A Look at a Few of Ducati's 4-Valve Cams
I'm not really the one to be writing the definitive article on Ducati racing cams. But, since I have more data than most, I'll have to do.
Set-up
I installed one intake and one exhaust opening rocker-arm in an 888 head, along with the corresponding valves with light springs. This allowed me to check either horizontal or vertical cylinder cams by swapping the cam bearings from one side to the other.
I chose a valve shim which holds the valve off the seat and used valves which are smaller than the seat in the head. By doing this the program gets a base-circle run-out figure.
The linear encoder is set up on the chamber side, parallel to and touching the valve head. The rotary encoder has a magnetic collar which sticks to the cam sprocket, with a locating arm that stops against a 6mm bolt screwed into one of the many holes in the head.
The cam opener lobe is dabbed with Redline assembly lube and that appears to cause everything to move smoothly.
The software offers the choice of checking in an engine, at the valve or cam follower, or in a fixture at the cam follower. I tried to tell the program that I was measuring in a fixture, at the valve, but it said I can't do that. I entered the rocker-arm ratio as 1:1 and will choose cam lift reports (which would be identical to valve lift in the reports.)
The Cam Pro Plus software allows one to view velocity, acceleration and/or jerk. Since I don't fully understand jerk (other than the fact that I am one) I've chosen to look at acceleration.
Finally, the software uses a smoothing algorithm to attenuate 'noise'. I'm not sure how much to apply, but a value of 10 (10 applications of the algorithm) seems to work. That is the amount of smoothing I've decided to use.
Cams
Inlets;
Strada, 'G', 916SPS, 748SPS, 748R, 748RS, '450', '458'
(The only inlets I'm missing are '431', and SP.) (That assumes that the cams I have heard of are all that there are.)
Exhausts;
Strada, 916SPS, 748SPS (SP, FBF 'K'), 748R, 748RS
( I forgot that I have a pair of Roche Replica exhaust cams, I think they're 'G's.)
Results
Inlets
There seems to be three levels of opening and closing acceleration rates that the 'Factory' will accept.
Below is a chart with all of the inlet cams shown (too confusing) along with the acceleration traces. Below that is a list of the reports for the same.
-------------------------------------------------------------------------------- CAM PRO PLUS Valve Lift Report 8:40:16 AM 5/11/2001 --------------------------------------------------------------------------------
C:\My Documents\Cams\458in.CPP
LIFT DUR. OPEN CLOSE AREA
Lobe I1 ----- ----- ---------- ---------- ------
Centerline 110.0 ATDC 0.006 409.2 95.4 BTDC 133.9 ABDC 49.05
.050 Lift C/L 110.5 ATDC 0.020 315.7 47.9 BTDC 87.7 ABDC 48.57
Runout 0.00040 0.050 284.8 31.9 BTDC 72.9 ABDC 48.06
