888 With Cams Dialed

Now that I had the base runs and other info I wanted, I debated whether to go for the usual cam timing mods, or fit the big exhaust first. Replacing headers on these models is not my idea of fun (although I did find later you can swap headers on the 888 using air tools only – very cool), so I fought the curiosity and did the cam timing instead. The factory settings were out by 4 and 7 degrees (inlet/exhaust) on the horizontal, and a whopping 11 and 12 degrees on the vertical. A bit of a surprise there, the biggest inconsistency I’ve seen in ‘as delivered’ timing to date. As usual, I didn’t bother trying the std specs first, going straight to my normal reset specs. Well, sort of. The way I did the job was a little different to usual though, going the offset key route due simply to cost reasons. As you should all know by now, I’m a tight arse. Saved myself around $150 by using the offset keys, although I had to change keys on the camshafts and the timing shaft to get the timing I wanted. Much more hassle than the lovely adjustable pullies, but cheaper, and the objective with this bike is to play, clean and sell for a profit. I ended up being a couple of degrees off on all, just because the keys I ordered didn’t end up giving me exactly what I wanted. If we had a stock of offset keys on hand, this would be overcome, but the whole process of using them really does annoy me. Maybe I’m just getting grumpy (grumpier?).

As a side note, the cranking compression increased with the cam dialing job from 125/145 vertical/horizontal before to 165/165 after. Cool (even if it did exaggerate my starting problem drastically). The 12 degree retarded inlet cam on the vertical exhaust certainly robbed quite a bit of cranking compression.

It also effected the running balance, or throttle synchronization. When I started it after I’d done the cam timing, it sounded like it was out of balance. Having done the balance as part of the service, I thought it was just the std mufflers or something making it sound a bit funny. When I fitted the big exhaust I wanted to check the idle mixture to see if it had changed any, and decided that I really should check the balance, as it did sound quite off just as you cracked the throttle. And it was, with the vertical cylinder having quite a bit more vacuum than the horizontal. I can only imagine this is due to the greater cam timing variation on the vertical (the vertical inlet cam was moved quite a bit more than the horizontal) increasing the manifold vacuum with the throttle almost shut. Not something I’d really noticed before, but I check/adjust the balance every time I do a cam dialing job, so probably never had a before/after check like this before to make I obvious.

I also didn’t get to do the "after" runs with the Staintune slip on mufflers. As the bike I borrowed them from was a second handy, it got sold in between the two sets of runs. There were no other carb 900SS hanging around at the time, so I used the Megacycle slip on mufflers from the 600M. Just had them poking out the side at a wacky angle, wired up to stay in place. I’ve always found the Megacycle mufflers to work very well, so wasn’t too concerned about any difference.

The results are shown below. In contrast to the 851, the power hasn’t dropped below the ‘before’ past the peak. I expected this, and contribute it to the bigger valves. As usual, a good result, somewhat exaggerated by the ‘as delivered’ timing being so bad. The increase in torque at the bottom end is always very nice on the road. These 64mm stroke motors are very revvy, particularly when set up well. Changing the cam timing on them seems to give a somewhat ‘faster rev’ feel, as opposed to the ‘more torque’ feel that it does on the bigger engines. This bike also doesn’t have the DP light flywheel that helps make my 851 so excitable, but will be rather nice none the less.

First graph is for std mufflers and airbox lid, the only mods being cam dialing and fuel "rezoning". Green is before, red is after. Improvement of around 7 or so % up to the torque peak at 7,000 RPM, which is about the usual. The fueling required for the best power run was not that different – less than 5% all over - to the fuel required for best power before the cam timing. This is certainly not the usual. The later runs showed the improved air entry of the open airbox lid required the sort of fuel mods I normally expect – up to +15% in the midrange, whereas the addition of slip on mufflers didn’t really cause the need for much further change. Anyway, getting ahead of myself.

Next is std mufflers and open airbox lid. I was interested to see how much difference the std mufflers would make. Their negative effect in the previous report compared to the Staintune slip ons was fairly minimal, so I wanted to see if that transferred with cam timing changes. Green is before cam dialing, red/blue after. The fuel rezoning required, as mentioned above, was more in line with what I normally see. The red/blue ‘after’ run is because I didn’t do a complete ‘after’ run, simply because I was trying to minimise the time taken and it wasn’t that important. The 29 runs I did in this session took over an hour in the dyno room, so I try not to stuff around too much. Again, usual improvement in % terms.

