Ritchie
Club Retro Rides Member
Posts: 765 
Club RR Member Number: 12
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Closed loop auto mapping?Ritchie
@ritchie
Club Retro Rides Member 12
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Recently I have been thinking about upping the power on my WRX Brat and have realised how difficult it is to get anything mapped in my area, so I'll probably not bother.
This bothers me a bit, as I have various ideas about retro stuff with throttle bodies installed.
Anyway, I was thinking, why is nobody (to my knowledge) producing an ECU which will self learn from the inputs which would negate the need for mapping.
If a preset aim of the ECU was to adjust fueling and timing to optimum AFR with no ignition knock as a closed loop system, surely it would just be case of installing the system and driving it until it had observed all possible parameters and you would be good to go. I know standard ECUs do this to a certain extent anyway.
The only reason that I can think of is that it's not possible to get the required level of accuracy for throttle response, idle smoothness etc. without some manual tweaking of the map.
If I remember correctly Holley produce a carb replacement single throttle body with a closed loop system which does this, but it's the only one I know of.
Can anybody with more knowledge on this than me shed any light?
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Last Edit: Jul 25, 2020 7:00:58 GMT by Ritchie
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mk2cossie
Club Retro Rides Member
Posts: 2,948
Club RR Member Number: 77
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Closed loop auto mapping?mk2cossie
@mk2cossie
Club Retro Rides Member 77
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As far as I know, a lot of the current gen aftermarket ecu's do have closed loop learning. The difficulty comes in knowing what parameters to set for it to bat and ball between to self learn and not get itself in a flap  |
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Most aftermarket ecu s including Megasquirt and Speeduino are capable of “self learning” in conjunction with external software such as Tuner Studio. I’ve been using this for 15 years.
It is very cool stuff but it should be emphasised that the resulting map is only as good as your target table and if you get that wrong in the high load/rpm areas there is the possibility of melting things. You will have to tweak acceleration enrichment and warm up enrichment by hand.
On powerful vehicles the other problem is actually spending any time in the high load/rpm areas without crashing or getting arrested.
Ignition timing cannot be handled in the same way, you can get fairly good results on the road (same comments apply re crash/arrest) but an RR is the right, safe way to do it.
Nick
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1967 Triumph Vitesse convertible (old friend)
1996 Audi A6 2.5 TDI Avant (still durability testing)
1972 GT6 Mk3 (Restored after loong rest & getting the hang of being a car again)
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goldnrust
West Midlands
Minimalist
Posts: 1,872
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vitesseefi has pretty much covered it. I will add that the auto tune / self learning features require the rest of your ECU parameters to be set-up correctly, things like injector dead times are often over looked but the auto tune features rely upon these to make it's calculations. You also need to have the understanding to go in and manually adjust the fuel table from time to time. For example if the map is so rich the car misses, then the oxygen sensor will actually read lean as it will see all the un-burnt oxygen in the exhaust, so the auto tune will make the map worse. Similarily, you don't want to be holding a high power/turbo car lean for extended periods of time while the auto tuning software collects its data and makes adjustments, you risk doing damage. So manual manipulation of the map is required at times. Learning to map your own ECU can be a rewarding and interesting process, but its a reactively steep learning curve and you have to be aware that it will be a hobby. It will take you, or I, as an amateur tuner a lot longer and a lot more hard work to get a tune close, compared to what a professional can do on a dyno in a few hours.
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Jul 25, 2020 11:44:07 GMT
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Good points raised above. I will also add than when I first mapped my Vitesse megasquirt in about 2004, I did it with a narrow band O2 sensor, data logs, seat of the pants and occasional "guest driver" to pilot the thing while I fiddled with the laptop. It took ages and burned alot of fuel. However, when I did finally fit a wideband O2 sensor, I couldn't find much to improve on, and when I finally did take it to a rolling road (the excellent Tipton Garage in Devon), he couldn't find much to change either.
However, lessons were learned and when I converted a 2.5PI in about 2011 I put wideband in from the outset and used the Tuner Studio autotune function straight away. It works like magic and provided your initial target table is something like right you can feel the thing waking up and coming alive as you drive it around, trying to cover all parts of the map (a challenge in itself!). I also went to the same rolling road fairly early on and it was an real eye opener just how quickly the high end mapping and ignition timing could be done. We were finished in a couple of hours and did find some more power on that occasion as well as getting best timing timing dialed in in the cruise areas to maximise fuel economy. While it might seem pricey, a good RR and operator (the operator is key!) will probably cost you less in the long run.
Nick
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1967 Triumph Vitesse convertible (old friend)
1996 Audi A6 2.5 TDI Avant (still durability testing)
1972 GT6 Mk3 (Restored after loong rest & getting the hang of being a car again)
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Ritchie
Club Retro Rides Member
Posts: 765
Club RR Member Number: 12
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Closed loop auto mapping?Ritchie
@ritchie
Club Retro Rides Member 12
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Jul 25, 2020 11:47:44 GMT
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Great info lads, thanks very much.
It's not the expense of the mapping, it's finding somebody to do it.
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