Dyno-Tuning an Aprilia Caponord
The Test Ride!
In September of 2001, I got the opportunity to ride the first Aprilia Caponord brought to the U.S. for the motorcycle magazines to road test. CityBike's riders finished their testing on a Monday evening, and it wasn't due back to the dealer until Friday. I put over 1000 miles on the Caponord during that time and FELL IN LUST with it!
I owned a Honda VTR1000F (SuperHawk) at the time and was impressed that the Caponord was just as power-wheelie prone as the VTR. It also handled very well to be ~90 lbs. heavier than the VTR. The ergonomics and wind protection were very good for me. I've always preferred the throb of a v-twin to the buzz of the popular inline-4s we get in America. When I returned the Caponord to Scuderia West, I gave them a deposit for one of my very own.
Christmas in April!
I bought the 1st silver Caponord delivered in April 2002. It is an enjoyable & unique motorcycle. Very similar to my previous favorite motorcycle, my 1983 Honda CX650Turbo. However, the Caponord is not without what some folks refer to as Italian "character". This story is about the character who lives in my Caponord's engine-control unit (ECU) and his interesting maps.
My Caponord is different than the test model I rode in 2001. The 2002 & later models that ship to the U.S. have an oxygen sensor & catalytic converters upstream of the mufflers. Also, a charcoal canister and associated emissions plumbing. And as I was later to learn, very different ECU mapping. Mine got poor fuel mileage, 29-42 mpg(usa) as I normally rode. It ran very rich at some rpms & part-throttle positions, and very rough in others. As the miles accumulated over the years, some of the rough spots became rougher yet and the motor started pinging there. On premium gasoline. The later oem maps did not change these issues. I feared it was so rich in places that it was building carbon deposits in the combustion chambers.
It was NOT as wheelie-prone as the test bike neither. After hanging out at a couple of the Caponord forums on the net, I learned about the Tuneboy/TuneEdit software. Aprilia uses a Sagem MC1000 flash-programmable ECU on the Caponord & the Futura. TuneEdit allowed full access to all fuel, ignition, air/fuel ratio, warm-up, & idle maps via a serial/USB cable & your laptop. The datalogger software, also included, allowed recording of real-time ECU data during road testing or dyno runs for later analysis.
Awakening my Caponord...
I replaced the oem cats & exhausts with Staintunes (with the noise silencers installed), and removed the intake snorkel in the airbox. These modifications should allow the motor to breath a little better, and not annoy my neighbors too bad. Bought the TuneBoy+TuneEdit software. Spent many hours looking at the differences between the various Aprilia-supplied maps and learning how TuneBoy said the ECU used them. I loaded each of the different available maps and did some road testing with the datalogger running on the laptop on the seat behind me.
As stated in the TuneEdit manual, the fuel maps are actually air-mass maps. They indicate how many milligrams of air should be arriving to that cylinder at that RPM & throttle position. The ECU then corrects these values based on airbox pressure & temperature, calculates load, & then uses load vs. rpm in the Air/Fuel Ratio map to get the target Air/fuel ratio. Then it finally calculates how much fuel should be injected, realtime.
I selected the 050429 base program and fuel maps as my starting point for dyno tuning. This program kept the oxygen sensor active for data-logging, but removed the charcoal canister purge-control valve from being required by the ECU. This allowed me to do a complete canisterectomy without getting an EFI error code about the now missing purge control valve.
The ignition and air/fuel ratio maps are not throttle position(TPS) vs. RPM like the fuel maps; they are "Load" vs RPM. Load is calculated in the ECU program, but Wayne at TuneBoy didn't decode (reverse-engineer) the algorithm from the many different programs he has looked at. We had many discussions about my dyno results and here is my SWAG (scientific wild-ass guess) based on my ECU data acquisition during dyno runs;
Load(RPM) = ((Fuel1+Fuel2 at TPS & RPM) / Max(Fuel1+Fuel2)) + (temp.& press. correction)
Max(Fuel1+Fuel2) would be the maximum SUM of the two wherever that occurs on the maps.