Peak Open Acc. 0.000358 0.100 254.5 16.4 BTDC 58.1 ABDC 46.94
Peak Nose Acc. -0.000331 0.150 231.5 4.8 BTDC 46.7 ABDC 45.52
Peak Close Acc. 0.000377 0.200 211.5 5.2 ATDC 36.7 ABDC 43.77
Lift @ TDC 0.1734 0.250 192.0 14.9 ATDC 26.9 ABDC 41.57
Valve Lash 0.0000 0.300 172.4 25.1 ATDC 17.5 ABDC 38.88
Rocker Ratio 1.00 0.350 152.6 35.4 ATDC 8.0 ABDC 35.66
0.400 130.9 46.2 ATDC 2.9 BBDC 31.59
0.450 103.8 59.7 ATDC 16.6 BBDC 25.80
0.500 59.4 81.1 ATDC 39.5 BBDC 15.19
0.517 --- PEAK LIFT ---
C:\My Documents\Cams\748RIN.CPP
LIFT DUR. OPEN CLOSE AREA
Lobe I1 ----- ----- ---------- ---------- ------
Centerline 117.0 ATDC 0.006 323.6 44.4 BTDC 99.2 ABDC 38.83
.050 Lift C/L 117.3 ATDC 0.020 283.9 24.6 BTDC 79.3 ABDC 38.61
Runout 0.00210 0.050 252.7 9.1 BTDC 63.7 ABDC 38.09
Peak Open Acc. 0.000292 0.100 220.2 7.3 ATDC 47.4 ABDC 36.89
Peak Nose Acc. -0.000367 0.150 195.7 19.6 ATDC 35.2 ABDC 35.37
Peak Close Acc. 0.000295 0.200 174.4 30.1 ATDC 24.6 ABDC 33.31
Lift @ TDC 0.0756 0.250 154.5 40.1 ATDC 14.6 ABDC 31.02
Valve Lash 0.0000 0.300 134.7 50.0 ATDC 4.7 ABDC 28.24
Rocker Ratio 1.00 0.350 113.8 60.4 ATDC 5.8 BBDC 24.80
0.400 90.2 72.2 ATDC 17.6 BBDC 20.32
0.450 59.7 87.4 ATDC 32.9 BBDC 14.20
0.490 --- PEAK LIFT ---
-------------------------------------------------------------------------------- CAM PRO PLUS Valve Lift Report 8:40:47 AM 5/11/2001 --------------------------------------------------------------------------------
C:\My Documents\Cams\748RSin.CPP
LIFT DUR. OPEN CLOSE AREA
Lobe I1 ----- ----- ---------- ---------- ------
Centerline 117.0 ATDC 0.006 386.7 80.8 BTDC 125.8 ABDC 41.95
.050 Lift C/L 116.4 ATDC 0.020 292.8 30.7 BTDC 82.1 ABDC 41.46
Runout 0.00060 0.050 262.2 14.7 BTDC 67.5 ABDC 40.97
Peak Open Acc. 0.000341 0.100 232.0 1.0 ATDC 53.0 ABDC 39.75
Peak Nose Acc. -0.000332 0.150 208.9 12.8 ATDC 41.7 ABDC 38.43
Peak Close Acc. 0.000398 0.200 188.3 22.7 ATDC 31.0 ABDC 36.42
Lift @ TDC 0.0962 0.250 167.8 32.6 ATDC 20.4 ABDC 34.06
Valve Lash 0.0000 0.300 147.3 43.0 ATDC 10.3 ABDC 31.20
Rocker Ratio 1.00 0.350 126.3 53.6 ATDC 0.1 BBDC 28.09
0.400 101.6 65.9 ATDC 12.5 BBDC 23.44
0.450 69.2 82.4 ATDC 28.4 BBDC 16.53
0.492 --- PEAK LIFT ---
C:\My Documents\Cams\748SPShi.CPP
LIFT DUR. OPEN CLOSE AREA
Lobe I1 ----- ----- ---------- ---------- ------
Centerline 111.0 ATDC 0.006 350.3 66.7 BTDC 103.6 ABDC 40.54
.050 Lift C/L 109.6 ATDC 0.020 315.9 48.9 BTDC 87.1 ABDC 40.33
Runout 0.00020 0.050 284.8 32.8 BTDC 72.0 ABDC 39.81
Peak Open Acc. 0.000274 0.100 251.6 15.7 BTDC 55.9 ABDC 38.59
Peak Nose Acc. -0.000237 0.150 224.7 2.0 BTDC 42.7 ABDC 36.76
Peak Close Acc. 0.000314 0.200 199.4 10.9 ATDC 30.3 ABDC 34.50
Lift @ TDC 0.1576 0.250 173.9 23.9 ATDC 17.8 ABDC 31.83
Valve Lash 0.0000 0.300 146.1 38.1 ATDC 4.2 ABDC 27.70
Rocker Ratio 1.00 0.350 113.1 55.0 ATDC 11.9 BBDC 22.27
0.400 65.6 79.2 ATDC 35.1 BBDC 13.27
0.424 --- PEAK LIFT ---
