Is there a way to output "load" from 0-5v?

JustinL · Post by **JustinL** » Tue Apr 25, 2006 6:50 am

My Bosch Motronic control unit needs a "load" variable for the part throttle ignition timing maps. This load is based on 0-5v from the AFM (which I'm removing). Is it possible to simulate the load signal from the MS? Alternatively could I use the 0-5v TPS as my load variable?

Any thoughts would be greatly apreciated.

Justin

eliotmansfield · Post by **eliotmansfield** » Tue Apr 25, 2006 7:08 am

Well the map sensor is the 'load' device on MS - and that outputs a 0-5v signal. But the chances of it being directly useable as your input are remote.

Post by **grippo** » Tue Apr 25, 2006 7:13 am

The MS hardware doesn't ouput any analog voltages, but your idea of using tps for load sounds like it should work - its a direct alpha-N with no software required. How well it will work is another issue because a MAF curve may not match the exact shape of a tps curve, but it may be worth a try.

JustinL · Post by **JustinL** » Tue Apr 25, 2006 9:21 am

First off the car is a 944 turbo. I have a link AFM MAP piggyback right now that pretends to be the AFM. I would love to ditch this thing in favour of Megasquirt, but I could keep it just to simulate load for the ECU. Also minimizing the number of boxes in the footwell would be nice.

If I use TPS as my load variable, will this be too agressive or too tame? Here are my thoughts (keep in mind I'm a newbie to this). If the most agressive maps are in the low load and slowly retard all the way to 55% then switch to WOT maps. With the idle switch closed, the engine will run idle maps.

What I'm worried about is having a genuine high load with low throttle opening thus having a way too agressive timing for the true engine load.

Here is the stock ignition map:

The other solution is obvious... only use full throttle... ever.

It seems like it should be pretty safe, but I'd like to have someone else look at it before I go try it.

Thanks,

Justin

boost junkie · Post by **boost junkie** » Tue Apr 25, 2006 10:25 am

Hrm... its 12x12 too. Why not just run ignition control on the megasquirt and simply copy the numbers over?

JustinL · Post by **JustinL** » Tue Apr 25, 2006 11:43 am

boost junkie wrote:Hrm... its 12x12 too. Why not just run ignition control on the megasquirt and simply copy the numbers over?

That is the ultimate goal, but as of right now my speed sensor wheel has 132 teeth and has a secondary sensor for the reference signal. So right now I'm eagerly anticipating the development of the router board before I try ignition.

I would just like to get MS started so I can get a feel for it.

JustinL · Post by **JustinL** » Tue Apr 25, 2006 12:03 pm

surely the mafs "load" will be power dependent (include rpm), where as the map and tps "load" will be only torque dependent. airflow at lower rpm will be lower even with full throttle than some where higher in the rpm band at the same throttle. not articulating myself well, but hopefully you see what i mean.

fred.

I see what you are saying Fred, and that is exactly my concern. The question is whether this will make my engine explode or just run less than optimally at part throttle. I can always keep my link AFM simulator and let it simulate a load based on MAP and RPM. That may be the best solution until I can get the full ignition running with MS as well.