CBR600 engine tuning?-missing under load at hi rpm

[just]

I am having a problem tuning our CBR600F4i engine on the dyno. The engine is running a Haltech E6X engine management system with four standard Honda coils and two Haltech ignition modules. My problem is at hi rpm (7,8,9000)the engine runs fine under light load, however, as the throttle is opened further and further the engine reachs a point where it starts to miss as though the spark is being blown out. If the throttle is opened further the missing becomes more violent. The missing appears to happen at the same air mass flow rate at different rpm's. The peak voltage (back emf) in the primary coils have been tested as per the Honda inspection and exceed the minimum value of 100v. At 8000v a peak voltage of around 140v has been measured, however when the missing occurs this value jumps to around 400v. This suggest that the spark plug is not firing when the engine misses (possibly blown out?). I have tried and tested many things including spark plug gaps. Changing the gaps just tends to alter the air flow rate at which the missing occurs. As my last resort I am thinking of changing to CDI ignition in an effort to beef up the spark and hopefully beat this problem. Has anyone experienced a similar problem? How do I fix this?
Also, what sought of peak ignition advance values do these motors like? I am getting some extremely high numbers and the motor seems to like it?

[just]

I am having a problem tuning our CBR600F4i engine on the dyno. The engine is running a Haltech E6X engine management system with four standard Honda coils and two Haltech ignition modules. My problem is at hi rpm (7,8,9000)the engine runs fine under light load, however, as the throttle is opened further and further the engine reachs a point where it starts to miss as though the spark is being blown out. If the throttle is opened further the missing becomes more violent. The missing appears to happen at the same air mass flow rate at different rpm's. The peak voltage (back emf) in the primary coils have been tested as per the Honda inspection and exceed the minimum value of 100v. At 8000v a peak voltage of around 140v has been measured, however when the missing occurs this value jumps to around 400v. This suggest that the spark plug is not firing when the engine misses (possibly blown out?). I have tried and tested many things including spark plug gaps. Changing the gaps just tends to alter the air flow rate at which the missing occurs. As my last resort I am thinking of changing to CDI ignition in an effort to beef up the spark and hopefully beat this problem. Has anyone experienced a similar problem? How do I fix this?
Also, what sought of peak ignition advance values do these motors like? I am getting some extremely high numbers and the motor seems to like it?

[Marc Jaxa-Rozen]

What is your coil dwell set at? Have you tried swapping the plugs?

BTW 40-45+ degrees of advance is normal.

Marc Jaxa-Rozen
École Polytechnique de Montréal

[just]

Marc,
Coil charge time is 1.8ms. I've changed plugs a number of times. I've tried irridium plugs and standard plugs.
40-45deg is normal for what? I've got advance up around 70 deg. I put it down to the very short stroke of this engine (42.5mm). If I run 40 deg the headers are cherry red. Maybe I've got my trigger angle wrong. Are you running one of these engines using the standard camshaft trigger? Which two teeth did you remove? Whats your angle? Thanks for your reply.

[B Lewis @ PE Engine Management]

Hi Just,

I don't think changing to CDI is going to help.

Have you tried tweaking the fuel table. Sometimes fuel problems will mascarade as ignition problems and vise-versa. If you have gone down this route, try looking at the crank position sensor as the culprit. What kind of sensor are you running? If it is not the stock unit, I have seen several ocassions where a combination of heat, sensor gap and engine speed will cause the sensor to malfunction.

Also, try to check ignition timing using a timing light to verify what you are getting agrees with the ECU. You can use a short piece of spark plug wire between the stock COP coils and the plug to clip onto. This will at least eliminate one variable.

Good Luck!

[just]

Brian,
I am actually thinking that the cam position sensor is the problem as it gives the computer a home or sync signal. I have had a lot of drama with this sensor previously. The standard Honda item is an int. reluctor sensor and the Haltech appears to have a lot of trouble with this particular sensor being oversensitive, actually triggering off the two mounting bolts that secure the trigger plate to the cam. This caused a lot of problems when I was trying to get the engine running with the Haltech. We have tried to dampen the signal by placing a resistor in parallel with the sensor. This appeared to work however I think the problem with this sensor may have resurfaced. I will replace this sensor with a hall effect trigger and hopefully my problem will be solved.

[Charlie]

Given your extremely high advance numbers, I would take a look at polarity of the crank and/or cam sensors. Reversed polarity means a wandering signal.