-------------------------------------------------------------------------------- CAM PRO PLUS Valve Lift Report 8:41:07 AM 5/11/2001 --------------------------------------------------------------------------------
C:\My Documents\Cams\916SPSin.CPP
LIFT DUR. OPEN CLOSE AREA
Lobe I1 ----- ----- ---------- ---------- ------
Centerline 119.0 ATDC 0.006 323.9 41.2 BTDC 102.7 ABDC 54.52
.050 Lift C/L 122.2 ATDC 0.020 297.0 26.7 BTDC 90.2 ABDC 54.35
Runout 0.00080 0.050 272.3 14.2 BTDC 78.1 ABDC 53.91
Peak Open Acc. 0.000425 0.100 246.3 0.8 BTDC 65.4 ABDC 53.01
Peak Nose Acc. -0.000371 0.150 226.5 9.2 ATDC 55.7 ABDC 51.78
Peak Close Acc. 0.000473 0.200 209.6 17.6 ATDC 47.2 ABDC 50.30
Lift @ TDC 0.1038 0.250 194.0 25.1 ATDC 39.1 ABDC 48.55
Valve Lash 0.0000 0.300 178.9 32.2 ATDC 31.1 ABDC 46.47
Rocker Ratio 1.50 0.350 163.5 39.4 ATDC 22.9 ABDC 43.62
0.400 147.5 46.9 ATDC 14.4 ABDC 40.57
0.450 130.3 55.0 ATDC 5.3 ABDC 37.32
0.500 111.0 64.3 ATDC 4.7 BBDC 32.72
0.600 56.4 91.2 ATDC 32.4 BBDC 17.55
0.634 --- PEAK LIFT ---
C:\My Documents\Cams\Gintake.CPP
LIFT DUR. OPEN CLOSE AREA
Lobe I1 ----- ----- ---------- ---------- ------
Centerline 102.0 ATDC 0.006 351.5 76.8 BTDC 94.7 ABDC 42.91
.050 Lift C/L 99.4 ATDC 0.020 328.3 65.3 BTDC 83.0 ABDC 42.77
Runout 0.00140 0.050 298.4 49.8 BTDC 68.6 ABDC 42.26
Peak Open Acc. 0.000236 0.100 263.8 32.1 BTDC 51.7 ABDC 40.98
Peak Nose Acc. -0.000198 0.150 236.3 17.9 BTDC 38.4 ABDC 39.27
Peak Close Acc. 0.000269 0.200 210.6 4.3 BTDC 26.3 ABDC 37.03
Lift @ TDC 0.2161 0.250 184.9 9.2 ATDC 14.1 ABDC 34.13
Valve Lash 0.0000 0.300 156.8 23.8 ATDC 0.6 ABDC 30.27
Rocker Ratio 1.00 0.350 123.5 40.6 ATDC 15.9 BBDC 24.84
0.400 74.1 65.1 ATDC 40.8 BBDC 15.51
0.428 --- PEAK LIFT ---
-------------------------------------------------------------------------------- CAM PRO PLUS Valve Lift Report 8:41:26 AM 5/11/2001 --------------------------------------------------------------------------------
C:\My Documents\Cams\stradain.CPP
LIFT DUR. OPEN CLOSE AREA
Lobe I1 ----- ----- ---------- ---------- ------
Centerline 110.0 ATDC 0.006 317.9 33.8 BTDC 104.1 ABDC 31.45
.050 Lift C/L 118.4 ATDC 0.020 286.2 21.7 BTDC 84.5 ABDC 31.26
Runout 0.00080 0.050 252.8 8.0 BTDC 64.8 ABDC 30.70
Peak Open Acc. 0.000318 0.100 217.6 7.6 ATDC 45.2 ABDC 29.40
Peak Nose Acc. -0.000266 0.150 189.0 20.4 ATDC 29.4 ABDC 27.63
Peak Close Acc. 0.000219 0.200 161.4 32.8 ATDC 14.3 ABDC 25.21
Lift @ TDC 0.0738 0.250 132.5 46.1 ATDC 1.5 BBDC 21.95
Valve Lash 0.0000 0.300 100.8 61.3 ATDC 17.9 BBDC 17.58
Rocker Ratio 1.00 0.350 56.6 82.7 ATDC 40.7 BBDC 10.35
0.374 --- PEAK LIFT ---
Opening
The highest peak opening acceleration rates are; '458' at 0.000345 in/degree^2 and the 748RS at 0.000334 in/degree^2
The chart below has the green cursor set at the peak lift of the '458' cam. Both the opening and closing accelerations are close to one another.
