Back in beige

[jamie]

Got the car running this evening. It idles and revs pretty nice, albeit quite rich.

Next I need to fit a wide-band O2 sensor to the exhaust, put it all back together, and it's ready to take out and tune.

[sladey]

Nice one Jamie

[neilbardsley]

That was quick. No flies on you.

Great photo too

Sent from my Redmi 7 using Tapatalk

[jamie]

You're posting pictures for me because I'm too lazy!

I just got the air filters installed, so it looks like a complete engine again. I'll post some shots of the setup.

My Innovate LC-2 wideband O2 kit arrives tomorrow. I need to weld a bung onto the exhaust to hold the sender. This is the updated version of the LC-1 that I used when I converted my 1972 911T to EFI back in 2008 or 2009.

I encountered a weird situation where I would turn off the car and the engine would stay running. After a bit of chasing with the multimeter I discovered that the tach was backfeeding three volts down the line that energised the relay that sends 12v from the battery / alternator circuit to the injectors and ECU. So the pump would stop (different relay, unaffected), but the ECU and coil packs would continue to function, and the engine would run for several minutes, sucking up all 43psi of pressure that was left in the fuel line. I solved the issue by adding a diode to the 12v feed on the back of the tacho, so now it will send 12v one way, and no volts the other.

Driving impressions so far - the car is not mapped yet, and all that I know is that is running rich at idle and is difficult to start once it has warmed up. Other than this it drives great. The throttle-bodies are a bit quieter than the Weber IDFs that they replaced, and there's a significantly smoother feel to the power delivery. The Webers had a kind of snappy 'bark' to them which was neat when I first got the car back on the road, but became obnoxious over time - especially on long journeys.

I think I'll miss the carbs for the first five minutes of every trip, then be glad as hell that they're gone for the rest of it. Gettin' old.

Not feeling that there has been a big jump in performance, just as I didn't feel that big a difference when I went to twin-spark, but perhaps a bit of tuning will help that.

This engine certainly is an oddball now. 1883cc with crank-fired twin-plug ignition and throttle body fuel injection running off a Microsquirt ECU. The heads were ported and flowed, and fitted with big valves, so I guess the case is the only original bit of Porsche left, and even that isn't 912 - the number shows it to be from a Super 90.

The problem I'm having is that I drove a '69 911E a few weeks ago and it really set my balls on fire. I'd forgotten how good Mechanische Einspritzung is - combined with a small-displacement, high-revving engine, it's just absolute poetry.

Luckily I'm near the end of a wallet-raping house extension build, so there's not much I can do except plod on fiddling with this silly little four-banger science fair project.

[jamie]

I expect I will EFI this one as well. Got to be done!

Me, this thread
2012

[hot66]

Sounds a great little motor Jamie ... but a high revving 6pot would be fun

[Lightweight_911]

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Good to see you're still lurking here Jamie - & still modding/enjoying your car.

However, there's something missing from your recent posts ....

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- where are the pictures of the inevitable injuries you've sustained whilst 'tinkering' ?



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[Bootsy]

and near death scrapes...

[Darren65]

....great to see you're doing well in the States Jamie, how many petrol stations do you have in total?

[inaglasshouse]

The problem I'm having is that I drove a '69 911E a few weeks ago and it really set my balls on fire. I'd forgotten how good Mechanische Einspritzung is - combined with a small-displacement, high-revving engine, it's just absolute poetry.

Yep!
Next time you are in the UK (we can dream of travel, right?) come and borrow my 69 S for a day or two...
But your car is awesome, too. EFI mods are interesting, and seem to offer endless scope for tinkering (always a good thing!) Thanks for posting.
Take care, wear sunscreen.
R

[jamie]

Well, I wasn't that impressed with the conversion. It ran pretty well straight out of the gate, giving the impression that it was already somewhat tuned. But it was a bit flaccid.

Little did I know, I had one last step to complete...

An explainer, for those that aren't into this silliness - there are a couple of way you can tune an EFI engine, but the easiest way is to use a 'wideband O2 sensor', which screws into the exhaust pipe and outputs a voltage (via a small controller) depending on the air/fuel mixture blowing past it. You can display this output (expressed as 'parts of air to one part of fuel') on a gauge, or do what I did, which is to hook it into the ECU to output that figure in your tuning software.

You can then tell the software what your target air/fuel ratio ('AFR') is for varying loads and RPMS, and express this on a table. The base AFR is 14.7 parts of air to one part of fuel, although that's not much use on an aircooled motor except for light cruise - you want to be richer than that in almost every other scenario. On my software the AFR table is 16x16 points. More sophisiticated software has more points, but this engine doesn't need that level of finesse - what I have is good enough.

Once you have the O2 sensor up and running, you hook up the laptop and go drive the car in a variety of conditions - light throttle cruise to absolute balls-to-the-wall death thrash. The O2 sensor reads what's coming out of the pipe, and the ECU actively adjusts the fuelling to meet the target AFR as laid out in the table. Provided your AFR targets are suitable for what the engine wants, the car tunes itself. You drive a bit, the software shows what it has changed, you confirm and then upload it to the ECU. The ECU then drives on those adjustments and makes finer and finer changes until...

you are at the raging helm of a fire-breathing four-banger from hell.

Or thereabouts.

Slowly but surely, with each click of the upload, the fuelling map is refined. The car is really good now - the throttle is snappy but amazingly smooth, and it pulls much harder than when it was on carbs. It idles at a fairly steady 760rpm and refvs freely up to 6k without any kind of flat spot of stutter. It doesn't have the character that people love about carbs - the snappy bark, the loud induction noise or even any overrun popping and banging, but it does have a different type of character, and it's really good.

Up at 4500-6000 there's a little hint of die Mechanische Einspritzung ASMR buzzsaw, which is neat. Makes me happy. Also makes me wring it out in every gear, so if I write here that the engine has exploded, that'll probably be why.

There's more to go, but I'm really happy so far.

[jamie]

You asked for some nice shots of the car, so here it is at the post office earlier today.

[jamie]

Joking. I'll do some nicer ones.

For now, here's some more crap ones. Wiring in the engine bay needs tidying up.

[911hillclimber]

That is a great write-up!
A hillclimb friend has a similar 'learn while you drive' system on his Rover V8 engined car and it works well.
Most interesting, thanks for the post.

[Bruce M]

One point to be aware of. A key parameter for the auto-tune process is the delay setting for the O2 sensor signal. The software has a lag setting to allow for the delay in the sensor recording the change in mixture. You can test this by logging the O2 against the injector signal. do a hard fuel cut manually & see the lag in the log.