Aprilia RSV-R (early) with Akrapovic 2-2 Race system and Evo Air box  - Written 03/08

Summary: ’03 model RSV-R previously fitted with Akrapovic 2-2 Race system dynod before and after fitment of Evoluzione airbox and ’98 airbox inlet snorkel.

This bike came in with the Akra system fitted and running the Aprilia Evo kit eprom (2-1 std header kit) # 8796495.  I did some baseline runs with this eprom fitted and with another eprom that as sent to me as a Factory Pro eprom.  While I don’t doubt that it is a Factory Pro eprom of some sort, which variation it is I don’t know.  So in fairness to Marc, and not wishing to misrepresent his work in any way, you need to be clear on the unknown bit.  We’ll simply call it the FPRSV eprom and leave it at that.  I was simply after a comparison to the Aprilia eprom, and I had this one available.

For those that are asking why I didn’t try one of Gabro’s eproms – it arrived the day after I did these runs, so unfortunately we missed using it.

I also rigged up a little joiner so I could run both eproms with the “de-restriction wire” both joined and cut.  As it turns out, there’s not much difference, and having had a look at the FPRSV eprom maps there would appear to be a very simple reason why – they’re the same.

I’m not sure if the Aprilia 8796495 eprom has the same maps or not, but they both gave very close fuelling.  There was a little power difference between the runs, but often turning the bike off and then restarting it (even for a short time, as I did when connecting or disconnecting the wire) or even a long series of runs will result in a tiny bit more power.  If I’m doing a long series of runs without turning the bike off I often make the last run the same as the first run these days, just to see if the output has changed.

Sometimes there can be a few hp variation, with the last run the best.  For that reason I also try to make my ‘compare to last dyno session’ runs the first ones I do, just so there’s the consistency of method and hopefully repeatability in the result.

One of the main changes with the Factory Pro eproms is modified spark maps, with ignition timing advanced.  In the before session it made a little more power than the 8796495 eprom, as shown below.  Power first, then torque and air/fuel.  8796495 eprom I green, FPRSV is red.

Given both these eproms are intended for the original 2-1 headers the fuelling is remarkable even.  I’ve been told the 2-2 boosts midrange more than top end, so I was expecting to see some leanness there.  You’ll also see that both eproms are too rich – I’ve also been told that fuel pressure can vary quite a lot with these bikes across model years, and it is something I didn’t check on this bike.  If we do remap it later we’ll do so then.

One thing I did notice (as is expected) with the FPRSV eprom is that the idle speed went up quite a lot.  As I was just running it on the dyno I didn’t bother changing anything to compensate though.

Then I fitted the Evoluzione airbox kit and early model airbox inlet snorkel and ran the tests again.  The first graphs below are with the 8796495 eprom, before in green, after in red.  Again, power first, then torque and air/fuel.  As expected, more torque and power across the whole RPM range, and leaner air/fuel due to the fact we’ve done nothing to the fuelling.

The leanness I was expecting due to the midrange improvements the 2-2 exhaust system give over the 2-1 the eprom was designed for is somewhat apparent here.  Below 5,000 and above 8,000 RPM the air/fuel is quite flat, with a lean swing from 5 to 8,000 RPM that peaks around 6,000 RPM.  Given the air/fuel trace on this dyno usually has a lag of around 500 RPM, this corresponds to 4,500 and 7,500 RPM on the road.  This sounds about right from what I’ve been told and what I’ve felt, especially on earlier Tuono models that really come on around 7,500 RPM.

Next, the graphs for the FPRSV eprom, before in green, after in red.  Again, power first, then torque and air/fuel.  Again, more torque and power across the whole RPM range, but not as much as before.  And rather surprisingly, a slightly richer air/fuel.  No idea why.  Although I did notice that the air/fuel curve with the FPRSV eprom did tend to drop with consecutive runs, stabilising after 3 or 4.  The Aprilia 8796495 eprom didn’t do this, or at least not so much as to make it a noticeable trend.   Again, no idea why.

The next thing I did was to test what I’d been told with regard to the operation of the idle trimmers – the adjustable pots on the front of the ECU that allow you to adjust the idle mixture.  This was also based on a somewhat poor result I’d had tuning an RSV some months earlier, where I had suspicions about the trimmers being an influence in that result.  From what I’ve been told or read, the trimmers affect the mixture up to about 4,000 RPM at WOT and not above.  I decided to test this, which I did by simply winding both the trimmers to full lean and then back to full rich with a couple of runs at each setting.

The results, compared to the previous runs where one trimmer was approximately 45 degrees lean and the other approximately 80 degrees rich (out of 140 or so possible degrees of travel either side of the mid point) are shown below.  As was is green, full lean is red and full rich is blue.  The runs were done consecutively with the Aprilia 8796495 eprom without turning the ignition off.  Power first, then torque and air/fuel.

A very clear result, from which I would conclude that, unless you test and prove otherwise, it’s safe (or just best) to assume that, for an eprom with the idle trimmers enabled, the idle trimmers can and do affect the mixture over the whole RPM range.

Next I tried some trumpet extensions.  I had made some up for the later model bikes with 57mm throttle bodies as the RSVR trumpets are 30mm shorter than the Tuono trumpets, being 20mm and 50mm above airbox base level respectively.  On the early 51mm throttle body bikes the trumpets are all the same 50mm length, meaning I ran these tests with trumpets extended 30mm to 80mm above airbox base level.  The extensions are simply aluminium tubes with the required ID and OD, along with some longer screws and four little extension tubes for the screw supports

I set the trimmers back to where they were previously for these runs, and the results are probably clouded somewhat by the rich mixture, as excessive richness on a Dynojet dyno (as shown by the previous graphs) impacts the top end more than the midrange in my experience.  I should have wound the trimmers back a bit, but didn’t think of it at the time.  Ideally, I would have run a sample out of each header pipe and set the trimmers as required (for best compromise) based on that, but again, time and (much more likely) organisation weren’t my best friends that day.

And the changes in the air/fuel are always a good indication of actual changes to the air flow – richness means less air moving through, leaner means more.  Although the different trumpet lengths move the volumetric efficiency and hence torque curve peaks around a bit, which compounds the tuning changes somewhat.  You can see that more clearly in the power curve.  On the road with the trumpets extended you could feel the lumps in the power curve, whereas without the extensions the delivery was much more consistant.

I wouldn’t call this result a bad one however, I’d call it a more work required one.  As in tuning required to suit, which is always the most important step.

Anyway, green is std trumpets, red is extensions fitted.  Power first, then torque and air/fuel.

Hopefully we’ll get to finish this bike off in the future with cam timing changes and then tune it as required.  We’ll do that using eprom modification info and software from Duane Mitchell at Ultimap, with a fair bit of input from Gabro as well.

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