In the middle; Strada, the 748R, and the 916SPS are between 0.000302 and 0.000284 in/degree^2.
At the bottom; the 748SPS is 0.000264 in/degree^2, and the 'G' is 0.000236 in/degree^2. This Cam Pro Plus software is far superior to the old Cam Doctor stuff. It gives values rather than just relative graphs, and it allows one to look at more than two lobes simultaneously. This has pointed out to me that the 'G' cam isn't the acceleration 'bad-guy' that I have thought.
.
Closing
Again the 748RS with 0.000383 in/degree^2', and the 458' at 0.000369 in/degree^2 are the winners. (See three charts prev.)
The middle group consists of everything else except the Strada. They go from 0.000269 in/degree^2 to 0.000316 in/degree^2. (Two previous charts.)
The strada inlet has the laziest closing accel. rate at 0.000208 in/degree^2. (middle chart of the previous three.)
De-acceleration across the peak lift
The 'G' cam has the lowest, and most even, de-cel of any of the cams. Having the longest duration helps.
All of the inlets (along with the acceleration traces) are on the first chart. It gets a little confusing unless you can turn them on and off as you view different areas.
Exhausts
Below is a chart of all of the 4-valve exhaust cams I have measured. Again, too confusing.
One thing that does stand out is the acceleration of the 748RS cams (orange.)
-------------------------------------------------------------------------------- CAM PRO PLUS Valve Lift Report 9:21:49 PM 5/10/2001 --------------------------------------------------------------------------------
C:\My Documents\Cams\916spsex.CPP
LIFT DUR. OPEN CLOSE AREA
Lobe E1 ----- ----- ---------- ---------- ------
Centerline 120.0 BTDC 0.006 307.7 86.9 BBDC 40.8 ATDC 33.95
.050 Lift C/L 113.9 BTDC 0.020 280.6 73.8 BBDC 26.8 ATDC 33.79
Runout 0.00050 0.050 252.2 60.0 BBDC 12.2 ATDC 33.31
Peak Open Acc. 0.000329 0.100 221.2 45.1 BBDC 3.9 BTDC 32.17
Peak Nose Acc. -0.000295 0.150 196.8 33.5 BBDC 16.6 BTDC 30.65
Peak Close Acc. 0.000291 0.200 174.3 22.9 BBDC 28.6 BTDC 28.68
Lift @ TDC 0.0864 0.250 151.0 12.0 BBDC 41.0 BTDC 26.06
Valve Lash 0.0000 0.300 123.9 0.7 ABDC 55.4 BTDC 22.32
Rocker Ratio 1.00 0.350 86.2 18.4 ABDC 75.4 BTDC 16.16
0.384 --- PEAK LIFT ---
C:\My Documents\Cams\748Rex.CPP
LIFT DUR. OPEN CLOSE AREA
Lobe E1 ----- ----- ---------- ---------- ------
Centerline 110.0 BTDC 0.006 348.6 103.3 BBDC 65.3 ATDC 37.98
.050 Lift C/L 110.4 BTDC 0.020 301.7 81.0 BBDC 40.7 ATDC 37.73
Runout 0.00080 0.050 269.7 65.2 BBDC 24.5 ATDC 37.19
Peak Open Acc. 0.000301 0.100 236.7 48.8 BBDC 7.9 ATDC 35.98
Peak Nose Acc. -0.000259 0.150 211.2 36.0 BBDC 4.9 BTDC 34.39
Peak Close Acc. 0.000285 0.200 187.7 24.3 BBDC 16.6 BTDC 32.34
Lift @ TDC 0.1301 0.250 164.2 12.5 BBDC 28.2 BTDC 29.70
Valve Lash 0.0000 0.300 138.5 0.5 ABDC 41.0 BTDC 26.15
