Best Cam Profile For A Stock SC?

[emcon5]

Originally posted by smestas
Why does that last dyno have the big dip in the middle of the torque curve as opposed to the nice table top shape mentioned previously?

That dip really isn't that big, looks like ~ 3 ft/lbs. The scale is different (numbers on the right), and really hard to read in that pic. Noah posted a cleaner version here:



Tom

[GrindingGears]

Point of clarification:

Is a 330 Sport SC cam the same as a stock SC cam?

[rdane]

Dyno comparisons are really an unrealistic comparison but the graph comparisons should be something we can work from.

We have mountain profiles, then have Noah's twin peak profile and we have flat topped mound profiles from the different cams. Be interesting for someone with the skills to apply them all in the same scale so we can stop quessing as much.

Th dip is closer to 5 than 3. Which is around 3% of the total torque.

[smestas]

Originally posted by GrindingGears
Is a 330 Sport SC cam the same as a stock SC cam?

It's considered a step up from a stock SC cam profile and the 964 is considered two steps up.

[GrindingGears]

Thank you

[emcon5]

Originally posted by rdane
Be interesting for someone with the skills to apply them all in the same scale so we can stop quessing as much.

True. Do you have a better quality scan of your dyno sheet?

The scale on Noah's is further confused by the torque numbers not matching the main horizontal lines on the graph. If you blow it up in a graphics program, you can see light grey lines at the torque scale. I made them a little clearer, and superimpsed them over the graph. The first peak is ~174@ ~4250RPM, drops to ~171 @ ~4750, then back to the peak, 176.4 @ ~5250.



Tom

[rdane]

I am doing pictures of the sheet not scans. Sorry for the size. Tom can your graph 2K through 6500 rpm? Both ends should tell us a lot.
http://standingwave.org/albums/porsche/agg.jpg

superman's

http://standingwave.org/albums/porsche/alr.jpg

[emcon5]

Here is Dane vs Noah. I started at 3K, because that is about where your run started Dane. I blew up and made reference lines on both graphs, these numbers should be ± 1 ft lb, maybe ±1.5 on yours Dane, it is harder to do with a photo. The lines aren't quite square, and there is some paralax in your picture (I think the bottom is a little closer than the top).

The bottom of Noah's dip isn't really shown, because it fell between data points, the line between 4600 and 4800 shouldn't be straight, but this is fairly close. If I get time, I will do the same with Jim's, and maybe even mine and add them to the chart.



Here are the numbers I used. If you want to play with them, I can send you the file.




Tom

[rdane]

Very cool Tom, can you plot Jim's and Charlie's so we get a small data base going for comparison of curves? The higher and lower we go the more useful they are. Then you need to reflect on the HP for each and see what is below the curve.

[emcon5]

Tom

[rdane]

Great stuff Tom...how about marking them by cam types instead of the owners and having all 5 (or more) one graph. I know easy for me to say

Thanks,what you have done makes it easier to read!

[fintstone]

I have to vouch for the webcam/JE Pistons 9.3:1/early big port ('78) heads and CIS/SSI setup that several guys describe. That is exactly what I had built by Supertec. I have not dynoed mine yet, but it is the quickest, smoothest, CIS engine I have come across and the butt dyno puts it easily in the HP range they describe.

[dd74]

Originally posted by fintstone
I have to vouch for the webcam/JE Pistons 9.3:1/early big port ('78) heads and CIS/SSI setup that several guys describe. That is exactly what I had built by Supertec. I have not dynoed mine yet, but it is the quickest, smoothest, CIS engine I have come across and the butt dyno puts it easily in the HP range they describe.

Are you going to dyno it in NM? That altitude will kill your hp, won't it?

[fintstone]

Originally posted by dd74
Are you going to dyno it in NM? That altitude will kill your hp, won't it?

I understand that they adjust the graph/hp per some sort of algorithm. I am still looking for an excuse to drive back to LA with it. Maybe to get some A/C installed (underbody condensor) at performance aire when I have a few extra bucks..maybe I can dyno it then at sea level. I am currently on a no Porsche parts/expenses diet due to finances...but expect a big improvement in that area soon.

[dd74]

Originally posted by fintstone
expect a big improvement in that area soon.

Way to go!

[aigel]

Originally posted by dd74
Are you going to dyno it in NM? That altitude will kill your hp, won't it?

That brings up a good point. Dyno numbers are very dependant on the actual dyno (manufacturer, model), elevation, temperature etc. etc. Putting those graphs on top of each other is a great idea, but you'd have to put error bars on there too. It will be a blurr, everything will overlap. The only thing - as mentioned earlier - that you will be able to compare is the shape of the curves.

Don't forget: Unless you are drag racing, you can obsess about the last Nm and the last hp, but in the end the skill of the driver makes the biggest difference. I keep my mods to a minimum to have more $ for instruction.

Also, if you want to make serious power, the CIS has to go. For chugging around town, you wont notice the difference between the cams discussed above.

George

[Henry Schmidt]

No dyno sheets, just some personal experience. If performance is your goal, "more is better". Every time, every time one of my customers has done the research, looked at the sheets, read the cam specs ad nauseam, the result was "this cam makes more low end torque, I want this one" the end result was " what would it cost to change these cams ?".
Pick the biggest cam your engine will take.
MORE IS BETTER , more lift- more duration. I like the 20/21 if smog is not an issue. If smog is an issue there will need the be a warmup regulator change.

[dd74]

Henry - in most cases, on an SC, do the rockers, valve springs, etc., need to be modified for the 20/21 cams, or are they robust enough to coincide with the increase lift and duration of the 20/21 cams?

Thanks.

[Henry Schmidt]

The rockers are fine. When set properly, shimmed .070 from coil bind at max lift, the stock springs function fine. The closer you get to .500 lift and 8000 rpm the more you need a high performance spring.
We are working on a new spring as we speak. We have used Aasco springs for years, but now that we are heading past .500 lift the Aasco spring is reaching it's limit.
A quick note: 962 springs are just stock spring sorted and rated as the top 2 %.

[emcon5]

Originally posted by rdane
Great stuff Tom...how about marking them by cam types instead of the owners and having all 5 (or more) one graph. I know easy for me to say

How is this?



I probably shouldn't include my engine on the chart, as this is comparing 3.0 engines. I also decreased the scale, to expand the 100-200 ft/lb area.

The torque numbers themselves are meaningless, as they are different dynos (except Dane/Jim). However, we can compare the shape of the curve. I think the most suprising of these is the comparison of Dane's and Jim's engines.


Jim has an 83, Dane a 79. Both engines have early exhausts with Web 20/21 cams, and CIS, and these were done on the same dyno, on the same day. Dane has lower compression, but larger ports. It looks like the smaller ports and compression gave Jim a boost in torque down low (which is exactly why Porsche did it), but as the RPMs climb, the Torque drops off earlier (5000 rpm vs 5600) and faster than Dane's. Jim drops 20% between 5K and 6.4K, Dane only drops 13% and most of that is >5.6K. Interesting.

I believe all the engines shown have SSIs, so I would like to get a stock SC with SSIs for comparison. We have one with David (dd74) but the chart is too hard to get the numbers off of accurately. David, if you can get me the torque numbers every 200 rpm from 3K to 6.4K, PM me with them, I will add it to the chart.

Or if someone has a better graph of a 3.0 with SSIs, I can try and pull the numbers from the graph.

Tom