87 951 VEMS Install
09-20-2019, 06:40 PM
#511
Three Wheelin'
Guys, I would be careful of arbitrarily changing your ignition timing map based on what someone else has done, especially in the boost range over 100 kpa---you simply don't know what the engine condition/modifications are, and what kind of fuel is being used.
Let's say two different 951s have "stock" engines. That could still mean that one has a shaved cylinder head and/or excessive carbon buildup, which effectively raises the compression ratio.
The bottom line is, you should get the ignition table tuned on a load-bearing dyno to figure out the ideal timing settings for your particular engine and fuel.
All of that said, very advanced timing in the low-load/cruising range is desirable because it increases the engine's mechanical efficiency, and there is no risk of detonation.
Let's say two different 951s have "stock" engines. That could still mean that one has a shaved cylinder head and/or excessive carbon buildup, which effectively raises the compression ratio.
The bottom line is, you should get the ignition table tuned on a load-bearing dyno to figure out the ideal timing settings for your particular engine and fuel.
All of that said, very advanced timing in the low-load/cruising range is desirable because it increases the engine's mechanical efficiency, and there is no risk of detonation.
09-21-2019, 12:12 AM
#512
Race Director
It could prob take more down low honestly as I don't think its as hard hitting as it was with the previous Vitesse MAF in place. The tuner used a load based dyno (mustang) and kept adding timing until it didnt make any more power and then backed it off a bit for safety. Im sure he looked at knock along with power to adjust the timing table for my specific car. I was just sharing as its always good to have more than one data point.
09-25-2019, 03:49 AM
#516
Rennlist Member
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Thanks for all the suggestions. I wish it were as simple as that. Went over all the usual conditions 3 times and finally figured out the issue
After narrowing it down to the wb02.
Turns out my VEMS ECU was earmarked for an LSU 4.2 wideband, but a lot of units were being done at that time in May 2019 and to make a long story short an LSU 4.9
WB02 was shipped with that setup, but the necessary 27K pull up resistor was never installed so the unit was only pushing out 3.7V Nernst to the wb02 (Fine for LSU4.2) and it needs over 4V to function properly for a 4.9. So I soldered in a 27K resistor in series on a wire and soldered one end to Nernst which is pin 13 on the EC18 and pin 28 on the EC28(+5V). I did this on the OUTSIDE of the VEMS unit. Used liquid electric tape to seal since it's now a T connection and it worked well.
Now I am getting 4.5V to the LSU4.9 WB02 which is reading lambda in the correct range.
After narrowing it down to the wb02.
Turns out my VEMS ECU was earmarked for an LSU 4.2 wideband, but a lot of units were being done at that time in May 2019 and to make a long story short an LSU 4.9
WB02 was shipped with that setup, but the necessary 27K pull up resistor was never installed so the unit was only pushing out 3.7V Nernst to the wb02 (Fine for LSU4.2) and it needs over 4V to function properly for a 4.9. So I soldered in a 27K resistor in series on a wire and soldered one end to Nernst which is pin 13 on the EC18 and pin 28 on the EC28(+5V). I did this on the OUTSIDE of the VEMS unit. Used liquid electric tape to seal since it's now a T connection and it worked well.
Now I am getting 4.5V to the LSU4.9 WB02 which is reading lambda in the correct range.
09-25-2019, 06:08 AM
#517
Rennlist Member
If you have a chance, could you measure voltage drop on DME pins 18 and 35. DME 18 goes to Vems ECU 25. I measured voltage drop to 10.8V during cranking with hi torque starter and quest alternator combo. This is with a new battery fully charged at 12.8V. Beginning to suspect, vems ecu is very sensitive with voltage drop which is causing trigger syncing issues with timing, causing startup problems. I'm starting to get it every now and then again. Investigating if it's starter and / or alternator related. I've noticed on good starts, tachometer will Rev to 1200rpm or more. Where as a bad start will be below 1k rpm. It's either the starter is faulty causing a big voltage drop causing vems to be confused. Or voltage drop related to starter/alternator combo. So far I've tried to put an amplifier battery capacitor with ecu but it did not correct issue. Will try a seperate battery ( is this even ok to do?) and report back. Also suspect that my starter/alternator could be faulty as I bought them used with an Ice Shark battery cable here on the list many years ago. So if you have this starter/alternator combo without issues, I would like to know. Much Appreciated. - Wayne
09-25-2019, 06:09 AM
#518
Rennlist Member
Thanks for all the suggestions. I wish it were as simple as that. Went over all the usual conditions 3 times and finally figured out the issue
After narrowing it down to the wb02.