Rocker Ratio 1.00 0.350 106.7 16.5 ABDC 56.8 BTDC 20.97
0.400 51.4 44.4 ABDC 84.3 BTDC 10.48
0.412 --- PEAK LIFT ---
-------------------------------------------------------------------------------- CAM PRO PLUS Valve Lift Report 9:22:14 PM 5/10/2001 --------------------------------------------------------------------------------
C:\My Documents\Cams\748RSex.CPP
LIFT DUR. OPEN CLOSE AREA
Lobe E1 ----- ----- ---------- ---------- ------
Centerline 113.0 BTDC 0.006 338.5 102.2 BBDC 56.3 ATDC 41.30
.050 Lift C/L 113.2 BTDC 0.020 310.4 88.3 BBDC 42.1 ATDC 41.13
Runout 0.00130 0.050 284.4 75.4 BBDC 29.0 ATDC 40.66
Peak Open Acc. 0.000385 0.100 256.3 61.3 BBDC 15.0 ATDC 39.57
Peak Nose Acc. -0.000211 0.150 232.6 49.9 BBDC 2.7 ATDC 38.05
Peak Close Acc. 0.000382 0.200 208.8 38.0 BBDC 9.1 BTDC 35.91
Lift @ TDC 0.1610 0.250 184.9 25.8 BBDC 20.9 BTDC 33.42
Valve Lash 0.0000 0.300 156.7 11.6 BBDC 34.9 BTDC 29.53
Rocker Ratio 1.00 0.350 119.9 6.9 ABDC 53.2 BTDC 23.18
0.400 55.4 39.3 ABDC 85.3 BTDC 10.92
0.413 --- PEAK LIFT ---
C:\My Documents\Cams\748SPSex.CPP
LIFT DUR. OPEN CLOSE AREA
Lobe E1 ----- ----- ---------- ---------- ------
Centerline 115.0 BTDC 0.006 351.5 113.8 BBDC 57.7 ATDC 35.18
.050 Lift C/L 117.3 BTDC 0.020 323.4 99.5 BBDC 43.9 ATDC 35.01
Runout 0.00030 0.050 290.0 82.3 BBDC 27.7 ATDC 34.44
Peak Open Acc. 0.000209 0.100 252.6 63.3 BBDC 9.3 ATDC 33.06
Peak Nose Acc. -0.000163 0.150 220.4 47.1 BBDC 6.7 BTDC 31.06
Peak Close Acc. 0.000225 0.200 188.5 31.2 BBDC 22.6 BTDC 28.27
Lift @ TDC 0.1288 0.250 153.4 13.3 BBDC 39.9 BTDC 24.04
Valve Lash 0.0000 0.300 108.0 10.9 ABDC 61.2 BTDC 17.72
Rocker Ratio 1.00 0.350 13.3 57.9 ABDC 108.8 BTDC 2.33
0.351 --- PEAK LIFT ---
-------------------------------------------------------------------------------- CAM PRO PLUS Valve Lift Report 9:22:35 PM 5/10/2001 --------------------------------------------------------------------------------
C:\My Documents\Cams\Aexhaust.CPP
LIFT DUR. OPEN CLOSE AREA
Lobe E1 ----- ----- ---------- ---------- ------
Centerline 115.0 BTDC 0.006 346.9 110.7 BBDC 56.2 ATDC 34.81
.050 Lift C/L 118.1 BTDC 0.020 320.5 98.1 BBDC 42.4 ATDC 34.63
Runout 0.00170 0.050 287.8 82.0 BBDC 25.8 ATDC 34.10
Peak Open Acc. 0.000210 0.100 250.7 63.1 BBDC 7.6 ATDC 32.73
Peak Nose Acc. -0.000179 0.150 219.2 47.1 BBDC 7.8 BTDC 30.62
Peak Close Acc. 0.000226 0.200 187.5 30.7 BBDC 23.3 BTDC 27.78
Lift @ TDC 0.1238 0.250 151.4 11.6 BBDC 40.2 BTDC 23.91
Valve Lash 0.0000 0.300 106.8 12.1 ABDC 61.1 BTDC 17.45
Rocker Ratio 1.00 0.349 --- PEAK LIFT ---
C:\My Documents\Cams\gexhaust.CPP
LIFT DUR. OPEN CLOSE AREA
Lobe E1 ----- ----- ---------- ---------- ------
Centerline 115.0 BTDC 0.006 346.5 111.8 BBDC 54.7 ATDC 39.29
.050 Lift C/L 118.8 BTDC 0.020 319.0 98.3 BBDC 40.7 ATDC 39.11
Runout 0.00090 0.050 287.0 82.3 BBDC 24.7 ATDC 38.53
