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Help with building your Speeduino, installing it, getting it to run etc.
By JoostXT
#44581
PSIG wrote:
Mon Aug 03, 2020 8:07 pm
JoostXT wrote:
Mon Aug 03, 2020 3:06 pm
… The vacuum point is actually almost exactly 1,5'' from the throttle plate and feeds directly into a large symmetrical plenum, so this must work pretty well.
You may have to test for the most stable MAP location in your manifold, typically away from the inlet and runners, but dynamics can be weird.
JoostXT wrote:
Mon Aug 03, 2020 3:06 pm
This brings up an interesting issue though; whilst cruising at 3000rpm I'm at 90kPa, so I want it to be quite lean to gain some mileage. …
Also, this engine seems to like a lot of timing, I'm up to almost 40 degrees high rpm cruising which seems a bit high to be honest.
90kPa is oddly high for cruise, but could be your MAP source point or the MAP mode. Generally, from best-torque fuel Lambda/AFR at stable cruise, lean to the point that you feel lean surge (slow push-pull feel), and enrich just out of it. Check MAP. Don't be surprised if it's higher, as lean is actually less efficient (assuming it was originally fueling for max torque).

In order to recover efficiency at the new Lambda; at stable cruise again, begin slowly testing timing advance until timing is at minimum value for MAP just at minimum value, indicating peak timing efficiency. Advance may be quite high relative to power Lambda timing, in order to compensate for the change in cylinder pressure rise rate. The table cell may change during this exercise. See where that gets you. Don't forget you are tuning for best target performance (and resulting Lambda) at any point, not a Lambda number, which is only a reference.

David
90kPa is high, I agree, but I've had this car for years on it's original ECU and a boost gauge T'eed into the boost sensor port (it had a boost sensor and hotwire MAF) and it always saw almost 0 bar/1 atm at 120kmh cruising. It also saw consistent 0,7bar boost pressure which is stock gate pressure so I'm inclined to believe the sensor/gauge.

I think it's due to the small but very inefficient little 80s turbo that is on there. It starts to build boost as low as 1900rpm but doesn't actually attribute to any power gains until above 3000rpm. And after 5k it starts tapering off and heating up significantly. I guess it's mostly there for bragging rights (it has "TURBO" stickers all over the car :D)

Something new to consider; I noticed 10 PSI (!) fuel pressure difference between hot and cold engine, engine off. This seems like a lot! I think heating up the fuel would make it thinner, but the tank is full (60L) and the ride was only 20min so I don't think I could heat all that fuel in that amount of time? Maybe the regulator is bad?

edit; forgot to say, thanks for the sage tuning advice, I'll have to have someone else driving, but it's the best way forward!
By JoostXT
#45023
If anyone is still interested; I've just done 3000+km faultlessly, averaging about 11km/L @ 130/140kph, which is better than the stock ECU could ever manage. One of the biggest gains was realizing I had about 10degrees ignition latency @ 4k rpm and adjusting for this. This resulted in an amazing gain of power, torque and fuel economy. I've also come to the conclusion that the stock alternator (55A) is not strong enough for the added power draws of the big fuel pump, fans, idle valve etc. so I need to upgrade to get a more stable voltage.

Sadly though, the hiccup is still there :( I am in the process of swapping the stock igniter for a BIM124 to hopefully loose the latency and maybe fix the hiccup? I have noticed that it seems to happen more at load changes than at steady state, it could happen 5 times in a row whilst slowly accelerating and then nothing for minutes on end whilst cruising.

I've added the current MSQ, keep in mind the ignition map is greatly increased to remove the latency; 5 degrees @2k rpm, 10 degrees @4krpm, 15 degrees@6krpm
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By JoostXT
#45055
theonewithin wrote:
Thu Aug 27, 2020 10:24 pm
What is this "latency" you are talking all the time?

I'm sure you mean something else but are using the wrong term.
https://en.wikipedia.org/wiki/Latency_(engineering)

https://www.youtube.com/watch?v=H_oYAEMGZS0

It is a very normal term to indicate the demanded timing of (for instance) 20 degrees is not what you get due to losses and inefficiencies in the system (mechanical and electrical).

In my instance, the locked timing @ 20 degrees advance, turned out to be 20 degrees at idle and 10 degrees at 4000 rpm. To make sure the timing you input in the ignition table, you need to compensate for this inefficiency. The best way would be to add a separate table for this (hint hint developers!)
By JoostXT
#45061
jonbill wrote:
Fri Aug 28, 2020 8:37 am
Why would you run locked timing at 4000 rpm? do you see this behaviour without locked timing? I don't.
This is merely done as a test to see if the demanded amount of ignition advance is actually what I get in the real world. Since latency is more prominent at higher RPM this is were I test.

When you unlock the timing it just follows the ignition table so you won't be able to see the latency. You could in theory create a ignition map with all cells at the same values, but this would yield the same results as locking the timing.

Just to be clear, I only lock the timing when testing, in normal driving I use the ignition table.
By jonbill
#45063
OK, but when my table commands 34 degrees of advance at 3500 rpm and at 8000 rpm, and the advance I measure with my timing light is 34 degrees in both cases, where is latency/error you describe?
By theonewithin
#45066
jonbill wrote:
Fri Aug 28, 2020 10:32 am
OK, but when my table commands 34 degrees of advance at 3500 rpm and at 8000 rpm, and the advance I measure with my timing light is 34 degrees in both cases, where is latency/error you describe?
Propbably either testing method or its a bug in the firmware.

Try the timing table trick .See if you get the same results.

The "drift" which is actually what it is called is no where near that bad.

You are doing something wrong in your testing or locked timing is bugged (considering it's not meant to be used at high RPM so it may never have been tested there).
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By PSIG
#45085
Keep in-mind that there are many factors that can cause timing drift or latency, such as various tune settings, reversed VR sensor polarity, gear or chain/belt-drive clearances, sensor lag, input circuit components (e.g., capacitor values), etc. Just sayin', so nobody runs down a rabbit hole if it's not necessary. Perhaps one of you could lock your timing and test with a light to confirm or eliminate that possibility. I have heard of that problem rarely and randomly, but new bugs can pop-up any time. <shrug>
By JoostXT
#45089
theonewithin wrote:
Fri Aug 28, 2020 12:10 pm
jonbill wrote:
Fri Aug 28, 2020 10:32 am
OK, but when my table commands 34 degrees of advance at 3500 rpm and at 8000 rpm, and the advance I measure with my timing light is 34 degrees in both cases, where is latency/error you describe?
Propbably either testing method or its a bug in the firmware.

Try the timing table trick .See if you get the same results.

The "drift" which is actually what it is called is no where near that bad.

You are doing something wrong in your testing or locked timing is bugged (considering it's not meant to be used at high RPM so it may never have been tested there).
Drift and latency are two different things with a similar result, so please, before plainly stating I (or someone else) is simply wrong, make sure you know what you are talking about in the first place.

If your table commands 34 and you get 34 this just means you have a well engineered system and this is a good thing! All the components in the chain from ATmega to sparkplug contribute to drift and latency. The drift/latency from the electronic parts on the speeduino are probably negligible, but the (in my case) long old wiring harnass, 1 single old coil and distributor and vintage transistor based igniter all add up.

To further prove my case (and in my continuing search for a smoother running engine) I've replaced the old transistor based igniter with a 'modern' BIM124 which is probably MOSFET based and lost 5 degrees of latency! No other settings were changed.

I think all systems could experience some sort of lag/drift/latency/whatever and it would be nice if speeduino would have some sort of compensation for it. Just upping the spark map will work, but it's a workaround.
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