This FAQ is in no particular order, so bear with me!
It depends on:
1 - How high you want to rev your engine
2 - How much Horsepower your engine can make, and at what RPM
3 - What your fuel pressure is.
A short discourse on the fuelling question: The total fuel delivery is a function of four things: injector duration, fuel pressure, injector nozzle bore, and number of injectors. Changing any of these things can deliver the same result, within bounds: as the engine RPM increases, the amount of time available for injection decreases, until at high rpm the injectors are switched on all of the time.
The only solution where this is the case is to use two injectors, each of which can then deliver half of the fuel load by turning on together, for half of the total required duration (get it?).
Now take a look at actual durations from three bikes at full
throttle, with the available time for a single injector at the
top:
| Model | 4000 RPM | 5000 RPM | 6000 RPM | 7000 RPM | 8000 RPM | 9000 RPM | 10000 RPM | 11000 RPM | 12000 RPM |
|---|---|---|---|---|---|---|---|---|---|
| Available mS | 30.0 mS | 24.0 mS | 20.0 mS | 17.1 mS | 15.0 mS | 13.3 mS | 12.0 mS | 10.9 mS | 10.0 mS |
| 916 Strada | 9.1 mS | 9.3 mS | 10.6 mS | 11.5 mS | 11.5 mS | 11.8 mS | 11.1 mS | 10.4 mS | rev lim |
| 916 SP | 7.9 mS | 7.3 mS | 10.1 mS | 13.4 mS | 15.0 mS | 12.8 mS | 12.2 mS | 12.4 mS | rev lim |
| 955 Corsa | 14.0 mS | 11.6 mS | 13.5 mS | 11.3 mS | 14.7 mS | 12.1 mS | 13.5 mS | 12.8 mS | 12.1 mS |
At 8000 RPM the Corsa duration is 14.7 mS with only 15.0 mS available. This is possible, but any further time would be impossible if the Corsa was single injector. Again at 10,000 RPM the Corsa duration is 13.5 mS, but there's only 12 mS of time available. Of course, the Corsa uses two injectors, so the 13.5 mS is split into 6.75mS across two injectors.
The same can be seen for the 916SP at 10000 and 11000 RPM. Again, the SP is twin injector so the durations are halved across two injectors.
Also note that the 916 Strada never needs more duration than is available, still with only one injector.
Fine, but figure out how high your engine will rev. We have tested 916 Bipostos with G cams and 54mm headers which make 118 BHP at the rear wheel, using single injectors. The power curve of the engine naturally falls off after about 9500 rpm, so there's always enough time to deliver the right fuel.
So, you can still achieve the right fuel delivery without
fitting twin injectors. How?
You can increase the fuel pressure, or you can fit bigger
injectors.
The first option is very difficult, but the second is easy. 916 Strada and Biposto models use 3.0 bar fuel pressure, while 916SP and Corsa models use 4.5 bar. This produces 22% more fuel from the same injector duration !
The other thing to remember is that Corsas produce around 135 BHP rear wheel, while a Biposto produces around 104 BHP. Corsas do this from valves, cams, header pipes, and REVS. If you want your crankcases to survive, you shouldn't rev over 11000 RPM, unless you want a replacement schedule like a Corsa, where the crankcases are replaced every 1200km.
Firstly, read the question above !
The 748 Strada / 748 Biposto / 916 Biposto use the Weber 16M ECU, which is only designed to run one injector per cylinder. We have tested the ECU with two injectors driven in parallel from the wiring harness connector at the throttle bodies, and there appears to be no reason why the ECU won't work this way. Naturally the injector durations in the fuel map will need to be changed to accomodate the increased flow.
However, as detailed above we see no reason to do this unless your engine produces over 120 HP at 10,000 RPM.
Back in the distant past (851 era) the Weber atmospheric pressure sensors were atrocious. The original 851 had a complete altitude compensation correction table which worked nicely up to 8000 feet or more.
Because this sensor correction is designed to lean off the mixture at high altitude (to compensate for lower air density), the tables had the range of +4% to -32%. This caused problems with faulty sensors, which could lean off the mixture by 32% at any time the sensor mal-functioned.
The factory solution was to reduce the correction range of the sensor to +4% to - 8%. This situation continues with the current models, but we can fix it.
