MicroSquirt.com read only forum (Jan.15,2018)

plans...
fit throttle bodies to my mx5

problem
air flow meter

solution
removed said air flow meter

that said, i am buying a v3 of the megasquirt in mid jan, until then, i need to get the throttle bodies up and running on the car. so i have come up with one solution.

the throttle bodies are off a honda fireblade 40mm, i will be using the fireblade injectors if they are the correct resistance, if they aint ill use the std injectors.
the afmo n my car contols the fuel pump shut off, intake temp sensor, and it gives a 5v-0v signal respective to load, at wot its down to 1.5v shut throttle its at 5v.

i already have a tps on the throttle bodies, but the signal that gives will be linear as opposed to the dynamic signal respective to airflow the afm will give.
i also have a map sensor on the throttle bodies, but the map sensor will give a dynamic signal from 0-5v respective to airflow so at wot it will be giving 5v instead of 1.5v, is there any way i can invert or reverse this signal to get the correct voltage for the map? or would it be ok on the linear signal from the tps?
any ideas anyone??

It will probably be easier to get the Megasquirt and throttle bodies fitted in one go instead of attempting a half-cocked solution. It will probably be very difficult to get things setup with the old ECU in control but with a different load sensor input. If it works at all it may well be undriveable.

James

i cant afford the ms at the mo, and i need the noise and extra power.
i have the scematic now to invert the signal from the map sensor to the same signal as the std afm would give. so the ecu will function as std but will adjust the timing and fuel for the extra air from the itb's, i will also be using the tps off the honda itb's and i will wire it into the std wiring for the std tps. so all said and done the setup should drive as std but with more power.

can anyone see a problem with this??

Errmm...

The signal voltages may be the same, but the respons and characterisitcs of the signal will be quite different.

It may be ok at idle and WOT but anywhere else could be a nightmare.

If it was that simple to do then thousands of home modders would have junked the AFM.

You could end up washing bores, or running lean, getting Massive detonation or just having something that is a pig to drive.

Your not going to realise a huge ( if any ) power increase without tuning the fuleing anyway.

TT

stevenford_uk wrote:can anyone see a problem with this??

Yes, The Map sensor does not have a MegaSquirt attached to it!!

Other than that, how does the manifold pressure relate to airflow? really only partially, you need a temperature sensor too. (your VAM probably has one built in.) Also the airflow transfer function is not going to be linear, like the output of the Map sensor, so you would get lean and rich conditions as mentioned above.