So, at high RPM, %Load is very roughly %TPS; but at very low RPMs 50% Load can occur with as little as 13-20% TPS. It also means that at say 2900 RPM, the load will never exceed ~75-80%. Yes, there are areas in the ignition maps that the Caponord is not capable of getting into; even on an eddy-current dyno.
The original (2001) Caponord map file #790329 had one ignition map and no ignition-limit map. All subsequent Caponord maps have both. The 790329 ignition map has a lot of advance at low-mid RPMs and hi loads, but only peaked at 24.4deg at 9000RPM & 100% load.
The current Caponord maps (050428, 050429, 051123,) all have the same ignition map & ignition-limit map. This ignition map has much less advance at low-mid RPMs and hi-loads; but peaks out at 30deg at 9000RPM & 100% load. 5.6 degrees more advance at 9000, but 12 degrees less at 3500rpm than the 790329 map. Hmmm... optimized up high, but neutered down low.
The Futura ignition map has more advance at lower RPMs (like the Capo 790329) and more advance at higher RPMs (like the Capo 050428, etc...).
I decided to transpose the Futura ignition map values into the Caponord 050429 map as my starting point for the dyno work.
The ignition-limit map, according to the TuneEdit software manual, is used to limit the calculated ignition advance. The ECU reads the base ignition map, calculates & adds in corrections based on air pressure, temp, etc and then uses the ignition limit map to prevent over-corrections. If the calculated value is larger than the limit value, use the limit value. If this were correct, then the current Caponords would only be running 4.4deg advance from 6000-9000RPM at 100% load. My dyno measurements did NOT confirm this. The actual ignition advance used was always more than the base ignition map value. So, then I assumed the limit map was only applied to the calculated corrections, before adding to the base map values. To test this, I changed the ignition-limit map to all ZEROs. We did not see any change in the actual timing used or measured torque while on the dyno. My speculation is that Aprilia tried to use the ignition limit maps during their tuning, experienced some problem(s), and disabled its use in the supplied map files.
After discovering the worthlessness of the ignition-limit map in these Caponord tunes, I returned them to the oem values & left them alone. This does not mean that these limit maps are ignored in Aprilia Futuras, or any of the other motorcycle's Sagem MC1000 ECU. The software program running in the ECU determines what or if the limit map is used. I only tested this with the Caponord 050429 map.
Air/Fuel Ratio Maps
If the fuel (air-mass) maps are correct for the motor, then the Air/Fuel Ratio map is where you would make adjustments to get peak power, better fuel economy, and improve throttle response. This is also where the closed-loop mode can be enabled. Most dyno shops with a 4 or 5-gas exhaust analyzer use the CO (carbon monoxide) measurement to tell how lean/rich a motor is running. This is the equivalent of the Air/Fuel Ratio and a CO-to-AFR conversion can be found here.
For the sake of emissions & fuel-economy, you want CO to be minimal (< 1%); but peak horsepower is usually with CO = 4-5%. As I have learned during this tuning process, good throttle response at low RPMs requires a CO of 3% or more.
Here is the Air/Fuel Ratio map in the current Caponord maps (050428, 050429) that are used in a Caponord with an oxygen sensor. Closed-loop mode in these ECUs is only enabled where the AFR is set to 14.5. I have colored those cells green. Set above or below 14.5, and its open-loop only. With stock gearing (17t CS sprocket & in 6th gear), the 2500-3500 RPM range is ~43-60 mph. Above 60 mph, it can't go closed loop on the oxygen sensor.