Take a look at the correction table:
| Air Pressure (millibar) | 622 | 683 | 744 | 805 | 867 | 927 | 988 | 1049 |
|---|---|---|---|---|---|---|---|---|
| Approx. Altitude (ft.) | 13200 | 10800 | 8500 | 6200 | 4600 | 2600 | 600 | -1000 |
| Original Correction | -32% | -28% | -20% | -14% | -9% | -6% | -2% | +4% |
| Current correction | -8% | -8% | -8% | -6% | -5% | -3% | -2% | +4% |
All of our UltiMap Engine Management Chips can be supplied with the altitude correction recalibrated. Simply add a 'P' to the order code (for example UM081P). These need to be ordered specially, as they will make your bike run poorly if the altitude sensor develops a fault.
Note that the following UltiMaps come standard with
altitude compensation, so they don't need a special order:
Due to the massive interest in the Suzuki TL1000s (and it's apparent jetting problems) we have developed the UltiMap Engine Manager. This cigarette-pack sized computer intercepts the injector wiring and allows complete re-mapping of both cylinders via a PC-interface.
We will be testing this with the stock exhaust, as well as a range of aftermarket exhausts, and offering the basic unit pre-programmed to suit. The PC software and cables will be offered at extra cost to those who wish to modify the maps further, or to use in racing applications.
The Manager is now available for Suzuki TL1000s and Harley Davidson Road King, and the Triumph T595 version will be available mid-July 98.
Pricing: 2 cylinder versions AUD 595.00, 3 or 4 cylinder versions AUD 695.00
Because we change a lot of settings it's possible that your bike will feel different at low rpm/ low throttle. Naturally the idea is that the bike feels better everywhere, but our methods are designed to ensure that the best is possible with a bike which has been set to factory spec.
Our chips are often leaner in the low rpm area, which is why they respond better to throttle, but conversely it puts them a lot closer to the threshold of mis-aligned throttle sensors. That's why we recommend you have your delaer confirm the following:
Although these are simple procedures, you'd be surprised how often they are not followed, and how often an out-of-the-box bike can be wrong! Specifically, certain Ducati 8 valve models can have cam timing variations by as much as 8 degrees crankshaft, from the factory!
We specify these points because they are exactly the procedure we follow before we dyno test and road-optimise our UltiMap eproms.
If you follow the same procedures, you should have a bike which runs ideally, the same as our test bikes!
We map all our eproms for standard OEM air filters. The large paper cartridge type fitted to Ducatis works extremely well, and our tests with other types have revealed greater airflow restrictions than the stock filters. Therefore we do not recommend or reject any aftermarket air filters.
For some reason we have enquiries about our EPROMs for K&N filters : We have never produced EPROMs for K&N filters ! If you have an eprom with our name on it (either FIM or UltiMap) which purports to fit K&N filters, please contact us with the name of the dealer you bought it from. We do not wish to see our name on product which we did not manufacture !
The only way to check is with the throttles completely shut (with the idle stop screws backed right out) and you want 150mV +/- 2mV. That is 0.148 volts to 0.152 volts. The reading is taken from ground to the middle pin on the throttle sensor connector, or across pins 16 and 30 on the ECU. This is very difficult, the factory spec is +/- 5mv but we think the results are better if this is within 2 mv. As you tighten the lock screws the sensor moves so you must progressively tighten and re-adjust until it's right. When it is within 2 mV (you snap the throttle open and shut a few times and re-check) you can reset your idle stop screws to get 1200 rpm idle. For more info see Question 11 below.
Firstly, some background on the Weber 1.6M ECU as used on 1100 Sport and 916 Biposto.
The controller is the Motorola 68HC11, a chip developed ten years ago for injection applications. Delco ECUs also use this chip. Although it's only 8 bit it has 16 bit math, and is found in many other applications as well as injection.
The timing is derived from one sensor at cam speed. On Ducatis this is the cam drive jackshaft, on Guzzis it's in the cam drive in the timing chest. The sensor collects 48 pulses plus 2 gaps (known as missing tooth triggering) totalling 50 intervals, for a resolution of 14.4 degrees crankshaft per pulse. The ECU derives both engine speed and phase from this sensor. By phase I mean the point in the firing cycle of each cylinder.
Previous Ducati and Guzzi models used a processor which took 2 triggers, one directly from the crank at 90 degree intervals, and one phase trigger which took one pulse from the cam drive, ie once per two revs, to identify engine phase.
