S4engineupgradepage2

Configuration 3

The planning for this upgrade started during the summer of 2004 as I started to get more interested in tuning Ducati engines. I tried to understand what the tuners knows since many years and I was only guessing. I was reading a lot and tried to sort it out in a not so expensive way. I realized that one of the main Hp killer on a S4 are the headers. They are 40mm just like on the 851 and the 888. This might be okay if you have 90hp or so but if you want more it is just to small. All 748/916/996 strada and Bp are running 45 mm headers. It is the same thing for the ST4 and St4S. They are running 45mm headers. It might not sound much to go from 40mm to 45mm as the diameter only increases with 12,5% but the area is increasing with 26,5%. This means that if you have an engine with standard 40mm headers that produces 100 hp you will have the same gas speed in the headers as an engine that produces 126,5 hp with 45mm headers. That is a big difference. As S4 and ST4 have the same engine and basically the same frame it is an easy swap to ST4 headers. It is just bolt on. The ST4 silencers need a bit of modified to fit as the attachment are different so at the same time as I modefied them I made them 70mm shorter to look a bit nicer.

No. This are not two Cobras figting. S4 40mm header to the left and ST-4 45mm header to the right

S4 to the left ansd St-4 to the right

ST-4 on top of S4 header

The next thing that is obvious are the cam shafts. It is nothing wrong with them. They are not bad or any thing. They are just old technology. All standard (not SP or SPS) desmo quattros from 851 up to 996 are running the same A1 camshafts. They are designed in the mid eighties. The first bike to receive some more modern “high lift/short duration” cams were 916/996SPS. Next one to get modern cams was 748R. Finally the standard bikes received an update and these bikes are S4, ST4S and S4R. The camshafts on these bikes are identical to the standard A1 except for inlet that is closing 10 degrees earlier and have 10 degrees shorter duration. Most tuners updates the cam timing on the standard A1 cams by advancing the inlet by 10 degrees and the result is about the same as S4 cams at factory spec so the S4 cams are not a revolution. They are not bad but....................

This means that I needed new camshaft. I had two interesting options. One option was 996 SPS cams. This are very nice cams that are not to aggressive to the cam train. This cams gives good power that holds on nicely at high RPM and still produces a nice midrange. SPS cams are much nicer cams then the older SP cams that have less lift and longer duration. The second option was Vee Two that makes a nice combination with inlets similar to 748R and exhaust similar to 996SPS. This cams are the thing to have performance wise as the inlet are higher lift and shorter duration compared to 996SPS cams. This means power similar to SPS but with better midrange. The problem is that they are very aggressive to the cam train and they are also expensive. 996SPS cams you can pick up at Ebay for a good price. As I am a tight bastard I selected 996SPS cams.

T1 = 996 SPS cams

This ones will retire at a young age

Look. I have full kit of T1 cams

S4 specifications are like this.
Intake opening 11 degrees btdc
Intake closing 60 degrees abdc
Intake duration 251 degrees
Intake lift 9,6mm
Exhaust opening 62 degrees bbdc
Exhaust closing 18 degrees atdc
Exhaust duration 260

The specifications are like this with standard 119,5/107 timing.
Intake opening 14 degrees btdc
Intake closing 73 degrees abdc
Intake duration 266 degrees
Intake lift 10,8mm
Exhaust opening 57 degrees bbdc
Exhaust closing 23 degrees atdc
Exhaust duration 260
Exhaust Lift 9,8

The specifications a la Brad Black are like this. 107/107 timing.
Intake opening 26,5 degrees btdc
Intake closing 60,5 degrees abdc
Intake duration 266 degrees
Intake lift 10,8mm (9,6)
Exhaust opening 57 degrees bbdc
Exhaust closing 23 degrees atdc
Exhaust duration 260
Exhaust Lift 9,8

It is not a huge difference in cam timing but it looks like the 996SPS cams are just what this engine need especially when they are used with Brads timing. They need that extra lift and that little extra duration. The next interesting thing is to look at the closing of the inlet and compare 107/107 SPS to the S4. It is a copy and past in timing. Look at the exhaust. It is also almost a copy and past. This thing is what Brad has been using for a long time before Ducati came with the “new S4” cams.

At the same time as I installed the camshaft and shimmed the valves I also checked the squish and set it to 1mm. What this does is to make sure that the piston and the cylinder head just about makes contact at max RPM. When it is just about contact the fuel / air mixture are “squished” into the centre of the combustion chamber and this gives more power and at the same time it reduces the risk of pinging. For more explinations about squish have a look at Sigma Performances or
Brad Black at Moto-Ones excelent page.

When the squishing was done I adjusted the cam timing to Brad Blacks (again) specification.

I set it to 107/107. This means that inlet is in the centre of the opening at 107 degrees after top dead centre and the exhaust is in the centre of the opening at 107 degrees before to dead centre. Standard 996SPS setting is 119,5/107 so it is a big difference. This timing might loose one or two hp at top but it will gain a lot off midrange and I like midrange.

The last thing to go one was a lightened flywheel just to make the engine spin up a bit faster.

Power and TRQ. Notice the big dip in TRQ at 6000 RPM. A result of the ST-4 exhaust I think

Power and mixture. As you can see it is a bit an the rich side. I would like to have 13/1 mixture

Same one in a strange format

Power is now 111hp or 12% up. It is a bit lower than I was hoping for as I expected 114hp but as you can see she is running a bit rich. The target was a mixture of 13/1 Air/Fuel but for some reason it ended up at 12/1. I think it would be 113 or 114hp with 13/1 mixture. It is a bit funny because when I run the bike at the road the mixture is spot on 13/1 indicated. I dont know. Maybe my "open airbox" installation creates some kind of ram air effect when I am riding the bike at high speed and is leaning out the mixture or if it is just that my Lambda reader has an erratic reading. I have to check this out. The performance gain does not look huge but the difference in feeling when you ride it is very big. One reason for this "Ohh my god she pulls so much stronger feeling" is of course due the TRQ dip at 6000 RPM. It looks like this is a result of the ST4 headers. It looks like Brad Black had the same thing on his bikes when he tried ST-4 headers at his 851 and 888. Take a look and compare.

Power commander map part 1

Power commander map part 2

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