During early road testing I experimented with setting cells to 14.5 up through 5000 RPM (>80 mph), and loads up to 41%. This dramatically improved my fuel economy while cruising in the 60-80mph range, so I knew the oem fuel mapping at part throttle was very rich for my Capo. However, while in closed-loop mode and during throttle changes that transitioned from closed-loop back to open-loop, the throttle response was very poor. It sucked! I knew I wanted the fuel maps corrected and to disable closed-loop mode entirely. I suspect Aprilia could improve their closed-loop algorithm if they wanted to.
On the Dyno...
We did several dyno-testing sessions with a 4-gas exhaust gas analyzer, made map corrections, and many days of road testing between sessions. Actually, this took several months. Dyno-tuning with marginal air flow around a Caponord can cause some unique problems.
During the 1st session, we had to use a large spray bottle of water on the radiator to help control engine coolant temperatures. Their fans worked ok at low RPMs and loads. When we were testing at 30 Hp and higher though, sprayed water and long idle times between runs were required to cool it back down to normal operating temperatures. Afterwards, I learned that my new voltage regulator had over-heated and didn't regulate very well anymore. It was replaced under warranty.
On the subsequent dyno runs the radiator and voltage regulator both got fans pointed at them AND sprayed with water. Between the 2nd & 3rd dyno sessions, BRG Racing moved their shop to a different building. They hired an engineering consulting firm to design their dyno room correctly. It was two and half months before the dyno was available again. The dyno room had better air flow in general to bring fresh air in and suck the exhaust out, but they still have marginal directed fans to position at the radiator and other specific locations.
On the 1st ride after the last dyno run, the hi-pressure oem plastic-fuel connector (2nd one, less than 1-year old) started leaking fuel. It didn't break or come loose. It was fully seated. The o-ring looked fine. It just leaked now. I suspect the outer shell over-heated and expanded from the 60 psi fuel pressure on the inside. The metal connectors were ordered and installed.
I wish I had video footage of the Caponord on the dyno. At certain low RPMs and loads, the drive chain is excited into its natural resonant frequency. It will oscillate violently, slapping the lower chain guide and the bottom of the swingarm. This is a VERY LOUD noise! This can get so bad that the rear suspension can't cope and the oscillations go into the whole rear of the bike. The plastic rear fender can flap so far that it will slap the rear tire! I asked BRG if they had ever seen this before, and they said, "Sure, all Aprilias do that!" D'OH!!!
Correcting the Fuel (Air-Mass) Maps
To correct the fuel maps while monitoring the CO in the exhaust, it became obvious that I wanted the target air/fuel ratio to be the same under all test conditions. This would help make testing simple as I wouldn't need to record the load values to understand what CO reading to expect. With load changing with RPM and throttle position, you get different target air/fuel ratios with the oem maps. I needed a "test" air/fuel ratio map with the same value everywhere to eliminate this variable.
So I created a test air/fuel ratio map with all cells set to 13.8, and then we had an expected CO target of ~2% for all measurements. The sniffer for the analyzer was attached to the cylinder-1 port and we attempted to test all 16 throttle positions from 1800 to 9250 RPMs; the actual control points in the fuel maps. Then we repeated the testing with the sniffer in cylinder-2 port. During testing, we saw CO measurements ranging from as low as 0.2% to as high as 11%!
Some fuel-map points were not accessible. At 1800 & 2000 RPMs initially, we couldn't get above a TPS value of 28% as the motor would ping. Too much ignition advance. We would need to lower the ignition advance values in these areas to get CO readings. Testing at RPMs above 5000, we could not get steady-state RPMs at small throttle openings (<13%) as the dyno's control system wouldn't sync RPM with that little torque at that high RPM.
There were also some test points where the drive chain oscillation was so severe that we were afraid the Caponord was going to JUMP off the dyno! No pinging at those points, but the ignition advance was too much there to test in steady-state conditions. Remember, I started with the more-advanced Futura ignition map settings.
I took this data home for analysis. The CO reading were converted to air/fuel ratio (AFR). The percent difference between the measured AFR to the expected AFR of 13.8 at any given point, was the percent change required in the Fuel map to correct that point. In theory anyway.
