E-gas

[hoveringuy]

Take 3...

getting better.

I've been wrestling with the stupid detent position on the throttle body trying to finesse a solution that would let it open and close without the detent making it too jerky. I was trying to drive the motor in one direction at a time only.

Finesse is out.

I changed it to complementary PWM where the motor is driven in both directions AT ONCE. (actually, it switches directions at like 500Hz) It's in a constant tug-of-war with itself but the detent basically becomes invisible.

The downside is that the MOSFET gets much hotter because it's delivering 4x the current.

So, engine idles pretty nice and responds to the Egas pedal smartly. The pedal is also mapped so that it's not super sensitive off-idle like it was before.

I'll do some more smoothing on the controller and beef-up the heatsink on the MOSFET before I do the first driving test. It'll be like a handicap car with the gas pedal hand-controlled. Should be fun!

Throttle cables still rule for now.

In the picture I have the M50 TB moved aside and the electronic TB installed. You can also see my brake booster clearnance with a 320i booster.

[hoveringuy]

E-gas now road tested, mostly successful.

This has been on the back burner for the past several months but I discovered there's a plastic tab on the back of one of the electric TB gears that can be removed so that it closes all the way without the 5 degree "limp home" detent.

That allowed me to reconfigure the the motor drive circuit and I could smoothly open it and close it. I also biased the TB feedback voltage to match the M50 TB voltage at idle.

So, installed it and it idled perfectly. Revved nicely with the electric pedal in the garage so I took it for a drive. Here's what I learned:

1) It's hard to drive with the gas pedal in your hand.
2) E-gas is smooth with great finesse and precision of control.
3) My mapping for pedal position to TB position is perfect.
4) 413 ECU was happy with it.
5) Cat-5 cable: it's not just for your network.
6) You really could be a backseat driver...

The problem I had is also siginificant. I am depending on the spring to close the throttle plate. That takes about 1/2 second.

Not fast enough!

On a hard 1-2 upshift the TB would still be closing when I depressed the clutch and the motor would rev in the middle of the shift.

The M50 TB snaps closed in about .1 second or as fast as you can release the pedal.

So.. I need to go back to full H-bridge so the plate can be driven closed.

It sure was fun!

[FredK]

Your work never ceases to amaze me!

[balooshinakus]

Pretty sweet Steve, I'll have to check this thing out again sometime.

[Tchao]

M10 DBW:

http://www.e30tech.com/forum/showpost.php?p=921489&postcount=480

[Jean]

Dude this is cool! I normally hate how the DBW cars "feel", but like you said it's probably in programming and can be fixed?

[Wh33lhop]

Very cool Subscribed.

I remember the valvetronic engines typically had a throttle body in the intake path "just in case" that was normally kept at WOT... kinda defeats the purpose of valvetronic, doesn't it?

[hoveringuy]

This is a fun project but I also would like to run the stock M54 TB. If the M54 is a 3 litre and came stock with a 70mm TB with a 3 1/2 MAF, I wonder why the S50 has a 64m TB with a 3" MAF?

[hoveringuy]

This has been a back-burner project, but I've made a lot of progress on it and finally completed the CAD to commit this to circuit boards.

Size is 2 3/4" x 2 3/4".

Prototype in 2 weeks?

[Voluted]

Just to comment quickly on that button at the end of the pedal path (fully pressed down):

I used to drive an e39 540i with the 5 speed auto with tiptronic. That button at the bottom, when pressed, would automatically shift the transmission to the lowest gear possible no matter what mode the transmission was in.

Eg. Transmission in 'tiptronic' or manual mode in 5th gear. When you floor it w/o hitting the button it stays in gear 5. If you press a bit more to hit that button it would override the driver's choice to be in 5th gear and switch to the lowest possible gear for the car's current speed.

This doesn't help you at all with what you are doing but i thought i should point it out lol.

Sweet projects btw; i always enjoy reading your threads.

[87e30]

So you have it all completely working?

One more step towards s54 swaps everywhere?

[hoveringuy]

So you have it all completely working?

One more step towards s54 swaps everywhere?

It works well enough that I'm ordering some proper circuit boards for it. I don't want anything sketchy running my throttle if I'm driving.

This would work just fine on the S54. I have made it massively heat sinked for reliability. It would replace the need for a bellcrank conversion with standalone.

[george graves]

Very cool! Looks like you found a nice h-bridge too. This is really cool because you can basically program into the gas petal a "feel." All the auto makers do it to some extent. Back in the day you'd do it with a cam shaped throttle body actuator. Very cool stuff.

I might have to PM you and pick your brain regarding power filtering.

[Fusion]

Wondering if the TB is from an automatic?
My Benz's throttle position sensor knows only 3 positions - idle, neutral (auto in N), full throttle. I guess because in Drive the idle rpms have to be a tad higher to hold the load without dieing. If the TPS finds any irregularities it puts the engine into limp mode.
Not sure if this is of any help to you, just my 2c.

Edit: damn, didn't notice the second page.
Good job, sir.

[hoveringuy]

Circuit boards are back from fab; everythings fits and works.

I'm bench testing the crap out of it; randomly disconnecting and shorting wires, having the cat piss on it, running it under the blow dryer.

This will be Toyota quality.

No, strike that.