Spent the last couple of days sorting the idle out. Still won’t start without throttle but it’s happy enough after about a minute. I’m not turning the idle control valve on or anything yet so that it doesn’t interfere with the ‘auto tuning’. I’m reluctant to call it autotune, because that’s the feature of different megasquirt tuning software but it describes it far better than “VE Analyze Live” (VEAL). What VEAL does is essentially map the car whilst it’s driving. It looks at the target AFR for whichever cell is being driven at the moment, then either removes or adds fuel until it’s hit.
So, I’ve set target AFRs according to manifold pressure against revs, aiming for safe figures from 14.7 at cruise to 11.5 under boost. I’ve also retarded the timing to help keep that safe too. Lastly, I set the initial fuel table quite high, thinking it’s safer to run rich than lean initially. Obviously, I’m not trying to make power here, just get it safely drivable for Thursday when I go to get it mapped.
Stu popped around this evening to play wingman and watch the laptop whilst we embarked on a bit of road mapping. I’d prefer to keep both eyes on the road than trying to watch the lambda gauge on a laptop! After pushing it out of the garage and firing it up, it suddenly became quite clear at just how quiet it was. Before, I’d only had the engine running in the garage but now with considerably less for the noise to bounce off it was more production car noise levels! Noise tests shouldn’t be an issue for me…
We started off on a quiet half mile stretch of road, doing a few 30-40mph runs in 3rd, 4th and 5th gear. Each time the results were the same, starting rich with the software adjusting it to the target AFR in a few runs. We then did a dual carriageway run to simulate the kind of drive down to the tuners. Again, started a bit rich but was brought into tune. When new cells were entered though (approaching positive boost), it was excessively rich to the point of making the engine stumble.
Back to the industrial estate for the same tests as before but with slightly wider throttle openings. Again, same thing found… as it entered new cells it was far too rich. Onto some local roads and then pulled up in a pub car park to compare what values the cells had now to when they were initially set. With it running epically rich on the untouched cells, we manually pulled 20% of the fuel out of them and started again. This time when entering new cells it would still be rich (10:1), but drivable so the software could deal with it. Plenty more runs, including some in boost but never more than half throttle opening. Each time the car tuned itself happily, and in the end we called it a day because I was getting a bit too confident!
Although the car isn’t properly mapped, running rich and timing at very safe levels it’s obvious it’s going to be quick. It happily boosts from below 2k rpm in the higher gears and builds speed very quickly.
Can’t wait for mapping on Thursday now!
Just a shame it uses so much fuel…
Here’s a video from the day after the above, on an extended trip to get petrol for proper mapping.