Herein lies the first, and most common, problem with all of the late model bikes. The ignition timing is derived from a half-speed sensor, which is prone to mechanical backlash... this means that under certain engine conditions, the gear which triggers the sensor is wobbling slightly between drive and trail on it's driving gear. In other words, the advance is calculated from an interval which can vary depending on mechanical slop in the cam drive.
Two factors affect this. First, the period immediately before the relevant ignition point is used to calculate the degrees of advance as a fraction of the overall period of 14.4 degrees. So variance on the interval produces variance on the fraction. Secondly the computer also calculates RPM from the same interval. The ECU has a sophisticated acceleration / deceleration algorithm which anticipates what is happening next, based on the history of recent pulse intervals. If the pulse intervals are getting shorter, the ECU assumes acceleration and modifies the ignition timing to accomodate a predicted shorter interval in the next pulse. If the pulse intervals are lengthening then the ECU assumes deceleration, and also trims the advance.
Now, if the interval is changing from shorter to longer, PULSE BY PULSE, the ECU is buggered because it cannot tell if the engine is in acceleration or deceleration. So we have a misfire situation. This is precisely the kind of operation you mention where your engine stumbles on cruise at 3400 or 3800 rpm. As you said, the engine pulls fine on drive, but if the engine is slopping around on constant throttle, the ECU can have difficulty working it all out, and you get a stumble. In my opinion this stumble is a "wild card" ignition pulse, maybe 10 or more degrees out, as the ECU tries to figure out an engine mode. You would also observe that it only has one bad ignition pulse usually, which often completely stops the engine. We have been observing this phenomenon since 1995 when the 1.6 was introduced on Ducati 748SP models.
The funny thing is, the rpm point at which this happens is different from Guzzi to Ducati, even from 1100 Sport to Daytona RS. But there's the rub, because each engine has different bore/stroke, different resonances, and each individual engine is microscopically different to the last. That's why some bikes seem to runs flawlessly, and others of the same type stall at every traffic light.
Further, the previous ECU did not exhibit this fault to any great degree. Remember that this ECU used an RPM (and ignition) trigger which was on the crankshaft, with no possible backlash. The only time this fault shows on the older ECU is when the main bearings are failing, and the crankshaft is wobbling on the bearings. This also produces a sequence of short and long pulse, which confused the ECU in a similar fashion. This I have seen dozens of times, with disbelieving customers who refused to listen to me when I said their misfire was caused by failing main bearings! It proved true in almost every case. (or crankcase, because a broken crankcase does the same thing by allowing the crankshaft to wobble in the cases).
The solution.. there is no solution yet. Again I am treated with disbelief when I suggest that to get rid of a misfire you split your 916 engine and re-shim the jack-shaft end float, and check the play on the jackshaft bearings. "But it's the computer" they cry.
A final comment on this misfire problem. Both Ducati and Guzzi produced a model which switched from the P8 ECU to the 1.6M ECU in mid-production. The 1994 916 Strada (solo seat) used a P8 ECU, and the Biposto (95 - now) uses a 1.6M. The engine spec did not change at all when they swapped to the new ECU, but suddenly the bikes had a misfire. Some people even traded their Stradas on a Biposto, only to find they had exactly the same power, but with an added misfire. The same applies to the Guzzi Daytona Racing (P8, C cams) and the Daytona RS (1.6M, C Cams).
We are still trying to find a fix for this in software, but I confess I don't think it is really possible. The main reason it is more prevalent on Guzzis is simply the variance in manufacture compared to Ducati.
We specifically do not recommend anything in that price range, as everything we have tested is crap. For a Lambda sensor to read properly it must have temperature compensation, which is essentially an ECU attached which reads voltage and internal resistance and then looks these up in a table to derive lambda for any given voltage and temperature. The CorseTec and Motec that we sell do this. Nothing on the market for $500 does this, they are usually just a bar-graph LED which shows sensor voltage in a tight range. Useless. Absolutely useless.
