[lukej]

You can get a stepper motor driver for a few £. A very small pcb & a few components. That takes the load off the ECU.

Would this be suitable for drive by wire throttles?

 

[psimitar]

Would this be suitable for drive by wire throttles?

Drive by wire throttle bodies don't use an idle air valve as the motorisation opens the throttle blade for idle. This is why the ECU does a calibration of the throttle pedal so it can check where throttle pedal takes over from idle position of the throttle butterfly.

 

[lukej]

Yeah I understand that.
I'm asking if the stepper motor tech is what is applied to a throttle shaft. Ie, can regular throttles be adapted to DBW.

 

[al_kaholik]

I guess if the ecu can handle doing the calibration. Hal tech support it natively but with existing DBW pedals and TBs

 

[gojira]

Would this be suitable for drive by wire throttles?

That was my first thought when I read it, but you'd need an ECU that can handle the throttle (pedal input and throttle output), in which case you probably don't need the separate driver.

I've had cars where a throttle cable has snapped, and also cars that have had ECU problems so I'm not sure what I'd trust more to be honest. Drive by wire makes a lot of sense if you're running a 600hp v8 so you can map it for sensible driving and full hooning, not sure it's so useful on a 50hp beetle engine.

 

[dc66]

When I had the Polo tdi engine in the beetle I used the DBW throttle box, connected to the original pedal. It worked great, no cable drag etc. But then I was using the Polo ecu.
I too have had cable and drive by wire failures. On the whole, I would choose to have a cable fail than the electronics. Its obvious when the cable breaks, but a DBW failure could be the pedal, wire, throttle body, or as was the case on my failure, a faulty clutch micro switch. It took me a while to diagnose that one, thanks Fiat! Lol
The Megasquirt ecu I'm using doesn't support DBW so it's a cable by default.

Ordered the Innovative wideband lambda sensor kit last night. I ordered one with a gauge so I can possibly use it to set up the carbs currently on the engine. Why? Well, I maybe using this as my daily before I have finished collecting the parts for the FI conversion. I haven't run the engine far with the twin solex carbs and can't find any info on jetting, so a gauge will be a useful guide. Along with plug colour and how it runs etc.

 

[psimitar]

Yeah I understand that.
I'm asking if the stepper motor tech is what is applied to a throttle shaft. Ie, can regular throttles be adapted to DBW.

The stepper motor is a separate part to the throttle butterfly. It opens a valve on a channel that goes around the throttle butterfly. So on a cable throttle the butterfly is fully closed and it's the stepper motor that allows air flow through this extra channel for sufficient air for idle speeds. You can adapt a normal throttle body to be DBW but for the cost of an actual DBW throttle body it's not worth the effort as you need a larger motor for the throttle butterfly with custom fabrication to make it fit a non DBW throttle body.

A DBW TB is a totally different motor to a stepper motor as it has infinite positions. Been ages since I did industrial electronics but from memory the stepper does just as the name suggests and steps between discreet points on a sensor wheel. DBW uses a feedback loop on infinite position sensors to ensure the motor command matches the two sensor feedback loops to within a <0.1% error.

 

[dc66]

I splashed out on a wide band o2 sensor kit...

And welded the thread for the sensor in near the input from num er 3 cylinder. We will have to wait and see how well it works

The kit comes with a gauge, so I'll try it out with the carbs first. I'm really interested to see how the jets are. They are stock solex 30 pict 1 carbs, each jetted for a 1300. Essentially each one is now feeding a 800cc engine so it should be over jetted. But, the airflow is reduced so the venturi effect is pulling less fuel through. So, as I said, it will be interesting to see what the gauge says

 

[dc66]

Today I've wired up the sensor and gauge.

Once the engine warmed up I was getting 12.7 at idle and 22.0 when holding high revs.

I think that means it's rich at idle and way too lean at high revs. I think! I can't drive the car to road test it at the moment though.
This is on the twin carbs, not injection.

