Not Running Through to Full RPM

Hi - hoping someone can help?

I have a TL1000R drag bike fitted with a DTA T4+ ECU. Have been setting up and running beautifully on idle up to 5,000 - 5,500 RPM at which point it is almost as though it hits a false limiter? Have been through all the settings on the ECU and cannot see anything amiss. Whether I run it on the bench or underload, normally aspirated or on boost I get the same issue.

I don't think it is fuelling as it does not run excessively lean or rich when it happens and no changes to the fuel map seem to make a difference. I have retarded the timing but the same issue occurs.

I have tested the injectors (via the ECU) and appear to be working fine and also tested the coils through to 10,000 RPM and sparking fine. The Oscilloscope for the crank sensor on the trigger wheel appears fine also. Any ideas?

Using your oscilloscope on your crank sensor, how narrow does the pulse width (either high or low) become at 5000 RPM?

Ignition coil charge time perhaps.

Thanks both for your replies. The oscilloscope I have is in the ECU itself so only tests initial cranking. That itself looks fine and did run past DTA and they also confirmed it looked okay. If I get no joy might have to invest in a external oscilloscope to test at higher RPM.

Re coils I am thinking they might be suspect - everything suggests it is electrical? I have ordered some Hayabusa stick coils to see if they are any different. The current coils I have are 3ohm Dyna coils which I appreciate are probably a little old school now!

If charge time is set to low, this can/will cause your issue. At least, this is my own experience on a single coil setup.

If you can borrow a scope it would be worth seeing what happens.

Perhaps crank sensor voltage at high RPM is causing missed or false teeth with the current trigger arming settings. I don't know what ECU you're running so that may or may not be a factor.

Alternatively the scope trace may show you the signal is getting too noisy for accurate triggering at high RPM.

Thanks both. I spoke to DTA the ECU supplier and they advised the dwell times were too high for Dyna coils (or too low - depends if you are glass half full or half empty I suppose!) and to drop to 1,500. There is not a lot of technical data out there for these particular coils so seems to be a bit of trial and error. Tried this but then found a bug in the software which they have provided a patch for this afternoon so will try again later this evening/weekend. If that does not work might need to go down the scope borrowing/purchasing route.

When they run the map on their test bench they had no issue going through the entire RPM so I assume it has to be an electrical disagreement somewhere!

You can measure the necessary dwell time with a coil by using a current probe with the oscilloscope. Here is a some very useful info and a description of the procedure to measure it:

http://dtec.net.au/Ignition%20Coil%20Dwell%20Calibration.htm

And here are some HPA threads with more links on the same topic:

https://www.hpacademy.com/forum/general-tuning-discussion/show/finding-acurate-dwell-time/

https://www.hpacademy.com/forum/general-tuning-discussion/show/how-to-use-an-oscilloscope-to-detemine-the-optimum-dwell-time/

Jo

You could simply lower dwell / charge time in order to "feel" out whether or not the lower spark energy will cause the engine trouble to occur at a lower engine load level.

Not exactly a deeply scientific approach, but it would not hurt to try it and it will not do harm either.

Thanks for the help. Okay so new Haybusa coils, amended dwell and advanced ignition. I am now successfully getting full RPM naturally aspirated! Think this confirms crank readings are fine at high RPM.

However the minute I plumb the turbo back in it presents the same issue and stuck at 5,500 RPM again. Currently running 8psi boost. I have tried retarding the timing slightly on boost but same issue. Do I just need to be braver with my ignition retard/advance? It is a v-twin engine if that makes a difference. Fuel map is on the rich side at the moment (about 77 lambda under what boost I do manage to get to). I was thinking to lower the boost further to see if I can rectify it and work up from there if I can resolve it?

I'd try 0.83 Lambda, unless you have a specific reason to be at overly rich 0.77 for 8 psi.

Have you tried to close the plug gap, ie. 0.3-0.4 mm for a test?

Are the coils and ECU receiving proper Alternator / Battery voltage?

What is the voltage at the coils when the problem occurs?