Turns out my VEMS ECU was earmarked for an LSU 4.2 wideband, but a lot of units were being done at that time in May 2019 and to make a long story short an LSU 4.9
WB02 was shipped with that setup, but the necessary 27K pull up resistor was never installed so the unit was only pushing out 3.7V Nernst to the wb02 (Fine for LSU4.2) and it needs over 4V to function properly for a 4.9. So I soldered in a 27K resistor in series on a wire and soldered one end to Nernst which is pin 13 on the EC18 and pin 28 on the EC28(+5V). I did this on the OUTSIDE of the VEMS unit. Used liquid electric tape to seal since it's now a T connection and it worked well.
Now I am getting 4.5V to the LSU4.9 WB02 which is reading lambda in the correct range.
After narrowing it down to the wb02.
Turns out my VEMS ECU was earmarked for an LSU 4.2 wideband, but a lot of units were being done at that time in May 2019 and to make a long story short an LSU 4.9
WB02 was shipped with that setup, but the necessary 27K pull up resistor was never installed so the unit was only pushing out 3.7V Nernst to the wb02 (Fine for LSU4.2) and it needs over 4V to function properly for a 4.9. So I soldered in a 27K resistor in series on a wire and soldered one end to Nernst which is pin 13 on the EC18 and pin 28 on the EC28(+5V). I did this on the OUTSIDE of the VEMS unit. Used liquid electric tape to seal since it's now a T connection and it worked well.
Now I am getting 4.5V to the LSU4.9 WB02 which is reading lambda in the correct range.
09-25-2019, 12:02 PM
#519
Advanced
Thanks for all the suggestions. I wish it were as simple as that. Went over all the usual conditions 3 times and finally figured out the issue
After narrowing it down to the wb02.
Turns out my VEMS ECU was earmarked for an LSU 4.2 wideband, but a lot of units were being done at that time in May 2019 and to make a long story short an LSU 4.9
WB02 was shipped with that setup, but the necessary 27K pull up resistor was never installed so the unit was only pushing out 3.7V Nernst to the wb02 (Fine for LSU4.2) and it needs over 4V to function properly for a 4.9. So I soldered in a 27K resistor in series on a wire and soldered one end to Nernst which is pin 13 on the EC18 and pin 28 on the EC28(+5V). I did this on the OUTSIDE of the VEMS unit. Used liquid electric tape to seal since it's now a T connection and it worked well.
Now I am getting 4.5V to the LSU4.9 WB02 which is reading lambda in the correct range.
After narrowing it down to the wb02.
Turns out my VEMS ECU was earmarked for an LSU 4.2 wideband, but a lot of units were being done at that time in May 2019 and to make a long story short an LSU 4.9
WB02 was shipped with that setup, but the necessary 27K pull up resistor was never installed so the unit was only pushing out 3.7V Nernst to the wb02 (Fine for LSU4.2) and it needs over 4V to function properly for a 4.9. So I soldered in a 27K resistor in series on a wire and soldered one end to Nernst which is pin 13 on the EC18 and pin 28 on the EC28(+5V). I did this on the OUTSIDE of the VEMS unit. Used liquid electric tape to seal since it's now a T connection and it worked well.
Now I am getting 4.5V to the LSU4.9 WB02 which is reading lambda in the correct range.
09-25-2019, 03:40 PM
#522
Rennlist Member
09-25-2019, 05:41 PM
#524
Rennlist Member
09-26-2019, 11:40 PM
#525
Three Wheelin'
Speaking of configs... I am having an issue trying to start my car. When I open VEMS it says it is in 'safe mode' and won't start. I realize I am supposed to upload a config to get it out of 'safe mode', but when I try it, nothing changes. I'm stumped. Any help?