S4R  With Cam Timing Reset

This S4R came in to have the cam timing checked and reset.  Given all the S4R (and all other ’03 onward bikes) have adjustable cam pullies std I expected the timing would be pretty close to spec.  Surprisingly it wasn’t.  The specs are 114.5 inlet, 112 exhaust.  This one had inlets at 119 and 120 and exhausts at 106 and 108.

With the shorter duration inlet cams these have and the fact we were not replacing the DP Kit ECU already fitted (same DP power kit as that featured in the other S4R report). I wasn’t keen to venture too far from the std specs.  We ended up using 113/110 centrelines and left it at that.

Unfortunately my assumption that the DP ECU would work at std or close to std specs was a bit off.  We didn’t get to dyno the bike before or after due to time constraints and it went out with the usual balance and idle mixture setting we do as part of any tune job.  When the owner reported that it was a bit rough to ride and felt like it had lost bottom end it all seemed like the usual ‘didn’t get to do it all properly and now it goes bad’ thing.  Especially as losing bottom end is something you don’t normally associate with advancing inlet cams.

So we got it back and took it to the dyno and played with the fuel using the idle trimmer – the only adjustment we have with original 5.9M ECU.  It responded to this at least, and after adding 30 points the owner was happy again.  Set like this the idle is somewhat rich and the fuel consumption has probably gone up, but he hasn’t mentioned that so it can’t be too big an issue.  It certainly goes well in this trim – I’m surprised how hard it keeps pulling at the top end given the shorter inlet cams and 40mm headers.  Hopefully, to finish the job, Duane will get it at some point to fit a U59 to and tune it properly.  I’ll be much happier with that.

For a comparison I’ll put the before tuning and after tuning runs against the bike from the previous “S4R with DP Kit” report.  Green is before tuning, red is after tuning and blue is the bike from the previous report.  If the blue line is representative of how this bike was before then it’s a fairly big difference.  More than I’d expect from 4 to 6 degree cam timing changes really.  There’s 7 or 8 Hp difference at 7,000 and 8,000 RPM.  This bike lifts the front wheel easily on acceleration in second (the std 15/43 gearing certainly helps there) and is overall a fairly quick thing to ride.  Very good fun too.  I was keen to get one of these originally, but am now thankful I didn’t – my licence wouldn’t survive too long.

The first graph is power, then torque.


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