. 420+ for tamuz06, as an example. Now, in looking at the cams they are using I see that they have a tighter LSA meaning more overlap, they have headers which help with the scavenging effect. So, on a car with a more open exhaust I would expect to see perhaps a bit less duration that a stock camshaft to take advantage of this increase in exhaust flow.
One of the things that I have also seen is that the LS1/LS6 intake begins to be a hindrance over 300cfm. So, now we have to play with another variable. You get the exahust port flowing good, you have a free flowing exhaust, so now you need even less duration on the exhaust side. But you have to start bumping intake port lift and duration up to compensate for poor intake flow.

Ok, so lets look at the Z06. TAMU and other have headers and no cats, they installed this cam. The F1 specs at
F1: 230/226 .591/.569 112

The MTI x1 is similar

MTI X1: 230/227 .591/.571 112

The stock '02 LS6 cam specs: 204/218 .551/.547 117.5lsa
The exhaust is only 0.93577981651376146788990825688073 of the intake duration
Multiply 230 by 1.0686274509803921568627450980392 (the Z06 intake to exhaust %)
245.78431372549019607843137254902
The lift I to E % on the F1 cam is 0.96277495769881556683587140439932
By comparison the stock '02 cam is 0.99274047186932849364791288566243
Multiply .591 by 1.0073126142595978062157221206581

595.32175502742230347349177330896

So what do you think about a cam that spec out as follows.
230/245 .591/.595 112

Similarly Patrick G's "old man cam" comes to mind as it is really closer to a Z06 Cam. It is descibed as a z06 cam on steroids.
Its specs are 214/220, .600/.527, 115 LSA, -2 degrees ground in.
As you will notice, like the stock Z06 cam it is bigger on the exhaust duration like the stock Z06 cam, but not a smuch. Using the stock multiplier it would be 228.68627450980392156862745098039. However it is smaller on the exhaust lift. Using the stock Z06 mulipliers again, the lift would be around 604.38756855575868372943327239488.

So, to mimic a stock Z06 camshaft it would be
214/228 .600/604 115 LSA -2 degrees ground in.
My suspicion is that putting most of the camshafts made today in a car with the stock exhaust would result in suboptimal performance, and the only way to get to a level of parity using stock exhaust would require a bigger exhaust side.

Most of this has been driven by my noticing that many cams are heavy on the intake side. Also, some heads seem to have better exhaust ports than some other heads. If you get the exhaust ports closer to 80% and the header, etc... keep the system efficent, you will need even more intake profile to keep up. I know many folks have brought up the fact that there is no such thing as a "magic cam". An engine is a system, and for that system to operate efficently all things need to be optimized to work together. Hence my question. I haven't seen any cams that work with stock exhaust. Now, I know the easy answer is "put on headers". But, there are some folks that want their mods to be either undercover or otherwise "dealer friendly". So, I was playing with what to do with an otherwise stock Z06, just a cam change. And that is what I cam up with. Now, the lift numbers may be a bit too high especialy on the exhaust there may be PTV issues. Also, I don't remeber exactly wher ethe stock heads go turbulent at, but it was in the high .5 (like .590) if memory serves me correctly. Anyhow, I just thought I would trow this out there and see what folks think.

DONAIMIAN

iTrader: (18)

ya im gona have to read this one a couple of times over but I think I understand what your saying.

Old SStroker

Gee, maybe Chevy thought of all those things, and maybe a few (hundred) others before they chose a cam.

J-Rod, if you are serious about evaluating cams, etc. get into Performance Trends' "Engine Analyzer Pro", learn how to use it then go to it with about any cam you can think of. You can specify exhaust back pressure, etc. ad nauseum. It's a great way to kill a couple of hundred (or thousand) hours, and learn a lot. Less than $500 and worth it.

J-Rod

That is what i was looking for. As you said, my math may need to be dusted off. All I did was take the stock intake to exhaust percentages, and then transfer them to another camshft. I know that the numbers may be nonlinear, but it gave somewhere to start at.

My question was based upong the premise of the stock camshaft having a bigger exhaust profile, and how much larger an aftermarket camshaft would need to be, to mimic it. I know that I did not take into account many of the other camshaft variables, but at least it gave me someplace to start from.... If anyone else has ideas, please feel free to comment.

<small>[ December 23, 2002, 12:24 PM: Message edited by: J-Rod ]</small>

J-Rod

Actually someone I have been talking with has it. The problem is that he lacked all the ddata necessary to put together a good model for the Z06. He was missing a lot of the information about port length, size, etc... To make an accurate model.

My numbers were based upon a factory cam, but simply making the camshaft bigger using the factory intake to exhaust ratios. The factory cam is bigger on the exhaust side, my guess would be because of a restrictive factory exhuast (in comparison to headers and a free flowing exhaust). I was simly looking at a bigger version of the factory cam that would work with the rest of the system.

But, if you have any of the data for doing the modeling, I'm sure I know someone who would be interested in seeing it...

Old SStroker

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by J-Rod:
<strong> Actually someone I have been talking with has it. The problem is that he lacked all the ddata necessary to put together a good model for the Z06. He was missing a lot of the information about port length, size, etc... To make an accurate model.

My numbers were based upon a factory cam, but simply making the camshaft bigger using the factory intake to exhaust ratios. The factory cam is bigger on the exhaust side, my guess would be because of a restrictive factory exhuast (in comparison to headers and a free flowing exhaust). I was simly looking at a bigger version of the factory cam that would work with the rest of the system.

But, if you have any of the data for doing the modeling, I'm sure I know someone who would be interested in seeing it... </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">It's fairly easy to measure the ports. Port volumes for LS1 and LS6 heads are readily available on line, and the instruction manual with EA Pro tells you how to use this data. Read the fine manual (aka RTFM).

No one ever said taking full advantage of EA Pro was easy. We learn something everytime we use it.

Study pages 8 and 9 of Comp cams catalog, especially the parts about valve opening and closing points. That's good basic stuff.

www.compcams.com
click on 'online catalog'
click on 'P8' then 'P9'

LS1derfull

J-Rod i hate to complicate things here but your stock LS6 intake port flow numbers are way off, too low. The exhaust numbers match mine pretty close. This is very important because stronger intake flow changes the I/E ratio you are using here to work out cam change. I very carefully flow tested Stock LS6 heads with 5.7 LS1 valves, the intakes flow way more as much as 25cfm more at many lifts than your data. The peak lift flow is .600" at 287 cfm and it carries this to .625" at 28" on Superflow 600 bench. I feel D port on LS6 exh. flows weaker than LS1 ports, even after minor porting they are still weaker than LS1 ports. This is one of the reasons GM uses longer exh. duration and spreads lobe centers to keep idle/emission quality with OEM cams. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

LS1derfull

Looks like i killed another post, oh well <img border="0" title="" alt="[Frown]" src="gr_sad.gif" />