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XMS4 | Frequently Asked Questions


Frequently Asked Questions.


How do I know if the coils that I am using for the XMS4 are positive or negative firing?

A simple test can be done if you know the wiring pin out of the coils that you are using. The coil trigger wire is flashed across the battery positive terminal and then across the battery negative terminal, to see when there is a spark generated from the coil.

Can I wire the XMS4 to do sequential fueling but still use the distributor?

Yes, you can. The ignition outputs must just be joined together and then connected to the Blue-Fire Amplifier.

I have a problem. I have a XMS4A stand alone installed in my Fiat Uno Turbo, but I lost the software for tuning and cannot find it. I would like to know if you could send me a file with the software for tuning my stand alone Perfect Power XMS4A.

Both LetRipp versions are on our website for download.

I have an Opel Corsa C 1.8 8V. My Rev Counter, temp gauge, speedo and electric power steering (eps) is not working. They use to work from a cluster on the original ecu, now they don't work at all once Perfect Power stand alone was fitted. Can't the Perfect Power run this cluster?

The only way to get them working again is to have the original ECU working in parallel with the XMS4 unit, so the XMS4 will be working the injection and the timing, the OEM unit will be doing everything else.

The RPM keeps jumping to 9999 when the engine is revved.

The incoming crank signal is experiencing noise and is receiving what it is interpreting as a second missing tooth. Check the earth connections, replace the crank sensor wiring with screened cable where the sensor is only earthed on one side.

The TPS % displayed by the software is not stable?

The TPS sensor earth should not be earthed to the engine block, but to the chassis or battery.

There is spark, but the injectors are not clicking?

Verify that there is 12 volts at the injectors. If there is 12 volts briefly short the other wire and hear if the injector actually clicks. Check in the LetRipp software that it has calculated the injector ms. Verify that the "Cam Every Two" in the "Shift F2" map has not been ticked.

The Rev counter does not work when pin 5 of 22 is connected?

The rev counter output from the XMS4 requires a 5 volt pull up voltage (pin 10 or 21 of 22). Some rev counters require a higher voltage signal in which case you could try to teethe cars rev counter wire to one of the Blue-Fire outputs. If that does not work then a step up transformer needs to be fitted.

The rev counter and the LetRipp software RPM is not the same?

The original rev counter may be for an engine that had more or less cylinders than the engine that is currently fitted.

When the ignition key is switched off the engine does not stall?

It is possible that one of the supply relays is causing this type of problem; there is one relay that once it is switched on it is causing a closed circuit, which is causing a power feed back that is keeping the XMS4 working.

The engine stalls when I unplug the USB cable?

The switch power supply for the XMS4 unit does not stay constant; it may fall away after the engine has started.

How should the Power supply be wired for the LSU4 probe?

The supply power for the probe should ideally be supplied when the engine is idling. To do this use one of the RPM set points to switch a relay on after 200 RPM.

The injectors that I have are low impedance 12 ohms and less?

The XMS4 unit cannot drive low impedance injectors; additional injector drivers should be fitted to each injector.

What would I have to fit for the XMS4 to control these injectors?

You have to fit one of the Perfect Power 7 AMP Silver ignition amplifiers for each injector.

Does a value of 100 in the injection map mean 1.0 ms injection open time?

It can, provided that the present AMP reading is set to 1.0 and the fuel range in the "Shift F1" Parameters map is set to 1.0.

The injection ms keep changing drastically all the time even at idle?

Open the "Data Display" and open the "SN" display window for "Accl Enrich". This value should be at zero if the Acc pedal is not being pressed; if it is displaying a number then go to the "Shift F1" Parameters map and reset the "Acc Detec" to 50 or higher or set all of the side table in the "F5" Acceleration maps to zero.

The engine will only rev up to 3500 RPM. Sounds like a rev limiter?

It may very well be that! Check in the "F6" set points map that "RPM#1", "RPM#2" and "RPM#3" have not had the hard or soft cut enabled.

The spark output stops when the engine revs over 4500.

The Ignition reverence angle in the "Shift F1" is less than ignition point "F2", which is trying to force the unit to calculate timing in the missing tooth area. The sensor must be moved to a greater angle.

When I use 24+1 the engine keeps back firing?

When the 24+1 trigger is selected the unit will automatically select the sequential mode. If you are using a wasted spark coil pack, verify that you have batched the correct XMS4 ignition outputs to the firing order.