The final set of runs was for the total combo – the one I would usually be working with. Megacycle slip on mufflers, open airbox lid, cams dialed and fuelling rezoned as required. Green is before – with the Staintune mufflers, red is after. I was hoping for 100 Hp, but I think 99.7 is close enough to make the claim. The Megacycles may have contributed to the low end increase a little over the Staintunes, given my experience with them. The increase is up to 10% under 6,000 RPM, so I’m pretty happy with that. Will make it quite a bit quicker on the road.

I included the runs for std mufflers as an idea of how it would effect an otherwise std bike. Given the price for our normal cam dialing job using Vee Two pullies is about the same as for a set of slip on mufflers for these models, I was curious to see how it would go. There was certainly a far greater difference between the std and aftermarket mufflers after the cam dialing. However, keeping the std mufflers with the open airbox lid, cam dialing and fuel rezoning still gave an improvement of over 10% through the bottom end and midrange, dropping to around 4% at the top. On that basis, if there was any one of these mods I would leave for last, it would probably be the mufflers. The growl from the open airbox may not be so apparent to the passer-by (or is that passed-by?), but it is very obvious to the rider, and will make up for any missing exhaust note. I’d even consider the lightweight flywheel (and any gearing changes) before the mufflers too. Personal choice really, and pretty much the reverse of Ducati owner reality, borne out by the current DP catalogues I guess. Lots of pipes, not much else in the way of engine hot up stuff. Which pretty much shows where most owners spend their money, and how unimportant real engine performance is to many.

The next graph shows what I’m talking about. Green is all std, yellow is Staintunes, open airbox lid and rezoned fuel, blue is cams dialed, std mufflers, std airbox lid and rezoned fuel, red is cams dialed, std mufflers, open airbox lid and rezoned fuel. Given the option between slip on mufflers and cam dialing (assuming open airbox lids on both), it’s pretty obvious which will have the most effect on how the bike rides.

So, with the usual mods, this 888 has picked up over 20% in places through the bottom end and midrange, and 6% at the power peak. Here the four mods – open airbox lid, slip on mufflers, cam dialing and fuel rezoning – work together to give a bike far more lively and responsive than the std issue. Comparing the green and red curves below shows the std/after comparison this far. First is power, then torque.

And there’s still the big exhaust to come! We’ve out torqued the 851 SP3 and 888 SP4 so far, hopefully we’ll out power them as well in the next installment. Not bad for a Strada.

The final graph is a torque graph and shows something that I get a lot of enquiries about, and is something many don’t seem to understand. If you change the cam timing (or do any other mods that alter the amount of air flowing through the engine), you need to change the fuel as required. Some see this as an option, but it’s probably the most important step. I get lots of questions about changing mechanical bits, but often the asker is planning to go through their "collection" of chips to see which one works the best. The truth is, if none of the chips you have suit the engine combination you end up with, you’ve wasted lots of time. The perceived cost of proper tuning puts many off too. Amazingly, people will spend thousands on heads and cams and ti rods and big exhausts (don’t get me started on big exhausts), but won’t spend a fraction of that to get it tuned properly. Really, they’d be far better off keeping all the cash in their pockets. Or doing the sensible thing and buying light wheels and good suspension. If you don’t, won’t or can’t carry out the final step of tuning the combination you have or plan to have, my advice don’t bother starting. Some guys are amazingly stubborn about this, and it really frustrates me. I’ve tuned track bikes people have been running for years with obvious improvement, and had them wonder how they were so far off to begin with. Just simple fuel zoning, costing a couple of hundred dollars at most. Probably due to the fact many people can’t tell when a bike isn’t running as well as it should be. If it’s not misfiring, then it’s fine.

The three curves shown are all std in green, the final cams dialed, open airbox lid, Megacycle mufflers and fuel rezoning in red, and the final without any fuel mods – ie, running a std chip – in blue. The problem is rather obvious.

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