E-gas

[hoveringuy]

My first attempt at Egas didn't go so well, but I learned a few things...

I've got the controller working in closed-loop and I can control the electric TB with the corresponding pedal with great precision. It's silky smooth and I can see that I'll like it... eventually.

I installed it on the motor this afternoon and wanted to answer 2 questions. First, the electric TB has a soft stop at about 3 degrees open. With polarity in one direction the motor will drive the plate open, with polarity reversed it will drive it the rest of the way closed. I didn't know if I needed to drive it all the way closed; would the idle valve compensate for a partially open TB??

The second is that the M50 TB has an idle voltage of .4 volts. The electric one only goes down to .7 volts. What would that do?

So, after installing I started the engine and it revved to 3000 rpm and stayed there. That shows that it needs to be closed 100%.

I sealed-off the throttle body and connected the throttle position sensor to the disconnected M50 unit. The engine started and idled normally and opening the M50 resulted in a richer idle mixture and higher rpms, as monitored on my wideband. So, even though the ECU wasn't seeing increased flow through the MAF it was pre-emptively enriching the mixture because it saw the throttle opening.

So, I need to re-wire my controller to full H-bridge so that I can drive it open AND closed. Not a big deal at all.

I also need to spoof the M50 TB voltages with a dedicated PWM channel working as a digital to analog converter. Not that big of a deal, either.

The cool part is that the electric TB fit perfectly on the M54 and really cleans it up.

This technology will hopefully find it's way to the S54's that currently have mechanical throttle conversions.

[BeirBrennerE30]

thats really cool stuff..

[bmwstephen]

out of curiosity why did you go with an electric TB?

I came from an e46 with an electric TB and after going into an e30 I don't understand why we decided to move to electronic management as I feel a degradation in responsiveness

[hoveringuy]

out of curiosity why did you go with an electric TB?

I came from an e46 with an electric TB and after going into an e30 I don't understand why we decided to move to electronic management as I feel a degradation in responsiveness

1) The M54 TB is 20% larger than the M50 TB which was sized for a 2.5l engine. It should theoretically make about a 2-3 hp difference which isn't a big deal, but the fit will also be better.

2) The pedal is smooth as butter. My cable pedal isn't bad either, but the electric one is superb.

3) The responsiveness is a matter of programming. As in everything else with the M54, it has to do with emissions and the "average" driver. I can actually make it much more responsive by reading the derivative of throttle position. A quick stab will open it more than the actual displacement of the pedal.

4) I can change response curves completely.

5) It's fun watching 1 amp chips explode when you put 3 amps through them!

See www.sprintboosterusa.com for a product that restores the responsiveness. I'll be doing the same thing organically.

[dude8383]

i think you will be the one to lead the revolution.

[hoveringuy]

Forgot to mention

6) This is my training wheels for a possible N52 project in the future. That motor has the fly-by-wire cylinder head that controls intake valve lift directly.

[hoveringuy]

Second try...

I changed the approach completely. The electric TB has a limp home default position where it goes to 5 degrees open when it loses power, I need to drive it closed AND open.

So, with the new full H bridge driver I installed it and got the car to idle.

Now my task is to clean up the noise to keep the PIC from resetting and to change the TB response to the pedal. I learned today that the linkage on the mechanical TB does a great job at controlling the amount of opening vs pedal position. It doesn't open as quickly for the first bit of pedal travel.

I found that with 100% linear TB movement vs pedal it opens WAY to quickly off idle. I need to make it less sensitive at partial throttle.

[daniel]

Forgot to mention

6) This is my training wheels for a possible N52 project in the future. That motor has the fly-by-wire cylinder head that controls intake valve lift directly.

n54! n54!

[jrdeamicis]

Thanks for the updates. I'm happy to see you are working through some of the problems and figuring out solutions.

[BeirBrennerE30]

question... what model is that pedal from? does it matter what pedal you use( are they interchangeable?) i assume they are just a 0-5v potentiometer. This is for a standalone (ViPEC)and the engine i purchased didnt come with its e-gas pedal. I was hoping I could get one that fits the e30 better

[SamE30e]

Forgot to mention

6) This is my training wheels for a possible N52 project in the future. That motor has the fly-by-wire cylinder head that controls intake valve lift directly.

Yea the N52 throttle is pretty intense. It took me a while to figure it out.

[hoveringuy]

question... what model is that pedal from? does it matter what pedal you use( are they interchangeable?) i assume they are just a 0-5v potentiometer. This is for a standalone (ViPEC)and the engine i purchased didnt come with its e-gas pedal. I was hoping I could get one that fits the e30 better

It's not just a potentiometer... it's two and they work in opposition to each other. While one is ramping the voltage up from .5 volts to 5, the other is decreasing from 5 down to .5.

Same thing on the TB. This allows the computer to validate the signal and prevent a short or stray signal from accelerating you unintentionally.

Also, there's no contact in the pedal, it's a rotary Hall sensor. Very
smooth!

I think all current BMW gas pedals work the same, although some are top hinge and some are bottom.

I've got mine working pretty well in prototype form. The issue I'm having now is that my lab power supply trips over 1.5 amps and I need to run it off the battery.

[BeirBrennerE30]

It's not just a potentiometer... it's two and they work in opposition to each other. While one is ramping the voltage up from .5 volts to 5, the other is decreasing from 5 down to .5.

Same thing on the TB. This allows the computer to validate the signal and prevent a short or stray signal from accelerating you unintentionally.

Also, there's no contact in the pedal, it's a rotary Hall sensor. Very
smooth!

I think all current BMW gas pedals work the same, although some are top hinge and some are bottom.

I've got mine working pretty well in prototype form. The issue I'm having now is that my lab power supply trips over 1.5 amps and I need to run it off the battery.

good info... the e39 m5 pedal looks to have the pot/pots outside the pedal attached to a linkage where your pedal (m54?) looks to have everything in one unit. I would like to have the single unit for ease of install but I was afaid they werent interchangeable

[hoveringuy]

good info... the e39 m5 pedal looks to have the pot/pots outside the pedal attached to a linkage where your pedal (m54?) looks to have everything in one unit. I would like to have the single unit for ease of install but I was afaid they werent interchangeable

No, physically they have slightly different designs but the wires do the exact same thing.

What's funny is that mine even has a little kick-down botton at the very end of the stroke, even though it's connected to exactly *nothing*.

I guess it makes people feel good to press that button when they floor it. The result of a $2 million dollar BMW marketing research, no doubt.

[87e30]

Dude, this bad ass.

Your skill impresses me.

I'm paying you to come to Renton if I can't get my m52 wiring figured out.