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Setting boost

James Wingfield

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I’ve got a LEM G3 and I’m trying to set the boost pressure to a sensible limit in each gear. The difficulty I’m having is due to the varying engine load. If the engine is more loaded then I need to set a higher duty cycle to maintain the correct MAP level. For instance, in high gears and/or going up hill the duty cycle may need to be several % lower than the same condition in a lower gear and/or going downhill. I have set different duty cycles for each gear but how have others dealt with the varying engine load due to gradients etc. At the moment I find that I often hit the boost limiter at 1.7bar when going uphill but may only reach 1.3bar if going downhill. I think I need another input, or some way to run closed loop but I don’t think that’s possible with my ECU. Can anyone offer any help? Thanks, James

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  • 1 month later...

Hi James.

As you are most probably aware the G3 can only do boost solenoid DC by Gear, TPS or Boost Adjust (0-5v) vs. RPM.  Unfortunately, this is the full extent of your problem really.  The only solution currently is not to boost by gear.

Closed loop boost will rectify this situation, but this is still a little way off.  If you are really needing to boost by gear, upgrading to G4 firmware is potentially the best solution for you.  The reason being is you can span almost anything against anything on the G4 platform if it makes sense to.

By having your boost control table as gear vs. MAP, things start to look a little more achievable with what your trying to do.  The only thing is you cannot give it a DC against the RPM if it's done this way.



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