I'm positive I need the injection system now! Lol

 

[dc66]

Back to the inlet manifold.

I used an offcut of 1 inch steel round bar to make the injector mounts. First drilled to 9.5mm, then cut and shaped to the curve of the manifold.
I wanted to position them so there is a straight as possible path to the head.
The inside of the piece needed some work. The fuel will spray in a fan shape, so I had to remove material to allow for this.

Then a corresponding hole was cut in the manifold and TIG welded together.

Looking down the hole

That's one side done. I'll do the other another day. I will also need to fabricate a bracket to screw the fuel rail to.

I'm using injectors from a mazda mx5 1.6. They are easily available, the right flow and impedance. They also do upgrades for racing......lol
The fuel rail is from the same car. I ordered it yesterday along with the stock fuel pressure regulator. It's steel so I can cut and weld it to suit.

 

[dc66]

All that welding on the outside of the manifold bend will have caused the shape to change. As it cools the metal shrinks slightly, causing the end to pull out.

Well, that's what I'm expecting anyway!

If it has, I'll just heat the inside to cherry red to pull it back. I'll know when I trial fit it on the mock up engine.

 

[dc66]

^^^^^ nope, it hasn't moved at all. Happy days!

 

[dc66]

Second injector boss fabricated and welded in.

Once the Maxda fuel rail arrives, I can modify it to fit. Then I need to work out a throttle linkage.
Once I've done that I think I'm ready to put it all together.
Things like the air filter I'll leave to last.

Oh, just thought, I need an air temperature sender.

 

[dc66]

The fuel rail is now done.


As it arrived.

The various bits are brazed on rather than welded. This means that any welding I do needs to be away from the brazed areas otherwise the heat could melt the braze. So I had to get creative with the brackets!

I decided to connect the two sides with solid tube, with a central brace. That keeps it all square and snug. It does, however, cause a possible issue with the throttle cable route. I'm probably going to be using a long Bowden cable so it shouldn't cause too much of a problem.

 

[lukej]

Nice progress, are you planning to make some spacers for the fuel rails for the bolts to snug down on. The injector shouldn't be clamped as such, just held captive between the inj. boss and the fuel rail imo.

 

[dc66]

Nice progress, are you planning to make some spacers for the fuel rails for the bolts to snug down on. The injector shouldn't be clamped as such, just held captive between the inj. boss and the fuel rail imo.

I did think about that. Now I have the lengths I can make something to replace the bolts. I realise the injectors shouldn't be clamped down.
I also thought about a lock nut at the bottom. Proper spacers will look better and be "right".

 

[dc66]

I found some material to make some spacers up

 

[lukej]

Nicely done

 

[gojira]

I was about to ask if you'd considered that the engine might 'grow' as it warms up - but I realised your rigid fuel rail is connected to a rigid manifold, so it doesn't matter.

 

[dc66]

Time to mount the trigger wheel to the pulley.

I bought the toothed wheel, life's too short for me to make that bit! It's a 36-1 wheel, ie 36 teeth with one missing.
I'm assuming the sensor will work better if the toothed wheel is spaced away from the pulley. So I made up Some spacers for it.

At this point I was tempted just to weld it to the pulley

But I didn't want to put too much heat into the pulley in case it warped. Nobody wants a wobbly pulley!
Instead I welded some tabs on, drilled for m6 bolts.

The orientation of the toothed wheel is only important if I use the ecu to control the spark. Since I may well do this at a later date, I set the wheel accordingly. First I found true tdc for #1 by using the old "bolt down the plug hole" method.

Then aligned the 9th tooth with that point on the pulley. That makes the sensor 90 degrees after the missing tooth at tdc. That's if the sensor is mounted at the timing mark on the case, which it will be.

I marked out and drilled the pulley for the mounting bolts, tacking the heads in with the TIG.

On monday I'll get the chap opposite me to stick the pulley/wheel assembly on his lathe to tidy up any run out from the teeth. Im interested to see how close i got it! Lol

I just need to work out a bracket to mount the sensor now.