Initial Map Calculator

[whizzo944]

Dear All,
I am fitting a Megasquirt 2 with Extra code to my bike, a Honda NC30. When I try to calculate an initial map the calculator objects to the figures I enter, i.e. max horsepower is at 12,500 rpm and max torque is at 10,000 rpm. Can anyone help or explain to me how the initial map is calculated?

Dave.

[Matt Cramer]

The reason it objects is that this is well outside of the parameters the method was designed to work on. I'm not aware of the details of how it works, but I believe it was designed for low output automotive engines with a small cam and won't give very good results on a bike engine.

[tronds]

It doesn't work for my application either.
I am trying to generate an initial AFR table for a tuned VW G60 engine.
1789 cc, 210 hp at 6200, about 200 Lb-ft at 4200 rpm(educated guess), redline at 6500. boost at 4200 is 180kPa boost at 6000 is 200kPa.



Am I off the scale, or do I assume something wrong in my initial data?

[racingmini_mtl]

The tool only generates VE tables. If you try to use it for other tables (AFR or ignition) it will give an output but it will be garbage as you saw.

Jean

[whizzo944]

Dear All,
Since the VE Table calculator must have some maths involved, can anyone explain how the original
calculator works so maybe I can figure how to modify it for my engine. If I'm clever enough !!!!!

Thanks,

Dave.

[PSIG]

From the MegaTune manual:

Generate Table This is a tool for establishing a baseline VE table for your tuning efforts with MegaSquirt® EFI Controller, MegaSquirt-II and UltraMegaSquirt. The VE curve is assumed to follow the torque curve (which is not quite right, but close enough for a first approximation). This calculator is based on modeling your engine's wide-open-throttle VE with a quadratic equation of the form:

VE = A*RPM² + B*RPM + C

where A, B, & C are constants.

These constants are derived from the:

* Peak torque@RPM,
* Peak horsepower@RPM,
* The assumption that the peak torque occurs at the VE curve's maximum (i.e., the first derivative with respect to RPM is zero).

An assumption has been made about the VE required to produced 1 lb·ft/ci as well as 1 hp/ci. A further assumption has been made that compressor efficiency=60% for kPa > 100. Finally, a scaling factor has been used to adjust the wide-open throttle VE for lower MAP values. The factor is derived from examples of working VE tables. A limit of 5% per RPM bin drop in VE has been applied to prevent the extreme drop-offs that can occur at high RPM & kPa when VE is modeled in this way. As well, all VEs are restricted to be not less than 25% of the highest VE, to prevent unusable idle values. This calculator has not been tested on all possible engine combinations and operating parameters. Use it at your own risk.

If you're a code junkie, perhaps you can just change the calcs in the Table Generator section, and get extended capabilities to suit. I did one years ago, and not being a code junkie to just change the generator, I just entered the info by scaling the inputs and reassigning the RPM bins. I don't recall exactly which I did (RPM, CID, etc.), but I'm sure you could figure that one pretty easy. Another method I have not tried is to use a dyno graph and make two tables - one from idle to half max RPM and a second from there to max. Then just take every-other column from each and create your table. It should work well enough to get it going for tuning.

David