1993 Volvo 240 LS Swap #56

What engine are you torturing? Is it inside some car?
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mck1117
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1993 Volvo 240 LS Swap #56

Post by mck1117 » Tue Dec 10, 2019 7:37 pm

My 1993 Volvo 240 has a v8. That v8 now runs on rusEfi!



That video was shot with no sensors hooked up (other than crank position...), so I had it locked to sensible-ish idle settings of 3.5ms fuel, and 20 degrees ignition timing. It was also only running on 6 cylinders in that video, since the pins for injectors 3 and 4 were shorted together on the pcb. That's since been fixed, and it now purrs on all 8 cylinders!

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Re: 1993 Volvo 240 LS Swap #56

Post by AndreyB » Tue Dec 10, 2019 11:06 pm

https://rusefi.com/s/howtocontribute
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my skype is arro239

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Re: 1993 Volvo 240 LS Swap #56

Post by mck1117 » Mon Dec 16, 2019 5:59 am

Car has now been for a ~half hour drive. No issues to report! Spent some time up above 4k rpm without any sync issues.

Also of note is that AFR was logged using an AEM X-Series wideband controller, connected over CAN bus!

Attached is the log from the drive.
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Re: 1993 Volvo 240 LS Swap #56

Post by AndreyB » Mon Dec 16, 2019 6:01 am

mck1117 wrote:
Mon Dec 16, 2019 5:59 am
connected over CAN bus!
Please PR this part? :)
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Re: 1993 Volvo 240 LS Swap #56

Post by puff » Mon Dec 16, 2019 7:38 am

aren't there delays introduced by using can bus instead of direct ADC?

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Re: 1993 Volvo 240 LS Swap #56

Post by mck1117 » Mon Dec 16, 2019 11:53 pm

puff wrote:
Mon Dec 16, 2019 7:38 am
aren't there delays introduced by using can bus instead of direct ADC?
Short answer: No.

Long answer: Yes, but no.

Longer answer:
ADC: We sample the ADC at 200hz. That's a period of 5ms, so the average amount of time we have to wait from any arbitrary point in time until we get a new o2 measurement is 2.5ms (note: this used to run at 20hz, so it used to be 25ms)

CAN: A CAN message can't be longer than ~150 bits, and transmits at 500kbit/s, which means a full frame can transmit in 300 microseconds (0.3ms). The interrupt overhead and processing on the ECU side adds at most another 100us (0.1ms) (since this is relatively low priority compared to other threads/interrupts). TunerStudio is only polling at ~100hz (10ms period), so this is much much faster than anything can consume it. This particular controller sends CAN messages at 100hz, but that's totally fine since the sensor is slow enough that there isn't any content at higher frequencies than that.

Result: Advantage CAN.

In reality, the CAN-based solution is actually MUCH faster than those numbers would suggest. This isn't because the transport is faster (which it is), it's because the actual wideband controller I'm using (AEM X-Series inline) is SO much faster than their older stuff.

Have a look at this snip from the attached datalog:
Image
You can see this happen, in order:
1. TPS starts opening
2. AFR goes lean (transient)
3. air mass starts increasing (MAP sensor indicates pressure change)

Compare that to this log from my other car, where the AFR lags behind the TPS change (using an older AEM 30-4110 wideband gauge/controller):

Image

So even if the actual transport was slower (which it isn't),

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Re: 1993 Volvo 240 LS Swap #56

Post by AndreyB » Mon Dec 16, 2019 11:59 pm

Interesting pictures, thank you!

Would be interesting to compare these two images to rusEfi basic cj125 implementation.
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Re: 1993 Volvo 240 LS Swap #56

Post by mck1117 » Tue Dec 17, 2019 12:28 am

russian wrote:
Mon Dec 16, 2019 11:59 pm
Would be interesting to compare these two images to rusEfi basic cj125 implementation.
Back when I had a cj125 (internal) and the AEM 30-4110 (external) hooked up to the same ECU with dual sensors next to each other in the pipe, they were essentially identical. The internal controller was maybe slightly faster, but not significantly like the X-Series is.

Also of note is that the X-Series also has a normal linear analog output, which probably provides the same speed benefit without CAN. However, with CAN, you don't have to worry about DC offsets between the wideband and the ECU.

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