Peak Open Acc. 0.000226 0.100 251.8 64.1 BBDC 7.7 ATDC 37.29
Peak Nose Acc. -0.000219 0.150 223.5 49.5 BBDC 6.0 BTDC 35.38
Peak Close Acc. 0.000271 0.200 196.9 35.9 BBDC 19.0 BTDC 33.20
Lift @ TDC 0.1274 0.250 169.5 22.0 BBDC 32.4 BTDC 30.12
Valve Lash 0.0000 0.300 139.3 6.3 BBDC 47.0 BTDC 25.64
Rocker Ratio 1.00 0.350 101.5 13.4 ABDC 65.1 BTDC 19.44
0.400 41.5 44.4 ABDC 94.1 BTDC 8.43
0.410 --- PEAK LIFT ---
-------------------------------------------------------------------------------- CAM PRO PLUS Valve Lift Report 9:22:52 PM 5/10/2001 --------------------------------------------------------------------------------
C:\My Documents\Cams\stradaex.CPP
LIFT DUR. OPEN CLOSE AREA
Lobe E1 ----- ----- ---------- ---------- ------
Centerline 112.0 BTDC 0.006 320.7 97.3 BBDC 43.5 ATDC 29.46
.050 Lift C/L 120.0 BTDC 0.020 286.7 82.5 BBDC 24.1 ATDC 29.25
Runout 0.00040 0.050 253.1 66.6 BBDC 6.5 ATDC 28.69
Peak Open Acc. 0.000243 0.100 215.9 47.0 BBDC 11.1 BTDC 27.32
Peak Nose Acc. -0.000231 0.150 185.3 30.3 BBDC 25.0 BTDC 25.42
Peak Close Acc. 0.000273 0.200 156.0 14.2 BBDC 38.2 BTDC 22.85
Lift @ TDC 0.0664 0.250 123.6 3.5 ABDC 52.9 BTDC 19.19
Valve Lash 0.0000 0.300 82.6 25.3 ABDC 72.1 BTDC 13.52
Rocker Ratio 1.00 0.341 --- PEAK LIFT ---
It is difficult to say if the 748SPS exhaust and SP2-3-4 exhaust are intended to be the same but they don't appear to be identical.
Below is the chart of the two of them.
The step in the acceleration curve is on the opening of the 748SPS and the closing of the SP (FBF refers to it as the 'A'.)
The two are very close.
The next chart shows the Strada exhaust and the 'A' (red trace.) The lowest acceleration rates occur with the 'A' (and the 748SPS.)
Next we add the 'G' to the 'A' and see that they are pretty close, and the Strada exhaust has the same closing acceleration as the 'G'.
The next step up in acceleration comes with the 916SPS and 748R exhaust cams. Below they are shown with the 'A' exhaust.
The 916SPS has a little higher opening acceleration that the 748R, but it probably operates at an lower average RPM. (understatement!?!)
The de-acceleration at max lift is greater with the 916SPS and 748R.
And, finally, the 748RS exhaust.
The chart below shows the 1999 SBK cams compared to the Strada cams.
One unique feature of the Strada cams is their assymetry. The inlet opens faster than it closes and the exhaust opens slower than it closes.
Below is a comparison chart of the 748RS and Strada.
Conclusions;
It's appears to me that there was a point in Ducati's Superbike history where they decided that there was no point in making a valve train that would out-last the crankcases, and they 'stepped-up' to the post 'G' generation of inlet cam.
If any of you want more charts, just ask. I can put the timing at whatever points you would like too.