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Motec M150 Linearizing throttle response via Throttle Translation

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Hello all,

This is probably a hair brain idea, I am new to tuning. In my normal world (PLCs) which is what I know, you can linearize flow characteristics of say, a water valve, by "inverting" the flow characteristic of the valve, and applying this inverse curve to the output ... so my proposition is this, in M1 tune the Throttle Body Area % characteristic is mapped in 2D table vs servo position. So essentially that would be the approximate flow characteristic of the TB?

*If* this is the case, if you inversed this curve and applied to throttle translation map, I'm thinking this would basically give linear flow characteristic of the throttle body (as butterfly's are non-linear)

I just played around in Excel inversing the curve, so you can see what I mean.

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Your confusion is the way a Throttle Request is treated -- basically it looks up the Y axis value, and set's the servo to the X axis value (always seemed inverted to me). I think you will find that the default curve is already doing what you want to do. But try it for yourself and see.

For circuit cars I generally set up the throttle target on the dyno so that torque is proportional to pedal position - so for example 50% pedal travel will give 50% torque approx etc. Most drivers seem to like it like that.

The curve definitely doesnt always end up looking like the graph above. GM LS throttles for example have some sort of odd linearisation curve already built into the TPS output. For road cars its normally nicer to have the torque increase slower at small throttle openings to prevent the "bunny hop" effect etc.

Thanks for the feedback! David raises a good point, I wonder if the M150 uses the TB area % curve to essentially automatically linearize the throttle demand some what, and then the throttle target can be adjusted from there for the desired throttle responsiveness . Otherwise 75% of the throttle would be in the first 45% of the throttle demand (logarithmic curve)

I like Adams suggestion to calibrate via engine torque , I'm guessing if you checked the engine torque at multiple throttle positions (10, 20, 30, 50, 75, 100) you could interpret a curve from there. I'm going to be using a Bosch 82mm DBW

Application is actually for an Outboard engine on a boat (4.6L V8) so getting good control at low throttle demand (between say 0-30%) will make the boat a lot easier to drive at slower speeds, super fine control up top is probably not as important

Hi James,

You may find that the 82mm throttle body is a size too large for that engine, especially if it is Naturally Aspirated. This can lead to difficulties in getting a nice throttle response down low as the air mass vs. throttle plate angle changes rapidly.

The larger GM throttle bodies deal with this by having a scalloped pocket on one side of the throttle body that the blade travels in for the first ~25% of its travel, reducing the amount of air mass into the engine at low throttle openings and giving a more progressive response at low throttle demands.

Thanks Stephen,

The 200hp model comes with 60mm TB, (limited to 50% TPS) , the 300hp model is mechanically identical but comes with 80mm TB (and a different tune) we are targeting just over 300hp once tuned with the M150 so I feel like there must be a reason the manufacturer needed 80mm on the higher HP model, I guess we will see! There's a large difference in surface area of the two TBs. I'm guessing that's what that little plate on the 60mm is for