Non stock cam users....
03-19-2010, 04:19 PM
#16
.....
I would not agree with your assessment. The Webcam 20/21 cams are CIS cams and are awful on an injected engine. Furthermore, you are missing the lobe centerline information which has a lot to do with the characteristics of the camshaft. From the spintron testing I've done, the Porsche camshafts have slow openeing ramps and are very hard on the valvetrain with high harmonics. I think this is a funamental reason why custom camshafts with similar lift and duration outperform a Porsche camshaft.
FWIW, it has been my experience that very little is gained from a 3.8l conversion (3.8RS pistons, RS cams, and a chip). I don't know how much the motronic programming limitation is the cause or simply the heavy Mahle pistons and poor squish. I am about to install a MoTeC system + the 9M USA Sport 2 camshafts on an engine with the 3.8l RS pistons. We'll see what happens. The baseline showed 254whp where the 3.6l with the same cams and MoTeC showed 301whp. (basically the car you rode in Bill). It will be interesting to see the difference.
Technically speaking the 964 RS/Cup engines are not blueprinted. The parts for the engine are hand selected and have tighter tolerances in weight and sizing. If you simply install an RS ECU into your stock street car, you get the +13hp the RS engine has. So, yes, it is all the Motronic programming.
I would not agree with your assessment. The Webcam 20/21 cams are CIS cams and are awful on an injected engine. Furthermore, you are missing the lobe centerline information which has a lot to do with the characteristics of the camshaft. From the spintron testing I've done, the Porsche camshafts have slow openeing ramps and are very hard on the valvetrain with high harmonics. I think this is a funamental reason why custom camshafts with similar lift and duration outperform a Porsche camshaft.
FWIW, it has been my experience that very little is gained from a 3.8l conversion (3.8RS pistons, RS cams, and a chip). I don't know how much the motronic programming limitation is the cause or simply the heavy Mahle pistons and poor squish. I am about to install a MoTeC system + the 9M USA Sport 2 camshafts on an engine with the 3.8l RS pistons. We'll see what happens. The baseline showed 254whp where the 3.6l with the same cams and MoTeC showed 301whp. (basically the car you rode in Bill). It will be interesting to see the difference.
Technically speaking the 964 RS/Cup engines are not blueprinted. The parts for the engine are hand selected and have tighter tolerances in weight and sizing. If you simply install an RS ECU into your stock street car, you get the +13hp the RS engine has. So, yes, it is all the Motronic programming.
Thats what blueprinting is, hand select and fit all the pieces w/ an eye to performance not longevity or noise
can't wait to see how the new engine performs too
the other thing not mentioned here is that the bottom end needs to be built w/ an eye to the rpm that the top end and cams will want.
03-19-2010, 04:50 PM
#17
Nordschleife Master
Thats what blueprinting is, hand select and fit all the pieces w/ an eye to performance not longevity or noise
For instance, the weight tolerance on the connecting rods is 9g for street and 5g for RS. In a racing engine (including the 964 Cups) we balance everything within a few TENTHS of a Gram. There is no way I would run an engine with 5g weight differences to 8k like we do in the racing engines.
03-19-2010, 05:51 PM
#18
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GT2/EVO CAMS
That's what I running. 3.8l Promotive built.
Even with the tall 6th gear(/31), I can accelerate from 20mph,
and then skip sideways in first @ 20mph.
That's what I running. 3.8l Promotive built.
Even with the tall 6th gear(/31), I can accelerate from 20mph,
and then skip sideways in first @ 20mph.
03-19-2010, 06:00 PM
#19
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All interesting stuff! I went to take pictures of my car in pieces today, here is the pitting on the cam. Many of the rockers had very slight wear, as did a few pins. This was probably due to infrequent valve adjustments by previous owners. My cylinders and pistons look good, so if anyone needs a set...
I am now awaiting an updated estimate to see what else I can afford to do. The heads will be sent out and polished up, I also am sending out the injectors for rebuild and testing. Everything else in the engine compartment is also getting rebuilt or replaced.
I am now awaiting an updated estimate to see what else I can afford to do. The heads will be sent out and polished up, I also am sending out the injectors for rebuild and testing. Everything else in the engine compartment is also getting rebuilt or replaced.
03-19-2010, 09:56 PM
#20
Nordschleife Master
The pitting on the camshaft is common of what we've begun to see in these engines. The factory cams are fairly soft material. We use Chill Cast cores or billet steel blanks on the custom camshafts we do and they last much longer.
It probably isn't a result of a valve adjust, but rather oil change frequency or type of oil used.
It probably isn't a result of a valve adjust, but rather oil change frequency or type of oil used.
03-20-2010, 12:47 AM
#21
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So, what type of oil are you guys recommending? I was running Mobile 1, 15w50, have used 10w30, but now am leery of lack of zinc zddp in the modern oils. Was considering going to conventional Brad Penn. I believe my builder will be using their break in oil when I get the car back.
03-20-2010, 02:36 AM
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So, what type of oil are you guys recommending? I was running Mobile 1, 15w50, have used 10w30, but now am leery of lack of zinc zddp in the modern oils. Was considering going to conventional Brad Penn. I believe my builder will be using their break in oil when I get the car back.
Fine yourself some oil with high ZDDP content. Guess the EPA banned it but it works much better on cams not running roller rockers. Zinc Dialkyl-Dithio-Phosphate helps reduce the wear ...
03-20-2010, 07:15 AM
#23
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Technically speaking the 964 RS/Cup engines are not blueprinted. The parts for the engine are hand selected and have tighter tolerances in weight and sizing. If you simply install an RS ECU into your stock street car, you get the +13hp the RS engine has. So, yes, it is all the Motronic programming.
Sure, the Motronic is different and with the RS ecu a standard car will make more power, however I have proven to myself many times that when you fit Motec to stock 964's and compare them to Motec on an RS, you also get 10hp more from the RS. If you then rebuild the 964, deck the heads and do a narrow valve seat job on the heads, you get your 10hp back.
06-03-2010, 10:11 PM
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For a budget street car w/ stock Motronic you cant go to wild on the cams, I know several people w/ the 3.8RS hydraulic cams in 3.6, w/ a 3.8 it's an obvious choice. The mechanical equivalent of the 993RS is the SS cam which also works well
993 Super Sport(mechanical)
lift .490I/.456E
Advertized duration 260/248
duration at .050" 240/230
All of these grinds work well in the 3.6 litre and up engines and the choice depends on your mods and driving style.
I also recommend Steve Wong for a chip for these engines, he will work w/ you to get it right. I have several of his chips and am very happy w/ them.
993 Super Sport(mechanical)
lift .490I/.456E
Advertized duration 260/248
duration at .050" 240/230
All of these grinds work well in the 3.6 litre and up engines and the choice depends on your mods and driving style.
I also recommend Steve Wong for a chip for these engines, he will work w/ you to get it right. I have several of his chips and am very happy w/ them.