The other factor in Lambda meters is the probe itself. many of the under $500 meters use a common auto probe which is cheap, but only designed to read accurately at a lambda of 1.0. Although this is a useful area, peak power is delivered at a lambda of 0.88 and a linear reading from 0.75 to 1.0 is essential to properly tune an engine. All the cheap probes/meters do is stretch the linearity of the sensor around the 1.0 region to try to derive richer lambdas than the sensor is capabnle of. Honestly, we have tried 5 different meters in an attempt to offer a chepaer alternative, and they are just no good. As the exhaust temperature changes the LED readout changes, whereas a temp-compensated unit will show lambda only. It's easy to check because CO meters, although slow, are very accurate over a wide temperature range. We did A/B comparisons of our lambda meters with a CO meter and the cheaper alternatives and the results showed that the CO meter tracked closely with the temp.compensated units, but the cheaper units slewed wildly around, to the extent that I have never used them since!
We use a Bosch Motorsport probe which is used world-wide by Superbike, Grand Prix, and Formula 1 teams, and costs around USD 290. The probe is wide-range, linear, and withstands leaded fuel, so it is obviously not an common auto type. The part number is 0 258 104 002, or commonly called LSM11.
So really you'd be better off with a cheap CO meter which although slower, is far more accurate. The cheapest I have seen is about USD 900, still more than you want to spend, but don't forget that every 2 bit auto shop has a CO meter and they are rarely used. We used to borrow them all the time before we got decent Lambda meters.
Unless we have specifically mapped an engine with your configuration, we don't recommend an UltiMap eprom. This means that if you have built a big bore engine, or modified cams or valves, we probably don't have a chip for you. The only way we can make a specific chip is if you are prepared to do some testing and give us exhaust gas figures for multiple operating points from your engine. This requires a gas analyser and a brake dyno. If you want more information, Click Here.
Every model of Weber injected bike has a CO trimming function which allows the idle mixture to be set. In fact the trimmer affects fuel delivery over the entire RPM range, but with a lesser effect at higher RPM. The amount of fuel added or subtracted from the base fuel duration varies from model to model, as it's programmed differently for different models and ECUs. However it is necessary to adjust the CO Trim to obtain optimum performance.
On these ECUs there is an external screw adjuster located next to the 35 pin harness connector. This is usually under a grey plastic cap which can be removed for access. The screw adjuster has a range of four turns, or plus/minus two turns. The default position is in the middle of the range. When you screw the adjuster clockwise the mixture is richened. The adjuster has no end stop, so if you over-adjust the screw the trimmer just rolls over at the maximum or minimum setting, without damaging the trimmer. Each time the trimmer rolls over a tiny click is just audible.
So to set the default position, all you need to do is turn the screw clockwise five times, and listen for the tiny click when the trimmer rolls over. Note the position of the screwdriver blade, and then turn counterclockwise for two turns. The trimmer is now in the default position.
Since the trimmer is simply a potentiometer which puts out a signal from 0 to 5 volts, you can also set your default position using a voltmeter placed on the centre terminal of the trim pot, inside the ECU. You should set the default position to 2.5 volts.
On these ECUs the trimmer is located inside the ECU and the rubber bung must be removed for access.NOTE - Always re-seal the rubber bung with waterproof tape (ie Gaffer tape or Duct tape) after you have finished adjusting CO.
Next to the chip socket there's a very small (1/4" square) trimmer potentiometer. This has the same function as the external trimmer screw on P7 and P8 ECUs. The Trimmer on the 16M ECU has a range of about 3/4 turn, or 270 degrees. When you hit the end stop, STOP !!! There is no roll-over on these trimmers and they will break if you try to force them.
When you screw the adjuster clockwise the mixture is leaned. To set the default position, simply set the trimmer in it's mid-rotation point. You can also use a voltmeter to set the 2.5 volt point.
On these ECUs the CO trim function is achieved via software. There is no CO trim potentiometer. To get access you need either the factory Mathesis tester, or the UltiMap Diagnostic software for Win95.
The CO is adjusted with the software using an Up/Down system, and when the correct CO is obtained the value is locked into the ECU using EEPROM memory.