All of the accessed points in both fuel maps were corrected. The second session was a repeat of the first, but with lowered ignition map points (subtracted 4 degrees) where we couldn't reach before. The low RPM points were reached this time and the others were re-tested for verification. Some required minor 2nd tweaks to get the CO to the range of 1.8-2.2%.
The 3 lowest RPMs (1150, 1340, & 1450) were only tested at a couple of throttle positions. Again, either the motor pinged or the Caponord was a bit too animated on the dyno to go higher in TPS.
Even with the test AFR map of 13.8 loaded, the Caponord ran much better in the low-to-mid RPM range.
The EXCEL data graph below shows the relative error in the OEM 050429 fuel-1 map vs. the corrected values on my Caponord (with Staintunes, etc...). Its quite shocking that it could be that different. I suspect & hope most Caponords flow like the OEM maps, but mine did NOT!
Speculation: The lean regions at 40-100% TPS are mostly differences in the rpm-related resonances in my engine vs. oem; the air box, exhaust, etc. The VERY rich regions at small throttle openings would mean my throttle position sensor does NOT have the same linearity as the oem reference as the errors are fairly consistent across the same throttle position(s) at all RPMs.
There are no linearity specifications or test procedures for the TPS, so it could be pretty bad and your Aprilia service department won't have a clue.
I took a 5500-mile trip on the Caponord after the fuel-map corrections (2nd dyno session). I created two test maps for this trip; (1) corrected fuel maps with the de-pinged Futura ignition map, and (2) corrected fuel maps with the original Caponord 050429 ignition map. With the laptop in the top box, I changed maps every morning to compare the two during my travels.
It was hard to tell which map was loaded above 6000 RPM. Both felt pretty good. Between 2500 & 6000 RPM, the Futura map was WAY stronger! The Capo ignition map had definitely been neutered in that range. Below 2500 RPM, the futura ignition map felt like it had too much advance, and the Caponord felt like it had to little.
My # 1 ignition coil died during this trip. Afterwards with the Futura ignition map loaded, the motor pinged at low RPMs & high loads where it was rough before. It didn't ping with the Capo ignition map. It became obvious why there are 2 spark plugs per cylinder in these motors.
Fuel mileage, withOUT closed-loop mode enabled, was now 40-52mpg!!!
Tuning the Ignition Map
The last two dyno sessions were used to fix the rough spots in the Futura ignition map and optimize it for 87-octane(usa) regular gasoline.
I setup a revised Air/fuel ratio map to provide good fuel economy (AFR=14.20) below 50% load, and then progress up to peak power (AFR=12.80) above 90% load.
The peak Hp optimization was only done at 3000, 6000, & 9500 RPMs at 28, 57, & 100% loads. Ignition advance was stepped up and/or down 2 degrees at a time, until we found the Hp peak for that RPM & Load. The values in between were interpolated & smoothed using similar-sized steps in the Futura ignition map. Values below 3000 RPM were adjusted to provide smooth power with no bucking, pinging, or excessive roughness.
At very low RPMs (2000 RPM & less), the Caponord motor becomes VERY efficient at loads greater than 40%. Much more so than the Futura motor with its cams having more overlap and larger throttle bodies than the Caponord's. Detonation (ping) occurs here with any ignition advance at all. The values you see in this region of my final ignition map were set to provide 4 degrees margin before pinging or excessive roughness, whichever occurred first.
Tuning Low-RPM Air/Fuel Ratio Map
Caponord motors do not like to run lean at low RPMs. They are more prone to stalling, roughness, and pinging. This region is hard to test on an eddy-current dyno. It took many test rides and adjustments to figure out that the CO should be at least 3% (AFR of 13.4 or less) to run smoothly down there. Here is my final Air/Fuel Ratio Map.
Well, that's about it. My resulting maps, tuning specifications, & associated WFO dyno-runs can be see on this page.