How do I know that the timing degrees in the map are lining up with what the engine is experiencing?

When the engine is idling, set the green cursor point to 0. The engine may battle to idle. Use an old fashioned timing light and verify that the mark is lining up with the 0 degree mark on the crank pulley. If there is no mark then you will have to make one yourself.

The car battles to start in the morning.

The Prime Map "F3" may need to be increased s well as the cold compensation in the "F1" Injection Map.

What do the entries in the dwell map mean?

The entries are coil charge time in ms.

What is the typical dwell time that is used?

The average dwell time that is used is a 2 at the lowest RPM and then blend "G" to a 4 at the highest RPM. This should allow the engine to start so that it can be tuned.

As soon as the engine heats up, the boost pressure drops, even in closed loop.

Open all the Boost side tables and verify that there are no negative numbers in the air temperature compensation. If there are then make the column all zeros and test to see if the boost pressure holds.

I am trying to pulse the boost solenoid at 50% but the actual boost PWM is 63% in the data display?

Either you have a boost gain higher than 0.0 in the parameters map or you have values in the boost air temperature map.

I have wired one of the AUX wires to control the boost but there is no response from the solenoid.

Make sure that the AUX you have used has been assigned in the "F6" set points map under the boost heading.

Is it possible to run the Boost circuit in open loop?

Yes it is, in the "Shift F1" parameters map make the boost gain zero.

The car has a flat spot as you pull off?

The acceleration maps "F5" may need a little work as well as the detection speed "Shift F1".

I have increased the values in the Acceleration maps but there is very little response.

The entered value in the "Shift F1" parameters map for the detection speed may need to be reduced.

How do I know if one of the setpoints is active?

As soon as the set point goes active a "x" will appear next to it. Also if you are editing that set point the background colour of the screen will change to green.

Will the XMS4B unit still function if the wide band lambda is not connected?

Yes it can; the software must be set up to not allow the unit to modify the main injection map. To do this set the adjustment windows above each column in the lambda target map to zero.

The lambda circuit keeps leaning out when the car is cold?

The Lambda Map has an engine temperature side table that has not been setup. So what is happening is the lambda control is removing all the cold compensation from the Injection Map.

The lambda circuit does not adjust the fueling to attain the set target.

There could be two reasons for this. The adjustment windows above each column of the "F7" Lambda Map has not been set, or the actual Lambda reading is outside of the "AFR rich limit" of the "AFR Lean limit" in the "Shift F10" parameters map.

The wide band lambda reading is changing very quickly.

Check the connecting plug between the harness and the wide band probe for water. The lambda probe could be faulty.

How should the power supply be wired for the LSU4 probe?

The supply power for the probe should ideally be supplied when the engine is idling. To do this use one of the RPM set points to switch a relay on after 200 RPM.

What does ETC mean?

ETC stands for Electronic Throttle Control. It is more often referred to as "drive by wire".

Can the XMS4 control VVT solenoid similar to VANOS?

No, the unit can only switch a solenoid type of V-tec systems, where it is either on or off. The VANOS type of system can be controlled by one of Perfect Power's other units for example the I-Switch.

Can the XMS4 do staged injection?

No, not with one unit only. You can wire in a second XMS4 unit to control the extra injector set by switching the power on, using a set-point output from the first unit.

Can the XMS4 do Nox control?

No, not with one unit only. You can wire in a second XMS4 unit to control the Extra injector set by switching the power on, using a set-point from the first unit.

Does the XMS4 have two tuning maps?

Yes, Map A and Map B.

Can the XMS4 use the standard Hall Effect sensor on the engine?

Yes, the XMS4 can supply the Hall sensor with the 5 volt supply and will need to have the 5 volt pull up voltage teed onto the Hall sensor signal wire.

Can I convert from distributor to a wasted spark coil pack?

Yes, provided that you are not using the 1 pulse per fire trigger pattern.

Can the XMS4 unit use the factory air flow meter (MAF)?

No, the signal voltage supplied by the MAF sensor works differently to the way the AMP sensor that is fitted; the XMS4 is not programmed to work like that.

Can I fit the Electronic Throttle Control unit to an engine where there is an Accelerator Cable?

Yes you can, the XMS4C unit has this feature. However some kind of TPS sensor has to be fabricated to fit onto the Acc pedal.

Can I use the XMS4 on a three cylinder engine?

Yes the unit can. The unit will need a crank and cam signal (TDC) in order to perform this function.