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Speeduino – Rover SD1, Quirky Tuning

It’s been a while since my last update, so here’s what I have been up to.

I have now done about 240km on Speeduino, with constant tuning and tweaking of the ECU. For the most part, its driving really well.

Important disclaimer. Please remember that these settings are ONLY suitable for my own car. I can tell and feel what it does and doesn’t like, and the results may be undesirable if used on a different car. I post these here to explain how and why I am doing things to my car. Take my advice for what is it, and use it to find settings that work for you.

There isn’t much to show, but the seat-O-pants meter tells me it’s running a lot better than the old Lucas ECU, not to mention that if the current rate of fuel consumption continues, I should be looking at a decent reduction in fuel consumption from the Lucas setup. To think, I may be getting better fuel economy from the Speeduino than the Lucas, and I’m driving the absolute hell out of the Rover trying to hit as many tuning cells as I can.

I have had a couple of little issues. I have previously mentioned my troubles tuning the Acceleration Enrichment. I decided the other day to completely disable AE, and see what happened. The results were clear, the car drove a lot better, with a complete absence of any form of bogging when accelerating. I did note that the AFR did swing a little lean for a second when accelerating. This indicated to me that AE was still needed, just to iron out that lean out, but it needed to be a small amount.

This is what I have settled on for now. It’s enough to counter it leaning out, but not so much that it causes the over-rich bogging.

TPSdot is basically a measurement of the rate of change in the throttle over a period of time. The quicker you open the throttle, the higher the TPSdot will be. Even if you go Wide Open Throttle, slowly, the TPSdot will be lower than if you opened it half way really quickly. If you open the throttle quickly, the engine gulps a huge amount of air in a short period, so needs a quick shot of fuel to counter that. AE is much like the old school tuning of the carb accelerator pump.

I still have some tweaking to do, but now its at a point where it doesn’t bog no matter how big or quick the throttle opening is.

The other issue that came to light today was that the Inlet Air Temp sensor has been spiking randomly, and causing huge bogging as the IAT compensations kick in, and retard timing and cuts fuel.

You can see it in this log capture

The very bottom yellow line is the IAT reading. It goes from about 21 Degrees (normal) to about 178 degrees. You can see the overlapping red line, which is the AFR reading, goes very lean at the same time (higher is leaner). Above it, the green line that takes a dip is ignition timing, which is being hugely retarded. The very top white line is RPM, which you can see has a corresponding dip, where the car bogged down and made me go “wtf just happened”.

Heres another time it happened

My trusty assistant was watching the Tunerstudio dials at the time and noted that the IAT gauge was all over the show. The high point in that graph is 175 degrees! This was a good indicator of what was happening, and where to start looking.

Later on in the day when I was checking my timing (more on that soon) my trusty assistant was once again watching the dials whilst I plugged the injector resistor pack back in (which is beneath the IAT sensor) and noted the IAT gauge went crazy. With her watching the gauge, I started to wiggle various bits of wiring until I narrowed it down to the IAT plug itself. When I purchased the sensor I got the plug as a pigtail, not as a bare plug with pins (like I should have) and I soldered the wires to the loom. As it turns out my soldering on the ground wire for the sensor was a bit rough, and the wire had worn through the self amalgamating tape (Yes, i should have used heat shrink but i forgot) and was shorting directly to the signal wire. A quick tidy up with some snips, and wrap with more tape, and back into the braided sleeve it went. No more issues since. Such a simple thing, but a pain in the backside.

Speaking of checking the timing, there is one thing I have been a bit curious about since I fit the Speeduino. When I did the initial setup, I used the timing pointer on the engine to check TDC. I did a rudimentary check of cylinder 1 to see if it was at the top of the cylinder. It sort of worked out at the time, and I set my base timing to that. I had my trigger angle setting at 157 ATDC.

I was never really convinced the TDC was correct. Today, I decided to check it properly.

I removed cylinder 1 spark plug, which looked pretty good

Introducing Chopstick-cam (patent pending)

Connected to my phone

And then stuck the camera in the spark plug hole.

So apparently the crown of my piston is covered in a nice layer of carbon. MMMmm.

Using the chopstick-cam, I checked when the piston got to the top of its stroke.

And from there, I checked where the pointer was when the engine was at TDC.

Ah. Ok, well that’s not ideal. The TDC mark is above the pointer in the photo. The pointer is about 5 degrees ATDC. So that throws my whole spark map out by 5 degrees. Woot.

Since I knew where TDC actually was now, and the pointer is adjustable, I backed the screws off an adjusted it. Damn, now the pointer contacts the back of the pulley. The trigger wheel has pushed the power steering pulley closer to the engine, and it doesn’t clear now.

I removed the pointer, and filed it down until it cleared.

Now that it cleared the pulley, I installed it correctly

And using my trusty 10+ year old timing light (purchased for my Marina), I checked the trigger angle.

With the cranking angle set to Zero, I needed to back the timing off to 152 ATDC for the TDC mark to line up again.

So, did it do anything? Yes. The car feels more lively, and a bit smoother to drive. The VEAL is also taking big whacks out of the fuelling again, so obviously the timing difference is enough to make a difference. It still doesn’t start easily when warm, but I think that’s something I will need to work on gradually.

This is my current spark map

Its based loosely off my research of other Rover V8 engines running Megasquirt, and what my car likes. You can see that below idle (the 600 and 800RPM columns along the bottom) take a big jump up in timing advance, I built this in to help with the idle when in gear, and with other load on the engine (PS, lights etc) so it wouldn’t stall. An advanced timing makes the car run stronger, and increases RPM. The higher the number, the higher the ignition advance in degrees.

It’s not an overly aggressive map, but the car seems to like it. I have tried a couple of different maps out, and this is the one my car likes the most. I will start working more on the ignition timing map once I have the fuel dialed in more.

My fuel map is all over the place

Once again the idle cells have been manually set to what the car likes, based on how it feels. I have the idle at a nice solid tickover at about 1000 +/- RPM, and 800RPM in gear. The rest of the map is a combo of the table generator making a base map, me manually tweaking various parts, and then using VEAL to change the map to what the car needs. There are a lot of cells I have not had VEAL touch yet, so my mission is to keep trying to push the car into weird running conditions and see if I can hit them. This means a lot of up hill driving at high RPM with my foot on the brake to load the engine up. The table is all about Volumetric Efficiency, but long story short, the higher the number, the richer, the lower, the leaner.

So whats next? Well, I’m still going to be working on the maps for a long time yet, and I need to fix hot starting as its taking its toll on my battery cranking over and over. The battery was on its last legs anyway, thanks to the previous owner letting it sit flat for a week, so that’s on the list of things to replace before I leave my current job (where I get staff/trade prices).

Other than that there are a few other things to want to look into, like blocking off the plenum Over Run valve, as I think it’s giving me an overly lean mixture on decel, and I would rather alter that via the ECU than the mechanical setup that uses. I still need to look into the horrible resonation from the intake too, its loud and gross.

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