This depends on the particular EPROM settings for each model. Bear in mind that this function is deigned for idle mixture adjustment, not overall engine tuning! Typical examples are shown in the table:
| RPM | Idle Throttle | Idle Throttle range mS | Idle Throttle range % | Mid Throttle | Mid Throttle range mS | Mid Throttle range % | Full Throttle | Full Throttle range mS | Full Throttle range % |
|---|---|---|---|---|---|---|---|---|---|
| 1100 | 1.17 mS | +/-0.24 mS | +/-20% | 2.31 mS | +/-0.24 mS | +/-10% | 3.44 mS | +/-0.24 mS | +/-7% |
| 4500 | 0.96 mS | +/-0.15 mS | +/-15% | 1.48 mS | +/-0.14 mS | +/-10% | 2.78 mS | +/-0.14 mS | +/-5% |
| 9100 | 0.95 mS | +/-0.07 mS | +/-8% | 1.11 mS | +/-0.07 mS | +/-6% | 2.20 mS | +/-0.07 mS | +/-3% |
Note that a mixture change of 1.5% is required to move the exhaust Lambda by one point (ie from 0.90 to 0.91) so the available range is pretty massive, and will still have some effect at high rpm.
Firstly let's look at the factors involved in the mixture system:
The fuel entering the engine is controlled by the injectors, principally by how long they are open for each engine cycle. Typically at idle they are open from about 1mS to about 2mS. The CO trimmer affects this duration as shown in the table above. This change is the same for both cylinders, and cannot affect the CO cylinder balance.
The computer measures the butterfly position using the Throttle Position Sensor (TPS). This sensor is precisely aligned on the butterfly shaft and afftects not only fuel delivery but ignition advance as well. Many owners are tempted to move this sensor on the shaft, as you can get more fuel delivery from the ECU in this way. But there are several goods reasons not to do this:
The air entering the engine is controlled by two things, the throttle butterfly and the air-bleed channel. These two factors are inter-dependant, ie you can get the same amount of air with a shut throttle and open airbleed as with an open throttle and shut air-bleed. The difference is that the ECU does not know how the air-bleeds are set, whereas it does know the throttle position. So you can change the air entering the engine either by opening the throttles (which the ECU knows about and makes an adjustment for) or by opening the airbleed. The salient point here is that the butterfly and the airbleed are designed for two different functions.
The butterflies are designed to deliver the same amount of air to each cylinder under load conditions. This is achieved by synchronising the butterflies using a vacuum guage or 2-channel CO meter.
Because the butterflies are not perfect, the airflow will vary between the two, especially at low throttle settings. It is impossible to maintain exact synchronisation through the throttle range, so the butterflies are synched where they are most critical, ie in the range one-third to one-half throttle. This can be easily achieved on a brake dyno.
The designed purpose of the air-bleeds is to achieve cylinder balance at low, or idle, throttle settings, where the butterflies are effectively closed on the stop screw. The bleeds are adjusted to give either matching vacuum or CO for both cylinders.
Clearly the idle can be set in a number of ways, since the mixture and balance are interdependant, along with the butterfly synchronisation.
So unless you are familiar with idle setting then we suggest you leave this to a dealer with the right equipment. To properly set the CO you need a CO meter !! If you don't have one it is very hard to pin down the relationship between the CO trim, the air bleeds, and the butterfly position.
So to re-iterate the variables:
We use the following sequence to correctly align all parts of the induction system. This sequence is essentially the same as the factory recommended sequence:
So hopefully you will have an engine which now idles, accelerates, and delivers full power faultlessly. Again, if you are not confident about all of these steps, then we suggest you use a dealer who has the skills and equipment. It is not worth adjusting the CO trimmer unless the entire sequence is followed without skipping any steps.
The ECU on these bikes (made by TDD in Bologna) is highly sensitive to interference from the spark system. We have tested a number of Bimotas with this computer (including the YB9, the DB2, and the V-due) and they all showed a periodic miss which was related to interference.
The simplest way to reduce this (it's almost impossible to eliminate) is to shield the cable which runs from the RPM pickup in the alternator cover, to the ECU. On some wiring harnesses a part of this cable is shielded, and another part is not. We have used aluminium sheathing, but even better is braided sheilding tube (looks like braided brake lines!). This is often used on high energy ignition systems.
Further, you should re-position the spark plug leads to be as far away as possible to the injection harness. If it needs to cross the harness, do it at a right angle as this reduces interference. We did this with the V-due and improved the problem a lot.
You can also try spraying the inside of the plastic ECU box with an interference paint (lead or something) which will help shield the ECU from the same problem. Again we tried this on a V-due and it made a small difference.
We also fitted different ignition coils which made a lower voltage on the spark leads (that is, a less efficient coil). This helped too.
Finally, if the map is really lean you will see the symptoms you described, but on Bimotas they are often masked by the interference problem. We recommend that you reduce the interference as much as possible before you start to change the fuel settings.
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